Monkey Business – sharing disease

Humans and monkeys have shared and competed in the same environments, though not always to the benefit of monkeys.  In an interesting form of retribution for killing and eating monkeys, humans may have acquired the simian immunodeficiency virus (SIV) which mutated into HIV.

Although the earliest evidence of HIV was traced to about 60 years ago, a new study in Science as reported by the New York Times, suggests that monkeys may have harbored SIV for over 30,000 years. The Times notes that scientists have questioned …

What happened in Africa in the early 20th century that let a mild monkey disease move into humans, mutate to become highly transmissible and then explode into one of history’s great killers, one that has claimed 25 million lives so far? Among the theories different researchers have put forward are the growth of African cities and the proliferation of cheap syringes.

HIV is not the only health problem humans and monkeys share. Erma Sulistyaningsih and colleagues are among the most recent to address the problem of Plasmodium knowlesi, acquired from monkeys when tourists among others visit forests as a possible fifth form of human malaria in southeastern Asia including Indonesia, Malaysia, Vietnam,  the Philippines and recently in Myanmar.

There is also … “the theory of P. vivax originating in macaques in Southeast Asia and the close relationship to other primate malaria parasites.” Studies in Brazil also show that monkeys could serve as reservoirs for P vivax.

Researchers have also been exploring the “co-speciation hypothesis” in the relationship between P. reichenowi in chimpanzees and P. falciparum in humans. Hughes and Verra concluded that, “The available data are thus most consistent with the hypothesis that P. reichenowi (in the strict sense) and P. falciparum co-speciated with their hosts about 5–7 million years ago.”

Then last year Medical News Today reported that, “Researchers based in Gabon and France report the discovery of a new malaria agent infecting chimpanzees in Central Africa. This new species, named Plasmodium gaboni, is a close relative of the most virulent human agent P. falciparum.”

The authors of the Gabon study warn that, “The risk of transfer and emergence of this new species in humans must be now seriously considered given that it was found in two chimpanzees living in contact with humans and its close relatedness to the most virulent agent of malaria.” Similarly other researchers have expressed concern that, “Finally, our data and that of others indicated that chimpanzees and bonobos maintain malaria parasites, to which humans are susceptible, a factor of some relevance to the renewed efforts to eradicate malaria.”

Hence we see the lesson. In all our efforts to eliminate malaria, we do not want to monkey around with other possible reservoirs of infection.  Capacity to monitor our simian cousins is a key element in eventually ridding humans of the malaria parasite.

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