Longitudinal study of small ruminant zoonoses in Tana River, Kenya

Objectives
Bacterial infections are the leading causes of non-malarial fevers in Africa. Brucellosis, leptospirosis,
and Q fever are priority zoonoses in Kenya, but little information on their epidemiology is available to
date. Therefore, we implemented this longitudinal study by following up 316 small ruminants on
September, November, and December 2014, and January, March, and June 2015.
Materials and methods
Sampling was done in pastoral, irrigated, and riverine settings in Tana River County. We aimed at
estimating the disease burden, disease frequency, and associated risk factors for both exposure and
seroconversion. We tested for: (i) Coxiella burnetii using an IgG ELISA, (ii) Leptospira spp. using the
microscopic agglutination test, and (iii) Brucella spp. using the complement fixation test. We further
tested seropositive animals by real-time PCR.
Results
The overall seroprevalence estimates were highest for Coxiella burnetii (20.89%, 95% confidence
interval [CI]: 16.54-25.79), followed by those of Leptospira spp. (15.97%, 95% CI: 12.09-20.51) and
Brucella spp. (1.27%, 95% CI: 0.35-3.21). Despite this, we observed more seroconversions for
Leptospira spp. (27) than Coxiella burnetii (10) and Brucella spp. (0). Analysis of the risk factors and
incidence rate estimations are still ongoing. Three animals were positive by PCR for Brucella spp.
either consistently or intermittently for almost the entire study period, demonstrating the possibility of
prolonged periods of transmission. One animal was also PCR-positive for C. burnetii, but we
detected no pathogenic leptospires. The most prevalent leptospiral serovar was Ballum, but
evidence of paradoxical reactions was seen. Therefore, infective serovars in the area should be
proven by isolation of leptospires.
Conclusions
The high number of seroconverting animals in the study area shows the need for surveillance and
control measures to reduce animal disease burden and possible human exposure.