Rat bite fevers

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Rat bite fevers

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Rat bite fevers

  1. 1. Rat Bite Fevers Dr.T.V.Rao MD
  2. 2. 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.
  3. 3. Rat-bite fever Rat-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.
  4. 4. Risk Factors Any 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
  5. 5. Infected Rodents Spread the Disease .It is a rare disease spread by infected rodents and can be caused by two specific types of bacteria.
  6. 6. Spirillum Minus Short 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
  7. 7. 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. Dr.T.V.Rao MD 8
  8. 8. 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.
  9. 9. 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
  10. 10. 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
  11. 11. 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). Dr.T.V.Rao MD 12
  12. 12. 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. Dr.T.V.Rao MD 13
  13. 13. 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. Dr.T.V.Rao MD 14
  14. 14. 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 Dr.T.V.Rao MD 15
  15. 15. 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. Dr.T.V.Rao MD 16
  16. 16. Diagnosis This condition is diagnosed by detecting the bacteria in skin, blood, joint fluid, or lymph nodes. Blood antibody tests may also be used.
  17. 17. Other Methods of DiagnosisTo 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.
  18. 18. 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. Dr.T.V.Rao MD 19
  19. 19. Avoid Contact with Rats Improve conditions to minimize rodent contact with humans is the best preventative measure for RBF. Dr.T.V.Rao MD 20
  20. 20. Prevention Animal 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. Dr.T.V.Rao MD 21
  21. 21. Treatment Responds to penicillin antibiotics or where allergic to this erythromycin or tetracycline's for respectively streptobacillary or spirillary infections.
  22. 22. Programme Created by Dr.T.V.Rao MD for Medical and Paramedical students in the Developing world Email doctortvrao@gmail.com

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