Gammaherpesvirus carrier status of black wildebeest (Connochaetes gnou) in South Africa.

ABSTRACT

Malignant catarrhal fever (MCF) is an economically important disease primarily of domestic cattle with a high case fatality rate. It is caused by either alcelaphine herpesvirus type 1 (AlHV-1) or ovine herpesvirus type 2 (OvHV-2). The major reservoir host of AlHV-1 is the blue wildebeest (Connochaetes taurinus), but it is generally accepted that the black wildebeest (Connochaetes gnou) is also a reservoir host. No viral studies in the black wildebeest have been reported and the carrier status of black wildebeest has not been documented. Specimens were collected from several game farms and conservation areas in central South Africa representing the geographical area historically linked to the natural habitat of the black wildebeest. Specimens were obtained from 304 black wildebeest of different ages and sex, as well as 51 black wildebeest foetuses at different stages of gestation. Virus was isolated from a black wildebeest calf. Morphological features and antigenic characteristics suggested it to be a gammaherpesvirus closely related to AlHV-1. All serum samples tested positive with a competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) for group-specific malignant catarrhal fever virus antibody. A SYBR Green real-time PCR assay was developed for the detection of gammaherpesviral DNA. Only 15.8 % of the animals tested positive with the real-time PCR assay whereas 90 % of the foetuses tested positive. This finding suggests that, unlike OvHV-2 infection in lambs in which the infection takes place after weaning, the virus in black wildebeest is mainly transmitted in utero or soon after birth. The results suggest that black wildebeest are latent carriers of a gammaherpesvirus similar or closely related to AlHV-1 present in blue wildebeest and that it is likely that all black wildebeest are persistently infected.