Because infectious diseases of domestic animals also occur in wild animals, vaccination of captive exotic mammals is often desirable. However, commercial vaccines are tested and approved for use only in domestic species; therefore, recommendations for use in exotic mammals tend to be based on limited published data and anecdotal experience (see Vaccinations Recommended for Exotic Mammals).
For safety reasons, inactivated viral or bacterial vaccines are preferable to modified live virus (MLV) vaccines. Although MLV vaccines are usually avirulent in domestic counterparts, they may retain the ability to cause disease in some exotic species. This is especially true for rabies and distemper vaccines. In some cases MLV vaccines may be recommended in exotic species, based on considerable experience in zoos, with satisfactory safety results and limited serologic data; however, studies evaluating protection against virulent virus challenge are rarely done. Recently developed distemper vectored vaccines such as those in canarypox vectors appear to be both safe and effective.
In general, animals with active clinical illness should not be vaccinated. When using remote delivery systems (eg, darting syringe guns), one must be sure that a full dose has been delivered. Syringe darts may rebound quickly on impact and fail to deliver the dose required to elicit a satisfactory immune response.
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All members of the families Canidae, Procyonidae, Mustelidae, and some members of Viverridae are considered susceptible. The susceptibility of Hyaenidae and Ursidae is questionable, even controversial. Clinical distemper in exotic carnivores usually resembles that in dogs but often appears primarily as a neurologic disease that results in the affected animal losing its fear of humans; thus, the disease may be confused with rabies. Canine distemper infection has caused deaths in wild felids such as lions in Tanzania; however, vaccination of feline species in zoos is not deemed necessary.
Caution is advised in vaccinating wild-caught animals because they may be incubating the disease. While a killed virus vaccine would be preferred, none are currently available. Several MLV vaccines of chick embryo or avian tissue culture origin have been used in zoos for several years and appear to be satisfactory, based on limited studies. It is prudent to consult a zoo veterinarian for recommendations of specific products. There is marked variation among species and individuals in their reaction to MLV vaccines, and different MLV vaccines vary in their degree of attenuation. MLV vaccines marketed for use in mink generally are more highly attenuated and are recommended for use in Mustelidae. However, European mink have developed canine distemper even when such vaccines have been used. Ferret-origin MLV vaccines are contraindicated for use in any nondomestic carnivore.
Single doses of MLV vaccines are administered SC or IM to young animals after weaning, with monthly booster doses up to 4 mo of age and annual revaccination thereafter. For fennec foxes, meerkats, ferrets, red pandas, and giant pandas, canarypox vectored distemper vaccines appear to be safe and effective. It may be prudent to adjust the dose of these vaccines to account for differences in the size of these animals.
Canine Parvovirus and Feline Panleukopenia
Canine parvovirus, raccoon parvovirus, and feline panleukopenia virus are closely related antigenically and pathogenetically. Wild Canidae, Felidae, most Mustelidae, Procyonidae, and Viverridae are considered susceptible to one or more of these parvoviruses. MLV vaccines that are safe for one species may be insufficiently attenuated for others. Therefore, only inactivated vaccines of tissue or tissue-culture origin should be used in exotic species. Recommendations for dosage and frequency of vaccination have been determined somewhat empirically: for small species, 1 standard small animal dose (1 or 2 mL) is given SC or IM; for larger species, 2 mL/10 lb (4.5 kg) body wt to a maximum of 10 mL is given. A booster dose should be given at 10–14 days, and vaccination repeated at 6- to 12-mo intervals. Combination vaccines containing MLV canine distemper, canine adenovirus 2, canine parainfluenza, and feline panleukopenia or canine parvovirus have been used in wild Canidae without adverse effects, but experience of zoo veterinarians has been variable. Similarly, there are combination MLV feline vaccines that contain feline panleukopenia, feline rhinotracheitis, and feline caliciviruses. Most zoo veterinarians report good results with such vaccines in exotic felids, but a few report conflicting results. Combination killed feline panleukopenia, feline rhinotracheitis, and feline calicivirus vaccines are preferred.
