Original Research

Experimental exposure of pregnant mares to the asinine-94 strain of equine arteritis virus

J.T. Paweska, M.M. Henton, J.J. Van der Lugt
Journal of the South African Veterinary Association | Vol 68, No 2 | a869 | DOI: https://doi.org/10.4102/jsava.v68i2.869 | © 1997 J.T. Paweska, M.M. Henton, J.J. Van der Lugt | This work is licensed under CC Attribution 4.0
Submitted: 13 July 1997 | Published: 13 July 1997

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J.T. Paweska,
M.M. Henton,
J.J. Van der Lugt,

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Abstract

Clinical, virological and serological responses were evaluated in 10 pregnant mares after different challenge exposures to the asinine-94 strain of equine arteritis virus (EAV). The outcome of maternal infection on the progeny was also investigated. Mares were inoculated intranasally (n = 4), intramuscularly (n = 2), intravenously (n = 1), or contact-exposed (n = 3). All inoculated mares developed pyrexia, 5 showed mild clinical signs related to EAV infection and 2 remained asymptomatic. Viraemia was detected in all the inoculated animals and shedding of virus from the respiratory tract occurred in 6. Five mares were re-challenged intranasally 7 and 15 weeks after inoculation. Clinical signs of the disease in these mares were limited to mild conjunctivitis. After re-challenge, virus was recovered from buffy coat cultures of 2 mares 2-6 days after re-infection. EAV was not recovered from colostrum and milk samples during the 1st week post partum. All inoculated mares seroconverted to EAV 8-12 days post inoculation and also seroconverted after re-challenge. No clinical signs of EAV infection were observed in the 3 mares kept in close contact during the post-inoculation and re-challenge periods. Serum neutralising antibody to the virus was detected in 1 in-contact mare only, while a detectable concentration of specific IgG was found by ELISA in the colostrum of 1 of the other in-contact mares. Eight of the mares gave birth to clinically normal foals, although 1 was born prematurely. Shortly after birth, 7 foals developed fever and variable clinical signs; 5 foals became septicaemic and 3 of them died 2-5 days after birth, while the remaining 2 were euthanased at 1 month of age. EAV was not recovered from the placenta, from buffy coat fractions of blood collected from foals immediately after birth and 1-3 days later, or from a range of tissues taken from the 3 foals that died and 2 that were euthanased. Virus was not isolated from tissues collected from 1 mare and her foetus 3 weeks after this mare was re-challenged.

Keywords

Asinine-94 Virus Strain; Equine Arteritis Virus; Experimental Exposure; Pregnant Mares; Progeny; Responses

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