NZSP40
NEW ZEALAND SOCIETY FOR PARASITOLOGY
ANNUAL MEETING No. 40
24-25 OCTOBER 2012
MARLBOROUGH CONFERENCE CENTRE
BLENHEIM
Conference Proceedings & Abstracts
The Society would like to thank the following
sponsors for their generous support
AgResearch Limited
Ancare Scientific
Gribbles Veterinary
Merial Ancare New Zealand Limited
MSD Animal Health
Novartis Animal Health Limited
New Zealand Veterinary Pathology
PGG Wrightsons Limited
Pfizer New Zealand Limited
Ravensdown
2
Programme
Tuesday 23 October
@ Convention Centre
6.30pm – 8.00pm - Registration and Welcome
6.45pm – 8pm “Taste Marlborough”
Wednesday 24 October
8.30am – 9.00am - Registration
Conference Opening – 9.00am
Colin McKay - President
Robin McAnulty – Housekeeping matters
Session 1 – Some Interesting Papers to Get the Conference Going
9.15 am - 10.30pm
Chair: Paul Mason
9.15am
A case study of Anthelmintic Reversion in sheep internal parasites (nematodes) after
12 years of continuous Triple active combination use. Can drenching be sustainable?
Mark Vickers, Gary Harrison, Mitch Venning and David Chandler
9.30am
Efficacy of oral, injectable and pour-on formulations of moxidectin against
gastrointestinal nematodes in cattle in New Zealand.
TS Waghorn presenting on behalf of DM Leathwick & CM Miller
9.45am
Outline of the management options taken on a production orientated South Island
deer farm with known anthelmintic resistance and high internal parasite challenge.
Ian Page
10.00am
Anthelmintic resistance to moxidectin and abamectin in red deer after 20 years of
moxidectin pour-on use.
Colin Mackintosh, Chris Cowie, Peter Johnstone, Paul Mason
10.15am
Gastrointestinal (GI) nematode infection and diagnostic indicators in dairy cows.
Dhrubajit Saikia, Robin McFarlane, Andrew Greer, Robin McAnulty
10.30am -11.00am
MORNING TEA/COFFEE
3
Session 2 – Invited Papers & Related
11.00am - 12.30pm
Chair: Tania Waghorn
11.00am
WormBoss: Australia’s sheep worm control resource
Lewis Kahn, Deborah Maxwell, Stephen Love, Maxine Lyndal-Murphy, Arthur Le Feuvre,
Brown Besier
11.30am
Wormwise, an update.
Presented by Peter Anderson
11.45am
Voluntary intake of an anthelmintic by grazing sheep.
Lewis Kahn, Fiona Fishpool
12.05pm
A production based targeted selective anthelmintic treatment regime for grazing dairy
calves.
Robin W. McAnulty, A. W. Greer and S.J. Gibbs
12.25pm
Conference Photo, weather permitting – otherwise at another convenient time.
12.30pm
- 1:30pm
LUNCH
4
Session 3 – Mainly Marine
1.30pm – 3.00pm
Chair: Robert Poulin
1.30pm
How will ocean acidification affect the free-living stages of marine parasites.
Colin D MacLeod
1.45pm
Cryptic diversity in widely distributed amphipods: do parasites care?
Clément Lagrue & Loïc Bollache
2.00pm
An atypical genotype of Toxoplasma gondii as a cause of mortality in Hector's
dolphins (Cephalorhynchus hectori).
WD Roe, L Howe, EJ Baker, L Burrows, SA Hunter
2.15pm
Reproduction and caste ratios under stress in trematode colonies with a division of
labour
Melanie Lloyd and Robert Poulin
2.30pm
Cast ratios and behavioural plasticity in social trematodes.
Tsukushi Kamiya
2.45pm
Numerical and functional responses of intestinal helminths in three elasmobranch
fishes: evidence for competition between parasites?
Haseeb S Randhawa
3.00pm – 3.30pm
AFTERNOON TEA/ COFFEE
5
Session 4 – General Papers
3.30pm – 4.30pm
Chair: Bill Pomroy
3.30pm
Benefits and limitations of various diagnostic tools for the detection of Neospora
caninum infection in sheep flocks.
L Howe, SS Syed-Hussain, WE Pomroy
3.45pm
Vineyard grazing – a good example of the dangers of a low refugia system.
Peter V A Anderson
4.00pm
The distribution of Nematodirus spathiger and N. filicollis in New Zealand.
Oliver A-M., Leathwick D. and Pomroy W.
4.15pm
Potential ivermectin-resistance in equine nematodes.
[an Scott, Rebecca Bishop, Erica Gee, Chris Rogers, Joe Mayhew, Bill Pomroy
4.30pm
Annual General Meeting
6.30pm
Drinks followed by Conference Dinner
CONFERENCE DINNER
Drinks 6.30-7.15pm, then bus to
Wither Hills Winery
for dinner at 7.30
6
New Zealand Society for Parasitology
and 41st Annual General Meeting
Marlborough Convention Centre
24 October 2012
AGENDA
1.
Attendees
2.
Apologies
3.
Minutes of the 40th AGM
4.
Matters arising from these Minutes
5.
Correspondence
a.
Inwards
b.
Outwards
6.
President’s Report
7.
Treasurer’s Report
8.
Election of Officers
9.
Honorary members
10. Conference 2013
11. General Business
WFP – membership fees, ICOPA levy, Conference Organiser
7
Thursday 25 October
Session 1 – General Papers
9.00 am - 10.30pm
Chair: Dave Cole
9.00am
The implications for New Zealand of potentially invasive ticks sympatric with
Haemaphysalis longicornis.
Allen Heath
9.15am
Modelling the effect of temperature on the development and survival of Cooperia
oncophora third stage larvae
C.W. Sauermann, D.M. Leathwick, W.E. Pomroy, I. Scott
9.35am
Targeted use of bioactive forages as a curative treatment for organic lambs
Robin W. McAnulty and A. W. Greer
9.50am
Evaluating a molecular test for BZ resistance in field populations of Teladorsagia
circumcincta and Trichostrongylus colubriformis
JS Knight, TS Waghorn, SA Bisset and DM Leathwick
10.10am
A study of parasitism in 12 horses over a 14 month period.
Ian Scott, Bill Pomroy
10.30am -11.00am
MORNING TEA/ COFFEE
8
Session 2 – General Papers
11.00am - 12.30pm
Chair: Colin McKay
11.00am
Migration as an escape from parasitism in New Zealand galaxiid fishes
Robert Poulin, G. Closs, A. Lill, A. Hicks, K. Herrmann, D. Kelly
11.20am
Prevalence of periwinkle parasites.
Katie O'Dwyer & Robert Poulin
11.40am
High Prevalence of Leucocytozoon sp. in the Endangered Yellow-eyed Penguins
(Megadyptes antipodes) residing in the Sub-Antarctic Regions of New Zealand.
L.S. Argilla, L. Howe, B.D. Gartrell, and M.R. Alley.
12.00pm
Immunological competence of calves.
David Heath, Christine Robinson and Marshall Lightowlers
12.30pm
- 1:30pm
LUNCH
Session 3 – General Papers
1.30pm – 3.00pm
Chair: Paul Mason
1.30pm
Nitrogen metabolism in Haemonchus contortus and Teladorsagia circumcincta.
