The seroprevalence and risk factors of contagious bovine pleuropneumonia in the Northwestern area of Turkana District, Kenya i
Maritim, W K
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Contagious bovine pleuropneumonia (CBPP) is a severe respiratory disease affecting cattle. The study was carried out to determine the seroprevalence and risk factors associated with the disease in North-western Turkana, Kenya. The objectives of the study were; 1) to estimate the seroprevalence of CBPP in North-western Turkana District; 2) to determine the risk factors of CBPP in North-western Turkana District; 3) to map CBPP in North-western Turkana District; and 4) to use the information from (1) and (2) to recommend sound CBPP control strategies and mitigation measures in North-western Turkana District. A list of all livestock-grazing units (adakaars) in North-western Turkana was obtained through the assistance of the local administration. The study area was stratified into three regions and two adakaars per region were purposively selected based on logistics, accessibility and security considerations. Cattle were bled for purposes of determining their CBPP sero-status. A total of 270 cattle were sampled. The locations of all the selected adakaars were geo-referenced using global positioning system (GPS). Data on aspects of cattle management including grazing patterns, watering points, disease outbreaks, kraaling, treatments, cattle acquisition, cattle movements, herd size and structure (age, sex), herd composition and vaccination, were sought through the administration of a questionnaire to the herders via personal interviews. Six adakaars, . namely, Ekipor, Erukudi, Ngibelianga, Ngikachipchipi, Ngilibatom, and Apamulele were involved in the study. All the respondents (30 herders) in the study cooperated in the questionnaire interview, leading to a 100% response rate. The collected serum (270 samples) was subjected to the Complement Fixation Test (CFT) and the competitive ELISA (c-ELISA) for the detection of antibodies to mycoplasma at the Kenya Agricultural Research Institute (KARl), Muguga, Kenya. The mean herd size was 61.4, and was not significantly different across the adakaars The herd sizes were highest in Ekipor and lowest in Erukudi. Cattle were taken to various places for grazing. Of the 30 herders interviewed, 10 took their animals to Mogilla ranges (Kenya), 10 to Oropoi (bordering Uganda), and 10 to Soya neighbouring Republic of Ethiopia. Ten percent (10%; 3/30) had not been raided. There was a significant association between having been raided before and where cattle were taken for grazing (p=0.04). During the night, cattle were kept at the kraals (67%; 20/30) and in open places (33%; 10/30). Cattle owners reportedly had their animals treated by; Veterinary staff (13%; 4/30), owners themselves (80%; 24/30), and others (traditional healers) (7%; 2/30). A high proportion (73%; 22/30) of the herders had reportedly seen respiratory problems in their herds. The herders perceived the infections as arising from watering points (37%) and grazing areas (63%). A vast majority (77%) of herds with previous respiratory problems were kept in kraals at night. Blood samples collected were analyzed using c-ELISA and Complement Fixation Test (CFT). A total of 270 samples were subjected to both tests. In each of the adakaars, 45 animals were sampled. Of the 270 cattle serum samples tested using the Complement Fixation Text (CFT), 39 tested positive for CBPP antibodies for prevalence rate of 14 % (9.9% ,18%; 95% CI). The prevalence ranged from 4% (2/45) in Ekipor and Ngikachipchipi adakaars to 38% (17/45) Erukudi adakaar. The prevalence of CBPP antibodies based on c-ELISA was 17% (46/270; 12.5%,21.5%; 95% CI). The prevalence ranged from 0% in Ngikachipchipi adakaar to 49% in Erukudi adakaar. This prevalence (17%) was not statistically different from the one obtained (14%) using the CFT. Prevalence of CBPP in the two stratified grazing regions, Mogillal7.8 % (9.9, 25.7; 95%) and Soya 12.2 %( 5.4, 19.0; 95%), was not statistically different. However, the prevalence of CBPP in Oropoi 38.9 %( 28.8, 49.0; 95%) was statistically different from that of the other two regions. The prevalence of CBPP antibodies in five adakaars (Ekipor 8.9%, Ngibelianga 26.7%, Ngikachipchipi 4%, Apamulele 22.2% and Ngilibatom 20%) was not statistically different while that of Erukudi 55.6% was statistically different. In an attempt to increase the sensitivity of the testing regime, parallel interpretation of the results of the two tests was done. In this interpretation, an animal was considered positive if it tested positive to either of the two tests. A total of 62 samples were positive for either of the tests, giving an overall CBPP prevalence of 23 %( 62/270). A Kappa statistic of 0.48 (0.42, 0.54; 95% CI) was obtained indicating a moderate agreement between the two tests, CFT and c-ELISA. Associations between the various variables considered in this study were done using l statistics and their strengths determined using odds ratio (OR). The univariate analysis was based on the questionnaire responses about presence of respiratory diseases. Variables significant at the 95% level of confidence were included in the logistic regression. These were respiratory problems, source of disease, treatment, grazing area, adakaar, dry season, and wet season. The results showed that a herd which had experienced respiratory problems is two times more likely to be seropositive than those negative (OR=2.208, P=0.026). Cattle grazing at Oropoi were three times more likely to be CBPP sero-positive (OR=2.943, P=O.OOl) whereas if they graze at Soya they were two times less likely to be CBPP sero-positive (OR= 0.644, P= 0.001). Cattle kept by herders in Erukudi adakaar were four times more likely to be affected by CBPP disease (OR= 4.375, P = 0.001) but if kept at Ngikachipchip adakaar they were six times less likely to be affected by the disease (OR= 0.1628, P = 0.001). Keeping cattle in Oropoi Division was five times more likely to contract CBPP disease than when they were kept in Lokichoggio or Lapur (OR= 4.570, P = 0.001). On subjecting the significant variables to multiple logistic regression, only treatment and grazing area were significant in the forward fitting logistic modelling, with p<O.OS. Whether one had encountered respiratory problems in his herd was a potential confounder since it was explaining the same variable with treatment. Most herders tend to treat (mostly using oxytetracyclines) their herds whenever they observe respiratory problem in their cattle. Source of disease, adakaar, distance travelled in dry season and distance travelled in wet season were potential confounders as they are strongly associated with grazing area. In conclusion, CBPP was found to be a major constraint III North-western Turkana. Erukudi adakaar in Oropoi region had the highest seroprevalence for CBPP. Livestock owners were also aware that absence of clinical cases does not mean there was no CBPP and reported that the source of infection in clinical cases that developed after a period was from within their own herds. Grazing area and treatment were considered to be the main risk factors.