Rat Diseases

Rat Diseases Rat Diseases

Bacterial diseases Bacterial diseases

Murine Respiratory Mycoplasmosis Murine Respiratory Mycoplasmosis

Mycoplasma pulmonisMycoplasma pulmonisVery common and important!Very common and important!Transmission: Transmission: intrauterine and intrauterine and aerosolaerosolChronicChronic subclinical carrier state; subclinical carrier state; disease precipitated by disease precipitated by stress andstress and airway damageairway damage

Same as mice… Same as mice…

Nasal Discharge – Porphyrin StainingNasal Discharge – Porphyrin Staining

Murine Respiratory Mycoplasmosis- Murine Respiratory Mycoplasmosis- “Cobblestone” lung“Cobblestone” lung

StreptococcosisStreptococcosis

Streptococcus pneumoniaeStreptococcus pneumoniae

HumansHumans are primary reservoir are primary reservoir

Transmission by Transmission by aerosol and aerosol and contactcontact

Incidence of infection is lowIncidence of infection is low


Clinical signs:Clinical signs:– URT infection that spreads to LRTURT infection that spreads to LRT– Especially effects Especially effects youngyoung rats rats

Dyspnea, snuffling, abdominal Dyspnea, snuffling, abdominal breathingbreathing

Weight loss, hunched postureWeight loss, hunched posture


Pathologic findings:Pathologic findings:– Fibrinopurulent pleuritisFibrinopurulent pleuritis– PericarditisPericarditis– Otitis mediaOtitis media

Fibrinopurulent pleuritisFibrinopurulent pleuritis


Diagnosis and treatment:Diagnosis and treatment:– Histology and Histology and cultureculture– OxytetracyclineOxytetracycline in water will control in water will control

mortality but will not eliminate carrier mortality but will not eliminate carrier statestate

Rat Bite (Haverhill) FeverRat Bite (Haverhill) Fever

Streptobacillus moniliformisStreptobacillus moniliformisCommensal in Commensal in nasopharynxnasopharynx of wild and of wild and some laboratory ratssome laboratory ratsTransmission: (Transmission: (rat bitesrat bites, aerosol, , aerosol, contaminated bedding, fomites)contaminated bedding, fomites)ZoonoticZoonotic (endocarditis/DJD) (endocarditis/DJD)

Rat Bite FeverRat Bite Fever

Diagnosis:Diagnosis:– Very Very difficult to culturedifficult to cultureTreatment:Treatment:– PenicillinPenicillin (no procaine use Pen G (no procaine use Pen G

benzathine or Streptomycin if benzathine or Streptomycin if used in rats)used in rats)

Tyzzer’s Disease

Etiology: Etiology:

Clostridium piliformeClostridium piliforme is a gram-negative, is a gram-negative, obligate intracellular rod that produces obligate intracellular rod that produces spores spores

• See mice….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 Staphylococcal Dermatitis

A syndrome of ulcerated to scabby skin lesions on A syndrome of ulcerated to scabby skin lesions on the dorsal cervical or cranial regions occur the dorsal cervical or cranial regions occur frequently in some rat colonies . frequently in some rat colonies . This syndrome This syndrome appears to be seasonal with most cases occurring appears to be seasonal with most cases occurring in the spring and occasionally the fall.in the spring and occasionally the fall. Trauma to Trauma to the skin from fighting, scratching, etc. is thought to the skin from fighting, scratching, etc. is thought to be an inciting factorbe an inciting factor. . In many cases, In many cases, Staphylococcus Staphylococcus sp., including sp., including S. S. aureusaureus and and S. epidermidisS. epidermidis, have been isolated , have been isolated from the woundsfrom the wounds..

Staphylococcal DermatitisStaphylococcal Dermatitis

Combination therapy of oral Combination therapy of oral benadryl (10 mg/kg) and benadryl (10 mg/kg) and chloramphenicol (50 chloramphenicol (50 mg/kg) has resulted in mg/kg) has resulted in resolution of ulcerative resolution of ulcerative lesions. lesions.

