Rodent Medicine
American Association of Zoo Veterinarians Conference 2010
Gary West, DVM, DACZM
The Phoenix Zoo, Phoenix, AZ, USA


The word rodent comes from the Latin verb rodere, meaning to gnaw.

Rodents have continuously erupting incisors, strong cutting incisors. Compared to rabbits, the rodents only have one pair of upper incisors.

Order Rodentia

 Over 1700 species in 29 families

 About half of the living species of mammals

 Rodentia is split into three suborders

 Myomorpha ("rat-like" rodents): rats, mice, hamsters, gerbils

 Hystricomorphia ("porcupine-like" rodents): guinea pigs, chinchillas, degus

 Sciuromorpha ("squirrel-like" rodents)

Anatomy and Physiology

Dental Anatomy

 Four incisors (2 upper, 2 lower)

 Hypsodont or elodont (continually growing from the base)

 Outer surface is enamel, inner surface is dentin

 Yellow color of the enamel is from iron deposits

 No canines with a large space between the incisors and the molars (diastema)


 Variable numbers of premolars and molars

 Molars are constantly growing in guinea pigs and chinchillas (elodont)

 Consist mostly of dentin

Oral Cavity

 Tongue is short and compressed

 Many rodents have cheek pouches

Gastrointestinal System

 Stomachs vary from simple (rats) to ruminant-like (hamsters, lemmings)

 Cecum is varied, with guinea pigs having a complex cecum

Respiratory and Cardiovascular System

 Small thorax: therefore, heart volume and lung field very small compared to size of abdominal cavity or body.

 Prone to cardiovascular shock and respiratory collapse under stress condition.

 Prone to heat stroke at environmental temperature of 82-86F (28-30°C)

 Rodents are obligate nasal-breathers

 Rapid normal heart rates

 Rodents are difficult to intubate

Renal System

 Kidneys are relatively large for the size of the animal

 All rodents have a simple, single-lobed kidney

Integumentary System

 Many rodents have specialized glands that function as scent glands for territorial marking: different location in different species

 Rodents lack sweat glands and are unable to pant

Reproductive System

 Determination of sex may sometimes be difficult

 Early puberty

 Short gestations

 Copulatory plugs

 Found in the female tract after copulation

 Can be used as a visible sign of breeding

 Produced by the male accessory glands


 Harderian glands produce porphyrins

 Cause red colored tears and urine: mainly rats, mice, gerbils

 Thymus is often found in adult animals

 Brown adipose tissue used for metabolic heat production

Determining the Sex of Mature Rodents



Anogenital distance is longer in the male.

Anogenital distance is shorter in the female.

 Manipulate genital papilla (prepuce) to protrude penis

 Palpate for testicles either in a scrotal sac (if present) or subcutaneous in inguinal region

 Males have only two external openings in the inguinal area:


 Urethral orifice at tip of penis.

 In very fat males, there may be a depression between the penis and anus. This depression can be obliterated by manipulating the skin in that area.

 Look for three external openings in the inguinal area:

 Anus (most caudal opening)

 Vaginal orifice (middle opening)

 Urethral orifice at tip of urethral papilla (most anterior opening)

 The urethral papilla is located outside the vagina (unlike dogs and cats)

 In very fat females or young females, the vaginal orifice may be either hidden by folds of skin (the former) or sealed (latter). Gentle manipulation of the skin in this area will divulge the orifice.

Rodents of various suborders show some differences in their biological characteristics which are discussed separately.

Guinea Pigs and Chinchillas


Family: Guinea pigs – Caviidae
Genus/species: guinea pig – Cavia porcellus

Family: Chinchillas – Chinchillidae
Genus/species: long-tailed chinchilla – Chinchilla laniger

 All families are related to each other

 All are originating from Andean highland in South America. They are well adapted to cold and dry environment.

 Guinea pigs and chinchillas are crepuscular (more active during dusk and dawn)

 All of these species live in family groups consisting of one reproductive male and several females with their offspring.

