The vaccination of wildlife has become a very common procedure in South Africa, especially in privately owned herds where the farmer has paid a lot of money to acquire these animals. In high-risk areas where anthrax and botulism is a problem farmers will vaccinate endangered and expensive species annually. Breeders of the wild carnivores keep these animals in small camps and vaccinating these animals has become routine.
Anthrax (Bacillus anthracis):
Sterne 34F2 spore vaccines are recommended for use in wildlife. These vaccines contain the uncapsulated avirulent strain of Bacillus anthracis. Onderstepoort Biological Products produces the vaccine “Anthrax”. Intervet produces “Anthravax” for protection against anthrax only; “Blanthrax” for protection against anthrax and blackquarter (Clostridium chavoei) and “Supavax” for protection against anthrax, blackquarter and botulism (Clostridium botulinum). “Supavax” is probably the most widely used in free-ranging animals and most commonly administered through the use of dropout darts. These vaccines are contra-indicated for use in pregnant animals but this is very difficult to determine in wild animals without immobilising them. The risk of fatal disease outweighs the risk of abortion in pregnant animals, especially in endangered or very expensive species. The vaccine is normally administered during the winter or early spring. Animals being translocated from areas where no anthrax has been reported to high-risk areas should be vaccinated at least 3 weeks prior to release. This is however not practical and seeing that most of the wildlife are captured and translocated during the winter period, vaccination at the time of capture is absolutely necessary. A booster vaccination four to six weeks later is ideal but not always practical but in very rare and expensive animals it should be considered. No antibiotics should be used in conjunction with live vaccines as this will interfere with the development of immunity.
Only two inactivated rabies vaccines are registered for use in wildlife. “Rabisin” (Merial) as well as “Imrab 3” (Phizer). Only inactivated vaccines should ever be used. The vaccine should be given subcutaneously or intramuscularly. The animals could be restrained in a crush cage, e.g. cheetahs in captivity or the animals might need to be immobilized, e.g. lions. Dropout darts could be used in carnivores but there is a risk that the animals might ingest the dart. If there is an outbreak of rabies or a high incidence in an area, it might be considered to vaccinate some of the more expensive or endangered herbivores by use of dropout darts. A recombinant vaccine, making use of the rabies glycoprotein (VRG) has been used as an oral vaccine with great success in many species. When administered orally (directly or in bait) to young and adult animals, VRG elicits high titres of virus-neutralizing antibodies and produces protection against severe rabies challenge. No abortifacient, teratogenic, or oncogenic side effects have been noted. Other modified live rabies vaccines for oral administration are available (SAD B19 and SAG-1). The safety of these vaccines in non-target species is however questionable as reversion to virulence in especially immunologically compromised individuals is possible.
The bacille Calmette-Guérin (BCG) is the basis of the vaccine most widely used in humans and domestic livestock. It is a Mycobacterium bovis isolate of low pathogenicity. It has shown variable results over the world but this is probably due to differences in dose and route of administration. Low-dose administration seems to result in better “immune-locking”, resulting in improved responses of the appropriate T lymphocyte population and in turn, better protection in cattle and deer. The administration of BCG to cattle, and in some cases of possums, via the oral, intranasal and intratracheal route, gave equal or superior protection in comparison with the subcutaneous route. Other vaccine candidates include M. vaccae that was given to badgers orally and showed promising results, as well as M. microti, the vole bacillus, which yielded results similar to the BCG vaccine. Tuberculosis is a controlled disease in South Africa and a test and slaughter program is in place. However in wildlife it has become a huge problem for example in Kruger National Park and Hluhluwe-Umfulozi Nature Reserve where there is a high incidence of the disease in the buffalo, kudu, lion and other populations. A test and slaughter program is not really feasible; therefore a lot of research is aimed at the moment at finding an effective vaccine.