Rat Pathology Review Flashcards
Transmission of Rat Virus
- Direct (oronasal) contact
- Urine
- feces
- oropharynx secretions (on fomites)
- milk
–(contaminated bedding was able to infect and seroconvert rats even after 5 weeks)
Which rat parvovirus is the only strain to produce natural disease?
Rat virus (RV; Kilham’s rat virus
Features of Rat virus
Parvovirus, ssDNA
Rat Virus causes what clinical signs/issues in pregnant females?
- infertility
- fetal resorption
- abortion
T/F Pups infected w/ Rat virus in-utero will clear the infection
False, they will be persistently infected
Where can Rat Virus be found in persistently infected rats?
Lymphoid tissues, endothelium, vascular muscle, and renal tubule epithelium
Diagnosis of Rat Virus
- Serology
- PCR for DNA in tissue, feces, or environment
Rat Virus Pathogenesis
- Infects cells in S-Phase (dna synthesis) of cell cycle
- Attacks endothelial cells and megakaryocytes (think hemorrhage)
Which phase does Rat Virus infect cells?
S-Phase (DNA synthesis)
How does Rat Virus cause damage?
Attacks endothelial cells and megakaryocytes
Which rats spp. are susceptible to Rat Virus
- Athymic nude rats are more susceptible
- Immunocompetent rats can prevent clinical infection
Gross Lesions of Rat Virus
- Congestion of lymph nodes, loss of body fat, and ***scrotal hemorrhage with fibrinous exudate
- ***Disseinated foci of hemorrhage in cerebrum and cerebellum (both white and gray matter)
- multifocal coagulative necrosis and hemorrhage (infarcts) in testes and epididymis
- ***Cerebellar hypoplasia in neonatal or infant rats
- Icterus 2° to liver damage
Histopathological lesions of Rat Virus
- ***multifocal coagulative necrosis and hemorrhage (infarcts)
- focal to multifocal *hepatocellular necrosis, cerebral and cerebellar necrosis
- Intranuclear inclusions in hepatocytes, Endothelium, bile duct epithelium
- Peliosis hepatitis, nodular hyperplasia, portal scarring are seen in rats that survive disease
- cerebellar hypoplasia
Pathognomonic lesions of Rat Virus
Gross:
- **scrotal hemorrhage with fibrinous exudate
- **Disseinated foci of hemorrhage in cerebrum and cerebellum (both white and gray matter)
- ***Cerebellar hypoplasia
Histo:
- ***multifocal coagulative necrosis and hemorrhage (infarcts)
- focal to multifocal *hepatocellular necrosis, cerebral and cerebellar necrosis
Research impact of Rat Virus
- impact on breeding rats
- Attacks mitotically active cells
- tropism for T-cells can impact immune responses to the experimental treatment or other diseases
Which paroviruses only produce subclinical disease in immunocompetent rats?
- H-1 Virus (Toolan’s H-1 Virus)
- Rat parvovirus
- Rat Minute Virus
Features of Sendai Virus
Respirovirus of paramyxoviridae family (-ssDNA)
Transmission of Sendai Virus
???
Clinical signs of Sendai Virus
- usually subclinical
- CS varies based on immune function of individual strains
- most pulmonary dz affects the bronchioles
- repro issues (reduced litter size, slow growth)
- IgG development coincides w/ clearance of respiratory tract infection and recovery of viral infection
Diagnosis of Sendai Virus
- ***PCR from Trachea or lung samples
- MFI or MFIA serology
- combination of antibody-detection and presence of histopatholgical lesions (can guide dx, but is not pathognomonic)
Histopathological lesions of Sendai Virus
- rhinitis with epithelial necrosis
- Hyperplastic to supperative bronchitis and focal alveolitis
- Lymphoplasmacytic cuffing may persist for months after infection
Susceptible rat strains to Sendai Virus
Brown Norway and LEW rats
Prevention and Control of Sendai Virus
- Regular and periodic serological screening
- If present in colony:
— do not add any antibody-naïve rats
— Cull any preg. And preweanling rats, halt breeding
— virus should be eliminated in 4-8 weeks
Research Impact of Sendai Virus
- Any respiratory research might be affected
- May impact immune responses to research target
Features of Sialodacryoadenitis virus (RCV-ADA)
- Coronavirus
- +ssRNA (tends to mutate more frequently than DNA)
Transmission of Sialodacryoadenitis virus
- Direct contact (nasal secretions, saliva)
- Aerosols
- Fomites
Do different coronaviruses provide protection against others?
