Veterinary · Clinical · also MSVE VMD-512
Health care of zoo and free-ranging wild animals: management and nutrition, chemical immobilisation, the major wildlife diseases, wildlife law and forensics.
In the exams: SAVC wildlife 10; ACZM and ECZM specialist colleges
Wildlife, zoo animal and conservation medicine is the veterinary care of non-domestic animals: animals kept in zoos, safari parks, rescue centres and breeding centres, and animals living free in national parks, forests, wetlands and the edges of farms and towns. It borrows from every other veterinary subject, but three things make it different. First, the patients are hundreds of species whose anatomy, physiology, diet and drug responses are often poorly described, so the clinician reasons from comparative principles rather than from a single species textbook. Second, most patients cannot be handled safely without capture and chemical immobilisation, and the restraint itself can kill. Third, the client is often a population, a protected area or a species rather than an owner, so decisions weigh welfare, conservation value, public health and the law together.
The subject matters in practice because wildlife sits at the meeting point of animal, human and environmental health. Most emerging infectious diseases of people are zoonoses, and a large share of these come from wildlife. Wild species maintain diseases that defeat livestock control programmes: bovine tuberculosis in African buffalo, badgers, brushtail possums and white-tailed deer; the SAT types of foot-and-mouth disease in African buffalo; rabies in foxes, jackals, raccoons, skunks and bats. In India, Kyasanur Forest disease is first detected through deaths of langurs and bonnet macaques, and surra kills tigers and leopards fed infected meat. The veterinarian who understands these interfaces protects herds, people and threatened species at the same time.
This manual follows the ten units of the veterinary curriculum: zoo animal breeding, management and nutrition; chemical immobilisation and capture myopathy; tuberculosis, anthrax, rabies, foot-and-mouth disease, Kyasanur Forest disease and surra in wildlife; wildlife legislation; and wildlife forensics. Within those units it also covers preventive medicine and quarantine, the major diseases of elephants, big cats, primates, ungulates, birds and reptiles, rescue and rehabilitation, and human-wildlife conflict. Drug doses are deliberately not given: immobilising agents, especially the potent opioids, are species-specific, controlled and dangerous to people, and must be taken from a current specialist formulary and your national rules, never from a general text.
The subject is examined in the South African registration examination, in Indian PhD and recruitment examinations, and in depth by the American and European Colleges of Zoological Medicine. Law differs by country; this manual gives the international frame and the main national acts by name, and tells you where to check the current text.
Conservation medicine, now usually discussed under the wider headings of One Health and planetary health, is the study of how the health of wildlife, domestic animals, people and ecosystems affect one another, and the use of that knowledge to protect biodiversity. The unit of concern shifts from the individual to the population: a clinician may treat one rhinoceros intensively because each animal matters to a population of a few dozen, yet decline to treat a common species in a large population when intervention would change nothing and carry risk. Wildlife disease matters to conservation in several ways. Disease can drive small populations towards extinction, as canine distemper did to black-footed ferrets in North America and as rabies and distemper have done to African wild dogs and Ethiopian wolves. Disease from wildlife can harm livestock economies and trade, as foot-and-mouth disease from buffalo does in southern Africa. Disease from wildlife can harm people directly, as with rabies, Kyasanur Forest disease, Ebola, Nipah and avian influenza. And people and livestock can harm wildlife, as when great apes catch human respiratory viruses or wild carnivores catch distemper from village dogs. Most emerging infectious diseases of people are zoonoses, most from wildlife, driven by land-use change, bushmeat hunting and trade, and animal movement.
Interface epidemiology uses a precise vocabulary. A maintenance (reservoir) host is a population in which an infection persists indefinitely without reintroduction from elsewhere. A spillover or dead-end host becomes infected but cannot sustain the infection on its own; if contact with the maintenance host stops, infection dies out in the spillover population. Lions and leopards in Kruger National Park are spillover hosts of Mycobacterium bovis from African buffalo; people are dead-end hosts of Kyasanur Forest disease virus. An amplifying host multiplies an agent and increases transmission, as monkeys do for KFD virus by feeding large numbers of infected ticks. A sentinel is a species whose illness or seroconversion signals that an agent is present, such as dead langurs for KFD or howler monkeys for yellow fever in South America. Whether a wild species is a true maintenance host depends on population density, social structure and contact rates, not on the species alone: badgers maintain bovine tuberculosis in Britain and Ireland, while in some other countries they are spillover hosts. Control at the interface rarely relies on one tool. Options include separation (fences, herding, keeping livestock away from water points or carcasses), vaccination of livestock or of wildlife, test-and-remove in managed wildlife, culling, managing feeding sites that concentrate animals, and, for trade, zoning and commodity-based approaches. Each has welfare, ecological and social costs.
Wildlife disease surveillance is either active (planned sampling of live-captured, hunted or culled animals) or passive (investigation of animals found dead or sick). Passive surveillance of carcasses is cheap and good at detecting new or high-mortality agents, such as anthrax, avian influenza or KFD in monkeys, but it is biased towards visible, large or accessible species. Active surveillance can estimate prevalence but needs capture, permits and enough samples. To show freedom from disease at a design prevalence, the sample size for a large population is approximately the natural logarithm of one minus the confidence level, divided by the natural logarithm of one minus the design prevalence, assuming a perfect test; real tests in wildlife are rarely validated, so true sensitivity and specificity are often unknown. The World Organisation for Animal Health (WOAH) requires member countries to report listed diseases in wildlife as well as domestic animals and also collects voluntary reports of some non-listed wildlife diseases. National rules on notifiable disease apply to wild animals too: a veterinarian who confirms anthrax, rabies or foot-and-mouth disease in a wild animal must notify the official veterinary service. At any mortality event, record location, species, numbers and ages, sample several carcasses fresh and fixed, and protect staff.
