Abstract
Malignant catarrhal fever (MCF) is a fatal disease of cattle that, in East Africa, follows contact with wildebeest excreting alcelaphine herpesvirus 1 (AlHV-1). Recently an attenuated vaccine (atAlHV-1) was tested under experimental challenge on Friesian-Holstein (FH) cattle and gave a vaccine efficacy (VE) of approximately 90%. However testing under field conditions on an East African breed, the shorthorn zebu cross (SZC), gave a VE of 56% suggesting that FH and SZC cattle may respond differently to the vaccine. To investigate, a challenge trial was carried out using SZC. Additionally three adjuvant combinations were tested: (i) Emulsigen®, (ii) bacterial flagellin (FliC) and (iii) Emulsigen®+bacterial flagellin. We report 100% seroconversion in all immunized cattle. The group inoculated with atAlHV-1+Emulsigen® had significantly higher antibody titres than groups inoculated with FliC, the smallest number of animals that became infected and the fewest fatalities, suggesting this was the most effective combination. A larger study is required to more accurately determine the protective effect of this regime in SZC. There was an apparent inhibition of the antibody response in cattle inoculated with atAlHV-1+FliC, suggesting FliC might induce an immune suppressive mechanism. The VE in SZC (50–60%) was less than that in FH (80–90%). We speculate that this might be due to increased risk of disease in vaccinated SZC (suggesting that the vaccine may be less effective at stimulating an appropriate immune response in this breed) and/or increased survival in unvaccinated SZC (suggesting that these cattle may have a degree of prior immunity against infection with AlHV-1).
Highlights
Malignant catarrhal fever (MCF), an often-fatal disease with a worldwide distribution, is caused by several g-herpesviruses and affects many species of even-toed ungulates including cattle, bison and deer (Russell et al, 2009)
Previous studies have shown that vaccinated cattle that subsequently succumbed to MCF exhibited a significantly increased alcelaphine herpesvirus 1 (AlHV-1) À specific antibody titre after challenge (Haig et al, 2008; Russell et al, 2012)
The calculated efficacy of the atAlHV1 + Emulsigen1 vaccine formulation following experimental virus challenge was 50% in this trial in which shorthorn zebu cross (SZC) cattle were used whilst it was 81.5% in the Russell trial in which FH were used. This was the first experimental trial to investigate the efficacy of a new immunization strategy against MCF in an East African breed of cattle
Summary
Malignant catarrhal fever (MCF), an often-fatal disease with a worldwide distribution, is caused by several g-herpesviruses and affects many species of even-toed ungulates including cattle, bison and deer (Russell et al, 2009). The disease ranges from the sporadic to epidemic and occurs following transmission from an unapparent carrier host to MCF-susceptible species. Defined by the reservoir species from which the causative virus arises, two major epidemiological forms of MCF exist, wildebeest-associated (WAMCF) (Plowright et al, 1960) and sheep-associated (SA-MCF) MCF (Reid et al, 1984). The clinical presentation is similar in both forms with affected animals suffering fever, oral epithelial lesions, corneal opacities, ocular/nasal discharge and, frequently, death.
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