Microbiology 501

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Microbiology 501

• Mice and Rats
• Disease Surveillance and Prevention
• Common Diseases

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Common Diseases of Laboratory Animals

• Prevention of common diseases in laboratory
  colonies is done by
• Purchasing of animals from commercial vendors
  with stringent health surveillance programs.
• Implementing strict quarantine procedures.
• Establishing an in-house disease surveillance
  program.

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Rodent Health Surveillance

• Systematic laboratory testing to monitor for
  sub-clinical infections in animal populations.
• Crucially important in rodent disease prevention
• Transplantable tumors

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Typical Serological Screen

• Sendai virus
• Pneumonia virus of mice
• Mouse hepatitis virus
• Minute virus of mice
• Theilers (GDVII) encephalomyelitis virus
• Reo 3 virus
• Epidemic diarrhea of infant mice (EDIM)
• Mycoplasma pulmonis
• Mouse adenovirus

• Polyoma virus
• K virus
• Lymphocytic choriomengitis virus (LCM)
• Hanta virus
• Ectromelia (Mouse pox)
• Encephalitozoon cuniculi
• CARB
• Mouse parvovirus
• Mouse Cytomegalovirus (MCMV)
• Mouse Thymic Virus

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Typical Bacteriological Screen

• Bordetella bronchiseptica
• Citrobacter freundii
• Corynebacterium kutscheri
• Mycoplasma pulmonis
• Salmonella spp.
• Strep. Moniliformis
• Helicobacter spp.
• Klebsiella pneumoniae

• Klebsiella oxytoca
• Pasteurella pneumotropica
• Pseudomonas aeruginosa
• Staph. Aureus
• Strep. Pneumoniae
• Beta Strep group B
• Beta Strep group G
• Beta Strep spp.

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Typical Parasitological Screen

• Ectoparasites
• Endoparasites
• Enteric Protozoa

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Sampling strategies

• Purpose detect at least one animal with each of
  the infections present in the population.
• Not interested in determining prevalence of
  disease

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Sampling Strategy

• Sample size critical
• Determined mathematically
• Assumptions
• Rate of infection
• Randomness of sampling

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Sentinel animals

• Animals placed in colonies
• Exposed to dirty bedding from all animals in
  colony
• Immunocompetent animals
• Respiratory transmission?
• Parasites?
• Frequency?

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Testing strategies

• ELISA IFA

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Diagnosis Seroconversion Rate
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Disease Terminology

• Carriers
• Animals that can transmit infectious diseases to
  other animals without ever showing clinical signs
• i.e. Lymphocytic choriomeningitis (LCM)

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Disease Terminology

• Zoonosis
• Diseases that can be transmitted from animals to
  humans
• TB
• Salmonella
• Ringworm
• Rabies
• Herpes B
• LCM
• Toxoplasmosis

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Disease Terminology

• Enzootic (Endemic)
• A disease that commonly occurs in several members
  of the population
• Epizootic (Epidemic)
• Sudden disease outbreak that affects a large
  number of animals

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Mouse Hepatitis Virus (MHV)

• Coronaviridae -ssRNA virus - 25 strains
• Most important pathogen of lab mice??
• Highly contagious
• Significant affect on experimental studies

Liver from mouse infected with MHV
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MHV - Clinical Patterns

• Epizootic (clinical) infections
• Introduction into a naive colony
• Adult disease uncommon
• Infant mice - diarrhea, runting and death
• Enzootic (subclinical) infections
• Breeding colonies - requires constant source of
  susceptible animals ( newborns)
• Infection in immunodeficient mice
• Wasting disease and death

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MHV - Runting
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MHV - Mode of transmission

• Aerosol
• Direct contact
• Fomites
• Transplantable tumors
• Transplacental passage

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MHV - Tissue Tropism

• Enterotropic (intestinal) strains
• LIVIM, MHV-D, MHV-Y
• Polytropic (Respiratory) strains
• MHV-1, MHV-2, A59, S, JHM
• Hepatotropic strain

Histopathic lesion in liver syncitial cell
formation
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MHV - Genetic Susceptibility

• Immunocompetent mice
• Resistant - A
• Semi-susceptible - C3H, CBA, AKR
• Fully susceptible - DBA/2, BALB/c, NZB, C57BL/6,
  B10.D2
• Immunocompromised mice - Chronic Wasting Disease

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MHV (Wasting Disease)
Athymic Mouse
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The Effects of Disease on Research

• Mouse Hepatitis Virus (MHV)
• High mortality in newborn mice
• Diarrhea
• Immune function affected
• Alter studies involving tumors, liver function,
  and immune system function

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Mouse Parvovirus (MPV) and Minute Virus of Mice
(MMV)

• Highly contagious
• Associated with digestive tract.
• Causes alterations in immune function.
• Resistant in the environment and to many chemical
  disinfectants
• Elimination requires rederivation.

