Factors influencing the distribution of questing ticks and the prevalence estimation of T. parva infection in brown ear ticks in the Tanga region, Tanzania.

Questing ticks from various districts and agro-ecological zones (AEZ) in the Tanga Region of Tanzania were studied for a two-year period between September 1999 and July 2001. Collections of both nymphal and adult ticks occurred at 29 sites using a blanket or white cloth dragging technique. The species recorded in the order of decreasing abundance were Rhipicephalus appendiculatus, Boophilus spp., and Ambylomma variegatum. Rhipicephalus appendiculatus field infestation levels varied across administrative districts and seasons, with Amani and the cool-to-dry season having lower tick counts ( = -2.09, SE = 0.71, P < 0.001 and = -1.54, SE = 0.56, P = 0.006 for Amani and cool to dry season, respectively). Based on the polymerase chain reaction technique, Theileria parva infection prevalence in adult R. appendiculatus was estimated to be 2.6%. Implications of these findings in light of the spatial and temporal distribution of ticks are discussed for the accurate diagnosis of multiple tick-borne diseases, the infected vector tick, the endemic status of T. parva in the region, and the implemention of control strategies.

Breed-associated resistance to tick infestation in Bos indicus and their crosses with Bos taurus.

The relative resistance to tick infestation of zebu (Bos indicus) in comparison to crossbred (B. indicus x B. taurus) cattle was investigated. B. indicus breeds, all belonging to Tanganyika shorthorn zebu were Meru, Mbullu and Iringa red. Crossbreds were Meru x Friesian and Iringa red x Friesian. Parameters to distinguish between 'tick resistant' and 'tick susceptible' cattle were tick counts on naturally exposed animals, serum complement levels and delayed skin hypersensitivity response to phytohaemagglutinin. Results have shown that pure zebu cattle are less infested with ticks when compared to zebu-taurine crosses under identical field conditions. Zebu cattle also had significantly higher serum complement level than crossbred cattle. While serum complement and tick burden were negatively associated (r = -0.27, P < 0.001), the cutaneous response to phytohaemagglutinin did not vary with tick infestation. The influence of cattle breed on tick infestation and serum complement level is demonstrated.