On Contagious Ecthyma and its Treatment in Muskoxen (Ovibos Moschatus)

Abstract

Contagious ecthyma (CE) has been a frequently occurring disease in captive Norwegian muskoxen (Ovibos moschatus), inflicting heavy losses among calves and adult males; adult females, however, have been little affected. Parapox virus particles from papilloma tissue were observed by transmission electron microscopy. Papilloma tissue excerted a typical cytopathic effect on human continuous lumar cell line. Sera from infected muskoxen contained antibodies reacting with virus antigen from muskoxen papilloma tissue in a complement fixation test. In animals already affected, papilloma tissue was surgically removed at intervals and the lesions injected with active papilloma tissue homogenate emulsified in Freund’s complete adjuvant (FCA). Serum antibody titers against CE virus increased 3 times in response to this treatment which reduced papilloma growth, but recovery was slow in adults and all but 1 calf succumbed when offered this treatment only. Isolated purified X-ray inactivated CE virus in FCA injected s.c. 4 weeks post partum was first attempted as a vaccine against CE. This treatment increased serum CE-antibody level, but did not prevent CE in calves experimentally injected with live CE virus. The incubation time of CE in this experiment was 20 days. Adequate protection was, however, obtained with a vaccine consisting of homogenated, glutaraldehyde inactivated, muskox papilloma tissue in FCA injected s.c. 2 weeks post partum. It is assumed that this protection was due to activation of both humoral and cellular immune mechanisms.