Most of the rickettsial disease is zoonosis. They are gram negative coccobacillary organisms. The cycle is maintained between the insect vector and the animal reservoir. Human infection is not the part of the cycle, but it occurs when the insect vector bites or makes contact with man in conditions dominated by poor personal hygiene and overcrowding.
It is also known as epidemic typhus fever.
The organism rickettsia prowzekii is carried by the vector body louse.
Transmission of R. prowzekii occurs when the skin wound is scratched or scrapped, with the fecal matter or the body fluid of the crushed louse.
- The onset of epidemic typhus is abrupt.
- Body ache and lassitude and headache are early manifestations.
- Thereafter the fever rises rapidly and remains constant. It is accompanied with chills.
- Face becomes flushed, the tongue is furred and the eyes turn red.
- Rash appears on the third to seventh day. It starts in the axilla and the flanks, then spreads to the abdomen and back and finally on the legs. Face, palms and soles remain free from rash.
- The rash blanches on pressure.
- Bad smell from mouth. Abdominal pain.
- Cough and constipation.
- Rapid heart rate, hypotension and cyanosis.
- Gangrene of finger and toes.
- Cerebral thrombosis resulting into coma.
- Renal failure.
- Early antibiotics are especially important in treating epidemic typhus. When the therapy is delayed until rash is hemorrhagic, the response is less dramatic.
- Therapy is continued until the patient is free from fever for 24 hours.
- Intravenous fluids may be required in patients who are unable to take medicines orally. It is also required to balance the electrolyte level in blood.
- In uncomplicated cases, the patient starts improving within 24 hours after the treatment, and fever subsides after 3 days of treatment.
- The death rate of untreated epidemic typhus (rickettsia prowzekii) is 15%.