Taxonomy
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)
Molars
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
Miscellaneous
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
|
Male
|
Female
|
|
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:
Anus
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
Biology
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
|
Chinchillas
|
|
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
Stomach
Monogastric
Thin muscular wall
Unable to vomit
Cecum
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
Chinchillas
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
Chinchillas
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
Chinchillas
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
Chinchillas
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
Biology
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
| |
Mice
|
Rats
|
|
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
|
45
|
|
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)
|
3
|
3
|
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
Biology
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
Gerbils
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
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
Hamsters
Cheek pouches:
Evaginations of oral mucosa
Paired muscular sacs
Reversible
Extending as far as the scapula
Transporting food, bedding material, young
Forestomach:
High pH
Containing microorganisms
Urogenital System
Hamsters
Vaginal discharge: after ovulation, whitish
Paired vaginal pouches to collect exfoliated cells and leukocytes
Skin and Adnexa
Gerbils
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
Hamsters
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
Housing
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
Furniture
Hiding box: with shavings; with shredded paper or nesting cotton for hamsters
Shelves
Climbing material
Tubes
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
Environment
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)
Quarantine
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
Nutrition
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
Chinchillas:
Have a very sensitive intestinal tract
Do not tolerate too much soft food or sugars
Hay, herbs, dried veggies, fruits
Mice, rats:
Omnivorous
Dog dry food; milk products such as cheese, cottage cheese, ricotta, yogurt, veggies, fruits
Daily Food Intake of Some Exotic Pets
|
Species
|
Food intake (g/day)
|
Water intake (ml/day)
|
|
Rabbits
|
50–100 / kg BW
|
50–10 / kg BW
|
|
Guinea pigs
|
6 / 100 g BW
|
10 / 100 g BW
|
|
Mice
|
10–15
|
3–4
|
|
Rats
|
5–10 / 100 g BW
|
8–11 / 100 g BW
|
|
Hamsters, Gerbils
|
5
|
2
|
Examination
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
History
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
Symptoms
When first signs
Development, process
Treatment: owner, veterinarian
Information About Husbandry
Single/group
Composition of group: numbers, sex, adults, offspring
Other animals in household
Indoors/outdoors
Indoors: cage, bin, room
Outdoors: barn, hutches, size of enclosure, space for exercise
Cage:
Size
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
Ventilation
Temperature
Humidity
Information About Nutrition
Feeding technique: dishes, on floor, food dispenser
Frequency: ad libitum, certain times
Diet:
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
Observation
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.
Restraining
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
Chinchillas
Jugular vein
Lateral saphenous vein
Femoral vein
Cephalic vein
Rats
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)
Considerations
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
Hypothermia
Heat stroke
Head / eye trauma / neurological conditions
Trauma with blood loss
Intoxications
Dystocia
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:
Malocclusion
Change of microflora (diet, drugs)
Systemic diseases
Obstruction
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
Fluids
Coverage against underlying or secondary diseases
Antibiotics
Replacement of intestinal microflora: (Controversial)
Cultures of lactobacilli
Yogurt
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
Yogurt
Fruit juices
Jam, syrup
Anesthesia
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
Palpebral
Pedal
Jaw tone
Ear pinch reflex (surgical plane)
Monitor the respiration and heart rates: stethoscope, pulse Doppler ultrasound, ECG, and pulse oximeter
Anesthetics
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.
Induction
Via face mask
Via Plexiglas chamber
Maintenance
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).
Chemotherapeutics
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
Amoxicillin
Ampicillin
Clindamycin
Erythromycin
Lincomycin
Tetracycline
Rodents with AAE need immediate supportive care (heat, fluids, steroids, force feeding).
Common Diseases
Mammary Neoplasia (Rats)
Fibroadenomas
Early OVH
Prolactin dependent/Melatonin
Respiratory disease complex (rats)
Multifactorial
Mycoplasma pulmonis
Other bacteria, viruses, husbandry, age and immunocompromised
Trauma
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
Overfeeding
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)
Cardiomyopathy
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
Pododermatitis
Guinea pigs secondary to osteoarthritis
Dermatophytosis (ringworm)
Mange
Lice (Polyplax in rats): Commonly seen in immunocompromised rats, treat with selamectin
Reproductive Diseases
Dystocia
Guinea pigs: when bred older than 7 months for the first time (reduced distension of pubic symphysis)
Endometritis
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
Hyperadrenocorticism
Common in hamsters, rats, guinea pigs
Neoplasia
Very common in rodents, especially rats, mice, hamsters