Malignant catarrhal fever in American bison (Bison bison) experimentally infected with alcelaphine herpesvirus 2.

Malignant catarrhal fever (MCF), due to ovine herpesvirus 2 (OvHV-2), causes appreciable death loss in ranched bison (Bison bison) throughout North America. No vaccine exists to protect animals from disease. Since OvHV-2 has not been propagated in vitro, one strategy to develop a modified live vaccine is to use a closely related, non-pathogenic member of the malignant catarrhal fever virus family as a vector expressing potentially protective OvHV-2 epitopes. To date, no controlled experimental challenge studies with alcelaphine herpesvirus 2 (AlHV-2) derived from topi (Damaliscus lunatus jimela) have been reported The unique or light DNA segment of the AlHV-2 genome was sequenced and annotated and the virus was tested for its ability to infect and induce disease in American bison. Yearling bison were inoculated intranasally (n=4) or intramuscularly (n=3) with 2 × 10(-4.7) TCID50 of AlHV-2, and monitored for infection and the development of disease. Six inoculated bison became infected with AlHV-2. Two of the six animals developed clinical signs and had gross and histological lesions consistent with terminal MCF, which differed in distribution from those in bison with MCF due to OvHV-2. One other animal developed minor clinical signs and had gross and histological pulmonary lesions consistent with early (pre-clinical) stages of MCF. Unmodified low cell culture passage AlHV-2 derived from topi is an unsuitable vaccine vector for the prevention of MCF. However, the annotated genome might be useful in identifying genes which could be deleted to potentially attenuate the virus for bison.

Experimental induction of malignant catarrhal fever in pigs with ovine herpesvirus 2 by intranasal nebulization.

Malignant catarrhal fever (MCF), a frequently fatal herpesviral disease primarily of ruminant species, has been sporadically reported in pigs. All cases of naturally occurring porcine MCF reported to date have been linked to ovine herpesvirus 2 (OvHV-2), a gammaherpesvirus in the genus Macavirus carried by sheep. Experimental induction of MCF by aerosolization of the virus in nasal secretions collected from infected sheep has been successful in bison, cattle and rabbits. The goals of this study were to determine the susceptibility of pigs to MCF following experimental intranasal inoculation of OvHV-2, and to characterize the disease. Twelve pigs in four groups were nebulized with 10(5), 10(6), 10(7), or 10(8) DNA copies of OvHV-2 from sheep nasal secretions. Three control pigs were nebulized with nasal secretions from uninfected sheep. Three additional pigs were inoculated intravenously with 10(7) DNA copies of OvHV-2 to evaluate this route of infection with cell-free virus. Seven of twelve intranasally challenged pigs became infected with OvHV-2. Five of these seven, all in higher dose groups, developed MCF. Lesions resembled those reported in natural cases of porcine MCF. The most striking and consistent histological lesions were in trachea, lung, kidney and brain. These comprised mucopurulent tracheitis, interstitial pneumonia, necrotizing arteritis-periarteritis, and nonpurulent meningoencephalitis. No infection was established in the intravenously challenged or control groups. The study showed that MCF can be experimentally induced in pigs by aerosol challenge using sheep nasal secretions containing OvHV-2. Domestic pigs are a natural clinically susceptible host for sheep-associated MCF. They represent a useful, cost-effective model for MCF research.