Unique Anatomy and Physiology

Chinchillas are native to the semiarid mountainous areas of South America, particularly the countries of Peru, Argentina, Bolivia, and Chile.^1,2 Most of the chinchillas kept in the United States are descendants of a small group of animals imported into California in the 1920s.¹ Because of overhunting for its beautiful coat, the chinchilla is believed to be nearly extinct in the wild. Wild-type chinchillas have a silver-gray coat with black ticking. Today, there are a number of different coat color variations that have been developed as a result of the fur, show, and pet chinchilla trades. Because the captive chinchillas found in the United States originated from a very small number of animals, a genetic component is suspected in many of the commonly seen disease processes.

Adult chinchillas usually weigh between 400 and 800 g, females being slightly larger than males. Relative to other rodent species, the life span of the chinchilla is long, sometimes nearing 20 years of age.¹ Chinchillas are naturally nocturnal, but they can adapt to a more diurnal lifestyle.

Chinchillas are unique-looking animals with a short body, large head, delicate limbs, large hairless ears, and a bushy tail. Chinchillas have the longest gestation period of any commonly kept rodent species (110 days). Young, of which there are one to six (average two), are precocial. Chinchillas become sexually mature at 7 to 9 months of age.

Creating an Appropriate Habitat

ACCESSORIES

Shelter Box

Chinchillas should be provided shelter areas within their enclosure. Non-treated wooden boxes may be used, but may eventually need to be replaced if the animal chews on the box.

Dust Baths

To maintain proper coat health, chinchillas must be provided with a dust bath 2 to 3 times per week for 10 to 20 minutes (Figure 18-1). The dust used for these animals is a volcanic ash, and commercial brands are readily available. It is important to remove the dust bath from the chinchilla’s enclosure after the bathing period. If the dust bath is not removed, chinchillas tend to bathe excessively, and the prolonged exposure to dust can cause ocular and respiratory irritation.

Figure 18-1 A chinchilla enjoying a dust bath. Dust baths are essential for chinchillas’ skin maintenance and coat health.

(Courtesy Michelle G. Hawkins, VMD, DABVP [Avian].)

Diet

Chinchillas are native to an area of the world that contains sparse vegetation, primarily consisting of grasses. The recommended nutritional composition of a chinchilla diet is 16% to 20% protein, 2% to 5% fat, and 15% to 35% bulk fiber.³ An appropriate chinchilla diet should be comprised of a high-quality hay (e.g., timothy, oat, or orchard grass), chinchilla pellets, and an assortment of dark leafy vegetables (e.g., romaine lettuce, mustard greens, collard greens). Some veterinarians recommend rabbit or guinea pig pellets for chinchillas; however, these pellets are shorter in length than those recommended for chinchillas and are more difficult for these animals to hold. Fruits, grains, and raisins may also be provided as treats on an occasional basis, but they should comprise less than 5% of the animal’s diet. Chinchillas should be provided ad lib access to water in a hanging water bottle.

Quarantine

Newly acquired animals should be quarantined from established animals for a minimum of 30 days. This recommendation should be considered a minimal quarantine period, as certain diseases could remain latent for more than 30 days. All quarantined animals should be thoroughly examined and screened using baseline diagnostics (e.g., complete blood count, plasma biochemistries, and a fecal exam). During the quarantine period, the animal’s appetite, demeanor, and fecal output should be monitored closely.

Routine Exams

Chinchillas are not routinely vaccinated for infectious diseases in the United States. However, owners should be encouraged to have an annual examination performed on their pets, including a thorough oral examination and blood work. Being a prey species, chinchillas are adept at hiding illness, and a routine evaluation by a qualified veterinarian may help in detecting abnormalities early.

Many health problems of chinchillas are directly related to improper husbandry. During a routine veterinary visit for chinchilla patients, owners should be asked to provide a detailed description of the animal’s environment, including cage size and type, substrate, frequency of cleaning, ambient temperature, and exercise time. Information pertaining to the animal’s diet, feeding frequency, and bowel movements is also important to obtain.

