Global Ecology and Conservation 4 (2015) 146–149
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Global Ecology and Conservation
journal homepage: www.elsevier.com/locate/gecco
Original research article
Gastro-intestinal helminths of goliath frogs (Conraua goliath)
from the localities of Loum, Yabassi and Nkondjock in the
Littoral Region of Cameroon
Nguiffo Nguete Daniel, Wabo Pone Josue ∗ , Mpoame Mbida
Laboratory of Biology and Applied Ecology, Department of Animal Biology, Faculty of Science, University of Dschang,
PO Box 067 Dschang, Cameroon
article
info
Article history:
Received 10 June 2015
Received in revised form 26 June 2015
Accepted 30 June 2015
Keywords:
Gastro-intestinal helminths
Conraua goliath
Species richness
Diversity
Cameroon
abstract
The gastro-intestinal helminth parasites of goliath frog (Conraua goliath) from the Littoral
Region of Cameroon in the Localities of Loum, Yabassi and Nkondjock were surveyed. Out
of the 30 goliath frogs examined (13 males and 17 females) between April and May 2013,
26 (85%) contained at least one helminth parasite and yielded a total of nine hundred and
seventy three (973) helminths comprising: Nematodes (90.5%), Trematodes (9.4%) and Pentastomids (0.1%). Nematodes included: Africana taylori (60%), Oswaldocruzia perreti (0.2%),
Aplectana sp. (21%), Gendria sp. (7.1%), Amphibiophilus sp. (0.2%), Strongyluris sp. (0.1%),
Physalopteroides sp. (1.6%), and Oxyuridae gen. sp. (0.3%). Trematodes comprised: Mesocoelium sp. (7.3%) and Diplodiscus subclavatus (2.1%). Pentastomids were represented by
Sebekia sp. (0.1%). The mean species richness and diversity were 1.97 ± 2.12 and 0.41 ± 0.04
respectively. The intensity of parasite infection was correlated with host body weight, positively for Africana taylori, Aplectana sp., Diplodiscus subclavatus, and Mesocoeliumsp. Infection rates were influenced by land-use pattern. Thus higher prevalences were observed in
Loum (intensive agricultural area).
© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC
BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction
Cameroon has a diverse Anuran fauna with at least 200 different species (Depierre, 1978). The goliath frog is the largest
known frog with a maximum weight of 3.3 kg (Boulenger, 1906) and is endemic in Cameroon and Equatorial Guinea. These
frogs are classified as endangered species by International Union for Conservation Nature (IUCN) and as protected species
of class ‘A’ by the Wildlife Law in Cameroon. Little information is available on the helminth parasites of amphibians from
Cameroon (Dollfus, 1929, Gassmann, 1975, Durette-Desset and Vaucher, 1979, McAllister et al., 2010). To the best of our
knowledge, the parasites of goliath frogs have not been studied. The objective of this study therefore was to establish an
initial helminth list for C. goliath and also determine their helminth richness and diversity.
2. Materials and methods
The goliath frogs were collected from 3 localities of the Littoral Region of Cameroon: Loum (4°42′ 58′′ N, 9°44′ 11′′ E) with
300 m of altitude, Yabassi (4°45′ N, 9°96′ 67E) and Nkondjock (4°87′ 36′′ N, 10°24′ 86′′ E). Mean annual precipitation in this
∗
Corresponding author.
E-mail address: [email protected] (W.P. Josue).
http://dx.doi.org/10.1016/j.gecco.2015.06.009
2351-9894/© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/
licenses/by-nc-nd/4.0/).
N.N. Daniel et al. / Global Ecology and Conservation 4 (2015) 146–149
147
Table 1
Infection pattern of Conraua goliath by gastro-intestinal tract helminths from Loum, Yabassi and Nkondjock in the Littoral Region in Cameroon.
Helminths
Sites of infection
Localities
Loum
Yabassi
Nkondjock
Prévalence
n(%)
Mean
intensity of
infection
Prévalence
n(%)
Mean
intensity of
infection
Prévalence
n(%)
Mean intensity
of infection
Large intestine
Large intestine
Large intestine
Large intestine
Large intestine
Large intestine
Large intestine
Small intestine
61(9.6)
161(25.4)
368(58.1)
2(0.3)
0(0)
0(0)
0(0)
2(1.3)
8.71 ± 6.6
32.2 ± 47.27
90 ± 130.83
2 ± 0.00
0±0
0±0
0±0
8 ± 0.00
1(0.3)
40(15)
182(61.3)
0(0)
1(0.3)
16(4.9)
3(0.9)
0(0)
1 ± 0.00
9.8 ± 7.66
28.71 ± 21.91
0±0
1±0
16 ± 0
3±0
0±0
5(11.3)
3(6.8)
34(77.3)
0(0)
0(0)
0(0)
0(0)
0(0)
1.66 ± 1.15
3 ± 0.00
4.85 ± 3.02
0±0
0±0
0±0
0±0
0±0
Small intestine
Large intestine
13(2)
20(3.2)
Large intestine
0(0)
Nematoda
Gendria sp.