A modern zoo exists for conservation, education, research and recreation, and its legitimacy depends on the welfare of the animals it keeps. Welfare is assessed with frameworks such as the Five Freedoms and, increasingly, the Five Domains model, which considers nutrition, physical environment, health and behavioural interactions as inputs to the fifth domain, the animal's mental state. Enclosures should meet the species' needs for space, complexity, substrate, refuges, climate and social grouping; a solitary species housed with conspecifics, or a social species kept alone, suffers chronic stress. Thermal needs are critical for ectotherms: reptiles need a temperature gradient that spans their preferred optimal temperature zone, plus ultraviolet B light for many species. Environmental enrichment adds to the environment to increase species-typical behaviour and choice; it is usually grouped as food-based, physical (structural), sensory, cognitive and social enrichment. Stereotypic behaviours, repetitive invariant behaviours without obvious function such as pacing in carnivores, swaying in elephants and bar-biting, are a warning that the environment or management does not meet the animal's needs, although a stereotypy can persist after conditions improve. Operant conditioning with positive reinforcement lets keepers train animals to present a foot, open the mouth, accept injections or stand for blood sampling, which reduces the need for general anaesthesia.
Preventive medicine is the centre of zoo practice because sick wild animals hide signs until disease is advanced. A programme includes routine observation and records; regular body weights and body condition scoring; faecal parasitology at intervals; vaccination where safe and justified; tuberculosis screening of primates, elephants and other susceptible taxa; dental and foot care; pest and vector control; hygiene and zoning of keeper routes; safe food handling; staff occupational health; and a full necropsy on every animal that dies. Necropsy is the most valuable surveillance tool a collection has, because it finds diseases that were never seen in life and tells the clinician what is circulating. Vaccination of exotic species carries a specific rule: modified-live vaccines designed for domestic animals can cause the disease they are meant to prevent in some wild species. Modified-live canine distemper vaccines have caused fatal distemper in black-footed ferrets, red pandas and other susceptible carnivores, so killed, recombinant or species-tested products are used, and only inactivated rabies vaccines are used in non-domestic carnivores.
Every animal arriving at a collection is quarantined before joining resident animals. Quarantine is a separate area with its own staff or staff who work there last, its own equipment, footbaths and waste handling. The period is set by the institution and the national regulator and varies by taxon; many zoos use a minimum of about thirty days for most mammals and longer periods for primates, elephants, ungulates from tuberculosis-risk sources and species with regulatory testing requirements. During quarantine the animal is observed, weighed, examined (often under anaesthesia), sampled for repeated faecal parasitology, haematology, biochemistry and serology, tested for tuberculosis where relevant, vaccinated, given parasite control, and marked or identified by microchip, tattoo, ring or band. Any animal that dies in quarantine receives a full necropsy. Zoo staff are part of the risk: people with active respiratory infections should not work with great apes, and staff working with macaques need a plan for Macacine herpesvirus 1 (herpes B) exposure, which is usually harmless in macaques but can cause fatal encephalitis in people.
Elephants: elephant endotheliotropic herpesvirus (EEHV) haemorrhagic disease kills young Asian elephants, mostly between about one and eight years of age, often within days; many collections monitor at-risk calves with blood PCR so that antiviral drugs and supportive care, including plasma, start before signs appear. Elephants also contract tuberculosis, usually Mycobacterium tuberculosis acquired from people, and suffer foot disease, arthritis and obesity in poor environments. Big cats: canine distemper killed about a third of the Serengeti lions in 1994 after spillover from domestic dogs; feline panleukopenia, feline herpesvirus and calicivirus affect captive cats; captive cheetahs suffer gastritis, renal amyloidosis and veno-occlusive disease; tigers in Thailand died of H5N1 avian influenza after being fed infected chicken carcasses. Primates: tuberculosis, measles (often fatal in marmosets and dangerous in great apes), herpes B as a zoonosis from macaques, Ebola virus disease in wild gorillas and chimpanzees, and human respiratory viruses in habituated wild apes. Ungulates: malignant catarrhal fever from wildebeest (alcelaphine herpesvirus 1) or sheep (ovine herpesvirus 2) kills susceptible deer, bison and cattle; chronic wasting disease is a prion disease of cervids in North America, Scandinavia and South Korea; peste des petits ruminants has caused mass mortality of saiga. Birds: highly pathogenic avian influenza, avian malaria in outdoor penguins, aspergillosis in penguins and raptors, avian tuberculosis, psittacine beak and feather disease, pododermatitis (bumblefoot) and lead poisoning. Reptiles: inclusion body disease (reptarenavirus) in boas and pythons, cryptosporidiosis in snakes, mycoplasmal upper respiratory disease in tortoises, and husbandry diseases such as metabolic bone disease and hypovitaminosis A. Amphibians: chytridiomycosis has caused declines and extinctions worldwide.
Zoo populations are small, closed and founded by few animals, so their genetic health must be managed deliberately. A founder is an animal from the wild with no known relationship to others in the population. Over generations, small populations lose genetic diversity by random genetic drift and become inbred. The rate of loss depends on the effective population size, Ne, the size of an idealised population that would lose diversity at the same rate. Ne is usually much smaller than the census size because of unequal sex ratios, unequal family sizes and fluctuating numbers. For an unequal sex ratio, Ne = 4NmNf / (Nm + Nf), where Nm and Nf are the numbers of breeding males and females. The expected increase in inbreeding per generation is 1/(2Ne), and the proportion of heterozygosity retained after t generations is (1 − 1/(2Ne)) to the power t. Inbreeding depression, reduced survival and fertility in the offspring of related parents, was shown across many zoo mammal species by higher juvenile mortality in inbred young. A widely used goal for cooperatively managed zoo populations is to retain about 90 per cent of the founders' gene diversity for 100 years, although many programmes cannot reach it. Studbooks record the pedigree of every animal in a regional or global population. Regional programmes, such as Species Survival Plans in North America and EAZA Ex situ Programmes in Europe, use studbook data to recommend which animals should breed. The main tool is mean kinship: pairing animals with the lowest mean kinship, which are the most genetically under-represented, maximises retained diversity and slows inbreeding. In India, the Central Zoo Authority coordinates conservation breeding programmes for endangered species in designated zoos.
