Studies on bilharziasis endemicity in the vicinity of Basra, Iraq.

This paper reports on investigations into the distribution of snail genera and possible limiting environmental factors in the endemic and non-endemic areas of human bilharziasis in and near Basra, carried out in 1958 by the WHO Bilharziasis Control Project staff in Iraq. These investigations confirmed the existence of an abrupt line of demarcation between these areas immediately south of Basra.During June and October 1958, the known intermediate snail host, Bulinus truncatus, was not found in canals bordering on areas of either infected or non-infected human populations. From these findings and the evidence of previous investigations it is concluded that in southern Iraq, and particularly in Basra, B. truncatus has been demonstrated with difficulty, if at all. Nevertheless, transmission has continued to take place. Explanations of this apparent phenomenon are discussed and it is concluded that populations of B. truncatus may be completely absent for several years and that other snail genera may play a role in transmitting the disease.A study of environmental factors indicates that water velocities, salinity, turbidity, and pH in the endemic and non-endemic areas showed no significant differences, but that the continuous change in water flow may be a factor limiting B. truncatus colonization.It is also concluded that the salinity in the Shatt al Arab River originates from Lake Hammar and is not introduced from the Persian Gulf by tidal wave, as has been previously believed.