Saleh Umair, Ross Bland & Heather Simpson
1.45pm
CarLA and the immune response: how a worm glyco-lipid impacts on immune cell
function.
Joanna Roberts
2.00pm
Investigations into suspected ivermectin-resistant Ostertagia.
Ian Scott, Bill Pomroy
2.15pm
Conference finishes about this time
3.00pm – 3.30pm
AFTERNOON TEA/COFFEE
9
Abstracts
1
A case study of Anthelmintic Reversion in sheep internal parasites (nematodes) after
12 years of continuous Triple active combination use. Can drenching be sustainable?
Mark Vickers, Gary Harrison, Mitch Venning and David Chandler
26 A Buchanan Road, RD 1, Papakura 2580
Launched in controversy in 2001, the world’s first commercially available triple roundworm
active drench formulation “Triton” containing a member of each of all three broad spectrum
anthelmintic drench families was marketed in New Zealand.
Data is presented from a North Auckland farm with severe clinical anthelmintic drench
resistance that had used this triple drench prior to commercial launch. This farm has used a
Triton-like drench almost continuously and exclusively since 2000. The faecal egg count
reductions in May/Aug
2000 were ivermectin (33-79%), levamisole (22-33%) and
albendazole (56-65%) , Triton (>99%), in Dec 05/Jan 06 they were ivermectin (94-95%),
levamisole (94-99.5%), albendazole (91-99%), Triton (>99%); and in Aug 2012 were
ivermectin( >99%), albendazole (>99%) levamisole (>98.0%), Triton or Matrix (>99%). Initial
worm counts (2000) showed an ML+Bz resistant Haemonchus contortus, a triple resistant
Teladorsagia circumcincta and a dual Bz+Lev resistant Trichostrongylus colubriformis
2
Efficacy of oral, injectable and pour-on formulations of moxidectin against
gastrointestinal nematodes in cattle in New Zealand.
TS Waghorn presenting on behalf of DM Leathwick & CM Miller
Grasslands Research Centre, Private Bag 11008, Palmerston North 4442
The efficacy of moxidectin administered by different routes, against naturally acquired
infections of gastrointestinal nematode parasites of cattle, was compared using faecal egg
count reduction tests on 14 commercial farms throughout New Zealand. On each farm,
groups of 15 calves were sampled for faecal nematode egg count and then treated with
ivermectin administered orally, or with moxidectin administered either by the oral,
subcutaneous injection or topical (pour-on) route. Samples were again collected 14 days
after treatment and efficacy was calculated as the percentage reduction in group mean egg
count between the pre- and post-treatment samples. In addition, efficacy was calculated for
individual animals, in order to compare the variability of the different treatments. On four
farms untreated control groups were run and five animals from each of the control and all of
the moxidectin-treated groups were bled over time to estimate plasma-moxidectin
concentrations.
Averaged across all tests, the reduction in faecal egg count was significantly greater after
treatment with moxidectin oral (91.1%) than following treatment with moxidectin injection
10
(55.5%) or with moxidectin pour-on (51.3%). Low efficacies were invariably against
Cooperia oncophora. The oral treatments were significantly less variable in efficacy than
the injection and pour-on treatments. Moxidectin concentrations in plasma were highest
following subcutaneous injection and lowest following pour-on administration. Plasma
levels following oral administration were intermediate, being significantly lower than postinjection and significantly higher than post-pour-on. There was no evidence of transfer of
moxidectin to untreated animals through licking. Based on these results, along with those of
other studies, it is proposed that oral administration of macrocyclic lactone anthelmintics
results in higher concentrations of active reaching the target worms in the gastrointestinal
tract than following either administration by injection or by pour-on.
3
Outline of the management options taken on a production orientated South Island
deer farm with known anthelmintic resistance and high internal parasite challenge.
Ian Page
North Canterbury Veterinary Clinics Ltd, Cheviot
Since March 2010 I have been involved with the Stone Jug farm, Inland Road, Kaikoura as
the veterinarian consulted on animal health issues on the farm. The farm itself is primarily a
commercial deer farm breeding up to 2000 R1yr deer for venison production. From early in
my involvement the farm history and some early testing showed resistance to ML-type
anthelmintics including moxidectin pour-on and doramectin injection. At this time all deer on
the farm where being given some form of anthelmintic treatment to prevent deaths. Over the
following 2 year period the farmer and I have worked together to reduce the use of
anthelmintics, ensure the most effective anthelmintics available are used when required and
changed farm management policies to reduce the parasite challenge. This has been
achieved while maintaining high production output but may not be sustainable in the long
term. This presentation is to discuss the limited options available on this farm as an
example of what may be happening on large scale deer operations.
4
Anthelmintic Resistance to Moxidectin and Abamectin in red deer after 20 years of
moxidectin Pour-on Use.
Colin Mackintosh, Chris Cowie, Peter Johnstone, Paul Mason
AgResearch Invermay, PO Box 50034, Mosgiel, 9053
Moxidectin Pour-on has been used exclusively on a deer farm for the last 20 years. There
have been suspicions that anthelmintic resistance was developing recently.
A slaughter study was undertaken in 5 month old red deer weaners and included two
anthelmintics and three routes of administration (Pour-on, oral and injection) of moxidectin
(Cydectin) and abamectin (Genesis); ie 6 treatment groups and an untreated Control group,
with 6 weaners per group. The deer were killed 14 days after treatment. A faecal egg count
reduction test (FECRT) was also conducted in parallel.
11
Control deer averaged 1108 Ostertagia-type spp.
Moxidectin efficacy; injection 79%, oral 31% and pour-on 27%.
Abamectin efficacy; injection 76%, oral 72% and pour-on 33%.
Control deer averaged 2489 adult Dictyocaulus sp. lungworm. Efficacy was 100% for all
treatments except abamectin injection (96%), but only one animal (#433) had 640
lungworms, and may have not have received its full anthelmintic dose.
There were nil or negligible numbers of Haemonchus, Trichostrongylus, Nematodirus and
Cooperia spp. in the abomasum and small intestine. Control deer averaged 55
Oesophagostomum venulosum in the large intestine and the efficacy was 100% for all
treatments except for abamectin injection (61%), but only #433 had O. venulosum (130).
At slaughter there was a good correlation between FEC and Ostertagia-type nematodes in
the untreated Controls, but hardly any eggs were found in faeces from treated animals at 7
and 14 days post treatment despite significant worm burdens, showing egg-laying
suppression in resistant nematodes.
These results show significant anthelmintic resistance against moxidectin and abamectin is
present on this deer farm. The injectible is significantly more effective than the oral or pouron forms of both anthelmintics.
FECRT is unreliable in deer when anthelmintic resistance is present.
5
Gastrointestinal (GI) nematode infection and diagnostic indicators in dairy cows.
Dhrubajit Saikia, Robin McFarlane, Andrew Greer, Robin McAnulty
Faculty of Agriculture and life Sciences, Lincoln University, Canterbury, New Zealand
There is a need to identify only those animals with parasite burdens that are likely to benefit
from anthelmintic treatment in order to minimise the development of drug resistance in
nematodes. Although evidence from Europe and North America suggests that antibody
levels to GI nematode infection are inversely linked to production in adult dairy cattle
(Charlier et al., 2009 and Sanchez et al., 2004), no such link has been shown, to date, in
New Zealand.
