THE MERCK VETERINARY MANUAL
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Chinchillas

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Chinchillas are slender-bodied, medium-sized rodents with short forelimbs and long muscular hindlimbs that give the animal a rabbit-like appearance. The head, eyes, and ears are relatively large and the bullae are greatly expanded. Chinchillas have long gestation periods and deliver fully furred young with open eyes.

In the wild, chinchillas live in relatively barren areas of the Andes of Northern Chile at elevations of 3,000–5,000 m. Chinchillas live in burrows or rock crevices but are well adapted for running. They dust bathe, are vegetarian, and are active throughout the year. They are gregarious, living in groups of several hundred. All domestic chinchillas are descendants of 13 individuals brought to the USA in 1927.

Biology

Chinchillas come in a variety of colors. The original chinchilla fur color in the wild was mottled yellow-gray. Through selective breeding, the most common color seen is dark blue grey (dominant fur color gene). Other colors have emerged as mutations of the original standard color. Eye color may be black or pink to red due to coat color genes. Homozygous white and homozygous black combinations are lethal.

The female chinchilla has an estrous cycle of 38 days. Females are seasonally polyestrous, and the breeding season is November to May in the northern hemisphere. The gestation period averages 111 days. Generally, females have 2 litters a year with 1–6 young (average 2) per litter. Young become sexually mature at 8 mo of age. Chinchillas have a long lifespan reported to be up to 20 yr.

Sexing chinchillas can be difficult. In females, a vaginal closure membrane seals the vaginal orifice at all times except estrus and parturition. The vaginal orifice is U-shaped and situated between the anus and the mound-shaped urethral orifice; it is difficult to distinguish when closed, and is indicated by a slightly, raised semicircular area. When its closure membrane covers the vaginal orifice, the urethral orifice can be mistaken as a genital opening. The well-developed clitoris of female chinchillas can be manually extruded through the urethral orifice and mistaken as a penis. The vagina is open during estrus. During these times, the vaginal closure membrane dissolves and then repairs. During estrus there is no vulval swelling. Instead, there is a change in perineal color from a dull, flesh color to a deep red. The color intensity of the perineum increases dramatically at the time of vaginal perforation and remains bright throughout most of the luteal phase of the cycle.

Male chinchillas do not have a true scrotum. The testes are contained within the inguinal canal or abdomen, and there are 2 small moveable sacs (the post-anal sacs) next to the anus, into which the caudal epididymis can drop. The external appearance of the scrotal sacs is similar to the nonpendulous scrotum of pigs and cats. The penis is readily apparent below the anus, from which it is separated by an expanse of bare skin. The penis can be manually extruded 1–2 cm when flaccid. The tip of the erect penis extends to the level of the axilla, a distance of about 11 cm.

As in other rodents, the anogenital distance gives the best initial indication of the animal's gender. In males, the distance is greater. Extrusion of the penis from the urethral orifice confirms the sex of the chinchilla. The penis can be differentiated from the clitoris in 2 ways: 1) the penis is significantly larger than the clitoris; and 2) the extruded penis can be separated and distinguished from the prepuce, while the extruded clitoris tends to evaginate and the clitoral prepuce is not apparent.

Husbandry

Chinchillas are tolerant of cold but sensitive to heat. The ambient temperature range to which chinchillas are adapted is 65–80°F (18–27°C). Exposure to higher ambient temperatures, especially in the presence of high humidity, can result in heatstroke. A good rule thumb is to add the unit values of the temperature (Fahrenheit) and humidity, and consider any value greater than 150 dangerous. For example, 85°F + 65% humidity = 150. Chinchillas develop matted fur if kept in a warm (>80°F [26.7°C]), humid environment.

Chinchillas are easily housed in either wire mesh-bottom or solid-bottom cages, although solid-bottom cages are recommended for pregnant females about to have young. Wire mesh spacing in cages should be narrow, as tibial fractures are a common risk in young chinchillas that catch a leg in a cage bar. Chinchillas are shy animals and need a place to hide when in captivity. In the wild, chinchillas conceal themselves in rock crevices. PVC plumbing pipes, especially elbow, Y, and T sections, make ideal hiding places. The pipes should be 4–5 in. in diameter and can be sanitized by placing in a dishwasher.

