Rotavirus Plasma and The Equine Neonate

Rotavirus infections are a significant cause of diarrhoea in the foal, the virus being first observed in faecal samples by Flewett et al. (1975) and since implicated in several outbreaks of infectious diarrhoea (Eugster et al. 1978; Dwyer and Powell 1989; Baldwin et al 1990; Higgins et al 1990; Browning et al 1991; Dugdale 1992). Rotavirus diarrhoea occurs generally as an epidemic with a high percentage of the foal herd affected. Clinical signs vary from mild and non specific to severe diarrhoea. The first signs are usually depression and failure to suck. 12-24 hours later these are followed by a profuse, non-foetid, yellow-green to grey watery diarrhoea. Rapid dehydration follows and pyrexia is variable. Once foals stop sucking they weaken rapidly and the younger the foal, the more seriously it is affected by dehydration.

Treatment is usually symptomatic involving electrolytes, fluid therapy, with occasionally antibiotics, spasmolytics and anti-ulcer preparations. In recent years, prophylactic treatment has been extended to the use of oral plasma containing rotavirus antibodies. In two recently documented outbreaks, treatment was based on the administration of plasma from mares selected because their foal had suffered recently from rotavirus diarrhoea in the hope that this would have enhanced their antibody content. (Dugdale 1992; Dugdale 1995). In the absence of an acceptable vaccine the logic of feeding immunoglobulins to provide continued local gut protection is persuasive. However, despite the presence of common group-specific antigens amongst all the rotaviruses, cross protection is unreliable and one cannot rely on vaccines made for other species to protect foals against rotavirus.(Dugdale 1992)

Veterinary Immunogenics Ltd has been following these developments and note these comments. We use a licensed commercial vaccine containing the equine strain (H2) rotavirus antigen to produce HYPERMUNE-RV, equine plasma with SVN titres as high as 1:10,000 specifically to the equine H2 strain. This plasma is available in pre-filled 35ml syringes for oral use for both treatment and prophylaxis. The dose is variable, as the heavier the rotavirus challenge, the more antibody is needed to neutralise it. It has been documented that 50ml had a prophylactic effect when given to newborn foals at a few hours of age and subsequently at daily intervals for three days. (Dugdale1992). However, for treatment, Beaufort Cottage Laboratories Newsletter May 1994 states, "Well organised stud-farms can often follow a supervised oral dosing schedule such as 50-100mls hyperimmune plasma orally TID until symptoms abate." Because HYPERMUNE-RV is equine strain specific and high titre, an initial oral dose of 35 mls is recommended for a 50kg foal and daily thereafter for at least three days in divided doses. This advice is confirmed by customer feedback. If symptoms are not abating in 24 - 36 hours the dose should be increased. In very severe cases of dehydration and collapse the use of plasma intravenously should be considered, as dramatic improvements have been reported to us when this approach has been used.

Although there are some gram negative anti-endotoxin antibodies present in HYPERMUNE-RV it must be emphasised that it is specifically produced for confirmed rotavirus outbreaks. Having said that, we have had reports of its usefulness in helping to control diarrhoea not specifically due to rotavirus such as when the mare is in season.

References

  • 1. Baldwin, J L., Cooper, WL., and Higgins, WP (1990) Epidemiology of an outbreak of rotavirus associated enteritis in foals on a large horse breeding farm. Proc. 2nd Int. Vet. Perinatol. Cambridge p60.
  • 2. Browning, G F., Chalmers, R M., Snodgrass, D R., Batt, R M., Hart, C A., Ormarod, S E., Leadon, D P., Stoneham, S J., and Rossdale, P D. (1991) The prevalence of enteric pathogens in diarrhoeic Thoroughbred foals in Britain and Ireland. Equine vet. J. 23, 405-409.
  • 3. Conner, M E. and Darlington, R W. (1980) Rotavirus infection in foals. Am. J. vet. Res. 41, 1699-1703.
  • 4. Dugdale, D., (1992) Outbreak of rotavirus diarrhoea in 2 successive years on a studfarm. E V E 4, (5) 233-236
  • 5. Dugdale, D., (1995) Foal Medicine Workshop BEVA Congress 1995
  • 6. Dwyer, R M., and Powell, DG. (1989) The third report of the Lloyds foal disease project. University of Kentucky, pp 2-10.
  • 7. Dwyer, R M., Powell, D G., Lyons, F., Donahue, J M., Roberts, A W. and Osborne, M. (1988) The aetiology of infectious diarrhoea in Thoroughbred foals in central Kentucky. Equine vet. J. Suppl. 5, pp 59-60.
  • 8. Eugster, A K., Whitford, H W. and Mehr, L E (1978) Concurrent rotavirus and Salmonella infections in foals. J. Am. vet. med. Ass. 173, 857-858.
  • 9. Flewett, T H., Bryden, A S., and Davies, H A. (1975) Virus diarrhoea in foals and other animals. Vet. Rec. 96, 477.