ABSTRACT
The aim of this study was to estimate the prevalence of herds and animals infected with equine influenza virus in Uruará County, Pará State, Brazil. Antibodies against equine influenza virus were detected by the haemagglutination inhibition test. Sample size was estimated from 2,069 holder farms that raised Equidae and did not vaccinate against equine influenza virus. A 90% confidence level was adopted with 15% precision and 50% estimated prevalence. The following prevalence of serum reactors animals were observed: 55.6% (45/81) (CI 49.8-61.3) A/Eq1/SP/56 (H7N7) and 76.5% (62/81) (CI 70.7-82.3) A/Eq2/SP/1/85
(H3N8). All the farms were positive for both subtypes of equine influenza virus. It is concluded that both subtypes of equine influenza virus were circulating among animals and on all farms in Uruará County, Pará State, Brazil, Eastern Amazon Region, in the year of 1998.
KEY WORDS
Seroprevalence; equine influenza; Pará; Brazil; Amazon