Seroprevalence and risk factors of brucellosis, chlamydiosis and ehrlichiosis in goats at different wildlife/livestock interface areas in the south-eastern lowveld of Zimbabwe.

Abstract

Brucellosis and chlamydiosis (zoonotic) are major causes of abortion, still birth, low herd fertility and other reproductive losses in goats in many countries world-wide and ehrlichiosis (heartwater) is also a major threat to livestock, including goat production in sub-Saharan Africa. Three study sites were selected in the south-east lowveld of Zimbabwe; a porous interface site where a direct wildlife/livestock interaction exists, a non-porous interface with no direct wildlife/livestock interaction and a non-interface area where there is little/no chance of wildlife/livestock interaction. Collected goat sera were tested for Brucella spp, Chlamydia abortus and Ehrlichiaruminantium antibodies using the Rose Bengal plate test (RBPT) and the complement fixation (CFT), the CFT and the Major Antigenic Protein (MAP-1B) ELISA tests, respectively. All goats tested (n=563) were negative for Brucella antibodies. Overall, chlamydial seroprevalence was 22% (n=563) while that of ehrlichiosis was 94% (n=450). The prevalence of tick-infestation was 73.3% (n=450). The porous [χ2=9.6, odds ratio (OR) =2.6, p=0.002)] and non-porous (χ2=37.5, OR=5.8, p<0.00001) interfaces were significantly associated with increased chlamydial seropositivity than the non-interface area. In contrast, tick infestation prevalence and ehrlichiosis seroprevalence were not significantly associated (p>0.05) with proximity to wildlife. Female (χ2=49.6, OR=13.6, p<0.0001) and tick-infested (χ2=35.9, OR=8.7, p<0.00001) goats were significantly associated with an increased ehrlichiosis seropositivity compared to their counterparts. Chlamydial seroprevalence was independent of sex (χ2=0.5, OR=1.2, p=0.5), abortion history in female goats (χ2=0.7, OR=1.3, p=0.4), keeping goats with cattle (χ2=0.2, OR=1.5, p=0.7) and flock size (χ2=0.03, OR=1.4, p=0.9). Season was also not associated (p>0.05) with tick-infestation prevalence and ehrlichiosis seroprevalence. The null hypothesis was true with regard to brucellosis and partly true with regards to seroprevalence of chlamydiosis and ehrlichiosis.