Transcript Rat Diseases - Kristin Singer

Rat Diseases
Murine Respiratory
Mycoplasmosis
Mycoplasma pulmonis
Very common and important!
Transmission: intrauterine and
aerosol
Chronic subclinical carrier state;
disease precipitated by stress and
airway damage
Same as mice…
Nasal Discharge – Porphyrin
Staining
Murine Respiratory
Mycoplasmosis- “Cobblestone”
lung
Streptococcosis
Streptococcus pneumoniae
Humans are primary reservoir
Transmission by aerosol and
contact
Incidence of infection is low
Streptococcosis
Clinical signs:
– URT infection that spreads to LRT
– Especially effects young rats
Dyspnea, snuffling, abdominal
breathing
Weight loss, hunched posture
Streptococcosis
Pathologic findings:
–Fibrinopurulent pleuritis
–Pericarditis
–Otitis media
Fibrinopurulent pleuritis
Streptococcosis
Diagnosis and treatment:
– Histology and culture
– Oxytetracycline in water will control
mortality but will not eliminate carrier
state
Rat Bite (Haverhill) Fever
Streptobacillus moniliformis
Commensal in nasopharynx of wild
and some laboratory rats
Transmission: (rat bites, aerosol,
contaminated bedding, fomites)
Zoonotic (endocarditis/DJD)
Rat Bite Fever
Diagnosis:
–Very difficult to culture
Treatment:
–Penicillin (no procaine use Pen G
benzathine or Streptomycin if
used in rats)
Tyzzer’s Disease
Etiology:
Clostridium piliforme is a gram-negative,
obligate intracellular rod that produces
spores
• See mice….
Clinical Signs:
Subclinical infection is
the most common form
of infection in the rat.
Clinical manifestations
of Tyzzer's disease
include anorexia,
hunched posture,
distended abdomen,
rough hair coat and
death. Diarrhea has not
been reported in the
rat.
Gross Pathology:
A "fat rat" syndrome with
a flaccid segmental
dilatation of the intestine
(especially of the ileum)
has been described. The
liver typically has multiple
pale foci throughout.
Circumscribed, greyish
foci may sometimes be
observed in the
myocardium. Multiple
necrotic foci in sections
of liver and myocardium
are often surrounded by a
pyogranulomatous cellular
infiltrate
Staphylococcal Dermatitis
A syndrome of ulcerated to scabby skin lesions
on the dorsal cervical or cranial regions occur
frequently in some rat colonies . This syndrome
appears to be seasonal with most cases
occurring in the spring and occasionally the
fall. Trauma to the skin from fighting, scratching,
etc. is thought to be an inciting factor.
In many cases, Staphylococcus sp., including S.
aureus and S. epidermidis, have been isolated
from the wounds.
Staphylococcal Dermatitis
Combination therapy of
oral benadryl (10 mg/kg)
and chloramphenicol (50
mg/kg) has resulted in
resolution of ulcerative
lesions.
Clipping toenails of the
hind foot has allowed
healing of the wounds
without antibiotic therapy
Clean with Nolvasan
Sialodacryoadenitis virus
(SDAV)
Very common coronavirus
Highly contagious via aerosol,
contact, fomites
Tropism for salivary, lacrimal,
Harderian gland, and lung
Usually mild disease (strain
dependent)
Sialodacryoadenitis virus
(SDAV)
Clinical signs (transient):
– Oculonasal porphyrin staining
– Enlarged submaxillary salivary gland
– Exophthalmus and blepharospasm
(keratitis/corneal ulcers)
– Photophobia
– Sniffling, nasal crackles
SDAV- Exopthalmia
– Swollen edematous salivary glands
– Cervical lymph node enlargement
interstitial pneumonia
SDAV- Pathology & Diagnosis
Coagulative necrosis & squamous
metaplasia of gland types above
Rhinitis, tracheitis, focal bronchitis,
bronchiolitis w/ neutrophil infiltrate
ELISA
SDAV- Treatment
No treatment available
No carrier state
Spread contamination throughout
large colony so that every rat gets
infected or separate out clinical
cases in small colony
Cease breeding for 2 months
Parvoviruses (RV, H-1, RMV, and
RPV-1a)
Etiology:
Parvoviruses are single stranded DNA
viruses. Multiple species of parvoviruses in
rats include Rat Virus (RV or Kilham rat
virus), H-1 (Toolan's H-1 virus), Rat Minute
Virus (RMV 1a, 1b and 1c) and Rat
Parvovirus 1 (RPV-1a). Of these, RV is
the only virus species reported to cause
clinical disease in rats
Parvovirus cont..
Transmission is primarily by direct contact or
contact with fomites.
Clinical Signs: Parvovirus infections are usually
subclinical.
In newly infected breeding colonies, RV causes
decreased fertility, fetal resorption, small litters,
and runting of pups.
Parvovirus cont..
Diagnosis: Serologic assays are used for
virus identification
Control: Eliminate seropositive rats and
replace with parvovirus-free animals.
