Laboratory Animal Medicine

1. Laboratory Animal Medicine Class from Feb. 7, 2013

2. The Gerbil

3. Gerbils • Small friendly rodents that are native to harsh desert environments. • Merionesunguiculatus= mammal having claws • Originates in Mongolia, southern Siberia, and northern China. • Referred to as Mongolian gerbil.

4. 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.

5. 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.

6. 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.

7. 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 tunnelsincluding multiple entrances, nesting rooms, and food chambers.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. Ferrets

20. Ferrets • Not widely used in biomedical research • Classified in the order Mustelidae • Which includes: minks and weasels. • Domestic ferret scientific name: Mustela putoriusfuro which translates into “stinky weasel thief” Very popular as pets- currently rank 3rd behind dogs and cats.

21. Ferret Terminology • Male ferrets =hobs • Female ferrets = jills • Young ferrets = kits • Spayed female = sprite • Neutered male = gib • Group of ferrets = business

22. 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.

23. 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.

24. 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.

25. 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

26. 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.

27. 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.

28. Identification Methods • Permanent ID is usually accomplished with microchips. • Tattoos, ear tags, and ear punches can also be used.

29. 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.

30. 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.

31. 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.

32. 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.

33. 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.

34. 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.

35. Diseases Cont’d • Canine Distemper- • Serious disease in unvaccinated ferrets, is usually always fatal. • Clinical signs-seen 7-10 days post exposure. • Photophobia, mucopurulentoculonasal 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.

36. 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.

37. 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.

38. 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.

39. 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.

40. 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.

41. 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.

42. 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.

43. 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.