John M. Sykes IV, DVM, DACZM
The primate order includes prosimians (lemurs), monkeys, and apes. This presentation, and the notes that follow, focus on the preventive medicine and intensive care of New World (NW) and Old World (OW) monkeys. New World monkeys include the Cebidae (capuchins, squirrel monkeys), Callitrichidae (marmosets, tamarins), Aotidae (owl monkeys), Pitheciidae (titi, saki monkeys), and Atelidae (howler, spider monkeys) families. Old World monkeys are all in the Cercopithecidae family and include macaques and baboons.1
Zoonoses and Anthropozoonoses
There are numerous infectious diseases that can be transmitted from primates to humans (zoonotic). In addition, there are numerous infectious diseases that can be transmitted from humans to other primates (anthropozoonotic). Important examples of these include tuberculosis (see below) and herpes viruses. Human herpes simplex 1 and 2 (i.e., Herpes simplex) can be lethal to owl monkeys, callitrichids, and saki monkeys.1,3,6,7 After exposure to the natural host with active lesions (e.g., humans with cold sores), these species may develop systemic signs including encephalitis, ulcerative dermatitis, oral ulcers, and necrotic plaques. Similarly, humans that are exposed to Herpes B virus, carried by macaques, may develop systemic illness and death.4,5 The case fatality rate of Herpes B virus in humans who do not receive immediate treatment is 70%.4 For these reasons, it is important to always wear appropriate protective equipment when working with both NW and OW monkeys. In our practice, we wear gloves and masks when in the same air space (room) with all primates, and wear a face shield when working with OW primates. Clothing should be changed after working with primates before eating or going home. If you are working with macaques (all of whom should be assumed to potentially carry Herpes B virus), you should have a bite/scratch protocol for yourself and employees that makes it clear what your policies are in case of an exposure. Immediate cleaning of the wound is most important and follow-up with a physician familiar with the disease should be recommended.2
Routine exams are often recommended in human and domestic animal medicine. Likewise, annual (or semi-annual) exams are often recommended for non-human primates. As these animals must be anesthetized to perform a complete exam, the risk of anesthesia should be weighed against the benefits of the exam. Additionally, many primates live in complex social groups where removal of the animal from the group for an extended period may make it difficult to return the animal to the group without excessive fighting. However, routine exams allow for better management of oral health and identification of problems, such as diabetes or osteoarthritis, in their early stages when they are more easily managed. Procedures during a "wellness" exam should include a complete physical exam, dental exam with prophylaxis (being sure to wear appropriate protective equipment especially when scaling and polishing), baseline CBC and biochemistry panel, and whole body radiographs. Serology for exposure to various viruses is available; however, these panels are generally designed for laboratory animals where the presence of some viruses in the animal can jeopardize its usefulness in a laboratory setting and often do not have clinical significance in smaller collections. It is useful to save serum samples from these in a frozen library for potential future testing (serum banking).
There are no vaccines labeled for use in non-human primates. Generally recommended vaccinations include rabies virus vaccine and tetanus toxoid.1 As with all mammals, monkeys are susceptible to rabies. Not only does vaccination protect the animal from the disease, it can be very helpful to have primates vaccinated for rabies in case they bite a person. Despite the fact that the vaccine is not labeled for primates, some human health departments will make different decisions on the disposition of a monkey that has bitten a person if it has been recently vaccinated for rabies. It is unknown what frequency of vaccination is needed for different species and with different products in monkeys to be protective. Yearly vaccination is likely to be more than frequent enough. There are newer attenuated vaccines that are being investigated experimentally,8 but until these are more widely tested, only killed vaccine products should be used in non-human primates. All monkeys are susceptible to tetanus. Treatment of primates with tetanus is often unsuccessful. These primates can be vaccinated with tetanus toxoid as for humans. The effective frequency is, again, unknown. In our practice, we adjust the volume of the vaccine for both rabies and tetanus based on the size of the animal: 0.1 ml for small monkeys (e.g., tamarins), 0.25 ml for medium-sized monkeys (e.g., guenons, capuchin), and 0.5 ml (tetanus) or 1 ml (rabies) for larger primates (e.g., baboons, apes) and vaccinate opportunistically when animals are handled, but not more frequently than yearly.
