Health Risks of Non-Human Primates

 

The following is a sample of health problems associated with nonhuman primates. It is not an exhaustive list. Some of these problems occur rarely, while others pose a significant health risk. Given our genetic closeness, there is always the possibility of transmission from human to nonhuman primate or from nonhuman to human. This is just a brief account, to educate and raise awareness of this issue - to learn more about any of these, including symptoms and treatment, and to find references, visit the sources at the end of these lists.

OW = Old World Primates; NW = New World Primates
transmission = common mode of transmission

Bacterial Diseases

There is little difference in susceptibility to this type of disease between most primate species; however, macaques are more susceptible to tuberculosis and enteric bacteria, while NW primates are more susceptible to the water-borne agents (Pseudomonas or Klebsiella.) The bacteria that deserve the most concern are Mycobacteriaciae (responsible for tuberculosis,) Shigella/Salmonella, Campylobacter, and Klebsiella.
  • bordetellosis - OW or NW
    transmission: respiratory
  • branhamella catarrhalis - "bloody nose syndrome" in cynomolgus macaques
    transmission: aerosol
  • campylobacteriosis - OW or NW; asymptomatic carriers are common; one of the leading causes of diarrhea in human beings
    transmission: oral
  • escherichia coli -
    transmission: fecal-oral
  • heliobacteriosis - OW, prevalent in rhesus stomachs
    transmission:oral
  • klebsiella - OW or NW; primarily opportunists affecting primates that have a lowered resistance, for example, those with inadequate nutrition. An infected primate poses threat to human infants or children with a mild respiratory infections - reduced level of health can increase liklihood of infection. Klebsiella is present in stagnant water, dirty drinking receptacles, soil, and as flora of the alimentary tract.
    transmission: respiratory - carried in nose and throat
  • leprosy - Normally OW, but limited to certain species, like mangabeys, others may be resistant
    transmission: respiratory, possibly skin
  • listeriosis - widespread in the environment
    transmission: oral from contaminated food, transplacental
  • pseudomonas spp. - P. aeruginosa and P. pseudomallei; human mortality from P. pseudomallei is about 80%
    transmission: P. aeruginosa ubiquitous is in moist environments worldwide. P. pseudomallei is an environmental saprophyte in SE Asia
  • salmonellosis/shigellosis - caused by separate organisms, but signs, symptoms, and treatment are similar; both are frequently present in the alimentary tract of nonhuman primates; Shigellosis is a significant zoonotic disease that has frequently been transmitted from non-human primates to man.
    transmission: fecal-oral; humans can be carriers of shigellosis, with no symptoms; spreads in monkey colonies via feces - carriers are common and can constitute the majority of animals in a colony. Stress can bring on disease.
  • staphylococcus
    transmission: commonly carried asymptomatically in the nose and throat but occasionally infects breaks in the skin and invades the bloodstream
  • streptococcus (diplococcus) pneumoniae
    transmission: respiratory
  • tetanus - OW or NW
    transmission: soil organism and an obligate anaerobe that contaminates wounds and causes postpartum infections.
  • tuberculosis - OW or NW, NW more resistant than OW; caused by mycobacteria; recognized as a common disease of captive primates for many years; not a disease of wild monkeys - caught from humans; in nonhuman primates the signs of TB may be hard to see - only slight behavioral changes noticed, followed by anorexia and lethargy. Often animals die suddenly while appearing to be in good condition.
    transmission: respiratory, oral
  • yersiniosis - OW or NW
    transmission: wild birds and rodents are reservoir hosts - ingestion of feed contaminated by feces of infected vermin

Fungal Diseases

Several reports have been made on systemic and superficial mycoses in primates. Fortunately, these are isolated cases; however, there is a potential danger to human beings. The primary pathogens are Dermatophilus congolensis (streptothricosis,) Candida albicans, and Trichophyton mentagrophytes (ringworm.)
  • blastomycosis - OW or NW
    transmission: inhalation
  • candidiasis - OW or NW
    transmission: ubiquitous organism - opportunistic infection of immunocompromised, usually a secondary disorder
  • coccidioidomycosis - OW or NW; limited to arid regions of North & South America
    transmission: inhalation of spores
  • cryptococcosis - OW or NW
    transmission: inhalation
  • histoplasmosis - OW
    transmission: inhalation of spores of H capsulatum from soil rich in bird or bat excreta. H. duboisii may be spread by dermal contact and may have a long incubation period.
  • pneumocystis - OW or NW
    transmission: aerosol
  • ringworm - OW or NW
  • streptothricosis - OW or NW, natural disease has been reported in Aotus and Lagothrix, and experimental infection was in rhesus, cynomolgus, and squirrel monkeys