Since parvoviruses can survive for weeks
in the environment, environmental cleanup with parvovirocidal disinfectants is
critical to prevent re-infection of clean rats
Parasites
Radfordia ensifera “Rat Fur
Mite”
Relatively common
Transmission by direct contact
May be subclinical, or cause:
–Scruffiness, pruritus, patchy
alopecia, self-trauma, skin
ulcerations, pyoderma, secondary
bacterial infections
Radfordia ensifera “Rat Fur
Mite”
Diagnosis: collection and
examination of mites
Treatment:
Ivermectin at 0.2 mg/kg SQ may be
effective when administered every 2 to 3
weeks for a total of 3 treatments
Flagellated Protozoa
Spironucleus muris and Giardia muris are
protozoa that colonize the upper small
intestine; Spironucelus muris dwells in the
mucosal crypts of the small intestine and
in the pylorus, and Giardia muris resides
along the villous enterocytes in the
anterior small intestine.
Syphacia muris (Rat Pinworm)
Transmission: Syphacia muris deposits
eggs in the perianal region. Transmission
of infection occurs via ova ingestion. The
eggs are very light and have been shown
to aerosolize, resulting in widespread
exposure. The incidence of infection is
high.
Clinical Signs:
No signs are usually seen. It has been
reported that heavy parasite loads may
lead to catarrhal enteritis, or perianal
irritation causing hair to be chewed off the
tail base
Diagnosis:
Direct exam of cecal
contents, fecal flotation,
and tape test of the
perianal region will
identify adults and eggs,
respectively. The eggs
are slightly smaller and
more symmetrical than
those of Syphacia
obvelata.
This image shows
adult pinworms found
in the cecum and
large intestine
Treatment:
If treatment is desired, piperazine (4 to 7 mg/ml
water) for 3 to 10 days is effective. Karo syrup
can be added to the solution if the rats refuse to
drink it.
Fenbendazole medicated feed provided every
other week for 5 weeks has been an effective
treatment method.
Ivermectin at 0.2 mg/kg subQ weekly for 2 to 3
weeks or in drinking water (25 mg/liter) for 4 to 5
daily treatments 3 days apart.
Control:
Rigid sanitary procedures, use of filtered
cage tops to prevent aerosol transmission,
and regular ova examinations with
treatment may control the parasitism.
NEOPLASTIC DISEASES
Mammary Fibroadenoma
Most common rat tumor
Almost always benign
Rare in males
Fast growing
Will make you a hero (easy to fix)
Surgical excision (be quick, look for
“feeder vessel”, keep rat warm and well
hydrated)
Mammary Fibroadenoma
Because of the
extensive mammary
tissue present in rats,
tumors may be found
practically anywhere-behind the shoulder
blades, at the base of
the tail, etc.
Look mom, I can
Carry my tumor!
Mammary Fibroadenoma
With surgical removal, the
prognosis is good, although
recurrence in another location is
common.
Pituitary Chromophobe Adenoma
This is an extremely
common tumor of rats,
although incidence varies
with strain. Grossly, tumors
are soft with an irregular
surface and may have
prominent hemorrhagic
areas. They are generally
well circumscribed and
compress adjacent brain
tissue, occasionally causing
hydrocephalus resulting in
depression or head tilt. The
tumors commonly secrete
prolactin
MISCELLANEOUS DISEASES
Malocclusion
Autosomal recessive trait
Incisors overgrown poorly aligned
Inanition, oral trauma, ptyalism (“slobbers”),
starvation
Diagnosis- just look
Do not breed these rats
Clip w/sharp human nail clippers but avoid
scissoring action. Dremmel-type dental disc
every 2 to 3 months
Malocclusion
Heat Exhaustion
Rats have a limited ability to regulate body
temperature with the primary
thermoregulatory mechanism being tail
vein dilation or constriction.
Males also use scrotal vasculature for
same purpose
Hyperemic scrotum (pathognomonic)
Heat Exhaustion
Predisposing factors to heat
exhaustion are ambient
temperatures above 28oC
(85oF), high humidity (about
80%), poor ventilation and
overcrowding
The rats salivate profusely to
wet the hair coat for cooling,
and water consumption
increases (see photo).
Death from heat exhaustion
can be diagnosed from
history of high temperature,
lack of water (or empty water
bottles), saliva soaked chins
Treatment of affected rats
includes cool water baths,
forced-feeding water, and
subcutaneous saline or
5% dextrose
administration
Ringtail
Low environmental humidity (<40%)
Annular constriction of the base of the
tail
More common in weanlings and rats in
wire-bottom cages
Tail may slough
Increase humidity and provide bedding
Ringtail
Tail stumps usually heal
without complication.
Prevention of ringtail is
accomplished by
providing sufficient
environmental humidity,
reducing drafts, and
maintaining room
temperatures between
70oF to 74oF.
Urinary calculi
Clinical signs may be
absent but obstruction
within the pelvis may cause
hydronephrosis.
Occlusion of the neck of
the bladder will cause
acute dilatation, uremia and
death.
ZOONOTIC DISEASES
Salmonella
Rats are reservoirs for bacterial diseases that
are pathogenic to man. Salmonellosis,
especially Salmonella enterica serovars
Enteritidis and Typhimurium have been
diagnosed in research and pet rats.
Salmonellae are Gram-negative toxin-producing
enteric bacteria that are transmitted through
contact with infected feces. Rats are frequently
asymptomatically infected, and rarely exhibit
systemic infection.
Definitive diagnosis of infection is provided by
culture