 Guinea pigs and chinchillas are all very social and less territorial than rabbits. Males may fight other males out of their area.

 They are seeking physical contact and crowd together, but they do not groom each other like other social animals. Hair pulling and ear nibbling are signs of social stress.

 These are the only rodents that give birth to fully developed young (precocious). They are born with fur, open ears and eyes, and their teeth have already changes in utero.

Biological Data


Guinea Pigs


Weights (in grams)

M: 900 – 1200

M: 400 – 600

F: 700 – 900

F: 450 – 650

Life span (in years)

4 – 8

12 – 20

Sexual maturity (in days)

28 – 35

6 months

Gestation (in days)

59 – 72

110 – 114

Litter size / birth weight

2–5/50–100 g

1–4/30–50 g

Weaning (in weeks)

2 – 3

6 – 8

Anatomy and Physiology

Gastrointestinal System

 Similar to other rodents

 High metabolic rate: fasting not recommended

 Oral cavity
Incisors and molars have open roots (hypsodont) and are permanently growing
Guinea pigs and chinchillas have a palatal ostium, an opening in the soft palate

Thin muscular wall
Unable to vomit

Large and complex: ½ of abdominal cavity
Fermentation by microflora
Cecotrophy / coprophagy: see rabbits

Urogenital System

Female Reproductive Tract

Guinea Pigs

 Urethral orifice separate from vaginal orifice

 Seasonal polyestrus, estrus cycle: 15–17 days

 2 inguinal mammary glands

 Uterus duplex: 2 uterine horns, but one cervix

 Vaginal closure membrane, that perforates at estrus and parturition

 Pelvic symphysis: fibrocartilaginous; can ossificate in non breeding animals older than 7–8 months, therefore dystocia can occur.

 Do not build nests


 Seasonal polyestrus, estrus cycle: 30–50 days

 3 pairs of mammary glands: 1 thoracic, 2 inguinal

 Uterus duplex, cervix duplex: also cervix lumen separated by septum

 Vaginal closure membrane only perforating during estrus and parturition

 Large urinary papilla: looks similar to prepuce of males

 Do not build nests

Male Reproductive Tract:

Guinea Pigs

 Obvious scrotal sacs with large testes surrounded by a large fat body

 Penis in tubular prepuce, easy to extrude by placing gentle pressure at its base


 No true scrotum: testes kept in inguinal canal or abdomen

 Postanal sacs: 2 movable sacs next to anus, into which epididymis can drop

 Penis in papilla-like prepuce, easy to manually extrude

Musculoskeletal System:

 Fragile bones compared to body size and weight.

 Guinea pigs have small thin feet and legs: walking

 Chinchillas have thin feet, but strong legs: climbing and jumping ·

Nervous System and Sensory Organs

Guinea Pigs

 Olfactory and auditory senses well developed

 Small eyes

 Thin-walled auditory bullae


 Well developed olfactory and auditory senses

 Very large, thin-walled auditory bullae

 Large eyes, sitting in shallow bony orbit

 Iris densely pigmented, with vertical pupil: adaptation to UV-light in high-altitude

Skin and Adnexa

Guinea Pigs

 Fur straight, curly or long-haired depending on breed

 No tail

 Sebaceous gland as marking gland on dorsal tail base

 Anal glands for marking


 Fur very soft and dense: up to 50–60 hairs growing from one single hair follicle

 Long strong furred tail with bushy end: tail hair hard

 Thin nails, not claws

 Anal glands for marking

Mice and Rats


Family: mice-like rodents – Muridae

Species: House mouse / lab mouse – Mus musculus

Brown rat / lab rat – Rattus norvegicus

 Pet mice and rats are originating from laboratory animals.

 Very social and live in large colonies consisting of one dominant reproductive male and several females with their offspring

 Territorial and mark their area with urine, feces and scent from anal glands. Males tolerate each other when they grow up together. But they fight against new males as invaders and these fights can be fatal.