Mouse parvovirus affects coat color, hair
density, and growth rates.
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Rotavirus

• Epizootic Diarrhea of Infant Mice (EDIM)
• Associated with digestive tract
• Causes diarrhea in pups during the first two
  weeks of age
• No clinical signs in adults
• Elimination is through rederivation

(Left) Mice infected with MHV. (Middle) Normal
mice. (Right) Mice infected with Rotavirus.
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Runting - MHV vs Rotavirus
MHV
Normal
EDIM
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MHV vs Rotavirus - Gross
MHV
Normal
EDIM
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Mousepox (Ectromelia)

• High morbidity and mortality
• Depending on strain may cause hepatitis
• Transmitted through tissue culture and
  transplants
• Swelling and necrosis of appendages is common
• No treatment

Mousepox showing amputated foot.
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Helicobacter

• Helicobacter hepaticus
• typhlitis,
• chronic active hepatitis, cofactor for hepatic
  carcinogenesis
• Helicobacter bilis
• chronic, active hepatitis?
• Heliocobacter rodentium

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Helicobacter sp.- Diagnosis

• Microaerophilic culture of large intestine.,
  liver, or feces
• Serologic testing - ELISA
• PCR
• Pooled fecal samples or tissue (lg. int. or
  liver) samples
• Histopathology

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Helicobacter sp - Containment or Eradication?

• Containment
• Microisolator cages
• Forceps transfer of mice
• Changing one cage at a time - biosafety hood
• Eradication?
• Antibiotics - Amoxicillin trimethoprim
  sulfamethoxizole ?
• Neonatal transfer
• Embryo transfer

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Lymphocytic choriomeningitis Virus (LCMV)

• RNA, Arenavirus
• Disease found naturally in mice and hamsters
• Vertical and horizontal transmission
• Zoonotic high level of shedding in affected
  animals
• May be used in animal models

Outcomes of LCMV infection.
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Sendai Virus

• RNA virus, Paramyxovirus
• Affects both rats and mice
• Highly infectious
• Morbidity is 100
• Epizootic high death rate in young animals
• Enzootic subclinical
• Suppresses the immune system
• Elimination requires rederivation or cessation of
  breeding.

Intranuclear inclusion bodies in
bronchoepithelium of a nude mouse infected with
Sendai
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The Effects of Disease on Research

• Sendai Virus
• Results in bronchitis and pneumonia
• Profound influence on immune system
• Rats-tracheal, bronchial, and bronchiolar necrosis

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Sialodacryoadenitis Virus (SDAV)

• SDAV - Coronavirus
• Host range
• Most common virus in laboratory rats
• rats and inoculated infant mice
• Clinical disease
• Highly contagious
• Contact or aerosol transmission
• Neck swelling, keratoconjunctivitis, ophthalmic
  lesions
• Lesions
• necrosis of ductular epithelium
• Control
• self-limiting if susceptible animals removed

Cervical swelling and kertoconjunctivitis
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Mycoplasmosis

• Mycoplasma pulmonis
• Rats (less common in mice)
• Chronic respiratory disease or murine respiratory
  mycoplasmosis (MRM)
• Major health problem in rats
• Horizontal and vertical transmission
• Red and gray consolidation of lungs, with
  abscesses
• Difficult to eradicate

Lung infected with Mycoplasmosis.
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The Effects of Disease on Research

• Mycoplasmosis
• Complicate studies of the respiratory tract
• Increases lung neoplasia
• Increases the severity of arthritis
• reduced reproductive function

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Endoparasites of Mice and Rats

• Protozoa
• Sporozoa - Pneumocystis carinii
• Flagellates -Giardia muris
• Amoebae - Entamoeba muris
• Helminths
• Nematodes - Syphacia Aspicularis spp.
• Cestodes - Hymenolepsis spp.

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Pneumocystis carinii

• Opportunistic Protozoa
• Hosts - man, rodents, rabbits, dogs, cats, farm
  animals
• Pathology - pneumonia in compromised hosts
• Diagnosis - histopathology, serology
• Treatment - Sulfas and trimethroprim

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Pinworms (Oxyurids)

• Syphacia obvelata - Mouse pinworm
• Syphacia muris - Rat pinworm
• Aspicularis tetraptera - Mouse or rat pinworms

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Pinworms

• Frequently no clinical signs.
• Rectal prolapses, intussusceptions, enteritis,
  fecal impactions may occur.
• Difficult to eradicate due to resistant eggs in
  the environment.
• Fenbendazole is the treatment of the choice.

Pinworm eggs, Syphacia obvelata
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Pinworms - Syphacia sp.

• Direct life cycle - (Completed in 11-15 dys.)

Embryonate
Infective in 5-24 hours
Eggs deposited in perianal region
Migrate to cecum or lg. int. and mature
Ingested from perianal region
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Pinworms - Research Complications

• Immunological System - reduced antibody
  production induction of lymphomas in athymic
  mice

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Pinworms - Prevention Control

• Re-derivation
• Depopulation
• Isolation by barrier techniques
• Strict sanitation
• Eggs infective for at least 4 weeks
• Sodium hypochlorite heat time
• Ethylene oxide

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Rats and Mice

• Ectoparasites
• Mites and lice are found in rodent colonies
• Use antiparasitic drugs, such as ivermectin or
  pyrethrins.

Mite
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Mite lesions?
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Ectoparasites - Diagnosis

• Detected by examining the animals pelt.

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Noninfectious Skin Disorders
Fighting
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Noninfectious Skin Disorders
Barbaring
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Noninfectious Skin Disorders
De chewer
De chewee
Whisker Chewing
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Noninfectious Skin Disorders
Chronic Ulcerative Dermatitis
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Chronic Ulcerative Dermatitis

• Predominantly B6 Mice
• Previously suspected etiologies
• Ectoparasite (mite) infestation
  (hypersensitivity)
• Dermatitis secondary to behavioral trauma
• Lupus-like syndrome
• Immune complex induced vasculitis

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Non-infectious Disease

• Malocclusion
• Incisor teeth that grow too long interfere with
  the animals ability to eat.
• Highly heritable and should not be bred.

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Porphyrin Staining