Monkeys and apes have been used for biomedical purposes on an increasing scale during the last 40 years, but the greatest increase in recent years occurred as a result of the introduction of poliomyelitis vaccine. Monkeys have traditionally been used in large numbers for both production and testing of polio vaccine and continue to be used in many countries, even though diploid cells can replace monkey kidneys at the production stage, and the inactivated (Salk) vaccine does not require the monkey neurovirulence test.
The main source of monkeys and apes used in the laboratory has been wild populations, but although action has been taken to conserve stocks, some species are already in short supply and this source of supply cannot be relied upon in the future. Many primate species are caught by the shooting of mother primates so that their infants, who cling to their mother's dead body, can be easily caught. Primates caught by this method include gorillas, orang-utans, chimpanzees, gibbons, and many arboreal species. Many mothers and babies die for each baby ape successfully brought into captivity, and sometimes protective group members are also killed. Between trapping and receipt in the laboratory, many animals die and the tissues of many others have to be discarded owing to illness or infection. The animals may experience considerable pain and suffering during the experiments performed upon them and before they are finally discarded.
The greatest exploitation of any species of primates occurred during the 1950s when laboratories were racing to produce poliomyelitis vaccine using monkey kidneys. It was found convenient to use Rhesus monkeys from India. During the years of this boom about 2.5 million Rhesus monkeys were exported from India, mostly for vaccine production. For a time they left at the rate of 250,000 per year.
In 1968 it was estimated that total world trade amounted to 200,000 primates. The USA alone took 124,000 monkeys, 60% coming from Latin America and the remainder from Africa and Asia. In 1978, India entirely stopped export of Rhesus monkeys, after learning that monkeys exported from India were being used in warfare experiments by the USA military. In January 1979, Bangladesh stopped monkey exports for the same reason, as did Malaysia in 1984. Many countries feel that many of the uses to which primates are put overseas violate their religious traditions or national culture and principles.