 Mice and rats are well adapting to their environment and are opportunistic omnivores. They use their front paws to hold food and to climb. They like to gnaw and are able to chew through thick wooden walls.

 Rats are very intelligent and curious. It is possible to build a close human-animal bond with them.

Biological Data




Weights (in grams)

M: 55 –100

F: 250 – 300

F: 65 – 110

M: 350 – 500

Life span (in years)

2 – 4

2 – 3.5

Sexual maturity (in days)

10 – 36


Gestation (in days)

18 – 24

21 – 23

Litter size / birth weight

4 – 8

4 – 14 / 5 – 6

First hair (in days)

2 – 3

2 – 3

Eyes open (in days)

12 – 14

12 – 15

Weaning (in weeks)



Anatomy and Physiology

Gastrointestinal System

 Oral cavity:

 Only incisors open-rooted and permanently growing

 Molars are fixed rooted

 GI system

 Rats lack a gallbladder

Urogenital System

 Female reproductive tract

 Polyestrus, spontaneous ovulation

 Mice: 5 pair of mammary glands

 Rats: 6 pairs of mammary glands

 Glandular tissue of mammary glands reaching over shoulder and to perianal region

 Uterus duplex, cervix simplex

 Copulatory plug: appearance in cage confirming mating

 Male reproductive tract

 Large scrotal sacs with large testes surrounded by large fat body

 Wide inguinal canal

 Tubular prepuce, penis easily extruded by gently putting pressure on its base

Nervous System and Sensory Organs

 Olfactory and auditory sense well developed

 Rats have better developed vision than mice

 Porphyrin-rich, fluorescent, red secretion from Harderian glands: ocular lubrication and pheromone-mediated behavior

Skin and Adnexa:

 Long tail virtually hairless with rasplike skin

 Hairless soles

 No sweat glands

 Anal glands for marking

Gerbils and Hamsters


Gerbils are closer related to hamsters, but show mainly characteristics like mice and rats

Family: Diggers – Cricetidae

Genus: Middle hamster – Mesocricetus

Species: Syrian golden hamster – Mesocricetus auratus

Russian dwarf hamster – Phodopus roborovskii

Genus: Gerbils – Gerbillus

Species: Mongolian gerbil – Meriones unguiculatus


 Originating from Central Asia and Africa; Mongolian gerbil is commonly kept as pet.

 Social like mice and rats; big families consisting of a dominant male with several females and their offspring; males territorial, tolerate other males only when they are related to them and have never left the group; once a male leaves the family it will no longer be accepted and eventually killed when put together again.

 To alert their mates for danger or when they get very excited they drum with their hind feet

 Mainly active during dusk and dawn (crepuscular)

 Adapted to a desert environment, drink only a little and can obtain most of the water requirement from soft food and metabolic processes


 Hamsters kept as pets originate from Central Asia and Middle East

 Solitary animals; very territorial and attack and possibly kill other hamsters in their area. They tolerate only hamsters of the opposite gender in their environment.

 Strictly nocturnal

 Originating from a desert-like environment and need less drinking water, produce less urine

 Lower temperature stimulates hamsters to gather food and they go into hibernation, when temperature falls below 41°F

Gastrointestinal System


 Cheek pouches:

 Evaginations of oral mucosa

 Paired muscular sacs


 Extending as far as the scapula

 Transporting food, bedding material, young


 High pH

 Containing microorganisms

Urogenital System


 Vaginal discharge: after ovulation, whitish

 Paired vaginal pouches to collect exfoliated cells and leukocytes

Skin and Adnexa


 Furred and tufted tail

 No sweat glands

 Sebaceous/scent gland: ventral marking gland; noticeable in both genders as an orange-tan area of alopecia on the mid-ventral region of body wall, next to the umbilical area


 Short furred tail

 No sweat glands

 Sebaceous/scent glands: flank glands; noticeable as brown hairless patches behind rib bows, more developed in males.

