Sero-prevalence of Coxiella burnetii infection in sheep and goats and associated factors in Baringo County, Kenya

Abstract

Q fever is a highly endemic, globally distributed zoonosis caused by Coxiella burnetii. The pathogen host rage is varied although domestic small ruminants are the frequent source of human infection. The disease is associated with outbreaks of significant public and animal health importance but epidemiological data in subSaharan Africa is largely scarce with little attention to control and prevention strategies. The aim of this thesis was to determine the seroprevalence and factors associated with C. burnetii infection in small ruminants both at herd and animal level in Baringo County, Kenya, a region where acute cases of Q fever in humans have previously been reported. Data were collected from 140 randomly selected households. From the 140 household herds, 508 goats and 332 sheep were randomly selected for blood sample collection and the serum analyzed using an indirect ELISA assay for C. burnetii IgG antibodies. In addition, epidemiological information at both herd and individual animal level was collected using an animal level factor data collection tool and a household questionnaire. At individual animal level, the tool captured animal characteristics such as age, sex, species, breed, and production system while at household/herd level; the questionnaire captured household demographics, husbandry practices and farmer practices. Statistical analysis was done both at animal level and herd level. Multivariable logistic regression model was used to evaluate the relationship between C. burnetii seropositivity and animaland herd level factors. A mixed effect multivariable model using household herd as a random effect was used to adjust the data for possible clustering with C. burnetii seropositivity. The overall small ruminant seroprevalence was 20.5%. Seroprevalence was significantly higher in goats than in sheep (26.0% versus 12.2%, p = <0.001). Of the 140 households enrolled, 92 (66% 95% CI: 57.6 -73.2) had atleast one animal seropositive. At animal level, production system (nomadic pastoralism) and animal age (old versus young) were significantly associated with positive serological result (p = <0.05). Heterogeneity in C. burnetii seropositivity was observed across the sub locations (p =0.028). At herd/household level, households practicing nomadic pastoralism were more likely to be C. burnetii seropositive compared to those practicing non-nomadic pastoralism production systems (OR= 7.6, 95% CI: 2.3-34.1), p = 0.0023. Of the 140 humans interviewed, 120 (86%) reported to have assisted animals giving birth, 115 (82%) assisted in removal of retained placenta and 78% (n=109) had contact with aborted fetuses. Only 4 (3%) reported to have used PPEs during contact with animals. Coxiella burnetii exposure in sheep and goats and associated factors were demonstrated. Integrated animal-human surveillance and socio-economic studies are required for C. burnetii, to aid on the understanding of the risk of transmission between the animals and humans, and in the design of prevention and control strategies for the disease in the region.