Due to their habit of dust bathing, a box containing a mixture of silver sand and Fuller's earth (9:1), 2–4 in. deep should be placed in the cage daily. Dust baths should be provided for ∼30 min/day. If dust baths are left in the cage for long periods, they become soiled with feces. When denied dust bathing in captivity, the fur becomes matted from oily secretions on the back. Dust bathing often causes irritation of the eyes, resulting in conjunctivitis without clinical signs of upper respiratory infection. Excessive dust bathing may result in pulmonary granuloma and epithelial hyperplasia.

A pelleted chinchilla ration is commercially available and suitable; however, chinchillas have also been raised on guinea pig or rabbit rations. Compared with rabbits and other pet rodents, chinchillas have a high requirement for dietary fiber. In addition, their diet should be supplemented with high-quality hay. Urinary calculi, urolithiasis, metastatic renal calcification, and nephritis are reported occasionally. Calculi are typically composed of calcium carbonate. The conditions are associated with feeding a diet high in calcium, such as alfalfa hay.

Like rabbits and guinea pigs, chinchillas produce 2 types of fecal pellets, one nitrogen-rich intended for cecotrophy, and one nitrogen-poor delivered as fecal pellets. Polygamous breeding colonies are common among chinchilla ranchers, and a system of individual female housing has been devised that allows a single male to serve 12 females. A variety of breeding techniques have been used successfully, and mating is facilitated by observing changes in the vaginal closure membrane and performing vaginal cytology. Pregnant females do not make a nest.

Chinchillas possess unusually well developed and elaborate male accessory reproductive glands. The secretion of these glands form a hard plug that remains in the female tract after copulation. In chinchillas, the vesicular gland provides the bulk of the accessory gland secretions, and the fluid hardens or gels when mixed with prostatic secretions. A 2–3 in. long, 1-in. diameter, irregularly shaped firm, waxy plug is often found in the cage after mating and is considered normal.

Physical Examination

The animal's overall appearance and behavior should be noted. Sick chinchillas may show weight loss, hunched posture, abnormal gait, scruffy fur, or labored breathing. They may be lethargic or unresponsive to stimulation. Chinchillas should be handled calmly and gently to minimize stress. Docile, nonpregnant animals can be removed from a cage by grasping and lifting the base of the tail while using the opposite hand to support the body. Routine restraint can be accomplished by wrapping a towel around the body. Small chinchillas may be grasped gently around the thorax, taking care not to restrict breathing. Pregnant females should not be handled unless necessary. Pregnancy is detectable by palpation at 90 days gestation and may be determined by regular weighing. After 6 wk, weight gain in pregnant chinchillas increases rapidly.

A protective reaction in chinchillas known as fur slip results in the release of a large patch of fur, revealing smooth, clean skin underneath. It may also occur with improper handling, fighting, or anything that over-excites chinchillas. The fur can take several months to regrow and frequently results in a different shade. To prevent this phenomenon, chinchillas should be handled gently with minimal stress.

Infectious Diseases

Nearly all significant reports on infectious diseases of chinchillas over the past 50 yr come from colonies of chinchillas raised for fur, and most reports of bacterial disease in colonies are ≥20 yr old. Reviews of the diseases of chinchillas give the impression that these animals are very susceptible to infectious disease. However, in veterinary private practice, infections are infrequent in pet chinchillas.

Opportunistic infections by normal bacterial flora of chinchillas can cause frank disease, localized to a single organ (eg, Streptococcus spp, Pseudomonas spp, Escherichia coli) or as septicemia. Affected animals usually are immunocompromised by age, nutritional status, or husbandry-related stress.

Diagnosis is based on clinical signs, culture, and isolation of the organism. Treatment includes appropriate systemic antibiotics and general supportive therapy. Prognosis is nearly always guarded. Prevention and control in colonies depend on maintenance of good husbandry and sanitation and separation of affected or carrier animals.

