Vaccination of Exotic Mammals

All mammals should be presumed susceptible to rabies.

Vaccination against rabies is considered a core vaccination for all carnivores and is recommended for many other mammal species in areas where incidence of rabies in free-living wildlife is high.

Although the efficacy of parenteral rabies vaccination of exotic mammals has not been established in most species, titers appear to indicate appropriate humoral immune response, with protective levels presumed across taxa.

Commercially available parenteral vaccines are licensed in domestic cats, dogs, sheep, cattle, horses, and ferrets; otherwise, use is extralabel. For parenteral vaccines, killed virus vaccine products only are recommended in exotic mammals, with the exception of a recombinant nonadjuvanted modified live canarypox vaccine approved for ferrets.

Young animals are vaccinated as early as 12 weeks, with a booster 1 year after and then repeated, based on product recommendation or titers.

In several countries, oral rabies vaccines (modified live virus vaccines), delivered via bait distributed in a target area, are used for control of rabies in wildlife. This type of vaccination is not intended for use in individual captive animals.

Rabies vaccine volumes for exotic mammals in managed care generally are the same as labeled for domestic mammal species; however, in especially large exotic mammals (eg, elephants), the volume is often doubled or even quadrupled based on antibody response or titers. Volumes < 1 mL have been routinely used in especially small exotic mammals (eg, Megachiroptera, or fruit bats); appropriate antibody response has been documented with vaccine volumes of 0.1–0.25 mL.

In case of a bite, consultation with appropriate public health officials is required. The National Association of State Public Health Veterinarians' Compendium of Animal Rabies Prevention and Control, 2016, recommends against keeping wild-caught animals as pets, and doing so is illegal in many jurisdictions. In consideration of the potential long incubation period of rabies, the Compendium also recommends that any wild-caught animals with public contact (eg, in zoos) be quarantined for at least 180 days.

Canine distemper virus (CDV) affects species across multiple taxa, with a large number of susceptible carnivores. Given the widespread distribution and severity of CDV, vaccination against CDV is considered a core vaccine in multiple families of the order Carnivora.

Species known to be particularly susceptible to CDV include the following:

• giant panda (Ailuropoda melanoleuca) of Ursidae

• red panda (Ailurus fulgens) of Procyonidae

• black-footed ferret (Mustela nigripes) of Mustelidae

• African wild dog (Lycaon pictus), bush dog (Speothos venaticus), gray fox (Urocyon cinereoargenteus), and maned wolf (Chrysocyon brachyurus) of Canidae

All of these species have a risk of death from vaccine-induced disease after administration of modified live virus (MLV) vaccines. Due to the concern for vaccine-induced disease in exotic mammals, recombinant nonadjuvanted modified live canarypox vaccines—first developed and licensed for domestic ferrets—have become the most widely used vaccines.

Limited availability of this canarypox product has led to investigation into the use of MLV vaccine products in certain situations. Due to their susceptibility to CDV, big cats of the genus Panthera in family Felidae, both in captivity and in the wild (where the disease manifests primarily in the neurological form), have been a large target of such investigation.

CDV vaccination protocol for captive exotic mammals generally follows the recommendation for domestic species, with the first series performed using a recombinant or killed virus vaccine product, followed by a booster with an MLV vaccine. Clinicians must assess the risks of inadequate protection versus vaccine-induced disease when developing species-specific protocols.

Domestic ferrets are most susceptible to CDV as juveniles, when maternal antibodies wane, and vaccination is recommended to prevent disease with 2 effective doses starting at 8 weeks.

Although a licensed recombinant nonadjuvanted modified live canarypox vector vaccine exists for domestic ferrets, its availability is limited, so live, attenuated virus vaccines labeled for use in dogs have been used. Because of an outbreak of vaccine-induced CDV in a major breeding colony in the US, ferrets are required to be vaccinated at 6–8 weeks old, prior to entering the domestic pet trade, with a recommended booster every 3–4 weeks until 14 weeks, followed by annual boosters.

The parvoviruses, including canine parvovirus, raccoon parvovirus, and feline panleukopenia virus, are closely related antigenically and pathogenetically.

Vaccination against canine parvovirus is considered a core vaccine for Canidae and a recommended vaccine for Procyonidae.

Feline panleukopenia virus vaccine is a core vaccine for Felidae and a recommended vaccine for Hyaenidae, Viverridae, Mustelidae, and Procyonidae.

Giant pandas of Ursidae are recommended to receive both canine parvovirus and feline panleukopenia virus vaccinations.

