RESUMO
The sero p revalences of brucellosis and Q-fever we re eva l u ated in humans and live s t o ck in three Chadian nomadic commu n i t i e s ; i . e. ; Fulani cattle bre e d e rs and A rab camel and cattle bre e d e rs. The survey was carried out in 1999 and 2000. The total number of human sera and animal sera tested were 911 and 1 637; respectively; for antibodies against Brucella spp. and 368 and 613; respectively; for Coxiella burnetii. Sixteen brucellosis positive human sera resulted in a seroprevelance rate of 2. Male participants were significantly more often brucellosis seropositive than females. No association was found between brucellosis serostatus and physical findings or reported symptoms. Positive brucellosis serology was more frequent in c attle (seropreva l e n c e;7) than in camels (1.4) and small ruminants (0.5). Fifteen human sera from 11 A rab camel bre eders and 4 Arab cattle breeders were positive for Q-fever (seroprevalence below 1). Being a camel breeder was a significant risk factor for Q-fever seropositivity. Camels had the highest Q-fever seroprevalence (73) among livestock species