The objectives of this study were to seek associations between serum or milk antibody
levels to GI nematodes and infective larvae availability on pasture, adult parasite burdens
and faecal egg count (FEC) expressed as egg per gram (EPG).
A group of lactating dairy cows at high stocking density and fed supplements were
compared with a low stocking density group (n=30), by monthly monitoring for milk yield,
pasture L3 larvae, FEC, milk and serum antibody levels to gastrointestinal (GI) nematodes.
Mean EPG was low in both the groups, neither mean EPG nor the proportion of cows
showing positive FEC were influenced by stocking density over the whole lactation season.
Further, FEC in either group did not correlate with milk yield (production). Immunological
analysis has not yet been completed.
12
6
WormBoss: Australia’s sheep worm control resource
Lewis Kahn, Deborah Maxwell, Stephen Love, Maxine Lyndal-Murphy, Arthur Le Feuvre,
Brown Besier
Animal science (W49), School of Environmental and Rural Science,
University of New England, Armidale NSW 2351, Australia
WormBoss was originally launched by the Australian Sheep Industry CRC in March 2005,
principally to provide an on-line national information source to help livestock producers
better control the major and occasional internal parasites of sheep (i.e. roundworms, flukes,
tapeworms and coccidia). The site has been well used by industry with a monthly average
of 6,000 different users. WormBoss has been redeveloped during 2012 to provide greater
emphasis on assisting sheep producers to address specific parasite problems. The
updated WormBoss has three important new elements: Australia-wide, region-specific worm
control programs, online Drench Decision Guides and an improved database to help with
drench selection. The WormBoss team includes representatives from the Sheep Industry
CRC and state departments of primary industry. There was wide-spread consultation with
industry professionals and the opportunity to draw on new research to develop Drench
Decision Guides and update and further develop existing control programs to become
WormBoss programs. The philosophy of WormBoss is to provide a demand-driven (as
opposed to supply-driven) approach to learning so that the likely hierarchy of use is (i)
Drench Decision Guides to help solve current internal parasite problems; (ii) the Drench
Database to help select an effective product; (iii) Regional worm control programs to
establish an on-going plan for prevention, detection and response; and finally (iv) site
information to better understand the ecology and financial cost of internal parasites, host
resistance and drench resistance. WormBoss training has been developed to extend
regional worm control programs to livestock producers and animal health specialists trained
in delivery. Professional development is also being developed for agribusiness staff
involved in providing animal health advice. WormBoss will eventually form part of the
Australian ParaBoss initiative that will see blowfly (FlyBoss) and lice (LiceBoss) added to a
national program that will include technical advisory panels.
7
Wormwise, an update.
Presented by Peter Anderson
No abstract when Proceedings went to print.
13
8
Voluntary intake of an anthelmintic by grazing sheep.
Lewis Kahn, Fiona Fishpool
Animal science (W49), School of Environmental and Rural Science,
University of New England, Armidale NSW 2351
Control programs for roundworms of sheep must satisfy the apparently competing interests
of efficacy and minimising selection for anthelmintic resistance. One strategy to achieve
both interests is to administer anthelmintics to grazing livestock in a manner that targets the
least resistant and resilient animals. This approach, known as targeted selective treatment,
leaves a proportion of animals untreated whose resident roundworms are likely to reduce
selection pressure for anthelmintic resistance. Targeted selective treatment strategies
typically require data collection followed by analytical interpretation to decide which animals
will be treated. We investigated if sheep were able to display behaviours that directed
freely-available anthelmintic to those carrying roundworm infections. Specifically we tested
the notion that infection with sensitive strains of Trichostrongylus colubriformis and
Haemonchus contortus would alter the consumption by sheep of a medicated feed block
(MFB; containing 1.5 mg/g fenbendazole). The underlying hypothesis for this work was that
the pathophysiology of roundworm infection coupled with positive post-ingestive
consequences of curative treatment, from consuming the MFB, would provide the stimulus
for MFB consumption by grazing Merino wethers. Plasma concentrations of fenbendazole
metabolites were used to estimate individual MFB intake as these have been demonstrated
to be proportional to fenbendazole intake. More infected wethers (95%) consumed the MFB
than did uninfected wethers (79%) (P < 0.001) and infected wethers ate significantly more
MFB over the first four days (P = 0.041) of access (30 and 22 g/d respectively). All infected
wethers consumed sufficient MFB to receive a therapeutic dose of fenbendazole and worm
egg counts declined from 2165 epg to 120 epg in the first week of access to MFB.
Differences in MFB intake between infected and uninfected wethers diminished as worm
egg count declined. The pattern of consumption of MFB was altered by roundworm
infection in a way that encourages the concept of self-medication as a targeted selective
treatment strategy.
9
A production based targeted selective anthelmintic treatment regime for grazing dairy
calves.
Robin W. McAnulty, A. W. Greer and S.J. Gibbs
Faculty of Agriculture and Life Sciences, PO box 84 Lincoln University,
Lincoln 7647
Recent studies have highlighted the risk of anthelmintic resistance in dairy heifer calves due
to use of neo suppressive drenching regimes. For these systems, effective parasite control
and reduced anthelmintic usage can be achieved through targeted selective treatment
(TST) anthelmintic regimes. However, recent investigations in sheep and cattle suggest that
FEC is a poor indicator of which individuals are likely to benefit from treatment. This
investigation sought to determine if a production based TST was an effective targeted
selective treatment option for dairy calves over time and across a variety of farms.
Studies over three years, across a number of farms evaluated the performance of various
groups of Friesian and Friesian x Jersey calves (n=100+) in two different grazing systems.
14
In system 1 calves were grazed in front of the main milking herd whereas in system 2 where
calves were sent for grazing off farm. Within each grazing system calves were allocated
into two groups (n-=50) with one group treated on a monthly basis , a neo suppressive
treatment, (NST) and the second group were treated on individual basis by their failure to
reach a production target (TST). Calves were monitored at monthly intervals for Individual
FEC and live weights (LW) from around 4 months of age until 10 months of age.
Results from year 3 confirm initial trial findings with substantial reductions (p=0.001) in
drench usage in TST treated groups, ranging from 57% to 73 %. As LWG targets increased
over the three years the number of TST animals needing treatment also increased. In year
3, on three of the four farms there was no significant difference seen between LWG of NST
and TST calves. This supports earlier findings which suggested that as you approach a
50% treatment frequency, difference in LWG between NST and TST groups were
eliminated. The adoption of a production based TST appears to reduce drench usage
without compromising calf production and would tie in nicely with industry recommendations
to frequently monitor calf liveweights during their first grazing season.
10
How will ocean acidification affect the free-living stages of marine parasites.
