Mice diseases

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Mice diseases
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Bacterial diseases
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MRM

• Mycoplasma pulmonis is the cause of murine
  respiratory mycoplasmosis, or MRM
• In the respiratory tract, M. pulmonis
  preferentially colonizes the nasal passages and
  middle ears

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Etiology - Mycoplasma pulmonis

• Most infections are subclinical- carried in
  nasopharynx
• Disease induced by high cage ammonia or pathogens
• Slow onset, chronic condition
• Aerosol and direct contact
• Proximal Airway Disease

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Mycoplasma pulmonis

• Early signs purulent nasal discharge, otitis
  media, sneezing, sniffling, porphyrin staining
• Progresses to labored breathing, anorexia,
  lethargy, hunched posture
• Bronchopneumonia

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Gross Lesions

• In advanced disease, the lungs can have
  gray-purple patches that often have a
  "cobblestone" appearance.
• Pictures

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The left lobe of these lungs from a mouse with
experimental MRM has a gray-purple "cobblestone"
appearance due to accumulation of inflammatory
cells in and around airways,
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Diagnosis

• Commercial ELISA and IFA tests are useful for
  health monitoring, but serologic testing can be
  complicated by potential cross reactions with
  other rodent mycoplasmas.

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Treatment

• Tetracycline limits losses
• Enrofloxacin
• Dosages p.58

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Tyzzers disease

• Clostridium piliforme is the cause of Tyzzers
  disease. It is a gram-negative, motile,
  spore-forming bacillus. It has been grown in
  embryonated eggs and cell cultures

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Epizootiology

• C. piliforme has a worldwide distribution and a
  wide host range, including rats, mice, gerbils,
  hamsters, guinea pigs, rabbits, dogs, cats,
  horses, nonhuman primates, and various wild
  species. Mice appear to be affected more often
  than rats.

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Clinical signs

• Many affected rats and mice are simply found dead
  without prior signs being observed. If present,
  clinical signs include lethargy, ruffled fur, and
  diarrhea, as indicated by fecal soiling of the
  fur.

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Transmission

• Transmission is presumably fecal-oral.
• Possibilities include vertical transmission and
  introduction of spores via vermin contaminated
  feed or incompletely sterilized food, bedding,
  or water. Morbidity and mortality are highly
  variable.

term applied to various animal species regarded
as pests or nuisances and especially to those
associated with the carrying of disease.
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• The most consistent lesions in mice are multiple,
  pale, slightly depressed foci of necrosis in the
  liver, as seen here. Thickening and hyperemia of
  the intestine and pale areas in the myocardium
  also can be seen in some cases, but are not
  consistently present.

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Pathogenesis

• C. piliforme becomes established in the intestine
  as a primary infection, usually in the ileum,
  cecum, or both. It spreads via the portal
  circulation to the liver, and from there via the
  blood to other organs, chiefly the heart.

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Diagnosis 

• Since the organism cannot be propagated on
  artificial media, histopathologic diagnoses are
  made by demonstration of the bacillus in the
  enterocytes, hepatocytes or cardiac
• myocytes  bordering necrotic foci in tissues
  stained with silver stains

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Treatment

•   Oxytetracycline at 0.1 mg/ml water for 30 days
  was reported to abate mortality of an epizootic
  in mice.  Treatment is usually not warranted

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Salmonella

• Salmonella enteritidis is a gram-negative
  bacillus. Salmonellae are identified according to
  serotype, of which over 1500 exist.
• Virulence varies widely among serotypes
  enteritidis and typhimurium are most commonly
  associated with disease in rodents

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Epizootiology

• Salmonellosis was a major epizootic and enzootic
  disease of laboratory mice prior to the 1950s,
  but clinical salmonellosis in mice is now rare.
  Transmission is fecal-oral. Salmonellae in
  general are not very host specific, and carriers
  are common among exposed populations. Therefore,
  potential sources of infection for laboratory
  mice include vermin contaminated food, water,
  bedding, and fomites

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Clinical signs

• Most infections are subclinical.
• Signs in mice infected with weakly virulent
  serotypes vary from none to occasional losses
  among sucklings and weanlings

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Gross lesions

• This mouse with salmonellosis has pale foci of
  necrotizing and suppurative hepatitis at the
  margins of the liver lobes (arrows). The spleen
  is greatly enlarged due to production of
  increased numbers of neutrophils, or myeloid
  hyperplasia.

