Vaccination of Exotic Mammals
Exotic mammals are susceptible to many of the same infectious diseases that affect domestic mammals. Vaccines developed for domestic species are often used extralabel in exotic species, with protocols and vaccine selection based on limited publications, institutional experience, and organizational recommendations. For managed captive populations, recommendations often include core vaccines designed to protect against life-threatening, widely distributed diseases, as well as zoonotic diseases such as rabies. Beyond those, vaccine choices are often determined by geography or institutional risk factors. Protocols and product recommendations may change rapidly based on anecdotal reports, and it behooves any veterinarian establishing a vaccine protocol to consider relative risk of both the infectious agent and target species, including delivery of the vaccine and possible adverse effects.
In the absence of true efficacy studies, repeated demonstrations of vaccine safety in exotic mammal species and the few natural challenge reports guide vaccine protocol development in captive and wild exotic mammals. Vaccine failures range from failure to protect against natural challenges to induction of disease resulting in morbidity and mortality due to a vaccine.
Seroconversion, a measure of humoral immune response to vaccination, has been used most routinely to investigate vaccination protocol success; however, many vaccines may target cell-mediated immunity (CMI) rather than humoral immune response. Although antibody production may be an inadequate way to identify an adequate vaccine response, it remains one of the most widely published markers of vaccination success in exotic mammals. Additionally, protective titer levels for exotic mammals have not been evaluated or established for most vaccines used in these species. 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.
Another logistical concern when developing and deploying a vaccination protocol in exotic mammals is differentiating infected from vaccinated animals (DIVA). This is of particular import when vaccinating against a reportable disease or one for which documenting exposure may be important to longterm management of a population. Some vaccines are deployed under certain circumstances, such as in the face of an epidemic (eg, bluetongue vaccination in the face of an outbreak in Europe).
Vaccination protocols developed for exotic mammals should be determined with respect to number of animals, susceptibility to a disease, likelihood of encountering said disease, delivery route and associated risk, disease prevalence in surrounding geography, ability to obtain vaccine products, and measures of vaccination success. Another important consideration is the zoonotic potential of diseases in captive exotic mammals or the risk of transmission to or from adjacent domestic populations in wild mammals.
Vaccination protocols for juvenile exotic mammals are largely based on the need to provide immune coverage as maternal immunity wanes. Some exotic mammals and their recommended vaccination protocols (eg, ferrets, potbellied pigs, llamas and alpacas) are discussed in the topics devoted to those species. As in domestic species, animals that are febrile or have other clinical signs of illness should not be vaccinated.
In summary, vaccination should be considered in captive wildlife and conservation programs based on a number of factors:
Vaccination Recommendations for Exotic Mammals
All exotic mammals should be presumed susceptible to rabies. Vaccination is considered core for all carnivores and recommended for many other mammal species in zoos 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, titers do appear to indicate appropriate humoral immune response, and protective levels have been presumed across taxa.
Commercially available parenteral vaccines are licensed in domestic cats, dogs, sheep, cattle, horses, and ferrets; otherwise, use is extralabel. Killed vaccine products only are recommended in exotic mammals. Young animals are vaccinated as early as 12 weeks of age, with a booster one year after, and then repeated based on product recommendation or titers. Use of oral bait vaccination for control of rabies in wildlife continues in several countries; this type of vaccination is not intended for use in captive, single animals.
In the case of a bite, consultation with appropriate public health officials is required. Wild-caught mammals may have been exposed at a young age, with a prolonged incubation period. The National Association of State Public Health Veterinarians 2016 Compendium of Animal Rabies Prevention and Control recommends that wild-caught animals with public contact (eg, in zoos) be quarantined for at least 180 days. Based on the potential for human rabies exposure, keeping wild-caught carnivores as pets should be discouraged, and is illegal in many jurisdictions.
Canine distemper virus (CDV) affects species across multiple taxa, with a large number of susceptible carnivores. Given its widespread nature and severity of disease, it is considered a core vaccine in multiple families of the order Carnivora. Species known to be particularly susceptible to CDV include the giant panda (Ailuropoda melanoleuca) of Ursidae; red panda (Ailurus fulgens) of Procyonidae; black-footed ferret (Musteles nigripes) of Mustelidae; and African wild dog (Lycaon pictus), bush dog (Speothos venaticus), gray fox (Chrysocyon cinereoargenteus), and maned wolf (Chrysocyon brachyurus) of Canidae. All of these species have a risk of death from vaccine-induced disease following use of MLV vaccines. Recombinant canarypox vaccines, first developed and licensed for domestic ferrets, have become the most widely used vaccines due to this concern for vaccine-induced disease in exotic mammals, although availability of the product has led to investigations into use of MLV products in certain situations.
Big cats of the genus Panthera in family Felidae have been a large target of this investigation due to their susceptibility in captivity and in wild populations, where the disease manifests primarily in the neurologic form. Vaccination protocol for exotic mammals generally follows the recommendation for domestic species, with the first series performed using a recombinant or killed product followed by booster with an MLV vaccine. Clinicians must assess the risk of inadequate protection vs vaccine-induced disease when developing species-specific protocols.
The parvoviruses, including canine parvovirus, raccoon parvovirus, and feline panleukopenia virus, are closely related antigenically and pathogenetically. Canine parvovirus vaccine is considered a core vaccine in Canidae, with recommendations to vaccinate Procyonidae. Feline panleukopenia virus vaccine is a core vaccine for Felidae with a recommended vaccination of Hyaenidae, Viverridae, Mustelidae, and Procyonidae. Giant pandas of Ursidae are recommended to receive both the canine parvovirus and feline panleukopenia virus vaccinations. Killed vaccines are recommended for both of these diseases, with the significant exception being certain canid species, including red wolves (Canis rufus), grey 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. Vaccination protocols are modeled after domestic species, with care required when using multivalent products where other MLV products may be components.