Fecal Parasite Monitoring
Protozoal and helminth parasites are commonly found in monkeys and are common causes of diarrhea. Primates should be screened at least yearly for these parasites. Treatment should be based on the perceived parasite load (estimated from the fecal exam) and history of diarrhea or weight loss in the group. Protozoal parasites, particularly flagellates, may be seen routinely in some groups of monkeys without causing diarrhea. They may increase in number (on fecal exam) during episodes of diarrhea, either as a cause of the diarrhea, or as result of increased volume of fecal production. Helminth parasites are generally less common as commensals and should be treated when found. Some parasites in some species (e.g., Trichuris in colobus monkeys) are notoriously difficult to treat. The decision to treat as needed based on fecal exams, routinely, or not at all will depend on the history of the group and the effect parasites have had on its health.
Primates with diseases compatible with tuberculosis infection, or unknown source primates, should always be tuberculin tested with intradermal tuberculin marketed specifically for use in primates (Koch's Old Tuberculin, Synbiotics Corporation, 12200 NW Ambassador Drive, Suite 101, Kansas City, MO 4163). Tuberculin preparations produced for use in people or domestic species should never be used for tuberculin testing of non-human primates because they are not of the correct antigen composition or concentration and will not result in reliable results. Common intradermal test locations are the eyelid, chest, or abdomen. The intradermal tuberculin test may result in a nonspecific tuberculin response, so all suspicious responses should be further evaluated with comparative tuberculin testing using purified protein derivative tuberculins available through the USDA, and infection confirmed by a more extensive medical assessment including chest radiographs and mycobacterial culture of tracheal wash samples. In addition to intradermal tuberculin testing, a blood test is available (PrimaTB STAT-PAK®; Chembio Diagnostic Systems, Inc., 3661 Horseblock Road, Medford, NY 11763) that appears to be more sensitive and specific for tuberculin testing of non-human primates than the intradermal tuberculin test.
Complete necropsies of all mortalities are important components of the preventive medical plan. Necropsy should include both gross and histologic examinations; viral, bacterial, or fungal cultures if an infectious etiology is suspected; identification of parasites observed; as well as any specialized testing (molecular diagnostics, etc.) indicated. Determination of the cause of death is important to understand the individual mortality, but both the significant and incidental necropsy findings are also valuable to detect any underlying nutritional, metabolic, parasitic, or infectious diseases in the group which allows for appropriate steps to be taken to ensure the health of the remaining living collection.
Wound and intensive care
The basics of wound and intensive care in primates are no different than for other species. The challenge is that primates have hands (some with opposable thumbs) and there are no e-collars for monkeys! Additionally, they require anesthesia for bandage changes and wound care. The following information consists of practical approaches to dealing with these problems that have been employed in our practice.
The best place for IV catheterization in most monkeys is the caudal tibial vein located on the caudal aspect of the calf. This vein is generally very superficial, straight, and not easily compressed with leg movements. Using this vein also leaves the animal's hands free for locomotion and feeding. Alternatives may include medial arm veins or superficial pedal veins. The catheter is secured by suturing to the skin and then connected to the t-connector and IV line as for other animals. It can often help to also suture the skin over the IV catheter using mattress sutures and applying skin glue. This additional step helps to keep the catheter secured as the animal moves around. I will often place a piece of tape making "tabs" on the t-connector and secure this to the skin with sutures as well. This helps re-direct the tension away from the IV catheter itself if the line is pulled. Clips on the line can be removed to prevent snags or kinking after wrapping. After securing the catheter and first portion of the IV line, this can be protected by wrapping the leg (from above the stifle to the toes) with roll gauze and bandaging tape (e.g., Vet Wrap). Some practitioners add an adherent bandage (e.g., Elasticon) above the bandage to prevent it from slipping, and/or along the bandage to slow down deconstruction of the wrap by the animal. Allow the IV line to exit the bandage at the toes. For some animals, it may be necessary to cover the bandage with fiberglass casting tape. The IV line should also be protected. Connections should be taped to each other. The IV line should be placed within another covering to slow the animal down if it decides to pick at or chew on the line. The line can also be wrapped with Elasticon. We will often cut Tygon tubing longitudinally and place this over the IV line (the IV tubing will be within the Tygon tubing) and then wrap with Elasticon. For some animals, covering the IV line with rubber tubing/hose may be necessary. We have tried flexible metal conduit, which can work to protect the line, but if the animal is too strong, the conduit can be torn and have very sharp edges which can cut the line or the animal. The tubing covering the IV line can be incorporated in the wrap on the leg as well.
