Rickettsial diseases: the typhus group of fevers—a review
- University of London—North Thames, 33 Millman Street, London WC1N 3EJ, UK
- Dr Cowan, Dean of Postgraduate Medicine (e-mail:gcowan{at}tpmde.ac.uk)
- Received 24 March 1999
- Accepted 13 August 1999
Epidemic louse borne typhus has historically caused massive mortality in the wake of war, famine, and great migrations.1 In the four years from 1918 in Eastern Europe and Russia there were up to 30 million cases, and three million deaths. In the recent past in Burundi typhus has infected prison inmates before spreading to the wider community.2 It remains a risk among refugee populations in all parts of the world, despite its omission from a recent review of health care in refugee camps.3
Tick borne typhus is a significant risk to human health, especially in the Eastern United States, Brazil, the Mediterranean basin, the African veld, India, and Australia. Endemic flea borne typhus occurs sporadically wherever rats and man live closely together. Scrub typhus is a hazard in many parts of South East Asia and beyond, and is the first of the rickettsial infections to show evidence of resistance to standard antibiotics.4 No useful vaccines are currently available for any of the rickettsial infections.
Pathogenesis
The rickettsiaceae are a family of obligate intracellular small Gram negative coccobacilli which infect humans chiefly through insect vectors, mostly from animal hosts, but sometimes by transovarial transmission in the insects themselves.5
The genus Rickettsia is divided into:
(1) R prowazekii, the agent of classical epidemic typhus, transmitted by the human body (clothing) louse,Pediculus humanus (but not by head lice) from active human cases or from healthy carriers or subclinical cases, so-called Brill-Zinsser disease.6 Typical circumstances were evident in the Burundi outbreak,2 which started in a prison at N'Gozi in 1995 and spread to the malnourished inhabitants of refugee camps in the central highlands (over 1500 m), causing over 50 000 cases with a mortality of 2.6%. The infectious agent in the faeces of the body louse is …
