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

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.

Diversity of Trichobilharzia in New Zealand with a new species and a redescription, and their likely contribution to cercarial dermatitis

“…It might be that, in the absence of the preferred snail species, these schistosomes can use related species (e.g. Manzoli et al, 2021), which could be the case for T. regenti (in Europe uses R. balthica) and T. franki (in Europe uses R. auricularia) which are also found in domestic and wild ducks in Iran (Fakhar et al, 2016;Ashrafi et al, 2018Ashrafi et al, , 2021. Also, for avian schistosome species, as far as is known, rarely do species in more than one genus or family of snail serve as natural hosts.…”

“…Just in the last few years, several papers have defined and redefined the genetic diversity within Trichobilharzia relative to the reported morphological diversity. As a result, several new species or new lineages (probably new species) have been recognized (Jouet et al, 2010a(Jouet et al, , 2010b(Jouet et al, , 2015Brant et al, , 2017Kolárová et al, 2013;Devkota et al, 2014;Pinto et al, 2014Pinto et al, , 2017Fakhar et al, 2016;Ashrafi et al, 2018Ashrafi et al, , 2021.…”

“…Added to that, the avian hosts are often migratory, and the snail hosts can be common and widespread (e.g. Ebbs et al, 2016;Ashrafi et al, 2018Ashrafi et al, , 2021. Morphological features of the cercariae are not sufficient for species discrimination.…”

“…Comparative DNA sequence analysis offers a sound method for organizing and quantifying genetic diversity as a proxy for species diversity (e.g. Vilas et al, 2005;Brant et al, 2006;Jouet et al, 2010aJouet et al, , 2010bBrant et al, 2011;Aldhoun et al, 2012;Kolárová et al, 2013;Ebbs et al, 2016;Fakhar et al, 2016;Ashrafi et al, 2018Ashrafi et al, , 2021.…”

Wild bird trade at live poultry markets potentiates risks of avian influenza virus introduction in Iran

“…On different days during October 2019, swabs were taken from 396 individuals from four different species of wild migratory aquatic birds, all traded at different LBMs of Ferydunkenar city, Mazandaran province, Iran. The province borders the south coast of the Caspian Sea and provides resting and/or wintering sites during fall and winter for migratory waterbirds along several migratory flyways [ 18 ]. Swab samples were collected from mallards ( Anas platyrhynchos , n = 96 cloacal swabs), Eurasian teal ( Anas crecca , n = 100 cloacal swabs), Eurasian coots ( Fulica atra , n = 100, comprising 40 oropharyngeal and 60 cloacal swabs), and greater white-fronted geese ( Anser albifrons , n = 100 cloacal swabs).…”