Colin D MacLeod
340 Great King Street, Dunedin, 9054
The increasing concentration of carbon dioxide in the atmosphere, caused by anthropogenic
activity such as fossil fuel combustion, is commonly associated with the release of
greenhouse gasses and consequent global warming. However, as the atmosphere and the
oceans are in a state of equilibrium, anthropogenic activity is also increasing the
concentration of CO2 in seawater. As one of the most significant changes to seawater
chemistry caused by elevated CO2 is a reduction of pH, this phenomenon has become
known as ocean acidification (OA).
In the past 10 years, it had been established that OA could have significant and negative
effects on a wide variety of marine species, although the overall ecosystem level impact will
likely be unpredictable. However, to date, the effect of OA on parasites as individual species
and important components of marine systems has been almost completely overlooked.
In order to address this knowledge gap, it is necessary to initially examine the effects of
reduced pH on the various life stages of individual parasite species. This presentation
discusses the effects of reduced pH on the cercarial larvae of marine trematode parasites
as they emerge from their first intermediate host and enter the free living stage of their life
cycle. It has been suggested that free living stages, such as cercariae, are the most
vulnerable step in the parasitic life cycle to novel abiotic stressors. Any OA mediated
change to the activity, survival, and, ultimately, transmission success of an individual
parasite species could have broad implications for disease prevalence. Evidence of
differential tolerances to acidified conditions between coexisting parasite species could also
provide important evidence that OA has the potential to shift the composition of host
communities, especially in the case of parasites that reduce fecundity or increase mortality.
15
11
Cryptic diversity in widely distributed amphipods: do parasites care?
Clément Lagrue & Loïc Bollache
Department of Zoology, University of Otago, 340 Great King Street, PO Box 56
Dunedin 9054
Generally, diversity is estimated as the number of species present at any one time in an
ecosystem. However, identifying species using morphological characters is not always
reliable and genetic techniques have recently exposed variable and sometimes high levels
of cryptic diversity in the European amphipods Gammarus pulex, G. fossarum and G.
roeseli. Here we simultaneously analyzed natural cryptic diversity in these amphipods and
tested its possible implications for the infection dynamics of acanthocephalan parasites.
Results show that co-occurring amphipod cryptic lineages may have highly different, and
species-specific, vulnerabilities to different acanthocephalan parasites. In some cases, both
parasite prevalence and abundance were found to differ by an order of magnitude between
amphipod lineages living in the same environment and that would be morphologically
classified as a single taxonomic unit.
Differential parasitism among morphologically cryptic hosts may affect the relative success
of sympatric genetic lineages in wild amphipod communities, eventually driving speciation. It
also has serious implications for the study of host-parasite interactions, parasite virulence or
host resistance.
12
An atypical genotype of Toxoplasma gondii as a cause of mortality in Hector's
dolphins (Cephalorhynchus hectori).
WD Roe, L Howe, EJ Baker, L Burrows, SA Hunter
Tennent Drive, Massey University, Private Bag 11-222, Palmerston North
Hector’s dolphins (Cephalorhynchus hectori) are a small endangered coastal species that
are endemic to New Zealand. Anthropogenic factors, particularly accidental capture in
fishing nets, are believed to be the biggest threat to survival of this species. The role of
infectious disease as a cause of mortality has not previously been well investigated.
The importance of protozoal disease in marine mammal species has become increasing
apparent over the past decade. Recently, protozoan encephalitis caused predominantly by
Toxoplasma gondii was identified as a major cause of mortality in the southern sea otter.
Sporadic cases of fatal toxoplasma infections have also been reported in several cetacean
and pinniped species.
This study investigates Toxoplasma gondii infection in Hector’s dolphins, finding that 7 of 28
(25%) dolphins examined died due to disseminated toxoplasmosis, including 2 of 3 Maui’s
dolphins, a critically endangered sub-species. A further 10 dolphins had one or more tissues
that were positive for the presence of Toxoplasma gondii DNA using PCR. Genotyping
revealed that 7 of 8 successfully amplified isolates were an atypical Type II genotype. Fatal
cases had necrotising and haemorrhagic lesions in the lung (n = 7), lymph nodes (n = 6),
16
liver (n = 4) and adrenals (n = 3). Tachyzoites and tissue cysts were present in other organs
including the brain (n=5), heart (n = 1), stomach (n = 1) and uterus (n = 1) with minimal
associated inflammatory response. One dolphin had a marked suppurative metritis in the
presence of numerous intra-epithelial tachyzoites. No dolphins had underlying morbillivirus
infection.
This study provides the first evidence that infectious agents could be important in the
population decline of this species, and highlights the need for further research into the route
of entry of Toxoplamsa gondii organisms into the marine environment worldwide.
13
Reproduction and caste ratios under stress in trematode colonies with a division of
labour
Melanie Lloyd and Robert Poulin
340 Great King Street Dunedin 9016
Parasitic trematodes in their first intermediate host form colonies of clonal individuals. These
individuals are, depending on the species, rediae or sporocysts (which continue to asexually
reproduce) or cercariae (which develop within the rediae or sporocysts and leave the snail
to infect the next host). Some trematode species use a division of labour within the colonies,
in which there exist two distinct redial morphs: small rediae (non-reproducing individuals
which appear morphologically specialized for defense against co-infecting trematodes), and
large rediae (asexually reproducing individuals which expand the colony while also
producing cercariae). In the social insect literature, the theory of optimal caste ratio predicts
that the relative amount of caste members (small rediae to large rediae) should respond to
environmental variability. Here, we tested this response experimentally in Philophthalmus
sp. colonies exposed to environmental stress (host starvation and competition with a
common co-infecting trematode, Maritrema novaezealandensis). Philophthalmus sp.
infected snails, with and without co-infection by M. novaezealandensis, were subjected to
various food treatments over a ten week period. Reproductive output (measured as
released cercariae), total number of rediae, and the ratio of small to large rediae were
compared among treatments. Philophthalmus sp. colonies responded to stress by host
starvation and competition; reproductive output was significantly higher in (a) well fed snails
of both infection types compared to snails in lower food treatments and (b) well fed, single
infected snails compared to well fed double infected snails. Furthermore, Philophthalmus
sp. colonies altered the caste ratio of small to large rediae in response to competition. This
is the first study that shows caste ratio responds to environmental pressures in trematodes
with a division of labour.
17
14
Cast ratios and behavioural plasticity in social trematodes.
Tsukushi Kamiya
Department of Zoology, University of Otago, P.O. Box 56, Dunedin 9054
The optimal caste allocation theory predicts that specialised morphological castes are
efficient at specific tasks, and hence different caste ratios should affect the ergonomic
efficiency, hence reproductive output of the colony. Here I present findings of a study
investigating whether the ratios of non-reproductive and reproductive morphs affect the
reproductive output of a recently discovered social trematode, Philophthalmus sp., in which
the non-reproductive members are hypothesized to be defensive specialists. Census of
natural infections and a manipulative in-vitro experiment demonstrated a positive
association between the reproductive output of trematode colonies and the ratio of nonreproductive to reproductive morphs in the presence of an intra-host trematode competitor,
Maritrema novaezealandensis. On the contrary, without the competitor, reproductive output
was negatively associated with the proportion of non-reproductive members. My findings
demonstrate a clear fitness benefit associated with the non-reproductive castes in the
presence of a competitor while illustrating the cost of maintaining such morphs in noncompetitive situations. I explored further to elucidate mechanisms through which colony
fitness of Philophthalmus sp. changes in relation to the competitor. One of my hypotheses is
socially-mediated behavioural plasticity where members adjust their behaviours according
to social context, allowing colonies to sustain efficiency of the whole without the cost of
additional production of individuals or delayed responses to perturbations. Using in-vitro
experiments, I demonstrated that members of the reproductive caste adjust their defensive
behaviour according to the local availability of non-reproductive defensive specialists, and
this plasticity was associated with differential reproductive output at the individual level. My
findings support the prediction that the fitness of colonies is influenced by the composition of
specialized functional morphs in social trematodes and present behavioural plasticity as a
potential mechanism responsible for the observed differential fitness.
