Veterinary Laboratory Animal Medicine Boards Study

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gram neg, non-spore forming bacillus;direct contact transmission; high ammonia levels are precipitating factors; stains with Warthin-Starry; clinical signs: chronic respiratory disease in mice (greater significance in rats)

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Cilia Associated Respiratory (CAR) bacillus infection

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discovered in Japanese waltzing mice; gram neg spore forming bacterium; spores infective >1year; propagates only in living cells

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Tyzzer's Disease (Clostridium piliforme)

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Clostridium piliforme infects which species?

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rats, gerbils, hamsters, guinea pigs, rabbits. Reservoir is unknown

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Transmission of Clostridium piliforme

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1. fecal-oral
2. possible natural pre-natal
3. experimental inoculation resulted in intrauterine transmission

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Target organs of Clostridium piliforme

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1. Heart (myocardial degeneration +/- necrosis)
2. Gut (necrosis of mucosal epi; acute inflammation and hemorrhage in ileocecocolic region; intracytoplasmic bundles of bacilli in enterocytes)
3. Liver (periportal coagulative necrosis; intracyto bundles of bacilli in hepatocytes near necrotic foci)

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Clinical signs in mice with Clostridium piliforme
Differentials

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CS: inactivity, diarrhea, death (variable morbidity, high mortality)
DDx: Mousepox, MHV, reoviral hepatitis, Helicobacter infections, Salmonellosis

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Prevention and control of Clostridium piliforme

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good sanitation and husbandry procedures
Infected animals: quarantine, depopulate, decon environment (autoclaving and 1% bleach kills spores), restock animals

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Clostridium piliforme effects on research

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may increase cytokines; mice with immune dysfunction are at increased risk

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Gram pos ubiquitous bacterium; resides in skin, nasopharynx and GIT - inoculation with this bacterium is usually associated with grooming and bite wounds

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Staphylococcus spp

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Clinical signs of Staph. spp in mice

DDx

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suppurative dermatitis, eczematous dermatitis (face, ears, neck, shoulders, forelimbs); ulcerative dermatitis; cellulitis; abscesses
DDx pasteurellosis, streptococcus, corynebacteriosis, pseudomonas, ectoparasites, fight wounds, self-mutilation

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Staph spp. effects on research

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disease and disfigurement -- especially in immune deficient mice
Behavioral dysfunction (scratching and trichotillomania)

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Diagnosis of Staph spp

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PCR of nasopharynx (S. aureus); histo - isolation of gram +, coagulase +, cocci

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Gram pos ubiquitous bacteria with most infections caused by beta-hemolytic organisms in Lancefield's group C

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Streptococcus spp

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2 types of disease caused by Strep spp

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1. ulcerative dermatitis (gangrene) on trunk
2. systemic disease - conjunctivitis, rough hair coat, hyperpnea, somnolescence, cachexia

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Pathology of Strep spp

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absessation, endocarditis, splenomegaly, lymphadenopathy

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gram neg rod; resides in mouse gut; causes hyperplastic typhlocolitis in SCID mice

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Escherichia coli

non-pathogenic in immunocompetent mice

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Pathology of E. Coli

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Gross - segmental thickening of colon or cecum; blood-tinged feces
Histo - mucosal hyperplasia in 1 or more colon segments + inflammation and erosion

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DDx for E. coli in mice

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hyperplastic typhlocolitis (C. rodentium); Helicobacter infection, MHV (enterotropic) in immunodeficient mice

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Gram neg coccobacillus; minor pathogen; opportunistic pathogen; may complicate pneumonias cause by M. pulmonis and Sendai virus

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Pasteurella pneumotropica

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Transmission of Pasteurella pneumotropica

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direct contact
fomites - dirty bedding, equipment, lab coats, etc.