For both canine parvovirus and feline panleukopenia virus, killed virus vaccines are recommended, with the noteworthy exception being certain canid species, including red wolves (Canis rufus) and gray wolves (C lupus), for their entire vaccine series, and adult maned wolves (Chrysocyon brachyurus), for which MLV vaccines are recommended once protective titers (> 80) have been observed.

Canine parvovirus and feline panleukopenia virus vaccination protocols for exotic mammals are modeled after those for domestic dogs and cats, respectively, with care required when using multivalent products of which other MLV vaccine products might be components.

Tetanus, caused by Clostridium tetani, is a risk to exotic mammals in multiple taxa. It is, therefore, a core vaccine for New and Old World monkeys, great apes, Equidae, Tapiridae, and elephants, with recommended use in prosimians, macropods, artiodactylids (including Cervidae, Giraffidae, Camelidae, Bovidae, Suidae, and Tayassuidae), and Rhinocerotidae.

In artiodactylids and rhinoceroses, this vaccine is often administered in combination with other inactivated clostridial toxins, most often C perfringens type C (beta) and D (epsilon), to induce additional immunity to clostridial disease. The initial multivalent clostridial vaccine is administered when the animal is 4–8 weeks old, followed by a booster after 3–4 weeks and annual boosters after that.

Exotic equids follow the protocols established for domesticated horses, beginning vaccination at 4–8 months with one booster 4–6 weeks after initial vaccination and then an annual booster after that. This protocol is often used in other perissodactylids (Tapiridae and Rhinocerotidae) and in elephants.

Because of their small body size, prosimians are given tetanus toxoid at a smaller volume than the recommended equine dose.

In other primates, tetanus coverage is provided with a multivalent vaccine against bacterial respiratory pathogens, including Corynebacterium diphtheriae and Bordetella pertussis, as part of the diphtheria, pertussis, tetanus (DPT) or tetanus, diphtheria, acellular pertussis (TDaP) vaccination protocol.

Late vaccination (catch-up) human protocols are often followed for nonhuman primates, with a first dose around 6–9 months, pending behavioral training, and a total of 4–5 doses. The last dose is administered after age 4 and at least 6 months after dose 3. Routine boosters every 5 years are recommended.

Also see information on clostridial vaccines.

Vaccination against measles, mumps, and rubella (MMR) is a core vaccine for great apes and recommended for Old World monkeys.

Given the nature of the MLV vaccine, veterinarians must be alert for possible vaccine-induced disease in New World primates.

Current protocols follow CDC pediatric recommendations for the catch-up vaccine series.

Some MMR vaccines also include varicella vaccine (MMRV), which confers protection against the varicella virus, the causative agent of chickenpox. Given the infectious nature of this pathogen in primates, immunization may be beneficial.

Seasonal influenza vaccine has been administered routinely to many great ape species if individuals are over 6 months old. The vaccine is administered between October and December in the Northern Hemisphere to coincide with influenza season and to decrease both likelihood and severity of infection. Human influenza vaccines are used; sourcing may be a challenge for a zoo clinician.

Feline viral rhinotracheitis (caused by feline herpesvirus 1) is a serious disease threat in exotic Felidae, and vaccination against feline viral rhinotracheitis is considered a core vaccine. Vaccination can decrease severity of clinical signs and viral shedding but might not prevent infection or viral latency.

Multiple vaccine types are available, generally combined with feline calicivirus and other core vaccines.

Killed virus vaccines are considered safest, although to provide stronger protection, some institutions use MLV vaccines or boosters with MLV vaccines after an initial killed virus vaccine series. Reversion to virulence after MLV vaccination has been noted in black-footed cats (Felis nigripes).

Feline viral rhinotracheitis vaccinations in exotic felids follow protocols for domestic cats. Titers can be used to guide boosters in adults; however, serological testing can be unreliable.

Vaccination against feline calicivirus is also a core vaccine for exotic felids. Exotic felids are susceptible to the virus, and some strains can substantially increase morbidity and mortality rates.

Vaccines against calicivirus are often combined with other vaccines into a multivalent formulation, and vaccine regimens for exotic felids are as for domesticated cats receiving vaccines against feline rhinotracheitis virus. Reversion to virulence after MLV vaccination has been noted in black-footed cats.

The encephalitides of Eastern equine encephalitis, Western equine encephalitis, and West Nile virus are constituents of combination vaccines deployed as core vaccines based on vector presence and geographic risk.

Various mammal groups have been vaccinated against West Nile virus and other encephalitides; however, the practice must be weighed based on the challenge of vaccination and risk for adverse effects (eg, sterile vaccine abscesses).

