THE MERCK VETERINARY MANUAL
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Overview of Vaccination of Exotic Mammals

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Exotic mammals are susceptible to many of the same infectious diseases that affect domestic mammals. However, vaccination of these species is often extra-label, because vaccines are tested and approved for use only in domestic species. Vaccination protocols recommended for exotic mammals are therefore based on limited published information, anecdotal experience, and relative risk of disease to the species from the infectious agent or vaccination itself. Reports of lack of seroconversion, antibody production, sustained protection, and induction of the disease resulting in morbidity and mortality in a variety of species, particularly for rabies and distemper, are common after vaccination of exotic mammals. Regardless, vaccination should be considered in captive wildlife and conservation programs based on a number of factors. Many diseases preventable by vaccination such as canine distemper virus, canine parvovirus, feline calicivirus, feline panleukopenia virus, and rabies virus have caused population declines or reduced host fitness in critically endangered mammals. Certainly, infectious disease outbreaks in small numbers of highly genetically valuable individuals can disastrously affect conservation projects. Unfortunately, the biology of many of these preventable diseases (incubation period, transmissibility, etc) in exotic mammals is often unknown. Captivity may enhance the risk of acquiring disease based on food sources, exposure to rodents and other disease hosts, and an unknown degree of exposure of other zoo animals, which is unlikely to occur in nature. Thus, due consideration of protection of captive nondomestic species, even those destined for release to the wild, is warranted. Core vaccines are designated as those that protect captive animals from life-threatening, globally distributed diseases. The determination of protection has largely been based on studies in domestic species; nonetheless, based on current knowledge, these vaccines deserve full consideration for inclusion into vaccination regimens for captive exotic mammals.

Individual animal safety dictates that inactivated or recombinant viral or bacterial vaccines are preferable to modified-live virus (MLV) vaccines, which have the potential to cause disease in exotic mammals and abortions in hoofstock. However, in select species, especially Old World apes, MLV vaccines have received sufficient use to warrant consideration based on the serious risk of morbidity and mortality. Use of MLV vaccines for rabies and distemper are generally contraindicated in exotic mammals. In particular, use of MLV distemper vaccines in exotic mammals may result in postvaccinal myelitis or distemper. Recently developed canary pox–vectored vaccines are the current vaccine of choice for distemper and appear both safe and efficacious. The following concepts should be considered before extra-label use of a vaccine in an exotic animal. Possession of the animal should be legal per state community and other applicable laws. Informed consent of the owner and discussion of the availability or lack of safety and efficacy trials associated with the use of this vaccine in the animal should be documented in the medical record. Use of product and vaccination procedures with record of previous success such as those used or recommended in zoo (Association of Zoos and Aquariums or American Association of Zoo Veterinarians) protocols, and those with publications supporting their safety and efficacy in the species, should be considered. Vaccination may be foregone in the face of lack of data to support that a certain disease occurs, despite antibody presence, in some species.

Vaccination protocols developed for exotic mammals should be determined with respect to number of animals, husbandry, relative value of animal and offspring, pregnancy, species susceptibility to a disease, likelihood of encountering disease, disease prevalence in the surrounding locality, ability to obtain useful products, information of reported or anecdotal benefits or disadvantages with usage of a vaccine in that species, housing and vector control programs, and zoonotic and infectious potential of the disease. As in domestic species, animals that are febrile or have other clinical signs of illness should not be vaccinated. Because a full vaccine dose is required to elicit a satisfactory immune response, remote vaccine administration should be weighed against anesthetic and disease risk. Some nondomestic mammals and their recommended vaccination protocols (eg, cervids, rodents, lagomorphs, camelids) are reviewed elsewhere in the Manual, and the reader should refer to the relevant chapters. In domestic mammals, young animals have differing vaccine schedules than those presented in Table 1: Vaccinations Recommended for Exotic MammalsTables based on waning maternal antibodies. Consideration of the provided references and consultation with experts in zoo medicine and exotic mammal husbandry are recommended to develop vaccination protocols. Specific vaccine protocols should be developed for neonates. For apes, a youngster vaccination schedule, based on the human schedule, should include the killed polio series and Haemophilus vaccination (http://www.cdc.gov/vaccines/schedules/index.html).

Although titer determinations may be useful for evaluation of vaccination in exotic mammals, the lack of antibodies does not equate to lack of immune response. This method quantifies only the humoral immune response, not the cell-mediated aspect, and protective titer levels for exotic mammals have not been evaluated or established. Examples of titers that may be assessed include rabies, distemper, parvovirus, and leptospires, as well as the encephalitic viruses and many viruses affecting nonhuman primates that also affect people. Yearly and preshipment viral titers, which vary based on species, are recommended for all primates. Titers change based on natural disease exposure, independent of vaccination, may or may not confer protection from disease, and may also wane quickly, despite repeated exposure.

