Abstract
BackgroundTheileriosis, caused by Theileria parva, is an economically important disease in Africa. It is a major constraint to the development of the livestock industry in some parts of eastern, central and southern Africa. In Zambia, theileriosis causes losses of up to 10,000 cattle annually.MethodsCattle blood samples were collected for genetic analysis of Theileria parva from Isoka and Petauke districts in Zambia. Microsatellite analysis was then performed on all Theileria parva positive samples for PCR using a panel of 9 microsatellite markers. Microsatellite data was analyzed using microsatellite toolkit, GenAlEx ver. 6, Fstat ver. 2.9.3.2, and LIAN computer softwares.ResultsThe combined percentage of positive samples in both districts determined by PCR using the p104 gene primers was 54.9% (95% CI: 46.7 – 63.1%, 78/142), while in each district, it was 44.8% (95% CI: 34.8 – 54.8%) and 76.1% (95% CI = 63.9 – 88.4%) for Isoka and Petauke districts, respectively. We analyzed the population genetic structure of Theileria parva from a total of 61 samples (33 from Isoka and 28 from Petauke) using a panel of 9 microsatellite markers encompassing the 4 chromosomes of Theileria parva. Wright’s F index (FST = 0.178) showed significant differentiation between the Isoka and Petauke populations. Linkage disequilibrium was observed when populations from both districts were treated as a single population. When analyzed separately, linkage disequilibrium was observed in Kanyelele and Kalembe areas in Isoka district, Isoka district overall and in Petauke district. Petauke district had a higher multiplicity of infection than Isoka district.ConclusionPopulation genetic analyses of Theileria parva from Isoka and Petauke districts showed a low level of genotype exchange between the districts, but a high level of genetic diversity within each district population, implying genetic and geographic sub-structuring between the districts. The sub-structuring observed, along with the lack of panmixia in the populations, could have been due to low transmission levels at the time of sampling. However, the Isoka population was less diverse than the Petauke population.
Highlights
Theileriosis, caused by Theileria parva, is an economically important disease in Africa
PCR screening The screening of cattle blood samples (n=142) using the p104 gene primers showed a combined T. parva positive percentage of 54.9% from both districts
There are several potential short comings of selecting predominant alleles from mixed populations to form an multi-locus genotype (MLG): (i) each particular marker does not always amplify the predominant allele from all strains (ii) the same strain is not always amplified by a particular marker in all the samples, (iii) target regions in different strains that have the highest sequence homology with markers are amplified whether they are representative of the predominant strain or not and (iv) all markers in the selected panel of markers most likely do not amplify the same strain in different samples
Summary
Theileriosis, caused by Theileria parva, is an economically important disease in Africa. It is a major constraint to the development of the livestock industry in some parts of eastern, central and southern Africa. Theileriosis is an economically important disease of cattle in eastern, central and southern Africa. Theileriosis causes high levels of mortality in taurine breeds [5] and both high morbidity and mortality in indigenous 1–6 month old calves (Bos indicus). The high level of mortality in taurine breeds impedes the introduction of highly productive exotic breeds in endemic areas, further preventing the improvement of cattle production in the affected areas. Theileriosis is a major constraint to the development of the livestock industry in the eastern, central and southern parts of Africa
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