A New Trend in Cholera Epidemiology

Abstract

Since 1962 classical cholera has been limited to India and Pakistan ; but cholera El Tor, which began to spread in pandemic form after 1961, is involving increasingly large areas in the West Pacific region and South and South-East Asian countries. It is rapidly extending to areas in India and Pakistan, where classical cholera was already endemic, and in many of these areas it has progressively displaced cases due to classical cholera. Laboratory experiments to study the interaction of V. cholerae and V. eltor have shown that in mixed cultures V. eltor is capable of eliminating V. cholerae within a short time both in vitro and in vivo. These findings provide a possible explanation of the observed alteration in the pattern of cholera outbreaks in the Indo-Pakistan subcontinent. Because of the greater epidemic and endemic potentialities and speed of dissemination of cholera El Tor there is a likelihood that in the near future El Tor infections may spread further westward to the Middle East countries and from there to Southern Europe. Consequently it is suggested that containment measures, particularly the organization of mobile diagnostic and treatment services, should be undertaken in the threatened areas in anticipation of possible outbreaks. As V. eltor is now the causative organism of cholera in most areas, and since a better degree of protection is obtainable with vaccines made of El Tor vibrios, it is suggested that more emphasis should be placed on El Tor vaccine than on the classical cholera vaccine. Most of the observations relating to spread of El Tor infection in India and other countries were made during the course of phage-typing of vibrio strains referred to our Centre from various laboratories. Our grateful thanks are due to the workers and chiefs of these laboratories for their valued co-operation. We are particularly thankful to the World Health Organization and the Health Directorate of the Government of India. Owing to their sustained help we have been able to follow up regularly the progress of cholera infection in different areas. We are indebted to Dr. K. Patricia Carpenter, Director, International Shigella Centre, London, for opportunities of testing the El Tor strain isolated in Bahrain and for providing the relevant information concerning the patient. The annual incidence of cholera cases in Calcutta was supplied by the Office of the Director of Health Services, New Delhi. Dr. A. Narayanaswami, a colleague in the Institute, deserves our gratitude for his helpful suggestions. © 1965, British Medical Journal Publishing Group. All rights reserved.