Table 1

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Inactivated and attenuated-live vaccines for infectious bovine rhinotracheitis and infectious pustular vulvovaginitis are available. Vaccines may not prevent infection but reduce clinical signs and significantly reduce shedding of field virus. Use of the inactivated vaccine in exotic hoofstock may be preferred, because abortions and initiation of disease in vaccinated hoofstock have not been adequately studied.

Most, if not all of the Carnivora, including canids, procyonids, mustelids, and the viverids, are considered susceptible to canine distemper virus (CDV); the susceptibility of most Ursidae and Hyenidae is unknown. Giant and red pandas are an important exception among the ursids and appear quite susceptible; canine distemper vaccination has been specifically evaluated in and is recommended for use in this species. Large felids, particularly tigers and lions, also appear susceptible to disease, which in exotic mammals manifests primarily in the neurologic form. CDV is considered a core vaccination in captive canids and should also be considered in captive exotic felids with a history of disease in the collection. Many species of small carnivores have developed vaccine-induced distemper after receiving an MLV vaccine. The recombinant canary pox–vectored subunit distemper vaccine, which causes appropriate serologic titers and appears safe and effective, is now recommended for use in susceptible exotic mammals. Generally recommended vaccination regimens for young animals incorporate an initial vaccination after weaning with a 1-mo booster followed by yearly revaccination. Vaccination of free-living animals should be carefully considered, because vaccine efficacy is unknown for many nontarget species, and animals may have recovered from or be incubating disease, rendering vaccination a poor use of resources.

Canine parvovirus, raccoon parvovirus, and feline panleukopenia virus are closely related antigenically and pathogenetically. Canidae, Felidae, most Mustelidae, Procyonidae, and Viverridae are considered susceptible to one or more of these parvoviruses. Binturongs are susceptible to feline panleukopenia, and vaccination is recommended. Vaccinations that protect from feline panleukopenia are considered core vaccines in exotic felids, while those that protect from canine parvovirus are core vaccine for canids. Based on insufficient attenuation of MLV vaccines for some species, only inactivated vaccines of tissue or tissue-culture origin are recommended for use in exotic mammals. Vaccine and dosage regimen have been empirically determined but should adhere to label directions, with boosters recommended at 2 wk, 6 mo, and then annually. Based on reports of vaccine reaction associated with MLV combinations of canine distemper, canine adenovirus 2, canine parainfluenza, and canine parvovirus, multivalent vaccination with killed feline panleukopenia, feline rhinotracheitis, and feline calicivirus is preferred for use in exotic mammals.

Because nondomestic equids are susceptible to equine encephalomyelitis, vaccination should follow guidelines for domestic equids in endemic areas. Inactivated trivalent (Eastern, Western, Venezuelan) or bivalent (Eastern, Western) vaccine, or a combination of these with tetanus toxoid, are administered according to manufacturer instructions. Initial immunization is two doses, 1–2 wk apart with annual revaccination. Although susceptibility of tapir species is unknown, a similar vaccination regimen has been recommended in this species. The susceptibility of exotic equids to West Nile virus is unclear, but zebra, tapir, and related species are often vaccinated for West Nile virus; efficacy and safety of the inactivated equine (more commonly used) or the DNA West Nile virus vaccination in these species is unknown.

Equine herpesvirus 1 (EHV-1) can cause abortion in exotic equids; killed virus vaccination is recommended, because adequacy of attenuation in MLV vaccines is unknown for nontarget species. Vaccination of foals should begin at 4 mo, with boosters at 4-mo intervals up to 1 yr. Mares must be vaccinated often to provide protection from abortion, because EHV-1 natural protective immunity after infection lasts only 4 mo.

The bacterium Erysipelothrix rhusiopathiae is pathogenic for the Tayassuidae, nondomestic Suidae, cetaceans, and pinnepeds. Erysipelas bacterin can be administered with the standard regimen to nondomestic swine and peccaries (see Erysipelas). Despite the importance of preventing erysipelas in marine mammals, there is no bacterin designed specifically for these animals. Vaccination of cetaceans and pinnepeds is controversial, but a subunit vaccine has been investigated in dolphins (Bacterial Diseases of Marine Mammals). In facilities where captive cetaceans are vaccinated, extra-label bacterins are used to prevent erysipelas outbreak. Based on vaccine breaks, the necessity of bacterin culture and sensitivity testing before revaccination, and the risks of fatal anaphylaxis, sterile abscessation, tissue reaction, and animal immobilization, some facilities have reduced vaccination to one-time administration, even though antibody titers fall below the presumed effective level (also see Bacterial Diseases of Marine Mammals). Booster at 6 mo and annual revaccination are recommended to maintain protective antibody titers. Because disease appears less common and vaccination is not without significant risk of morbidity and mortality while protective efficacy remains unknown, vaccination is not routinely recommended in pinnepeds.

