Abstract
Theileria annulata, which causes tropical theileriosis, is a major impediment to improving cattle production in Sudan. Tropical theileriosis disease is prevalent in the north and central regions of Sudan. Outbreaks of the disease have been observed outside the known endemic areas, in east and west regions of the country, due to changes in tick vector distribution and animal movement. A live schizont attenuated vaccination based on tissue culture technology has been developed to control the disease. The parasite in the field as well as the vaccine strain need to be genotyped before the vaccinations are practiced, in order to be able to monitor any breakthrough or breakdown, if any, after the deployment of the vaccine in the field. Nine microsatellite markers were used to genotype 246 field samples positive for T. annulata DNA and the vaccine strain. North and central populations have a higher multiplicity of infection than east and west populations. The examination of principal components showed two sub-structures with a mix of all four populations in both clusters and the vaccine strain used being aligned with left-lower cluster. Only the north population was in linkage equilibrium, while the other populations were in linkage disequilibrium, and linkage equilibrium was found when all samples were regarded as single population. The genetic identity of the vaccine and field samples was 0.62 with the north population and 0.39 with west population. Overall, genetic investigations of four T. annulata populations in Sudan revealed substantial intermixing, with only two groups exhibiting regional origin independence. In the four geographically distant regions analyzed, there was a high level of genetic variation within each population. The findings show that the live schizont attenuated vaccine, Atbara strain may be acceptable for use in all Sudanese regions where tropical theileriosis occurs.
Highlights
Tropical theileriosis is a tick-borne disease, caused by Theileria annulata that continues to be a major concern for livestock in tropical countries affecting millions of animals, crossbreed and exotic cattle, and resulting in significant economic loss and mortality (Dolan, 1989)
The polymorphic information content (PIC) of marker TS8 had the highest (0.87), whereas TS9 had the lowest (0.36) (Table 2). This finding argued in favor that these markers could be effective in determining linkage disequilibrium analysis in T. annulata populations
This study investigated the diversity and population structure of T. annulata in Sudan
Summary
Tropical theileriosis is a tick-borne disease, caused by Theileria annulata that continues to be a major concern for livestock in tropical countries affecting millions of animals, crossbreed and exotic cattle, and resulting in significant economic loss and mortality (Dolan, 1989). Many countries, including, Israel (Pipano et al, 1981), Iran (Hashemi-Fesharki, 1988), Russia (Stepanova and Zablotskii, 1989), India (Beniwal et al, 1997), China (Zhang, 1997), Turkey (Sayin et al, 1997), Spain (Viseras et al, 1997), Morocco (Ouhelli et al, 1997), Tunisia (Darghouth, 2008), and India (Roy et al, 2019), have employed the attenuated schizont vaccines to control T. annulata infection. T. annulata from other endemic regions, such as China, Oman, Turkey, Tunisia, and Portugal have all been researched utilizing a multilocus genotyping technique for assessing genetic diversity, population structure, and transmission patterns (Weir et al, 2007, 2011; AlHamidhi et al, 2015; Gomes et al, 2016; Yin et al, 2018; Roy et al, 2021). T. annulata genetic populations studies were notable for its genetic variation, the availability of many genotypes per sample, and sub-structuring by geography (Weir et al, 2007, 2011; Al-Hamidhi et al, 2015; Gomes et al, 2016; Yin et al, 2018; Roy et al, 2019)
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