Epidemiology of Tropical Theileriosis in Nyala Dairy Farms in South Darfur State, Sudan

Abstract

The current study of epidemiology of bovine tropical theileriosis has been conducted in dairy farms in and around Nyala town, South Darfur. Cattle under different husbandry systems, different age groups, different types and sex were randomly selected. Ticks infesting cattle, blood smears, biopsy smears and serum samples were collected on a monthly basis for one year from June 2006 to May 2007. Cattle were mainly indigenous and cross (Friesian X indigenous) while the husbandry systems practiced were semi- intensive and extensive systems. Four age groups of cattle were selected, viz: group one < one year old, group two one year to < two years old, group three two years to three years old and group four older than three years. A total of 1200 blood smears and lymph node biopsy smears (780 samples from indigenous and 420 samples from Friesian cross bred cattle) were collected. The prevalence rate of Theileria spp. piroplasms was 43 (3.6%) in the Giemsa’s stained blood smears (BS). Using indirect fluorescent antibody (IFA) test, out of 100 serum samples, 31 samples (31%) were positive for T. annulata antibodies. Prevalence rate of Theileria spp. piroplasms and T. annulata antibodies were highest in December followed by November, and the lowest prevalence rate was in August followed by April. Although the disease occurred throughout the year, but it was significantly higher in winter followed by summer and the lowest rate was in autumn. The prevalence of the piroplasms among cross bred cattle was higher than xii indigenous cattle. However, the highest prevalence of antibodies against T. annulata was recorded among indigenous cattle. The highest prevalence Theileria spp. piroplasms 9 (5.1%) was recorded among calves 1 < 2 years old, and lowest prevalence 3 (2.4%) was recorded among calves aged < 1 year old. The highest prevalence of T. annulata antibodies, 20 (4.1%), was recorded among old cattle (> 3 years old) and the lowest, 2 (1.8%) was recorded among young calves (< 1 year old). There was a slightly high significant difference (P < 0.05) between the prevalence rate of piroplasms and antibodies in bulls and cows. Extensive management systems posed a greater risk than semi intensive systems and semi extensive systems. There were four genera and thirteen species of ticks found feeding on cattle. These included Amblyomma variegatum, A. lepidum, Boophilus annulatus, B. decoloratus, Hyalomma anatolicum anatolicum, H. anatolicum excavatum, H. dromedarii, H. impeltatum, H. impressum, H. marginatum rufipes, H. truncatum, Rhipicephalus evertsi evertsi, and R. s. sanguineus. High abundance of H. dromedarii, H. m. rufipes, H. truncatum, H. impeltatum was found and the probable role of these tick species in transmission of theileriosis is discussed with emphasis on H. dromedarii. It is strongly recommended not to introduce livestock from Central Sudan into South Darfur without applying strict tick control measures. At the same time, there must be planned programme of tick control in the farms where H. a. anatolicum was found for the purpose of eradicating this newly introduced tick species. Spread of this species to other farms, other towns and probably cross the international borders must be prevented.