A Preliminary Study on the Gastrointestinal Helminth Parasites of Toads (Amietophyrnus Regularis)
Chapter One
Aim and objectives
The aim of this research is to determine the prevalence of intestinal helminths of toads (Amietophyrnus regularis) in Nnamdi Azikiwe University, Awka.
The objectives of this study were to;
- To identify intestinal helminths of toad in Nnamdi Azikiwe University.
- To determine the prevalence of helminths of toad with respect to sex of the
CHAPTER TWO
LITERATURE REVIEW
During the past decades the ecology and ecotoxicology of amphibians started to get attention (Sparling et al. 2000) because of global amphibian population declines (Houlahan et al. 2000). Based on the lists of the International Union for the Conservation of Nature (IUCN) there are 787 rare or endangered amphibian species (Frost et al. 2006) and about 1,900 species known to be threatened (Stuart et al. 2008). Frogs and toads are about 90% of all amphibians (McDiarmid and Micthell 2000) Therefore, they are an important link between
human and ecosystem health (Hayes et al. 2002) and they are main components of aquatic and terrestrial ecosystems (Unrine et al. 2007). Most adult frogs and toads feed on invertebrates, so they are important, energy-efficient trophic link between insects and other vertebrates (Sparling et al. 2000). They are sensitive to environmental changes both in terrestrial and aquatic habitats because they have highly semi-permeable skins and different life cycle stages (Alford and Richards 1999). Nevertheless, the information on the effects of environmental contamination on frogs and toads is little known (McDiarmid and Micthell
2000). The declines of amphibian populations are caused by a number of factors, including habitat loss and fragmentation (Icochea et al. 2002, Beebee and Griffiths 2005), ultraviolet radiation and chemical pollution (Blaustein et al. 2003), climate change (Pounds 2001)and epidemic disease like chytric fungus [Pounds et al. 2006]. Some of these factors may also cause deformities and abnormalities in their development (Blaustein and Johnson 2003) lowering further the viability of populations. Effects of contamination may result in shorter body length, lower body mass, malformations of limbs or other organs [Sparling et al. 2000]. Thus, the risk of mortality and exposure to predation is increased by slowed down development, late metamorphosis, and small metamorph size (Rowe et al. 2001, Pahkala et al. 2002, 2003). As a result, the use of anurans as bioindicators of accumulation of contaminants in pollution studies is increasing (Welsh and Ollivier 1998, Johansson et al. 2001, Loumbourdis et al. 2007).
In Nigeria, several literatures exist on the helminths parasites of toads. Their reports gave the estimates of the endemicities and epidemiological picture of these parasitic infections in different parts of the country. Iyaji et at., 2015 studied the gastrointestinal helminth parasites of Amietophyrnus regularis (African Common Toad) in Anyigba, Kogi State, Nigeria. A total of 120 specimens were examined for helminth parasites, 113(94.17%) toads were infected, while 7(5.8%) were uninfected. Helminth parasites recovered were 1576, comprising of 1 Cestode (Baerietta jaegerskioeldi )(2.50%) and 3 Nematodes: Amplicaecum africanum (92.50%), Cosmocerca ornate (16.67%) and Physaloptera spp. (6.67%). Nematodes had the highest occurrence with A.
africanum as the most prevalent. The cestode, (B. jaegerskioeldi) and the nematode, C. ornata exhibited specific sites of infection, being found in the small intestine and large intestine/rectum, respectively. Small intestine of hosts harboured the highest number of parasites with a prevalence of 90%. Although infection increased with the size of hosts examined, there was no significant difference in the infection of size categories. Similarly, there was no significant difference in the infection of male and female toad hosts (p>0.05). The toads with 1 – 10 worms had the highest frequency of infections, 61(50.83%). Multiple infections were recorded in several of the toad hosts, an indication
of the rich parasitic fauna of Amietophyrnus regularis in Anyigba.
