LABORATORY ANIMAL MEDICINE

Class from Feb. 7, 2013

The Gerbil

Gerbils

Small friendly rodents that are native to harsh desert environments.

Meriones unguiculatus= mammal having claws

Originates in Mongolia, southern Siberia, and northern China.

Referred to as Mongolian gerbil.

Anatomic and Physiologic Features

Hind limbs are particularly long, allowing animal to stand nearly upright and jump rather high.

Consume very little water Their low water requirement and highly

concentrated urine makes them a good animal model for studies.

Animal Models

Used in endocrine studies Used extensively in studies of lipid

metabolism due to being prone to developing high serum and hepatic cholesterol levels.

Other research areas include: stroke, behavior, parasitology, epilepsy, radiobiology, auditory, and infectious disease research.

Reproduction

Determine gender by evaluating the ano-genital distance.

Females are polyestrous Monogamous pairs can be left together for life. Males assist in caring for the young. Males can be

kept in cage with female and offspring. Gestation period=25 days.

Behavior

Highly social and inquisitive animals Easy to handle, rarely bite and are nearly odor free.. Do not become aggressive towards cage-mates

unless they are overcrowded. Tend to be most active in the evening, with short

periods of activity during the day. Like to dig and burrow-in native habitat are known to

construct elaborate tunnels including multiple entrances, nesting rooms, and food chambers.

Behavior Cont’d

Frequently sit upright on their hind limbs in an inquisitive stance.

Attract attention by thumping hind limbs to create a drumming sound.

Make an interesting pocket pet because they are very curious and tend to be quite active.

Husbandry, Caging, & Nutrition Solid-bottom shoebox cages with ample soft

bedding. Do not tend to climb, but can jump large

heights. Eliminate a small amount of waste, cleaning is

usually performed once weekly. Temperature and humidity preferences are

similar to other rodents. Rodent chow is appropriate food can

supplement with seeds and clean, fresh vegetables must avoid excess due to being prone to develop obesity.

Husbandry Cont’d

Cedar is not recommended for bedding material because it is irritating to their skin and mucous membranes.

Bedding should be at least 1 in in depth to allow for nest building and burrowing activities.

Restraint and Handling

Restraint techniques are similar to those used for mice.

Should not be picked up by tip of the tail, can slough off.

Identification Methods

Temporary identification: Markers Hair dyes on the hair coat.

Permanent identification: Ear punching Ear tagging Implantation of microchip

Cage cards are used for general identification of groups.

Administration of Medication

Injection Techniques: Subcutaneous Intraperitoneal Intravenous Intramuscular-rarely used due to small muscle

mass. Oral Medications:

Can be mixed into food or water Not the best in water due to low consumption of. Can administer with a feeding needle or

eyedropper

Anesthesia

High metabolic rate-should not undergo prolonged fasting before anesthesia.

Single injection anesthesia techniques are generally used to minimize stress. Ex. Ketamine with either diazepam or xylazine. administered IP.

Inhalant agents include halothane, isoflurane, and sevoflurane. Can be administered by a precision vaporizer using a small

syringe casing as an anesthetic face mask. Can also use an induction chamber.Depth of anesthesia can be determined by using a combination of reflexes such as the righting reflex, pedal withdrawal reflex, and the abdominal pinch reflex. Muscle tone and purposeful movement in response to surgical stimuli may also be used.Ocular position and the palpebral reflex are not reliable indicators in gerbils of anesthetic depth.

Blood Collection Techniques

Preferred site for collection of blood is the retro-orbital sinus.

Technique is similar to that described for the mouse and requires that animal be placed under anesthesia.

Small amounts can be obtained by clipping a toenail or accessing the lateral metatarsal vein.

Diseases

A sick gerbil typically presents with the same signs regardless of the cause.

General signs of illness include weight loss, ocular porphyrin staining, loss of body and coat condition, and lethargy.

Supportive care in the form of warmed fluids given IP or SC and dietary supplements are important.

Unlike the hamster, guinea pig, and rabbit, the gerbil can be treated with a wide variety of antibiotics.

Common Diseases

Like most rodents, gerbils are susceptible to Tyzzer’s disease and Salmonellosis.

