Equine influenza outbreak in India (2008-09): virus isolation, sero-epidemiology and phylogenetic analysis of HA gene.
Abstract: An outbreak of equine influenza (EI) was reported in India in June, 2008 after a gap of two decades. The outbreak started from Jammu and Kashmir (Katra), northern state of India and spread to the other parts of the country affecting equines in 11 states. The virus (H3N8) was isolated from nasal swabs obtained from clinical cases in various locations in the country including Katra (Jammu and Kashmir), Mysore (Karnataka) and Ahmedabad (Gujarat) using embryonated chicken eggs. The virus isolates were identified as H3N8 by haemagglutination inhibition (HI) test titration with standard serum and by sequencing of full-length haemagglutinin (HA) gene and partial sequence of neuraminidase (NA) gene. Paired serum samples (n=271) showing more than fourfold rise in antibody titres tested from 11 states confirmed equine influenza. Serum samples (n=2517) of equines from 13 states of the country screened by HI test revealed 687 (26.85%) samples positive for antibodies to EI (H3N8). Phylogenetic analysis of the haemagglutinin (HA) gene confirmed the virus to be closely related to Clade 2 of the Florida sublineage in American lineage. Comparison of deduced amino acid sequence of HA gene with EIV isolates from various lineages showed substitutions in the antigenic regions C and D. HA1 gene sequence had highest amino acid identity to A/eq/Gansu/7/08 and A/eq/Hubei/6/08 isolates from China and Inner-Mongolia isolate, while the complete HA gene sequence was closest to A/eq/A/eq/Newmarket/5/03, A/eq/Bari/05 and A/eq/Kentucky/05/02 isolates. Recent outbreaks of Mongolia, China and India by clade 2 EI viruses imply their predominance in Asia in addition to Europe.
(c) 2009 Elsevier B.V. All rights reserved.
Publication Date: 2010-01-06 PubMed ID: 20053509DOI: 10.1016/j.vetmic.2009.12.007Google Scholar: Lookup
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Summary
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This research article describes an equine influenza outbreak in India in 2008-09, detailing virus isolation, the sero-epidemiology of the illness, and a phylogenetic analysis of the virus’s HA gene.
Overview of the Outbreak
- After two decades with no reported cases, an equine influenza (EI) outbreak occurred in India in June 2008. The outbreak originated in Jammu and Kashmir (Katra), a northern state, and spread throughout the county, affecting 11 different states.
- Nasal swabs from affected horses in various locations were collected and the virus (H3N8 subtype) was successfully isolated using embryonated chicken eggs.
Virus Identification and Serology
- The virus isolates were identified as subtype H3N8 through a haemagglutination inhibition (HI) test and sequencing of the full-length haemagglutinin (HA) and partial neuraminidase (NA) genes.
- Serum sample testing from equines in 11 states confirmed the EI outbreak. From the 2517 serum samples collected from 13 states and tested by HI, 687 tested positive for antibodies to the H3N8 virus, indicating a recent infection.
Phylogenetic Analysis
- Phylogenetic analysis was conducted on the HA gene. The results confirmed that the Indian H3N8 virus was closely related to Clade 2 of the Florida sublineage in the American Lineage.
- Amino acid sequence comparison of the HA gene with other EI isolates from various lineages revealed substitutions in the antigenic regions C and D.
- Research found a high amino acid identity between the HA1 gene sequence of the Indian samples and the A/eq/Gansu/7/08 and A/eq/Hubei/6/08 isolates from China, as well as the isolate from Inner-Mongolia.
- The complete HA gene sequence showed the most resemblance to A/eq/A/eq/Newmarket/5/03, A/eq/Bari/05, and A/eq/Kentucky/05/02 isolates.
Implications and Conclusions
- The research implies that Clade 2 EI viruses are predominant in Asia and Europe. The recent outbreaks in Mongolia, China, and India are believed to demonstrate a pattern of this predominance.
- The study’s findings contribute valuable information to the ongoing surveillance and understanding of equine influenza epidemics globally.
Cite This Article
APA
Virmani N, Bera BC, Singh BK, Shanmugasundaram K, Gulati BR, Barua S, Vaid RK, Gupta AK, Singh RK.
(2010).
Equine influenza outbreak in India (2008-09): virus isolation, sero-epidemiology and phylogenetic analysis of HA gene.
Vet Microbiol, 143(2-4), 224-237.
https://doi.org/10.1016/j.vetmic.2009.12.007 Publication
Researcher Affiliations
- National Research Centre on Equines, Sirsa Road, Hisar 125 001, Haryana, India. nvirmani@gmail.com
MeSH Terms
- Amino Acid Sequence
- Animals
- Antigens, Viral
- Disease Outbreaks / veterinary
- Hemagglutinins / chemistry
- Hemagglutinins / genetics
- Hemagglutinins / metabolism
- Horse Diseases / epidemiology
- Horse Diseases / virology
- Horses
- India / epidemiology
- Influenza A virus / genetics
- Influenza A virus / immunology
- Molecular Sequence Data
- Orthomyxoviridae Infections / epidemiology
- Orthomyxoviridae Infections / veterinary
- Orthomyxoviridae Infections / virology
- Phylogeny
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