Clipping toenails of the Clipping toenails of the hind foot has allowed hind foot has allowed healing of the wounds healing of the wounds without antibiotic therapy without antibiotic therapy

Clean with Nolvasan Clean with Nolvasan

Viral diseases Viral diseases

Sialodacryoadenitis virus (SDAV)Sialodacryoadenitis virus (SDAV)

Very common coronavirusVery common coronavirus

Highly Highly contagiouscontagious via aerosol, via aerosol, contact, fomitescontact, fomites

Tropism for Tropism for salivarysalivary, , lacrimallacrimal, , Harderian glandHarderian gland, and lung, and lung

Usually Usually mild diseasemild disease (strain (strain dependent)dependent)

Sialodacryoadenitis virus (SDAV)Sialodacryoadenitis virus (SDAV)

Clinical signs (transient):Clinical signs (transient):– Oculonasal porphyrinOculonasal porphyrin staining staining– Enlarged Enlarged submaxillary salivarysubmaxillary salivary gland gland– Exophthalmus Exophthalmus and and blepharospasmblepharospasm

(keratitis/corneal ulcers)(keratitis/corneal ulcers)– PhotophobiaPhotophobia

SnifflingSniffling, nasal crackles, nasal crackles

SDAV- ExopthalmiaSDAV- Exopthalmia

– Swollen edematous salivary glands– Cervical lymph node enlargement

interstitial pneumonia

SDAV- TreatmentSDAV- Treatment

No treatment availableNo treatment available

No carrier stateNo carrier state

Spread contamination throughout Spread contamination throughout large colony so that every rat gets large colony so that every rat gets infected or separate out clinical infected or separate out clinical cases in small colonycases in small colony

Cease breeding Cease breeding for 2 monthsfor 2 months

Parvoviruses (RV, H-1, RMV, and RPV-Parvoviruses (RV, H-1, RMV, and RPV-1a) 1a)

Etiology: Etiology: Parvoviruses are single stranded DNA Parvoviruses are single stranded DNA viruses. Multiple species of parvoviruses in viruses. Multiple species of parvoviruses in rats include Rat Virus rats include Rat Virus (RV or Kilham rat (RV or Kilham rat virus),virus), H-1 (Toolan's H-1 virus), Rat Minute H-1 (Toolan's H-1 virus), Rat Minute Virus (RMV 1a, 1b and 1c) and Rat Virus (RMV 1a, 1b and 1c) and Rat Parvovirus 1 (RPV-1a). Of these, RV is the Parvovirus 1 (RPV-1a). Of these, RV is the only virus species reported to cause clinical only virus species reported to cause clinical disease in rats disease in rats

Parvovirus cont..Parvovirus cont..

Transmission is primarily by direct contact or Transmission is primarily by direct contact or contact with fomites. contact with fomites. Clinical Signs: Parvovirus infections are usually Clinical Signs: Parvovirus infections are usually subclinical. subclinical. In newly infected breeding colonies, RV causes In newly infected breeding colonies, RV causes decreased fertility, fetal resorption, small litters, decreased fertility, fetal resorption, small litters, and runting of pups.and runting of pups.

Parvovirus cont..Parvovirus cont..

Diagnosis: Serologic assays are used for Diagnosis: Serologic assays are used for virus identification virus identification

Control: Eliminate seropositive rats and Control: Eliminate seropositive rats and replace with parvovirus-free animals. Since replace with parvovirus-free animals. Since parvoviruses can survive for weeks in the parvoviruses can survive for weeks in the environment, environmental clean-up with environment, environmental clean-up with parvovirocidal disinfectants is critical to parvovirocidal disinfectants is critical to prevent re-infection of clean rats prevent re-infection of clean rats

Parasites Parasites

Radfordia ensiferaRadfordia ensifera “Rat Fur Mite” “Rat Fur Mite”

Relatively commonRelatively common

Transmission by direct contactTransmission by direct contact

May be May be subclinicalsubclinical, or cause:, or cause:

Scruffiness, Scruffiness, prurituspruritus, , patchy patchy alopeciaalopecia, , self-traumaself-trauma, , skin skin ulcerationsulcerations, pyoderma, secondary , pyoderma, secondary bacterial infectionsbacterial infections

Radfordia ensifera “Rat Fur Mite”Radfordia ensifera “Rat Fur Mite”

Diagnosis: collection and Diagnosis: collection and examination of mitesexamination of mites

Treatment:Treatment:

IvermectinIvermectin at 0.2 mg/kg SQ may be at 0.2 mg/kg SQ may be effective when administered every 2 to 3 effective when administered every 2 to 3 weeks for a total of 3 treatments weeks for a total of 3 treatments

Flagellated ProtozoaFlagellated Protozoa

Spironucleus muris Spironucleus muris andand Giardia muris Giardia muris are are protozoa that colonize the upper small protozoa that colonize the upper small intestine;intestine; Spironucelus muris Spironucelus muris dwells in the dwells in the mucosal crypts of the small intestine and in mucosal crypts of the small intestine and in the pylorus, and the pylorus, and Giardia murisGiardia muris resides resides along the villous enterocytes in the anterior along the villous enterocytes in the anterior small intestine.small intestine.

