TDK conference 2020

Cercarial dermatitis in humans is a re-emerging zoonotic disease. This illness is caused by the infectious larvae of avian blood flukes in the Schistosomatidae family that penetrate human skin in water. In non-definitive hosts the larvae of the parasite (i.e. cercariae) die within hours leading to topical inflammation of skin. Repeated invasion of cercariae cause vesiculo-maculo-papular skin eruptions accompanied by intensive itching. Avian schistosomes are present worldwide and consequently are the subjects of many local and international research projects. In Hungary there are hardly any scientific articles published on this topic. Even the diversity and range of such species residing in the country is yet unknown, although the occurrence of cercarial dermatitis in Hungary has been proven.

In this study the head and viscera of 68 mallards (Anas platyrhynchos), 2 green-winged teals (Anas crecca) along with 1 ferruginous duck (Aythya nyroca) were examined from 12 regions of 9 different counties of Hungary between September 2018 and September 2020. Based on morphological analysis, we were able to identify the schistosomid species Bilharziella polonica and Dendritobilharzia pulverulenta, which are well-known causative agents of cercarial dermatitis. In addition, at least two species of the genus Trichobilharzia were found that had not yet been described in Hungary. Their precise identification will only be possible after their molecular examination. Comparing the results of birds from different locations, we showed a significant difference between the infection of wild duck populations and the infestation of those flocks of birds which are reared for hunt.

Furthermore, 122 European ear snails (Radix auricularia) were collected from an urban pond in Hungary. Although the infectious larvae responsible for cercarial dermatitis were only found in one snail, this finding proves that the life cycle of these parasites can be realized even in an urban environment as long as the pond is regularly visited by waterfowl.

Based on our results we can ascertain that avian schistosomes, which are responsible for recurring problems in numerous European countries, can also be found in Hungarian waterfowl. It is possible that the people can count on the occurrence of cercarial dermatitis in any type of water what these birds visit.