The Northeast Wildlife Disease Cooperative
Offering wildlife health and disease services in the Northeast U.S.
Phone: 508-887-4933
Email: [email protected]
http://sites.tufts.edu/nwdc
N W DC NOT E S
QUARTERLY NEWSLETTER FROM THE NORTHEAST WILDLIFE DISEASE COOPERATIVE
Volume 3, Number 1, January 2016
Maine Department of Inland
Fisheries and Wildlife, Adult Cow
and Calf Moose Survival Study
Lee Kantar, MDIFW State Moose Biologist
PROJECT UPDATE JANUARY 2016
Background
In the early 2000’s, New Hampshire Fish and Game
identified periodic winter tick epizootics as a significant
factor in overwintering calf mortality. As far back as the
1990’s, winter tick infestations were recognized as a
potential influence on population dynamics because
they could create an energy drain, particularly in young
moose (calves and yearlings). Over the past decade,
mortality data, necropsies, and winter tick surveys on fall-harvested moose have provided additional insight
into factors contributing to the species' population
trends. Observation, recovery, and necropsies of moose
calves have shown that the anemia associated with
winter tick infestations increases mortality, and that
lungworm (Dictyocaulus sp.) and tapeworm cysts
(Echinococcus granulosus canadensis) may also
contribute to mortality by reducing lung function.
Calves enter their first winter in a negative energy
balance and may even lose weight because there are
no fat reserves to draw upon over winter. In winters
that have deep snow and extreme cold temperatures
the energetic demands of calves increase even more.
These environmental elements, when combined with
both external and internal parasite loads, may lead to
increased winter mortality; in years with heavy tick
loads, an epizootic may occur. Increased calf loss can
have a profound effect on recruitment and population
size in moose.
The influence of winter ticks on all age classes of
moose is related to annual winter tick abundance,
moose density, habitat, and environmental conditions
(fall/spring temperatures, winds, and snow depth).
Currently, we are working with New Hampshire Fish
and Game and University of New Hampshire to
understand this dynamic, evaluate causes of mortality
in moose, and compare regional differences. To this
end we will be able to compare moose population
densities and environmental conditions between study
sites in Coos County, New Hampshire, the
Jackman-Moose River area of Maine, and the Fish River
Lake area between Allagash and Portage, Maine.
Cow and Calf Capture and Collaring
In January 2014, New Hampshire and Maine initiated a
coordinated and parallel study of adult cow and calf
survival. New Hampshire captured and radio-collared
43 moose and Maine captured and radio-collared 60
moose. In 2015, a total of 44 moose were captured in
NH, and total of 45 in ME. This past month, Maine
added a second study area on the northern border
with New Brunswick, Canada. Thirty-five adult cows
and 35 calves were collared, in addition to 36
additional calves in the original (western) study area.
NH collared 45 moose in 2016. Since the collaring study
was initiated in 2014, a total of 149 moose in Maine are
currently fitted with GPS collars. These collars forward
an email to biologists when reduced activity is
detected so that the situation and potential mortality
can be investigated within 24 hours. They also send
location data that provide valuable information on
moose movements, habitat usage, and the location
and timing of calving. This is one of the largest GPS
collar studies on moose in North America.
During collaring, biological samples including blood,
feces and hair were collected from all individuals and
standardized winter tick counts were done (Fig. 1).
Collared moose in NH and ME are then monitored daily
for mortalities and are recovered for necropsy. This
winter, for the first time in the study, moose calves
NWD C NOT ES – Quarterly Newsletter From The Northeast Wildlife Disease Cooperative
Figure 1. Lee Kantar conducting winter tick count on a female calf
that was captured and collared. From left to right: Sam Davison
(Native Range Wildlife Capture), Lee Kantar, Jeanne Ross (Wildlife
Veterinarian).
were weighed at capture, providing a measure of body
condition as they enter the winter. In addition to
weighing calves, winter tick counts (4-10 cm transects)
were also conducted on the shoulder and rump of each
calf using the same methods as used in our winter tick
counts on hunter harvested moose done in the fall.
Calf Weights and Tick Burdens: Results
There was no statistical difference in weight at capture
between Maine’s two study areas. In our western study
area, calf capture weights averaged 428lb with no
difference between males and females. In our northern
study area, calf capture weights averaged 414lbs, with
females averaging 406 and males 425. Weighing calves
at death will enable us to detect significant changes in
body condition between capture and mortality,
providing critical information relating to potential
cause of death.
There was no difference between the two study areas
in counts of winter ticks on the shoulders of live
calves. However, the counts were higher than the
mean of fall hunter harvested winter tick counts of
both adults and calves. Winter tick counts were also
higher during the 2016 collaring than in 2014 and
2015 capture events. Although it is not clear what this
means in terms of survival, it could predict increased
winter/spring calf mortality.