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Diagnosis

• Diagnosis of salmonellosis is by culture and
  serotyping. Several sites should be cultured,
  including liver, spleen, mesenteric lymph nodes,
  blood, and intestinal contents.

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Control

• Special attention should be given to vermin
  control and procurement and storage of bedding
  materials and food, which are easily contaminated
  by wild rodents. If salmonellosis is diagnosed in
  a research facility, the facility should be
  immediately quarantined, the affected populations
  destroyed and their environment decontaminated.
• ZOONOTIC disease!!!

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Skin

• Staphylococcus aureus is the major pathogen for
  the skin of mice and rats.
• Staphyloccus aureus is a gram-positive coccus
  that typically grows in clusters. It commonly
  inhabits the skin, skin glands, nasopharynx, and
  intestine of many host species.

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Epizootiology

• Staph. aureus is a common commensal of many
  species. It also is common in the environment.
• Human carriers can be an important source of
  infection for rodent colonies

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• Staph. aureus is associated mostly with
  dermatitis in the form of pyoderma or ulcerative
  dermatitis. The face, shoulders, neck, and ears
  are most commonly affected.

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Staphylococcus aureus

• Abscesses and granulomas, most commonly affecting
  the face and tissues around the base of the tail,
  also occur and can be associated with fight
  wounds

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Staphylococcus aureus

• The best methods of control are improved
  sanitation, frequent sanitizing of cages and
  other equipment, and elimination of equipment
  that could cause skin injury
• Topical treatment with Nolvasan BID

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Viral diseases
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SDAV (Sendai Virus) SV

• Sialodacryoadenitis virus (SDAV), another
  coronavirus (Parainfluenza 1), is one of the most
  common viruses found in laboratory rats and mice.
  It is highly contagious, and is spread by direct
  contact with infected animals or by respiratory
  aerosol

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SDAV

• The incubation period for SDAV less than 1 week.
  In naive populations, a sudden high incidence of
  overt disease with sneezing, porphyrin-stained
  nasal and ocular discharges (as seen in this
  image), cervical edema, corneal ulceration, and
  keratoconus may be the first indications of a
  problem

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Sendai Virus

• This image shows swollen submandibular salivary
  glands (arrows) in a mouse with SDAV. SDAV has
  tissue tropism for the submaxillary and parotid
  salivary, exorbital, Harderian, and intraorbital
  lacrimal glands

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• In rats and mice, few gross morphologic lesions
  are seen in uncomplicated Sendai infections. The
  lungs can be focally reddened and atelectatic
  with serous fluid visible in the pleural and
  pericardial cavities.

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Mouse Hepatitis Virus (MHV)

• Mouse hepatitis virus (MHV) and
  sialodacryoadenitis virus (SDAV) are frequently
  encountered coronaviruses of mice and rats
  respectively
• Some primarily infect the gastrointestinal
  system some the respiratory tract some the
  brain

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MHV

• Mice (Mus musculus) are the only natural hosts.
  MHV is extremely contagious with prevalence rates
  exceeding 80 in outbreaks. Active infection
  lasts 2-3 weeks, during which mice shed the virus
  in gastrointestinal and respiratory excretions.
  Direct contact with shedding mice, contaminated
  cell lines, fomites, or airborne particles are
  the important routes of viral transmission.

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MHV

• An epizootic can produce nonspecific clinical
  signs in naïve, juvenile mice, such as runting,
  as shown here, or failure to thrive

not previously subjected to experimentation or a
particular experimental situation ltmade the test
with naive mousegt
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MHV

• This image shows large coalescing cream-colored
  friable foci (arrow) of necrosis that result when
  acute multifocal hepatitis progresses to chronic
  active hepatitis in nude mice. Gross pathology in
  immune-incompetent mice is more generalized and
  progressive than in immune-competent mice.