Reproductive physiology varies enormously across zoo species, and knowing it prevents mismanagement. Elephants have long oestrous cycles of roughly fourteen to sixteen weeks and an unusual pair of luteinising hormone surges about three weeks apart, of which only the second is followed by ovulation; gestation lasts about twenty-two months. Adult bull elephants show musth, a period of raised testosterone, temporal gland secretion, urine dribbling and aggression, which affects both safety and breeding. Giant pandas have a single short oestrus a year and delayed implantation. Cheetahs have low genetic diversity and a high proportion of abnormal spermatozoa. Many felids are induced ovulators. Non-invasive monitoring of reproductive and adrenal hormones in faeces or urine lets clinicians track cycles, pregnancy and stress without handling. Assisted reproductive technologies include semen collection (by electroejaculation under anaesthesia, by training, or post-mortem from the epididymis), cryopreservation in genome resource banks, artificial insemination, which has produced offspring in elephants, giant pandas, rhinoceroses and many others, and in some species embryo transfer and in vitro fertilisation.
Because space in zoos is limited, controlling breeding is as important as promoting it. Options include separation of sexes, surgical sterilisation, and reversible contraception. Gonadotropin-releasing hormone (GnRH) agonist implants first stimulate, then suppress, the reproductive axis; the initial stimulation can cause oestrus or ovulation, so additional measures are needed for the first weeks. Progestin implants and injections are effective, but long-term progestin use in felids has been associated with endometrial hyperplasia, uterine disease and mammary tumours, so they are used with caution in cats. Immunocontraception with porcine zona pellucida vaccines is used in some free-ranging populations, for example wild horses and elephants in parts of southern Africa. When a mother cannot or will not rear her young, hand-rearing may be needed. Its risks include imprinting on people, poor social and maternal behaviour in adulthood, and nutritional disease from inappropriate milk replacers: milk composition differs greatly between species, with marine mammals producing very high-fat milk and marsupials changing milk composition through lactation. Colostrum or plasma is given where the neonate depends on passive transfer of immunity. Wherever possible, young are reared by the mother or fostered to a conspecific.
Zoo nutrition starts by placing each species in a feeding guild and digestive type, then building a diet that meets nutrient needs while allowing natural feeding behaviour. Carnivores (felids, mustelids, many raptors) eat meat and whole prey; insectivores eat invertebrates; nectarivores and frugivores eat sugars; herbivores eat plant cell wall that they ferment with microbes. Herbivores ferment either in the foregut (ruminants, camelids, colobine monkeys such as langurs, kangaroos, and the hippopotamus) or in the hindgut (equids, rhinoceroses, tapirs and elephants). Among ruminants, browsers or concentrate selectors such as giraffe, moose and many duikers eat leaves, shoots and fruits; grazers such as buffalo, wildebeest and many cattle-like species eat grass; intermediate feeders switch with season. Browsers do poorly on grass hay and high-starch concentrates; feeding them grass-based diets can cause rumen acidosis, poor coat and wasting. Colobine monkeys, as foregut fermenters, are prone to bloat and digestive upset on fruit-rich diets designed for other primates. Energy requirements scale with metabolic body size. Basal metabolic rate in placental mammals is approximately 70 kcal multiplied by body weight in kilograms raised to the power 0.75; maintenance requirements are a multiple of this that varies with activity, climate and species. Because of the exponent, small animals need much more energy per kilogram than large ones. Diets are formulated on a dry-matter basis.
Felids are obligate carnivores: they require dietary taurine, arachidonic acid and preformed vitamin A, and a diet of muscle meat alone is severely deficient in calcium relative to phosphorus. Feeding unsupplemented muscle meat causes nutritional secondary hyperparathyroidism, with soft, fracturing bones in growing cats; whole prey or meat with bone or a calcium supplement prevents it. The dietary calcium-to-phosphorus ratio is usually targeted between about 1:1 and 2:1 for most vertebrates. Fish-eating animals such as seals, sea lions, penguins and some otters fed frozen fish need thiamine supplements, because some fish contain thiaminase and storage destroys thiamine; deficiency causes neurological signs. They also need vitamin E, because the polyunsaturated fat in stored fish oxidises. Anthropoid primates (monkeys and apes), like guinea pigs and people, cannot synthesise vitamin C and need it in the diet. New World monkeys need vitamin D3 rather than D2 and are prone to metabolic bone disease without it or without ultraviolet light. Modern primate diets rely more on leafy greens, vegetables and nutritionally complete biscuits and much less on cultivated fruit, which is higher in sugar and lower in fibre than wild fruit and is linked to obesity and dental disease.
Metabolic bone disease of captive reptiles is usually nutritional secondary hyperparathyroidism caused by low dietary calcium, a high phosphorus diet, or lack of ultraviolet B light, which reptiles need to make vitamin D3 in the skin. Signs include soft jaws, swollen limbs, fractures, deformity and tremors. Insects fed to reptiles are low in calcium, so they are dusted with calcium or gut-loaded before feeding. Chelonians fed vitamin A-deficient diets develop squamous metaplasia, swollen eyelids, respiratory disease and aural abscesses. Iron storage disease (haemosiderosis) is common in species whose wild diets are low in available iron when they are fed iron-rich captive diets: browsing rhinoceroses (black and Sumatran), tapirs, lemurs and several frugivorous and insectivorous birds such as toucans, mynahs and starlings. Prevention uses low-iron diets and limits vitamin C-rich foods that increase iron absorption. Captive browsing ungulates and rhinoceroses can also have low vitamin E status. Elephants in captivity are prone to obesity, which worsens foot and joint disease and may affect fertility; their diets should be based on hay and browse with limited produce and concentrates.
