Which have more susceptibility to bacteria in general, mice or rats?
Which of the following are true regarding features of rat anatomy:
Mature male rats have higher total leukocyte counts than do females in both lymphocytes and granulocytes, Mammary tissue extends throughout the subcutis along the side and to the neck. They possess serous cells in respiratory epithelium (Serous respiratory cells are unique to rats)
How many lobes does the rat liver have?
4 major lobes, no gallbladder
Cyclic infiltration of basophils is common in the uterus of rats. T or F?
False. Cyclic infiltration of eosinophils is common�cause is unknown.
How many pairs of mammary glands to rats have?
Three pectoral pairs and three inguinal pairs.
How many lung lobes do rats have?
Similar to mice (remember)
Do rats harbor an adenovirus?
Yes, but it has not been characterized, and its status as a pathogen is questionable.
Rat cytomegalovirus infection is common in laboratory rats. T or F?
False. Although it exists in wild populations, and has a tropism similar to murine CMV, it is virtually nonexistent in laboratory reared rats.
What population of rats is susceptible to papovaviral infections? Has this agent been characterized? What tissues are infected? What clinical signs are seen?
A colony of Rowett athymic nude (rnu) rats has been diagnosed with this agent. It has not been fully characterized. Large INIB�s were seen in salivary gland and bronchiolar epithelium and alveolar lining cells. Caused interstitial pneumonia and chronic weight loss in this colony.
What are the three prototype rat parvoviruses?
Kilham�s Rat Virus (RV)
Toolan's H-1 (H-1)
Rat Parvovirus (RPV)
Which rat parvovirus is the most pathogenic under natural conditions?
Kilham�s Rat virus
How can Rat parvovirus be diagnosed?
Negative HAI and positive IFA tests.
How is RV transmitted?
Transplacental, oronasal; is shed in saliva, milk, feces and urine.
What is a common finding in tissues with RV?
Hemorrhage�of the neuropil, lymph nodes, testes. Other lesions include hepatic necrosis. Recovered rats can have peliosis hepatis and nodular hyperplasia.
What agent has been reported to cause mousepox-like lesions in rats? Is it the same virus? What other animals are susceptible?
Turkmenia rodent poxvirus; this is distinct from ectromelia virus, but related to cowpox. Cats and humans are reportedly susceptible.
What kind of virus is sialodacryoadenitis virus (SDAV)?
What are two macroscopic findings associated with acute SDAV infection in rats?
Periglandular edema and red crusting around external nares and eyelids.
What are the histologic changes associated with chronic SDAV infection?
Ductal and acinar squamous metaplasia and mononuclear inflammatory infiltrates.
Are microscopic changes alone sufficient to make a diagnosis of SDAV infection?
What is the typical cause of death with a high morbidity/low mortality agent like SDAV?
Accidental anesthetic deaths (misjudge the severity of pulmonary lesions)
What other respiratory agents have a synergistic effect with SDAV?
Mycoplasma pulmonis and CAR bacillus
What is at the root of behavioral changes and reproductive disorders in rats infected with SDAV?
Depletion of EFG from affected salivary glands.
What are the two major lineages of hantaviruses?
HFRS: hemorrhagic fever and renal syndrome
HPS: hantavirus pulmonary syndrome
Are hantavirus lesions seen in infected rodents? What is the significance of this disease?
Lesions have not been reported in rodents. Human infection is the biggest concern with these viruses.
Pneumonia Virus of Mice (PMV) is what type of virus? Does it infect rats?
Paramyxovirus; you bettcha it does! Results in interstitial pneumonia and perivasculitis, and may be potentiated by mycoplasmosis.
Sendai virus is indigenous to what rodent?
Describe the pathogenesis of Sendai viral infection in rats.
Leukocytic rhinitis that progresses to a descending, necrotizing bronchitis and bronchiolitis in severe cases. Recovered rats have prominent lymphocytic-plasmacytic perivascular and peribronchial cuffing, and interstitial fibrosis.
Name two differential diagnoses for Sendai virus infection in rats.
M. pulmonis, PMV, RCV.
Name two paramyxoviruses that infect rats
Sendai Virus and PMV
What are the acute lesions seen with PMV infection in rats.
