Leishmaniases are among the important public health problems facing populations in the tropical and subtropical world. The wide diversity of the state of the disease and its epidemiology contributes greatly to the difficulties experienced in the control or management of the leishmaniases. Each focus of the disease calls for specific control or management strategies. Furthermore, the knowledge of the true prevalence of the disease and the extent to which it is responsible for human suffering and invalidity is lacking. However, our current knowledge of this disease indicates that it is on the increase.

Antigenic variation is a mechanism exploited by parasitic protozoa to evade the host's immune response. Studies on such variation are of cardinal importance in approaching the practical problems of vaccine design and diagnosis of infection by serological tests. Coincidently these studies have revealed novel gene expression mechanisms which are of fundamental biological interest (Vickerman and Barry, 1982). The African (salivarian) trypanosomes all exhibit antigenic variation and the process has been studied in Trypanosoma brucei subspecies in particular.

The first paper of this symposium was presented by Y. Tsukii (Hosei, Univ.) under the title of ‘Genes controlling the specificity of mating type and matingtype-substance interactions in Paramecium.’

Sexual reproduction in the ciliate Paramecium caudatum is initiated by ciliary agglutination (mating reaction) between cells of complementary mating types, E and O. This initial cell contact involves specific macromolecules called the ‘mating-type substances’, proteins associated with ciliary membranes. Although they have eluded all attempts at isolation, genetic approaches are disclosing their structural characteristics.

The workshop held in Mombasa was an extremely successful one and for some participants a highlight of their Congress activities. Those participating were: Dr John J. Lee, Department of Biology, City College of CUNY; Dr Rudolf Rottger, Institut fur Allgemeine Mikrobiologie, Universitat Kiel; Dr Stanislaw Dryl, Department of Cell Biology, Nencki Institute (Poland); Mr Mrinal Ghosh, Department of Marine Science, Calcutta University; Dr Leonard Otieno, International Centre for Insect Physiology and Ecology; Dr Pamela and Dr Robert Hallock, Department of Marine Science, University of South Florida; Dr Wolfgang Lutkin.

Our knowledge of tropical African protozoa is limited to the extensive studies on ciliates by Dragesco (1980, 1985) and a study of plankton in Lake Tanganyika by Hecky et al., (1978) and Hecky and Kling (1981). No intensive study of freshwater protozoa had been previously undertaken in Kenya and for this reason a post-congress freshwater workshop under the dual leadership of Dr Stuart S. Bamforth (U.S.A.) and Dr Colin R. Curds (U.K.) was held at Kisumii, a town situated on the shores of Lake Victoria. The opportunity was taken to visit Lakes Naivasha and Nakuru en route to Kisumu. In addition a smaller saline lake, Lake Simbi near Kisumu was visited by some participants which enabled a comparison of two saline and two freshwater lakes to be made as well as a study of some stream sites.