Historically, Pseudomonas aeruginosa infections, yersiniosis, and listeriosis occurred frequently among fur-ranched chinchillas in Canada, the USA, and the UK. The estimated number of fur-ranched chinchillas in the USA in 1954 was >100,000. By the mid-1960s, the number was reduced to only a few thousand. Since 1980, reports of yersiniosis and listeriosis in chinchillas come almost exclusively from fur-ranched chinchillas in Hungry, Poland, Slovakia, and Croatia, which supply almost 50% of the 200,000 chinchilla pelts annually produced worldwide.

Opportunistic systemic P aeruginosa infections are described in chinchillas. Affected animals display a variety of clinical signs, including scrotal swelling, conjunctivitis, anorexia, weight loss, and corneal and oral ulcerations. Affected animals can be given chloramphenicol and butorphanol (for analgesia). A vaccine against P aeruginosa has been developed and is used in fur-ranched chinchillas.

The causative agents of yersiniosis, Yersinia pseudotuberculosis and Y enterocolitica occur worldwide in areas of moderate and subtropical climate, and outbreaks in chinchillas are commonly described. Y enterocolitica is the species most frequently isolated from chinchillas. Yersiniosis is an enteric disease that damages epithelium of the ileum, cecum, and colon, resulting in mucosal hemorrhage and ulceration. Lymphoid infiltration results in hypertrophy of Peyer's patches and mesenteric lymph nodes and necrotizing granulomas. Granulomatous lesions spread to the lungs, spleen, and liver, eventually causing death.

A chinchilla-type strain of Y enterocolitica (biovar 3, antigens or serovar 1, 2a, 3) appears to persist enzootically among chinchilla stock worldwide. The pathogenicity of enteric Yersinia appears to depend on a plasmid that is essential for virulence expression. Plasmid-mediated pathogenic functions are survival in serum, resistance to phagocytosis, cell adhesion, and cytotoxicity. However, bacterial endocytosis in intestinal epithelial cells seems not to be encoded by a plasmid.

Listeriosis in chinchillas was first reported in 1949. It is common in fur-ranched chinchillas but not in laboratory or pet chinchillas. Although the original report suggested that chinchillas are highly susceptible to infection with Listeria monocytogenes, this has not been proved. Case reports of listeriosis in chinchillas describe fur-ranched animals in high northern latitudes (eg, Canada, Washington State, the UK, Croatia, Hungry, and Slovakia). Most reports of listeriosis arise from the ingestion of contaminated food; the disease is common in animals fed on silage. Unlike most foodborne pathogens that primarily cause GI disease, L monocytogenes causes several easily recognized invasive syndromes, such as encephalitis, abortion, and septicemia. In chinchillas, listeriosis is a cecal disease with bloodborne dissemination. The main target organ is the liver, where the bacteria multiply inside hepatocytes. Early recruitment of polymorphonuclear cells lead to lysis of hepatocytes, bacterial release, septicemia, and in surviving hosts, the development of lung, brain, spleen, lymph node, and liver abscesses. The invasion of peripheral nerve cells and rapid entry into the brain, which cause the classic histopathologic lesion of monocytic perivascular cuffing, is believed to be a unique characteristic of its virulence.

Other recorded infections in chinchillas include clostridial enterotoxemia, salmonellosis, and Klebsiella infection. Affected animals display nonspecific septicemic signs such as loss of appetite, respiratory distress, and diarrhea and die within a few days after the onset of clinical signs. In the 1940s and 1950s, veterinarians described Salmonella epizootics characterized by gastroenteritis and abortion in fur-ranched chinchillas in the USA. Recent case reports describe Salmonella infection in companion chinchillas.

No species-specific viral diseases have been described in chinchillas. Chinchillas are susceptible to human herpesvirus 1 and may play a role as a temporary reservoir for human infections. Two case reports describe spontaneous, herpes-like viral infection in chinchillas. Affected animals displayed conjunctivitis and subsequently showed neurologic signs of seizures, disorientation, recumbency, and apathy. Nonsuppurative meningitis and polioencephalitis with neuronal necrosis and intranuclear inclusion bodies were found on histologic examination at necropsy. In addition, eyes displayed ulcerative keratitis, uveitis, retinitis and retinal degeneration, and optic neuritis. The clinical signs, distribution of the lesions, and viral antigen suggested a primary ocular infection with subsequent spread to the CNS.