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conjunctivitis, panophthalmitis, dacryoadenitis, urogenital tract (bulbourethral gland); cutaneous lesions; respiratory tract

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Pasteurella pneumotropica loves to cause these problems

Also think Staph, Strep and Corynebacterium

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Clinical disease of P. pneumotropica

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seldom overt clinical disease
URI can manifest as oculonasal discharge, torticollis from otitis media, and/or dyspnea (if mycoplasmal and/or viral resp disease are also present).
Epidemics of conjunctivitis and panophthalmitis have been reported in weanling mice

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Diagnosis of P. pneumotropica

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Primarily by CULTURE
ELISA
PCR

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Treatment of P. pneumotropica

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antibiotics generally unsuccessful
Enrofloxacin in drinking water has been reported to be effective in one study

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Prevention of P. pneumotropica

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barrier housing, microbiology monitoring, rederivation, prophylactic treatment with TMS in drinking water for immunodeficient mice

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gram neg. microaerophilic, spiral-to-curve shaped bacteria, sheathed flagella; common colonizer of GIT

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Helicobacter spp

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Pathology of Helicobacter spp

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colonizes crypts of the lower bowel; can cause liver disease
C57BL/6 resistant to hepatitis
A/JCr, C3H/HeNCr, SLJ/NCr susceptible to hepatitis

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Clinical signs Helicobacter spp

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Asymptomatic in adult immunocompetent mice
liver enzymes may be elevated
H. hepaticus can cause inflammatory bowel disease / rectal prolapse / diarrhea

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Diagnosis of Helicobacter spp

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PCR - does not differential species
IgG ELISA promising
Isolate in feces using filter
Silver stain on histopath

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DDx for Helicobacter spp

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Clostridium piliforme
Salmonella
Citrobacter rodentium (causes colonic hyperplasia which can present as rectal prolapse)

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Prevention / Control Helicobacter

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eradicate via rederivation or antibiotic therapy

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Helicobacter effects on research

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provokes inflammatory response and may interfere with other immunological responses
may be a cofactor in promoting hepatic neoplasia

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Giardia muris

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pear shaped, bilaterally symmetrical organism; resides in upper SI; adheres to microvilli of columnar crypt cells

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Clinical signs associated with Giardia muris

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diarrhea, weight loss, distended abdomens

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Diagnosis of Giardia muris

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detection of trophozoites in the SI or ellipsoidal cysts with 4 nuclei in the feces or histopath
fecal wet preps by characteristic rolling and tumbling movements
DDx - can be confused with Spironucleus muris

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Treatment, prevention, control of Giardia muris

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0.1% dimetronidazole in drinking water X 14 days

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Effects of Giardia muris on research

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potential for severe or lethal infection in immunodeficient mice

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Spironucleus muris

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common flagellate of intestine
inhabits crypts of Lieberkuhn
pear shaped, elongated and bilaterally symmetrical

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Clinical signs associated with Spironucleus muris

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none in immunocompetent adults
dehydration, hunched posture, diarrhea

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Diagnosis of Spironucleus muris

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ID trophozoites in GIT
smaller in size than Giardia muris; no undulating membrane; no sucking disk

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Treatment of Spironucleus muris

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0.1% dimetronidazole in drinking water X 14 days

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Tritrichomonas muris

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nonpathogenic organism
located in cecum, colon and SI

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Coccidosis

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1. Eimeria falciformis - pathogenic; occurs in LI and ONLY found in European mice - Not found in US

2. Klosiella muris - causes renal coccidiosis; RARELY found in laboratory mice

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Mousepox

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Ectromelia virus; dsDNA virus; multiplies in cell cytoplasm

Gross - see "mosaic spleen" due to necrosis and scarring or red and white pulp
Severe hepatocellular necrosis

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Name the 2 types of inclusion bodies produced by Ectromelia virus

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1. A Type (Marchal body)

2. B Type

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A Type (Marchal body)

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one of the 2 types of inclusion bodies produced by Ectromelia virus; well-demarcated and acidophilic; Found primarily in epithelial cells of skin or mucous membranes; may also be found in intestinal mucosa

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B Type inclusion body

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one of the inclusion bodies produced by ectromelia virus; is basophilic; found in all ectromelia-infected cells; difficult to visualize unless intensely stained with hematoxylin, or immunohistochemistry for antigens

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Pathogenesis of Mousepox

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Skin invasion --> multiplication in draining LN and primary viremia --> spleen and liver involved within 3-4 days --> secondary viremia --> focal skin infection

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Mousepox DDx

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Must differentiate between other infectious disease with high morbidity and high mortality:
Tyzzer's
Reo3
Differentiate skin lesions from others: lesions caused by opportunistic or pathogenic bacteria, acariasis, bite wounds

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Mousepox
Prevention and Control

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quarantine infected colonies
depopulate
Disinfection with heat, formalin, sodium hypochlorite or chlorine dioxide
Autoclave materials - but incineration is preferred
Sanitized rooms should be challenged with susceptible sentinels
Rederivation possible
Vaccination by scarifying skin