Local environmental factors characterizing Rhipicephalus appendiculatus abundance in cattle grazed in permanent pastures in South Kivu province, Democratic Republic of the Congo

Rhipicephalus appendiculatus is a highly competent pathogen transmission tick species and the most economically important tick of cattle in sub-Saharan African countries. This study determined the abundance and seasonality of free-living ticks in different agro-ecological zones (AEZ) and identified factors that drive its abundance. The distribution and abundance of ticks were monitored by drag sampling the vegetation on 24 cattle pastures considering seven replicates at each site located in South Kivu in DRC. The generalized linear models were used to model R. appendiculatus abundance. The identified species of ticks were Rhipicephalus appendiculatus, Rhipicephalus decoloratus, and Amblyomma variegatum. R. appendiculatus was the most abundant species with a relative abundance of 93.83% and a relative prevalence of 87.5% on pasturelands. Nymph burden per 25m2 was 9.9±10.4, 4.1±3.8 and 4.3±4.8, while average adult burden per 25m2 was 1.2±2.0, 0.4±0.8 and 2.4±2.7, respectively in highland, lowland, and upland zones. Tick abundance varied significantly with the method of farming (p<0.001): free-range pastures increased the expected number of nymphs and adults (β=2.279±0.353 and β=2.014±0.542, respectively) in comparison to fenced pastures. The wet season was more favourable to nymph abundance (β=1.312±0.360; p<0.001) while the annual mean temperature (β=-0.006±0.003; p<0.05) influenced negatively abundance of nymphs. There was no significant difference between the abundance of nymphs in the different AEZ while adult abundance varied significantly. Upland and highland zones recorded more adults in comparison to lowland zone. There is a need to quantify the contribution of R. appendiculatus species in local dynamic of zoonotic diseases and tick-borne disease control programmes must take into account local pasture management and microclimate. Keywords: Cattle, Congo, pastures, Rhipicephalus appendiculatus