Disinfection and Sanitation

Chinchilla enclosures, food bowls, water bottles, and cage accessories should be sanitized using a standard disinfection protocol. Sodium hypochlorite is the preferred disinfectant (dilute 5.25% solution 1 : 32). It is important to thoroughly rinse the enclosure and accessories before replacing them in the cage. The cage should be allowed to dry in a well-ventilated area.

Manual Restraint

Chinchillas are relatively docile and usually do not require aggressive restraint; however, they are capable of quick bursts of activity. A chinchilla that is dropped may injure itself, so appropriate restraint is necessary when examining or transporting these animals. In general, the more a chinchilla is restrained, the more it tends to struggle, so a “less is more” approach should be used. A chinchilla should be restrained by supporting the weight of the body with one hand under the thorax and grasping the base of the tail with the other hand (Figure 18-2). Chinchillas should never be scruffed or handled roughly. Rough handling can result in “fur slip” or the loss of a patch of fur at the site where the animal was grasped. This lost fur can take several months to grow back (see Dermatologic Conditions).

Figure 18-2 Restraining a chinchilla for transport. The handler has control of both the pelvic and thoracic limbs to prevent the patient from jumping and injuring itself.

Chemical Restraint

Chinchillas that are fractious or must be anesthetized can be given either parenteral or inhalant anesthetics. We prefer inhalants for these animals, although the parenterals can be used as preanesthetics to limit the concentration of inhalant required for a procedure. Chinchillas can be induced via a face mask with isoflurane or sevoflurane (Abbott Laboratories, North Chicago, IL). In general, an induction rate of 3% to 5% isoflurane (per 1 L oxygen) or 5% to 7% sevoflurane (per 1 L oxygen) is required. Chinchillas, like other rodents, are difficult to intubate because of their long, narrow oral cavity. We prefer to intubate these animals using an endoscope. A rigid 2.7-mm endoscope can be used to visualize the airway and direct the endotracheal tube into place. The endotracheal tube size required for a chinchilla can vary, although 2.0 to 4.0 outside diameter tubes are generally acceptable. Once the chinchilla is intubated, the endotracheal tube should be secured and the animal maintained on the inhalant. In general, chinchillas can be maintained at 1.5% to 3.0% isoflurane (per 0.5-1 L oxygen) or 3.0% to 5.0% sevoflurane (per 1 L oxygen). Many of the parenteral anesthetics used for domestic pets can also be used for chinchillas. (For a complete list of parenteral agents please refer to Anesthesia; see also Table 18-6).

TABLE 18-6 Common Analgesic and Anesthetic Agents Used in Chinchilla Medicine

Common Abnormalities Found on the Physical Examination

As with any species, it is important to always perform a thorough physical examination to minimize the likelihood of misclassifying the disease state of a patient. Therefore, veterinarians working with an animal should avoid the trap of only examining the system(s) that a client mentions during the history and instead examine the entire animal. There are a number of potential abnormalities that may arise during a physical examination. In many cases, an animal may present with multiple, unrelated problems. The primary problems found on a chinchilla examination include teeth malocclusion, otitis externa, heat stroke, upper and lower respiratory disease (e.g., pneumonia), penile fur ring, pododermatitis, and fur slip.

Hematology

Venipuncture in chinchillas can be difficult for the veterinarian and stressful for the patient. Many of the peripheral vessels that are accessible in dogs and cats are very small in chinchillas and do not allow for the collection of adequate volumes of blood for routine testing. Access to larger vessels, such as the jugular vein, requires somewhat aggressive restraint, which may not be appropriate in a sick or stressed animal. It is often preferable to perform venipuncture under sedation or anesthesia in these patients; however, veterinarians must carefully consider the benefits of obtaining diagnostic samples against the risk of anesthesia for each individual patient.

When a large blood sample is required (e.g., for complete blood count and plasma biochemistry panel), the jugular, cranial vena cava, or femoral vein can be used. These sites are best accessed under anesthesia, as restraint is stressful and excessive struggling by the patient may cause laceration of these large vessels. A 25-gauge needle fastened to a 1-ml or 3-ml syringe can be used to collect the sample. If small quantities of blood are required (e.g., blood glucose or PCV/TS [packed cell volume and total solids determination]), blood can be collected from the cephalic or lateral saphenous veins. When sampling these smaller veins, a 25- or 27-gauge needle fastened to a 1-ml syringe can be used. Insulin syringes may also be used. Using a smaller syringe will help minimize the likelihood of collapsing the blood vessel. When placing the sample into a blood storage tube, it is important to remove the needle before discharging the sample to prevent hemolysis.