Husbandry and Nutrition


Most Rodents Are Social

 Should not be kept solitary

 Young animals tolerate each other best; siblings tolerate each other best

 If females and males are kept together, birth control needs to be considered

 Hamsters should be kept solitary

 Can be kept indoors or outdoors (except smaller rodents)

 Cage construction:

 Hutches: only recommended for guinea pigs; other rodents may escape by chewing through wire cages

 Plastic bins with cover

 Wire floor should be avoided

 Zinc wire should be avoided


 Hiding box: with shavings; with shredded paper or nesting cotton for hamsters


 Climbing material


 Heavy food dishes

 Water bottle or water bowl

 Chewing material: branches, hard hay, cardboard

Cage Substrate

 Wood chips

 Saw dust shavings

 Paper, paper towel

 Straw, hay


 Temperature: 40 – 80°F, preferable room temperature; over 85°F: heat stress

 Drastic temperature should be avoided

 Humidity: 40 –70%

 Draft should be avoided

 Quiet area

 Cage not on floor level to avoid stress

 Free roaming on a daily base for exercise, but only supervised

 Outdoor cages need to be secured:

 Against escape by digging underneath fence

 Against predators (foxes, dogs, raptors)


 Rodents should, like any other animal, undergo quarantine before they are newly introduced into an existing group or collection

 Quarantined animals should be kept under similar husbandry condition as normally recommended and social animals should be quarantined in groups rather than solitary to avoid excessive stress impact

 New animals should be kept totally separate from other animals in collection

 Separate housings, tools, dishes should be used to avoid contamination and transmission of pathogens to other animals

 Quarantine period should be 30 days

 A thorough quarantine examination should be performed, ideally with blood collection for CBC, and few chemistry values, fecal culture and fecal parasitology


 Nutritional conditions are similar to other herbivorous animals. High fiber should be main basis ingredient in diet.

 For most of the popular rodent pets there have been special pelleted diets developed. Their content of vitamins and minerals is supposed to meet the requirement of the species, but the quality of the diet greatly depends on the storage conditions. It is recommended only to acquire smaller amounts of feed to avoid molding, destruction of vitamins and other ingredients, and cultivating pathogenic agents and insects.

Ideal Diet for Rodents:

 Pelleted diet

 Feed mixture for rodents: seeds, cereals, dried fruits and veggies, vitamins, minerals in form of pellets (problem: selective eaters)

 Additional: hay, fruits, veggies

 Sunflower seeds, nuts, raisins: only as occasional treats

Special Requirements for Some Species:

Guinea pigs:

 Vitamin C is essential: dark green leaves, herbs such as parsley, dandy lion leaves; bell peppers; fruits such as: oranges, mandarins, kiwis


 Have a very sensitive intestinal tract

 Do not tolerate too much soft food or sugars

 Hay, herbs, dried veggies, fruits

Mice, rats:


 Dog dry food; milk products such as cheese, cottage cheese, ricotta, yogurt, veggies, fruits

Daily Food Intake of Some Exotic Pets


Food intake (g/day)

Water intake (ml/day)


50–100 / kg BW

50–10 / kg BW

Guinea pigs

6 / 100 g BW

10 / 100 g BW





5–10 / 100 g BW

8–11 / 100 g BW

Hamsters, Gerbils




Office Visit

 Initial telephone conversation

 Ask the client to bring animal in with its cage (without cleaning cage)

 Empty the water container prior to transport

 Bring a small sample of animal's food

 Bring any medication or dietary supplements being given

 If cage is not portable

 Ask them to obtain a secure portable enclosure for transporting

 Advise the client you will need a detailed description of the home cages


Many of the exotic pets are non domestic animals and some species, such as rabbits and rodents, are potential prey. Thus, they are easily stressed by unfamiliar environment. Stress-induced catecholamine release can lead to increase in vital parameters such as heart rate, respiratory rate and body temperature.