Pinworm and tapeworm infections also occur. Dermatitis is commonly seen.

Topical treatments are usually effective. Nasal dermatitis is also referred to as red nose, sore nose,

or stress-induced chromodacryorrhea. May be self-limiting or topical treatments may be

needed. Mechanisms to reduce stress must be addressed.

Euthanasia

Same methods as used for hamsters and mice.

The use of a CO2 chamber-prefilled at least 70%.

Overdose of an inhalant anesthetic Sodium pentobarbital administered IP at

3-4x the anesthetic dose.

Ferrets

Ferrets

Not widely used in biomedical research Classified in the order Mustelidae Which includes: minks and weasels. Domestic ferret scientific name: Mustela

putorius furo which translates into “stinky weasel thief”Very popular as pets- currently rank 3rd behind dogs and cats.

Ferret Terminology

Male ferrets =hobs Female ferrets = jills Young ferrets = kits Spayed female = sprite Neutered male = gib Group of ferrets = business

Unique Features

Have a musky smell Surgical procedures are sometimes

performed to remove the skin glands responsible for the musky secretions.

Secretions are reduced in castrated males

Cannot completely eliminate the unusual odor characteristic of ferrets.

Animal Models

Widely used in early studies of the influenza virus.

Influenza infection in ferrets closely resembles infection in human beings

Used in neuroendocrinology and toxicology research.

Used to study canine distemper Have a strong emesis response and thus are

used to screen compounds for emesis potential. Oropharyngeal anatomy is similar to human

infant’s, ferrets are commonly used for neonatal intubation practice.

Behavior

Easy to house and handle. Friendly, inquisitive animals. Can be housed singly or in groups. Rarely bite, unless frightened or in pain. Females with litters often become

aggressive. Males housed together usually fight

during the breeding season.

Husbandry, Caging, & Nutrition

Can be housed in cages used for cats, dogs, or rabbits that have been modified to prevent animals from escaping.

Feet can be injured in wire cage floors, usually kept in solid bottom cages.

Nest boxes and soft towels can be provided to allow animals to burrow and hide.

Require cooler temps than most other lab animals.

Prone to heat stroke with temps above 80°F

Husbandry cont’d

Ventilation needed to remove fumes and to keep temps from rising.

Commercial ferret chow is available, or cat chow may be fed if protein is at least 30-40%.

Ferrets cannot digest fiber, therefore diets with fiber are less nutritious for them

Food is offered in large, heavy bowls on cage floor.

Water is provided either in large, heavy bowls or hung inside the cage.

Handling and Restraint

Easily restrained by simply picking them up and cradling in the crook of the arm.

For firmer restraint, the loose skin over the back of the neck is grasped and the animal held suspended.

For invasive procedures, the animal can be held with a hand across the shoulders, with the thumb under the chin and fingers placed around the neck and behind the forelimbs. The other hand restrains the hindquarters.

Identification Methods

Permanent ID is usually accomplished with microchips.

Tattoos, ear tags, and ear punches can also be used.

Administration of Medication

Injection Techniques: Sub Q- loose skin on the back over the shoulder

area-in fall and winter months develop a thick layer of fat-will need a longer needle to penetrate.

IM-quadriceps or semi-membranous muscles. IP-lower abdomen IV-cephalic, saphenous, or jugular.

Oral Medications

Administered by a syringe or feeding tube.

No cough reflex-must verify placement by aspiration of a small amount of stomach contents.

Placement of a mouth gag is also needed to ensure animal doesn’t chew on the tube.

Anesthesia

Ketamine-acetylpromazine works well. Given IP due to venipuncture being difficult.

Inhalants can be given to decrease amount of barbiturates needed. Isoflurane, sevoflurane and halothane.

Can be maintained on a mask but should be intubated with a non-cuffed tube.

Non-cuffed tubes are used due to the small size of the larynx and trachea.

Anesthesia Cont’d

Analgesics should be given for all surgical procedures unless there is a scientific justification to avoid their use.

Butorphanol is indicated for mild post-op pain. Buprenorphine works well but causes more

sedation. NSAIDS such as aspirin, flunixin, and carprofen

works well for musculoskeletal pain and inflammation. May cause gastrointestinal upset-use with caution in animals with gastritis and enteritis.