Multifocal non-suppurative vasculitis and interstitial pneumonitis with necrosis
Natural disease outbreaks have been reported in rats with mouse encephalomyelitis virus. T or F?
False, although rats have been documented to seroconvert.
Rats possess endogenous retroviruses. T or F?
True. These are of minimal practical significance, however.
What kind of virus causes Infectious Diarrhea of Infant Rats (IDIR)?
At what age are rats resistant to clinical disease with IDIR? How long are they susceptible to viral infection?
2 weeks; all ages can be infected
Which of the following are not associated with IDIR:
Hepatic necrosis, Gastric ulceration
What is the suspected origin of IDIR in rats?
Name two viral agents that infect rats but do not produce clinical disease.
Murine encephalomyelitis virus
Name the three tissues most commonly affected by mycoplasmosis in rats.
Lung, tympanic bulla, and uterus (organism has tropism for epithelial cells of respiratory tract, middle ear and endometrium).
What other pathogens or environmental conditions increase the severity of mycoplasmosis in rats?
Concurrent infection with Sendai virus, RCV, CAR bacillus and other bacterial pathogens; high environmental ammonia levels
What are key histologic features of M. pulmonis infection in rats at all stages of the disease?
Peribronchial and perivascular cuffing with lymphocytes and plasma cells
What are the limitations in diagnosing M. pulmonis infection?
Culturing may fail to detect organism; false positives are seen with ELISA if animals are infected with M. arthritidis; many animals remain seronegative even after 4 months postexposure.
What are the pulmonary changes seen histologically in rats with chronic mycoplasmosis?
Bronchiectasis, bronchopneumonia, emphysema; respiratory epithelial hyperplasia and metaplasia; mucus, leukocytes and cellular debris in airways.
What is the serologic test of choice for mycoplasmosis in rats and is it diagnostic for M. pulmonis? Explain your answer
No, because of cross reactivity with M. arthritidis and rats may be seronegative up to 4 months following exposure.
Campylobacter-like organisms have been isolated from young rats. What is the likely etiologic agent, and what clinical signs have been observed in these rats?
Lawsonia intracellularis is the likely agent. Soft stools/diarrhea have been observed in these rats.
What triad of histopathologic lesions is seen in rats infected with Tyzzer�s disease?
Multifocal necrosis with intralesional bacteria of the heart, liver and ileum
What is the etiologic agent of Tyzzer�s disease?
What is a common gross finding in rats infected with Tyzzer�s disease
Helicobacter infection, with proliferative and ulcerative colitis, has been observed in what type of rats?
Athymic nude rats
How do you diagnose active infection with CAR bacillus?
ID organisms with Warthin Starry stain on tissue sections of nasal turbinates or lung; PCR on oropharyngeal washes.
Describe the characteristic lesions seen with CAR bacillus infection in rats.
Chronic suppurative bronchitis/bronchiolitis; peribronchiolar cuffing with lymphocytes and plasma cells.
From what sites has Haemophilus been cultured in rats?
At necropsy, name three changes commonly seen in rats with acute pseudomoniasis (or any gram negative bacterial septicemia).
Pulmonary edema, splenomegaly, and visceral ecchymoses.
In rats with pseudomoniasis, in what organ are lesions usually most extensive?
Name 3 sources of infection of rats with Pseudomonas aeruginosa.
Water sources (sipper tubes); human skin; implanted surgical devices/indwelling catheters (remember the ERML rats)
Streptobacillus moniliformis causes systemic disease in infected rats. T or F?
False. S. moniliformis is a commensal found in the nasopharynx of rats. Systemic disease is seen in infected mice and humans.
Rat bite fever and Haverhill fever in humans is caused by what 2 organisms?
S. moniliformis and Spirillum muris
What is the causative agent of pseudotuberculosis in rats?
Rats infected with pseudotuberculosis have more severe disease when concurrently infected with viral agents (SDAV, Sendai, Rat virus). T or F?
False, does not alter the course of disease.
What special stains are required to make a diagnosis of pseudotuberculosis? What best describes these lesions? How are gross lesions best described?
