Contributions on human fascioliasis and its snail intermediate host in Nile Delta, Egypt

Abstract

The present study spotted some light on human fascioliasis in Kafr El-Sheikh Governorate in the west of the Nile Delta in Egypt, its species, its intermediate host (IMH) snail and tried to answer previous questions about development of Fasciola (F.) species in new snail hosts other than that known for animal fascioliasis in Egypt. The study recorded a percentage of infection by Fasciola eggs reached up to 6.02% in 1810 randomly collected human stool samples from 6 climatically selected sites in this governorate using fluke-finder technique. The incidence was high in Sedi Salem and Motobus than in the other study sites. Micrometry measuring of 100 eggs from each locality showed that egg size cannot be used as a main criterion in differentiation between F. hepatica and gigantica. Wide range of egg size varied between 130-162.5 µ X 75-87.5 µ with a mean length and width of 144.24 ± 11.33 µ X 80± 6.55µ, was recorded. Upon dissection of 1972 Lymnaea (L.) cailliaudi, 268 L. alexandrina, 502 Bulinus species, 11316 Biomphalaria alexandrina, 1398 Cleopatra species, 8520 Physa acuta, 420 Melania tuberculata, 2132 Vivipara (Bellamya) unicolar, 144 Neritina nilotica and 1570 Planorbis philippi, Fasciola parthenitae were not detected in snails other than L. cailliaudi (the known IMH of Fasciola in Egypt). The results proved that there is no accommodation has occurred in any of the surrounding snails to transmit Fasciola to man. The present study proved that human fascioliasis in the study sites was due to Fasciola gigantica not F. hepatica. This appeared in its tendency to develop in L. cailliaudi not in other tested snails with successive radial generations as that described previously for F. gigantica. Moreover, early mature flukes extracted from laboratory infected rabbits by the produced encysted metacercariae had the characteristic features described previously for F. gigantica.

An overview of cercariae from the Egyptian inland water snails

“…Radix natalensis (R. natalensis) snails were reported to be naturally infected with cercariae belonging to the genus Fasciola [14,18,27,35,42,45,[47][48][49][50][51]. Results of experimental infection confirmed the susceptibility of this snail species to be infected with F. gigantica [52] and F. hepatica [52,53].…”

“…B. unicolor snails were reported to be naturally infected with cercariae belonging to the genus Eumegacetes (Family Eumegacetidae) [81], and unidentified species of stylet cercariae [14,49,50,82].…”

“…B. truncatus snails were reported to be naturally infected with cercariae of Lepoderma ramlianum [15,21,72,76,83,84], and unidentified species of stylet cercariae [7,14,26,27,[29][30][31][32]34,40,42,49,50,60,83,[85][86][87].…”

“…6. H. acuta snails were reported to be naturally infected with unidentified species of stylet cercariae [14,49,50].…”

“…Infection with Paramphistomum cervi cercariae were reported by some authors [76,108,109], but these reports are doubtful because the presence of the species Paramphistomum cervi in Egypt is doubtful [95,[110][111][112]. Many authors reported unidentified species of paramphistomoid cercariae from B. truncatus snails [21,26,27,[29][30][31]34,40,42,49,50,60,95].…”