Seroprevalence of malignant catarrhal fever in cattle and sheep from South Brazil

Authors: MORÉ, DANIELA - Washington State University; Baker, Katherine; DE PAULA, SERGIO - Universidade Federal De Vicosa; PRATES, JOHN - Universidade Federal De Vicosa; Cunha, Cristina; BRUM, MARIO - Universidade Federal Do Pampa

Submitted to: Brazilian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2025
Publication Date: 12/14/2025
Citation: Moré, D.D., Baker, K.N., de Paula, S.O., Prates, J., Cunha, C.W., Brum, M.C. 2025. Seroprevalence of malignant catarrhal fever in cattle and sheep from South Brazil. Brazilian Journal of Microbiology. 57. Article 7. https://doi.org/10.1007/s42770-025-01814-7.
DOI: https://doi.org/10.1007/s42770-025-01814-7

Interpretive Summary: Malignant catarrhal fever (MCF) is a viral disease that impacts veterinary health and livestock industries in many countries. The form of the disease transmitted by sheep has been reported in Brazil. In these cases, sheep are the adapted host, not developing disease themselves but transmitting the virus to non-adapted species, such as cattle, which can develop the disease. MCF in non-adapted hosts is frequently fatal. The southern region of Brazil is the second in importance for the sheep industry in the country, and although cases of MCF have been reported in cattle, no information on the disease epidemiology is available for the region. In this work, we selected 20 farms in that region that rear bovine and ovine concomitantly to evaluate the serological prevalence of the disease in both species. For that, 253 cattle and 137 sheep samples were analyzed, and 4.7% and 92% of them, respectively, were positive for MCF antibodies, although no clinical signs of the disease were observed. These results show that the virus circulates in these populations and that the high prevalence of MCF among sheep represents a risk for cattle. The study represents a first step on better understanding the epidemiology of MCF in the south of Brazil, which is critical on implementing strategies to control viral transmission and disease in cattle.

Technical Abstract: Malignant Catarrhal Fever (MCF) is caused by a group of gamma-herpesviruses in the genus Macavirus. Virus transmission occurs through nasal shedding from an adapted host, such as sheep, which do not develop the disease, to non-adapted hosts, such as cattle, pig, bison, and deer, that can develop an often-fatal form of the disease. There is no specific treatment or available vaccine to control MCF and losses due to the disease significantly affect livestock industries worldwide. To determine the seroprevalence of MCF in South Brazil, blood samples were collected from sheep and cattle reared simultaneously in 20 farms from western region of Rio Grande do Sul state. A competitive enzyme-linked immunosorbent assay was used to detect specific antibodies to MCF viruses, and the prevalence was calculated for each herd/flock according to the total number of samples analyzed. We found seropositive sheep in all flocks tested, with an average prevalence of 92%. Among the bovine herds, on average 4.7% of the animals tested were seropositive. Although no clinical cases were observed during the study, the management system applied in the farms associated with the high prevalence of seropositive sheep represent a potential significative risk for cattle in the region. This work sheds light on the understanding of MCF epidemiology on South Brazil and supports the improvement of methods to control virus transmission and disease in cattle.