Human oesophagostomiasis in Ghana: a study on the adaptation of a zoonotic infection to man.

The research proposal attempts to characterise the parasites of man and monkeys and to identify the differences. Morphological and, more importantly, molecular tools will be used: PCRlinked restriction fragment length polymorphism (PCR-RFLP) and PCR-coupled single strand conformation polymorphism (PCR-SSCP), to screen for sequence variation in the first and second internal transcribed spacer (ITS-1 and ITS-2) of ribosomal DNA, and in the mitochondrialDNA. Promising regions will be sequenced. Human oesophagostomum infections are mostly thought to be rare zoonotic accidents, but in northern Ghana and Togo the parasite is well established in man and it is estimated that in this region at least a quarter of a million people are infected. The infection is the cause of serious pathology and is recognised, even by the local population, as an important cause of disease and morbidity. Recent studies now seem to suggest that the strain or species infecting humans is different from the one infecting monkeys. Did the monkey parasite adapt to the human host? And if so, how can both parasites be differentiated? Is there a risk of further expansion of the strain that adapted to man? Indeed, many details on the life cycle, the route of transmission, and the identity of the parasite in humans are still lacking. The situation in Ghana offers unique opportunities since areas occur in which both the humans and the monkeys are heavily infected. In other villages monkey infections are common while human infections are not apparent in spite of intense contacts between the humans and monkeys. In the present research proposal field studies are described on behavioural interaction between humans and monkeys, along with laboratory studies on the similarity and on the differences of their worms.