Hematologic testing is an important diagnostic tool in chinchilla medicine. Because these prey species can mask their illness, veterinarians must rely on hematologic and other diagnostic tests to fully assess their patients. Box 18-1 presents reference intervals for chinchillas.

The most common leukocyte in the chinchilla is the lymphocyte. The second most common circulating granulocyte is the heterophil. Heterophils lack myeloperoxidase, the enzyme responsible for liquefying purulent material. Therefore, chinchilla abscesses tend to be very thick and caseous. The remaining leukocyte types—monocytes, eosinophils, and basophils—are normally present in very low numbers. During an inflammatory response in a chinchilla, the early stages are often characterized by a shift in the differential (e.g., increased heterophils, decreased lymphocytes) rather than an increase in absolute leukocyte count, so evaluation of the entire leukogram is essential. The platelet count can also serve as an important marker of inflammation in chinchillas. Large increases in the platelet count (>1,000,000/ml) may be seen without an increase in the total white blood cell count, indicating an inflammatory process.

Plasma biochemistries can provide important information regarding the physiologic status of a chinchilla. As with any patient, it is important to interpret the results of a chemistry panel in conjunction with the anamnesis, physical exam findings, and the results of other diagnostic tests. Reference intervals for various chinchilla biochemical parameters can be found in Box 18-2.

Urinalysis

A urinalysis is an important diagnostic test in chinchilla medicine and should be considered in any case with signs of upper or lower urinary tract disease. Urine samples may be obtained by free catch, floor catch, or cystocentesis. If urine is to be cultured, it should be collected by cystocentesis. The cystocentesis procedure for chinchillas is similar to that described for cats. The animal should be placed in dorsal recumbency for the procedure. Sedation may or may not be necessary. A 25-gauge needle fastened to a 3-ml syringe can be used to collect the sample. The ventral abdomen should be disinfected before needle insertion using standard techniques. Ultrasound can also be used to guide the needle into the bladder.

The urine of chinchillas is typically yellow to amber in color, although the color may be darker and more orange in color depending on the diet. Pigments (e.g., porphyrins) in the urine can sometimes be mistaken for hematuria and must be ruled out by the absence or presence of blood cells on a direct smear. Because chinchillas are herbivores, the pH of chinchilla urine should be alkaline (pH 8.0-9.0).

Diagnostic Imaging

Whole body radiographs can provide a significant amount of information regarding the status of a chinchilla patient. A minimum of two radiographic views should be taken. Our preferences are for lateral and ventrodorsal (or dorsoventral) views (Figures 18-4 and 18-5). Care should be taken to extend the limbs when positioning the patient, to minimize rotation and the superimposition of the limbs over the abdomen or thorax. Chinchillas typically resent aggressive restraint, so sedation or anesthesia is helpful in obtaining diagnostic radiographs as well as in reducing the stress on the patient. Table 18-1 is intended as a general guideline for the techniques used for chinchilla radiographic studies.

Figure 18-4 A right lateral radiograph of a chinchilla. Note the small size of the thorax and the large size of the abdominal cavity.

(Courtesy University of California–Davis.)

Figure 18-5 A ventrodorsal radiographic view of a chinchilla. Again, note the small size of the thorax and large size of the abdomen in this species.

(Courtesy University of California–Davis.)

TABLE 18-1 Guidelines for Radiographic Techniques for Selected Radiographic Studies in Chinchillas

Dental malocclusion is a common problem in chinchillas. Skull radiographs can be used to fully assess the degree of malocclusion and secondary bony involvement (Figure 18-6). When taking skull radiographs, it may be necessary to take 3 to 4 different views. In addition to the standard lateral and dorsoventral (or ventrodorsal) views, right and lateral oblique views can be used to more specifically localize lesions. Magnified views of the skull can be obtained by placing the patient on an elevated platform under the x-ray beam without changing the distance between the x-ray cassette and the beam.