Syphacia murisSyphacia muris (Rat Pinworm) (Rat Pinworm)

Transmission: Transmission: Syphacia murisSyphacia muris deposits deposits eggs in the perianal region. Transmission eggs in the perianal region. Transmission of infection occurs via ova ingestion. The of infection occurs via ova ingestion. The eggs are very light and have been shown to eggs are very light and have been shown to aerosolize, resulting in widespread aerosolize, resulting in widespread exposure. The incidence of infection is exposure. The incidence of infection is high.high.

Clinical Signs: Clinical Signs:

No signs are usually seen. It has been No signs are usually seen. It has been reported that heavy parasite loads may reported that heavy parasite loads may lead to catarrhal enteritis, or perianal lead to catarrhal enteritis, or perianal irritation causing hair to be chewed off the irritation causing hair to be chewed off the tail base tail base

Diagnosis:Diagnosis:

Direct exam of cecal Direct exam of cecal contents, fecal flotation, contents, fecal flotation, and tape test of the and tape test of the perianal regionperianal region will identify will identify adults and eggs, adults and eggs, respectively. The eggs are respectively. The eggs are slightly smaller and more slightly smaller and more symmetrical than those of symmetrical than those of Syphacia obvelataSyphacia obvelata. .

This image shows This image shows adult pinworms found adult pinworms found in the cecum and in the cecum and large intestine large intestine

Treatment:Treatment:

If treatment is desired, If treatment is desired, piperazinepiperazine (4 to 7 mg/ml (4 to 7 mg/ml water) for 3 to 10 days is effective. Karo syrup water) for 3 to 10 days is effective. Karo syrup can be added to the solution if the rats refuse to can be added to the solution if the rats refuse to drink it. drink it. Fenbendazole medicated feed provided every Fenbendazole medicated feed provided every other week for 5 weeks has been an effective other week for 5 weeks has been an effective treatment method. treatment method. Ivermectin at 0.2 mg/kg subQ weekly for 2 to 3 Ivermectin at 0.2 mg/kg subQ weekly for 2 to 3 weeks or in drinking water (25 mg/liter) for 4 to 5 weeks or in drinking water (25 mg/liter) for 4 to 5 daily treatments 3 days apart. daily treatments 3 days apart.

Control:Control:

Rigid sanitary procedures, use of filtered Rigid sanitary procedures, use of filtered cage tops to prevent aerosol transmission, cage tops to prevent aerosol transmission, and regular ova examinations with and regular ova examinations with treatment may control the parasitism. treatment may control the parasitism.

NEOPLASTIC DISEASES NEOPLASTIC DISEASES

Mammary FibroadenomaMammary Fibroadenoma

Most commonMost common rat tumor rat tumor

Almost always Almost always benignbenign

Rare in malesRare in males

Fast growingFast growing

Will make you a hero (easy to fix)Will make you a hero (easy to fix)

Surgical excision (Surgical excision (be quickbe quick, look for “, look for “feeder feeder vesselvessel”, ”, keep rat warmkeep rat warm and and well hydratedwell hydrated))

Mammary FibroadenomaMammary Fibroadenoma

Because of the Because of the extensive mammary extensive mammary tissue present in rats, tissue present in rats, tumors may be found tumors may be found practically anywhere--practically anywhere--behind the shoulder behind the shoulder blades, at the base of blades, at the base of the tail, etc. the tail, etc.

Look mom, I can Carry my tumor!

Mammary FibroadenomaMammary Fibroadenoma With surgical removal, the prognosis is good, although recurrence in another location is common.

