Adopted by the AZA Board of Directors 1997, Incorporated into the Accreditation Guidelines in 1998
Submitted by the Animal Health Committee, R. Eric Miller, DVM, Dipl. ACZM, Chairman
every contact with other living organisms, whether it be with humans or
other animals, carries some risk of disease transmission. Diseases that
are spread from animals to humans are called zoonoses (adj. = zoonotic
diseases). Responsible zoos should and do make reasonable attempts to
limit the risk of the spread of disease from the animals in their care
to their employees and to the general public (4,9). For the general
public, the risk of contracting disease from most zoo animals is minimal
to nonexistent due to their distance and isolation from the animals.
However, contact areas for the general public can present increased
risks that can be controlled with reasonable precautions. For this
paper, contact areas refers to those areas in which there is direct
physical contact between animals and people. These precautions are most
effective when they are part of an overall preventive medicine program
for the zoological park (5,8).
Risks of zoonotic disease can be
markedly reduced by avoiding direct animal contact. However, this
foregoes many valuable educational experiences and the establishment of a
direct relationship between animals and the public. A reasonable
alternative is adequate hand washing for those in direct contact with
the animals. Hand washing is perhaps the single most effective personal
hygiene procedure for reducing the risk of infection (4). Given that
fact, all areas in which the public has direct contact with animals
should have access to hand washing facilities that are in the immediate
vicinity of the contact (or an equivalent; e.g., bacteriocidal
As outlined by the AZA and the USDA’s Animal
Welfare Act, animal contact areas should always be supervised by a
trained zoo representative. Obviously, animals that are ill, should not
be used. Human food consumption should not occur in the immediate area
of contact. Additionally, zoological institutions should be aware that
the Centers for Disease Control (CDC) standards advise additional
precautions may be necessary for humans that they classify as at
increased risk of disease, including those that are immunocompromised.
When a reportable disease is identified, all appropriate local, state,
and federal regulatory officials should be contacted.
detailed information on zoonotic diseases may be obtained from a variety
of veterinary and medical textbooks and journals, (1,6) and from public
health officials. Additionally, the AZA’s Quarantine Protocol provides
further testing recommendations (7). Also referenced at the end of this
report is a review of some of the risks associated with animals and
immunocompromised humans (3). Following is a list of disease
considerations and control programs recommended for animals commonly
used in contact programs. Depending on the disease and history of the
animals, testing protocols may vary from an initial or incoming
quarantine test, to yearly repetitions. This protocol should be at the
discretion of the institutional veterinarian.
Reptiles and Amphibians
notable among the disease risks presented by reptiles is the
transmission of Salmonella sp. Salmonellosis is a common and often
nonpathogenic infection of reptiles (in one survey, according to
species, the infection rate ranged from 3 to 55 percent) (2). Diagnosis
may be difficult. A cloacal swab or other sample positive on culture for
Salmonella sp. is diagnostic for infection. However, due to
intermittent fecal shedding of these organisms, false negative cultures
frequently occur. So it is difficult, if not impossible to ascertain
with certainty that an animal is Salmonella "negative." Therefore, all
reptiles should be treated as salmonella carriers. Attempts to eliminate
Salmonella carriers with antibiotic therapy have been unsuccessful and
may be contraindicated as they can lead to chronic carrier states and
increased resistance of these bacteria to antibiotics. Risks of
transmission can be reduced in two ways: 1) avoid all direct contact
with reptiles or surfaces with which they have come in contact, or, 2)
allow only supervised contact followed by hand washing as previously
Reptiles can also transmit a variety of other
organisms, mostly gastrointestinal in origin, and the same procedures
described above should be effective in reducing the risks of
transmission to those in contact. These other risks include other gram
negative bacterial infections. Reptiles used in contact areas should be
free of snake mites and pentastomids (e.g., Armillifer sp.).
Amphibians may present several of the same zoonotic risks as reptiles, so again, contact should be followed by hand washing.
used in contact areas should be free of chlamydiosis and zoonotic
parasites (e.g., giardia). Chlamydiosis testing is appropriate for
members of the orders Psittaciformes, Galliformes, and Columbiformes. As
in reptiles, salmonellosis can be present and difficult to diagnose and
so, birds should be treated as suspects. In the general human
population, avian tuberculosis is generally considered to have very low
zoonotic potential, however, it can present significant risks for
immunocompromised individuals. Care should be taken to avoid public
contact with known infected flocks.
mammals are considered at risk for infection with rabies. Current
rabies vaccines are licensed for use in only six domestic species: dogs,
cats, ferrets, sheep, horses, and cows. For wild-caught individuals of
most species, a prolonged (three-six month) quarantine is necessary to
reduce the risk that they are infected with the virus. Even then, some
species such as skunks, foxes, raccoons, and bats may still represent a
greater risk. Any skin lesions compatible with dermatomycosis
("ringworm") should be carefully evaluated in order to prevent
transmission to those in direct contact with them.
extensive testing has been performed for a variety of viral, parasitic,
and bacterial diseases, all direct public contact with primates should
be avoided. Public contact also places the primates at considerable risk
of contracting diseases from humans.