Amuzie (2017) examined the helminth parasites of amphibians belonging to five families (Ptychadinidae, Bufonidae, Dicroglossidae, Raniidae and Pipidae) collected using the visual encounter and acoustic survey method from two communities (Agbada and Rumuesara) in Rivers State, Nigeria. The parasites included nematodes (Amplicaecu mafricanum, Oswaldocruzia hoepplii, Chabaudus leberrei, Cosmocerca ornata, Rhabdias sp., Rhabdias africanus and ascaridoid larvae), trematodes (Mesocoelium monodi, Diplodiscus fischthalicus, Prosotocus exovitellosus, Ganeo africana, Prosotocus exovitellosus, Haematoloechus exoterorchis and H. micrurus), Monogeneans (Polystoma spp.), cestodes (Baerietta sp. and Cephalochlamys compactus), pentastomids (Raillietiella sp.) and Acanthocephalans (cysthacants). Coefficient of variation of the prevalence rates in infected host specimens from Rumuesara showed that although the prevalence of infection of most of the parasites was higher in the family Ptychadinidae, the variation was low. On the other hand, prevalence of most of the multi -host parasites recovered from infected hosts from Agbada was higher in the Dicroglossidae and the coefficient of variation was also high indicating that infection was actually higher in this family than in the other amphibian families examined. However, the difference between the coefficients of variation between both locations was not significant.
Sulieman et al., (2015) carried out a research on helminths parasite of the subdesert toad Amoetophrynus (Bufo) Xeros (Anura: Bufonidae). In his research sixty- nine subdesert toads, Amietophrynus (Bufo) xeros, were collected in Shendi, Sudan, from August to November 2014, and examined for the first time for the presence of internal helminth parasites. Sixty – seven (97.1%) of the toads were found infected with one or more helminth species including, four Nematoda: Aplectana macintoshii, Rhabdias bufonis, Strongyloides prokopici, and Oswaldocruzia sp.; one Trematoda: Mesocoelium sp.; one Cestoda: Lanfrediella sp. A higher prevalence and intensity of infection was found in male toads compared with females, and old toads were found to harbor a higher prevalence and intensity of infection when compared to younger ones. However, neither of these differences was statistically significant.
CHAPTER THREE
MATERIALS AND METHODS
Study area
Nnamdi Azikiwe University, Awka is situated on the northern side of the Onitsha – Enugu Federal Highway, about 60km from Enugu and 35km East of Onitsha. Lying within Latitude 6˚14´N to 6˚14.5´N and Longitude 7˚8.6´E to 7˚9´E. UNIZIK is built on an area spanning over 502 hectares, with a vast expanse of land for development and expansion. The area experience two seasons, the dry season November-March and wet season April-Octber and with hammattan from December-January. It is a rain forest zone with an annual rainfall ranging from 100mm-150mm, (Ikpeze, 2007).
Sample collection
Amietophyrnus regularis males and females were collected; the toads were collected from three sites, Unizik first gate, behind Bakassi, and Garuba square. This was accomplished using the visual encounter and acoustic survey (VEAS) method and auditory surveys for calling anurans at night, between 7.00 pm and 10.00 pm, on each sampling day with the aid of flashlights. Ten specimens were collected from each study location during each visit which lasted for a period of two weeks without bias to species or size. The specimens were identified to species level using taxonomic keys (Schiotz, 1999; Rodel, 2000), after which it was taken to Zoology laboratory in Nnamdi Azikiwe University for dissection.
Examination procedure
Amphibians were euthanized in chloroform vapour. They were dissected longitudinally and the gut was separated from the viscera. The gut was cut into the sections: oesophagus, stomach, small intestine, large intestine and rectum. Other sections examined included lungs, urinary bladder and the body cavity. Thorough searching for helminth parasites was done using magnifying lens. Each section was placed separately in a Petri dish containing 0.70 % saline solution for examination and collection of parasites. The worms were then collected finely with the aid of forceps and transferred into the beaker containing saline solution. The recovered parasites were counted, recorded, and variously fixed and preserved in the 70% alcohol.
