Study of equid herpesviruses 2 and 5 in Iceland with a type-specific polymerase chain reaction

The horse population in Iceland is a special breed, isolated from other horses for at least 1000 years. This provides an exceptional opportunity to investigate old and new pathogens in an inbred herd with few infectious diseases. We have developed a high sensitivity semi-nested PCR to study equid gammaherpesviruses 2 and 5 (EHV-2 and 5) in Iceland. The first PCR is group specific, the second type-specific, targeting a 113 bp sequence in the glyB gene. DNA isolated from white blood cells and 18 different organs was tested for the presence of EHV-2 and 5. This was done in adult horses and foals, healthy and with various enteric infections. Both virus types were easily detected in all types of organs tested or EHV-2 in 79% cases and EHV-5 in 63%. In DNA from PBMC or buffy-coat EHV-2 was found in 20% cases and EHV-5 in 10%, all except one positive were foals. Co-culture of PBMC on fetal horse kidney cells was efficient for detecting EHV-2 but not for EHV-5. We verify here for the first time infections with EHV-2 and 5 in horses in Iceland and show that both viruses are common.