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Mouse Hepatitis Virus

• Enterotropic versus respiratory strains
• Extremely contagious by many routes
• Nursing pups diarrhea and mortality
• Weanlings Obstipation
• Adults Hunched posture, weight loss, rough hair
  coat, variable mortality
• No latent infections- stop breeding
• ELISA

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Mouse Hepatitis Virus

• Diagnosis of latent infections is dependent on
  the histologic demonstration of large,
  multinucleate syncytial cells (arrow) in the
  liver, brain, or mucosal epithelium of the
  intestine

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Rotavirus

• Rotavirus, another genus of the family
  Reoviridae, is associated with clinical disease.
  Rotaviruses affecting mice and rats respectively
  are mouse rotavirus, a group-A rotavirus
  associated with the syndrome, epizootic diarrhea
  of infant mice (EDIM)

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Rotavirus

• Epizootic Diarrhea of Infant Mice (EDIM)
• Most susceptible birth to 17 days of age
• Fecal-oral transmission
• Yellow, watery diarrhea in 14-17 day old pups
• Death with a full stomach (versus reovirus),
  shortened intestinal villi
• Unapparent viral carriers
• ELISA

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EDIM

• Neonatal diarrhea is the most prominent sign.
  Watery yellow stool accumulates around the anus
  and tailbase, soiling the coats of neonatal pups
  and their dams. Pups appear stunted and lethargic
  and have distended abdomens. Mortality rates are
  low

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Rotavirus
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Parasites
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Myobia musculi, Radfordia affinis, and Myocoptes
musculinus

• Common
• Transmitted by direct contact
• May be subclinical, or develop pruritus, scruffy
  coat, patchy alopecia, self-trauma, pyoderma
• Typically found on back and head
• Mist with ivermectin (0.1) for 3 weekly
  treatments

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Myobia musculi

• Myobia musculi lesions in a pet white mouse,
  characteristic of hypersensitivity to the mites.
  Intense pruritus, often directed at the neck and
  ears, leads to self-mutilation. Early lesions
  consist of subtle hair thinning on the dorsal
  neck and shoulders
• Acariasis???

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Myobia musculi
Single claw
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Radfordia affinis
Two claws
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Myocoptes musculinus
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Pinworms

• Common
• Fecal-oral transmission
• Usually subclinical, but may cause rectal
  prolapse
• Fecal floatation (Aspiculuris tetraptera) or tape
  test (Syphacia obvelata)
• Ivermectin misting (others more labor intensive)
• Clean environment well

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Aspiculuris tetraptera
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Syphacia obvelata
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Rodentolepis nana and Hymenolepis diminuta

• Common tapeworms among pet mice
• Roaches, beetles, fleas intermediate hosts
• R. nana also transmitted directly, or by
  autoinfection (retroinfection)
• Usually subclinical infection

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Rodentolepis nana and Hymenolepis diminuta

• Often find proglottids in feces instead of
  individual eggs
• Zoonotic (more commonly R. nana because of direct
  transmission)
• Praziquantel is effective

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Rodentolepis nana
Polar filaments
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Tumors
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Mammary Adenocarcinoma

• Most common tumor of mice
• Mice have 3 pair of thoracic and 2 pair of
  abdominal mammary glands- glandular tissue may be
  found up around the body to the dorsum
• Poor prognosis- anaplastic and very invasive

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Mammary Adenocarcinoma
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Tissue  Mouse mammary gland adenocarcinoma
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MiscellaneousDiseases
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Barbering

• Animal model of trichotillomania
• MOBS (Move Over Buddy Syndrome)
• Alopecia (R.O. ectoparasites, dermatophytes,
  endocrinopathy)
• Well demarcated area of alopecia without
  dermatitis- exposed skin appears normal
• Commonly involves hair over the nasal and orbital
  regions, or over the dorsal cervical area
• Separate out barber

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Barbering
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Bite Wounds

• Males fight and abuse females
• Bites often found on face, back, and genital area
• May abscess
• Nolvasan ( lance abscesses)
• Separate offenders
• Provide enrichment

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Malocclusion

• Genetic predisposition (autosomal recessive)
• Incisors hypsodont
• Inanition, starvation
• Trim teeth with nail clippers (no scissor
  action)
• Do not breed these mice

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Malocclusion