Prevalence And Factors Associated With Brucellosis In Livestock In Baringo County, Kenya

Abstract

Brucellosis is an important zoonotic disease occurring worldwide. Its importance stems from both public health and economic effects of the disease. The prevalence of brucellosis in livestock from pastoralist herds is usually higher than in settled herds, with human brucellosis highly relating to the disease in animals. This cross sectional study was carried out in four sub-counties of Baringo County, in which farms were randomly selected from each sub-county. Blood (10ml) from selected cattle (n= 250), sheep (n= 142) and goats (n= 166) was collected in sterile plain vacutainers. Bulk raw cattle milk (n=83) was also collected. All serum samples were screened for Brucella antibodies using Rose Bengal Plate test (RBPT) and by competitive Enzyme Linked Immunosorbent Assay (cELISA). Brucella antibodies in milk were assayed using Milk Ring Test (MRT). Polymerase chain reaction (PCR) was carried out on blood clots from all RBPT-positive serum samples as well as on blood clots of 7% of the serum samples that turned negative on RBPT to determine presence of brucella antigens in those samples. Twenty three (9.2%) of the 250 cattle serum samples reacted positive to RBPT while 17 (6.8%) reacted positive to cELISA with cumulative reactors of 25 (10%). The 166 caprine serum samples had 17 (10.2%) positive reactors to RBPT and 11 (6.6%) by cELISA. Cumulative caprine reactors were 18 (10.8%). Positive ovine serum samples were 10 (7%) and 7 (4.9%) on RBPT and cELISA respectively, yielding positive cumulative reactors of 11 (7.7%). The sensitivity and specificity of RBPT was 88.6% and 96.4% respectively with a predictive value positive of 62% and predictive value negative of 99%. From the 83 milk samples collected, 9 (10.7%) tested positive to Milk Ring Test. xv Brucella abortus DNA was extracted from 11 of cattle blood clots and from two goat and one sheep blood clots respectively. Brucella melitensis DNA was extracted from one goat blood clot. Mixed farming was reported by 57% of the respondents, communal grazing reported by 32% of the respondents, use of communal watering points reported by 38% of the interviewees and allowing of animals to calve down on pasture reported by 91% of the respondents. All these were found to be factors associated with brucellosis in the region. However, introduction of a new animal reported by 42% was found not to be a risk factor despite studies elsewhere documenting it as a risk factor. From the serological results, it is evident that brucellosis occurs in livestock in Baringo, predominantly caused by B. abortus. This study also established that there is a huge knowledge gap on its risk factors in the region. It is therefore important to establish an educational campaign in the region on the significance of the disease, and establish possible control measures. This will lower the prevalence of the disease in animals and will go a long way towards minimizing human brucellosis.