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Overseas information: www.cdc.gov/ncidod/diseases/Index.htm
An infection caused by one of five species of the
Schistosoma infections are contracted when humans are
in contact with contaminated water. The parasite in its infective stages is called a
cercariae and swims freely in open bodies of water. On contact with humans, the parasite
burrows into the skin, matures into another larval stage (schistosomula) then migrates to
the lungs and liver, where it matures into the adult form. The adult worm then migrates to
the anatomic area of its preference, depending on which species is involved. Likely areas
include the bladder, rectum, intestines, liver, portal venous system, spleen, or lungs. It
can also be contracted by ingesting untreated water or salads that have been washed in
Clinical presentation of schistosomiasis varies with the
species of worm. Initial invasion of the skin may cause itching and a rash (swimmer's
itch). Heavy infestation may cause fever, chills, lymph node enlargement, and liver and
spleen enlargement. Urinary symptoms may include frequency, painful urination (terminal dysuria)
and blood in urine (haematuria). Intestinal symptoms include abdominal pain and diarrhoea
(which may be bloody). Worldwide this is a common illness thought to affect more than 200
- 3 clinical entities (all or none may occur)
i) cercarial dermatitis - local - within days
ii) acute febrile illness (Katayama fever) - usually between 4-8 weeks
iii) chronic illness - after 3 months
- may have diarrhoea, abdominal pain, haematuria
- investigations (see serology & eosinophilia sections)
Travellers at risk from this infection are those who bathe in streams, rivers, or
lakes, or who indulge in water sports in fresh-water areas. Some areas are especially
risky; the Nile valley and in Africa, Lake Victoria, the Tigris and Euphrates river
systems, and artificial lakes such as Lake Kariba in Zimbabwe and Lake Volta in Ghana and
many parts of Asia. There is a sign at Lake Malawi that proclaimes that it is safe to
swim. It definitely is not! - Nb. All waterways in Africa are infected.
Since the larvae die quickly on removal from water and
cannot survive drying, quick drying of exposed skin and removing wet clothing and swimwear
and vigorously rubbing oneself down with a towel immediately after leaving the water may
reduce the risk. Swimming for short periods in flowing rather than still waters, avoiding
the early and late parts of the day also will reduce the risk. When schistosomiasis occurs
in one or more members of a travelling party, the proportion of those in the party
infected is high (between 30% and 60%).
- Investigations: - Serology for all
returned travellers from Africa and other risk areas who swam, waded or walked in
streams or lakes. Schistosoma eggs can be ingested via contaminated water.
- Check for Eosinophilia - early seroconversion within weeks but may be delayed for up to
few false negatives after 3 months
some false positives occur
- Other tests include Faeces for eggs & Terminal urine x 3 for microscopy
- Consider Empirical treatment: Praziquantel 40mg/kg/d for 3 days gives 95% cure rate with no
relapses Treatment before significant damage or severe
complications usually produces good results.
Information mostly taken from: "International
Travel and Health" (WHO year book -
Australian Immunisation Handbook, 8th Edition - 9/2003 - Part1 - Part 2 & Part 3 (large pdf
Centre for Disease Control, USA - www.cdc.gov/travel Travel Health Seminar Oct 96, June 97,Feb 98, March 99, May 2000, August 2002 &
March 2005 - Victorian Medical Postgraduate Foundation.
Manual of Travel Medicine,
Melbourne, Oct 2004.
Updated 06/09/2006. Additional references & disclaimer.