Concurrent infections of echinostomes with helminths and protozoans

Abstract

Concomitant infection with helminths and other parasites is a frequent occurrence, due in part to the widespread distribution of helminths and chronic nature of infection. A multitude of studies have utilized echinostome parasites (Class: Trematoda) to examine the host response to coinfection, and this chapter discusses the use of echinostomes paired with (1) heterologous species of Echinostoma, (2) nonechinostome helminths, and (3) protozoan parasites in rodent models of coinfection. In general, the following trends were observed. Primary infection with echinostomes, which usually confers a high level of protection against homologous echinostome challenge, also tends to protect the infected host against heterologous echinostome challenge. Secondly, protection against echinostome challenge also appears to be induced by high-dose, patent, schistosome infection, as well as intestinal nematode infection. Finally, in contrast, primary chronic echinostome infection often enhances establishment of secondary schistosome infection, while likewise exacerbating secondary protozoan infections. These interactions are dependent on the specific host used in the experiments, the specific parasites used and their dose, and the timing of the infections in relation to each other. Moreover, these studies suggest that echinostome infection results in a complex systemic host response that exhibits both specific and nonspecific effector mechanisms, though further study will be required to fully define the mechanistic determinants that influence host response to primary echinostome infection and to coinfection with other parasites.