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The close phylogenetic relationship between humans and great
apes means that there is avery high risk of pathogen exchange.
The emergence among humans of diseases carried by great apes
has been an unintentional effect of the hunting and butcher-
ing of the African great apes. Pathogen exchange has resulted
in outbreaks of some of the most lethal diseases among hu-
mans, including the Ebola virus and HIV/AIDS (Bailes
et al.
2003). Transmission of various other retroviruses has been
demonstrated and it is likely that through bushmeat hunting
and butchering other pathogens are being exchanged between
humans and apes, however systematic investigations have not
been carried out.
DISEASE THREATS AND ILLEGAL TRADE
Bushmeat hunters are at the highest risk during the butcher-
ing process, as they come in contact with the blood and or-
gans of freshly killed great apes (Wolfe
et al.
2005). Hunters
themselves frequently have lesions caused by their work in
the forest and the handling of machetes, leading to blood-
on-blood contact between humans and great apes. Transmis-
sion of pathogens from processed (smoked or cooked) meat
is also possible but depends largely on the stability of the
pathogen. Anthrax spores, for example, are extremely stable
pathogens and have been known to infect African great apes
in the wild (Leendertz
et al.
2006). Given the tremendous
costs associated with zoonotic diseases such as HIV/AIDS
in humans, limiting bushmeat consumption is an extremely
cost-effective means of combating such diseases, contribut-
ing to both the protection of great apes and the prevention of
diseases in humans.
Pathogen transfer goes both ways and bushmeat hunting
presents another, albeit less obvious, threat to wild great ape
populations. Infant or juvenile great apes captured during the
bushmeat hunt are illegally sold as pets, resulting in human
exposure to the pathogens carried by the apes, and ape expo-
sure to the pathogens carried by humans (Schaumburg
et al.
2012; Unwin
et al.
2012). These pathogens may cause acute
disease in the great apes, and while some may be treated, oth-
ers may persist over many years.
Once captured, the best scenario for the individual great ape
is to be confiscated at some point along the trade chain and
housed in a great ape sanctuary. Here, the animals obtain vet-
erinary care and are housed in social groups. However, many
sanctuaries are engaged in reintroduction programmes in ac-
cordance with international regulations that will return a por-
tion of these great apes to the wild. Such programmes are dif-
ficult and much-debated (Beck
et al.
2007). If confiscated apes
are released in areas already home to wild apes of the same
species and disease screening is inadequate, human patho-
gens may be introduced into the wild populations. The risk of
pathogen transfer creates new challenges for reintroduction
programmes and will lead to the exclusion of entire groups of
captive apes from such programmes.