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Theileria parva is a parasitic protozoan that causes East Coast fever (ECF), an economically important disease of cattle in eastern, central and southern Africa. In South Sudan, ECF is considered a major constraint for livestock development in regions where the disease is endemic. To obtain insights into the dynamics of T. parva in South Sudan, population genetic analysis was performed. Out of the 751 samples included in this study, 178 blood samples were positive for T. parva by species-specific PCR, were collected from cattle from four regions in South Sudan (Bor = 62; Juba = 45; Kajo keji = 41 and Yei = 30) were genotyped using 14 microsatellite markers spanning the four chromosomes. The T. parva Muguga strain was included in the study as a reference. Linkage disequilibrium was evident when populations from the four regions were treated as a single entity, but, when populations were analyzed separately, linkage disequilibrium was observed in Bor, Juba and Kajo keji. Juba region had a higher multiplicity of infection than the other three regions. Principal components analysis revealed a degree of sub-structure between isolates from each region, suggesting that populations are partially distinct, with genetic exchange and gene flow being limited between parasites in the four geographically separated populations studied. Panmixia was observed within individual populations. Overall T. parva population genetic analyses of four populations in South Sudan exhibited a low level of genetic exchange between the populations, but a high level of genetic diversity within each population., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

A cross-sectional survey was carried out in four counties of Jonglei State, South Sudan, between May and June 2012 to determine the distribution and northern limit of Theileria parva, the causative agent of East Coast fever in cattle, and its tick vector Rhipicephalus appendiculatus, as a prerequisite to the deployment of relevant control strategies. A total of 1636 ticks, 386 serum samples and 399 blood samples were collected from indigenous, apparently healthy, cattle of different age groups. Tick species were identified morphologically, and the identity of R. appendiculatus was confirmed by DNA barcoding. Overall, the T. parva infection rate in R. appendiculatus was 25% as shown by nested PCR. ELISA was used to assess antibodies to T. parva, and the overall seroprevalence was 22.8%. PCR of the blood samples showed 55 (13.8%) were positive for T. parva. This is the first molecular confirmation of T. parva DNA in areas north of Juba, where it was previously known and established. The northern limit of T. parva was determined as N⁰06.17.792, about 242 Km north from Juba. Implication of this limit on the epidemiology and control of ECF is discussed., (© 2016 Blackwell Verlag GmbH.)

East Coast fever (ECF), caused by Theileria parva infection, is a frequently fatal disease of cattle in eastern, central and southern Africa, and an emerging disease in South Sudan. Immunization using the infection and treatment method (ITM) is increasingly being used for control in countries affected by ECF, but not yet in South Sudan. It has been reported that CD8+ T-cell lymphocytes specific for parasitized cells play a central role in the immunity induced by ITM and a number of T. parva antigens recognized by parasite-specific CD8+ T-cells have been identified. In this study we determined the sequence diversity among two of these antigens, Tp1 and Tp2, which are under evaluation as candidates for inclusion in a sub-unit vaccine. T. parva samples (n = 81) obtained from cattle in four geographical regions of South Sudan were studied for sequence polymorphism in partial sequences of the Tp1 and Tp2 genes. Eight positions (1.97%) in Tp1 and 78 positions (15.48%) in Tp2 were shown to be polymorphic, giving rise to four and 14 antigen variants in Tp1 and Tp2, respectively. The overall nucleotide diversity in the Tp1 and Tp2 genes was π = 1.65% and π = 4.76%, respectively. The parasites were sampled from regions approximately 300 km apart, but there was limited evidence for genetic differentiation between populations. Analyses of the sequences revealed limited numbers of amino acid polymorphisms both overall and in residues within the mapped CD8+ T-cell epitopes. Although novel epitopes were identified in the samples from South Sudan, a large number of the samples harboured several epitopes in both antigens that were similar to those in the T. parva Muguga reference stock, which is a key component in the widely used live vaccine cocktail.

A cross-sectional survey was conducted in 2005 in different cattle camps in Juba, Mangalla and Terekeka localities of Central Equatoria State, South Sudan. Serum samples were collected from 514 cattle of different age groups. Samples were analysed using an indirect enzyme-linked immunosorbent assay (ELISA) with commercially available polymorphic immunodominant molecule (PIM) ELISA kits. The overall serological prevalence of Theileria parva was 70.8% (364/514). The highest rate of prevalence was observed in Mangalla (91.2%) and the lowest in Juba (61.8%), with Terekeka recording 71.8%. Regarding the age groups, older cattle (over four years of age) showed a significantly higher rate of prevalence (p>0.001) than calves (below one year of age). The implications of these results in the overall epidemiology of East Coast fever in South Sudan are discussed and possible recommendations for future implementation of disease control measures are outlined.

Ticks infesting cattle represent a serious problem for improvement of cattle productivity in South Sudan. There has been limited information on ticks and tick-borne diseases in southern Sudan. This study was initiated to update the current distribution of ticks infesting cattle in the Central Equatoria region of South Sudan. The surveys for the present study were conducted at various cattle camps in Juba, Mangalla and Terekeka between December 2004 and June 2005. A total of 2322 ticks were collected from the bodies of 88 randomly selected cattle. Ticks were preserved in 70% ethanol for later identification. Seven ixodid tick species were found to infest cattle in Juba whilst six species were recorded in Mangalla and only four species in Terekeka. Amblyomma variegatum was the most common and widely distributed species found on cattle across all the study locations. Amblyomma lepidum was not found during this study. Based on these findings, it would be advisable to preempt the situation and institute containment procedures before possible East Coast fever outbreaks occur.