Epidemiology of African horsesickness: antibodies in free-living elephants (Loxodonta africana) and their response to experimental infection

BARNARD, B.J .H., BENGIS, R.G. , KEET, D.F. & DEKKER, E.H. 1995. Epidemiology of African horse­ sickness: Antibodies in free-living elephants (Loxodonta africana) and their response to experimental infection. Onderstepoort Journal of Veterinary Research, 62:271-275 The presence of low levels of group- and type-specific antibodies against African horsesickness virus in the serum of some free-living elephants was reconfirmed. Experimental infection resulted in conflict­ ing results. No detectable viraemia nor virus could be demonstrated in the organs of the six elephant calves and none of them mounted significant levels of neutralizing antibodies against the virus. On the other hand, all calves showed a slight rise in ELISA tit res. This rise, however, was modest when com­ pared with the rise in experimentally infected zebra. The presence of low levels of group- and type­ specific antibodies in the serum of some free-living elephants is judged to be the result of natural hyper­ immunization due to frequent exposure to infected biting insects. Elephants should therefore, despite the presence of low levels of antibodies, be regarded as poorly susceptible and unlikely to be a source of African horsesickness virus.