Capture is the most dangerous routine procedure in wildlife practice, for the animal and for people. Planning asks: why must this animal be captured, what is the least stressful method, who does what, what will be done if the animal is injured, overheats or stops breathing, and how will people be protected. Capture should be done in the cool part of the day, with chase time kept as short as possible. Physical methods include nets for birds and small mammals, crush or squeeze cages built into zoo enclosures, drop-nets, net guns, box traps, and for groups of antelope and zebra, mass capture into a funnel of plastic sheeting leading to a holding pen (a boma) and then a crate. Birds are restrained with towels and the wings held against the body; large raptors are controlled at the feet first. Venomous snakes are handled with hooks and clear tubes, never by hand. Physical restraint is quick and avoids drug risks but is stressful, so for large, dangerous or valuable animals chemical immobilisation is normally used, often combined with physical methods.
Immobilising drugs are chosen for potency (so a dose fits into a dart), speed of induction, safety margin and, ideally, reversibility. The main groups are: potent opioids such as etorphine, carfentanil and thiafentanil, which are thousands of times more potent than morphine and are used especially in ungulates, rhinoceroses and elephants; alpha-2 adrenergic agonists such as xylazine, detomidine and medetomidine, which sedate and relax muscles and potentiate other drugs; dissociative anaesthetics such as ketamine and the combination tiletamine with zolazepam, widely used in carnivores and primates; butyrophenone tranquillisers such as azaperone; benzodiazepines such as midazolam and diazepam; and the mixed opioid butorphanol, used in combinations. Most protocols combine an opioid or dissociative with an alpha-2 agonist or tranquilliser so that each component can be given at a lower amount. Dissociatives used alone in large felids can cause muscle rigidity and convulsions, so they are combined with a sedative. Reversal agents are a major safety advantage: naltrexone, naloxone and diprenorphine antagonise opioids, with naltrexone being long-acting and least likely to allow renarcotisation; atipamezole, yohimbine and tolazoline antagonise alpha-2 agonists. Dissociatives have no specific antagonist. Drugs are delivered by hand injection, pole syringe, blowpipe or dart projector powered by compressed air, carbon dioxide or a powder charge. The kinetic energy of a dart is half its mass times velocity squared, so doubling velocity quadruples impact energy; darts are placed into large muscle masses of the hindquarter or shoulder, avoiding the head, neck, thorax and abdomen. All doses vary by species, body size, condition, environment and drug formulation — confirm against a current specialist formulary, the product label where one exists and your national formulary.
From induction to recovery the team monitors depth of anaesthesia, respiratory rate and pattern, heart rate, mucous membrane colour, capillary refill, body temperature and, where possible, pulse oximetry and capnography. Common complications are: respiratory depression and hypoxaemia, which are marked with potent opioids in rhinoceroses and other large ungulates and are treated with oxygen insufflation and partial or full reversal; hyperthermia from chase, exertion, sun and drug effects, which is treated by cooling with water and shade and by ending the procedure early; regurgitation, bloat and aspiration in ruminants, prevented by keeping them sternal with the head up and nose down so saliva drains; and trauma from falls, darts or fighting. Positioning matters by species: elephants are usually kept in lateral recumbency with the trunk kept open, and giraffes need head and neck support and rapid reversal because of the risk of regurgitation, airway problems and injury during induction and recovery. Renarcotisation, a return of opioid effects after reversal, occurs when the antagonist wears off before the agonist; it is why animals are watched after release. Recovery is planned away from water, cliffs and aggressive conspecifics.
Etorphine, carfentanil and thiafentanil can kill a person through a needle-stick, a splash into the eye or mouth, or absorption through broken skin, in amounts far smaller than a single animal dose. Safe practice is standard in every jurisdiction that permits their use: the drugs are stored and recorded as controlled substances under national law; they are handled only by trained people wearing gloves and eye protection; darts are loaded with the needle capped and pointing away from people; a second trained person is always present; and an opioid antagonist for human use, with the means to give it and to support breathing, is drawn up and ready before the drug container is opened. Anyone exposed is treated immediately as an emergency, even if they feel well, and transported to medical care. Alpha-2 agonists such as medetomidine are also hazardous to people in concentrated wildlife formulations. National law determines who may possess, use and record these drugs, and in many countries their use is restricted to veterinarians with specific licences.
Capture myopathy (also called exertional rhabdomyolysis or overstraining disease) is a non-infectious, often fatal disease of wild animals that follows pursuit, capture, restraint and transport. It is most common in ungulates such as antelope, deer and giraffe, and in some birds such as flamingos, cranes and bustards, but occurs in many taxa including marsupials and marine mammals. The mechanism combines extreme sympathetic stimulation with intense muscular exertion. Muscle switches to anaerobic metabolism and lactic acid accumulates, causing metabolic acidosis; hyperthermia develops; muscle cells are damaged and release potassium, myoglobin and enzymes such as creatine kinase and aspartate aminotransferase. Myoglobin damages the renal tubules, causing myoglobinuric nephrosis and renal failure. Four clinical forms are classically described. Capture shock syndrome occurs during or within hours of capture, with depression, rapid breathing, hyperthermia and death. Ataxic myoglobinuric syndrome appears hours to days later with ataxia, torticollis and dark brown urine; mildly affected animals may survive, but severe cases die of renal failure. Ruptured muscle syndrome appears a day or more later with a dropped hindquarter caused by rupture of the large hind-limb muscles, especially the gastrocnemius. Delayed peracute syndrome affects animals that seemed normal but die suddenly when stressed again, often days to weeks later, possibly from ventricular fibrillation caused by hyperkalaemia and acidosis.