Necropsy
MDIFW biologists recover and necropsy moose using
Volume 3, Number 1, January 2016
a protocol adapted from Minnesota Department of
Natural Resources and further modified by the
University of Maine-Animal Health Lab (UMAHL), New
Hampshire Fish and Game Department, and the
University of New Hampshire Diagnostic Lab. This
protocol includes assessment of the mortality site,
winter tick count, blood collection, field necropsy,
aging, and collection of tissue samples from all organs
for diagnostics and analysis. University of Maine-Animal
Health Lab (UMAHL) receives all blood and fecal
samples after live capture and after death. UMAHL
catalogues and processes all tissue samples and
analyzes blood parameters and internal parasites from
capture. Blood samples are also sent to additional labs
to test for pregnancy of adult cows, to examine
physiological parameters/body condition assessment
(blood chemistry), heavy metal toxicity, screening of
vector borne diseases as well as other pathogenic
agents known to moose. Results from the New
Hampshire and Maine moose studies will be compared
and further assessed, and summarized for subsequent
reports.
Cow/Calf “Walk-ins”
Part of MDIFW’s moose survival project includes
examining cow productivity and survival of calves in
order to understand population trends. Each year of the
study, beginning in May, biologists monitor the status
and fate of radio-collared adult female moose and their
potential calves. Current knowledge of neonatal moose
survival would suggest that losses of 50% or more can
occur due to factors such as bear predation and
malnutrition. Due to concerns over the impact of
radio-collaring
neonates,
and in
consultation
with moose
researchers
from Minnesota
as well as work
done in Ontario
and
Scandinavia,
MDIFW adopted
a non-invasive
Figure 2. Winter tick infestation on rump of dead
monitoring
moose calf. Photo by Lee Kantar.
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N WD C N OT ES – Quarterly Newsletter From The Northeast Wildlife Disease Cooperative
approach based on research done at the University of
New Hampshire. This includes monitoring GPS locations
and movements of adult cows to confirm initiation of
calving. Researchers have documented long range
movements of pregnant cows to calving areas followed
by clusters of GPS locations where the cow has
potentially calved. By pinpointing these locations,
biologists can stalk the cow using traditional VHF
telemetry and determine whether the cow has a calf at
heel or not. Biologists “walk-in” to the location indicated
by telemetry several times a week until a calf is
documented to be with the cow or it is determined that
no calf was born. Once a calf is documented, walk-ins
are reduced to one per week until the calf dies or until
the probability of its survival is significantly higher,
usually after about 12 weeks of life.
Moose are an icon of the North Woods. This
collaborative study with New Hampshire will provide a
greater understanding of the influence of winter ticks
on moose populations in the Northeast. Assessing
survival rates of adult cows and calves over time and
across the North Woods will help guide future moose
management. We hope that this study, following an
unprecedented number of collared moose across three
study areas, will provide insight into moose population
dynamics that will help conserve these magnificent
animals for future generations.
We gratefully acknowledge the work of Dr. Peter Pekins
at the University of New Hampshire Wildlife and
Conservation Biology Department; Kristine Rines,
Moose Project Leader for the New Hampshire
Department of Fish and Game; Dr. Anne Lichtenwalner,
Director of the Animal Health Lab at the University of
Maine Orono; and, Dr. Inga Sidor, Senior Pathologist
with the University of New Hampshire, Veterinary
Diagnostic Laboratory.
For additional details, see the following references:
Bontaites, K. M., and K. Gustafson. 1993. The history and
status of moose and moose management in New Hampshire.
Alces 29:163-167.
Musante, A. R., P. J. Pekins, and D. L. Scarpitti. 2007. Metabolic
impacts of winter tick infestations on calf moose. Alces
43:101-110.
Samuel, W. M. 2007. Factors affecting epizootics of winter
ticks and mortality of moose. Alces 43:39-48.
Schwartz, C.C. 2007. Reproduction, natality and growth.
Pages 141-171 In A.W. Franzmann and C.C. Schwartz. Editors.
Volume 3, Number 1, January 2016
Ecology and Management of the North American Moose.
University Press of Colorado. Boulder, Colorado. USA.
What’s New with LPDV?
Turkeys with Pox-like Lesions in NJ and VT
In October 2015, Bill Stansley of the NJ Division of Fish
and Wildlife submitted a male turkey to the NJ Animal
Health Diagnostic Laboratory (NJAHDL) for diagnosis.
The bird was in a flock on a private property where the
resident observed it lying on the ground and noted that
it was easily approachable. The bird died on the
property soon thereafter and had proliferative lesions
on the head and neck (Fig. 3) suggestive of either avian
pox or lymphoproliferative disease virus (LPDV).
