Publikationsdatenbank

Delimiting Theileria parva strain diversity towards targeted and unified approaches in the control of T. parva cattle infections (2021)

Art

Hochschulschrift

Autor

Mwamuye, Micky Mwananje (WE 13)

Quelle

Berlin: Mensch & Buch Verlag, 2021 — 123 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/31746

Kontakt

Institut für Parasitologie und Tropenveterinärmedizin

Robert-von-Ostertag-Str. 7-13
14163 Berlin
+49 30 838 62310
parasitologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

The fatality of the tick-transmitted Theileria parva infections in cattle heavily impacts farmers in sub-Saharan Africa who depend on livestock for subsistence. Infection prevention by tick control relying on acaricides is expensive and unsustainable, while cattle vaccination by the “infection and treatment” is marred by ‘breakthrough’ infections in some areas within eastern Africa - where cattle share pasture grazing lands with wild Cape buffaloes. While it is known that buffalo-maintained parasites are diversely heterogeneous than cattle-maintained parasites, there is still a scarcity of parasite genotype data from wildlife-livestock interface areas. Moreover, a definitive genetic basis for differentiating cattle- and buffalo-derived parasites from such co-grazed areas is yet forthcoming. In addressing the two foregoing aspects, this thesis describes studies in which parasite genotypes based on the T. parva sporozoite surface antigen (p67) and the CD8+ antigen Tp2 genes were compared between Tanzanian and Kenyan wildlife-livestock interface areas. In addition, heterogeneity patterns of thirteen full-length near-complete T. parva mitogenomes from East and Southern Africa T. parva strains were examined. In the first set of analyses, T. parva-parasites antigen genes amplified from buffaloes, vaccinated and unvaccinated cattle from wildlife-livestock areas of northern Tanzania where vaccine ‘breakthrough’ have not been reported – despite the presence of Cape buffaloes, were compared against parasites in vaccinated cattle exposed to buffalo-derived T. parva challenge in central Kenya – where vaccine ‘breakthroughs’ have been reported. The analysis revealed additional epitope variants within the Tp2 antigen genes amplified from Tanzanian buffaloes, which adds to the evidence of parasite heterogeneity within the buffalo population. Moreover, a buffalo type p67 (allele 4), an allele reported in South Africa but is rare among East African isolates studied thus far, was identified in Tanzania, while p67 alleles (2 and 3) that are presumptive buffalo origin were observed in Kenyan cattle. In the second set of analyses, the heterogeneity patterns in 13 near-complete mitogenomes revealed seven haplotypes defined by nine SNPs that were initially parsimonious among transforming Theileria; T. parva, T. annulata, T. taurotragi, and T. lestoquardi mitogenomes, with the latter two sequenced in this study for the first time. All nine SNPs were synonymous except for two that cause amino acid substitutions within the cytochrome b gene of buffaloderived strains. Notably, the buffalo‐derived T. parva strains were clustered under one haplotype defined by the same nine SNPs. Further phylogenetic analyses were congruent with nuclear-encoded genes, which rules out possibilities of mitochondria specific inheritance patterns in the analysis. Although preliminary, the totality of the findings in the p67 and Tp2 analyses suggests that whereas the live vaccine can protect against buffalo-derived T. parva, this may be dependent, among other factors, on the parasite infecting genotype. Thus, it is emphasized that a further understanding of T. parva strains diversity and its field population dynamics is key to targeted control of East Coast Fever (ECF) and the related T. parva infections. As such, the identified T. parva mitochondrial haplotypes from this study will be insightful in understanding T. parva epidemiology with important implications for control, prediction of target populations for vaccination, and characterization of breakthrough infections by buffalo T. parva in ITM vaccinated cattle.