Retrospective serological survey for influenza in horses from Brazil
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VETERINARY MICROBIOLOGY - SHORT COMMUNICATION
Retrospective serological survey for influenza in horses from Brazil J. M. Daly 1
&
J. Megid 2 & H. Langoni 2 & G. de Nardi Júnior 3 & M. G. Ribeiro 2
Received: 7 May 2020 / Accepted: 27 October 2020 # Sociedade Brasileira de Microbiologia 2020
Abstract Equine influenza (EI) virus is one of the most economically important pathogens of respiratory diseases of horses worldwide. Despite availability of vaccines for control of EI, the highly contagious nature and variability properties of the virus mean global outbreaks occur. Thus, continuous surveillance programs, including seroprevalence studies of disease in different countries, may contribute to better control of the disease. In this study, the seroprevalence of equine influenza in 850 horses from Brazil was investigated. The serodiagnosis was based on the single radial hemolysis (SRH) assay using influenza A/equine/Richmond/1/ 2007 (H3N8) antigen. Antibodies against A/equine/Richmond/1/07 (H3N8) were detected in 44.7% (380/850, 95% CI: 41.4– 48.1%) of horses. Seroprevalence was significantly lower (p = 0.001) in younger animals (< 5 years, 38.6%) than in “adult” animals (5–14 years, 52.1%). There was also a significant relationship between the year of sampling and seroprevalence (p < 0.0005). The mean SRH antibody value was 42.0 mm2 (range 4–238.9 mm2), with the majority of horses (95.3%) having an SRH value ≤ 150 mm2, which is considered an insufficient level for protection of equine hosts against influenza infections and potential virus shedding. These findings indicate the need to reinforce preventive/control measures against equine influenza in Brazil. Keywords Horses . Influenza virus H3N8 . Seroprevalence . Serodiagnosis
Introduction Alphainfluenzavirus, a renamed genus in the Orthomyxoviridae family [1], is comprised of emerging and re-emerging animal and human diseases associated with severe respiratory infections worldwide. Particularly, the equine influenza virus (EIV) is the causative agent of equine influenza (EI). It is one of the most economically important pathogens causing respiratory disorders of horses worldwide because of its rapid spread and highly contagious nature among susceptible hosts. Influenza A viruses of the H3N8 subtype were first isolated from horses in 1963. The equine H3N8 Responsible Editor: Fernando R. Spilki. * M. G. Ribeiro [email protected] 1
School of Veterinary Medicine and Science, University of Nottingham, Nottingham, UK
2
Infectious Diseases of Domestic Animals, Department of Animal Production and Preventive Veterinary Medicine, School of Veterinary Medicine and Animal Science, São Paulo State University-UNESP, Botucatu, SP 18618-681, Brazil
3
Technology Faculty-FATEC, Botucatu, SP, Brazil
virus is thought to have emerged in South America; phylogenetic analysis demonstrated that genes of the virus isolated from horses shared a most recent common ancestor with avian strains circulating in Argentina, Bolivia, Brazil, and Chile a few years before it was first i
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