Monkeys and AIDS


By Dr. Rohan H Wickramasinghe

A recent proposal in the Balangoda Council that it would be desirable to encourage the consumption of the flesh of monkeys has led to a certain amount of discussion in the Sri Lankan media. The comments this writer has seen have made no mention of the fact that convincing evidence has been found that the worldwide scourge of AIDS (‘acquired immunity deficiency syndrome’) was brought about following an initial infection with a HIV (‘human immunodeficiency virus’), which may originate at some point from ‘simian immunodeficiency virus’ (SIV) found in certain species of primates (which include monkeys and apes). The present note, based mainly on information found in authoritative reviews presented in sources such as in the invaluable Wikipedia, hopes to furnish a basic introduction on the subject to readers who are unfamiliar with the field and may be stimulated to read up more about it. Regrettably, very much has had to be left out as will be observed while perusing the specialist literature. Again, ‘conflicting’ or inconsistent findings have sometimes been found by workers in different areas of this field.

Types of HIV and SIV

There are several strains of HIV. Accounts of the various groups and types of HIV are given in some detail in many reviews. Various sub-groups of the virus became infective towards humans at different times.

Several HIV-1 groups are found in wild ape populations of West Central African forests. These are the chimpanzees (Pan troglodytes troglodytes) and western lowland gorillas (Gorilla gorilla gorilla). For instance, chimpanzees are found in the Cameroon, Republic of Congo and Gabon. Of the various groups, a pandemic group is the HIV-1M or Main. Another major group is HIV-1 O. It is believed that the chimpanzees get infected by SIVs when they feed on monkey flesh. A HIV-1C group may have its origins in the jungles of Argentina or Brazil. More research is needed on this area.

HIV-2 (groups A and B) are found in the Sooty mangabey monkeys (Cercocebus atys atys), e.g. of the Ivory Coast and Senegal. HIV-2 is less pathogenic than HIV-1 and the epidemics of HIV-2 (groups A and B) appear to have started spreading in humans in the Ivory Coast between 1905 and 1961.

The story begins

It has been observed that a) SIV pathogenicity could exist in primates and not be recognized due to lack of long-term studies, b) SIV may have infected monkeys in an island off Cameroon for at least 32,000 years, c) a recent Czech study of the genome of the Malaysian Flying Lemur (Galeopterus variegatus), which shares an immediate common ancestor with primates, found endogenous viruses of the genus (lentiviruses) to which HIV belongs, that had emerged about 40 to 60 million years ago.

Zoonoses are diseases which pass from animals to humans. Examples are rabies, Ebola virus disease, bird flu and salmonellosis. HIV was a zoonosis in the early 20th century but is now readily transmitted from human to human. Many investigations have focused as to when the virus may have evolved/jumped from a primate (e.g. chimpanzee) to human. This is termed the ‘most recent common ancestor’ (MRCA). The various studies reported, for instance, that a) the global pandemic of the HIV-1M group dates back to the city of Leopoldville in the Belgian Congo (now Kinshasa of the Democratic Republic of Congo) in the 1920s, b) the MRCA (jump from chimpanzee to human) occurred between 1915 and 1941, c) a biopsy made in Kinshasa in 1960 suggested an MRCA (HIV-1M) between 1873 and 1933 and d) another study arrived at an estimate of the date of transmission at around 1915 and 1931. While discrepancies exist between the results reported by different groups of researchers they generally help towards the resolution of earlier uncertainties.

Transmission of AIDS to humans

(In the early years of the AIDS pandemic of the 20th century, there was speculation that the HIV virus may be transferred to humans during sexual activity with animals. This has subsequently been firmly discounted irrespective of the species of the animal.) There are several ways by which the HIV virus may be transmitted to or between humans. These include 1) contamination from or contact with meat, blood or other tissues during hunting or butchering, 2) sexual activity between humans, 3) medical and surgical procedures, including blood transfusions, 4) use of blood products (such as infected blood plasma by haemophiliacs), 5) from mother to child (before, during or after giving birth or during breast feeding), 6) using non-sterile injection needles (e.g. needles shared by heroin addicts) and 7) injection or vaccination campaigns.

Stages of HIV infection

These are 1) symptoms of acute infection (which is, also, called primary infection), which can last for several weeks, 2) the latency stage involving few or no symptoms and can last anywhere from two weeks to twenty years or more and 3) AIDS, the final stage of HIV infection accompanied by, among others, assorted opportunistic infections, such as the rare lung infection, Pneumocystis carinii pneumonia (PCP), wasting disease and cancers, such as the usually uncommon Kaposi’s sarcoma. It should be noted that Pneumocystis carinii is now known as Pneumocystis jiroveci.

