Emerging parasite zoonoses: the role of host-parasite relationship

Human-parasite relationships have played an essential role in the emergence or re-emergence of some parasitic diseases. These interactions are due to numerous causes. Some are linked to humans (immunodeficiencies due to AIDS among other causes, treatments, nosocomial contaminations, genetic predispo sition), others concern the parasite (particular genotypes having modified their parasitic specificity). Several of these causes were predominant in t he emergence of parasitoses such as cryptosporidiasis, microsporidioses or, to a certain point. pneumocystosis, the transmission of which has become z oonotic or even anthroponotic, inter-human. Re-emergent diseases (toxoplasm osis, leishmaniasis, giardiasis. strongyloidiasis, scabies) had already bee n described in human pathology, but their frequency or symptomatology have been drastically modified. In this case also, the unbalanced host-parasite relationship is largely responsible but it can not be dissociated from othe r causes, especially environmental and nutritional. (C) 2000 Australian Soc iety for Parasitology Inc. Published by Elsevier Science Ltd. All rights re served.