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Mouse Disease and Your
Research
The health status of research mice has improved steadily over the past decade. Laboratory rodents are raised in extremely clean environments with relatively little antigenic stimulation. Some experts argue that animals that are kept in this sort of situation cannot really be considered normal. The question 'When is clean, too clean?' is discussed at meetings of laboratory animal veterinarians. meeting.
However, there are diseases that must be kept out of research facilities. These are diseases that can either infect humans (zoonosis) or cause severe infections in (immune competent) mice. Aside from these diseases there are numerous others that can affect research outcomes or cause disease in immune incompetent animals. It is these organsims that will be discussed below.
The information provided is an basic outline only. Links will be provided to more detailed desciptions.
Epizootic Diarrhea of Infant Mice (EDIM)
Type of virus
- dsRNA, Rotavirus species A
- Non-enveloped, environmentally stable
Other Rotaviruses
Transmission
- Direct contact, airborne dust, fomites
Disease in Immune Competent Mice
- May be subclinical
- Signs are generally limited to pups under two weeks of age
- Watery stools, lethargy, distended abdomens, rectal fecal impaction leading to death
Disease in Immune Incompetent Mice
- As above but more severe clinically
Affects on Research
- Altered results in dietary and nutritional studies
- Increased susceptibility to co-pathogens
- Alterations in gastrointestinal physiology
Eradication
- Cull and replace
- Caesarian rederivation
- Embryo transfer
Additional Information
Helicobacter
Organism
- A Genus of bacteria
- Gram negative
- Have a typical helix shape
- Microaerophilic
- Survive acid environments
Species Associated with Mice
- H. bilis
- H. hepaticus
- H. muridarum
- H. rappini
- H. rodentium
- H. typhlonicus
- plus numerous others
Transmission
Disease in Immune Competent Mice
- H. hepaticus can cause acute focal, nonsuppurative, necrotizing hepatitis which progresses to chronic, active hepatitis. Mouse strains A/JCr, B6C3F1, BALB/cAnCr, C3H/HeNCr, SJL/NCr, and SCID/NCr have been shown to develop hepatitis due to H. hepaticus infection, and infected A/JCr and male B6C3F1 mice show increased incidence of hepatocellular neoplasms.
- H. bilis can be found in the bile, liver, and intestines of mice. Infection is associated with chronic hepatitis.
Disease in Immune Incompetent Mice
- Members of this genus that do not usually associated with disease can cause inflammatory bowel disease in immune incompetent animals.
Additional Information
Mouse Hepatitis Virus (MHV)
Type of virus
- Corona virus
- ssRNA
- 25 strains reported, wide variety of pathogenicity and trophism for different organs
Other Corona Viruses
- Sialodacryoadentitis is rats
- SARS in humans
Transmission
- aerosol, fecal-oral, direct contact, fomites
Disease in Immune Competent Mice
- Adults are usually asymptomatic carriers.
- Neonates may develop diarrhea or increased neonatal mortality.
- Disease will burn out with cessation of breeding.
Disease in Immune Incompetent Mice
- May be subclinical, increased neonatal mortality
- Diarrhea, wasting, death
Affects on Researach
- Immune competent
- Initial immune stimulation followed by immunodepression
- Enhanced phagocytic activity of macrophages
- Necrotic changes in various organs
- Immune Incompetent
- Altered hepatic activity
- Impaired liver regeneration
- Increased production of IL-12 and IFN
- Decreased incidence of diabetes in NOD mice
Eradication
- 'Burn - out' - cease all breeding for at least 8 weeks
- Cull and replace
- Caesarian rederivation or embryo transfer
Additional Information
Mouse Norovirus
Type of Virus
- Calici virus
- Non-enveloped RNA, stable
- At least 4 strains
Other Noroviruses
- Norwalk Virus - Cruise ship gastroenteritis
Transmission
Disease in Immune Competent Mice
- None
- Causes persistent infection
Disease in Immune Incompetent Mice
- None except in mice severely deficient in both innate and acquired immunity ie RAG/STAT -/-
- Encephalitis, pneumonia, meningitis
Affects on Research
- Virus replicates in macrophages.
- Resistance requires interferon-dependant systems
- Could impact research into either of these areas
Eradication
- Cull and replace
- Embryo transfer
- Caesarian rederivation
Additional Information
Parvovirus
Type of Virus
- Parvo virus
- Single stranded DNA
- Very stable
Parvoviruses of Note
- Mouse Minute Virus (MMV)
- Mouse Parvovirus
Transmission
- direct contact with feces or urine
- fomites
- respiratory?
Disease in Immune Competent Mice
- None obvious in natural infections
- MPV causes persistent infection
Disease in Immune Incompetent Mice
Affects on Research
- Immune modulation both in vivo and in vitro
- Responses that depend on cellular proliferation
Eradication
- Cull and replace
- Embryo transfer
- Caesarian rederivation
- Environmental decontamination
Additional Information
Pinworms
Type of Organisms
- Gastrointestinal nematodes
- Syphacia obvelata
- Aspiculuris tetraptera
Location of Parasite
Location of Eggs
- Syphacia - perianal
- Aspiculuris - released in feces
- Eggs are very stable
Transmission
- Ingestion
- Syphacia eggs may aerosolize
Disease in Mice
- Usually none evident
- In severe infections and immune compromized animals may see rectal prolapse
Affects on Research
- May complicate gastrointestinal research. (see below)
Eradication
- Treatment with paracitacide, cage bonnets to prevent aerosolization.
- Cull and replace
- Caesarian rederivation
- Environmental decontamination - this is very difficult due to the nature of the ova - disinfectants do not work - physical removal or heat sterilization.
Additional Information
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