Therefore, it is important to give those patients some time to acclimate to the new environment while asking questions to the owner regarding husbandry and nutrition and getting a good history.

As many diseases in exotic pets occur because of poor or sub-optimal husbandry and nutrition, it is very important to take a good history before the examination of the animals.

A thorough history collection should include the following:

Information About the Animal

 Species, breed, age, sex, purpose

 Acquisition: breeder, wild-caught, import

 Length of ownership

 Purchase of new animals

 Quarantine conditions

 Moving, transport, vacation out of country

 Preventive medicine: vaccinations

 Breeding: breeding status, problems

 Former diseases: development, treatment (owner, veterinarian)

Information About the Problem


 When first signs

 Development, process

 Treatment: owner, veterinarian

Information About Husbandry


 Composition of group: numbers, sex, adults, offspring

 Other animals in household


 Indoors: cage, bin, room

 Outdoors: barn, hutches, size of enclosure, space for exercise



 Wire construction

 Floor construction

 Opportunity to hide

 Nest / sleeping box

 Perches / shelves

 Toys, chewing material

 Position of food and drink dishes

 Environment of cage or hutch:

 Quiet / busy

 Daylight / sunlight: photo period, sun exposition




Information About Nutrition

 Feeding technique: dishes, on floor, food dispenser

 Frequency: ad libitum, certain times


 Commercial diet: pellets, mixture

 Own preparation of mixtures

 Quality: content of roughage, protein, fat, vitamins, minerals

 Content of fresh food in diet

 Water access: bowl, bottle; ad libitum, certain time; quantity


The first step of the examination of an exotic patient is to observe the animal in its cage for its behavior, posture, obvious external changes, as well as for respiration pattern and respiration rate.

If the animal is presented in its own cage, the interior and bedding may give an idea of the quality of the husbandry.

Animals with mental and neurological disorders can show changes in their behavior. They may be overexcited or depressed. Depression is shown by drooping the head, ears, and whiskers, and showing no response to environmental stimuli.

Animals in pain mostly have a ruffed hair coat and half-closed or closed eyes. The respiratory rate is increased and the animals breathe superficially or show panting. They mostly show reluctance to move, sudden aggression, apprehension, anxiety. They may be lying stretched out or sit in hunched position. In rabbits, the grinding of teeth is a typical sign for pain.

Nervous and distressed animals will defecate and the feces may be softer than normal or loose, which has to be differentiated from gastrointestinal problems.


For a closer examination the patient has to be restraint. Therefore, the animal should be approached calm and fast movements have to be avoided.

Calm animals of larger species, such as guinea pigs, chinchillas, and rats can be held with one hand under the thorax and the other hand is supporting the pelvic girdle.

Chinchillas should be held at the tail base and around the thorax or neck if they try to escape. They should never be scruffed by the fur. They are able to actively release their hair causing fur-slip. Fur farmers will not be happy about that because it takes months for the fur to gain its quality back.

Hamsters can be held in one hand. To keep the animal calm, it can be covered with the other hand.

Long-tailed rodents such as rats, mice, and gerbils can be grabbed with one hand at the tail base. After lifting the animal, the body is supported with the other hand. The tail always has to be held only at the base. Otherwise, the grip can cause sloughing of the tail skin.

To transport smaller rodents, they are held between the palms where they feel safe, like in their nest. Larger rodents are set on one forearm and hand, while the other hand is covering the body. Chinchillas are held at the tail base and the body is supported by one hand and forearm.

Aggressive rodents or such not used to be handled need to be scruffed in the neck taking as much fur as possible in the palm of the hand to prevent the animal from turning the head towards the fingers.

Physical Examination

 Determine the apparent age and sex

 Visually examine all body orifices for discharges, exudates, etc.

