SCHISTOSOMIASIS: Global epidemiology
CALL FOR REVISION
The WHO Expert Committee Report of 1993 endorsed the estimates of 200
million persons infected among 600 million persons at risk in 74 countries
(WHO, 1993). The recent attempts at estimating the distribution and
prevalence of schistosomiasis have been published since 1981.
The estimates of the number of persons infected and the number of
persons at risk has not changed since the mid 1970's. The dynamics of this
"static" data include 1) increased population growth in the most affected
countries, particularly in Africa; 2) increased risk in water resources
development projects, again particularly in Africa and 3) lack of resources
for control in the most affected countries. In relation to the total
population, the prevalence has decreased; in relation to the population at
risk, the prevalence has remained stable. This later statement is inaccurate.
The number of endemic countries has varied between 73 and 76 since 1980.
Montserrat was removed from the list of endemic countries in 1993. Japan and
Tunisia will eventually be removed since no new infections have been reported
since 1977 and 1984 respectively. The fusion of Yemen and Democratic Yemen
reduced the count as well.
There have been other changes reported in the WHO Weekly Epidemiological
Record - the official record of epidemiological change: S. mansoni has now
been reported in Guinea Bissau, Mauritania and Somalia. S. haematobium is
present in Sao Tome. S. intercalatum has been reported in Mali and in
Equatorial Guinea. The geographical extent of change is usually incompletely
reported.
WHO is now in the process of a complete reevaluation of the global
distribution of schistosomiasis using, if available more precise
geographically coordinated data from provincial and district level. Desktop
Mapping/GIS software will be used to manage the database.
We would like to encourage you to join WHO and its Regional Offices in
this effort of reassessment. Your comments and contributions should be sent
to Dr. Isabelle Nuttall at nuttalli at who.ch with a copy to me. Many thanks for
your collaboration. Schistosomiasis control is everybody's business!
Ken Mott
Chief, Schistosomiasis Control
Divison of Control of Tropical Diseases
WHO/OMS
CH 1211 Geneva 27, Switzerland
Direct telephone: 41-22-791-3862
Secretary (Ms. Josie Mercado) telephone: 41-22-791-3898
Direct fax: 41-22-791-4869
WHO fax: 41-22-791-0746
Email INTERNET: mott at who.ch
X.400 mail: S=mott/C=ch/A=arcom/P=who/O=whohq
REFERENCES:
Doumenge J-P, Mott KE, et al. CEGET/WHO Atlas of the Global Distribution of
Schistosomiasis. Presses Universitaires de Bordeaux, 400 pp. (1987)
Iarotski LS and Davis A. The schistosomiasis problem in the world: results
of a WHO questionnaire survey. Bulletin of the World Health Organization 59:
115-127 (1981).
Utroska JA, Chen MG, Dixon H, Yoon S, Helling-Borda M, Hogerzeil HV, Mott KE.
An Estimate of Global Needs for Praziquantel Within Schistosomiasis Control
Programmes. WHO unpublished document WHO/SCHISTO/89.102 92 pp. (1989).
World Health Organization. The Control of Schistosomiasis. Second Report of
the WHO Expert Committee. Technical Report Series no. 830, 86 pp. (1993).