Pituitary Chromophobe Adenoma Pituitary Chromophobe Adenoma

This is an extremely common This is an extremely common tumor of rats, although tumor of rats, although incidence varies with strain. incidence varies with strain. Grossly, tumors are soft with Grossly, tumors are soft with an irregular surface and may an irregular surface and may have prominent hemorrhagic have prominent hemorrhagic areas. They are generally well areas. They are generally well circumscribed and compress circumscribed and compress adjacent brain tissue, adjacent brain tissue, occasionally causing occasionally causing hydrocephalus resulting in hydrocephalus resulting in depression or head tilt. The depression or head tilt. The tumors commonly secrete tumors commonly secrete prolactinprolactin

MISCELLANEOUS DISEASESMISCELLANEOUS DISEASES

MalocclusionMalocclusion

Autosomal recessiveAutosomal recessive trait trait

Incisors overgrown poorly alignedIncisors overgrown poorly aligned

Inanition, oral trauma, ptyalismInanition, oral trauma, ptyalism (“slobbers”), (“slobbers”), starvationstarvation

Diagnosis- just lookDiagnosis- just look

Do not breedDo not breed these rats these rats

ClipClip w/sharp human nail clippers but avoid w/sharp human nail clippers but avoid scissoring action. Dremmel-type dental disc every scissoring action. Dremmel-type dental disc every 2 to 3 months2 to 3 months

MalocclusionMalocclusion

Heat ExhaustionHeat Exhaustion

Rats have a limited ability to regulate body Rats have a limited ability to regulate body temperature with the primary temperature with the primary thermoregulatory mechanism being tail thermoregulatory mechanism being tail vein vein dilation or constrictiondilation or constriction. .

Males also use Males also use scrotal vasculaturescrotal vasculature for for same purposesame purpose

Hyperemic scrotumHyperemic scrotum (pathognomonic) (pathognomonic)

Heat ExhaustionHeat Exhaustion

Predisposing factors to heat Predisposing factors to heat exhaustion are ambient exhaustion are ambient temperatures above 28oC temperatures above 28oC (85oF), high humidity (about (85oF), high humidity (about 80%), poor ventilation and 80%), poor ventilation and overcrowding overcrowding The rats salivate profusely to The rats salivate profusely to wet the hair coat for cooling, wet the hair coat for cooling, and water consumption and water consumption increases (see photo). increases (see photo). Death from heat exhaustion Death from heat exhaustion can be diagnosed from history can be diagnosed from history of high temperature, lack of of high temperature, lack of water (or empty water bottles), water (or empty water bottles), saliva soaked chins saliva soaked chins

Treatment of affected rats Treatment of affected rats includes cool water baths, includes cool water baths, forced-feeding water, and forced-feeding water, and subcutaneous saline or subcutaneous saline or 5% dextrose 5% dextrose administration administration

RingtailRingtail

Low environmental humidity (<40%)Low environmental humidity (<40%)

Annular constriction of the base of the Annular constriction of the base of the tailtail

More common in weanlings and rats in More common in weanlings and rats in wire-bottom cageswire-bottom cages

Tail may sloughTail may slough

Increase humidity Increase humidity and provide beddingand provide bedding

RingtailRingtail

Tail stumps usually heal Tail stumps usually heal without complication. without complication. Prevention of ringtail is Prevention of ringtail is accomplished by providing accomplished by providing sufficient environmental sufficient environmental humidity, reducing drafts, humidity, reducing drafts, and maintaining room and maintaining room temperatures between temperatures between 70oF to 74oF. 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 ZOONOTIC DISEASES

Salmonella Salmonella

Rats are reservoirs for bacterial diseases that are Rats are reservoirs for bacterial diseases that are pathogenic to man. Salmonellosis, especially pathogenic to man. Salmonellosis, especially Salmonella entericaSalmonella enterica serovars Enteritidis and serovars Enteritidis and Typhimurium have been diagnosed in research Typhimurium have been diagnosed in research and pet rats.and pet rats.Salmonellae are Gram-negative toxin-producing Salmonellae are Gram-negative toxin-producing enteric bacteria that are transmitted through enteric bacteria that are transmitted through contact with infected feces. Rats are frequently contact with infected feces. Rats are frequently asymptomatically infected, and rarely exhibit asymptomatically infected, and rarely exhibit systemic infection. systemic infection. Definitive diagnosis of infection is provided by Definitive diagnosis of infection is provided by culture culture

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Rat Diseases