 Examine skin for hair loss, cuts, abrasions, abscesses, tumors, ectoparasites

 Palpate limbs, thorax, abdomen, back and vertebral column and genitalia

 With animal well restrained, examine the mouth and teeth, complete oral examination

 Examine the ears for excessive cerumen or evidence of mites

 Examine the eyes for excessive fluid, drying, conjunctivitis, corneal lesions

 Listen for rales by holding animal near your ear

 Do not attempt to take temperature of small rodents, it can cause severe stress and rectal prolapse

Diagnostic Procedures

Fecal Examination

 Native samples: color, consistency

 Samples for laboratory diagnostics: parasitology, bacteriology

Urine Samples

 Spontaneous urine:

 Collection from plastic bin underneath wire cage

 Setting them on cold surface or in cold plastic bag stimulates urination

 Palpation and expression of bladder

 pH: 8–9

 Specific gravity:

 Mice / rats: 1020 – 1050

 Gerbils / hamsters: up to 1060

 Rodents normally show some proteins, glucose and bilirubin in the urine; high on calcium-carbonates

 Rats, mice, hamsters, gerbils: some acetone normal; high on calcium and/or magnesium-carbonates, depending on diet

Blood Collection


 Jugular vein

 Lateral saphenous vein

 Femoral vein

 Cephalic vein


 Lateral tail veins

 Ventral tail vein

 Cephalic or saphenous veins

Guinea Pigs, Rats, Mice, Hamsters, Gerbils

 Jugular vein

 Lateral saphenous

 Vena cava (risk of thoracic hemorrhage and death)


 Guinea pigs have very thick skin, blood collection is very difficult

 Small rodents need to be anesthetized for blood collection

 Potentially very stressful on awake animals

Hematological and Chemical Values

 Leukocytosis: stress, digestion, pregnancy, muscular stress

 Leukopenia: viral infections, toxic influence (endotoxins), drugs (steroids, chloramphenicol, chemotherapy)

 Guinea pigs: low ALT levels, high cholesterol levels, Kurloff cells (unique leukocyte)

 Gerbils: short-lived RBC, so basophilic stippling of RBCs common

 The chemistry values change under same conditions as in other mammals. Rodents living in a desert-like environment show higher BUN and protein levels.

Other Sample Collections

 Swabs from discharge: nasal, ocular, vaginal, preputial discharge for culture and sensitivity

 Fine needle aspiration of swellings, lymph nodes for cytology, culture and sensitivity

Further Diagnostics

 Radiology / ultrasound (most commonly under anesthesia)

 Bone marrow aspiration (under anesthesia)

 Can be performed in small mammals. The sites for aspiration are femur, tibia, and sternebrae. The procedure is performed under the same criteria as in other mammals.

Treatment Procedures

Per Oral Administration (PO)

 Over food / water

 In mouth: via syringe dripping small portions of liquid food on tongue and let animal swallow (ideal for owners)

 In stomach: via tube, gavage needle

 Under proper restraining

 To check position of tube: inject few drops of sterile water or saline first

Subcutaneous Injection (SC)

 Under skin fold in flank

 Area between shoulder blades should be avoided, especially in guinea pigs because of their fat storage

Intramuscular Injection (IM)

 Small volumes of drugs can be administered into the muscles

 Muscles of the hind limbs are well developed in most of the small mammals

 Quadriceps muscles are preferred because the caudal muscles of the hind legs are very thin and the risk of injury of the sciatic nerve high

Intraabdominal / Intraperitoneal Injection (IP)

 For larger volumes and faster absorption of drugs

 Often the most practical method of administering emergency medication to small rodents.

 The animal is restrained with the head down, a 22–25 gauge needle is introduced into the lower left quadrant of the abdomen. Injection is given slowly.