No. Reinfection by same strain also possible, but CS less severe
Clinical signs of Sialodacryoadenitis virus
-
** Cervical or intermandibular swelling, sniffling, blepharospasm, epiphora, and nasal and lacrimal discharges
-Chromodacryorrhea (not specific for rat coronavirus) - Repro problems: irregular cycling, small litters, neonatal mortality
- may produce resp. dz in young rats (rhinitis, tracheitis, pneumonia)
Morbidity / mortality of Sialodacryoadenitis virus
high morbidity / low mortality
Diagnosis of Sialodacryoadenitis virus
- MFIA serology
- PCR from affected glands
- Histopath can be helpful in CLINICAL cases
Which strains are susceptible to Sialodacryoadenitis virus?
- Athymic nude rats: develop chronic persistent infections and wasting disease
— significant additive effects in rats prev. exposed to Mycoplasma pulmonis and Filobacterium rodentium (CAR bacillus (see below)
Gross lesions of Sialodacryoadenitis virus
- **Swelling of the submandibular and parotid salivary glands with edema
- Regional lymph node enlargement
- Unilateral or bilateral glaucoma Megaglobus, hyphema, and corneal ulceration
- Chromodacryorrhea
- Rhinitis
Histopath lesions of Sialodacryoadenitis virus
- Salivary and lacrimal glands:
— necrosis of salivary and lacrimal ducts; edema w/ mixed inflammation - Respiratory epithelium:
— loss of cilia and mucosal necrosis; edema, inflammation, fibrinocellular exudates; epithelial hyperplasia (tracheitis, focal bronchitis, and bronchiolitis)
— necrotizing rhinitis w/ mixed inflammation. - ophthalmic lesions:
— Keratitis/KCS; anterior uveitis and Glaucoma w/ retinal degeneration - Reparative stage:
— Squamous metaplasia of salivary, Harderian, and lacrimal glands w/ mixed inflammation; reactive hyperplasia of cervical LNs 7-10 d. post exposure
Describe the Two stages of Sialoacryoadenitis virus
Acute Stage:
Virus infects epithelial cells in salivary and lacrimal glands, causing necrosis of ductular structures spreading to adj. acini and effacement of normal architecture (**mucous salivary glands (sublingual Salivary glands) not affected)
Reparative Stage:
Nonkeratinizing Squamous metaplasia of ductal and acinar structures of salivary and lacrimal glands takes place with reactive hyperplasia of cervical lymph nodes
Prevention of Sialodacryoadenitis virus
Prevention:
- know pathogen status of vendor
- Effective quarantine programs
- keep separate from wild rats
Control of Sialoacryoadenitis virus
Control:
- (6-8wks):
– allow infection to spread so that whole colony seroconverts
– keep infected colony isolated
– suspend breeding and remove preweanlings from colony
OR
– separate seropositive breeders from original colony
– Allow both original and seropositive groups to breed separately
– depop. The original and replace w/ the seropositive group once the seropositive breeders are in late gestation
Research Impacts of Sialodacryoadenitis virus
- Any studies interested in examining tissues from affected sites (period of active infection and 2-3w. of reparative period; ocular lesions may be long-term)
- decreased food intake
- decr. Salivary gland production of EGF, affecting carcinogenicity studies and possibly repro.
