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Seroprevalence of Equine Influenza and Its Associated Risk Factors in Northwest Nigeria

Olufemi, Olaolu T.; Edeh, Emmanuel R.; Isyaku, Mustapha S.; Haliru, Mustapha; Samaila, Shafiu; Mshelia, Philip W.; Owolodun, Olajide A.; Newton, J. Richard; Daly, Janet M.

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Olaolu T. Olufemi

Emmanuel R. Edeh

Mustapha S. Isyaku

Mustapha Haliru

Shafiu Samaila

Philip W. Mshelia

Olajide A. Owolodun

J. Richard Newton

Professor of Viral Zoonoses


Equine influenza (EI) is a fast-spreading respiratory disease of equids caused by equine influenza A virus (EIV), often resulting in high morbidity and a huge economic impact on the equine industry globally. In this cross-sectional study to determine the seroprevalence of EI and its associated risk factors, sera from 830 horses bled on a single occasion in Northwest Nigeria between October 2019 and January 2020 were screened for antibodies to A/equine/Richmond/1/2007 (H3N8) using the single radial haemolysis (SRH) assay. Antibodies were detected in 71.3% (592/830, 95% CI: 68–74%) of horses (SRH area ≥ 0.5 mm2). Although there were statistically significant univariable associations between seropositivity and age, sex, breed, purpose and coat colour, only age remained significant when included with each of the other variables in bivariable analyses. There was a clear trend for increasing odds of seropositivity with increasing age: OR 1.6, 95% CI: 1.05–2.40 (p = 0.03) for 5–14-year-olds and OR 8.13, 95% CI: 2.75–24.1 (p < 0.001) for ≥15-year-olds compared to horses <5 years old. The mean SRH value was 78.2 mm2 (median = 88 mm2, interquartile range = 0–121 mm2) with only 9% of the horses having an SRH value > 150 mm2, considered sufficient to protect against clinical disease and virus shedding. Comparative screening of a subset of the horses (n = 118) with a 2019 H3N8 virus (A/equine/Worcestershire/2019) revealed a significantly greater seropositivity (p = 0.0001) than A/equine/Richmond/1/2007 consistent with exposure of the population during a widespread outbreak of EI in the region in 2019. In conclusion, there was an insufficient level of protection against EI in the region and introduction of a vaccination programme with vaccines containing recently circulating virus is recommended to mitigate against further outbreaks of EI in Nigeria.


Olufemi, O. T., Edeh, E. R., Isyaku, M. S., Haliru, M., Samaila, S., Mshelia, P. W., …Daly, J. M. (2022). Seroprevalence of Equine Influenza and Its Associated Risk Factors in Northwest Nigeria. Pathogens, 11(11), Article 1372.

Journal Article Type Article
Acceptance Date Nov 14, 2022
Online Publication Date Nov 17, 2022
Publication Date 2022-11
Deposit Date Nov 18, 2022
Publicly Available Date Nov 18, 2022
Journal Pathogens
Publisher MDPI AG
Peer Reviewed Peer Reviewed
Volume 11
Issue 11
Article Number 1372
Keywords equine influenza, seroprevalence, Nigeria
Public URL
Publisher URL


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