Unveiling Q Fever Underreporting in Humans and Livestock: A One Health Alert

Abstract

Q fever, caused by Coxiella burnetii, is a globally distributed zoonosis that remains substantially underdiagnosed, despite increasing reports of human and animal infections across Europe. Within the Zoonoses Working Group of the Trás-os-Montes and Alto Douro Academic Clinical Center (CAC TMAD), which integrates human and animal health professionals, an apparent discrepancy emerged. Although no official human notifications had been recorded in Trás-os-Montes in recent years, three clinical cases, at hospital level, were identified in the Bragança district between 2021 and 2024. This unexpected finding prompted an evaluation of local veterinary awareness of Q fever in livestock, given that no cases had ever been reported. A structured, simple questionnaire was provided to all livestock veterinarians in the district, achieving an 88.5% response rate (23/26). Among respondents, 43.5% (10/23) reported laboratory-confirmed C. burnetii-positive results in clinically suspected livestock (both serology and PCR). All reported clinical cases occurred in small ruminants, with abortion as the predominant clinical manifestation. These results provide local evidence of active C. burnetii circulation in both humans and livestock in Bragança, suggesting potential underreporting. This gap supports the need to strengthen clinical recognition and reporting practices among medical and veterinary professionals, firmly embedded within a One Health framework.