- damage to olfactory and vomeronasal organ epithelium -> may affect pheromone detection -> may affect breeding
- unanticipated complications (impairment of nerve regeneration)
Features of Polyomavirus
- small dsDNA polyomavirus
Clinical signs of rat polyomavirus
- ***wasting, nonsuppurative sialoadenitis, dyspnea, and interstitial pneumonia
Rat Strains susceptible to Rat Polyomavirus
- Athymic nude rats susceptible
- Euthymic rats NOT susceptible
Histopathological lesions of rat Polyomavirus
- Large intranuclear inclusions in duct epithelium of salivary glands, less frequently in salivary acini, bronchiolar epithelium, and alveolar lining cells (“relatively diagnostic”)
(“pushes normal DNA to edge”)
Features of Rotavirus
Group B rotavirus, dsRNA, possibly of human origin
Transmission of Rat Rotavirus
-Fecal oral (feces and fomites)
Clinical signs of Rat Rotavirus
-** diarrhea within 24-36 hours
- slowed growth
Gross lesions of rat rotavirus
- milk curd in stomach (indicates presence of appetite)
- watery contents in proximal sm. Intestine
- yellow-brown to green fluid and gas in distal sm. Intestine and lg. intestine
- Erythema and bleeding of the perianal skin
Histopath lesions of rat rotavirus
- **Pathognomonic epithelial syncytia w/ variably present eosinophilic intracytoplasmic inclusions
- Intestinal villus attenuation, necrosis of enterocytes
What is the biggest concern for Cowpox virus
The zoonotic potential
Features of Cowpox virus
- orthopoxvirus, dsDNA
Clinical signs of cowpox virus
CS may vary:
- may be subclinical
-proliferating and necrotizing circular dermal lesions
- Acute pulmonary form w/ high mortality (intranasal inoculation leads to peracute mortality)
Morbidity/mortality of cowpox virus
Enzootic among rodents;
(humans, cattle, felids, and some other mammals susceptible)
High mortality w/ acute pulmonary form
Gross lesions of cowpox virus
Dermal lesions
- Proliferative and necrotizing lesions on libs, tail, tongue, nose, inguinal skin (mostly non-haired skin)
- tail amputation
Pulmonary lesions:
- Focal necrotizing lesions in mucosa
- Pulmonary congestion and edema
Histopath lesions of cowpox virus
- Hyperplasia and necrosis of epithelium
- bronchointerstitial pneumonia, congestion, eema
- large eosinophilic intracytoplasmic inclusion bodies (Guarnieri bodies)
- Lymphoid necrosis
Features of Rat Cytomegalovirus
- Beta-herpesvirus
Clinical signs of rat cytomegalovirus
often subclinical
Pathogenesis of rat cytomegalovirus
- Infects salivary and lacrimal glands
- Cytomegaly w/ intracytoplasmic and intranuclear inclusions in ductal epithelium
- nonsuppurative interstitial inflammation
Rat strains susceptible to Rat Cytomegalovirus
not really seen in lab rats, common in wild rats
Features of Rat Theilovirus
Cardiovirus genus
transmission of Theilovirus
Fecal-oral
Clinical signs of Theilovirus
Often subclinical
Diagnosis of rat Theilovirus
Serology
Pathogenesis of Rat Theilovirus
¬Replicates in small intestinal enterocytes; shed in feces for 4-8 weeks
Rat Strains susceptible to Rat Theilovirus
Nude rats: infection leads to Persistent shedding, virus found in intestines and elsewhere
Gross and histopath changes of Rat Theilovirus
No gross or histopath changes
Control/prevention of Rat Theilovirus
Control via test and cull
Features of Pneumonia Virus of Mice (PVM)
- Pneumovirus of paramyxoviridae family
Clinical signs of Pneumonia Virus of Mice
subclinical infection
Pathogenesis/concerns of Pneumonia Virus of Mice
** possibly a significant co-pathogen w/ Mycoplasma pulmonis
What species does pneumonia virus of mice infect?
Infects mice, rats, hamsters, gerbils, guinea pigs, and rabbits
Histopath lesions of Pneumonia Virus of Mice
Vasculitis, interstitial pneumonitis w/ necrosis
Primary concern of Hantavirus
ZOONOTIC
What are the human diseases associated with hantavirus
(Seoul Hantavirus causes hemorrhagic fever w/ renal syndrome in humans); (hantavirus pulmonary syndrome in Florida)
Features of hantavirus
Bunyaviridae family
Clinical signs of Hantavirus
Chronic, subclinical infection
T/F Rodents are not natural reservoirs for Hantavirus
False, they are
Transmission of Hantavirus of Rats
virus shed in feces and urine
Does Rat Adenovirus cause clinical disease
no
Histopath lesions associated with Rat Adenovirus
Inclusions can be seen in enterocytes, typically incidental findings
Features of Filobacterium Rodentium
(formerly Cilia-Associated Respiratory (CAR) Bacillus)
- filamentous, G- argyophilic
Transmission of Filobacterium Rodentium
- direct (oronasal) contact, usually in young (neonatal) rats
