Paragonimiasis in Ecuador: prevalence and geographical distribution of parasitisation of second intermediate hosts with Paragonimus mexicanus in Esmeraldas province.

To determine whether the human cases of pulmonary paragonimiasis detected in the province of Esmeraldas were autochthonous a total of 1,457 freshwater crabs, species Hypolobocera aequatorialis, were collected from 45 different streams in 4 cantons to determine the rate of parasitisation with metacercariae of Paragonimus mexicanus. Some 28 (62.2%) streams were found to harbour parasitised crabs, with 76.5% of the streams in canton Quininde infected, followed by those in Muisne, 72.7%, Esmeraldas, 62.5% and Eloy Alfaro 22.2%. Of the 1,043 crabs studied from these 28 streams, 42.6% (444) were found to be parasitised with metacercariae: 45.1% of the crabs in the streams in the canton of Quininde, 43.9% in Muisne, 37.4% in Esmeraldas and 13.2% in Eloy Alfaro. There was a positive correlation between the crab parasitisation and the increasing size of their carapace. The results indicate that there is potential active transmission of disease in the four cantons in the province of Esmeraldas and that the human cases detected are probably autochthonous.