Brown and Brenn Gram�s stain or Warthin-Starry silver stain. Focal suppurative to caseous lesions with pathognomonic clusters of bacteria arranged as �Chinese letters�. Grossly, lesions appear as �bulls-eyes�, with central necrosis surrounded by a ring of hemorrhage
What kind of inflammation characterizes lesions in rats with streptococcosis?
What is the intestinal lesion unique to rats with Tyzzer's disease?
Name three tissues primarily affected by Tyzzer's disease in rats.
Ileum, liver, myocardium
Name potential sources of Salmonella if an outbreak occurs in rodent colonies.
Contaminated feed, experimental, humans, wild rodents in facility
Name two sites to culture in rats for the carrier state of salmonellosis
Feces and mesenteric lymph nodes
Describe the characteristic lesions of Salmonella infection
Leukocytic infiltration of the ileum and cecum with focal ulcerations; necrosis of Peyer�s patches and other lymphoid tissues; infectious emboli to spleen, liver, lymph nodes
What potential respiratory pathogen of rats might be acquired from guinea pigs or rabbits?
What is the pathogenesis of disease caused by the above pathogen? What other pathogen does this?
Infects apices of respiratory epithelial cells, impeding clearance functions of the mucociliary apparatus. Disease with B. bronchiseptica usually involves other copathogens as well. Mycoplasma pulmonis also interferes with mucociliary function, resulting in disease.
In rats, what are the most likely routes of transmission of Pasteurella pneumotropica?
Direct contact or fecal contamination (inefficient aerosol transmission).
Pasteurella pneumotropica is a primary pathogen in rats rarely associated with other etiologic agents. T or F?
False, probably an important secondary pathogen to infection with M. pulmonis or Sendai virus. Often can be isolated in rats lacking clinical disease.
What other organ system has clinical disease with P. pneumotropica been reported in?
Mammary glands, resulting in chronic necrotizing mastitis
What is the etiology of streptococcal enteropathy in infant rats?
Enterococcus faecium-durans 2
What is the microscopic lesion in infant rats with streptococcal enteropathy?
Large numbers of gram positive cocci on the surface of normal villi
What is the etiologic agent of pneumococcal infection in rats? What is a possible source of this microbe?
Streptococcus pneumoniae. Humans�serotypes isolated from rats are identical to those obtained from humans.
Is the agent of pneumococcal infection a primary or secondary invader?
Most often considered a secondary pathogen.
What best describes the lesions found in rats with pneumococcal infection (both local and systemic)?
Mucopurulent to fibrinopurulent exudate of affected organs and body cavities.
What is the historical vector of Hemobartonella muris? What type of parasites is H. muris? How can this organism be identified?
Polyplax serrata (sucking louse) is primary vector. H. muris is an extracellular parasite of RBC�s. Splenectomy with reactivation of subclinical infection is the best means of diagnosis (somebody probably has a PCR test now, too).
What leptospiral organism is commonly isolated from (wild) rats?
What is the most common infectious etiology of ulcerative dermatitis in the rat?
What factors contribute to ulcerative dermatitis in rats?
Continued self-trauma (scratching, biting, overgrooming); epidermolytic toxins produced by some strains of S. aureus
Which of the following are true regarding dermatomycosis in the rat:
It is most commonly caused by Trichophyton mentagrophytes. Affected areas of skin are usually raised, erythematous, and dry to moist and pustular in appearance.
Name some predisposing factors to Aspergillus rhinitis in rats.
Contaminated bedding, air quality, immune status of host, concurrent infections
Pneumocystis carinii strains are species-specific. T or F?
What strain of rat has been observed to contract eosinophilic granulomatous pneumonia? What is the etiologic agent?
This condition has been described in Brown Norway rats. An etiologic agent has yet to be isolated and characterized.
Interstitial pneumonitis of unknown etiology has also been described in what strains of rats?
F344, Sprague-Dawley and young Wistar rats. Mice co-housed with rats do not develop lesions.
Name two species of lice of historical importance in laboratory rats.
Polyplax serrata (spined rat louse) and Hoplopleura pacifica (tropical rat louse)�although the latter has not been described in laboratory rats.
