Surveillance of avian influenza and Newcastle disease viruses in backyard poultry raised near migratory bird sites in Mato Grosso state, Brazil.

Abstract

The Pantanal and Cerrado biomes in the state of Mato Grosso contain migratory bird sites in the municipalities of Cáceres and Araguaiana, respectively. The levels of avian influenza (AI) and Newcastle disease (ND) viral activity in backyard poultry at these sites are unknown owing to a lack of studies. Considering the risk of introduction of AI and ND to Brazil from migratory birds, as well as the importance of active surveillance in the detection and prevention of diseases for official control, monitoring in these poultry populations is faster, more practical and cheaper for official service veterinarians. The objective of this study was to verify the presence of AI and ND viral activity in backyard poultry reared near these migratory bird sites in the years 2016 and 2019. Serum samples and cloacal and tracheal swab samples collected from chickens, turkeys, quails, ducks and geese were evaluated by indirect diagnostic methods including enzyme-linked immunosorbent assay and haemagglutination inhibition tests and direct detection of viral sequences using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). No positive samples were detected by qRT-PCR.The frequencies of birds seropositive for AI and ND were 0.7% and 19.6% in 2016 and 0.5% and 17.2% in 2019, respectively, in Araguaiana and 0.8% and 32.3% in 2016 and 7.0% and 38.1% in 2019, respectively, in Cáceres. Antibodies belonging to AI subtypes H1, H4, H6 and H14 were identified in Cáceres in 2019. Spatial analysis showed an agglomeration of farms with seropositive poultry within the urban area of Cáceres, suggesting AI and ND virus activity in this area. This study showed no circulation of the notifiable AI subtypes H5 and H7 or the ND virus in backyard poultry raised around migratory bird sites in the state of Mato Grosso. The results of the present study support evidence indicating that the circulation of strains with low pathogenicity in urban areas enables backyard poultry to serve as a source of infection for other birds; thus, increased surveillance is necessary in this population.