Dr. Angelique Leone, pathologist at the NJAHDL,
examined the bird and determined that it had avian
pox, and probably not LPDV disease, based on histologic examination. Avian pox causes dermatitis characterized by intracytoplasmic inclusions (sites of virus
replication within a cell) within the hyperplastic epidermis (skin surface with abnormal cell growth). In
contrast, while LPDV can cause pox-like skin lesions, it
also induces
lymphoid tumors.
The turkey in this
case did not have
the lymphoid
tumors characteristic of LPDV.
In late October
2015, a hunterkilled adult wild
Figure 3. Pox lesions on a wild turkey from
turkey was
New Jersey. Photo by Angelique Leone.
submitted to VT
Wildlife Division for examination because of the
abnormal appearance of its head and legs. The turkey
was examined by Alyssa Bennet and Joel Flewelling in
the Rutland office who found the raised, nodular,
scab-like lesions of the skin that are characteristic of
both LPDV and avian pox (Fig. 4). Their gross necropsy
revealed none of the internal lesions associated with
LPDV, especially any swelling or discoloration of the
spleen or liver (Fig. 5).
In both the NJ and VT cases, LPDV could also have been
present in the birds, but did not appear to be causing
any overt disease.
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N WD C N OT ES – Quarterly Newsletter From The Northeast Wildlife Disease Cooperative
LPDV Discovery and Distribution in N. America
Outbreaks of LPDV were originally documented in
domestic turkeys in the European-Middle Eastern
region during the 1970s, but the virus had never been
detected anywhere else until recently. In 2009, LPDV
was identified by researchers at the Southeastern
Cooperative Wildlife Disease Study (SCWDS) in a wild
turkey from Arkansas. This was the first reported case of
LPDV in a wild bird and in North America. The inability
to culture the virus
has hampered
researcher’s
progress in further
understanding
LPDV, and made it
challenging to
interpret PCR
results.
Figure 4. Pox lesions on the leg of a wild
In domestic
turkey from Vermont. Photo by Kerry
turkeys, disease
Monahan.
due to LPDV
infections is typically first observed around 8-10 weeks
of age, with variable flock mortality that can reach 25%.
The most commonly affected organs were spleen,
thymus, pancreas, and liver, although smaller lesions
can be present in other tissues as well. It appears that
the natural host range of the virus is restricted to birds
of the order Galliformes.
A recent study that screened for LPDV DNA using PCR
in asymptomatic hunter harvested birds in the eastern
U.S. revealed that, across 17 states, a total of 47% of
turkeys were positive for LPDV. The highest prevalence
was in the Northeast, followed by the Mid-Atlantic,
Southeastern, and Central states. Causes of regional
differences in prevalence are unknown, but could relate
to turkey population densities, habitat availability,
artificial movement of infected birds, or interactions
among different domestic and wild turkey flocks.
Overall, the known distribution of LPDV in wild turkeys
extends from Maine to Florida and as far west as
Colorado. The high prevalence of asymptomatic turkeys
that are positive for LPDV also indicates that infection is
common but only occasionally causes disease. The
conditions that induce LPDV disease in wild turkeys are
unknown.
It appears that adult wild turkeys are more likely to be
positive for LPDV than are juveniles. Though the cause
Volume 3, Number 1, January 2016
of the higher prevalence in adults is unknown, it is
possible that increased age simply allows for a longer
period for virus exposure. Surveillance for LPDV has not
been conducted in wild turkey poults, which may have
higher levels of mortality than juvenile and adult
turkeys.
Update on Diagnostic and Surveillance
Techniques
As stated above, it has not been possible to isolate
LPDV using cell culture, a method that has long been
considered the gold standard for viral diagnostics.
Therefore, researchers have relied on PCR in turkey
bone marrow, liver and spleen. A recent study
comparing detection rates using PCR on liver, spleen,
and bone marrow of wild turkeys in the eastern U.S.
showed that bone marrow provided the highest level
of detection for both hunter harvested turkeys and
diagnostic cases. Bone marrow is easily and efficiently
collected from dead animals, making it very useful for
post-mortem LPDV surveillance and archiving. A
separate study showed that PCR on whole blood
produces results comparable to bone marrow, making
whole blood collection a useful tool for surveillance in
live birds.
Further Research
In sum, surveillance data suggest that LPDV is endemic
in wild turkeys in the eastern USA, but only causes
occasional disease. It may be more likely to cause
disease when an animal is already infected by another
immunosuppressive virus (e.g. avian pox), or is
otherwise immune compromised. Further research is
needed to understand modes of transmission and
pathogenesis in
wild turkeys, and
to determine the
L
impacts of LPDV
on their
S
populations.