Risk rises with long or repeated chases, high ambient temperature and humidity, fear and handling, prolonged transport, crowding, poor body condition, previous capture, and drug protocols that allow excitement. Prevention is the only reliable approach: capture in the cool hours, plan routes to limit chase distance and time, use experienced teams, reduce noise and visual stimulation by blindfolding and quiet handling, monitor temperature and cool early, keep handling short, use tranquillisers to reduce stress during holding and transport, and release or crate quickly. Some practitioners give vitamin E and selenium before capture of species at risk; its preventive value is uncertain. Treatment of established disease is supportive and often unsuccessful: cooling, intravenous fluids to correct dehydration and protect the kidneys, correction of acidosis where it can be measured, analgesia, sedation to reduce further stress, and nursing in quiet, padded, shaded surroundings. Diagnosis rests on history, clinical signs, high muscle enzymes, myoglobinuria and, at necropsy, pale or streaked skeletal and heart muscle, haemorrhage, dark swollen kidneys and microscopic muscle necrosis with myoglobin casts in the renal tubules. Because it can appear weeks later, translocations need post-release monitoring.
Tuberculosis in wildlife is caused mainly by members of the Mycobacterium tuberculosis complex, especially M. bovis, and in elephants and primates frequently by M. tuberculosis acquired from people. Several wild species are maintenance hosts of M. bovis that frustrate cattle eradication programmes: the European badger in Britain and Ireland, the brushtail possum in New Zealand, white-tailed deer in Michigan in the United States, wild boar and red deer in parts of the Iberian Peninsula, and the African buffalo in Kruger National Park and other parks in southern Africa, where the infection spread northwards through the buffalo population after introduction from cattle. From buffalo it spills over into lions, leopards, kudu, warthogs, baboons and other species; in lions it causes wasting, lameness and death. Bovine tuberculosis is a threat to rare species such as the black rhinoceros and to the movement of buffalo for conservation and trade. Avian tuberculosis (M. avium) is common in captive birds. The zoonotic risk runs both ways: keepers can infect elephants and primates, and infected animals can infect keepers and visitors.
Diagnosing tuberculosis in wildlife is difficult because most tests were developed for cattle or people and are poorly validated in other species. The intradermal tuberculin test is used in many species. In non-human primates it is traditionally given in the upper eyelid (palpebral test) and read for swelling and drooping at about 24, 48 and 72 hours; in deer and buffalo a comparative skin test with avian and bovine tuberculin is used. Interferon-gamma release assays have been adapted for several species, including buffalo and lions. In elephants, the traditional reference test is culture of trunk wash samples, which is specific but insensitive; serological assays that detect antibodies to mycobacterial antigens are used for screening. Necropsy with culture or PCR of lesions remains the definitive test. Because sensitivity and specificity are uncertain, a positive screening result in a low-prevalence population has a low positive predictive value and needs confirmation. Control in captivity uses quarantine testing, staff screening, separation and, for elephants, treatment with human anti-tuberculosis drugs under expert guidance with monitoring of blood drug levels; euthanasia is considered for many other species. In free-ranging wildlife, control combines limiting contact with cattle, test-and-remove in managed populations such as buffalo, vaccination with BCG (used, for example, in badgers), culling in some programmes, and stopping supplementary feeding that concentrates deer and boar.
Anthrax is caused by Bacillus anthracis, a Gram-positive, spore-forming, capsulated bacillus whose virulence depends on a poly-D-glutamic acid capsule and a three-part toxin (protective antigen, lethal factor and oedema factor). Spores persist in soil for decades. Herbivores are most susceptible; carnivores are more resistant; people are infected through skin, inhalation or ingestion. Anthrax is endemic in several African parks, where outbreaks recur in herbivores such as zebra, wildebeest, springbok and elephant in Etosha, kudu and other browsers in Kruger, and hippopotamuses in parts of Uganda and Zambia. In Kruger, blowflies feeding on carcasses deposit infected droplets on vegetation, which browsers then eat. Anthrax caused by a related organism, Bacillus cereus biovar anthracis, has killed wild chimpanzees and other mammals in West and Central African forests. Animals typically die suddenly; the carcass bloats quickly, rigor mortis may be absent, and dark, unclotted blood may ooze from the natural orifices. A suspected anthrax carcass must not be opened, because exposure to air allows the vegetative bacilli to form spores and contaminate the site. Diagnosis uses a thin blood smear from a peripheral vein or ear, stained with polychrome methylene blue to show square-ended bacilli in short chains with a pink capsule (the M'Fadyean reaction), culture and PCR. Control is by notification, safe disposal of carcasses by burning or deep burial according to national rules, disinfection, protection of people, and in some programmes vaccination of livestock or of small high-value wildlife populations with the live attenuated spore vaccine delivered by dart.
Rabies is caused by rabies virus, a lyssavirus in the family Rhabdoviridae. Dogs cause almost all human rabies deaths worldwide, but distinct virus variants are maintained in wild carnivores and bats. Major wildlife reservoirs include the red fox in Europe, raccoons, striped skunks, foxes and coyotes in North America, insectivorous bats throughout the Americas, vampire bats in Latin America, which also infect cattle, jackals and yellow mongooses in southern Africa, and the small Asian mongoose in some Caribbean islands. In Namibia, large epidemics in kudu have been reported, with spread between kudu suspected rather than only through carnivores. Rabies is a conservation problem for endangered carnivores: outbreaks introduced from domestic dogs have killed large proportions of Ethiopian wolf populations and contributed to losses of African wild dogs. Responses include vaccinating domestic dogs around protected areas and vaccinating the endangered species itself by injection or oral bait. In zoos, only inactivated rabies vaccines are used in exotic carnivores, and staff at risk receive pre-exposure vaccination. Diagnosis is by the direct fluorescent antibody test on fresh brain tissue, the WOAH reference test; histological Negri bodies are less sensitive. Every bite or scratch from a suspect wild animal is managed with immediate wound washing and medical assessment for post-exposure prophylaxis.