Parasites

In the wild, many primates scavenge about villages and share not only food but also the parasites of the human inhabitants. Danger from imported animals, therefore, is usually during the first few months after the animal's arrival in the country. If the parasites are effectively eliminated during the initial quarantine adaptation period, the danger of transmission can be eliminated. The most serious danger that arthropods pose is their role as an intermediate biological host for parasitic diseases and as a mechanical vector for infectious organisms. Parasites that need an intermediate host are self-limiting but those having a direct cycle become a continual problem. These include protozoa, nematodes, tapeworms, and arthropods. Possible human infection from primate carriers is a constant threat.
  • acanthocephala - thorny-headed worms - NW
    transmission: ingestion of intermediate host (cockroach, beetle)
  • anatrichosoma - OW
    transmission: unknown
  • athesmia - common in NW
    transmission: mollusk is intermediate host
  • cestodes - (tapeworms) - OW or NW; only one (Hymenolepsis nana) of the variety of cestodes is considered a threat to humans
    transmission: ingestion of eggs or infected intermediate host
  • cutaneous mites - OW or NW
    transmission: contact
  • filarids - NW or OW, most common in NW
    transmission: blood sucking insects
  • lice - OW or NW
  • lungworms - most common in NW
    transmission: larvae passed in feces
  • nochtia - OW (primarily Asian macaques)
    transmission: oral
  • oesophagostomum - nodular worms - OW
    transmission: oral
  • pentastomes - OW or NW
    transmission: oral
  • physaloptera
    transmission: ingestion of intermediate host (cockroach)
  • respiratory mites - normally OW
    transmission: unknown, close contact required
  • schistosoma - OW or NW
    transmission: snail is intermediate host
  • strongyloidiasis - (nematodes) - NW or OW, common in many species of nonhuman primate and, because of its direct life cycle, can be infectious for humans. There are three species
    transmission: oral, skin penetration
  • trichuris - whipworms - OW or NW
    transmission: oral

Protozoan Parasites

Many protozoa require arthropod vectors; with vector control, they do not cause a significant problem to man outside the environmental range of the arthropod. Giardia and Entamoeba histolytica are the two primary pathogens not requiring an arthropod vector. Although plasmodia cause malaria, a disease of major importance, they are usually specific for each primate except in experimental situations and are rarely transmitted between nonhuman primates and humans in North America.
  • amoeba - OW or NW - amebiasis is a severe disease of human and nonhuman primate
    transmission: oral
  • balantidium - OW or NW; distributed worldwide, common in swine. Humans, great apes, & several monkey species may carry it.
    transmission: oral - ingestion of cysts or trophozoites from infected animal or human feces. Contaminated water or food.
  • cryptosporidiosis - uncommon
    transmission: fecal-oral
  • encephalitozoonosis - NW
    transmission: oral, transplacental; organisms shed in urine
  • giardiasis - asymptomatic carriers are common; dogs and NHP's represent the greatest public health risk. Most common intestinal parasite of people in the U.S., becoming a frequent cause of recurrent diarrhea in man and nonhuman primate
    transmission: fecal-oral
  • hepatocystis - OW
    transmission: midge
  • malaria - OW or NW
    transmission: mosquito
  • sarcocystis - infects many species of wild-caught monkeys
    transmission: fecal-oral
  • toxoplasmosis - NW more susceptible than OW. Usually asymptomatic in OW.
    transmission: ingestion of food contaminated by cat feces containing oocysts or ingestion of raw meat containing cysts (example: rodents); rare but usually fatal
  • trichomoniasis - OW or NW
    transmission: fecal-oral
  • trypanosomiasis - OW or NW; trypanosoma is commonly found in the blood of South American primates, but the only one known to be pathogenic is T. cruzi. Monkeys could be reservoirs for human infection. T. cruzi is an important cause of human disease (American trypanosomiasis)
    transmission: insect vector

