Rat bite fevers

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Rat Bite Fevers Dr.T.V.Rao MD

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Rat bite fevers

Transcript of Rat bite fevers

Page 1: Rat bite fevers

Rat Bite FeversDr.T.V.Rao MD

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Rat-bite Fever (RBF)Rat-bite fever (RBF) is an infectious disease that

can be caused by two different bacteria.

Streptobacillary RBF is caused by Streptobacillus

moniliformis in North America while spirillary RBF

or sodoku is caused by Spirillum minus and

occurs mostly in Asia. People usually get the

disease from infected rodents or consumption of

contaminated food or water..

If not treated, RBF can be a serious or even

fatal disease.

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Rat-bite feverRat-bite fever is an

acute, febrile human

illness caused by

bacteria transmitted by

rodents, rats or mice in

most cases, which is

passed from rodent to

human via the rodent's

urine or mucous

secretions.

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Risk FactorsAny person who is exposed

to the bacteria that cause

RBF is at risk for getting the

disease. Some people who

may be at increased risk

include those who:

Live in rat-infested buildings

Have pet rats at their home

Work with rats in

laboratories or pet stores

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Infected Rodents Spread

the Disease

.It is a rare

disease spread

by infected

rodents and can

be caused by two

specific types of

bacteria.

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Spirillum MinusShort Gram negative spiral organism3 – 5 microns

Stains with Giemsa stain

Dark field microscope useful

Not cultured- Can be isolated by inoculating the specimen Intraperitoneally into Mic

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Geographic location of Rat

bite fevers

Most cases occur in Japan, but specific

strains of the disease are present in the

United States, Europe, Australia, and

Africa. Some cases are diagnosed after

patients were exposed to the urine or

bodily secretions of an infected animal.

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Signs and Symptoms

Symptoms do not manifest for two to four weeks after exposure to the organism, and the wound through which it entered exhibits slow healing and marked inflammation. The fever lasts longer and is recurring, for months in some cases. Rectal pain and gastrointestinal symptoms are less severe or are absent. Penicillin is the most common treatment.

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Streptobacillus

moniliformis

Symptoms depend on the

bacteria that caused the

infection. Symptoms due to

Streptobacillus

moniliformis may include:

Chills

Fever Joint pain, redness,

or swelling Rash

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Spirillum minus

Symptoms due to Spirillum minus may include: Chills

Fever

Open sore at the site of the bite

Rash -- may be red/purple plaques

Swollen lymph nodes near the bite

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Streptobacillosis

The Streptobacillosis form of rat-bite fever is known by the alternative names Haverhill Fever and epidemic arthritic erythema. It is a severe disease caused by Streptobacillus moniliformis, transmitted either by rat bite or ingestion of contaminated products (Haverhill fever).

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Streptobacillosis

After an incubation period of 2–10 days,

Haverhill fever begins with high prostrating

fevers, rigors (shivering), headache and

polyarthralgia (joint pain). Soon an exanthem

(widespread rash) appears, either

maculopapular (flat red with bumps) or

petechial (red or purple spots) and arthritis of

large joints can be seen. The organism can

be cultivated in blood or articular fluid.

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Transmission

S. moniliformis and S. minus are part of the normal respiratory flora of rodents. Either organism may be transmitted to humans through bites or scratches. Infection can also result from handling an infected rodent (even with no reported bite or scratch), or ingestion of food or drink contaminated with these bacteria (Haverhill fever). Rats are considered the natural reservoir of RBF, but the bacterium has also been found in other rodent species such as, mice and gerbils. Person-to-person transmission has not been reported.

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Pathogenesis

S.minus enters the body through rat urine

Incubation period 1-4 weeks

Clinically present with swelling of lymph nodes near the site of bite with relapsing fever and skin rash

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Severe illnesses can

include:

Infections involving the heart (endocarditis, myocarditis, or pericarditis)

Infections involving the brain (meningitis)

Infections involving the lungs (pneumonia)

Abscesses in internal organs

While death from RBF is rare, it can occur if it goes untreated.

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DiagnosisThis condition is

diagnosed by

detecting the

bacteria in skin,

blood, joint fluid,

or lymph nodes.

Blood antibody

tests may also be

used.

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Other Methods of

Diagnosis To diagnose

streptobacillary rat bite

fever, blood or joint fluid

is extracted and the

organisms living in it are

cultured. Diagnosis for

spirillary rat bite fever is

by direct visualization or

culture of spirillum from

blood smears or tissue

from lesions or lymph

nodes.

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Prevention

Whilst obviously preventable by staying away from rodents, otherwise hands and face should be washed after contact and any scratches both cleaned and antiseptics applied. Prompt cleaning of wounds with antiseptic solution, and reducing the risk of rat bites. The effect of chemoprophylaxis following rodent bites or scratches on RBF is unknown. No vaccines are available for these diseases. Improve conditions to minimize rodent contact with humans is the best preventative measure for RBF.

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Avoid Contact with Rats

Improve conditions

to minimize rodent

contact with humans

is the best

preventative

measure for RBF.

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PreventionAnimal handlers, laboratory workers, sanitation and sewer workers must take special precautions against exposure. Wild rodents, dead or alive, should not be touched and pets must not be allowed to ingest rodents. Those living in the inner cities where overcrowding and poor sanitation cause rodent problems are at risk for RBF. Half of all cases reported are children under 12 living in these conditions.

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Treatment

Responds to penicillin

antibiotics or where

allergic to this

erythromycin or

tetracycline's for

respectively

streptobacillary or

spirillary infections.

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MD for Medical and Paramedical

students in the Developing world

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