Very sick animals will tolerate IV catheters placed in the manner described above. The precautions, however, will only make it harder for the animal to remove the line or catheter. A dedicated (active or anxious) animal will be able to remove the line. In these animals, it can be helpful to try to keep the animal sedated. The level of sedation will vary depending on its attitude, but ideally keeping the animal alert enough to eat and move around, but not active enough to remove its catheter is the goal. In our practice we have had success using CRI of fentanyl and midazolam.
Case Examples of Creative Approaches to Wound Care
Multimodal Approach to Elbow Wound in a Lesser Slow Loris (Nycticebus pygmaeus)
A 9-year-old female intact loris presented (Day 0) with a 2-cm scab and suppurative discharge over the caudal aspect of the right elbow. The animal was treated with florfenicol (23 mg, SQ) and meloxicam (0.09 mg) and the scab left in place. On Day 2, oral antibiotics were added to the regime (Clavamox 13 mg PO BID). On Day 4, the wound was debrided, the scab removed, and an OpsiteTM bandage placed. By Day 6, there was a healthy bed of granulation tissue, but no wound contracture and the skin edges were starting to lift away from the granulation bed. In an attempt to speed healing, vacuum assisted wound closure (VAC) was attempted. Two pieces of sterile foam were cut to fit the wound and vacuum tubing placed between the layers of foam. This area was covered with TegadermTM (elbow, foam, and vacuum tube), and the whole apparatus wrapped with roll gauze and Vet Wrap. The vacuum was applied. Unfortunately, the animal became tangled in the vacuum line repeatedly overnight and it was cut after only 16 hours of treatment. At that time, the wound edges were more secure than they had been prior to the VAC. The wound was treated with bandage changes every 2–3 days using silver-impregnated dressings. By Day 20, there was minimal change in the appearance of the wound - no re-epithelialization of wound contracture was occurring. The bandage dressing was changed at this time to Duoderm, held in place with roll gauze and Vet Wrap. These bandages were changed every 4–6 days. A change in the wound appearance was noted 2 days later (Day 22) and by Day 38 the wound was completely healed.
Osmotic Pump Placement in a Gelada (Theropithecus gelada)
A 24-year-old male gelada housed in a multi-male bachelor group presented for a bite wound (Day 0) to the right forelimb resulting in local infection and carpal dislocation. This species is particularly difficult to medicate orally; treatment with oral marbofloxacin was successful, but the animal refused other antibiotics. As compliance with marbofloxacin was expected to wane, local antibiotic treatment was initiated. On Day 23, an Alzet® osmotic pump (Model 2ML1), loaded with amikacin (250 mg/ml), was placed SQ in the medial antebrachium and connected to a polyethelene catheter which was tunneled SQ to the site of infection. A cast was placed to protect the sutures and pump. One week later, the pump was replaced by 2 pumps of model 2ML2, the wound and joint flushed, and the cast replaced. The animal was completely non-compliant with marbofloxacin by Day 37. Pumps were replaced and the area flushed twice more at 14-day intervals, after which culture yielded no aerobic bacteria, but an anaerobe was isolated. On Day 73, pumps were removed, the wound left open, and the animal treated with florfenicol (20 mg/kg) via pole syringe or dart every 2 days for 1 month. Antibiotics were discontinued after Day 100, and by Day 116 there was no further discharge or swelling noted. Six months later the animal died of cardiac failure and there was no evidence of infection at that time. This case demonstrates some challenges and solutions to treating animals that may be difficult to treat using conventional methods.
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