Aplectana sp.
Africana taylori
Amphibiophilus sp.
Strongyluris sp.
Physalopteroides sp.
Oxyuridae gen. sp.
Oswaldocruzia perreti
Trematoda
Mesocoelium sp.
Diplodiscus
subclavatus
0±0
2.6 ± 2.6
57(17.3)
0(0)
0.0 ± 0.00
0(0)
19 ± 18.73
0±0
1(2.3)
0(0)
1 ± 0.00
0±0
Pentastomids
Sebekia sp. (nymph)
Species richness
Diversity
2.36 ± 2.76
0.46 ± 0.05
0±0
2.37 ± 2.44
0.46 ± 0.05
1(2.3)
1 ± 0.00
1.18 ± 2.13
0.31 ± 0.03
n = intensity.
Region is about 3909.7 mm with annual temperature ranging between 20 and 27 °C (Rouche, 2012). The predominant
vegetation in the study area is forest (semi deciduous and biafrean). A total of 30 goliath frogs (13 males and 17 females)
were sampled as follows: Loum 11, Yabassi 8 and Nkondjock 11. They were collected between April and May 2013 by hand
and peach net during the night. Frogs were transported to the laboratory and anesthetized with benzocaine. Postmortem
examination was carried out within 18 h of collection. The gastro-intestinal tract (GIT) divided into small and large intestine
was opened using the small scissors and the exudate examined. After successive washings and sedimentation of the
intestinal contents, helminths were collected using a pair of tongs (Meyer and Olsen, 1980; Euzeby, 1982).
Nematodes were fixed in hot (65 °C) AFA (alcohol formalin acetic acid) solution and thereafter conserved in vials
containing fresh 70% alcohol. Nematodes were cleared in pure glycerin. Trematodes and Pentastomids were also conserved
in vials with fresh 70% alcohol. Before examination they were dehydrated by enhanced concentration of alcohol (35%, 70%,
80%, 95%, and 100%) for 1 h in each concentration, colored by Semichon Carmine acetic acid and cleared by xylene (Meyer
and Olsen, 1980; Euzeby, 1982). Prevalence is defined as the percentage of frog infected with a helminth species and mean
intensity as the mean number of a helminth species in infected frog. Species richness is the number of helminth species
per host (Bush et al., 1997). The diversity was calculated by Shannon’s Weaver index accounts for both abundance and
evenness of the species present. The proportion of species i relative to the total number of species (pi) was calculated, and
then multiplied by the natural
 logarithm of this proportion (ln pi). The resulting product was summed across species, and
multiplied by −1. (H ′ = −
Pi log2 Pi.)
Helminths were identified by observation and measurement of morphological characteristics based on descriptions from
literature (Dollfus, 1929, Popova, 1965, Maeder, 1973, Gassmann, 1975, Chabaud, 1978, Durette-Desset and Vaucher, 1979,
Baker, 1981, Schmidt and Robert, 1981, Soulsby, 1982, Euzeby, 1982, Durette-Desset, 1983, Smyth, 1996, Aisien et al.,
2009 and Imasuen and Aisien, 2012). Determination of the genera and species was confirmed by Charles Bursey of the
Pennsylvania State University.
3. Results
The GIT helminth communities of goliath frogs consisted of 11 species (Table 1): 8 Nematodes, (Africana taylori, Oswaldocruzia perreti, Aplectana sp., Gendria sp., Amphibiophilus sp., Strongyluris sp., Physalopteroides sp., and Oxyuridae gen. sp.).