15
Numerical and functional responses of intestinal helminths in three elasmobranch
fishes: evidence for competition between parasites?
Haseeb S Randhawa
Ecology Degree Programme, Dept Botany, University of Otago, P.O. Box 56, Dunedin, 9054
Host-parasite interactions generally involve communities of parasites. Within these
communities, species will coexist and/or interact with one another in a manner either
benefiting the species involved or to the detriment of one or more of the species. At the
level of helminth infracommunities, evidence for intra- and inter-specific competition
includes numerical responses, i.e. those regulating helminth intensity of infection, and
functional responses, i.e. where the presence of competitors modifies the realised niche of
infrapopulations. The objectives of this study are to assess the numerical and functional
responses of helminths in infracommunities from three rajid skates using general linear
models. Despite a lack of numerical responses, functional responses to intra- and inter-
18
specific interactions were observed. A positive correlation between the number of
individuals in an infrapopulation and its niche breadth (functional response) was observed
for the tapeworms Pseudanthobothrium spp. and Echeneibothrium spp., in all their
respective hosts, and for the nematode Pseudanisakis sp. in the little skate. Evidence for
inter-specific competition includes niche shifts in Pseudanthobothrium purtoni (ex little
skate) and Pseudanisakis sp. (ex thorny skate) in the presence of Pseudanisakis sp. and
the tapeworm Grillotia sp., respectively. These results are consistent with other studies in
providing evidence for competition between helminths of skates.
16
Benefits and limitations of various diagnostic tools for the detection of Neospora
caninum infection in sheep flocks.
L Howe, SS Syed-Hussain, WE Pomroy
Tennent Drive, Massey University, Private Bag 11-222, Palmerston North
Naturally occurring ovine neosporosis has been reported worldwide. However, the role of
N. caninum as a significant pathogen and abortifacient agent in sheep is still unclear.
Recent studies have suggested that the current diagnostic methods may underestimate or
overestimate the prevalence of N. caninum in sheep flocks depending on the diagnostic
method used.
Historically, IFAT has been considered sensitive and specific for serological diagnosis in
sheep and cattle. However, recent studies have found inconsistencies with concordance
between IFAT and various ELISA methods. Although serology is a useful tool, limitations
include rapid fluctuations in humoral response to N. caninum infection and positive serology
only provides evidence of exposure not a definitive diagnosis. In addition, the effect of
congenital infection and/or mode of transplacental transmission need to be considered on
the development of antibody levels. ELISA avidity assays may provide an additional tool for
the identification of acute or chronic infections in association with abortion events and help
determine the timing of infection. For example, low-avidity IgG response suggests the
occurrence of a recent infection in a herd or flock. However, as with most assays, avidity
ELISAs must be standardised between laboratories and their performance monitored.
Several studies have used PCR or quantitative PCR (qPCR) for the detection of Neospora
DNA in aborted tissue, semen, and ewe blood, particularly for ewes experiencing
unexplained abortions. Molecular tools are extremely sensitive; however, studies have
shown that Neospora DNA disappears from the circulation soon after an abortion has
occurred. Therefore, aborting ewes may have a higher prevalence of parasite DNA during
early pregnancy prior to expulsion of the foetus.
Thus, a combination of serological, histopathology and molecular methods should be used
to investigate naturally-occurring abortions in sheep to help determine reliable testing
methods and elucidate the true role of Neospora caninum in poor reproductive performance.
19
17
Vineyard grazing – a good example of the dangers of a low refugia system.
Peter V A Anderson
The Vet Centre (Marlborough), 7 Redwood St, BLENHEIM
Vineyard grazing is a common practice in the grape growing areas of Marlborough. These
vineyards often contain high quality legume and herb based pastures and the benefits of
grazing them from after grape harvest in the autumn until bud burst in the spring with
minimum parasite challenge are significant. However because we had confirmed significant
anthelmintic resistance on some properties that carried out this practice we were concerned
that vineyard grazing might, because of them being low refugia systems, mean that sheep
when they returned home could be easily responsible for introducing anthelmintic resistant
parasite populations. This FITT funded study involved firstly determining the anthelmintic
resistance status of a Merino high country property. Then while half the replacement
hoggets were retained at home the other half were trucked to a vineyard that had been used
by the property in the winter of previous years. Both groups were drenched with the
anthelmintic to which there was some resistance (Levamisole) the day the hoggets left for
the vineyard. While the vineyard group did not require treating at any stage during their stay
the hoggets remaining on the station did require a mid-winter Levamisole drench. On the
return to the station both hogget groups underwent another FECRT. While there was no
evidence of deteriorating resistance to Levamisole on the main property, the vineyard group
were found to be carrying parasites resistant to both Albendazole and Ivermectin but not
Levamisole. Reasons for these findings are discussed.
18
The distribution of Nematodirus spathiger and N. filicollis in New Zealand.
Oliver A-M., Leathwick D. and Pomroy W.
Parasitology, AgResearch Grasslands, Tennent Drive, Private Bag 11008, Palmerston
North 4442
The main Nematodirus species infecting New Zealand sheep are N. spathiger and N.
filicollis. The distribution of these two species in two contrasting regions of the country was
studied by means of a presence/absence survey.
Faecal samples were collected from lambs under 6 months of age from 20 farms in the
southern North Island and 29 farms in the southern South Island. All samples were
incubated at 20°C for at least 28 days to allow larval development. Samples were then split
with one portion being baermannised and the other chilled at 4°C for varying intervals.
Following baermannisation of the second portion, the resulting third stage larvae were
identified to species by PCR methods.
The preliminary results show that N. spathiger and N. filicollis are prevalent in both regions.
Further, samples incubated without chilling were dominated by N. spathiger. N. filicollis was
only found in significant numbers after chilling, suggesting that this species normally
requires chilling before eggs will hatch.
20
19
Potential ivermectin-resistance in equine nematodes.
Ian Scott, Rebecca Bishop, Erica Gee, Chris Rogers, Joe Mayhew, Bill Pomroy
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
To investigate suggestions that Parascaris equorum, an important parasite of young horses,
had become resistant to ivermectin, egg count reduction tests were carried out in young
foals on 3 commercial thoroughbred stud farms. A total of 39 foals were treated with oral
ivermectin paste and egg counts monitored for 14 or 21 days post-treatment. Some of the
foals were later treated with an ivermectin or a moxidectin and benzimidazole/praziquantel
combination. On two of the farms, counts of P. equorum eggs continued to rise for 21 days
after ivermectin, but then declined by 94% after ivermectin/fenbendazole/praziquantel and
100% after moxidectin/oxfendazole/praziquantel. On the third farm, P. equorum egg counts
were reduced by < 70%, 14 days after treatment. The foals on this latter farm were the only
ones shedding strongylid eggs in any number before treatment, and counts of these were
only reduced by 85%. When originally released, ivermectin had 100% efficacy against egglaying P. equorum. The exact efficacies of the treatments in this study could not be
calculated, however, the results strongly suggest the presence of ivermectin-resistance in
this parasite on all 3 farms. The results also indicate reduced efficacy against the strongylid
nematodes (most likely cyathostomes) of the foals on at least one property.