Oral rabies vaccination of wildlife is one of the great successes of wildlife disease control. Baits containing a live attenuated rabies vaccine, or a recombinant vaccinia virus expressing the rabies glycoprotein, are distributed by aircraft or by hand across the range of the reservoir species. Repeated campaigns in western and central Europe eliminated fox rabies from large areas, and oral vaccination campaigns in North America have been used to contain raccoon and coyote rabies. Success depends on bait uptake by enough of the target population to raise herd immunity, timing campaigns when young animals are foraging, avoiding non-target uptake, and monitoring with bait-marker biomarkers, serology and continued surveillance of suspect animals.
Foot-and-mouth disease (FMD) is caused by an aphthovirus in the family Picornaviridae with seven serotypes: O, A, C, Asia 1 and the South African Territories types SAT 1, SAT 2 and SAT 3. In sub-Saharan Africa, the African buffalo is the maintenance host of the SAT types. Buffalo are usually infected as calves, show few or no signs, and can remain persistently infected carriers for years, sometimes in several serotypes at once. Transmission from buffalo to cattle is uncommon but does occur, mostly when infected young buffalo are in close contact with cattle; impala are frequently infected and may link buffalo and cattle. Southern African countries have used veterinary cordon fences to separate buffalo from cattle and create FMD-free zones recognised by WOAH, allowing beef exports. These fences have fragmented wildlife migrations. Commodity-based trade is an alternative approach that manages risk in the product, through processing steps such as deboning and maturation of beef, rather than requiring the whole area to be free of infection. Outside Africa, wild ungulates such as wild boar, deer, saiga and gazelles can be infected, but they are generally regarded as spillover rather than long-term maintenance hosts. Elephants are occasionally reported with clinical FMD. Buffalo moved for conservation or trade must be certified free of FMD and other controlled diseases under national law, which is why disease-free buffalo breeding programmes exist in South Africa.
Kyasanur Forest disease (KFD), known locally as monkey fever, is a tick-borne viral haemorrhagic fever of southern India. It was recognised in 1957 in Shimoga (now Shivamogga) district of Karnataka, when deaths of monkeys in the Kyasanur forest were followed by illness in people. KFD virus is a flavivirus of the tick-borne encephalitis group; a closely related virus, Alkhurma haemorrhagic fever virus, occurs in the Arabian Peninsula. The main vector is the ixodid tick Haemaphysalis spinigera, whose nymphs bite monkeys and people; other Haemaphysalis species are involved. Small mammals such as rodents and shrews help maintain the virus. Two monkey species, the black-faced langur (Semnopithecus entellus) and the red-faced bonnet macaque (Macaca radiata), develop high viraemia and die, amplifying the virus by infecting large numbers of feeding ticks and dropping infected ticks where they die. Cattle are important hosts for adult ticks and so increase tick numbers, but do not develop significant viraemia. People are dead-end hosts infected by nymph bites in forests, especially during the dry season from about November to June. The human disease is often biphasic: sudden fever, headache, myalgia and haemorrhages, followed in some patients by a second phase with neurological signs; reported case fatality is a few per cent. It has since spread to Kerala, Goa, Maharashtra and Tamil Nadu.
Because monkeys die before human cases appear, the investigation of monkey deaths is the backbone of KFD surveillance. Forest and health staff report dead monkeys; a team collects samples from the carcass with full personal protection, because the virus is a high-containment pathogen, and collects ticks from the carcass and the area around it. A positive result triggers control in a radius around the site: acaricide treatment of the ground near the carcass, burning or burial of the carcass, warnings to villagers, use of tick repellents, protective clothing for forest workers, and vaccination of people in affected villages. A formalin-inactivated tissue-culture vaccine has been used for decades in India in multiple doses with boosters, though its supply has been interrupted at times; its field effectiveness has been questioned, and people are told to combine it with personal protection. Veterinarians do safe monkey necropsy and tick control on forest-grazing cattle.
Surra is the disease caused by Trypanosoma evansi, a salivarian trypanosome of the subgenus Trypanozoon with a small subterminal kinetoplast, an undulating membrane and a free flagellum. It is the most widely distributed pathogenic trypanosome. Unlike the tsetse-transmitted trypanosomes, T. evansi is transmitted mechanically by biting flies, especially tabanids and stable flies, which carry blood on their mouthparts between hosts; vampire bats act as both vector and reservoir in Latin America. Carnivores, including dogs and big cats, are infected by eating fresh meat or viscera of infected animals. The disease is acute and often fatal in horses, camels and dogs, while cattle and buffalo often carry the parasite with mild or no signs and act as reservoirs. Outbreaks have killed tigers, leopards and lions in Indian zoos, linked to feeding meat from infected animals, and infections are reported in captive and free-ranging elephants, deer and other wild species. Signs include intermittent fever, anaemia, weight loss, oedema of the limbs and ventral body, corneal opacity and, in carnivores, nervous signs. Diagnosis uses wet blood films and stained thin smears during fever peaks, concentration methods such as the buffy coat or haematocrit centrifugation technique, serology such as card agglutination tests, and PCR; parasitaemia fluctuates, so a single negative smear does not exclude infection. Trypanocidal drugs used against T. evansi include quinapyramine, diminazene aceturate, suramin, isometamidium and melarsomine, with marked differences in safety between species — confirm drug, dose and species suitability against the product label and your national formulary. Prevention in zoos means sourcing meat from inspected, healthy animals, controlling biting flies, and screening herbivores and other at-risk animals.
