Epizootiological and virological studies of foal diarrhea associated with serotype 3 rotavirus.

This research paper focuses on the study of foal diarrhea occurrence at three foal-raising locations on a horse farm, and its potential link to serotype 3 rotavirus (RV).

Research Context and Methods

• The study was carried out at three separate locations within a light horse farm, monitoring the occurrence of diarrhea among foals in these areas from March to July, 1987.
• The researchers investigated the rate of rotavirus (RV) presence, common cause for diarrhea in mammals, in these outbreaks. The RV isolation rate refers to the percentage of fecal samples containing the virus.
• The researchers also examined the ages of foals at the onset of diarrhea and the period of time the disease was present at the different locations.
• A plaque-reduction neutralization test, a method often used to measure the specific immune (antibody) response to a virus, was used to determine the serotype of the RV present. Serotypes are categories within a species of microorganisms, such as bacteria or viruses, based on their reaction to immune response.

Research Findings

• At the first location, 75% of foals developed diarrhea, though the RV isolation rate was relatively low (36%), indicating that other factors might have contributed to the onset of the disease. Many foals were as young as 23 days old at the onset.
• At the second and third locations, 27% and 76% of the foals, respectively, were affected by diarrhea with high RV isolation rates of 90% and 100%.
• The disease was predominantly observed in foals aged 63 to 65 days, and during a short window from June to early July. These findings emphasized the importance of RV as a causal factor in these latter cases.
• All RV strains from each location were identified as serotype 3 using the plaque reduction neutralization test against antiserums of serotypes 1-6 of RV. However, these serotype 3 RV strains exhibited low cross-reactivity with antiserum of the same serotype of equine RV, implying that the tested strains might differ in some manner from the typical equine RV serotype 3.

Conclusion

• The research concluded that the serotype 3 rotavirus was a common cause of foal diarrhea across the study locations, particularly for the second and third sites. However, the first location’s lower RV isolation rate and wide age range at onset highlighted the potential involvement of other factors or pathogens in the outbreak.
• The low cross-reactivity of the serotype 3 RV strains with equine RV antiserum suggested divergences between these strains and the serotype 3 RV usually seen in horses.