Equine viral diseases in the Pantanal, Brazil. Studies carried out from 1990 to 1995

Abstract

A survey on equine viral diseases was carried out in the Pantanal, Brazil, from 1990 to 1995, and the authors report for the first time the occurrence of respiratory viral diseases in horses from the Pantanal. Seropositivity for the equine adenovirus was 42%, primarily among animals under 3 years of age (61.9%). It was 36% for the equine herpesvirus 1 (EHV-1) (50 and 22.2% of seropositive foals and mares, respectively). The observed seropositivity for EHV-1/respiratory was 58%. Among the equine rhinoviruses only equine rhinovirus 1 (ERV-1) was studied in this survey. Seropositivity for ERV-1 was 18%. Foals aged 1 to 2 years (22.2%) presented a titer of 1/5. Titers of 1/10 and 1/20 were only observed in animals over 5 years old. Seropositivity for influenza A/Equine/2/Miami was 30%. Foals represented 40% and mares 28.6% of all seropositive animals. Seropositivity for influenza A/Equine/2/Fontainebleau was 42%. Foals and mares represented 86% (43% in each group) of all seropositive animals. In the study on equine infectious anemia, the observed prevalence was 24.8%. Seropositivity among males was 14.3% and among females 10.6%. In the survey on arboviroses, neutralizing antibodies to the eastern equine encephalomyelitis (6.7%), western equine encephalomyelitis (1.2%) viruses, Ilheus flavivirus (26.6%), Maguari (28.2%) and Tacaiuma (15.7%) bunyaviruses were observed. The equine viral arteritis was not found in the region. In the Pantanal, except for arboviroses, apparently all equine viruses are acquired when young horses mix with older ones or through local management practices.