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Molecular epidemiology of gastrointestinal parasites in farmers and their ruminant livestock from Ghana

Squire, Sylvia Afriyie (2019) Molecular epidemiology of gastrointestinal parasites in farmers and their ruminant livestock from Ghana. PhD thesis, Murdoch University.

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Gastrointestinal (GIT) parasites can cause economic losses in livestock production. Among the GIT parasites infecting ruminant livestock are zoonotic species including Cryptosporidium, Giardia duodenalis and Trichostrongylus sp. that can cause severe diarrhoea and other symptoms in humans. However, nothing is known about the species and subtypes of these zoonotic parasites in farmers and their ruminant livestock in Ghana. Therefore, the aim of this thesis was to determine the prevalence and species of these parasites in these two groups.

A total of 925 faecal samples were collected from humans (n=95), cattle (n=328), sheep (n= 217) and goats (n=285) from the Coastal Savannah agroecological zone of Ghana. Faecal samples were examined by microscopy and/or molecular techniques to determine the gastrointestinal parasites present and genetically characterise the species of Cryptosporidium, Giardia duodenalis and Trichostrongylus present. The farmers were interviewed using a structured questionnaire on farm management systems and practices to determine the risk factors associated with parasites detected in the livestock. Faecal consistency and body condition scores of the animals were also recorded to determine their association with specific parasite infections.

This thesis describes the first molecular study of Cryptosporidium and Giardia in livestock in Ghana and the identification of zoonotic species. The prevalence of Cryptosporidium and Giardia by quantitative PCR (qPCR) at the 18S rRNA and glutamate dehydrogenase (gdh) loci was 8.4% and 10.5% in humans, 26.5% and 8.5% in cattle, 34.1% and 12.9% in sheep, and 33.3% and 12.3% in goat faecal samples, respectively. Molecular typing of G. duodenalis at the triose phosphate isomerase (tpi), beta-giardin (bg) and gdh loci detected assemblages A and B in humans and assemblage E in livestock. Cryptosporidium parvum was the only species identified in humans; C. andersoni, C. bovis, C. ryanae and C. ubiquitum were identified in cattle; C. xiaoi, C. ubiquitum and C. bovis in sheep; and C. xiaoi, C. baileyi and C. parvum in goats by typing at 18S rRNA locus. The C. parvum subtype IIcA5G3q, which has previously been identified in children in Ghana was identified in livestock by typing at gp60 locus.

This thesis also describes the identification of GIT helminths in farmers and their livestock, the first molecular characterisation of Trichostrongylus in humans and animals in Ghana and the identification of zoonotic as well as potentially novel species. Overall 21 farmers tested positive for at least one GIT helminth by formal ether concentration microscopy and/or PCR at the ITS-2 locus, 80.9% of which were single infections and 19.0% were co-infections. The parasites identified in the farmers consisted of hookworms (n=13) (9 were Necator americanus and the other 4 could not be amplified by PCR), Trichostrongylus spp. (n=9), Schistosoma mansoni (n=1), Schistosoma haematobium (n=1) and Diphyllobothrium latum (n=1). In livestock, Eimeria was dominant (78.4%) followed by strongylid nematodes (56.6%), Paramphistomum spp. (16.9%), Dicrocoelium spp. (7.1%), Thysaniezia spp. (5.8%), Trichuris spp. (3.3%), Moniezia spp. (3.1%), Fasciola spp. (2.8%), Toxocara spp. (1.1%) and Schistosoma spp. (0.2%) using microscopy. Genotyping of Trichostrongylus spp. in the farmer’s stools identified T. colubriformis (n=6), similar to T. colubriformis detected in cattle, sheep and goats in the present study. In addition, two Trichostrongylus spp. with 98.3% and 99.2% genetic similarity to T. probolurus respectively and one Trichostrongylus. spp. which showed 96.6% similarity to both T. probolurus and T. rugatus were identified and T. axei was identified in cattle, sheep and goats.

The distribution and risk factors associated with GIT parasite infection is also described in this thesis. Overall, 90.8% of the total livestock were infected by at least one of the ten different parasites (Eimeria, Strongylids, Toxocara, Trichuris, Schistosoma, Dicrocoelium, Paramphistomum, Fasciola, Moniezia and Thysaniezia). There was significant association between the prevalence of specific parasites and the animals’ age group, region, farming system, and housing floor type. The level of infection was generally light, however 99.0% of the 142 herds were infected. The risk factors significantly associated with specific GIT parasite infections in the livestock included region, type of housing floor, flock size, the number of ruminant species kept, infection with other GIT parasites and education.

In summary, the prevalence and species of GIT parasites in farmers and their ruminant livestock in the Coastal Savannah zone of Ghana is reported in this thesis. The zoonotic potential of the parasites detected are discussed and recommendations for effective control and further studies involving larger numbers of farmers and their household members have been made. The outcome of the present study is relevant for effective management and control of GIT parasites for both veterinary and public health in Ghana. Dedicated and co-ordinated commitments from African governments involving “One Health” initiatives with multidisciplinary teams of veterinarians, medical workers, relevant government authorities, animal health and public health specialists working together is necessary for effective control and prevention of the burden of disease caused by these GIT parasites.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
United Nations SDGs: Goal 12: Responsible Consumption and Production
Goal 15: Life on Land
Supervisor(s): Ryan, Una, Robertson, Ian and Yang, Rongchang
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