Killed virus vaccines are often used in combination with each other and with tetanus toxoid. Some combination products contain killed equine influenza virus.

Vaccine protocol for exotic equids follows that recommended for domestic equids, with a 3-dose series starting between 4 and 6 months, generally determined by the start of vector season, with a second dose administered 4 to 6 weeks later and a third dose at 10–12 months. Annual boosters are recommended.

Vaccination against infectious canine hepatitis has generally been by using vaccines against canine adenovirus 2 to provide cross-protection against the causative agent of infectious canine hepatitis, canine adenovirus 1.

Commercially available products are MLV vaccines with MLV components, including CDV, that must be used with caution in exotic mammals. This vaccine is currently recommended according to risk-based assessment for Canidae and Ursidae.

Vaccine protocols for exotic canids follow those recommended for domestic canids.

After the 2020 global pandemic, veterinary vaccination against SARS-CoV2 relied on one licensed mink vaccine, with deployment to multiple carnivores, primates, and other mammals. Because the licensed veterinary product is no longer commercially available, vaccination of exotic mammals against SARS-CoV2 is more challenging, relying on sourcing human products for Panthera spp and great apes or accessing a limited supply of expired vaccine product.

Protocols for use of the veterinary product were similar to those for the vaccine in humans, with a 2-dose initial series at least 4 weeks apart.

Humoral immune response via titers has shown mixed results to the veterinary vaccine.

Leptospirosis can occur in multiple exotic mammals, including carnivores, artiodactylids, primates, and Rhinocerotidae. The black rhinoceros is considered a high-risk exotic species, and vaccination is currently recommended by taxon advisory groups in endemic areas. Vaccination of domestic carnivores with Leptospira bacterins is considered noncore, so exotic mammal vaccination is often guided by risk in endemic areas and concern for disease in the target species.

Leptospirosis vaccination protocols for exotic mammals follow those recommended for the most closely related domesticated species.

Vaccination against leptospirosis does not necessarily prevent shedding of the organism.

Artiodactylid neonates can be vaccinated against viral diarrhea with a 2-dose protocol administered IM to the dam during the final trimester of pregnancy or by dosing the calf PO immediately after birth, ideally before any nursing. The latter protocol is most often used in hand-reared animals, and the decision to vaccinate pregnant dams is based on a comparison of risk for the disease in neonates versus risk of vaccine administration.

Vaccine-induced disease has been noted anecdotally in very small neonates (Cephalophinae, or small to medium-sized antelopes) after oral vaccination by this author.

Many pathogens common in domestic production ruminants are not as prevalent in zoos; however, veterinarians should consider deploying noncore vaccines to exotic ruminants in zoos based on geographical risk and biosecurity of their institution.

Most exotic mammals have a closely related domestic mammal model from which noncore vaccination protocols can be extrapolated, such as for viral respiratory pathogens of artiodactylids (eg, parainfluenza-3 or infectious bovine rhinotracheitis) or noncore vaccines for domestic carnivores (eg, feline coronavirus, Chlamydia felis, and feline retroviruses).

For exotic mammal species lacking a comparable closely related domestic mammal model, the protocol developed for a specific vaccine often guides protocol development. For example, for Bordetella bronchiseptica, both MLV and killed virus vaccines have been used in Suidae and Canidae to prevent disease. Exotic mammals, including koalas of Vombatidae and sloths of order Pilosa, are also susceptible to this pathogen; thus, vaccination with a killed virus vaccine may be considered.

Exotic pets, such as miniature pigs, often closely follow their production animal counterparts' vaccine schedules. This is true for erysipelas and Actinobacillus pleuropneumoniae vaccine recommendations, as well as for rabies and leptospirosis vaccination. Vaccination begins at 8–12 weeks, with 1 booster administered 3–4 weeks after the initial dose, followed by annual boosters after that.

Historically, pet rabbits have not been vaccinated in the US; however, in response to an outbreak of potentially fatal calicivirus, the USDA granted emergency use of the rabbit hemorrhagic disease virus (RHDV2) vaccine against calicivirus. Vaccinations can begin as early as 3–4 weeks, with a booster at least 3 weeks later and annual boosters thereafter.

• Compendium of Animal Rabies Prevention and Control, 2016. National Association of State Public Health Veterinarians.

• Transmissible Disease Handbook. European Association of Zoo and Wildlife Veterinarians.

• Infectious Disease Manual. American Association of Zoo Veterinarians.

• Association of Zoos and Aquariums Taxon Advisory Group and Species Survival Plan Supplemental Veterinary Care Resources.

• Animal Care Manuals. Association of Zoos and Aquariums.