Coxiella burnetii in Tunisian dromedary camels (Camelus dromedarius): Seroprevalence, associated risk factors and seasonal dynamics

Q fever, caused by Coxiella burnetii, is a zoonotic disease responsible of abortion in ruminants. Few studies have investigated the prevalence of this infection in camels (Camelus dromedarius). The present report aimed to highlight the epidemiological status and identify the risk factors associated with C. burnetii infection in one humped dromedary that is the most productive livestock species in arid areas. A total of 534 sera of healthy camels were collected in eight governorates from southern and central Tunisia. Samples were tested by an indirect Enzyme linked Immunosorbent Assay (ELISA). Results were analyzed using the Chi-square test and logistic regression. Overall, 237 camels (44%, 95%CI: 0.40-0.49) were seropositive to C. burnetii. Statistical analysis pointed out four potential risk factors associated with infection. A meaningful high seropositivity was observed in female camels with a previous history of abortion (70%) (OR = 4.186, 95%CI: 2.05-8.51). Seroprevalence was higher in aged camels ( > 10 years-old) (48%) (OR = 2.91, 95%CI: 1.37-6.17). Besides, camels, intended for meat production from small herds showed a high level of infection (52%) (OR = 2.43, 95%CI: 1.3-4.5). Coxiellosis evolved in dromedary herds throughout the year, however infection was significantly important in autumn (60%) (OR = 4.13, 95%CI: 1.86-9.17) and winter (56%) (OR = 5.52, 95%CI: 2.50-12.16). Bioclimatic stage, gender, tick infestation and contact with other ruminants were not risk factors in camel's infection by C. burnetii. Our reports confirm that Tunisian one-humped dromedaries had been exposed to this bacterium and could contribute to its dissemination among farmers and other livestock animals. Furthers studies are required to evaluate the prevalence of Q fever among people professionally exposed like farmers, veterinarians and slaughterhouse workers.