Descriptive study of Fascioliasis in Mazandaran province from seasonal transmission point of view

Introduction: About 2.400.000 human cases in 61 countries and 180000000
people at Fascioliasis infection risk, show the importance of human aspects of
Fascioliasis around the world. In the north of our country (Iran) huge outbreaks
of Fascioliasis have been seen and up to 10000 people have been infected with
Fascioliasis in one of these outbreaks. So this study tries to show better criteria
about the seasonal fluctuations of infection in the north of Iran. This descriptive
study is based on comparison between intermediate host population peak and peak
of human cases outbreak.
Methods: In this descriptive study population of snails were checked monthly in
6 selected colonies in different climatic areas for a year. In this study we
calculated average of snails in a 20×20 cm scoop each month.
Study of human cases of Fascioliasis was performed for better understanding of
its epidemiological aspects, so all files for Fascioliasis in Mazandaran province
Health center were checked out.
Results: Three species of Lymnaeid snails were found in Mazandaran provine:
Lymnea palustris, Lymnea truncatula and Lymnea auricularia (gedrosiana). The
Lymnea truncatula the main intermediate host for human and animal Fasciola
hepatica and L. gedrosiana act as intermediate host for human and animal
Fasciola hepatica and L. gedrosiana act as intermediate snail host of F. gigantica.
With respect to Lymnaeid snails population dynamics, we noted that the
maximum of L. truncatula snail host of F. hepatica may be seen from August to
January and for Lymnea auricularia (gedrosiana) the peak is in summer.
The results from Mazandaran province health center show that totally 107 human
infections have been reported in the last 4 years and most cases have referred to
the health center in early winter.
Conclusion: By considering the peak of snail population in mid and late summer
and peak of human cases in late winter it is probable that transmission occurs in
early autumn.