Rickettsia infection

Category: Illness or disabilities



Introduction and description

Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that can be present as

  • cocci (0.1 μm in diameter),
  • rods (1–4 μm long), or
  • thread-like (10 μm long).

Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells (typically endothelial cells).  Rickettsia cannot live in artificial nutrient environments and is grown either in tissue or embryo cultures; typically, chicken embryos are used.

Rickettsia species are transmitted by numerous types of arthropod, including chigger, ticks, fleas, and lice, and are associated with both human and plant disease. Most notably, Rickettsia species are the pathogen responsible for:

  • typhus,
  • rickettsialpox,
  • Boutonneuse fever,
  • African tick bite fever,
  • Rocky Mountain spotted fever,
  • Flinders Island spotted fever and
  • Queensland tick typhus (Australian tick typhus).

Rocky Mountain spotted fever  is the most lethal and most frequently reported rickettsial illness in the United States. It has been diagnosed throughout the Americas. Some synonyms for Rocky Mountain spotted fever in other countries include “tick typhus,” “Tobia fever” (Colombia), “São Paulo fever” or “febre maculosa” (Brazil), and “fiebre manchada” (Mexico). The disease is caused by Rickettsia rickettsii, a species of bacterium that is spread to humans by Dermacentor ticks. Initial signs and symptoms of the disease include sudden onset of fever, headache, and muscle pain, followed by development of rash. The disease can be difficult to diagnose in the early stages, and without prompt and appropriate treatment it can be fatal.

Typhus -  is any of several similar diseases caused by Rickettsia bacteria and carried by lice. The name comes from the Greek typhos (τῦφος) meaning smoky or hazy, describing the state of mind of those affected with typhus.


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