Investigating Central Nervous System Trypanosomosis in working equids in The Gambia

Kingston, Demelza (2018) Investigating Central Nervous System Trypanosomosis in working equids in The Gambia. PhD thesis, University of Glasgow.

Due to Embargo and/or Third Party Copyright restrictions, this thesis is not available in this service.

Abstract

Working equids, vital to many of the world’s most economically vulnerable people, face many challenges to their health, welfare and productivity. In The Gambia, West Africa, appropriate nutrition, husbandry and veterinary assistance are limited, while infectious disease is a constant threat, particularly the parasitic disease trypanosomosis. The prevalence of generalised trypanosomosis in working equids attending the Gambia Horse and Donkey Trust show in 2013 using PCR was 55.4%. Trypanosoma congolense was most prevalent (47.0%), followed by T. vivax (15.7%) and T. brucei s.l. (2.4%). Mixed infections were common (9.4%) and T. congolense/ T. vivax coinfection appeared to have the greatest clinical effect.
Spread of T. brucei parasites to the central nervous system (CNS), confirmed using immunohistochemistry and PCR, causes severe CNS dysfunction. Horses showed spastic paraparesis that rapidly progressed to recumbency, while donkeys more often displayed somnolence and cranial nerve dysfunction with a slower deterioration. The disease was fatal in all cases. Histopathology revealed diffuse lymphocytic-plasmacytic meningoencephalo-myelitis with marked perivascular cuffing, particularly in the white matter. T cells were prominent in this first study of lymphocyte distribution in equine CNS trypanosomosis. Extensive reactive astrocytosis was also demonstrated. Currently, a reliable diagnosis of equine CNS requires post mortem samples. The loop-mediated isothermal amplification (LAMP) assay was assessed for the diagnosis of equine T. brucei infection for the first time in both blood and cerebrospinal fluid (CSF).
An entomological survey showed that Glossina morsitans submorsitans was common in dry woodland areas while G. palpalis gambiensis was found in riverine habitats. The prevalence of T. brucei in the midguts of Glossina specimens was 1.7% and equine DNA was found in tsetse bloodmeals, providing evidence for ongoing interaction between host, parasite and vector. Atylotus agrestis, vector of T. vivax and T. congolense, was present in large numbers in village areas. Equine DNA was detected in one A. agrestis specimen, however, no evidence of T. brucei in association with these flies was found. Finally, microsatellite genotyping was used for the first time to investigate T. brucei populations in equine trypanosomosis in The Gambia. The results revealed a heterogenous population, providing further evidence for a tsetse-transmitted mode of transmission. No evidence of population clustering by disease type or host species was detected, suggesting that host factors determine pathogenesis.
Initial evidence for the involvement of the tsetse vector supports evaluation of vector control methods although further analysis of T. brucei populations in insect vectors and their relationships with those infecting equids is recommended. The clinicopathological descriptions will be of use in further study of equine CNS trypanosomosis and the development of new therapeutics and LAMP has the potential to facilitate research, especially in the study of CNS infection which has, up to now, relied on post mortem confirmation.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Due to confidentiality issues the electronic version of this thesis is not available for viewing. Access to the print version will be available after the embargo period expires.
Keywords: equine, horse, donkey, trypanosomosis, trypanosomiasis, parasitology, neurology, pathology, neuropathology, CNS, working equids, equidae, trypanosome, Trypanosoma, vivax, congolense, brucei, Gambia, tsetse, Glossina, Atylotus.
Subjects: Q Science > QH Natural history > QH301 Biology
Q Science > QH Natural history > QH426 Genetics
S Agriculture > SF Animal culture > SF600 Veterinary Medicine
Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
Supervisor's Name: Rodgers, Dr. Jean and Sutton, Dr. David
Date of Award: 2018
Embargo Date: 20 July 2019
Depositing User: Demelza Kingston
Unique ID: glathesis:2018-30682
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 20 Jul 2018 10:03
Last Modified: 24 Jul 2018 08:23
URI: http://theses.gla.ac.uk/id/eprint/30682
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