International wildlife law sets the frame within which national law operates. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) was signed in Washington in 1973 and came into force in 1975; nearly every country is a Party. It regulates international trade, not domestic use, through three appendices. Appendix I lists species threatened with extinction; commercial trade in wild specimens is generally prohibited, and trade for non-commercial purposes such as scientific research or conservation breeding needs both an export permit and an import permit. Appendix II lists species not necessarily threatened now but which may become so unless trade is controlled; an export permit is required, issued only after a scientific authority finds the trade not detrimental to the species' survival (a non-detriment finding). Appendix III lists species protected by a Party that has asked others for help in controlling trade. Each Party has a management authority that issues permits and a scientific authority that advises it. CITES covers parts and derivatives, including blood, tissue and other diagnostic samples, so a veterinarian who sends samples from a listed species across a border needs CITES documents unless a national simplified procedure applies. The Convention on Biological Diversity (1992) and its Nagoya Protocol on access and benefit-sharing can also apply to research samples, and the WOAH Terrestrial Animal Health Code governs disease aspects of trade. The IUCN Red List classifies extinction risk in categories from Least Concern through Near Threatened, Vulnerable, Endangered and Critically Endangered to Extinct in the Wild and Extinct, with Data Deficient where information is lacking. A species' Red List category and its CITES appendix are separate decisions and do not always match.
National laws protect species, regulate zoos, control dangerous drugs and set animal welfare duties; the details differ, and practitioners must check the current text. In India the Wild Life (Protection) Act 1972 prohibits hunting of scheduled wild animals except as the Act allows, for example where the Chief Wild Life Warden permits it because an animal has become dangerous to human life; it creates national parks, sanctuaries, conservation reserves and community reserves; and it regulates trade in wildlife articles. The 2022 amendment rationalised the schedules into four: Schedule I for animals with the highest protection, Schedule II for other protected animals, Schedule III for plants and Schedule IV for specimens listed in the CITES appendices, and strengthened the Act's implementation of CITES. The Central Zoo Authority, set up in 1992 under the Act, recognises and regulates zoos and coordinates conservation breeding; the National Tiger Conservation Authority and the Wildlife Crime Control Bureau are also statutory bodies. In the United States, the Endangered Species Act 1973 protects listed species and their habitats, the Lacey Act makes it an offence to trade wildlife taken in breach of any law, and the Animal Welfare Act requires exhibitors to be licensed and inspected. In the European Union, the Zoos Directive (1999/22/EC) requires member states to license and inspect zoos with conservation and welfare duties, the Habitats and Birds Directives protect species and sites, and the wildlife trade regulations implement CITES with stricter annexes. The United Kingdom has the Zoo Licensing Act 1981. In South Africa, the National Environmental Management: Biodiversity Act 2004 and its regulations on threatened or protected species govern wildlife, while the Animal Diseases Act 1984 controls diseases such as foot-and-mouth disease and controls the movement of buffalo. In every country, controlled-drug law governs immobilising opioids, and firearms law governs dart and euthanasia firearms.
Wildlife rehabilitation is the treatment and temporary care of injured, sick, orphaned or displaced wild animals with the aim of returning them to the wild. On admission, triage decides between three outcomes: treatment for release, permanent captivity where the animal has a clear purpose and an acceptable quality of life, or euthanasia. Euthanasia is right when injuries prevent a good life in the wild or captivity, such as a raptor with a wing amputation. Release criteria include full physical fitness, normal species-specific behaviour such as fear of people, foraging and flight, freedom from infectious disease that could harm wild populations, release into suitable habitat (usually near where the animal was found, for territorial species) and legal permission. Hand-reared young must not imprint on people; techniques include rearing with conspecifics, minimal contact and, for some birds, puppets. Soft release, with a period in an enclosure at the release site, suits many species; hard release suits others. Post-release monitoring shows whether rehabilitation works. Conservation translocations and reintroductions follow the IUCN guidelines on reintroductions and other conservation translocations, which require a disease risk analysis, among other steps. Legal permits are needed in most countries to hold or rehabilitate protected species.
Human-wildlife conflict covers interactions in which wild animals damage crops, kill livestock or injure people, and the responses of people, which often include retaliatory killing. Examples are crop-raiding elephants, livestock-killing leopards and tigers, and crop-raiding monkeys. Retaliatory poisoning of carcasses with agricultural pesticides kills not only the target carnivore but also vultures and other scavengers. Responses include prevention (predator-proof livestock enclosures, guarding, electric and beehive fences, early-warning systems, changing crops near forests), compensation or insurance schemes, land-use planning that keeps corridors open, and removal of individual animals. Capture and translocation of problem carnivores often fails because animals return to their home range, cause conflict elsewhere, or die; it is therefore used selectively. The veterinarian's role is to capture conflict animals safely, assess their health and whether they can be released, advise on whether removal to captivity or euthanasia is needed, and keep complete records that may later be used in court. The legal power to authorise removal or killing of a protected animal lies with the wildlife authority, not the veterinarian.
Wildlife forensic science applies laboratory and field methods to legal questions about wildlife: what species is this, which individual or population did it come from, how and when did it die, and who was involved. Crimes include poaching for ivory, horn, tiger parts, pangolin scales and bushmeat, live-animal trafficking, poisoning and cruelty. Veterinarians are often first to examine a carcass or seized item, so their work must stand up in court. The basic rules are the same as in any forensic work. Document the scene before touching anything, with photographs that include a scale and a label, notes, sketches and GPS coordinates. Collect and package each item separately in labelled, sealed containers. Maintain a chain of custody: a continuous written record of who held each item, when, and what was done to it. Keep samples appropriately (frozen, chilled, dried or in preservative, depending on the analysis). Send them to a laboratory that uses validated methods and, ideally, is accredited. Reports separate observation from interpretation, and the expert witness stays within their expertise.
