Internet Article: http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2004&PID=8661&O=Generic
Referenced: 10/27/05
Author: Sharon Redrobe, BSc (Hons), BVetMed, CertLAS, CertZooMed, MRCVS Head of Veterinary Services,
Bristol Zoo Gardens, Bristol, UK
Basic Approach to the Small Mammal Patient
Rodents
General Anatomy
Dental formula 1/1 0/0 0/0 3/3. The incisors are chisel shaped, constantly growing and a pigmented yellow colour. When
gnawing the lower jaw moves forward so that the incisors oppose each other but the molars do not. The cheeks are
drawn in across the diastema (the gap between the incisors and molars). This enables the rodents to gnaw without
wearing the molars or swallowing debris. Rodents exhibit coprophagy--the act of eating faeces--to recover vitamins B and
K.
Sexing Rodents
Rat, mouse, gerbil, hamster, chipmunk
A papilla is seen in both sexes. In the male it is the tip of the penis, in the female it is the urethral papilla. The distance
between the anus and the papilla (ano-genital difference) is greater in the male. The nipples are more obvious in the
female. The male hamster has obvious testes which can be seen from above.
Guinea pig, chinchilla
The female has a membrane between the urethral orifice and the anus. The penis of the male can be extruded by gentle
pressure and the testes can be gently palpated either side of the anus. The retracted penis forms a Y shape in the
prepuce. Beware; both sexes of guinea pig have an obvious pair of teats in the inguinal area.
Handling and Restraint, Risks to Handler and Animal
Non-aggressive animals can be gentle cupped in the hand and restrained by the base of the tail. Take care with the gerbil
that may slough the skin from the tail if handled roughly. The rat, mouse, gerbil, hamster may be gently scruffed for
injection or examination by holding a flap of skin at the back of the neck. Hamsters have a lot of loose skin and so can
turn around in it and still bite if you have not grasped enough scruff!! Rats can beheld around the chest with the handlers
thumb beneath the animal's chin to prevent biting and the hindquarters supported. Take care not to squeeze, as it is easy
to suffocate the wriggling rat by accident. Handle guinea pigs using one hand around the shoulders and one hand
supporting the rump. The liver can be ruptured if the guinea pig is handled roughly around the middle. Chinchillas can
generally be scooped up in the hands. The base of the tail may be held for restraint. When the chinchilla is stress large
amounts of hair may be lost (= fur slip) and bald patches may result. Although the hair will regrow, the owner should
always be warned about fur slip before handling the animal.
Rabbits
Basic Anatomy
Rabbits are not rodents but lagomorphs. The rabbit dental formula is 1/1 0/0 3/2 3/3. They characteristically have long
ears, short fluffy tail, hopping gait and powerful hind legs. Rabbits perform caecotrophy--they eat the soft, mucous
covered caecal pellets straight from the anus. They also produce dry pellets that are not eaten. Urethra opens into
vagina, so rabbits do not have a separate external urethral papilla like rodents.
Sexing and Methods of Breeding
Males have round penile sheath from which penis can be extruded. The large bald scrotal sacs are obvious in the mature
male. The female has slit-like opening. Begin breeding of the doe between 4 and 6 months old. One buck can service 25
does. Doe taken to bucks cage and left for ten minutes. Taken to another buck if not mated. Artificial insemination is
used commercially and is very successful.
Handling and Restraint, Risks to Handler and Animal
Rabbits rarely bite but have sharp claws that can inflict painful scratches on the handler. Mishandling can lead to a
fractured spine of the rabbit. The rabbit has powerful hind legs and will attempt to kick out or escape if frightened. Pick
up the rabbit firmly around the shoulders or by the scruff. Support the hindquarters. Tuck the rabbit's head under your
arm when carrying. Once the head is covered, the animal is calmer and if it does struggle it will tend to push deeper
under your arm. Place the rabbit back into the cage rear end first to prevent kicking out at the handler. For restraint, hold
the animal with the rear end against your body and hands around the shoulders. To restrain for intravenous injection into
the ear veins, wrap the whole body in a towel, leaving only the head exposed.
COLLECTION OF SAMPLES
1. Blood: Maximum volume removed should not exceed 10% of circulating blood volume.
Species
Av. Adult
body
weight
(g)
Av. adult
blood
volume
(ml)
Maximum Route
sample
volume
(ml)
Mouse
25-40
2.5
0.25
Lateral tail vein
Gerbil/hamster
85-150
9
0.5
Cardiac puncture
Rat
300-500
30
3
Lateral tail vein
Guinea pig
700-1200
60
6
Ear vein
Rabbit
2000-6000
250
25
Marginal ear vein,
jugular, cephalic vein
Ferret
750-1000
50
5
Jugular or cephalic vein
2. Urine: Collected during voluntary urination
Most rats and mice urinate when restrained. Urethral catheterisation and cystocentesis are easiest in the rabbit, guinea
pig and chinchilla.