Viral Diseases

These are probably the most dangerous diseases, because they are so difficult to diagnose and treat. A virus may be latent in one species of primate, with little or no symptoms, yet be fatal in another species of primate, including humans.
  • adenovirus - (numerous) - normally OW
  • benign epidermal monkey pox - (tanapox, OrTeCa pox) - unrelated to smallpox - OW, infects macaques and humans - rare
  • callitrichid hepatitis - NW, marmosets and tamarins
    transmission: rodents - endemic in mice worldwide. May be spread by feeding pinkies.
  • cytomegalovirus - normally OW, widespread latent infections in macaques
    transmission: horizontal (shed in urine), transplacental, highly species-specific
  • encephalomyocarditis virus - OW or NW
    transmission: oral, perhaps other - probable rodent reservoir
  • Epstein-Barr virus
    transmission: contact
  • focal epithelial hyperplasia of chimpanzees
    transmission: close contact
  • hepatitis a virus - NW or OW; nonhuman primates usually do not show symptoms but can be carriers
    transmission: fecal-oral
  • hepatitis b virus - OW
    transmission: infected blood, saliva, semen. Parenteral inoculation or intimate contact required.
  • hepatitis c virus - only chimps and humans
  • herpesvirus ateles - NW, spider monkey is natural host
  • herpes b - NW or OW, especially Asian monkeys, particularly macaques; monkeys are probably infected for life and a high proportion (perhaps 100%) of adults in infected colonies harbor the virus; the reliability of negative test results has not been ascertained - it is not certain that infected monkeys always have diagnostic titers. Infected monkeys can appear normal, showing no symptoms. The virus remains latent and may reactivate spontaneously or in times of stress resulting in virus shedding
    Since there is a high percentage of infection in monkeys yet relatively few human cases, risk of acquiring infection appears to be low. Through 1987, 22 human cases were reported. A few other cases are attributed to B virus infection, but lack adequate documentation. Twenty of the 22 human patients developed encephalitis. Fifteen of these died. Monkeys may shed the virus infrequently. It may also be possible that some humans are asymptomatic carriers.
    transmission: bites, scratches, venereal, aerosol
  • herpesvirus saimiri - (Cebid herpesvirus 2) - usually NW, squirrel monkey is natural host
    transmission: oral
  • herpes simplex virus - OW or NW
    transmission: latent or active infection in many humans, which are the natural reservoir. Human to monkey and monkey to monkey transmission from active lesions.
  • herpesvirus tamarinus - (Cebid herpesvirus 1) - NW, squirrel monkey is natural host (usually will show no symptoms); severe disease occurs in marmosets and owl monkeys
    transmission: contact, fomites, aerosol
  • Marburg virus - OW or NW; ; similar to ebola virus; first recognized in 1967 - lab workers in Germany and Yugoslavia working with tissue cultures from African green monkeys (vervets) from Uganda - seven out of the thirty affected died
    transmission: aerosol, handling infected tissue, saliva, urine
  • measles - NW or OW, most frequently reported viral disease of nonhuman primates; NW are more resistant than old world monkeys but exhibit high mortality when infected
    transmission: Virus is excreted from the mucous membranes of the eye and pharynx and later from the respiratory and urinary tracts. Highly contagious. It can spread from human to monkey, human to human, and monkey to human.
  • molluscum contagiosum - OW, humans and chimps - poxvirus unrelated to smallpox
  • monkeypox - OW or NW - most frequent pox virus, related to smallpox and vaccinia; Occurs sporadically, not epidemically
    transmission: Zoonotic disease of monkeys and humans in tropical rain forests of western and central Africa. Old and New World monkeys and apes also susceptible. Animal reservoir unknown, but possibly squirrels and probably not monkeys.
  • papillomavirus
  • rabies - NW or OW; 16 cases have been confirmed in nonhuman primates, including chimpanzees, cebus, cynos, and squirrel monkeys. All source countries of NHP's have endemic rabies. The vaccination of wild animal pets for rabies is discouraged by health authorities - modified live vaccines for dogs and cats can cause rabies in the nonhuman primate, can only use killed vaccines, the efficacy of which is not known.
    transmission: virus laden saliva via bite, scratch, or abrasion. Rabid animals may shed virus in saliva 1-14 days before showing signs
  • simian agent (SA8) - OW, especially Papio sp. and vervets
    transmission: venereal
  • simian ebola-like filovirus - OW; fatal in some monkeys, humans can be infected but do not get ill
    transmission: aerosol
  • simian hemorrhagic fever virus - OW, primarily patas monkeys
    transmission: endemic in some wild patas hosts remain persistently viremic, but asymptomatic for life. Animals may be viremic without antibody. Transmission from patas to macaques appears to require parenteral exposure to blood or body fluids. The virus spreads much more readily among macaques by contact or aerosol. Nearly always fatal in macaques.
  • simian varicella virus - OW - group of closely-related herpesviruses
    transmission: respiratory - latency is common and the origin of some outbreaks is unexplained
  • SV40 - OW, primarily macaques
    transmission: respiratory, virus shed in urine
  • yaba pox - OW, natural infections have occurred in rhesus and baboons; not presently understood; may be a natural indigenous infection of wild African primates. Humans are also susceptible
    transmission: obscure, but experimentally can be done by aerosol, direct inoculation; mosquitoes have also been implicated
  • yellow fever - NW, especially Alouatta spp. - disease of Central and South America and Africa, OW also suspectible
    transmission: mosquitoes in urban areas, in the wild many mammals are natural hosts

Primate Retroviruses

Family: Retroviridae
  • Subfamily: Lentivirinae (immunodeficiency viruses) - OW
  • Subfamily: Oncovirinae - OW or NW - usually no disease in natural host species but may cause natural or experimental disease in other species
  • Subfamily: Spumavirinae - (foamy viruses) - mainly OW