 Rats: left side to avoid cecum

 Gerbils, hamsters, and mice: right side to avoid spleen

Intravenous Injection (IV)

 Larger animals: same location as used for blood collection

 Only used for non irritating drugs in very small amounts

 IP is preferred, especially in smaller animals

 Fluid therapy commonly via IP or IO

Intraosseous Injection (IO)

 Preferred for fluid therapy in smaller animals

 Common needles can be used

 Femur: Proximal, just over greater trochanter (proximal tibia also possible), hair clipped and area antiseptically prepared; needle inserted through cortex with rotation movements

 Catheter can be left for up to 48 hours, fixed by bandages

Emergency and Critical Care

As potential prey, rodents try to hide weakness and sickness so as not to be preyed upon. Therefore, many disease conditions are often overlooked and the animals are presented at the veterinarian in the stage of decompensation, in critical condition and need of emergency care.

Critical conditions in rodents are:

 Energy loss (anorexia, chronic diseases)

 Endotoxemia / septicemia

 Gastrointestinal distress

 Respiratory distress


 Heat stroke

 Head / eye trauma / neurological conditions

 Trauma with blood loss



 Pregnancy toxemia

 Urinary obstruction

 Severe systemic diseases

Energy Loss

This is probably the most common critical condition in rodents. Due to their small body size and large body surface, they have a high metabolic rate to cover their high consumption of energy. Thus, anorexia for 24–48 hours can get these animals into a negative energy balance and in critical condition. Lack of food intake can create a vicious cycle, because a reduced food intake causes stasis of ingesta in stomach and cecum. This leads to a change of the microflora in the cecum followed by gas formation and bloating. In this condition the animals often refuse further food intake.

Reduced food intake and anorexia can be caused by:


 Change of microflora (diet, drugs)

 Systemic diseases


 Trauma (facial bones oral cavity)

 Neurological disorders (head trauma)

Critical care includes:

 Increase of energy intake:

 Fluids with electrolytes, amino acids, vitamins

 Force feeding: syringe, tube

 Decrease of further energy loss / shock treatment

 Heat source

 Quiet environment · oxygen


 Coverage against underlying or secondary diseases


 Replacement of intestinal microflora: (Controversial)

 Cultures of lactobacilli


 Inoculation of normal flora of healthy animal into sick animal

 Commercial products may have Gram negative bacterial contamination

Ingredients of force feeding formula for rodents:

 Good commercial critical care diets (Oxbow®)

 Ensure (high fiber)

 Baby food (veggies, fruits)

 Blenderized normal diet, cereals, fruits and veggies

 Alfalfa meal


 Fruit juices

 Jam, syrup


General Anesthesia Principles

 Determine an accurate body weight

 Monitor patient throughout the anesthetic period

 Prevent hypothermia

 Maintain hydration

 Prevent corneal ulceration

Monitoring Anesthesia

Order of loss of reflexes



 Jaw tone

 Ear pinch reflex (surgical plane)

 Monitor the respiration and heart rates: stethoscope, pulse Doppler ultrasound, ECG, and pulse oximeter


Isoflurane or Sevoflurane are the anesthetic agents of choice for all small mammals because of the short induction and recovery time. The gas is also eliminated to a high percentage via the airway and there is low accumulation in the tissues.


 Via face mask

 Via Plexiglas chamber


 Via face mask

 Via endotracheal tube (difficult in rodents)

The use of atropine sulfate to reduce excess of oral and respiratory mucus is limited due to production of atropine esterase in some rodents (rats). Therefore, it is recommended to use glycopyrrolate in a dose of 0.01–0.02 mg/kg SC.

Injectable anesthesia is generally not recommended, depends on the type and length of procedure, as well as the condition of the animal.

Analgesia is often given as premedication or sedative (opioids such as buprenorphine are commonly used), NSAIDS (with good hydration).