Administration of Substances
For each species, site of injection and maximum volume is given in the table below:
Species
Subcutaneous
Intramuscular
Intravenous
Intraperitoneal
Mouse
Scruff,
2-3ml
Quadriceps,
0.05ml
2-3ml
Lateral tail vein,
0.2ml
Hamster/gerbil Scruff,
3-4ml
Quadriceps,
0.1ml
3-4ml
Not practicable
Rat
Scruff, flank, Quadriceps,
5-10ml
0.3ml
10-15ml
Lateral tail vein,
0.5ml
Guinea pig
Scruff, flank, Quadriceps,
5-10ml
0.3ml
10-15ml
Ear vein,
saphenous vein,
0.5ml
Rabbit
50-100ml Marginal ear
Scruff, flank, Quadriceps,
30-50ml
lumbar muscles,
vein, 1-5ml
0.5-1ml
Clinical parameters of common mammal species
Mammal
Weight
Rectal
Approximate Approximate
range (g) temperature pulse rate/ respiratory
(°C)
minute
rate/minute
Chipmunk
100-250
38
200
100
Chinchilla
400-600
35.4-38
100
45-65
38
230-380
70-100
Guinea pig 500-1100
Hamster
85-120
37-38
280-500
35-120
Gerbil
45-130
39
260-600
90
Mouse
20-60
37.4
300-700
150-200
Gerbil
50-90
39
260-600
70-120
250-400
38
300-500
80-100
Rat
Common bacterial diseases
Bacteria
Clinical signs
Bordetella bronchiseptica
Conjunctivitis, pneumonia
Campylobacter
Diarrhoea, wet tail, rectal prolapse
Chlamydia
Perinatal mortality
Clostridium piliformis
Diarrhoea, weight loss
Corynebacterium spp
Arthritis, conjunctivitis, abscess, dermatitis
Fusobacterium necrophorum
Dermatitis, dental/jaw abscess
Klebsiella
Pneumonia, nasal discharge
Leptospira icterohaemorrhagica Vascular signs
Listeria
Perinatal mortality
Mycoplasma spp
Arthritis (M. arthritides), conjunctivitis, dyspnoea,
pneumonia, nasal discharge, infertility (M. pulmonis)
Pasteurella
Pneumonia (P. pneumotropica rodent, P. multocida rabbit),
abscess, perinatal mortality, dermatitis
Pseudomonas aeruginosa
Diarrhoea, dermatitis
Salmonella typhimurium,
S. enteritidis
Anorexia, septicaemia, diarrhoea, perinatal mortality
Staphylococcus
Abscess, dermatitis (Staph aureus)
Streptobacillus moniliformis
Limb/tail inflammation, necrosis
Streptococcus zooepidemicus
Pericarditis, abscesses of lymph nodes--mesenteric, cervical
Streptococcus
Septicaemia, pneumonia, abscess
2. Urine: Collected during voluntary urination
Most rats and mice urinate when restrained. Urethral catheterisation and cystocentesis are possible in the rabbit.
Rabbit urinalysis
Parameter
Value
Urine volume/24h
20-350 ml/kg average 130mg/kg
SG
1.003-1.036
Average pH
8
Colour
Pale to dark yellow, orange, rust, mildly opaque
with 'sand' calcium carbonate
protein
Negative to trace
Ketones
Negative
Glucose
Negative to trace
Casts
None
WBC
Rare
RBC
Rare
Epithelial cells, bacteria None to rare
Crystals
Common, triple phosphate, calcium monohydrate.
Anhydrous calcium carbonate
Other techniques
Fluid therapy can be administered by jelly cubes for rats), by syringe or dropper if intravenous catheter and drip sets in
rabbits the substance is palatable, or by gavage using and ferrets. Oral administration can be a polyethylene catheter or
commercial gavage achieved via the drinking water, by mixing needle. Rabbits tolerate nasogastric tubes with small
amounts of food (e.g., injected into well. Placement is as for the cat.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)
Sharon Redrobe, BSc (Hons), BVetMed, CertLAS, CertZooMed, MRCVS
Head of Veterinary Services, Bristol Zoo Gardens
Bristol, UK
Speaker Information:
Sharon graduated from London University Royal Vet College in 1994 with distinction in zoo animal medicine and has
practiced 100% with exotic species ever since. She is currently the Head of Veterinary Services, Bristol Zoo Gardens, UK
and is the co-editor of the recent BSAVA Manual of Exotic Pets.