20
The implications for New Zealand of potentially invasive ticks sympatric with
Haemaphysalis longicornis.
Allen Heath
AgResearch, National Centre for Biosecurity and Infectious Disease, Wallaceville, PO Box
40063, Upper Hutt 5140, New Zealand
Haemaphysalis longicornis Neumann, a broadly western Pacific species, is the only
economically important ixodid tick that has successfully invaded New Zealand.
The premise of this talk is that other tick species sympatric with H. longicornis elsewhere in
the world pose a risk to New Zealand as potential invaders because they share bioclimatic
and host preferences with H. longicornis. In all, 17 species of Ixodidae and one species of
Argasidae, principally from Japan, China and Australia, most closely match the
bioecological characteristics of H. longicornis. Humans and their baggage should be
considered an important vehicle of entry in addition to companion animals.
Sympatry and shared biological preferences are not necessarily indicative of potential
invasiveness, but serve as indicators of the need for heightened surveillance.
21
21
Modelling the effect of temperature on the development and survival of Cooperia
oncophora third stage larvae
C.W. Sauermann, D.M. Leathwick, W.E. Pomroy, I. Scott
Institute of Veterinary, Animal & Biomedical Sciences, College of Sciences,
Massey University, Private Bag 11-222, Palmerston North
Aim
To develop a model of the effect of ambient temperature on the development and survival of
the free-living stages of Cooperia oncophora.
Methods
Parameters were calculated from experimental data with C. oncophora third stage larvae
under constant temperatures and these were used to build models using the boxcar train
technique. Results from the model were compared to data from larvae experiments under
varying temperatures in the laboratory and in the field. Model predictions on larval
development and survival for ten years of temperature data were calculated.
Results
Model calculations show a good correlation with the experiments with varying temperatures
in the laboratory, whereas results gathered in field experiments are significantly lower than
those predicted.
Conclusion
The model provides a framework to develop a better understanding of the development and
survival of C. oncophora on pasture.
22
Targeted use of bioactive forages as a curative treatment for organic lambs
Robin W. McAnulty and A. W. Greer
Faculty of Agriculture and Life Sciences, PO Box 84 Lincoln University,
Lincoln 7647
This project was run on the organic land at the Lincoln biological Husbandry Unit (LBHU) to
provide the necessary information needed to develop practical, cost effective programmes
for nematode worm control in lambs grazing in organic systems. The ability to identify and
then remove individual animals suffering from parasitism and subsequently graze them on
bioactive forages (chicory, plantain) should provide a chemical free method of reducing the
impact of parasitism.
Trial area consisted of a 4 ha block that was split into two blocks (2 ha). Each block had 1.5
ha sown in ryegrass (AR1) and 0.5 ha in a mixed sward lay of chicory/plantain and white
cover. 60 weaned lambs were allocated on liveweight to one of two block (n=30), and were
rotational grazed across each block on the ryegrass sward, from November 2011. One
block had been seeded with Teladorsagia circumcincta eggs and the second block had
been seeded with Trichostronglyus colubriformis eggs. Animals were monitored at two
weekly intervals for liveweight using an electronic tag reader, automatic weighing and
drafting platform, to identify those animals whose performance was below their target
22
weight, and these animals were then drafted off and allowed to graze the bioactive swards.
Individual faecal samples (FEC) were taken fortnightly; pasture production measured
weekly and was used to set liveweight targets determined by ‘happy factor’ algorithm (Greer
et al 2010). Overall growth rates on the lambs grazing on the T. circumcincta and T.
colubriformis infected blocks were 252 g/d and 292 g/d respectively. Mean FEC were high
(> 2000 epg) for both sets of lambs, there were no significant differences in FEC between
animals grazing the main or hospital paddocks. For both pasture suites there was a
significant paddock time (p<0.05) early on that reflected a benefit of hospitalisation on LWG.
Of animals that required hospitalisation on either pasture suite over 80% had recovered
after 4 weeks grazing. However due to the poor establishment /growth of clover, chicory
and plantain it is not possible to judge the effectiveness of the bioactive forages on LWG or
in reducing worm burdens. Improved lamb performance is more likely to be a result of
reduced larval challenge.
23
Evaluating a molecular test for BZ resistance in field populations of Teladorsagia
circumcincta and Trichostrongylus colubriformis
JS Knight, TS Waghorn, SA Bisset and DM Leathwick
Hopkirk Research Institute, AgResearch Ltd, Private Bag 11008, Palmerston North 4442,
New Zealand
With anthelmintic resistance now widespread in parasitic nematodes of livestock in New
Zealand, it is becoming increasingly important to monitor the situation on-farm to ensure
that nematode control programmes remain effective. Faecal egg count reduction tests
(FECRTs) remain the most commonly used method to detect the presence of resistance,
but they tend to be labour intensive and lack the resolving power needed to identify
resistance in the early stages of development. New molecular techniques may enable
these shortcomings to be overcome.
Resistance to benzimidazole (BZ) anthelmintics is reportedly, predominately associated with
a single nucleotide polymorphism (SNP) in the codon for amino acid residue 200 (Phe to
Try) of the β tubulin isotype 1 gene. In Teladorsagia circumcincta a SNP at amino acid
residue 198 (Glu to Leu) has also been implicated. Allele-specific PCR assays were
developed to measure the incidence of the Phe200Try and Glu198Leu mutations in
T. circumcincta and the Phe200Try mutation in Trichostrongylus colubriformis. In a study of
larvae derived from cultures from a series of on-farm FECRTs, an average of 84% of
T. colubriformis from drenched lambs proved to be homozygous for the Phe200Tyr mutation
while 83% of T. circumcincta were homozygous for either this or the Glu198Leu mutation or
carried a combination of both. β tubulin gene sequence information suggested that other
SNPs may also contribute to resistance in both species. Correlations between BZ efficacy
(based on FECRTs) and the incidence of the resistant genotypes in unselected field
populations of both species were generally low with FECRTs underestimating the
frequencies of the putative resistance alleles. Possible explanations are the insensitivity of
the FECRT at low levels of resistance or that the mechanism of BZ resistance is polygenic
and recessive.
23
24
A study of parasitism in 12 horses over a 14 month period.