Severity and Clinical signs of Filobacterium Rodentium
Severity variable
(may be clinical, subclin., or only clinical if copathogen present)
CS:
- Oculonasal discharge, increased resp. effort, hunched posture, anorexia w/ weight loss
Diagnosis of Filobacterium Rodentium
- PCR from nasopharyngeal or tracheal swabs
- Serology (ELISA, MFIA, IFA)
- ID of org. w/ silver stains (like Warthin-Starry staining)
Pathogenesis of Filobacterium rodentium
- Colonizes cilia of airway epithelium, starting w/ upper airways and spreading to the lungs
***bacteria line the apex of the respiratory epithelium, interspersed between cilia
Which rat strains are susceptible to Filobacterium rodentium
all strains
Gross lesions of Filobacterium Rodentium
- Purulent discharge in upper and lower airways
- Lungs fail to collapse w/ release of pressure
- May have cranioventral consolidation
- Lungs may have mottled red to gray-tan appearance w/ dilated and mucus-filled airways
Histopath lesions of Filobacterium rodentium
- Chronic suppurative bronchitis and bronchiolitis w/ bronchiectasis
- Lymphocytes and plasma cells surrounding airways (peribronchiolar cuffing)
- Marked leukocytic infiltration in the lamina propria of affected airways
Control of Filobacterium rodentium
Control:
- evaluate risk of wild rodent exposure
- Test and cull and/or depop-repop
Research impact of Filobacterium rodentium
- Cannot be used for resp. research, even if asymptomatic
- clinically sick animals are generally unfit for research
- potential complications w/ inflammation, ciliary function, and immune modulation
Features of Mycoplasma pulmonis
- (G-); very small
- Lacks a cell wall entirely
transmission of Mycoplasma pulmonis
- direct contact
- Aerosolization
- Transplacental
Which is more likely to present clinical signs: Filobacterium rodentium or Mycoplasma pulmonis
Mycoplasma pulmonis
Clinical signs of Mycoplasma pulmonis
CS:
- Oculonasal discharge, increased resp. effort, hunched posture, anorexia, weight loss
- Repro. Deficits
Potential for infections beyond the lungs (due to affinity for ciliated cells)
- resp. epithelium -> pneumonia
- middle ear -> otitis media
- Uterus -> endometritis
- Synovium -> arthrosynovitis (less common)
Diagnosis of Mycoplasma pulmonis
- PCR on nasopharyngeal or tracheal swab, lung tissue, exudate
- Culture
- IHC
- Serology less reliable since seroconversion takes a long time, and cross-reacts w/ other Mycoplasma spp.
Pathogenesis of Mycoplasma pulmonis
**Strong predilection for tissues w/ ciliated epithelium
Colonies cilia of airway epithelium, starting w/ upper airways and spreading to lungs (may take up to 6 mos.)
Colonize the apex of the resp. epithelium, effacing the surface with loss of cilia
Susceptible strains of Mycoplasma pulmonis
All strains
Gross lesions of Mycoplasma pulmonis
Lungs:
- purulent material within trachea and bronchi; red to gray consolidation of the lungs with *** asymmetrical cranioventral enlargement and distended/ectatic bronchi
Ears
- purulent material within tympanic bullae
Repro tract
- clear to purulent exudate within uterine horns, ovarian bursae, and oviducts
Synovium
- Swelling of tibiotarsal joints
Histopath lesions of Mycoplasma pulmonis
Lungs:
- ***loss and flattening of cilia, squamous metaplasia
- bronchial and bronchiolar neutrophilic exudate (purulent material in other organs)
- ***Bronchiectasis and bronchiolectasis (ciliostasis -> unable to clear mucus or inflammatory exudate -> pressure expansion of airways -> bronchiectasis and bronchiolectasis
(essentially, disruption of the ciliary elevator) - ***Lymphoid hyperplasia
– intact organisms and cell membranes are superantigens and B-cell mitogens, resulting in marked peribronchiolar lymphocytic infiltration
Control of Mycoplasma pulmonis
Control:
- reputable vendors
- quarantine and screening
Prevent exposure to wild rodents
- Depop and repop
Research Impact of Mycoplasma Pulmonis
- Impact on animal health and number of possibly affected organ systems means that infected animals are unfit for research
What is the Etiology of Chronic Respiratory Disease of Rats
Etiology:
- Mycoplasma pulmonis (the major causative agent)
- CAR Bacillus (Filobacterium rodentium)
- Sendai virus
- Rat Coronavirus (Sialodenacryoadentitis virus)
- Ammonia exposure above 25ppm
Features of Corynebacterium kutscheri
- (G+); short rod
Transmission of Corynebacterium kutscheri
- Predominantly fecal-oral
- Direct contact
Clinical signs of Corynebacterium kutscheri
Frequently subclinical to inapparent (clinical dz and mortality usually ass. w/ underlying immunosuppression, nutritional deficits, etc.)
