Coxiella burnetii seroprevalence in small ruminants in The Gambia

Abstract

Background: In The Gambia over-diagnosis of clinical malaria might be present, while treatable bacterial diseases are likely to be missed. These treatable bacterial diseases are often emerging or neglected zoonoses, such as Q fever. Q fever is a zoonosis caused by Coxiella burnetii, a gram negative bacterium present worldwide. Epidemiologically, the massive shedding of the bacterium during abortions due to a C. burnetii infection makes sheep and goats the main reservoirs responsible for infection of humans. As such, the objectives for this study were two-fold; firstly to estimate the extent of the problem of C. burnetii infection among small ruminants in The Gambia and secondly to compare this with the findings from a pilot serological study among children.

Methodology/Principal Findings: This survey was carried out from March to May 2012 at two areas comprising different sites in The Gambia. The first area comprised a cluster of seven rural villages (Alkali Kunda, Jarjary, India, Yallal, Daru Yallal, Jumansareba and Conteh Kunda Nicci) situated 5-15 km west of Farafenni as well as the local Farafenni abattoir. A second sampling was done at the central abattoir in Abuko (30 km from the capital, Banjul) in the Western Region. Serum samples were obtained from 490 goats and 398 sheep. In addition, 67 milk samples were obtained from lactating dams in the villages only. Sera were tested with a Q fever ELISA kit. DNA was extracted from the milk using the NucliSens easyMag extractor. C. burnetii DNA was then detected using a specific quantitative multiplex PCR assay, targeting the transposase gen IS1111. A multivariable mixed logistic regression model was used to examine the relationship between seropositivity and explanatory variables ‘species’, ‘breed’, ‘sex’, ‘age’ and ‘location’. A overall seroprevalence of 21,6% was found. Goats had a significantly higher seroprevalence as compared to sheep, respectively 24,2% and 18,5%. Seropositive animals were significantly older than seronegative animals. Animals from the villages had a significantly lower seroprevalence than animals from the central abattoir (15,1% versus 29,1%). C. burnetii DNA was detected in 2 out of 67 milk samples, whereas 8 samples gave a doubtful result. No significant linear relationship was found between the human and animal seroprevalences in the seven villages.

Conclusion/Significance: This is the first serological survey of C. burnetii seroprevalence in small ruminants in The Gambia. It demonstrates a relatively high prevalence of current or past infection in the sheep and goat population. Although a direct link between the human and veterinary data could not be demonstrated, there are clear zoönotic implications. As such, further research on Q fever and other causative bacterial agents in The Gambia and other West African countries is needed.