Development of the pandemic

A time line by Stephen Lynch in the New York Post of 22 February 2015 was based on David Quammen’s book, ‘The Chimp and the River: How AIDS emerged from an African Rain Forest" (W.W. Norton, 2015) and begins with one human being infected by the blood of one chimpanzee butchered in the Cameroon around 1908. (Another account (J. Pepin, ‘The Origin of AIDS’, Cambridge University Press, 2011) dates the infection of a Central African bush hunter as having taken place in 1921.) The infection of the hunter or butcher would require the presence of an open wound, cut or bite. The infection was passed from person to person down the Sangha River to Leopoldville (later Kinshasa) in the Congo. Life expectancy was not long in the region in that era and AIDS was not a recognized disease. The disease was transmitted both sexually as well as owing to the multiple use of reusable syringes.

A Haitian professional (e.g. a doctor or teacher) returning from working in the Congo carried the infection from the Congo to Haiti in around 1960. The disease was next carried from Haiti to the USA around 1966 by either one infected person or a batch of imported frozen infected blood plasma. The disease spread un-noticed in the USA from between 1969/72 till around 1980.

Occasional cases of AIDS would have resulted before 1970 but the current epidemic is believed to have taken off in the mid- to late-1970s. By 1980, HIV may have spread to North and South America, Europe and Australia, in addition to spreading in Africa. The spread in Africa would have been facilitated by factors which emerged in the colonial era, such as the rapid growth of cities (and development of urban prostitution availed of by the migrant men, who left their homelands in colonial times in search of employment), some breakdown of family structures and well developed railway, road and river links out of Leopoldville (now known as Kinshasa). Mass programmes for protection against certain diseases would have contributed. The coming of air travel and sex tourism facilitated the spread of HIV around the globe. Various other factors, such as genital ulcer disease (GUD, e.g. syphilis), also helped. It is surmised that some 100,000 to 300,000 people may have been infected by 1980. As yet, however, the infection had yet to be identified and recognized as a disease.

Identification of a disease

In 1981, a few cases of the uncommon lung infection, PCP, were reported from Los Angeles and some in California and New York of Kaposi’s Sarcoma. In December 1981, cases of PCP emerged among people using shared heroin injection syringes. By the end of the year, of 270 cases of severe immune deficiency among gay men 121 had died. Due to the high incidence of immune deficiency among gay men in Southern California, the syndrome was given the name, ‘gay-related immune deficiency’ or GRID. (Some also called it the ‘4-H disease’ since those suffering from it were frequently homosexuals, heroin addicts, haemophiliacs or Haitians.) However, in September 1982, the Centre for Disease Control and Prevention (CDC) of the US gave it the name ‘acquired immune deficiency syndrome’ (AIDS), which received general acceptance. In 1982, cases were reported in 17 U.S. states and 5 European countries.

From then on the numbers started to climb and by 1991 there were 10 million people estimated to be HIV- positive worldwide. For the year 1999, the numbers of AIDS-related deaths stood as 1.4 million and the new HIV infections were 3.3 million. Such figures commenced to drop with the discovery and introduction of new medicines.

Relevance for Sri Lanka

No research appears to have been conducted on the presence of SIV or HIV in Sri Lanka’s monkeys. It is, therefore, impractical to speculate on the possible dangers involved in the consumption of the flesh of these animals. It is interesting that ‘Balangoda Man’, who was named by archaeologist/anthropologist Professor P.E.P. Deraniyagala, has been reported by the archaeologist, Dr. Siran Deraniyagala, to have been in the habit of consuming the flesh of monkeys and other wildlife. Balangoda Man’s life span is believed to have been of the order of thirty five years. It is interesting to speculate as to whether AIDS was one of the stresses or ailments he would have been exposed to. It is unlikely that in that era AIDS epidemics would have occurred in Sri Lanka since they would have lived in small rather isolated communities and the likelihood of human-to-human transmission of the virus would be minimal. However, Dr. Siran Deraniyagala (‘The Prehistory of Sri Lanka’, Dept. of Archaeological Survey, Govt. of Sri Lanka, 1992) has noted that Veddahs, who are phylogenetic descendants of Balangoda Man from around 16,000 B P., may carry with them a piece of dried human liver to be chewed on to acquire the valour of the dead person; the preparation of the liver sample and subsequent actions may have resulted in human-to-human transmission of AIDS in a manner not previously reported in the literature.

It is said that the consumption of the flesh of monkeys and other species of wildlife does occur in rural areas in Sri Lanka in the present era. It is possible that if ill health is caused by, for instance, a Kaposi’s Sarcoma, it is not being recognized as being an outcome of contracting AIDS, particularly in view of the lengthy latency stage, which may run into years. It behooves us to be watchful as to this possibility. One recalls the adage that ‘Coming events cast their shadows before them’.

Further speculation as to whether consuming the flesh of Sri Lankan monkeys may lead to contracting AIDS should await a research programme on the presence or not of SIV and HIV viruses in these animals. Such a programme could include a study relating to the possible presence of HIV viruses in lorises.

Information Sources

There are several hundred publications (papers, books etc) in the fields covered in the above article. Space considerations do not permit the citing of details of even a small fraction of them. The following are among the easily accessible and authoritative links which may be consulted for further information:




Comments on this article would be welcome.

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