Transcript Document

Mice diseases
Bacterial diseases
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

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”

Mycoplasma pulmonis
Early signs: purulent nasal discharge, otitis
media, sneezing, “sniffling”, porphyrin
staining
 Progresses to labored breathing, anorexia,
lethargy, hunched posture
 Bronchopneumonia

Gross Lesions
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In advanced disease, the
lungs can have graypurple patches that often
have a "cobblestone"
appearance.
Pictures…
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,
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.
Treatment
Tetracycline limits losses
 Enrofloxacin
 Dosages p.58
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Tyzzer’s disease

Clostridium piliforme is the cause of
Tyzzer’s disease. It is a gram-negative,
motile, spore-forming bacillus. It has
been grown in embryonated eggs and
cell cultures
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.
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.
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.

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.
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.
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
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
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
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
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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.
Diagnosis

Diagnosis of salmonellosis is by culture
and serotyping. Several sites should be
cultured, including liver, spleen,
mesenteric lymph nodes, blood, and
intestinal contents.
Control
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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.
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ZOONOTIC disease!!!
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.
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.
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
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
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
SDAV

The incubation period for
SDAV less than 1 week.
In naive populations, a
sudden high incidence of
overt disease with
sneezing, porphyrinstained nasal and ocular
discharges (as seen in
this image), cervical
edema, corneal
ulceration, and keratoconus may be the first
indications of a problem
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.
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
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.
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 <made the test
with naive mouse>
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.
Mouse Hepatitis Virus
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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
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
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)
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
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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
Rotavirus
Parasites
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
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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 selfmutilation. Early lesions
consist of subtle hair
thinning on the dorsal
neck and shoulders
Acariasis???
Myobia musculi
Single claw
Radfordia affinis
Two claws
Myocoptes musculinus
Pinworms
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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
Aspiculuris tetraptera
Syphacia obvelata
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

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
Tumors
Mammary Adenocarcinoma
 Most
common tumor of mice
 Mice have 3 pair of thoracic and 2
pair of abdominal mammary glandsglandular tissue may be found up
around the body to the dorsum
 Poor prognosis- anaplastic and very
invasive
Mammary Adenocarcinoma
Tissue: Mouse: mammary gland;
adenocarcinoma
Miscellaneous
Diseases
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
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
Malocclusion
 Genetic
predisposition (autosomal
recessive)
 Incisors hypsodont
 Inanition, starvation
 Trim teeth with nail clippers (no
“scissor” action)
 Do not breed these mice
Malocclusion