General Principles

 Obtain an accurate body weight

 Most medications used in rodents are "off-label" usage

Reported Adverse Reactions to Drugs

 Neuromuscular blockade in mice and gerbils caused by streptomycin and dihydrostreptomycin

 Procaine, included in some penicillin preparations, can be toxic to mice and guinea pigs

 Guinea pigs and chinchillas are highly susceptible to the ototoxic effects of aminoglycosides at dosages above those recommended clinically

Antibiotic Associated Enteritis (AAE)

Pathogenesis is caused by microflora changes induced by the antibiotics, allowing the growth of abnormal bacteria. Antibiotic treatment can result in enteritis and antibiotic associated clostridial enterotoxemia, especially when antibiotics with a primary Gram-positive spectrum are given. Incidence is higher when agents are given orally. Chinchillas, guinea pigs, and hamsters are most susceptible.

Drugs that could induce AAE include







Rodents with AAE need immediate supportive care (heat, fluids, steroids, force feeding).

Common Diseases

Mammary Neoplasia (Rats)


 Early OVH

 Prolactin dependent/Melatonin

Respiratory disease complex (rats)


 Mycoplasma pulmonis

 Other bacteria, viruses, husbandry, age and immunocompromised


Because rodents are often purchased as children's pets, trauma to pet rodents is common. Common traumatic injuries:

 Broken bones

 Blunt abdominal trauma

 Neurological injuries

Malnutrition and Dehydration

Most rodent owners have only an elementary understanding of how to keep their pets healthy. Many sick rodents are presented with simple dehydration and starvation. Typical examples of this type of problem include clogged water bottles or food bowls filled with seed hulls and no edible food. Additionally, problems associated with food quality and quantity can lead to malnutrition or obesity. Treatment usually consists of supportive emergency care and subsequent client education to correct the problem.

Common Errors

 Lack of water

 Inappropriate food


Dental Disease

Malocclusions are a common problem that can be caused by trauma, infection, and genetic predisposition. Often the presenting complaint is weight loss, anorexia, drooling, ptyalism.

Gastrointestinal Disease

 Food-related diarrhea

 Antibiotic Associated Enteritis (AAE) - see above

 Salmonella (Mouse typhoid, parathyroid)

Respiratory Diseases

Pneumonia is a major cause of morbidity and mortality in rodents. Various etiologies are possible, but the clinical signs of hunched posture, lethargy, anorexia, nasal discharge, and dyspnea are similar in all rodents.

Other (can be difficult to diagnose antemortem)


 Atrial thrombosis (hamster)

 Myocardial fibrosis

 Calcification of great vessels

 Nephrosis/Glomerular sclerosis with renal fibrosis (rat), nephritis (guinea pig), amyloidosis

 Cheek pouch prolapse (hamster)

 Radiculoneuropathy (rat) hind limb ataxia and proprioceptive deficits

Dermatological Diseases

Rodents often present with alopecia and pruritus. Associated finding are roughened hair coat, weight loss, anorexia, and excoriation of the skin. The diagnosis and treatment of these conditions are similar to other domestic species.

 Barbering (hair loss caused by cage mates)

 Bite wounds


 Guinea pigs secondary to osteoarthritis

 Dermatophytosis (ringworm)


 Lice (Polyplax in rats): Commonly seen in immunocompromised rats, treat with selamectin

Reproductive Diseases


 Guinea pigs: when bred older than 7 months for the first time (reduced distension of pubic symphysis)


 Common in guinea pigs, hamsters

 Ovarian Cysts

 Common in guinea pigs

Musculoskeletal System

Hypovitaminosis C (Scurvy)

In guinea pigs due to vitamin C deficiency of diet, guinea pigs lack enzyme to endogenously synthesize Vitamin C.

Clinical signs: subcutaneous, intraarticular, intramuscular hemorrhage, followed by lameness, pain, reluctance to move; also seen crusty lips, hemorrhage of gingival, loose teeth, poor hair coat

Endocrine System

 Pituitary adenomas


 Common in hamsters, rats, guinea pigs


Very common in rodents, especially rats, mice, hamsters


Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Gary West, DVM, DACZM
The Phoenix Zoo
Phoenix, AZ, USA

MAIN : EAMCP Conference : Rodent Medicine
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