Expert: Jonathan Wright - 2/28/2005

Question
Can you tell me if monkeys are harmful or useful to man and do they have any enemies?

How do they protect themselves?

Thank you very much.

Answer
Dear Shirley-Ann

Thanks for your question. I assume you want information about African green monkeys, as opposed to all monkeys. As you will see below, the monkeys are both useful and harmful to people. The positive aspects include bushmeat and use in medical research, as well as, possibly, spreading seeds from their food items. Negative aspects include attacks on people or their crops and the spread of various illnesses, including viruses similar to the HIV and ebola viruses. I have tried to simplify my answers, but some of the websites are quite complicated. In fact - if you type 'African green monkey' into Google, you'll find more information about medicine and microbiology than about the monkeys in general, which is quite unusual for a mammal species.
  

People use dogs to hunt monkeys for bushmeat for home consumption and for the market stall. Then monkeys react with a soft cal, of a timbre difficult to distinguish against the background noise. Then the monkeys slip unobtrusively into the foliage of bushes.

African green monkeys can become severe agricultural pests to crops and orchards. Captive monkeys can become dangerous when older, perhaps biting and scratching people.     

Green monkeys are used in medical research.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1... concerns viruses in African green monkeys.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=190510&rendertype=abst... states that kidney cells of green monkeys can be used as hosts to cultivate influenza viruses to provide adequate quantities of the viruses to meet the vaccine requirements if there is an influenza pandemic.

http://www.microscopyu.com/galleries/fluorescence/cells/cv1/cv1.html concerns research into the Rous sarcoma virus (RSV) and its relationship to cancers and other diseases.

http://www.ippl.org/Jasmine.htm states that monkeys can carry diseases that can make humans sick or, at worse, can kill them. Monkeys can catch most human diseases.
http://www.sfbr.org/pages/news_release_detail.php?id=47 concerns work by Jonathan Allan to determine the link between African green monkeys and AIDS. Over 50% of the monkeys carry SIV – the simian version of HIV – yet never develop the disease. Allan says that they have a natural resistance to a virus that is deadly in humans. Many people believed that the monkeys' natural resistance to the disease stemmed from a heightened immune system that allows them to “keep the virus in check.” However, Allan's research showed the opposite to be true. He observed that many African green monkeys carry viral loads as high or higher than humans who have full-blown AIDS. The monkeys remained healthy while their immune systems posed little response to the infection.

Perhaps the most harmful effect the African green monkey has on people concerns its subdued Allan believes that the monkeys' more subdued immune response might actually be what saves their lives because, unlike humans, they are not sending too many immune cells to the “front lines” to be killed off by the virus. Still, he says, the fight against HIV requires a delicate balancing act. If the immune system is too weak, the patient will die of the AIDS virus. But, if the immune system is overactive, too many immune cells are exposed to the virus and the patient will die. Allan will be looking at why the monkeys can maintain high levels of SIV in the brain without developing neurological disease and hopes that this will help human sufferers with AIDS.

http://www.ksu.edu/research/comply/iacuc/occhs/fact29.html concerns the Marburg virus, also called African Hemorrhagic Fever, Green or Vervet Monkey Disease.  This virus is related to the ebola virus and is especially prevalent in African green monkeys.  People have died from the disease, due to exposure to tissue and blood from African green monkeys or secondary contact with infected humans. People who handle intact animals or who wear gloves and protective clothing when handling tissues do not seem to catch the disease. The disease is 100% fatal in experimentally infected African Green Monkeys, Rhesus, squirrel monkeys, guinea pigs, and hamsters. The signs of the disease include leukopenia and petechial haemorrhages, sometimes with GI haemorrhages. In humans there is a 5-7 day incubation period. Signs include headache, fever, muscle pain, vomiting, diarrhoea, hemorrhagic diathesis, conjunctivitis, photophobia, skin rash, and jaundice, leukopenia, thrombocytopenia and proteinuria. There is shock and death in 25% of cas and haemorrhages are found throughout the body on post mortem examination.

http://www.oaklandzoo.org/atoz/azvervet.html mentions that they have a variety of alarm calls, distinguishing between birds (which attack from above), snakes (which attack in the undergrowth) or mammals, such as leopards. When the monkeys see a leopard, they take flight into the trees, where they can be out of reach at the extreme tips of the branches, as these cannot support a leopard's weight. If the monkeys see an eagle, they leap down from the trees and escape in dense undergrowth. The monkeys avoid snakes if they see them before they strike. Baboons will take young monkeys separated from the group. Other mammalian predators include cats, jackals, hyenas and crocodiles. While the monkeys have powerful canines, they tend to flee rather than to attack predators.

I hope that this answers your questions.

All the best

Jonathan