2 Trematodes (Mesocoelium sp. and Diplodiscus subclavatus) and 1 larval Pentastomids (Sebekia sp.). 85.95% of goliath frogs
were infected with one or more helminth species (100% in Loum, 90% in Yabassi and 67.85% in Nkondjock). The infection
pattern in different localities is presented in Table 1. Some species were characteristic of localities like O. perreti, Amphibiophilus sp. and D. subclavatus which were confined in Loum whereas Physalopteroides sp., Strongyluris sp. and Oxyurid were
restricted to Yabassi, nymph of Sebekia sp. found only in Nkondjock. Other helminths like Mesocoelium sp., Gendria sp. and
Africana taylori occurred in the 3 localities. The trematodes such as Mesocoelium sp. were more prevalent in Yabassi (17.3%)
and Nkondjock (2.3%).
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N.N. Daniel et al. / Global Ecology and Conservation 4 (2015) 146–149
The mean helminth richness was 2.36 ± 2.76; 2.37 ± 2.44 and 1.18 ± 2.13 respectively in Loum, Yabassi and Nkondjock.
However, the mean overall richness was 1.97 ± 2.12. The mean helminth diversity was the same at Loum and Yabassi
(H = 0.46) and lower at Nkondjock (H = 0.31).
Concerning infection in relation to host body weight, correlations between species were positive and not significant
(P > 0.05) for Mesocoelium sp. (r = 0.19) and significant (P ≤ 0.05) for A. taylori (r = 0.7), Aplectana sp. (r = 0.75) and
D. subclavatus (r = 0.79).
4. Discussion
The helminth species found in goliath frogs in the present study are most similar to those observed amongst the
amphibian hosts in other African countries except for the nymph of Sebekia sp. which has several fish species as intermediate
host (Christoffersen and De Assis, 2013). The occurrence of this nymph as observed during this study could be due to the
fact that the goliath frogs shared the same habitat with crocodiles (definitive host) and fishes (intermediate host).
Frogs from Loum and Yabassi had the highest overall helminth diversity with species richness of 2.36 and 2.37 respectively whereas those from Nkondjock had the lowest diversity and richness. This observation shows the importance of variation in host habitat due to the degree of practicing agricultural activities, deforestation and poaching in different localities.
Nguessu (2013) examined the liver weight of goliath frogs (increase with accumulation of toxic product) in same localities
and recorded a significant difference at Loum where intensive agriculture is practiced compared to Yabassi and Nkondjock.
The helminths that have direct life cycles may be an important factor contributing to species richness and community
complexity. In the present study, 5 helminths species (45%) all of which are nematodes (Gendria sp, Aplectana sp., A. taylori,
O. perreti, Amphibiophilus sp., Strongyluris sp., and Oxyuridae gen. sp.) are believed to have direct life cycles (Anderson, 2000).
Gendria sp., Aplectana sp. and A. taylori composing 27% of all helminths found in this study were frequent in their occurrence
(Loum, Yabassi and Nkondjock) and contribute to the complexity of helminth communities of goliath frogs.
Seven species (O. perreti, Amphibiophilus sp., Strongyluris sp., Physalopteroides sp., Oxyuridae gen. sp., D. subclavatus,
Sebekia sp.) were found only at one locality. The absence of helminths in C. goliath from one or more localities may be due to
the lack of a favorable environment for growth by either the parasite, an appropriate host, or both. The occurrence of O. perreti
in frogs only in Loum may be due to the fact that Loum is an agricultural zone and it is highly deforested. Aisien et al. (2011)
and McKenzie (2007) had observed Oswaldocruzia sp. only in agricultural zones and pasture environments respectively. It is
likely that, this parasite is more frequent in agricultural and polluted environments. Regarding the helminth that occurred
in frogs at all locations, the degree to which each habitat (locality) was preferred by these species, as indicated by prevalence
and mean intensity, did vary considerably. This again indicates the importance of local factors.
In conclusion goliath frogs showed a wide variation in helminthic fauna. Observations from this study are indicative of
some relationship between the pattern of parasitism and land use by goliath frogs in Littoral Region of Cameroon. The ecology
of goliath frog (habitat and diet in particular) and helminth transmission dynamics are important in shaping helminth
community structure. Moreover anthropogenic land use effects and their associated impact on water bodies are important
co-factors related to the abundance of helminths in goliath frogs like it was the case in Loum.
Acknowledgments
We are very grateful to Dr. Charles Bursey (Pennsylvania State University), USA for his assistance in helping us to identify
the isolated helminths; to the Ministry of Forestry and Wildlife who permitted us to work on this frog and to Dr. Kana
Raphael and Nguessu Charles (University of Dschang) for their assistance. We also thank Dr. Khan Payne of the Animal
Biology Department for reading and correcting the manuscript.
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