Species identification starts with morphology: skulls, teeth, claws, skins, feathers and horns are compared with reference collections. Hair can be identified by microscopy of the cuticular scale pattern, the medulla pattern and the medullary index, the ratio of medulla width to total hair width. Ivory is identified by Schreger lines, the cross-hatched pattern seen in cross-sections of proboscidean tusks; the angles between these lines help separate modern elephant ivory, which is legal or illegal depending on age and source, from mammoth ivory, with modern elephant ivory showing wider outer angles than mammoth ivory. Rhinoceros horn is compacted keratin without a bony core, unlike the horns of bovids, which have a bony core covered by a keratin sheath. When morphology fails, as with processed products, meat, powders and medicines, DNA analysis is used. Mitochondrial genes such as cytochrome b and cytochrome c oxidase subunit I (the DNA barcoding region) are favoured because each cell holds many copies of mitochondrial DNA, so degraded or tiny samples still give results, and because extensive reference databases exist. Individual identification uses nuclear markers such as microsatellites (short tandem repeats) and single-nucleotide polymorphisms; databases of rhinoceros DNA profiles allow horn seized in trade to be matched to a poached carcass. Population assignment using reference genotypes from across a species' range can identify the region where seized ivory originated, and stable isotope ratios can indicate geographic origin. Radiocarbon dating can show whether ivory came from an animal that died before or after a trade ban.
The forensic necropsy of a wild animal follows the same principles as any necropsy, with extra attention to evidence. Gunshot wounds are investigated by radiography to locate projectiles and fragments before dissection, recovery of projectiles without damaging their marks, and description of entry and exit wounds. Snares leave a circumferential constricting wound on the neck or limb. Electrocution, a common cause of death of large birds on power lines and of elephants near illegal fences, leaves burns at contact points, singed feathers or hair, and sometimes few internal lesions. Poisoning is suspected when several animals of different species die together near a bait, especially scavengers; samples of stomach contents, liver, kidney and the bait are collected for toxicology. Carbamate and organophosphate pesticides, which inhibit cholinesterase, are frequently used to poison carnivores and kill vultures. The veterinary anti-inflammatory drug diclofenac caused the collapse of Gyps vulture populations in South Asia: vultures eating carcasses of cattle treated shortly before death developed kidney failure and visceral gout. Veterinary diclofenac was banned in India, Pakistan and Nepal, and meloxicam is the alternative non-steroidal anti-inflammatory drug shown to be safe for vultures. Lead from ammunition poisons condors, eagles and waterfowl. Time since death is estimated from cooling, rigor mortis, decomposition and insect evidence: the development of blowfly larvae depends on temperature, and forensic entomologists estimate the minimum post-mortem interval from accumulated degree-hours or degree-days. These estimates are wide.
As a student you need the principles that let you work safely around wild animals and pass exams: the digestive types and the classic nutritional diseases (nutritional secondary hyperparathyroidism in cats and reptiles, thiamine deficiency in fish-eaters, vitamin C in primates, iron storage disease), the drug groups used for immobilisation with their antagonists, the four forms of capture myopathy, and the epidemiology of tuberculosis, anthrax, rabies, foot-and-mouth disease, KFD and surra in wildlife. On a zoo or wildlife rotation, your tasks are observation, records, assisting with monitoring during immobilisation and careful necropsy. Learn the CITES appendices and your country's wildlife act early, because they govern every sample you will send.
Five years in, you may be the only veterinarian a forest department or small zoo can call. You plan captures: deciding whether an animal needs to be caught, choosing method and drug combination from a specialist formulary, briefing the team, and having reversal agents and human antagonists ready. You set up and run quarantine and preventive medicine, investigate deaths with full necropsy and sampling, and recognise when a carcass might be anthrax and must not be opened. You respond to human-wildlife conflict captures, make release or euthanasia decisions in rescue centres, and keep records that will stand up if a case goes to court.
With twenty-five years' experience you shape programmes rather than single cases. You write capture and opioid-safety protocols, design surveillance for tuberculosis, rabies or KFD with health and forest departments, and advise governments on fences, buffalo movement or commodity-based trade. You chair studbook and breeding programme decisions, judge when contraception or culling is justified, and set nutrition and welfare standards across institutions. You give expert evidence in wildlife crime trials, assess disease risk for translocations under IUCN guidance, and train the next generation of field veterinarians.
As a researcher with long field experience you work on questions the textbook cannot yet answer: validating diagnostic tests for tuberculosis in elephants, lions or buffalo; modelling transmission at the buffalo-cattle interface; measuring the genetic consequences of small zoo populations; improving immobilisation protocols to reduce hypoxaemia and capture myopathy; and developing forensic markers for traded species. You design studies that respect animal welfare and permit conditions, publish data that managers can use, and translate findings into policy through WOAH, IUCN specialist groups, CITES scientific authorities and national wildlife agencies.
No drug doses are given for any immobilising, reversal, antiviral, anti-tuberculosis or trypanocidal drug: they are species-specific, controlled and dangerous, and must be taken from a current specialist formulary — confirm against the product label and your national formulary. Quarantine periods, release criteria and permit rules vary by institution and country and are described only in general terms. National law is summarised for India, the USA, the EU, the UK and South Africa only, by act name and main purpose; schedules, sections and penalties change, so check the current text. Wildlife diseases outside the curriculum list (for example corridor disease, heartwater, brucellosis in bison and elk, white-nose syndrome, Tasmanian devil facial tumour disease, sarcoptic mange) are mentioned briefly or not at all. Marine mammal, fish and amphibian medicine, avian and reptile surgery, and detailed anaesthetic monitoring equipment are not covered in depth. Reported case fatality of KFD, the carrier duration of FMD in buffalo and the field effectiveness of the KFD vaccine are given only as ranges or qualitative statements because published figures differ.
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