Figure 18-6 Right lateral radiographic view of a chinchilla skull. Note the severe elongation of the crowns and apicies of the premolars and molars as well as the abnormal occlusal angle of the incisors. The large tympanic bullae of the chinchilla are also easily seen (arrow).

(Courtesy University of California–Davis.)

Ultrasound is another imaging modality that can be used to diagnose various disease processes in chinchillas. As with radiographs, sedation or anesthesia may be required to reduce patient stress, minimize movement, and improve the overall quality of images that are acquired. The approach to the chinchilla ultrasound exam is similar to that described for domestic species, although there are some exceptions. Chinchillas have a large cecum. If the cecum contains a large quantity of gas, it may limit the value of an abdominal ultrasound exam. Ultrasound can also be used to assist with the collection of various aspirates (e.g., cystocentesis) or biopsies (e.g., liver biopsy).

Advanced imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), can also be used to assist in the diagnosis of disease in chinchillas. CT imaging is particularly useful in diagnosing dental problems, such as apical abscesses, osteomyelitis, and minor malocclusions not readily seen on oral examination or radiographs (Figure 18-7). The primary limitations associated with these imaging modalities include limited availability to the general practitioner, the expense associated with the collection and interpretation of the image, and reduced image quality in comparison with that of larger patients. MRI has the added limitation of requiring a significant amount of time (often >45 min) to collect the image.

Figure 18-7 Computed tomography image of a chinchilla skull in saggital section. There is mild malocclusion of the cheek teeth visible (arrow).

(Courtesy University of California–Davis.)

Regardless of the present limitations associated with these advanced imaging modalities, veterinarians should be made aware that these techniques are available and that reference material exists that depicts normal anatomy for comparison.⁵ As chinchilla owners continue to demand high-quality care for their pets, these imaging techniques will likely become more commonplace in exotic small mammal practice.

Microbiology

Chinchillas are susceptible to many of the same pathogens that affect domestic species. The primary pathogens isolated from chinchillas include Gram-negative bacilli (e.g., Bordetella spp., E. coli, Klebsiella spp., Salmonella spp., Pseudomonas spp.) and Gram-positive cocci (Staphylococcus aureus, Streptococcus spp.). Many of these organisms are opportunists and can be routinely isolated from healthy animals. Samples being submitted for bacterial culture should be collected using sterile swabs and submitted to a diagnostic laboratory capable of isolating and characterizing a range of organisms. The majority of the samples being submitted from chinchillas are for aerobic isolates and require no special attention regarding collection or submission. However, if an anaerobic infection is suspected, it is important to contact the local laboratory to obtain the appropriate materials to collect and submit the samples.

A positive bacterial culture does not necessarily confirm that an organism is responsible for a disease, so it is important to always use the data obtained from the culture, in combination with information obtained from the clinical examination (e.g., elevated body temperature) and additional diagnostic tests (e.g., elevated complete blood count, biopsy, etc.), to confirm a disease. This is especially important in chinchillas, as they are susceptible to antibiotic-induced enteritis and should only be treated with (appropriate) antibiotics when a bacterial infection is highly suspected.

Fungal infections are not common in chinchillas. However, if a fungal infection is suspected (e.g., no response to antibiotics, biopsy results), then standard techniques may be used to isolate the fungus.

Parasitology

Chinchillas may become infested with a variety of endoparasites and ectoparasites. Fortunately, because these animals are bred in captivity, parasites are uncommon. Protozoa (e.g., coccidian) are the most commonly encountered parasites in captive chinchillas. Fecal flotation and/or direct fecal smears mixed with saline can be used to diagnose these infections. These same techniques can be used to diagnose other endoparasites, such as nematodes. Diagnosing ectoparasites in these animals can be done using the same techniques used in domestic animals. Fleas may be identified by closely inspecting the animal hair coat and combing through the fur. Most mites can be identified by using tape preparations or skin scrapes. All of these samples, once collected, should be evaluated under light microscopy.