Identification
The identification of each worm was done by using Google Atlas Key as a guideline. Examination of the anterior mid gut and posterior regions of the worms were done using the x10 and x40 objectives of a light microscope. The work was analyzed using prevalence rate, Anova and Chi square statistical analysis.
CHAPTER FOUR
RESULTS
Out of the 32 Toads examined, comprising of 20 males and 12 females, 28 with a prevalence of (87.5%) specimens were found infected with helminth parasites. Nematodes and cestodes were the only helminths encountered with difference in species infection. The nematode species include; Amplicaecum africanum, Cosmocerca ornata and Physaloptera spp. Amplicaecum africanum had the highest prevalence 25 (78.1%) in both sexes, the males were more infected than females, followed by Cosmocerca ornata with a prevalence of 16 (37.5%) infecting both the males and the females at the same rate. Physaloptera spp had the lowest prevalence 9 (28.1%) infecting more females than the males. Only one species of cestode was found Baerietta jaegerskioeld infecting only 2 toads with a prevalence of (6.3%).
CHAPTER FIVE
DISCUSSION AND CONCLUSION
DISCUSSION
Amietophyrnus regularis from the three localities in Nnamdi Azikiwe University, Awka were found with large number of parasites involving two parasite taxa and four parasites species.
The infections with nematode parasites were quite common in the three localities but prevalence varied while the cestode infected hosts only from two localities. For instance, the nematodes Amplicaecum africanum, Cosmocerca ornata and Physaloptera sp. were common in the three localities but Amplicaecum africanum had the highest prevalence. This may be due to the fact that tropical zone experiences high rainfall and its vegetation consist mainly of tall trees, grassland and also for its biotic and abiotic factors, it is expected that the prevailing ecological conditions may affect the amphibian faunal composition of this area as well as influence the parasites infecting the anuran resident there (Aisien et al., 2001).
The overall parasites infection of 87.5% prevalence in this study compared
favourably with 99% recorded in 162 of the same host species examined in Ile-Ife (Ayodele and Akinpelu, 2004) and also with 71% recorded in 100 samples examined in Awka (Nworah and Olorunfemi, 2011). According to Hudson et al. (2006) and Lafferty (2008), parasites may play a role in promoting
biodiversity and function as indicators of ecosystem productivity and resilience. Among the parasites taxa recovered, nematodes had the highest infection rate. The high infection rate of nematode worms in Amplicaecum regularis is in conformity with other findings in Ile-Ife and Awka (Ayodele and Akinpelu, 2004; Nworah and Olorunfemi, 2011). Imasuen et al. (2012) reported that anurans serve as intermediate hosts of vertebrates’ parasites especially those that they inhabit the same habitat.
Nworah and Olorunfemi (2011), reported on the kinds of food materials recovered from the stomach of the amphibian investigated (snails, beetles, earthworms and mainly insect varieties). These invertebrates they eat serve as intermediate hosts to the amphibians, they ingest eggs evacuated from anuran hosts while the intermediate hosts are in turn ingested by the anuran hosts like A. regularis where they grow into adult or larval stages in the host.
The cestode parasite recovered occurred in a very low prevalence of 6.3% affecting more females than the males, which is similar to the reports of Ayodele and Akinpelu (2004) where the same host species were examined but in contrast to Nworah and Olorunfemi (2011) where no cestode was recovered from the same kind of species examined.
There was no evidence of the influence of sex on parasitic infection of Amietophyrnus regularis, both sexes were highly infected. A similar result was reported by Nworah and Olorunfemi (2011). The level of multiple infections and the number of worms recovered in this study was an indication of the rich parasitic fauna of Amietophyrnus regularis in Nnamdi Azikiwe University, Awka.
CONCLUSION
This study has shown that there is high level of parasitic infection in African common toads in Nnamdi Azikiwe University, Awka which is contributing to the ongoing declines in amphibian populations in the environment. These findings have opened the door for further research on amphibian parasitism, its threats to human health as they may infect frogs and fish in water, since they play vital role in the balancing of food chains and webs in the ecosystem.
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