Tetanus (caused by Clostridium tetani) is a risk to exotic mammals in multiple taxa. It is, therefore, a core vaccine in 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 given in combination with other inactivated clostridial toxins to induce additional immunity against clostridial disease, most often C perfringens Type C (beta) and D (epsilon). Using a multivalent clostridial vaccine, the initial vaccine is given at 4–8 weeks of age, followed by a booster after 3–4 weeks, with annual boosters recommended.
Exotic equids follow the protocols established for their domestic counterparts, beginning vaccination at 4–8 months with one booster 4–6 weeks after initial vaccination and then an annual booster. This protocol is often used in other perissodactylids (Tapiridae and Rhinocerotidae) and elephants.
In prosimians, tetanus toxoid is often given at a smaller volume than the recommended equine dose, because of their small body size. In other primates, tetanus coverage is provided as part of a multivalent vaccine against bacterial respiratory pathogens, including Corynebacterium diphtheriae and Bordetella pertussis , as part of the DPT or TDAP vaccination protocol. Standard human protocols are often followed for this group, with a first dose recommended at 2 months, with 2 additional boosters every 2 months, and a final booster at 15 months. Just as in people, routine boosters every 5 years are recommended.
Also see information on clostridial vaccines.
This is a core vaccine in great apes and recommended in New and Old World monkeys, although given the nature of the MLV vaccine, care must be taken to observe for possible vaccine-induced disease. Current protocols follow the CDC pediatric recommendations.
This is a core vaccine in great apes. Inactivated polio vaccine (IPV) is routinely used in the USA and must be given parenterally. Oral polio vaccine (OPV) has been historically used outside of the USA and in the face of outbreaks but is not routinely used in zoological medicine. Polio vaccination should also follow standard human pediatric protocols in young great apes.
Feline viral rhinotracheitis caused by feline herpesvirus 1 is a serious disease threat in exotic Felidae and is considered a core vaccine. Vaccination can reduce severity of clinical disease and viral shedding but may not prevent infection or viral latency. Multiple vaccine types are available, generally combined with feline calicivirus and other core vaccines. Killed vaccines are considered safest, although to provide stronger protection some institutions use MLV vaccines or booster with MLV vaccines after an initial killed series. Protocols for these vaccines follow those for domestic cats. Titers can be used to guide boosters in adults, but serology may be unreliable.
Eastern equine encephalitis, Western equine encephalitis, and West Nile virus are considered core vaccines in domestic equids. These arboviruses are important to consider geographically, with deployment as a core vaccine based on vector presence and risk. Vaccinating other mammal groups against West Nile virus or other encephalitides has been done but must be weighed based on the challenge of vaccination and risk for adverse effects (eg, sterile vaccine abscesses). These vaccines are killed and often found in combination with each other and with tetanus toxoid. There are combination products that contain killed equine influenza virus. Vaccine protocol follows that recommended for domestic equids, with a three-dose series starting between 4 and 6 months of age generally determined by the start of vector season, with a second dose given 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 canine adenovirus 2, to provide cross protection against the causative agent, 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 based on risk-based assessment for Canidae and Ursidae. Vaccine protocols follow those of domestic canids.
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. Vaccination protocols follow those of domestic species most closely related, with understanding that vaccination does not necessarily prevent shedding of the organism.
Vaccination against viral diarrhea in artiodactylid neonates can be done with a two-dose protocol administered parenterally (IM) to the dam during the final trimester of pregnancy or by dosing the calf immediately after birth orally, ideally before any nursing. The latter protocol is most often used in hand-reared animals, and vaccination of pregnant dams is based on risk to the neonate of the disease balanced against risk of administration.
Many pathogens common in domestic production ruminants are not as widely seen in zoos, but practitioners should consider deployment of noncore vaccines based on the geography and biosecurity of their institution. Most exotic mammals have a domestic animal model from which noncore vaccination protocols can be extrapolated, such as for viral respiratory pathogens of artiodactylids, such as parainfluenza-3 or infectious bovine rhinotracheitis, or noncore vaccines for domestic carnivores, such as feline coronavirus, Chlamydia felis, and feline retroviruses. In species with less translation to a domestic model, the protocol developed for the specific vaccine often guides protocol development, such as Bordetella bronchiseptica, which in Suidae and Canidae has been used to prevent disease with both MLV or killed vaccines. Exotic mammals, including koalas of Vombatidae and sloths of order Pilosa, are also susceptible to this pathogen; vaccination with a killed vaccine may be considered.
Evolving recommendations for vaccination against many infectious diseases can be found through professional group guidelines, which evaluate a pathogen's effects on exotic mammals and the safety of the vaccine in the face of disease risk. The American Association of Zoo Veterinarians' Infectious Disease Manual provides information on species susceptibility classified by disease, and the Association of Zoos and Aquaria Species Survival Plan and Taxon Advisory Groups often have recommendations for vaccination protocols based on taxa found in . The European Association of Zoo and Wildlife Veterinarians Transmissible Disease Handbook is also a helpful resource.
Vaccination of valuable animals could be considered in the event of an outbreak. Influenza vaccines exist for Equidae, Canidae, and Suidae as a killed vaccine to prevent the most pathogenic strains in the face of an outbreak. Differing hemagglutinin (H) or neuraminidase (N) subtypes may be used in vaccines to provide adequate DIVA strategy. Governmental approval may be required for this kind of vaccine use, such as for vaccinia (cowpox) which is currently limited by the CDC to distribution solely to healthy care and biomedical laboratory workers with exposure risk.