Immunisation of cattle against the herpesvirus of malignant catarrhal fever: failure of inactivated culture vaccines with adjuvant.

Attempts were made to immunise cattle against the herpesvirus of malignant catarrhal fever by inoculating living or formalinised preparations of the agent, propagated in cell cultures and combined with Freund's incomplete adjuvant. High and persistent levels of virus-neutralising antibody were regularly demonstrable, especially following two intramuscular inoculations at an interval of six to eight weeks. In spite of this no protection was demonstrable against parenteral challenge with virulent virus, whether in cell-free or cell-associated form. In a controlled field trial vaccinated cattle showed no evidence of protection against natural challenge by exposure to wildebeest herds. It was concluded that humoral mechanisms are probably not important in determining resistance to infection with virulent MCFV.     

Improved isolation of rinderpest virus in transformed bovine T lymphoblast cell lines.

Bovine T lymphoblast cell lines transformed by the protozoan Theileria parva were compared with bovine kidney (BK) and Vero cells for their ability to isolate various strains of rinderpest virus from tissues and infected secretions. All of the strains of rinderpest virus that were tested, including attenuated cell-culture, caprinised and lapinised vaccines, and both mild and virulent pathogenic strains, readily induced syncytial cytopathic effect (cpe) in T lymphoblasts. The cpe could often be detected within one day of inoculation of lymphoblasts, whereas it took three to 14 days to appear in Vero and BK cells. Using lymphoblasts it was possible to reisolate rinderpest virus from nine of 42 swabs collected from three cattle experimentally infected with an isolate from a recent outbreak of mild disease whereas the same swabs yielded only one reisolate on BK cells. It was also possible using the lymphoblasts to detect infectious virus in the ocular, nasal and oral secretions of goats and rabbits infected with caprinised and lapinised virus, respectively. Peste des petits ruminants virus appeared to grow as rapidly as rinderpest virus in the lymphoblasts whereas canine distemper virus readily induced cpe on first passage but less readily on subsequent passage. Measles virus induced relatively little cpe when inoculated into lymphoblasts and did not appear to passage in these cells. The lymphoblasts are easy to maintain in culture and since they rapidly recovered 11 isolates from 37 diagnostic samples could prove useful in laboratories carrying out rinderpest diagnosis.