Pet Rodents

Chapter 177 Pet Rodents

Many small rodents are commonly kept for companionship and enjoyment. This chapter provides information needed to diagnose and treat the most frequently encountered problems of mice, rats, gerbils, hamsters, guinea pigs, and chinchillas.


Caging and Sanitation



A systematic history and physical examination are mandatory. Many disease syndromes are caused by poor husbandry. Pets that have been kept isolated from other rodents or acquired from a private breeder are less likely to harbor infectious disease than animals obtained from a pet store, laboratory, or wholesaler. See Table 177-3 for normal physiologic data.

Obtain the following information:

Dates of unusual activity: breeding, parturition (Table 177-4), cannibalism, abnormal urination or defecation

Examination of Patient and Environment


Restraint of pet rodents is easy with experience. Pets that have been handled frequently and gently by the owners require only minimal restraint. Gentle pressure directs the animal as needed. Grasp less cooperative patients (except chinchillas and guinea pigs) by the scruff over the back of the neck with thumb and forefinger (Fig. 177-1). Take care to pinch enough skin to prevent the animal from turning around, yet leave enough slack for respiration. On smaller specimens, hold the base of the tail, if present, between the fourth and fifth fingers to provide additional restraint.

Hold docile guinea pigs with the palm of one hand supporting the chest while the other hand supports the hind quarters (Fig. 177-2). Place the thumb and forefinger of the first hand in the axillas for additional control.

Physical Examination

Once the animal is restrained properly, examine the head. Assess the cranial nerves. Check the nose for presence and character of discharge. Examine the mouth for ptyalism, swelling, overgrown incisors, or discharges. To inspect the oral cavity, place an avian speculum across the mouth just caudal to the incisors. Use a light source and a pair of hemostats as retractors to improve access. Alternatively, use an otoscope with a pediatric head to examine the premolars and molars of guinea pigs and chinchillas for overgrowth. Examine the cheek pouches of hamsters for swelling, impaction, or discharge. An ophthalmic examination, including a fundic examination, is important.


Blood Samples

To bleed the tail, warm the tail with water or compresses to dilate the tail vessels. In large rats, perform venipuncture with a needle and obtain blood in the usual fashion. In smaller animals, lacerate the tip of the tail. Blood from the wound is collected as described previously. See Tables 177-5 and 177-6 for hematology and chemistry values.


Oral Medications: Nutritional Support

Incorporate oral medications into a treat, or administer them in liquid form. If the medication is palatable, administer it by placing the tip of a dosing syringe into the diastema.

Administer medication in small amounts. Ensure that the animal swallows the medication in its mouth before more is administered. This technique is useful for force-feeding pellet gruels to anorexic pets if the caregiver is patient. Medication or food that is administered too quickly will be spit out or aspirated.

For rodents that are intractable or for administration of unpalatable substances, pass a stomach tube per os.

Metal feeding needles, red rubber urinary catheters, or infant feeding tubes work well. Selection is based on the size of the animal and individual preference. Metal feeding needles with ball tips frequently are used in patients weighing less than 100 g (Fig. 177-5). The metal provides the necessary stiffness to pass a tube of small diameter. The ball at the end of the needle makes it difficult (but not impossible) to pass the tube into the trachea. These tubes have the potential to create esophageal tears with improper restraint or when excessive force is applied.

A flexible catheter is ideal for use as a stomach tube in larger rodents (Fig. 177-6). Use a speculum to prevent chewing on the tube. An otoscope head, avian speculum, or piece of wood or plastic with a hole drilled in the center works well. Measure and mark the tube for the distance from the tip of the nose to the last rib. Place the speculum in the mouth and over the tongue. Pass the tube while holding the speculum in place and slightly ventroflexing the head. Resistance is encountered if the tube is malpositioned or is an inappropriate size. The tube must pass over the tongue before it can be advanced down the esophagus. This is difficult in some animals. Palpate the throat to confirm the presence of the feeding tube in the esophagus.


Premedication and Patient Preparation

Inhalation Anesthesia

Endotracheal Intubation

Most pet rodents are not intubated for anesthesia because of their small size. When necessary, as in prolonged oral and other procedures, endotracheal intubation is accomplished with the animal in dorsal or ventral recumbency, depending on the clinician’s preference. Small non-cuffed or Cole endotracheal tubes work well. A stylet usually is required to provide enough stiffness for the tube to pass the larynx. Extend the animal’s head and neck. Grasp the tongue with forceps and use gentle traction. The tip of the tube then is advanced above the tongue and just past its base. The hard palate is used to deflect the tip of the tube ventrally into the glottis. This is a blind procedure that is difficult to master. Use of a laryngoscope is helpful in larger rodents.

Another technique is to place an over-the-needle catheter in the trachea and move it up retrograde through the larynx to act as a guide. The catheter is removed after the endotracheal tube is in place.

The small diameter allows these tubes to collapse or kink, resulting in asphyxiation of the patient. Check patency at least every 2 minutes by applying positive pressure ventilation at 10 to 15 cm water and watching for excursion of the chest wall. If extending the head and neck does not result in air flow, suction the tube. If this is either not successful or impossible, remove the tube and continue anesthesia with a mask or reintubate the animal with a new tube. Because of the small diameter of the trachea, endotracheal tube-induced tracheitis and subsequent swelling of the trachea may become a life-threatening situation.


Dental Procedures

Incisors can be trimmed with nail trimmers, but this technique often fractures the tooth, causing abscesses of the root. Instead, use a high-speed dental burr or a flat cutting disk on a Dremel hand tool. Trim molars with a high-speed drill or pediatric rongeurs. A mouth speculum that deflects the tongue and other soft tissues is essential to prevent lacerations and provide working space (Fig. 177-8). Intubate the trachea to prevent aspiration pneumonia when working on molars.

If a tooth is abscessed, extract both it and the occlusal tooth.

In chinchillas with dental malocclusion, the roots of the molars can become impacted, causing swelling of the mandible or exophthalmos and epiphora. These teeth are extremely difficult to extract without causing extensive bony and soft-tissue damage. Discourage breeding of animals with malocclusion, unless it was acquired as a result of trauma or infection, because this trait is hereditary.


Most pet and laboratory mice are derived from Mus musculus, which is the common house mouse. Mice sold in the pet trade are randomly bred and less likely to suffer from the genetic problems associated with inbred laboratory rodents. Mice possess brown fat tissues between their scapulae that also are known as hibernating glands; these are thought to provide an energy store. The spleen in male mice is 50% larger than that of females.


Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Pet Rodents

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