Wild Equidae are susceptible to equine encephalomyelitis. Vaccination should follow guidelines recommended for domestic horses in endemic areas. Inactivated trivalent (Eastern, Western, Venezuelan) or bivalent (Eastern, Western) vaccines, or combinations of these with tetanus toxoid, are administered according to manufacturers' instructions, usually intradermally or IM depending on the product used. Initial immunization consists of 2 doses, 1–2 wk apart. Annual revaccination with intradermal products consists of 2 doses, 1–2 wk apart; combination IM products usually consist of a single injection. The susceptibility of wild Equidae to West Nile virus is unclear, but many zoos currently vaccinate zebras, tapirs, and related species with currently available inactivated equine products. A DNA vaccine may also be effective in these species. Some zoos also routinely use equine influenza vaccines.
Equine Herpesvirus 1 Infection
This can cause abortion in exotic Equidae. Only killed virus vaccines are recommended because it is not known whether MLV vaccines are adequately attenuated. A single vaccination should be given to foals at 3–4 mo of age and at 4-mo intervals up to 1 yr. Mares should be immunized every 4 mo to maintain adequate protection against abortion because even after recovery from natural infection, protective immunity lasts only ∼4 mo.
Erysipelothrix rhusiopathiae is pathogenic for wild Suidae and Tayassuidae (peccaries). Erysipelas bacterin (2 mL) is administered SC at 2–3 mo of age, with a repeat dose in 3–5 wk, and a single annual booster (see Erysipelas). Cetaceans, especially dolphins, are also susceptible to erysipelas (see Erysipelas).
Exotic felids are susceptible to feline caliciviruses. As with feline rhinotracheitis virus, vaccines against this disease are combined with other feline vaccines. Vaccination recommendations are the same as for feline rhinotracheitis.
Feline Herpesvirus Rhinotracheitis
Feline viral rhinotracheitis is a serious disease threat in exotic Felidae. Vaccines currently available are killed or MLV, usually in combination with other agents (eg, canine parvovirus and feline panleukopenia). These are given IM or SC in a single dose at weaning, followed by doses given at monthly intervals to 4 mo and annually thereafter.
Infectious Canine Hepatitis (Canine Adenovirus 1 [CAV-1])
All Canidae are susceptible. In foxes, the disease is called fox encephalitis due to a predominant neurotropism and neurologic signs. Ursidae may also be susceptible to CAV-1 infection. No killed virus vaccines are commercially available. MLV vaccines that contain combinations of canine distemper and CAV-1 or CAV-2 are used. The CAV-2 MLV is considered less likely to cause adverse postvaccinal reactions (eg, corneal opacity) than the CAV-1 MLV and is preferred for immunization against diseases caused by CAV-1 or CAV-2. These viruses are closely related antigenically and provide cross-protection. Single doses of such combination vaccines are administered SC or IM at weaning with monthly booster doses up to 4 mo of age and annual revaccination thereafter.
Leptospirosis is occasionally seen in exotic Canidae, Procyonidae, Ursidae, Mustelidae, Suidae, Tayassuidae, and in Cervidae and other ruminants of the families Bovidae, Camelidae, Giraffidae, etc. Bacterins that contain immunogens against Leptospira interrogans serovars canicola and icterohaemorrhagiae are used in the carnivores listed above. Ruminants, pigs, and peccaries are immunized with bacterins that contain serovars pomona, hardjo, icterohaemorrhagiae, canicola, and grippotyphosa. Carnivores are vaccinated with a 1 or 2 mL dose, IM or SC, at 6–8 wk of age, repeated in 14 days. Boosters are given every 6 mo. Hoofed animals are immunized with 5 mL of pentavalent bacterin IM; annual or, preferably, semiannual boosters are recommended. Vaccination does not necessarily prevent shedding of the causal organism(s).
Measles, Mumps, and Rubella
Pongidae are immunized against measles, mumps, and rubella at 2–3 mo of age with 0.5 mL of MLV human vaccine injected SC. This vaccination is also recommended for monkeys. Annual booster doses are given.
Wild sheep and goats are susceptible to pneumonia similar to shipping fever pneumonia of domestic sheep. Parainfluenza 3 (PI-3) is recognized as an important primary component, along with stress and Mannheimia haemolytica. Modified live virus PI-3 vaccines, particularly those administered intranasally, have been useful in reducing incidence of lamb pneumonia. Vaccine is administered at 3–4 mo of age, 1 mL in each nostril, and repeated 3–4 wk before anticipated shipment and annually thereafter.
