Isolation of an adenovirus antigenically distinct from equine adenovirus type 1 from diarrheic foal feces.

This research isolated a new type of adenovirus from the feces of foals with diarrhea, which was found to be distinct from the previously known equine adenovirus type 1. The prevalence of antibodies against this new adenovirus, proposed to be deemed EAdV2, in tested horse serum samples was high, at 77%.

Research Methods and Findings

• Researchers analyzed foal feces for the presence of microorganisms and discovered an adenovirus in samples from two foals suffering from diarrhea. These samples contained notably high counts of rotavirus particles. The virus was grown under laboratory conditions in equine fetal kidney cell cultures.
• Distinguishing characteristics of the isolated virus were observed. Unlike equine adenovirus type 1 (EAdV1), the adenovirus derived from the fecal samples did not cause hemagglutination in red blood cells cloned from humans, rhesus macaques, or horses; this phenomenon is when the virus causes the red blood cells to clump together.
• A technique known as serum neutralization was used to examine the strain relations between the adenoviruses from the fecal samples and EAdV1. The results showed that although the two fecal viruses were identical to each other, they demonstrated no relationship to EAdV1. Moreover, antiserum generated against the fecal viruses failed to inhibit hemagglutination by EAdV1, providing further evidence for their distinction.

Proposal and Prevalence

• Based on these findings, the researchers suggested that the adenoviruses isolated from the fecal samples be considered a new type of equine adenovirus, tentatively named EAdV2.
• In order to understand the prevalence of EAdV2, the investigation was expanded to check the frequency of antibodies produced against it in the serum samples of 339 horses, revealing a high prevalence of 77%.
• The researchers also confirmed through further serum neutralization tests that neither EAdV1 nor EAdV2 showed any relations to any of the 30 human adenovirus serotypes.

Conclusions

• The discovery of this new adenovirus, proposed to be called EAdV2, which shows no antigenic relation to EAdV1 or to human adenovirus serotypes, indicates potential for a broader diversity of adenoviruses affecting horses than previously known.
• The high prevalence of antibodies to EAdV2 in equine serum reflects that this virus is widespread among horses, suggesting that it may play a role in equine health and disease, such as causing diarrhea in foals.