Migratory routes, domesticated birds and cercarial dermatitis: the distribution of Trichobilharzia franki in Northern Iran.

Keyhan Ashrafi,Meysam Sharifdini,Abbas Darjani,Sara V Brant

doi:10.1051/parasite/2020073

Abstract

Background: One of the major migration routes for birds going between Europe and Asia is the Black Sea-Mediterranean route that converges on the Volga Delta, continuing into the area of the Caspian Sea. Cercarial dermatitis is a disorder in humans caused by schistosome trematodes that use aquatic birds and snails as hosts and is prevalent in areas of aquaculture in Northern Iran. Before the disorder can be addressed, it is necessary to determine the etiological agents and their host species. This study aimed to document whether domestic mallards are reservoir hosts and if so, to characterize the species of schistosomes. Previous work has shown that domestic mallards are reservoir hosts for a nasal schistosome. Results: In 32 of 45 domestic mallards (Anas platyrhynchos domesticus) (71.1%), the schistosome Trichobilharzia franki, previously reported only from Europe, was found in visceral veins. Morphological and molecular phylogenetic analysis confirmed the species designation. These findings extend the range of T. franki from Europe to Eurasia. Conclusion: The occurrence of cercarial dermatitis in Iran is high in areas of aquaculture. Previous studies in the area have shown that domestic mallards are reservoir hosts of T. regenti, a nasal schistosome and T. franki, as shown in this study. The genetic results support the conclusion that populations of T. franki from Iran are not differentiated from populations in Europe. Therefore, the schistosomes are distributed with their migratory duck hosts, maintaining the gene flow across populations with compatible snail hosts in Iran.

Highlights

One of the major migration routes for birds going between Europe and Asia is the Black Sea-Mediterranean route that converges on the Volga Delta, continuing into the area of the Caspian Sea
From our collection of 45 ducks from 45 localities in 16 districts, Trichobilharzia franki Müller and Kimmig, 1994 was found at 32 sites in 12 districts; worms were found in the liver of 32/45 ducks, with 71.1% prevalence (Table 1)
Because this study continues the efforts of Ashrafi et al [6], some of these ducks were infected with both T. franki and the neuropathic nasal species, T. regenti

Summary

Introduction

One of the major migration routes for birds going between Europe and Asia is the Black Sea-Mediterranean route that converges on the Volga Delta, continuing into the area of the Caspian Sea. The water that is used for plants, ducks, fish, or crustaceans and other invertebrates is often inhabited by aquatic gastropods that can host a myriad of trematodes. Both domestic and wild mammals and birds use the water, as do humans, creating many opportunities for life cycles of several species of parasites to establish. One of these life cycles can result in a disorder called cercarial dermatitis (CD) or swimmer’s itch [41], caused by digenetic trematodes in the family Schistosomatidae. It is more manageable to control one duck species in the life cycle than all duck species, so more specific knowledge facilitates control or mitigation of the disease

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Conclusion