Ian Scott, Bill Pomroy
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
Knowledge of the biology of the gastrointestinal nematode parasites of horses under New
Zealand conditions is limited. A study was therefore undertaken to examine natural
infections in 12 horses of mixed ages kept at pasture for 14 months. Every month, 4 of the
horses were treated with anthelmintic and their faeces collected to allow the parasites
acquired in the 3 months since they were last treated, but now killed and expelled, to be
counted and identified. The following month, the next group of horses would be due for
treatment and so on. There was a marked difference in the levels of parasitism experienced
by individual animals. According to the worm counts some animals were allowing only
negligible numbers of worms to establish whilst others were harbouring several hundred
thousand. Variation in worm burden accounted for less than 1% of the variation in egg
count. The younger animals tended to have higher worm burdens (P<0.10). Worms were
acquired in all seasons with no tendency evident statistically for more to be acquired at
certain times of the year. However, higher proportions of larval stages (L4s) were present
during winter and spring, suggesting that more of the worms acquired in the autumn and
winter periods may have become inhibited in their development.
25
Migration as an escape from parasitism in New Zealand galaxiid fishes
Robert Poulin, G. Closs, A. Lill, A. Hicks, K. Herrmann, D. Kelly
Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand
Animal migration, involving mass movements over large distances and often across
inhospitable habitats, is one of the most spectacular behavioural phenomena. Parasite
avoidance is increasingly considered to be a potential driving factor in animal migrations. In
many marine and freshwater benthic fish, migration into a pelagic environment by
developing larvae is a common life history trait that could reduce exposure to parasites
during a critical window of developmental susceptibility. We tested this hypothesis on
congeneric fish (family Galaxiidae, genus Galaxias) belonging to a closely-related species
complex sampled from coastal streams in southeastern New Zealand. Migratory Galaxias
have larvae that migrate to pelagic marine environments, whereas the larvae of nonmigratory species rear close to adult habitats with no pelagic larval phase. Both migratory
and non-migratory fish are hosts to two species of skin-penetrating trematodes that cause
spinal malformations and high mortality in young fish. Using generalized linear models
within an Akaike information criteria and model averaging framework, we compared
infection levels between migratory and non-migratory fish while taking into account body
size and several other local factors likely to influence infection levels. For one trematode
species, we found a significant effect of migration: for any given body length, migratory fish
harboured fewer parasites than non-migratory fish. Also, no parasites of any kind were
found in juvenile migratory fish sampled in spring shortly after their return to stream habitats.
Our results demonstrate that migration spares juvenile fish from the debilitating parasites to
which they would be exposed in adult stream habitats. Therefore, either the historical
adoption of a migratory strategy in some Galaxias was an adaptation against parasitism, or
24
it evolved for other reasons and now provides protection from infection as a coincidental
side-effect.
26
Prevalence of periwinkle parasites.
Katie O'Dwyer & Robert Poulin
Evolutionary and Ecological Parasitology Group, 340 Great King Street, Dunedin 9054
Periwinkles are dominant gastropods on rocky shores around the world. A variety of
trematodes have been reported to use these gastropods as first intermediate host
throughout Europe and North America. However nothing is yet known about the trematode
parasites of New Zealand periwinkles. Here we identify two different trematodes and
present prevalence data from New Zealand periwinkles, Austrolittorina antipodum and
Austrolittorina cincta, found around Otago Harbour, Dunedin. It is likely that variation in
prevalence of these parasites is closely related to differences in shorebird abundance at the
sites studied, as they are likely to be the definitive host. These parasites reflect a higher
degree of biodiversity than meets the eye on the rocky shores of New Zealand.
27
High Prevalence of Leucocytozoon sp. in the Endangered Yellow-eyed Penguins
(Megadyptes antipodes) residing in the Sub-Antarctic Regions of New Zealand.
L.S. Argilla, L. Howe, B.D. Gartrell, and M.R. Alley.
New Zealand Wildlife Health Centre, Institute of Veterinary, Animal and Biomedical
Sciences, Tennent Drive, Massey University, Palmerston North, New Zealand
The yellow-eyed penguin (Megadyptes antipodes), or Hoiho, is endemic to New Zealand
and is one of the rarest species of penguin. Over the past 30 years, yellow-eyed penguins
have suffered major population declines with no single cause established. Leucocytozoon
was first identified in yellow-eyed penguins in 2005. During the 2006/07 and 2007/08
breeding seasons, Leucocytozoon was found in adults and chicks from Stewart Island but
was absent from mainland New Zealand birds. During the 2008/09 breeding season, a high
mortality was seen in both mainland yellow-eyed penguins as well as those on Enderby
Island. No single factor was identified as the cause of these mortalities. Using light
microscopy, PCR and histology, a high overall prevalence (67.8%) of Leucocytozoon spp. in
association with a high incidence of chick mortality during the November 2008-January
2009 breeding season was observed in the yellow-eyed penguin population on Enderby
Island of the Auckland Islands archipelago. A high prevalence (73.7%) was also observed
by PCR in the blood of adult Enderby YEPs during the 2006-07 season. In addition, one
chick had histological evidence of leucocytozoonosis with megaloschizonts formation in
multiple organs and tissues throughout its body. These findings were different from the low
prevalence previously detected by PCR. The Leucocytozoon spp. sequences detected in
the YEPs formed two distinct clusters. Group A comprises Leucocytozoon spp. from YEPs
25
across their range whereas group B comprises isolates only found on Enderby Island.
Overall, we conclude that the Leucocytozoon pathogen is common in yellow-eyed.
However, the Enderby Island yellow-eyed penguins are infected with a Leucocytozoon spp.
that is genetically distinct than that found in other yellow-eyed penguin populations. The role
of Leucocytozoon in the high levels of chick mortality in the yellow-eyed penguins remains
unclear.
28
Immunological competence of calves.
David Heath, Christine Robinson and Marshall Lightowlers
76 Paremata Road. Paremata, Porirua 5024
In examining the effect of maternal antibody on the response of calves to vaccination with
EG95 (a vaccine that protects them against hydatid disease), it was observed that calves
were not fully immunologically competent until 4-5 months of age. Maternally derived
antibody from vaccinated cows may provide some protection for the neonate, but may also
interfere with the active response to vaccination. Experiments were undertaken to determine
the optimal regime for protection of young cattle against Echinococcus. One group of
pregnant cattle received 2 vaccinations of EG95 antigen + Quil A adjuvant two months and
one month prior to calving. The control group of pregnant cattle were not vaccinated.
Calves were either challenged with E. granulosus eggs at 4, 9, 13 or 17 weeks post-birth or
were given their first vaccination at 8, 12 or 16 weeks post-birth. Sera obtained at regular
intervals were tested by ELISA to assess the immunological response. All calves were
experimentally challenged with E. granulosus eggs and subsequent necropsy confirmed the
levels of protection. Maternal antibody was shown to protect calves to some extent for at
least 17 weeks. Calves from vaccinated cows responded well serologically if the first
vaccination was given at 8 or 12 weeks, but full protection against a challenge infection was
achieved only if the first vaccination was delayed until 16 weeks after birth. Calves from
non-vaccinated cattle also were not fully protected if the first vaccination was at 8 or 12
weeks, but were fully protected if the first vaccination was at 16 weeks of age. No safety
problems were observed following two vaccinations of 40 pregnant cows or 30 suckling
calves.
29
Nitrogen metabolism in Haemonchus contortus and Teladorsagia circumcincta.