Toxoplasmosis was commonly found in fur-ranched chinchillas but is now rarely seen. Necropsy lesions include hemorrhagic lungs, enlarged spleens, and enlarged mesenteric lymph nodes. Chinchillas may also develop focal necrotic meningoencephalitis due to Toxoplasma gondii.

In the past, group-housed chinchillas such as in fur ranches and research colonies often had a high prevalence of Giardia infection. However, normal chinchillas harbor Giardia in moderate numbers, and two-thirds of all chinchillas are positive on fecal diagnostic tests. Stress and poor husbandry are believed to cause an increase in Giardia and predispose animals to opportunistic gastroenteric bacterial infections, resulting in severe diarrhea and death.

Other protozoan infections include Eimeria chinchilla, hepatic sarcocystosis, and gastroenteritis associated with Cryptosporidium.

Outbreaks of cerebral nematodiasis caused by the raccoon ascarid Baylisascaris procyonis are seen in chinchillas housed outside in high northern American climates. An orbital cyst due to Taenia coenurus has been reported in a pet chinchilla with exophthalmos.

There are two reports of Histoplasma capsulatum infection in chinchillas. Necropsy lesions revealed multiple foci of pulmonary hemorrhage, consolidation, and bronchopneumonia with the organism in numerous giant cells and multifocal pyogranulomatous splenitis and hepatitis with H capsulatum in giant cells. H capsulatum was cultured from timothy hay used for food.

Dermatophytosis is uncommon in chinchillas. Trichophyton mentagrophytes is the dermatophyte most commonly isolated, although Microsporum canis and M gypseum have been incriminated in spontaneously occurring outbreaks. Infected chinchillas have small, scaly patches of alopecia on the nose, behind the ears, or on the forefeet. Lesions may appear on any part of the body, and in advanced cases a large circumscribed area of inflammation with scab formation occurs. Fungal cultures of fur-ranched chinchillas show a 5% incidence of T mentagrophytes in animals with normal skin and a 30% incidence in animals with fur damage. Diagnosis is based on lesions and isolation of the causative agent using dermatophyte test medium. Ultraviolet light (Wood's lamp) examination is rarely helpful, because most cases are caused by T mentagrophytes, which does not fluoresce under ultraviolet light. Treatment consists of 5–6 wk of oral itraconazole. Dermatophytosis is contagious to humans and other animals.

Metabolic and Nutritional Disorders

In the early 1960s, the Chinchilla Fur Breeders Association of England showed that approximately half of all deaths in adult chinchillas were due to disorders of the digestive tract; malocclusion accounted for ¼ of those deaths. Husbandry-related disorders of the digestive tract remain one of the most frequent problems seen. Lethargy and anorexia are typical clinical signs.

Cheek tooth crown and root abnormalities are common in chinchillas. Complications of malocclusion (“slobbers”) include periodontitis, alveolar periostitis, and alveolar abscessation of maxillary and mandibular cheek teeth. Abnormalities may be observed by the time animals are 6 mo old. Clinically, malocclusion leads to unthriftiness, rough fur, anorexia, and weight loss. Excess salivation frequently results in inflammation and alopecia of the skin on the chin and ventral neck. Overgrown teeth or roots can penetrate the mandible or hard palate, demonstrated by mucopurulent draining tracts or ocular and nasal discharge. Mastication becomes increasingly difficult, and severe malnutrition may lead to hypoglycemia and ultimately seizures, paralysis, coma, and death. The oral cavity should be thoroughly examined by otoscope or small speculum; usually general anesthesia is necessary. Premolar and molar teeth may be loose, broken, or sharply pointed. Sometimes feed or foreign bodies are impacted between the teeth and the underlying oral mucosa. Radiography is a helpful tool for checking tooth position and overgrowth of the roots. CT scans can be used for early diagnosis of malocclusion. Because chinchilla teeth grow constantly, appropriate materials (eg, pumice stones, chew blocks) to gnaw are required. Teeth and body weight should be frequently monitored to avoid further problems. Individual chinchillas with malocclusion should not be bred.

