Acute Leptospirosis Outbreak in Cattle: A Case Report

Leptospirosis is a globally distributed re-emerging zoonotic disease caused by Leptospira species. In cattle, the clinical course varies from a subclinical-chronic infection, commonly found in adult animals, to a severe acute syndrome mostly found in calves. The present study reports an outbreak of acute leptospirosis, following favourable climacteric conditions. Seven affected farms were monitored. Clinical observations from infected animals (n = 30) revealed two distinct patterns: lactating calves experienced hyperacute courses, often culminating in death, and older animals, mainly steers, displayed signs of apathy, anorexia, icterus and haemoglobinuria. Necropsies confirmed jaundice and haemoglobinuria, aligning with a presumptive diagnosis of leptospirosis. Haematology and serology results further supported this diagnosis. Pomona and Mozdok serovars were the most prevalent (62.5%) and had the highest mean agglutination titres, 1:1160 and 1:700, respectively. Antimicrobial treatment of sick animals consisted of oxytetracycline. Chemical metaphylaxis and prophylactic measures were established to control the outbreak in cohabiting animals. Environmental factors like climate change are expected to contribute to more frequent leptospirosis outbreaks. Comprehensive serological surveys are recommended to develop region-specific control measures, emphasising the importance of vaccination as a practical and effective prophylactic measure.

The authors sincerely thank the veterinarians from Vet+ clinic, Dr. Evaristo Silva and Jaime Ribeiro for supporting the fieldwork. We also want to thank Dr Teresa Rocha from the National Institute of Agrarian and Veterinary Research (INIAV) for conducting the MAT tests. This work was funded by National Funds through FCT - Fundaçao para a Ciencia e a Tecnologia, I.P., within the scope of the programmatic funding UIDP/05937/2020 with DOI identifier 10.54499/UIDP/05937/2020 and base funding UIDB/05937/2020 with DOI identifier 10.54499/UIDB/05937/2020.