Blood Sample Techniques Small amounts can be obtained from the

lateral saphenous or cephalic veins using a 25 gauge needle and tuberculin syringe.

Superficial caudal tail artery on the ventral side of the tail can be used to obtain blood from a restrained or sedated ferret.- hair clipped and tail warmed in water to dilate vessel.

Jugular vein is most accessible site for larger volumes.

Common Diseases

Susceptible to many of the same diseases as cats and dogs.

Routine vaccination against canine distemper is recommended. Purevax-only approved ferret vaccine.

Vaccine must be a modified live virus of chicken embryo tissue culture origin (CETCO)

Kits should be vaccinated starting at 6 weeks of age, with boosters given every 2-3 weeks. Until 14-16 weeks. Should then receive an annual vaccine.

Diseases Cont’d

Canine Distemper- Serious disease in unvaccinated ferrets, is

usually always fatal. Clinical signs-seen 7-10 days post exposure. Photophobia, mucopurulent oculonasal

discharge, hyperkeratosis of the footpads, a papular rash on the chin and inguinal area, and bronchopneumonia may be seen.

Infected ferrets usually die within a week of the onset of symptoms.

Diseases Cont’d

Rabies Rarely seen Routine vaccination has reduced the

incidence. A killed rabies vaccine labeled for use in

ferrets is available. Should be given at 3 months of age and then yearly.

Note: A modified live rabies vaccine must never be used- has been implicated as causing an active case of rabies in a ferret.

Diseases Cont’d

Human Influenza Humans can transmit influenza infections to

ferrets, and the reverse is true. Caretakers that are sick should wear masks and

gloves when handling ferrets. Within 48 hours of exposure, the ferret becomes

listless, anorexic, and has a sharp rise in rectal temperature.

Sneezing may occur along with mucoserous nasal discharge.

Congestion may be relieved with the use of antihistamines. Cough suppressants and antibiotics may also aid in relief of symptoms.

Diseases Cont’d

Bacterial Diseases Most serious-campylobacteria like organism-

Desulfovibrio-causes proliferative bowel disease. Clinical signs: tenesmus and production of

small frequent bowel movements that often contain frank blood and mucus. Rectal prolapse can occur and can be fatal of left untreated.

Respond well to treatment with chloramphenicol at 50mg/kg twice daily or metronidazole at 20mg/kg twice daily for 2 weeks.

Diseases cont’d

With the exception of coccidia, intestinal parasites are uncommon in ferrets. Diagnosis and treatment of parasite infections

is much the same as for cats and dogs. Miscellaneous Diseases

Gastrointestinal foreign bodies are common in young or bored ferrets. Are curious animals and will chew and ingest any object that they come in contact with. Anorexia and passage of abnormal stools are

common presenting signs.

Diseases Cont’d

High percentages of lymphosarcoma are seen.

Aplastic anemia Common in intact female ferrets Persistent estrus if not bred Prolonged estrogen exposure leads to anemia Clinical signs: lethargy, anorexia, pale mucous

membranes, and petechial hemorrhage. Affected females must have an ovario-

hysterectomy performed. Pet ferrets should be spayed.

Neoplasia

Pancreatic Beta Cell Tumors (Insulinomas) Most common neoplasms of ferrets. 4-5 yr old ferrets most commonly affected. Cancerous cells produce high levels of

insulin that drive the glucose into the cells and hypoglycemia results.

Clinical signs: Episodes of weakness, posterior paresis, ataxia,

head bobbing, weight loss, and vomiting.

Neoplasia Cont’d

Adrenal Tumors Second most common neoplasia in ferrets. Ferrets between 3 and 6 years are most

commonly affected. Clinical signs:

Alopecia, pruritis, swollen vulva in spayed females, prostatic enlargement in males, and increased sexual behavior in neutered ferrets.

Hair loss is most common sign Treatment includes removing the abnormal

adrenal gland. Typically the left gland is 50% more likely to be the one, rather than the right.

Euthanasia

Usually euthanized by administering an overdose of barbiturates by IV or IP injection.

CO2 chamber can be used but animal must be sedated first to prevent undue stress.