Chinchilla anatomy precludes the ability to vomit. Choking may be observed when the entrance to the trachea is occluded by a large piece of food or bedding or in postpartum females that eat their placentas. Aspiration of tiny particles from the foreign body can irritate the lower respiratory tract and precipitate a suffocating, edematous response leading to drooling, retching, coughing, and dyspnea as the chinchilla attempts to dislodge the foreign body. If untreated, choking may lead to asphyxiation and death. Megaesophagus, which leads to regurgitation and aspiration pneumonia, is described. Affected animals show recurring pneumonia despite treatment. Contrast radiographs are used for diagnosis.

Gastric ulcers are common in young chinchillas and are frequently caused by feeding coarse, fibrous roughage or moldy feeds. Clinically affected animals may be anorectic or asymptomatic. Lesions may only be noted at necropsy, with gastric mucosal ulcers and erosions covered by thick, black fluid. Prevention includes decreasing dietary roughage and feeding a commercial pelleted diet.

Bloat can result from sudden dietary changes, especially overeating. It has been reported in lactating females 2–3 wk postpartum and may be related to hypocalcemia. Gas production from the bacterial flora in static bowel rapidly accumulates within 2–4 hr. Affected animals are lethargic, dyspneic, and have a painful, distended abdomen. They may roll or stretch while attempting to relieve their discomfort. Treatment may require passage of a stomach tube or paracentesis to relieve gas build-up. Lactating females may respond favorably to calcium gluconate administered IV slowly to effect.

More common than diarrhea, constipation typically results from insufficient dietary fiber and roughage. Dehydration, environmental stress, intestinal obstruction, obesity, lack of exercise, trichobezoars, and uterine compression in gravid females may also result in constipation. Chinchillas may strain to defecate and have decreased fecal output. Fecal pellets are thin, short, hard, malodorous, and sometimes stained with blood. Chronic cases may lead to rectal prolapse, intestinal torsion, cecal impaction, or colonic flexure. To provide relief, dietary fiber should be increased by providing alfalfa cubes, adding mineral oil to the feed, and administering soapy, warm-water enemas. Persistent intestinal blockage may be due to intestinal adhesions, tumors, abscesses, impactions, or foreign bodies. These may be palpated abdominally or identified on radiographs using contrast media. Enterotomy and intestinal anastomosis may be required in such cases.

Pathologists often see fatty liver histopathology without clinical signs or other histopathology in routine necropsies. This is most likely due to prolonged anorexia before death.

A few cases of diabetes mellitus have been described in overweight chinchillas; they appear to be Type II diabetes. Clinical signs may include poor appetite, lethargy, and weight loss. Diagnosis is based on a history of polydipsia and polyuria, hyperglycemia (200 mg/dL), and glucosuria. Because the insulin of chinchillas and other hystricognath rodents (eg, guinea pigs, degus, tuco-tucos) has a low biologic potency compared to pig insulin, hypoglycemia is a risk when treating diabetes with recombinant human insulin or porcine insulin. Treatment is achieved by reducing obesity and feeding a diet that is high in protein, low in fat, and high in complex carbohydrates.

Traumatic Injuries

Some chinchillas chew each other's fur resulting in a moth-eaten coat. Clinically, hair loss is observed along the shoulders, flanks, sides, and paws. The affected areas appear darker due to the exposed underfur. Mothers often transmit the behavior to offspring. The higher incidence of fur chewing in commercial herds may be evidence of maladapted displacement behavior. Some clinicians claim affected animals suffer from malnutrition and chew their fur for dietary requirements. Multiple food factors are probably involved in this type of malnutrition and the exact etiology requires further study. The predator avoidance mechanism known as fur slip, in which a chinchilla releases a large patch of fur, thus enabling it to escape, should not be confused with fur-chewing.

During breeding, bite wounds that abscess may occur in group-housed animals. Culture of the abscesses often yields Staphylococcus spp. Female chinchillas are larger than males and more aggressive. They are highly selective in their choice of mates and will keep nonpreferred males at bay by urination, kicking, and biting. Often bite wounds result in the loss of pieces of ears and toes. A young male housed in the same cage with older females may be killed.