Mammals: Small Ruminants/Neonatal Ruminants
small ruminants; e.g., pygmy goats, sheep, dwarf cattle, llamas, etc.,
that are greater than six months of age and used in contact areas should
be tested for tuberculosis, brucellosis, and leptospirosis. Obviously,
any animals with lesions compatible with sarcoptic mange (mange mite =
Sarcoptes scabeii) should be removed from contact. Any animals with
lesions compatible with contagious ecythema ("orf" in man) should be
tested and removed from contact until proven negative. Calves should be
checked and found free of Cryptosporidium sp. And other infections with
protozoa. Other diseases of a potential zoonotic nature include
infection with Coxiella burneti (Q-fever) in endemic areas.
Additionally, recent reports indicate that infection with Johnes disease
(Mycobacterium paratuberculosis) may present zoonotic concerns,
primarily in goats.
animals should be checked for gastrointestinal infection with
Balantidium sp. efforts made to control this infection. Additionally,
consideration should be given to regular vaccination for the bacterial
disease, Erysipelothrix rhusipathae ("diamond skin disease").
Mammals: Small Carnivores
general, due to the potential for bites, small carnivores should be
used in contact areas only with extreme caution. Due to the risk of
bites, small felids are generally not used in direct contact. If they
are, care must be taken that such animals are negative for infection
with Toxoplasma gondii. All carnivores should be tested for and be free
of zoonotic species of roundworms such as Baylascaris sp. Small
carnivores (e.g., raccoons and skunks) obtained from the wild may
present a greater risk of rabies and their use should be avoided in
Mammals: Rodents and Lagomorphs
using rodents and lagomorphs in contact areas, consideration should be
given to the risk of bites, past history, and exposure to hantavirus,
salmonella, and tularemia.
At the present time, CDC regulations effectively prohibit the use of bats in direct contact areas.
to the potential for infection with atypical mycobacteria, Vibrio sp.,
Erysipelothrix rhusiopathae, and a variety of gram negative bacteria,
contact with fish or touch tanks should also be followed by hand
It is important to
evaluate the risks of zoonotic diseases in a rational context. Contact
animals can provide a valuable educational experience for visitors and
participants in public programs to zoological parks and aquariums. Most
zoonotic diseases of concern in public areas can be prevented with
reasonable testing and quarantine programs and proper hand-washing
techniques. These are intended to be general guidelines and the
risk of diseases can vary by area, so each zoological institution should
develop its own zoonoses control program. Two excellent resources for
reviewing testing and preventative procedures for many of these diseases
are the American Association of Zoo Veterinarians’ Infectious Disease
Notebook, (1) and the American Veterinary Medical Association’s Zoonoses
Updates.( 6) In summary, the most effective method for disease
prevention is a complete and thorough veterinary program and common
sense sanitary measures.
Amand, W: Infectious Disease Reviews, American Association of Zoo Veterinarians, Media, Pennsylvania, USA, 1993.
RC, DE Green, EE Smith, RJ Montali, M Bush: Salmonellosis and
arizonosis in the reptile collection at the National Zoological Park. J
Am Vet Med Assoc 177:800-803, 1980.
Greene, CF: Pet ownership
for immunocompromised people. In Bonagura, JD (Ed.) Current Vet. Therapy
XII, W.B. Saunders Co., Philadelphia, Pp. 271-276, 1995.
W., C. Bredeson Heuschele: Zoonotic disease - reducing the risks. In:
1988 Proceedings of the American Association of Zoological Parks and
Aquariums, Bethesda, Maryland, Pp. 591-598, 1988.
Preventive medicine recommendations. In Amand, W (Ed.): Infectious
Disease Reviews, American Association of Zoo Veterinarians, Media,
Pennsylvania, USA, Section 1, 1993.
Leveque, NW (ed.): Zoonosis updates. American Veterinary Medical Association, Schaumburg, Illinois, USA, 1995.
RE: Quarantine procedures for AZA-accredited zoological parks. In: 1995
Proceedings of the American Association of Zoo Veterinarians, Media,
Pennsylvania, Pp. 165-172, 1995.
Miller, RE: Veterinary services
in zoos and aquariums. In Wylie, D (ed.), Zoo and Aquarium
Fundamentals, Association of Zoos and Aquariums, Bethesda, Maryland,
Shellabarger, WC: Zoo personnel health program
recommendations. In Amand, W (Ed.): Infectious Disease Reviews, American
Association of Zoo Veterinarians, Media, Pennsylvania, USA, Section 7,