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Rat Diseases. Bacterial diseases. Mycoplasma pulmonis Very common and important! Transmission: intrauterine and aerosol Chronic subclinical carrier state; disease precipitated by stress and airway damage Same as mice…. Murine Respiratory Mycoplasmosis.
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Mycoplasma pulmonis Very common and important! Transmission: intrauterine and aerosol Chronic subclinical carrier state; disease precipitated by stress andairway damage Same as mice… Murine Respiratory Mycoplasmosis
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 Streptococcosis
Diagnosis and treatment: Histology and culture Oxytetracycline in water will control mortality but will not eliminate carrier state Streptococcosis
Streptobacillus moniliformis Commensal in nasopharynx of wild and some laboratory rats Transmission: (rat bites, aerosol, contaminated bedding, fomites) Zoonotic (endocarditis/DJD) Rat Bite (Haverhill) Fever
Diagnosis: Very difficult to culture Treatment: Penicillin (no procaine use Pen G benzathine or Streptomycin if used in rats) Rat Bite Fever
Etiology: Clostridium piliforme is a gram-negative, obligate intracellular rod that produces spores See mice…. Tyzzer’s Disease
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. Clinical Signs:
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 Gross Pathology:
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 Staphylococcal Dermatitis
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 Sialodacryoadenitis virus (SDAV)
– Swollen edematous salivary glands – Cervical lymph node enlargement
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 SDAV- Treatment
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 Parvoviruses (RV, H-1, RMV, and RPV-1a)
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 clean-up with parvovirocidal disinfectants is critical to prevent re-infection of clean rats Parvovirus cont..
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 Radfordia ensifera “Rat Fur Mite”
Ivermectin at 0.2 mg/kg SQ may be effective when administered every 2 to 3 weeks for a total of 3 treatments Treatment:
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. Flagellated Protozoa
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. Syphacia muris (Rat Pinworm)
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 Clinical Signs:
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. Diagnosis:
This image shows adult pinworms found in the cecum and large intestine
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. Treatment:
Rigid sanitary procedures, use of filtered cage tops to prevent aerosol transmission, and regular ova examinations with treatment may control the parasitism. Control:
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. Mammary Fibroadenoma Look mom, I can Carry my tumor!
Mammary Fibroadenoma With surgical removal, the prognosis is good, although recurrence in another location is common.
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 Pituitary Chromophobe Adenoma
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
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 Heat Exhaustion • Treatment of affected rats includes cool water baths, forced-feeding water, and subcutaneous saline or 5% dextrose administration
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
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.