The chinchilla's large, delicate pinnae are easily traumatized, most often from bite wounds. Therapy includes cleaning the traumatized area with antiseptic solution and antibiotic ointment. Suturing large ear lacerations is usually not effective and not recommended. If severe damage is present, ear tissue may require significant debridement or partial surgical removal. Trauma can result in rapid hematoma development, with blood and serum filling the space between skin and cartilage. Hematomas should be lanced and contents gently removed to avoid further damage to the ear. The skin over the hematoma must remain in contact with underlying cartilage and should be immobilized by sutures if necessary.

Traumatic fractures of the tibia are commonly seen and associated with the animal catching its hindlimb in a cage bar. The tibia is a straight bone longer than the femur, with little soft tissue covering; the fibula is virtually nonexistent. Tibial fractures are either transverse or short spiral and generally have multiple fragments. Treatment options are limited due to the small size and cortical thinness of the chinchilla tibia. An intramedullary pin is the treatment of choice for an oblique fracture; however, the pin may migrate outside of the bone causing problems with healing. Consequently, an external fixateur is generally used with an intramedullary pin. For transverse or spiral fractures, intramedullary pins do not stabilize against rotational forces. Fracture stabilization using human phalangeal plates and external coaptation has been reported at a few veterinary school surgery centers. Hindlimb amputation should be considered a salvaging procedure if fracture stabilization is not feasible.

Reproductive Disorders

In chinchillas, the fine structure of the interhemal membrane of the placental labyrinth is hemomonochorial, consisting of a single layer of syncytial trophoblasts. Female chinchillas may have an unusual puerperal disorder of trophoblastic emboli, resulting in pulmonary embolism.

Chinchillas usually give birth early in the morning and only rarely after midnight. Dystocia is usually associated with presentation of a single, oversized fetus or malpresentation of one or more kits. Uterine inertia has also been reported as a cause of dystocia. Chinchillas respond well to cesarean section.

Male chinchillas that groom excessively, urinate frequently or strain to urinate, and repeatedly clean their penis may have a fur ring. This is a ring of hair around the penis and under the prepuce that eventually stops the penis from going back to the prepuce. In severe cases, an engorged penis is seen protruding 4–5 cm from the prepuce, resulting in paraphimosis. The condition is painful and may cause urethral constriction and acute urinary retention. Chronic paraphimosis may culminate in infection and severe damage to the penis, affecting the animal's breeding ability. Getting fur from a female during copulation is the most common cause. However, the condition is also seen in group-housed and single-housed males not exposed to females. Males should be examined for fur rings at least 4 times a year; active stud males should be examined every few days. Fur rings can be cut or gently rolled off the penis after applying a sterile lubricant. Occasionally, sedation or anesthesia may be required. In some male chinchillas, the penis hangs out of the prepuce all the time and is not engorged. The cause of this condition is not fur ring, but overexcitement brought on by a separation of the male from its mate or overexhaustion due to too many females in the same cage.

Neoplasia

Despite a lifespan reported up to 20 years, references to neoplasia in chinchillas are rare. Postmortem examinations of 1,005 fur-ranched chinchillas before 1949 and another 1,000 fur-ranched chinchillas between 1949–1952 ranging in age from <6 mo to 11 yr did not list neoplasia as a cause of death. Between 1994 and 2003, 325 chinchillas were presented for clinical investigation at a major university veterinary hospital. Tumors were diagnosed in only 3 animals (1%). Single reports of tumors in chinchillas include neuroblastoma, carcinoma, lipoma, hemangioma, malignant lymphoma, hepatic carcinoma, and lumbar osteosarcoma.

Miscellaneous Disorders

Aged chinchillas may develop posterior cortical cataracts and asteroid hyalosis.

Certain types of cardiac disease such as dilated cardiomyopathy, congenital septal defects, and valvular disease have been reported in chinchillas. Murmurs of varying intensity have been described in chinchillas, and often are found on routine examination of young animals. There are no reports on the prevalence of various heart diseases in this species, and the relationship between the occurrence of heart murmurs and underlying cardiovascular pathology has not been investigated.

Last full review/revision July 2011 by Thomas M. Donnelly, BVSc, DACLAM

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