Interrelationship between schistosomiasis and concomitant diseases.

The biological literature contains many examples of mutual influences between different species of parasites, especially with respect to concomitant helminth infections. Several situations are known in which the association of infection by Schistosoma mansoni with other pathogens in the same host results in a type of disease which differs from the simple summation of the individual effects of each infection. The present study concerns concomitant infections involving S. mansoni and enterobacteriaceae; S. mansoni and other helminths such as Ascaris lumbricoides, Ancylostomids, Toxocara canis and species of the genus Hymenolepis; S. mansoni and different protozoa such as Trypanosoma cruzi, T. brucei, Toxoplasma gondii and Plasmodium berghei. The interaction between hepatitis B virus and S. mansoni, leading to prolonged viremia and worsening of liver damage, is also discussed. The paper also treats the simultaneous occurrence of schistosomiasis and other aggravating factors such as malnutrition and neoplasias which may alter the host's response to the trematode.