Persistence and diversity of Theileria parva in East Coast fever vaccinated and unvaccinated cattle

Abstract

Infection and Treatment Method (ITM) has been practiced in Tanzania for over 20 years now as a prevention method against East Coast Fever (ECF). However, there is less information regarding the persistence of the Theileria parva parasites after a long-time lapse after vaccination. Likewise, the implication of the potential exchange of genetic information is largely unknown as regards ECF vaccination outcomes. A total number of 336 cattle samples were collected from Loiborsoit, Emboret, Esilalei, Manyara ranch, Mswakini, Tanga Mruazi farm and Tanga Leila farm in March of 2018. Samples were then screened for Theileria parva using nested PCR and the overall prevalence of carrier state was 34.5%, with a significant higher prevalence among the vaccinated cattle group 43% (103/239) compared to the unvaccinated group 13.4% (13/97) (p<0.000). Similarly, higher prevalence emerged among the cattle grazing close to the wildlife 38.2% (107/280) compared to the ones grazing far from wildlife 16.1% (9/56) p<0.001. The carrier state persisted up to 132 months post vaccination. Minisatellite 7 (MS 7), microsatellite 2 and 5 (ms 2, ms 5) markers were used to characterize genetic diversity. Whereby parasite diversity across cattle groups was determined by the mean number of alleles, and expected heterozygosity. Manyara ranch had the highest parasite diversity with all the markers. This study concludes that vaccination against ECF and the wildlife interface has an influence on the diversity of Theileria parva parasites, as the highest number of alleles and parasite diversity were shown in the vaccinated cattle and the ones in close proximity to wildlife interface.