Primates, particularly the Pongidae (great apes) are susceptible to poliomyelitis. Oral trivalent MLV poliomyelitis vaccine is preferred to parenteral inactivated vaccine due to ease of administration. A single human dose (0.5 mL) is given PO on a sugar cube after 6 mo of age and annually thereafter. Vaccinated animals should be isolated from unvaccinated primates (including humans) for 1 mo after inoculation.
All wild mammals are susceptible (see Rabies). In areas where the incidence of rabies in free-living wildlife is high, mammals in zoos or kept as pets may be at high risk of exposure. In such cases, vaccination is recommended. However, the efficacy of parenteral rabies vaccination of wild animals has not been established, and no vaccine is licensed for use in wild animals. When vaccination is considered necessary, only killed virus vaccine should be used. Several inactivated vaccines prepared of nervous tissue (eg, murine, ovine, or caprine) or tissue culture have been found satisfactory in terms of safety and immunogenicity, the latter based on limited tests that demonstrated adequate antibody responses in some exotic carnivores. The human diploid cell-line origin killed virus vaccines appear to have the best immunogenicity in domestic species. These vaccines should be administered by deep IM injection. Young animals are vaccinated at 3–4 mo of age, and vaccinations must be repeated annually. MLV rabies vaccines licensed for domestic animals should never be used in exotic animals because they are often insufficiently attenuated and may produce clinical rabies and death. Evaluation of vaccines intended to control rabies in wildlife continues in several countries.
Wild-caught animals, especially foxes, raccoons, and skunks, even when very young, may have been exposed to rabies and may be incubating the disease. Because the incubation period can be quite prolonged (up to 1 yr), a short observation period is inadequate. The National Association of State Public Health Veterinarians recommends that wild-caught animals that will have public contact in zoos should be quarantined for ≥180 days.
Because of the potential for rabies exposure, keeping wild animals as pets, especially wild-caught carnivores, should be discouraged and is illegal in many jurisdictions.
Primates, exotic Equidae, Proboscidae (elephants), Pongidae, Cervidae (deer), camelids, and wild sheep and goats should be immunized against tetanus. Exotic Equidae and elephants are vaccinated on the same schedule as domestic horses; primary immunization at 3–4 mo of age consists of 2 IM injections of tetanus toxoid, 1 mo apart. A single booster dose is given annually.
Pongidae are often vaccinated against tetanus using the diphtheria, tetanus toxoid, and phase 1 pertussis (DPT) vaccines intended for use in human children or monovalent human tetanus toxoid. Monovalent tetanus toxoid is preferred because pertussis and diptheria are not considered health risks for nonhuman primates. Primary immunization consists of 0.5 mL vaccine injected IM on 3 occasions at 3-mo intervals, with a booster dose 1 yr after the third injection. Thereafter, booster immunizations of 0.5 mL of diphtheria-tetanus toxoid or tetanus toxoid alone are given every 3–5 yr or after potential exposure due to injury.
Wild sheep and goats and cervids are sometimes immunized beginning at 10–12 wk of age with multivalent clostridial bacterin-toxoids containing immunogens for Clostridium tetani, C perfringens (types B, C, D), C septicum, C chauvoei, C novyi, C sordellii, and C haemolyticum in areas of high exposure risk. The initial dose is 5 mL followed in 6 wk by a 2-mL dose, administered SC. A 2-mL booster dose should be given annually.
A number of infectious diseases, including bovine viral diarrhea (BVD), bluetongue, malignant catarrhal fever, and epizootic hemorrhagic disease of deer, may appear as serious local problems but are not widespread in zoos. Unfortunately, satisfactory vaccines for many infectious diseases are not available for exotic animals. Inactivated BVD vaccines are recommended in situations in which BVD has been a problem. Annual vaccination with 1 standard bovine dose IM should begin at 3 mo of age.
Satisfactory vaccines for bluetongue, epizootic hemorrhagic disease, and malignant catarrhal fever are not currently available in the USA.
Last full review/revision July 2011 by Ian Tizard, BVMS, PhD, DACVM