CS:
- weight loss
- resp. distress
- ruffled hair coat
- death in a few days after onset of signs
Diagnosis of Corynebacterium kutscheri
PCR or culture of
- cervical LNs, oropharynx, nasopharynx, middle ears, preputial glands, feces
Histopath w/
- Gram, Warthin-Starry, or Giemsa stains
(characteristic appearance of bacteria arranged in acute angles; referred to in textbooks as “Chinese letter-like” arrangement” (well that’s messed up)
Pathogenesis of Corynebacterium kutscheri
Carried in oropharynx and Regional LNs for weeks -> hematogenous spread to many organs
Strains / spp. susceptible to Corynebacterium kutscheri
Can infect mice, rats, and guinea pigs
Any age can be affected
Immunocompromised rats most at risk of infection
Gross lesions of Corynebacterium kutscheri
- Red crusty lesions around eyes and nares
- possibly mucopurulent exudate around nose
- raised pale tan to white foci on lungs and possibly other organs
What is the causative agent of pseduotuberculosis
Corynebacterium kutscheri
Histo lesions of corynebacterium kutscheri
- Abcesses (nodule-like lesions w/ suppurative inflammation and necrosis) in lungs an dother organs
– predominantly lungs in rats (liver, kidneys, and lungs in mice) - Bacteria form large colonies within lesions
- Inflammation often centered around blood vessels (embolic pattern of disease (e.g., embolic glomerulonephritis)
control of corynebacterium kutscheri
Control:
- depop. And repop
- Sterilization
Research impact of corynebacterium kutscheri
- impact on animal health and number of possibly affected organ systems means that infected animals are unfit for research
Features of Clostridium piliforme
- (G-); filamentous rod
(other clostridium spp. Are often G+)
Transmission of Clostridium piliforme
Forms spores (can survive in the environment for up to 1 year)
- ingestion of spores from the environment
- fecal oral
Morbidity / mortality of Clostridium piliforme
(Tyzzer’s disease)
Low morb. / Hight mort.
(often acute death w/o any clinical signs)
Diagnosis of Clostridium piliforme
- (G-); stains positively on silver, PAS, or Giemsa stains
- Serology: risk of false positives, so interpret results w/ histopath
- PCR on cecal contents or feces (less reliable since immunocompetent animals will clear the bacteria)
Rats strains susceptible to Clostridium piliforme
Affects many animal spp.
- spp.-specific variations in lesions
- Young rats in the postweaning period more susceptible to dz
gross lesions of Clostridium piliforme
- Small white foci throughout the liver and heart
- ***Megaloileitis: flaccid and dilated ileum filled w/ hemorrhage
Histo lesions of Clostridium piliforme
- Multifocal random necrotizing hepatitis
- necrotizing myocarditis
- necrohemorrhagic transmural ileitis w/ flaccid and dilated ileum (megaloileitis)
- bacteria are arranged in thin bundles within cytoplasm of cells near areas of necrosis
pathognomonic lesions of Clostridium piliforme
- Megaloileitis: flaccid and dilated ileum filled w/ hemorrhage
Control and prev. of Clostridium piliforme
Control and prev.
- keep facilities clean
- prevent exposure to wild animals (wide range of hosts and persistence of spores)
Research impact of Clostridium piliforme
- Clinically sick animals
- sudden death of animals, esp. young animals
Research impact of Streptococcus pneumoniae
- Impact on animal health and number of possibly affected organ systems means that infected animals are unfit for research
Control of Streptococcus pneumoniae
Control:
- Reputable vendors
- Quarantine and screening
- Depop if indicated
Histo lesions of Streptococcus pneumoniae
- Fibrinopurulent (fibrin, degenerate neutrophils), polyserositis, and bronchopneumonia
- embolic neutrophilic inflammation in liver and other organs
Gross lesions of Streptococcus pneumoniae
-Fibrinous and purulent pleuritis, pericarditis, and pneumonia (possibly peritonitis, periorchitis, and meningitis
- Fluid in trachea
- Mucopurulent exudate in nasal passage and sometimes tympanic bullae
- Lung consolidation
Rat strains/ages susceptible to Streptococcus pneumoniae
Young rats may develop disease
Diagnosis of Streptococcus pneumoniae
- Nasopharyngeal culture via blood agar place, optochin inhibition test
- PCR
Tests are best w/ histopath to corroborate, since there are nonpathogenic strains