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Cryptosporidiosis and Microsporidiosis
  1. R C G POLLOK

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Cryptosporidiosis and Microsporidiosis. Edited by F Petry (Contributions to Microbiology, vol 6), (Pp 268; illustrated). Switzerland: Karger, 2000. ISBN 3805570503.

There is a great need to raise the profile of parasitic diarrhoeal disease, and this book serves the cause well. World wide the prevalence of Cryptosporidium among individuals with diarrhoea is approximately 5%. The common notion that cryptosporidiosis is purely a disease of the immunocompromised is wrong. Since the well publicised Milwaukee outbreak in the USA, affecting 420 000 individuals, large waterborne outbreaks of cryptosporidiosis repeatedly occur at an alarming rate despite “state of the art” water treatment facilities, illustrated by two examples. In 1998, Sydney water supplies became heavily contaminated withCryptosporidium leading to a full scale enquiry by the Australian government. A large outbreak occurred in London and Hertfordshire in 1997, affecting a population of half a million water users, resulting in the issue of a public notice to boil drinking water. Largely as a consequence, the government recently commissioned the Bouchier report onCryptosporidium and water supplies which emphasised the need for better outbreak investigation in the future (www.dwi.detr.gov.uk/pubs/bouchier).

In the developing world, parasitic disease contributes heavily to the burden of diarrhoeal disease. Malnourished children are especially at risk of increased morbidity and mortality, both HIV negative and positive, from cryptosporidiosis and microsporidiosis. Twenty to forty per cent of HIV positive individuals in the developing world develop cryptosporidiosis or microsporidiosis. In addition to slowing retroviral progression, HAART has emerged as the best treatment for opportunistic infections. Sadly few people with AIDS in the developing world have access to antiretroviral therapy.

For these reasons Cryptosporidiosis and Microsporidiosis is a timely reminder of the importance of these infections providing an authoritative up to date summary of the many recent developments in the field. Franz Petry, the editor, has done well to bring together a panel of authors with an international reputation in their subjects.

Tzipori and Widmer as well as Morgan and colleagues put forward evidence for two distinct genotypes of C parvum: a “human-type” which may infect only humans or immunocompromised animals, and an “animal-type” which may infect both humans and a range of animals. This has important applications in the molecular epidemiological characterisation of samples collected during waterborne outbreaks. For example, almost all isolates tested from the London/Hertfordshire waterborne outbreak were of human origin, suggesting failure of water treatment. Petry summarises the diagnostic approaches for the identification of C parvum infection. Particularly of interest is the recent development of ELISA for the detection of serum antibodies toC parvum immunodominant antigens. The technique appears to be both more sensitive and specific than ELISA using crude oocyst antigen but has yet to be fully evaluated. Farthing emphasises the clinical importance of childhood infection in the developing world and flags up new therapeutic agents, including nitazoxanide, which has good efficacy and is likely to be an affordable option in the tropics. McDonald and coworkers review developments in our knowledge of the host immune response toCryptosporidium highlighting the role of T cell mediated responses. Work by the author has revealed the central role of interferon γ production by intraepithelial lymphocytes in the control of infection. Strong and Nelson tackle new developments in gene discovery of C parvum. Using a combination of characterisation of expressed sequence tags and the use of “HAPPY” mapping technology, approximately 30% of theC parvum genome has been surveyed. A full scale genome mapping project is needed to allow comparison with the better characterised related parasitesToxoplasma andPlasmodium.

Topics relating to microsporidiosis are similarly covered. Weber and colleagues review diagnostic methods although information on the relevance of this infection in the tropics, where most disease now occurs, is limited. Our knowledge of the immune response toMicrosporidium is relatively limited but as with Cryptosporidium, Didier points out the importance of interferon γ mediated T cell responses in control of infection. Deplazes describes the epidemiology of microsporidial infection. Interestingly, several different genotypes ofEnterocytozoon bieneusi have been identified but their phenotypic difference remains uncertain.

This book is an invaluable resource for workers with an interest in the field, my only regret, particularly for research students, is its hefty price.

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