Non-invasive detection of equid herpesviruses in fecal samples
Equid Herpesviruses (EHV) are pathogens of equid and non-equid hosts that can cause disease and fatalities in captivity and in the wild. EHVs establish latent infections but can reactivate, and most EHVs are shed via the nasal passage. Therefore, nasal swabs are generally used for EHV monitoring. However, invasive sampling of wild equids is difficult. While feces is a commonly used substrate for detecting other pathogens, to our knowledge EHVs have never been detected in feces of naturally infected equids. We systematically tested zebra feces for EHV presence by A) establishing nested PCR conditions for fecal DNA extracts, B) controlling for environmental EHV contamination, and C) large-scale testing on a free-ranging zebra population. A dilution minimizing inhibition while maximizing viral DNA concentration was determined in captive Grévys zebra (Equus grevyi) fecal samples from individuals shedding EHV nasally. Sixteen of 42 fecal samples (38%) were EHV-positive. To demonstrate that the EHV positivity was not a result of environmental contamination, rectal swabs of wild zebras were screened (N = 18; E. quagga and E. zebra), and 50% were EHV-positive, indicating that the source of EHV in feces is likely the intestinal mucosa, and not post-defecation contamination. Out of 270 fecal samples of wild zebras 26% were EHV-positive. Quantitative PCRs showed that the amount of virus DNA in feces was not significantly lower than in other samples. In summary, fecal sampling facilitates large scale screening and may be useful to non-invasively investigate phylogenetic EHV diversity in wild and domestic equids.