The lab is about to bring in a new batch of mice. What are the common infectious diseases in mice?

Common infectious diseases in laboratory mice mainly include bacterial/viral diseases and parasitic infections. Let's discuss them in detail.

 

Bacterial/Viral Infectious Diseases
 

1. Mouse Hepatitis Virus (MHV)
 

MHV is an RNA virus primarily transmitted via the fecal-oral route, but also airborne. Infection can lead to hepatitis, encephalitis, and pneumonia in mice.

● Symptoms: Initial lethargy, rough coat, anorexia; may progress to jaundice, ascites; severe cases may show neurological symptoms like hindlimb weakness and convulsions.

● Solutions: Isolate infected colonies, house separately; wipe cages and work surfaces with 1% potassium peroxymonosulfate solution; fumigate rooms with formaldehyde.
 

2. Sendai Virus

Primarily transmitted via airborne routes, infection causes respiratory symptoms in mice.

● Symptoms: Prominent respiratory symptoms like dyspnea, tracheal rales; rough coat; reduced activity.

● Solutions: Enhance quarantine, isolate newly introduced animals for observation; house new arrivals separately for at least 4 weeks.
 

3. Mousepox Virus (MPV)

Primarily transmitted via skin contact, infection causes skin lesions. Strains like A, DBA, and C3H are susceptible, while C57BL shows strong resistance and often becomes a latent carrier, making it a primary potential source.

● Symptoms: Acute infection can cause facial edema, skin ulceration, limb necrosis, and even death.

● Solutions: Strict isolation; cull infected individuals; thoroughly disinfect the environment using 5% hot alkali solution and formaldehyde fumigation.
 

 

(Image: Laboratory Animal Medicine)

4. Pneumonia Virus of Mice (PVM)
 

Infected mice and latent carriers are major sources; transmitted via the respiratory route, causing respiratory symptoms.

● Symptoms: Reduced appetite, unkempt fur, emaciation, hunched posture, dyspnea, cyanosis of ears and tail.

● Solutions: Enhance quarantine; isolate newly introduced animals for observation; house new arrivals separately for at least 4 weeks.
 

5. Salmonella (STM)

Salmonella is a Gram-negative bacillus, primarily transmitted via contaminated feed, water, excreta, and cages. Young mice are more susceptible than adults.

● Symptoms: Acute septicemia death; subacute and chronic infections may show piloerection, diarrhea, wasting diseases; latent carriers may develop symptoms under stress from transport or experiments.

● Solutions: Regular cleaning and disinfection; wipe cages with chlorine-based disinfectants. Reduce stocking density to minimize cross-infection.
 

6. Murine Mycoplasmosis

Primarily transmitted via airborne routes, causing respiratory symptoms.

● Symptoms: Hunched posture, rough fur, weight loss, tachypnea, distinct nasal sounds.

● Solutions: Regular cleaning and disinfection; wipe cages with chlorine-based disinfectants. Reduce stocking density to minimize cross-infection.
 

7. Staphylococcal Infection

Primarily transmitted via skin contact, causing skin lesions.

● Symptoms: Dermatitis, suppurative lesions, especially facial abscesses common in nude mice.

● Solutions: Maintain environmental hygiene; clean and disinfect regularly. Avoid skin injuries; treat wounds promptly. Cull infected individuals promptly to prevent disease spread.
 

8. Pseudomonas aeruginosa

A conditionally pathogenic, Gram-negative, short bacillus. Contaminated water, feed, bedding, carrier animals, or humans are primary sources. Transmission is mainly via contact and airborne routes.

● Symptoms: Otitis media, otitis interna leading to torticollis or circling; can also cause alopecia, ulcers, respiratory infections, or even sepsis.

● Solutions: Disinfect cages and work surfaces with disinfectants like benzalkonium chloride or chlorine-based agents. Regularly replace water, feed, and bedding. Treat infected mice with drugs like polymyxin B, ceftazidime, or imipenem.
 

9. Epidemic Diarrhea of Infant Mice

Caused by mouse rotavirus. Mainly transmitted via the digestive and respiratory tracts; high incidence in mice under 15 days old.

● Symptoms: Diarrhea, dehydration, skin wrinkling, growth retardation; dried feces in later stages can cause rectal impaction and death.

● Solutions: Isolate affected infant mice from healthy ones; disinfect with chlorine-based agents. Supplement affected pups with electrolyte solutions to prevent dehydration; use antibiotics to prevent secondary infections.

 

Parasitic Diseases
 

1. Pinworms

● Symptoms: Intestinal inflammation, diarrhea.

● Solutions: Deworming with drugs like ivermectin or praziquantel.

2. Tapeworms

● Symptoms: Intestinal inflammation, diarrhea.

● Solutions: Deworming with drugs like praziquantel.

3. Fur Mites

● Symptoms: Skin itching, rough fur.

● Solutions: Use anti-mite powders or washes.

4. Fleas

● Symptoms: Skin itching, rough fur.

● Solutions: Deworming with flea powders or washes.

 

References:

[1] Laboratory Animal Medicine [M] Third Edition 2015

[2] China Encyclopedia Online Entry

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