Dynamics and within-host interaction of Theileria lestoquardi and T. ovis among naive sheep in Oman.

Mixed species infections of Theileria spp. are common in nature. Experimental and epidemiological data suggest that mixed species infections elicit cross-immunity that can modulate pathogenicity and disease burden at the population level. The present study examined within-host interactions, over a period of 13 months during natural infections with two Theileria spp., pathogenic (T. lestoquardi) and non-pathogenic (T. ovis), amongst a cohort of naive sheep in Oman. In the first two months after exposure to infection, a high rate of mortality was seen among sheep infected with T. lestoquardi alone. However, subsequently mixed-infections of T. lestoquardi and T. ovis prevailed, and no further death occurred. The overall densities of both parasite species were significantly higher as single infection vs mixed infection and the higher relative density of pathogenic T. lestoquardi indicated a competitive advantage over T. ovis in mixed infection. The density of both species fluctuated significantly over time, with no difference in density between the very hot (May to August) and warm season (September to April). A high degree of genotype multiplicity was seen among T. lestoquardi infections, which increased with rising parasite density. Our results illustrate a potential competitive interaction between the two ovine Theileria spp., and a substantial reduction in the risk of mortality in mixed parasite infections, indicating that T. ovis confers heterologous protection against lethal T. lestoquardi infection.

Theileria lestoquardi in Sudan is highly diverse and genetically distinct from that in Oman.

Malignant ovine theileriosis is a severe tick-borne protozoan disease of sheep and other small ruminants which is widespread in sub-Saharan Africa and the Middle East. The disease is of considerable economic importance in Sudan as the export of livestock provides a major contribution to the gross domestic product of this country. Molecular surveys have demonstrated a high prevalence of sub-clinical infections of Theileria lestoquardi, the causative agent, among small ruminants. No information is currently available on the extent of genetic diversity and genetic exchange among parasites in different areas of the country. The present study used a panel of T. lestoquardi specific micro- and mini-satellite genetic markers to assess diversity of parasites in Sudan (Africa) and compared it to that of the parasite population in Oman (Asia). A moderate level of genetic diversity was observed among parasites in Sudan, similar to that previously documented among parasites in Oman. However, a higher level of mixed-genotype infection was identified in Sudanese animals compared to Omani animals, consistent with a higher rate of tick transmission. In addition, the T. lestoquardi genotypes detected in these two countries form genetically distinct groups. The results of this work highlight the need for analysis of T. lestoquardi populations in other endemic areas in the region to inform on novel approaches for controlling malignant theileriosis.

Prevalence and genetic diversity of Babesia and Anaplasma species in cattle in Sudan.

Disease prevalence studies are one of the most valuable tools to demonstrate the risk or impact of certain infections in local and global economies. The data obtained in these studies contribute to develop strategies for disease control. The present study aims to provide information about the prevalence of babesiosis and anaplasmosis in the northern regions of Sudan. Blood samples from four different states of Sudan were collected from apparently healthy cattle (n=692), DNA was extracted and the prevalence of Babesia and Anaplasma species was analyzed by PCR. The results confirmed the presence of Babesia bigemina, Babesia bovis and Anaplasma marginale in cattle in northern Sudan with overall prevalence rates of 4.0%, 1.9% and 6.1%, respectively. Statistical analysis revealed that the prevalence of B. bigemina, B. bovis and A. marginale varies significantly between Sudanese states as well as in different age groups, while gender seems not to have a significant effect on the prevalence of these pathogens among Sudanese cattle. The highest prevalence for B. bigemina was found in the Aljazirah State while the highest number of A. marginale positive samples was reported in River Nile.