Abstract
Buffalo-derived Theileria parva can ‘break through’ the immunity induced by the infection and treatment vaccination method (ITM) in cattle. However, no such ‘breakthroughs’ have been reported in northern Tanzania where there has been long and widespread ITM use in pastoralist cattle, and the Cape buffalo (Syncerus caffer) is also present. We studied the exposure of vaccinated and unvaccinated cattle in northern Tanzania to buffalo-derived T. parva using p67 gene polymorphisms and compared this to its distribution in vaccinated cattle exposed to buffalo-derived T. parva in central Kenya, where vaccine ‘breakthroughs’ have been reported. Additionally, we analysed the CD8+ T cell target antigen Tp2 for positive selection. Our results showed that 10% of the p67 sequences from Tanzanian cattle (n = 39) had a buffalo type p67 (allele 4), an allele that is rare among East African isolates studied so far. The percentage of buffalo-derived p67 alleles observed in Kenyan cattle comprised 19% of the parasites (n = 36), with two different p67 alleles (2 and 3) of presumptive buffalo origin. The Tp2 protein was generally conserved with only three Tp2 variants from Tanzania (n = 33) and five from Kenya (n = 40). Two Tanzanian Tp2 variants and two Kenyan Tp2 variants were identical to variants present in the trivalent Muguga vaccine. Tp2 evolutionary analysis did not show evidence for positive selection within previously mapped epitope coding sites. The p67 data indicates that some ITM-vaccinated cattle are protected against disease induced by a buffalo-derived T. parva challenge in northern Tanzania and suggests that the parasite genotype may represent one factor explaining this.
Highlights
Theileria parva is a tick-transmitted protozoan tick-borne haemo-pathogen which causes East Coast fever (ECF), a frequently lethal and economically important disease of cattle in Eastern, Central and Southern sub-Saharan Africa (Norval et al 1991)
The ability to grind up whole infected R. appendiculatus vector ticks and cryopreserve T. parva sporozoites that can be inoculated into cattle simultaneously treated with a longacting formulation of oxytetracyline was critical to the development of the infection and treatment method (ITM) of live vaccination (Cunningham et al 1973; Radley et al 1975)
The T. parva carrying the more heterogeneous p67 allele types 2–4 is known to originate from buffalo and has been shown to be associated with Corridor disease in livestock-wildlife interface areas, where cattle are exposed to infective ticks that have fed on infected African Cape buffalo (Mukolwe et al 2020; Obara et al 2015; Sibeko et al 2010; Sitt et al 2019)
Summary
Theileria parva is a tick-transmitted protozoan tick-borne haemo-pathogen which causes East Coast fever (ECF), a frequently lethal and economically important disease of cattle in Eastern, Central and Southern sub-Saharan Africa (Norval et al 1991). Exposure of cattle to buffalo-derived T. parva results in Corridor disease, a frequently lethal clinical syndrome characterised by low levels of schizonts, the parasite’s intra-lymphocytic stage and scanty piroplasm parasitaemia (Irvin and Mwamachi 1983; Jura and Losos 1980) These pathological features are distinct from ECF caused by T. parva that is transmissible between cattle by ticks, which tends to be associated with a high piroplasm parasitaemia. The T. parva carrying the more heterogeneous p67 allele types 2–4 is known to originate from buffalo and has been shown to be associated with Corridor disease in livestock-wildlife interface areas, where cattle are exposed to infective ticks that have fed on infected African Cape buffalo (Mukolwe et al 2020; Obara et al 2015; Sibeko et al 2010; Sitt et al 2019). We analysed blood samples from central Kenya obtained from clinically reacting cattle that exhibited the typical signs of Corridor disease in an ITM controlled trial (Bishop et al 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