L
For additional
details on LPDV,
Figure 5. Normal viscera found on necropsy of see the following
turkey from Vermont. Photo by Kerry Monahan. references:
L = liver; S = spleen
Allison, A.B. et al.
(2013) Avian oncogenesis induced by lymphoproliferative
disease virus: a neglected or emerging retroviral pathogen?
Virology 450–451: 2–12. doi: 10.1016/j.virol.2013.12.013
PMID: 24503077
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N WD C N OT ES – Quarterly Newsletter From The Northeast Wildlife Disease Cooperative
Thomas, J.M., et al. 2015. Molecular Surveillance for
Lymphoproliferative Disease Virus in Wild Turkeys (Meleagris
gallopavo) from the Eastern United States. PLoS ONE 10(4):
e0122644. doi:10.1371/journal.pone.0122644
Alger, K., et al. 2015. Diagnosing lymphoproliferative disease
virus in live wild turkeys (Meleagris gallopavo) using whole
blood. Journal of Zoo and Wildlife Medicine. 46(4):806-814.
Narrowing the Focus of the Wellfleet
Bay Virus Investigation: Annual
Movement Patterns of Satellitemarked Common Eiders Breeding in
Boston Harbor, Massachusetts
Lucas Savoy, Biodiversity Research Institute, Portland,
Maine
Between 1998 and 2015, 14 recognized mortality events
occurred in Common Eiders (Somateria mollissima)
along the coast of Cape Cod, Massachusetts. The
numbers of eiders involved in each outbreak ranged
from 30 to 2,800 individuals, with estimated total losses
exceeding 7,000 birds. In 2010, a novel orthomyxovirus
named Wellfleet Bay Virus (WFBV) was isolated from
tissues of four of these birds.
In 2012, biologists along the North Atlantic coast visited
several Common Eider nesting colonies to collect blood
samples to screen for the presence of antibodies to
WFBV. The presence of these antibodies would indicate
whether birds had been exposed to the virus. Eiders
nesting in Nova Scotia, Quebec, Maine and
Massachusetts were sampled, as were wintering eiders
in Rhode Island. Overall, 6% of eiders from Nova Scotia,
0% from Maine, and 4% from Rhode Island had
antibodies to WFBV. The largest percentage of eiders
with WFBV antibodies (41%) occurred in Massachusetts,
and most of these birds (96%) were located on one
nesting island in Boston Harbor.
Eider banding conducted in breeding and molting
areas along the Atlantic has provided information on
geographic distribution via hunter-harvested
recoveries of banded birds. However, detailed
information on movements were lacking, and prior to
2012, there were no bandings of eiders associated with
Boston Harbor breeding colonies. Therefore, in the
spring of 2013, an interagency team1 initiated a study
aimed at identifying the annual movements of eiders
breeding in Boston Harbor, and determining the
Volume 3, Number 1, January 2016
potential for mixing between Boston Harbor eiders and
eiders in other geographic areas. A total of 47 adult
eiders breeding in Boston Harbor were marked with
satellite transmitters from 2013-2015 (n = 12 in 2013; n =
19 in 2014; n = 16 in 2015). The transmitters have the
ability to provide location data for 4 hours at 72-hour
intervals for 2.5 years. So far, a total of 38 eiders have
provided location data. These data reveal that the eiders
marked in Boston Harbor molted in areas of Maine,
Massachusetts (including Boston Harbor), the Gulf of St.
Lawrence and Labrador, Canada. The birds wintered in
Boston Harbor, Nantucket Sound area, and Long Island
Sound. One of the marked birds died in November 2013
at Wellfleet Bay during the same time period as the eider
WFBV die-off that season, indicating that some eiders
nesting in Boston Harbor are involved in the cyclical
mass mortality events. This observation is supported by
a concurrent study of the genetic composition of eiders,
which shows that approximately 30% of eiders found
dead at Wellfleet are genetically similar to samples
collected from nesting females in Boston Harbor.
Overall, results from transmitters show that eiders
nesting in Boston Harbor can travel throughout the
entire range of the American common eider, which
extends from Long Island, NY to Labrador, Canada. This
means that eiders from a potential virus source area
(Boston Harbor) may mix with several other Atlantic
populations of eiders throughout their annual cycle.
1
Biologists who collaborated in this study were from the
USFWS, Biodiversity Research Institute, Massachusetts
Division of Fisheries and Wildlife, USGS Patuxent Wildlife
Research Center, and Massachusetts Department of
Conservation and
Recreation, with
logistical support
from the
Massachusetts
Water Resources
Authority,
Winthrop, MA.
Figure 6. Geographic
extent of Common
Eiders testing positive
for WFBV antibodies
and tagged with
satellite transmitters
from Boston Harbor
breeding colonies,
2013-2014.
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