First case-control study of zoonotic brucellosis in Gafsa district, Southwest Tunisia

Abstract

A case-control study was conducted, aimed to describe the clinical human brucellosis (CHB) pattern during 2015 in the Gafsa region (Southwest Tunisia) and to investigate the main risk factors involved in the disease occurrence. One hundred and four CHB cases were notified in 2015 in Gafsa district. All CHB cases that own ruminants were contacted, but only 32 accepted to participate in a matched case-control study. Thirty-two and thirty-one CHB cases and controls, respectively, were included in the study. The subjects were interviewed using a structured questionnaire. A total of 662 domestic ruminants (cattle, sheep and goats) belonging to cases and controls, were screened using the Rose Bengal Test, as recommended by the World Organisation of Animal Health. During 2015, the incidence of CHB was estimated to 30.8 per 100,000 inhabitants affecting mainly males aged between 30 and 39 years. The overall animal seropositivity to Brucella, was 21 and 1.9% in case and control farms, respectively (p < 0.0001). Only five risk factors were found to be significant: overall animal seropositivity (OR = 65.2; 95%CI: 13.3-318.7); handling aborted females (OR = 43.1; 95%CI: 8.3-222.7); presence of male ruminants in the herds (OR = 18.5; 95%CI: 5.18-66); owning seropositive goats (OR = 18.3; 95%CI: 2.4-137.6), owning seropositive sheep (OR = 9.66; 95%CI: 2.9-31.5) and history of abortion during the previous year in the herd (OR = 4.6; 95%CI: 1.3-12.6). Vaccination of animals against brucellosis was associated with lower odds of human brucellosis (OR = 0.03; 95%CI: 0.004-0.2). Raw milk and derivatives consumption was not a risk factor of human brucellosis. Based on this study, ruminants' vaccination coverage should be increased by enhancing the number of vaccinated animals and systematically including male ruminants in Tunisia. Comprehensive education programmes targeting both farmers and general population should be implemented.

Keywords: Abortion; Clinical human brucellosis; Risk factors; Ruminants; Tunisia.

Fig. 1

Map of Tunisia with Gafsa district location.

Fig. 2

Age-incidence of clinical human brucellosis (CHB) during 2015 in Gafsa district, Southwest Tunisia.

Fig. 3

Incidence per 100,000 inhabitants of clinical human brucellosis in Gafsa localities during 2015.

Fig. 4

Monthly number of clinical human brucellosis (CHB) cases in Gafsa district during 2015 (dots indicate the observed values, the line is the fitted curve).