Exotic felids are susceptible to feline caliciviruses, and some strains may cause serious morbidity and mortality. This is considered a core vaccine in exotic felids. Vaccines are often combined into a multivalent formulation, and vaccine regimens are as for feline rhinotracheitis.

Feline viral rhinotracheitis is a serious disease threat in exotic Felidae and is considered a core vaccine. Available vaccines, inactivated, subunit, and MLV, are combined with feline calicivirus and are usually in multivalent formulations with other pathogens (eg, feline panleukopenia). A single dose should be administered at weaning, with monthly boosters until 4 mo of age and annually thereafter. In domestic cats, vaccination provides reasonable disease protection but does prevent infection or viral latency. Vaccinated cats can be infected; however, clinical signs and viral shedding are reduced.

All Canidae and binturong, a viverid, are susceptible; Ursids may also be susceptible. In foxes, the disease is called fox encephalitis due to a predominant neurotropism and neurologic signs. Canine adenovirus (CAV) is a core vaccination for captive canids. Because a killed vaccine is not commercially available, multivalent MLV vaccines containing canine distemper and CAV-1 or CAV-2 are often administered. Based on the close antigenic relationship of CAV-1 and CAV-2, vaccination with either virus provides cross-protection. CAV-2 is thought less likely to cause postvaccinal reactions, such as corneal opacity and hemorrhagic and necrotizing hepatitis (vaccine-induced adenoviral hepatitis). However, administration of CAV-2 MLV vaccine to a maned wolf (Chrysocyon brachyurus) has resulted in vaccine-induced adenoviral hepatitis. Therefore, vaccination recommendations for this species are limited to canine distemper virus, canine parvovirus, and rabies; vaccination with MLV CAV-2 is contraindicated in this species. For other canids, recommended vaccine regimens are a single dose of the multivalent vaccine at weaning, with monthly boosters until 4 mo of age followed by annual revaccination.

Canine influenza virus vaccination for domestic carnivores is considered noncore. However, if a collection has a history of canine influenza or is located in an endemic area, vaccination may be considered. Vaccination may also be considered for great apes, as well as for contact staff on a yearly basis before flu season. Equine influenza vaccine is administered to nondomestic equids in some zoos.

Leptospirosis occurs sporadically in exotic Canidae, Procyonidae, Viveridae, Ursidae, Mustelidae, Suidae, primates, Tayassuidae, and in Cervidae and other ruminants of the families Bovidae, Artiodactyla, Perisodactyla, Proboscidae, Camelidae, Giraffidae, etc. Vaccination of domestic carnivores with Leptospira bacterins is considered noncore. However, if a collection has a history of or is in an endemic area for leptospirosis, vaccination should be considered with bacterins that contain immunogens against Leptospira interrogans serovars Canicola and Icterohaemorrhagiae. 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).

Ruminants, pigs, and peccaries are immunized with pentavalent bacterins that contain the serovars Pomona, Hardjo, Icterohaemorrhagiae, Canicola, and Grippotyphosa. Hoofstock should have an initial vaccination with a booster 4–8 wk later (as per label instructions); booster vaccination is essential, because leptospirosis vaccines are killed vaccines. At a minimum, hoofstock should be revaccinated yearly approximately 6–8 wk before the breeding season. However, because protective titers can wane within a year, a semiannual vaccination schedule may be instituted if leptospirosis is an issue or occurs in valuable breeding stock. Vaccination does not necessarily prevent shedding of the causal organism(s).

Pongidae are often immunized against measles, mumps, and rubella at 2–3 mo of age and annually thereafter with 0.5 mL of MLV human vaccine injected SC. This vaccination is also recommended for monkeys. New World monkeys are more resistant than Old World monkeys, but mortality is high when infected. Vaccine administration in other primates is optional, depending on colony-specific concerns. Vaccination of susceptible populations of nonhuman primates (>6 mo old) should be considered when contact with people cannot be adequately controlled (eg, nonhuman primates as pets). Annual booster doses are given.

Exotic sheep and goats are susceptible to pneumonia caused by parainfluenza 3 (PI-3) and Mannheimia haemolytica. Modified live virus PI-3 vaccines, particularly those administered intranasally are useful to reduce the incidence of lamb pneumonia. Vaccine is administered at 3–4 mo of age, 1 mL per 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 because of 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 people) for 1 mo after inoculation.

