Myomorph rodents Flashcards
Which rodent species are born altricial and hairless?
Rats, mice, hamsters, and gerbils
What is the gestation length in rats?
21 to 23 days
At what age should male rats be separated from female to prevent pregnancy?
5 weeks of age
What is the gestation length in mice?
19-21 days
What is the gestation length in hamsters?
15-20 days depending on species
What is the gestation length in gerbils?
24-27 days
Which hamster species are solitary and should be housed alone?
Syrian and Chinese hamsters (remainder of hamsters, as well as gerbils should be housed together)
Newly weaned rats present with anorexia, emaciation, mucoid/bloody diarrhea and sudden death. On PM, hepatitis and myocardial lesions are noted. What is the most likely diagnosis?
A. Enterococcal/Streptococcal enteropathy
B. Rat rotavirus
C. Tyzzer’s disease (Clostridium piliforme)
C is correct
A causes diarrhea/death in nursing rat pups.
B is the cause of diarrhea in infant rats (<2 wks of age), but rare mortality; rare/unlikely to be seen in pet rats
What should pinworms in rats be treated with?
Fenbendazole (topical selamectin ineffective)
Which is not a route of spread for salmonellosis among mice?
A. Wild rodents
B. Contamination of food/water
C. Placental transmission
C (as far as I know!)
What is the cause of necrotizing enteritis in weaned mice (and paraplegia/death in 2-3 wk old mice)?
Clostridium perfringens
What is the cause of transmissible murine colonic hyperplasia and what are the clinical signs?
Citrobacter rodentium; Diarrhea, rectal prolapse, death in nursing/recently weaned mice
What is the difference in presentation for mouse rotavirus vs. intestinal coronavirus (mouse hepatitis)?
Mice with rota keep nursing and recover; intestinal coronavirus often leads to death
What is the causative agent of proliferative ileitis (or wet tail - although term used broadly by laypeople)? What age is most commonly affected?
Lawsonia intracellularis; weaning (3 wks) to 10 wks of age
How is proliferative ileitis in hamsters treated? and what is the prognosis?
Chloramphenicol or TMS, enro, tetracycline; guarded - often leads to death
How is Tyzzer’s treated in gerbils? What are clinical signs?
Tetracycline or chloramphenicol; lethargy, diarrhea, death, weight loss if chronic
What parasite can cause urolithiasis and pyelitis in rats 8-12 weeks of age?
Bladder threadworms - Trichomoides crassicauda
Pneumonia secondary to what pathogen is more severe in juvenile rats (vs increasing in severity with age)?
A. Mycoplasma pulmonis
B. Streptococcus pneumoniae
C. Bordatella bronchiseptica
B (Mycoplasma severity worsens w/age)
What is the cause of ringtail and what age/species is it observed in?
Annular constrictions on tail, potentially related to humidity levels; young, unweaned rats and occasionally mice; uncommon in pet rats
What organism can be asymptomatic or cause anorexia, rough coat, oculonasal discharge, cutaneous ulceration, and arthritis in nursing and weanling mice?
Corynebacterium kutscheri (C. bovis can cause derm lesions); Can be fatal in nursing pups, but weanlings tend to resolve
What can cause lymphoma affecting skin, lymph nodes, and abdominal organs throughout a previously unexposed hamster colony?
Hamster polyomavirus
What condition causes conjunctivitis in unweaned rats and cervical salivary gland swelling in weaned and adult rats?
Sialodacryoadenitis (caused by a coronavirus)
What two types of neoplasia can be reduced as a result of ovariectomy at <90 days of age in rats?
Subcutaneous (mammary) and pituitary tumors
What are the benefits of flank ovariectomy in rats?
Smaller incisions, decreased risk of evisceration and less pain; also potentially less complications (but not statistically significant)
What is the primary benefit to neutering male rats?
Decreased aggression (more effective if done young), also can prevent development of urethral plugs
What is the most common spontaneous tumor in mice and how does it behave?
Mammary tumors, usually malignant and often viral induced, invasive, highly metastatic and carry poor prognosis
What are the top 2 systems affected by neoplasia in hamsters?
Integumentary and hematopoietic tumors
What is cabergoline’s MOA and when is it used?
Prolactin inhibitor; suppresses pituitary prolactin secretion; used w/pituitary adenomas in rats - may help reduce risk of mammary neoplasia development
What population is chronic progressive nephrosis/nephropathy more frequently diagnosed in?
Aged male rats (also generally more severe in males)
What is the most common cause of posterior weakness or tail dragging in rats?
Radiculoneuropathy
How can radiculoneuropathy in rats be treated?
B complex SQ/IM injection and NSAIDs appear to decrease symptoms
What is the likely underlying cause of mammary tumors in mice?
Mouse mammary tumor virus
What increases the risk of atrial thrombosis in male Syrian hamsters?
Castration
What is the most common tumor type in Syrian hamsters?
Adrenocortical neoplasia
What is the most frequently diagnosed neoplasm of the hematopoietic system in Syrian hamsters?
Lymphoma
A male hamster with bilateral symmetric alopecia of the flanks and lateral thighs, thin/hyperpigmented skin, PU/PD and polyphagia likely has what diagnosis and how can it be treated?
Hyperadrenocorticism. No successful tx to date.
What is the most common signalment of rats presenting with mammary neoplasia?
Females, 1+ yrs of age, typically intact
Which rodent species is prone to diabetic cataracts?
Chinese hamsters (Cricetulus griseus)
Which rodent species may develop idiopathic glaucoma?
Djungarian hamsters (Phodopus songurus cambelli)
Which rodent species is at higher risk for traumatic ocular injury if not housed alone?
Syrian hamsters (Mesocrecitus auratus)
What rodent species are prone to epilepsy and how should it be treated?
Gerbils (young, severity often diminishes w/time)
Continued anticonvulsant therapy not indicated
What is the difference between hibernation and torpor?
Torpor is a state of physical/mental dormancy lasting <24 hour; Hibernation is a prolonged state of torpor
List 4 triggers for torpor in hamsters:
- Shorter photoperiod
- Low ambient temp (<46*F)
- Inadequate food
- Gonadectomy
What species have cheek pouches?
Hamsters only!
How common are ovarian cysts in gerbils?
Very common - 47% of females >400 days
What signalment of rodent most likely to present w/ cushing’s disease?
Hamsters >1.5 years of age
What is the most likely underlying cause of lymphoma in a young hamster (especially if littermates affected)?
Hamster polyomavirus infection
What respiratory disease common in aged mice often occurs after other pulmonary diseases and causes interstitial to alveolar macrophages and crystals?
Eosinophilic crystalline pneumonia (ECP)
What is the gross appearance of rat kidneys affected by chronic progressive nephropathy?
Shrunken/pale kidneys, tan to pale brown with a pitted to cystic surface
What makes rats particularly susceptible to infectious agents spread between the heart, pulmonary veins and lungs?
Cardiac striated muscle extends to lung tissue
What are the 3 tear-producing glands in rats and mice?
Harderian, intraorbital, extraorbital
