CHINCHILLAS

CHAPTER 18 CHINCHILLAS




COMMON SPECIES KEPT IN CAPTIVITY


There are two species of chinchilla that are kept in captivity: Chinchilla laniger (or lanigera) and C. brevicaudata.1,2 C. laniger is the species commonly kept in captivity in the United States. Originally imported into the United States to provide a commercial fur, these long-lived rodents make excellent pets.



BIOLOGY



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.



HUSBANDRY



Creating an Appropriate Habitat








NUTRITION



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.



PREVENTIVE MEDICINE






RESTRAINT





PERFORMING A PHYSICAL EXAMINATION


A physical examination should include both a hands-off and a hands-on review of the animal. For the hands-off exam, particular attention should be paid to the respiratory rate and character, attitude, and posture. Animals with respiratory compromise or neurologic disease should be handled carefully during the hands-on examination. It is important to always measure the animal’s body temperature before performing the complete physical exam. A chinchilla’s body temperature is generally lower (96° to 99° F [35.5° to 37.2° C]) than that found in other domestic mammals. Because chinchillas have such a dense hair coat, their body temperature can increase dramatically over the course of a physical examination, and this should be taken into consideration. Otherwise, the physical exam should be approached in a thorough, systematic manner, as in any mammalian patient. Thoracic auscultation and abdominal palpation can be performed as in other patients. Auscultation of gut sounds is also an important part of the chinchilla physical exam. A healthy chinchilla should have 1 to 2 borborygmi per minute.


A complete oral examination is another important facet of the chinchilla physical exam. This should be reserved for the end of the examination, as it can be rather stressful for the patient. As is the case for most rodent species, the cranial surface of the incisors is covered with a layer of yellow to orange enamel (Figure 18-3). The oral cavity of the chinchilla has a small opening and is very narrow and long. In most cases, an otoscope with cone or a human nasal speculum is required to fully examine the molars and caudal aspect of the oral cavity. In most cases, the oral exam can be performed on an alert animal; however, anesthesia may be required when the animal is difficult to restrain, appears to be experiencing pain, or requires a more detailed oral exam.





DIAGNOSTIC TESTING



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.





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.




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



















Anatomic location mA kVp
Whole body 5.0 44
Extremities 6.0 54-56
Skull 6.0 48-52

kVp, kilovolt peak; mA, milliampere.


Data from Silverman S, Tell LA: Radiology equipment and positioning techniques. In Silverman S, Tell LA, editors: Radiology of Rodents, Rabbits, and Ferrets: An Atlas of Normal Anatomy and Positioning, St Louis, 2005, WB Saunders.


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.



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.



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.


Oct 1, 2016 | Posted by in EXOTIC, WILD, ZOO | Comments Off on CHINCHILLAS
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