What is the most common mite found in laboratory rats?
What mite with a nonselective host range has also been observed in rats?
Ornithonyssus bacoti (tropical rat mite)
What is the name of the ear mange mite in rats? Where on the body is it typically found?
Notoedres muris. Cornified epithelium of ear and other hairless sites.
What organ does Giardia muris and Spironucleus muris reside in?
What are two clinical signs associated with Pneumocystis carinii infection in rats?
Weight loss, cyanosis, and dyspnea
What is the method of choice to confirm Pneumocystis carinii infection?
After rat pinworm eggs are laid, how long is it before they embryonate and become infectious?
A few hours
The anal tape test is used to diagnose which pinworm infection?
Syphacia muris, S. obvelata
Fecal flotation is the test of choice for which pinworm species?
In which organ does infection with Trichosomoides crassicauda occur in rats?
What serve as intermediate hosts for the indirect lifecycles of Hymenolepis nana and H. diminuata?
Grain beetles and fleas (arthropods)
How do rats and mice become infected with Cysticercus fasciolaris?
Ingestion of feed contaminated with cat feces. C. fasciolaris is the larval stage of the cat tapeworm Taenia taeniaformis.
Regarding chronic progressive nephrosis in rats:
There is evidence to suggest that prolactin levels do contribute to the disease.
Describe sequela seen in advanced cases of progressive glomerulonephropathy.
Renal secondary hyperparathyroidism with metastatic mineralization of gastric mucosa, kidneys and arteries
Hydronephrosis in the rat is usually due to blockage of the ureters by calcium phosphate calculi. T or F?
False. Unknown cause, but it is a highly heritable trait.
Bonafide urolithiasis in rats is rare. What must the gross lesions be distinguished from?
Agonally excreted copulatory plugs
Spontaneous myocardial degeneration and fibrosis is seen in what strain of rats?
Atrophy of lumbar and hind limb skeletal muscles, along with paresis or posterior weakness in aged rats is consistent with what condition?
Spontaneous radiculoneuropathy (a degenerative disease of the spinal roots)
Age-related changes in the liver are more striking in rats than in mice. T or F?
False�more prominent in aged mice.
Name tissues commonly affected in rats with polyarteritis nodosa.
Medium size arteries in the mesentery, pancreas and testis.
Ileus in rats due to intraperitoneal injection of chloral hydrate may not be apparent until up to 5 weeks after administration of the drug. T or F?
Nodular masses are present on an aged Sprague-Dawley rat. What is your primary differential?
Which rat strain is most commonly affected with large granular lymphocytic (LGL) leukemia?
What are the gross necropsy findings with LGL leukemia in rats?
Splenomegaly, hepatomegaly, icterus, and pale viscera due to anemia.
Leukemia in rats is commonly associated with retroviruses. T or F?
What is another name for cutaneous lymphoma?
Mycosis fungoides; epidermotropic lymphomas
What is the most common tumor in female Sprague-Dawley rats? Can this tumor occur in male S-D rats?
Mammary fibroadenoma; males will develop these tumors as well.
Mammary tumors in rats are usually benign and have been associated with marked increases in serum prolactin. T or F?
Pituitary gland adenomas are common in what strains of rats? What specific type of adenomas of this gland is most common? What do these tumors tend to secrete?
Sprague-Dawley and Wistar rats. Most of these tumors are chromophobe adenomas, but immunohistochemical techniques are required to differentiate them from acidophil and basophil tumors. Many of these tumors secrete prolactin.
What is the most common tumor type in the rat teste and which strain is most commonly affected?
Interstitial cell tumor; F344
Mesotheliomas are commonly diagnosed in what strain of rat? Where are these tumors thought to arise from?
F344; primary site of tumor is thought to be tunica vaginalis with subsequent implantation to other serosal surfaces.
Where do Zymbal's gland tumors occur in the rat?
In the holocrine gland located at the base of the ear.
Questions from Chapter 2 of Percy and Barthold Pathology of Lab Rodents
Questions from Chapter 2 of Percy and Barthold Pathology of Lab Rodents