Cervid Herpesvirus 2 Infection In Reindeer In Norway

Reindeer (Rangifer tarandus) can be found all over the circumpolar arctic regions with a total number of animals of more than five million. In Norway there were more than 240.000 animals in 2007, of which more than 70% inhabit the county of Finnmark (northern most region of mainland Norway), where reindeer herding continues to represent an important economical and cultural activity for the local indigenous communities.

Reindeer mortality in Norway reaches high values, especially in calves. While predators are known to account for great part of these deaths, some other causes remained explained. Previous serological studies had demonstrated that an unknown alphaherpesvirus was present in the reindeer population in Norway and could hence be involved in some of this mortality.

With this background information, Carlos G. das Neves has been working for the past four years to map the seroprevalence of cervid herpesvirus 2 (CvHV2) in the several reindeer husbandry districts of Finnmark County, understanding at the same time the biological, ecological and geographical variables involved in transmission and infection of/with CvHV2.

In his doctoral work, Carlos das Neves has by the first time isolated CvHV2 in Norway, and also demonstrated that this virus can be involved in an ocular disease and abortion. The ocular disease (Infectious keratoconjunctivitis) has been known and observed for many years in Scandinavia but its primary etiological agent has only now been confirmed as being CvHV2. It is known that herpesviruses can infect several ruminant species and cause disease, but it remained unknown until the present work which was the impact of CvHV2 for reindeer, namely which clinical symptoms it could cause after genital or nasal infections.

After a large serosurvey including more than 3000 animals, Carlos das Neves has demonstrated that 49% of tested reindeer had antibodies against an alphaherpesvirus, later shown to be CvHV2.

In two experimental studies, Carlos das Neves has also studied different aspects of CvHV2 infection, showing that CvHV2 can cause viremia (spread via the blood to different organs), become latent in the brain, and be transmitted vertically from mother to fetus via the placenta, fact which can result in the birth of weak calves or even in abortion.

CvHV2 was isolated by the first time in natural conditions during the keratoconjunctivitis outbreak, and in association with secondary bacteria this disease can cause mild to very severe symptoms, which can include, at a final stage, the loss of the ocular globe and blindness.

Globally the present work demonstrates the importance and impact of this virus for reindeer and demonstrates the importance of better understanding the possible effects of herding techniques in virus transmission. Further studies will also be essential to access the impact of this virus in abortion.