Once infected, snails shed cercariae for the rest of their lives. Once in fresh water these eggs hatch, releasing another type of larvae that are attracted to specific aquatic snails where they multiply many times to produce thousands more cercariae. If the cercariae invade the correct host they mature into adult worms and produce eggs that escape from the host in the faeces. They emerge from aquatic snails during the summer months and, using their forked tails, swim in search of their next host, usually a water bird, and burrow into exposed skin. ![]() ![]() The parasites that cause swimmers itch are the larval stages, or cercariae, of flatworms of the schistosome genus Trichobilharzia. Incidences of infection are now increasing worldwide and swimmers itch is now regarded as an emerging infectious disease. In addition to its medical label of cercarial dermatitis, it is also known as: duck rash, clam digger’s itch or lake itch in the US, duck lice in Canada, pou du canard in Switzerland and rice paddy itch in rice growing areas. Swimmer’s itch was first described in 1928 in Michigan, US and incidences have since been recorded worldwide. But beware, minuscule parasites may be lurking in seemingly tranquil waters ready to burrow into exposed skin and cause an extremely itchy rash to develop. Image from wikimediaįor those in the northern hemisphere, summer holidays are upon us and with them comes the pleasure of taking part in fresh water sports.
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