Saleh Umair, Ross Bland & Heather Simpson
The main goal of the study was to identify some key enzyme that can be used as targets for
vaccine/anthelmintic development. This is the first study to characterise proline, arginine
and lysine metabolism and aspects of glutamate metabolism in homogenates of L3 and
adult Haemonchus contortus and Teladorsagia circumcincta. The kinetic properties of
27 enzymes were determined. The genes encoding T. circumcincta glutamate
dehydrogenase (GDH) and arginine kinase (AK) and H. contortus AK were sequenced and
recombinant TcGDH, TcAK and HcAK expressed and biochemically characterised.
The ornithine-glutamate-proline pathway was fully functional.
The mammalian-like
saccharopine and pipecolate pathways of lysine catabolism, but no bacterial-like pathways
26
enzymes, were present in adult worms. The pipecolate pathway was incomplete in L3 of
both species. Interestingly, the enzymes of lysine catabolism were able to use both cofactors, which is not the case in mammals. The GS-GOGAT pathway of ammonia
incorporation into glutamate was present, except in L3 H. contortus. The TcGDH properties
were similar to that of H. contortus GDH. GDH activity was inhibited by GTP and stimulated
by ADP whereas ATP either inhibited or stimulated depending on the concentration and
direction of the reaction. The GABA shunt enzymes were not detected in homogenates of
L3 or adult worms.
Neither parasite had a fully functional ornithine urea cycle, nor appeared to use bacterial
pathways to covert arginine to ornithine. Nitric oxide synthase was demonstrated
histochemically in nerves of adult H. contortus, but was undetectable in homogenates of
both species. There was species variation in polyamine metabolism: T. circumcincta used
arginase to form ornithine, followed by decarboxylation by ornithine decarboxylase, while in
H. contortus there was the additional pathway of first decarboxylation by ADC to form
agmatine, then hydrolysis by agmatinase to putrescine. The present study helped in the
better understanding of nitrogen metabolism and these enzymes can be useful vaccine
targets if they differ antigenically from the host, provided the enzyme is accessible to
blockage by immune effectors.
30
CarLA and the immune response: how a worm glyco-lipid impacts on immune cell
function.
Joanna Roberts
CarLA is a glycolipid found on the epicuticle of infective larvae of Trichostrongylid
nematodes. While the naturally arising antibody response to this compound in sheep (when
present) will protect the animal from subsequent infection, purified CarLA is ineffective in a
vaccination strategy designed to protect sheep from parasite challenge. The immune
response to gastro-intestinal nematodes is initiated by cells of the immune system known as
dendritic cells (DC). An in vitro model of DC has been established and has been used to
study the effects of CarLA on the activation status of DC. Using flow cytometry to measure
levels of the antigen presenting receptor major histo-compatibility complex class II (MHC Cl
II), and co stimulatory molecules CD80 and CD86, we show that CarLA suppresses DC
activation induced by moderate levels of ‘danger signal’ such as lipopolysaccharide(LPS).
We also examine the possibility that contaminating endotoxin in our experimental system
may be masking the extent of CarLA’s immuno-suppressive action and discuss future plans
to address this.
31
Investigations into suspected ivermectin-resistant Ostertagia.
Ian Scott, Bill Pomroy
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
For many years the problem of anthelmintic resistance in cattle has largely been confined to
the relatively harmless nematode Cooperia onchophora. As yet there have been no
confirmed field reports from NZ of resistance to the most important bovine nematode
27
species, Ostertagia ostertagi. On one farm, cattle treated with ivermectin were extensively
monitored post-treatment and O. ostertagi was present at worrying levels in post-treatment
larval cultures. On this same farm, Ostertagia eggs reappeared in the faeces of cattle
treated with injectable ivermectin after 28 days - earlier than should have been possible
given the product’s claim for persistence of protection for at least 14 days. To further
investigate the situation on this farm, an egg count reduction test was conducted using 20
yearling heifers, all of which were treated with oral ivermectin and faecal samples were
collected on Days 0, 8, 10 and 14. In addition, a slaughter study was conducted using 12
recently weaned calves. The calves were infected with larvae recovered from the faeces of
other calves grazing the paddocks on the farm under investigation. Half of them were
treated with oral ivermectin, 25 days after infection and all calves were killed 7 days later.
The average egg count of the heifers pre-treatment was 225epg, of which according to
larval culture results, only 2% were Ostertagia. Egg counts were reduced by 68, 81 and
72% on Days 8, 10 and 14 respectively and efficacy against Ostertagia was calculated at
85, 100 and 44%. In the slaughter study, an average of 1200 O. ostertagi adults were
recovered from the control animals and only 15 from the treated animals (98.7% efficacy).
The findings of the present and previous work suggest that resistance to ivermectin in O.
ostertagi on this farm cannot yet be confirmed as being present, but may be developing.
Poster
1.
An overview of CARLA® and its applications in parasite management.
Sheralee Cleland and Richard Shaw
AgResearch, Palmerston North
CarLA (Carbohydrate Larval Antigen) is a molecule found on the surface of all
gastrointestinal parasite third stage larvae (L3s) that infect livestock. The immune system of
livestock can mount a response to this molecule by producing mucosal antibodies, which
bind to the surface of these L3s and have been shown to prevent their establishment in the
mucosa.
The concentration of these antibodies can be detected by an immunoassay of saliva
samples. CarLA antibody responses in saliva are moderately heritable (30%) and well
correlated with reduced faecal egg counts (genetic correlation 0.5; animals with elevated
CARLA antibodies have 20-30% lower FEC). This immune response is a useful mechanism
for selecting individual animals to breed host resistance against parasites into sheep flocks.
An added advantage is that young animals with elevated CARLA antibody response can be
up to 1.5kg heavier than none responders. Selective breeding for elevated CARLA antibody
levels should in time reduce farmers’ needs to regularly drench young stock.
28
List of Delegates
[This list is correct at the time the Proceedings went to print.]
Delagate
Pete Anderson
Dallas Bishop
Charlotte Bouchet
Mary Bowen
Richard Campbell
Victoria Chapman
Cathryn Christie
Sheralee Cleland
Dave Cole
Caroline Costall
Geoff De Lisle
Andrew Dowling
Hannah Field
Andrienne French
Jim Gibbs
Gavin Goble
David Heath
Allan Heath
Brendan Hickman
Joanne Holter
Laryssa Howe
Lewis Kahn
Tsukushi Kamiya
Jacqui Knight
Clement Lagrue
Melanie Lloyd
Sarah Lochore
Colin Mackintosh
Colin D MacLeod
Bernad Mariadass
Paul Mason
Robin McAnulty
Colin Mckay
Rob Nottingham
Katie O'Dwyer
Ann-Maree Oliver
Ian Page
Bill Pomroy
Robert Poulin
Bronwen Presswell
Haseeb Randhawa
Richard Olde Riekerink
Email address
[email protected]
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[email protected]
[email protected]
[email protected]
[email protected]
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[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
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[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
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[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
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Joanne Roberts
Peter Rolfe
Dave Rutherford
Dhrubajit Saikia
Christian Sauermann
Ian Scott
Richard Scott
Richard Shaw
John Southworth
Warren Tully
Saleh Umair
Mark Vickers
Tania Waghorn
Mark Watson
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
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