All exotic mammals are susceptible to rabies (see Rabies). Vaccination is considered core for felids and canids in endemic areas and recommended for mammals in zoos in areas where incidence of rabies in free-living wildlife is high. However, the efficacy of parenteral rabies vaccination of exotic mammals has not been established, and no commercially available vaccine is licensed for use in free-living animals. Use of rabies vaccines in these species is extra-label and is not considered protective in the event of a bite. Based on the potential for human rabies exposure, keeping wild-caught carnivores as pets should be discouraged and is illegal in many jurisdictions. Wild-caught animals such as foxes, raccoons, and skunks may have been exposed to the virus when quite young and may incubate disease for a prolonged period (>1 yr), rendering a short observation period inadequate. The National Association of State Public Health Veterinarians recommends that wild-caught animals with public contact (eg, in zoos) should be quarantined for at least 180 days.

When vaccination is considered necessary, only killed-virus vaccine should be used, and it should be administered via deep IM injection. MLV rabies vaccine licensed for use in domestic species should never be used in exotic animals, because such vaccines are often insufficiently attenuated and may produce clinical rabies and death. 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. Young animals are vaccinated at 3–4 mo of age, and vaccinations must be repeated annually. Vaccination for rabies of bats in captivity is done at some institutions; MLV vaccination of bats incubating the rabies virus may hasten the disease course and result in death (as occurs in people). Use of oral bait vaccination for control of rabies in wildlife continues in several countries; this vaccination is not intended for use in captive, single animals.

Primates, exotic Equidae, Proboscidae (elephants), Pongidae, Cervidae (deer), camelids, and exotic sheep and goats should be immunized against tetanus. Although the susceptibility of tapirs to tetanus has not been documented, vaccination is recommended. Exotic Equidae and elephants are vaccinated on the same schedule as domestic horses; primary immunization at 3–4 mo of age consists of two 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. However, susceptibility of these diseases likely varies in primates, because olive baboons were recently found to develop clinical signs of pertussis and a strong anamnestic response. Primary immunization consists of 0.5 mL of vaccine injected IM on three 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.

In exotic hoofstock, the need for clostridial vaccines depends on animal husbandry and density, environment, and local disease circumstances. If vaccination is warranted, vaccines should be given according to manufacturers' recommendations for hoofstock. Multivalent clostridial vaccines are available for prophylaxis; tetanus antitoxin can be used if tetanus is a concern. Pregnant animals should be vaccinated 4–8 wk before parturition to increase specific colostral immunoglobulins. Neonates can be vaccinated at 4 and 8 wk of age with Clostridium perfringens type C and D. Exotic sheep, goats, and cervids are sometimes vaccinated 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, epizootic hemorrhagic disease of deer, anthrax, encephalomyocarditis virus, cowpox, and brucellosis, 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 one standard bovine dose IM should begin at 3 mo of age. Satisfactory vaccines for bluetongue, epizootic hemorrhagic disease, malignant catarrhal fever, and encephalomyocarditis virus are not currently available in the USA. In contrast, a number of vaccines are available for extra-label use in exotic mammals, which may not be efficacious or necessary. These noncore vaccines for domestic carnivores include feline leukemia virus, feline immunodeficiency virus, Chlamydophila felis, feline infectious peritonitis, feline Gardia vaccine, coronavirus, and Lyme disease. Should a collection have a history of these diseases or be in an area endemic for disease, vaccination may be considered. Anthrax vaccine has been administered to cheetah (Acinonyx jubatus) and black rhinoceros (Diceros bicornis) without apparent ill effect, and conference of protective immunity in some with a single booster was recommended. Vaccination of valuable animals could be considered in the event of an outbreak. Brucellosis affects both free-living and captive marine mammals, with minimal apparent zoonotic potential. No vaccination or other control methods for brucellosis are established for these or other exotic mammal species in captivity. Vaccination programs for free-living bison and cervids are controversial. Although the MLV vaccine effectively prevents future abortions and the transmission of brucellosis, it does not protect from infection or seroconversion, may induce abortions in pregnant animals, and is infectious to people. The reemergence of brucellosis worldwide and an increasing incidence of human disease underscore the need for new and improved brucellosis vaccines. The vaccinia, cowpox, and small pox (variola) viruses are closely related pox viruses that may have all evolved from a single ancestral virus. Cowpox virus has caused morbidity and mortality in canids, felids, equids, elephant, rhino, camelids, viverids, rodents, primates, and hoofstock; zoonotic disease has been reported. Vaccinia titers have been documented in free-living nonhuman primates in South America. The CDC currently limits distribution of vaccinia vaccine to health care and bioindustrial laboratory workers with exposure risk.

Last full review/revision August 2014 by J. Jill Heatley, DVM, MS, DACZM, DABVP (Avian); Jeffrey Musser, DVM, PhD

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