|
Synonyms
- Schistosome dermatitis or Bilharziella dermatitis, Swimmer’s itch, Bather’s dermatitis, Clam digger’s itch
Type of zoonosis
Definition
- It is caused by cercariae of Schistosomes, characterized by development of cercarial dermatitis (immediate hypersensitivity reactions) with intense itching and development of red spots at the site of skin penetration, but resolve spontaneously within 10 to 24 hours.
Etiology
- It is caused by cercariae of avian Schistosomes (genera Bilharziella, Ornithobilharziella, Microbilharziella, Trichobilharziella, Gigantobilharziella and Australobilharziella) belong to the family Schistosomatidae or of nonhuman mammals (genera Schistosoma, Schistosomatium, Orientobilharzia and Heterobilharzia).
Reservoir and incidence
- Distributed worldwide.
- Definitive hosts: Geese, ducks, water fowls, domestic and wild mammals, such as raccoons and rodents.
- Sources of infection are in and around fresh water or salt water bodies, where snail activities are more.
- Swimmers, clam-diggers, washermen, fishermen and rice-field workers are most likely to be exposed to cercariae.
- People contract infection through recreational and occupational activities.
Transmission and life cycle
- Eggs (contains miracidium) are voided in the faeces of definitive host or urine.
- Miracidium liberated in the water and swims till it attaches with an intermediate host (snails such as Bulineus, Lymnea, Planorbis).
- Miracidium develops into sporocyst, which develops into redia, and then into cercaria. Unlike the cercariae of other trematodes, schistosomes do not form metacercariae.
- The cercariae swim in the water and die if they fail to find a host within 24 hours.
- Cercariae invade the host body by skin penetration and undergo histological changes in their tegument, becoming juvenile parasites, called schistosomula.
- Schistosomula penetrate into blood circulation and lymphatics, and reach the lungs, where they remain for several days. Then, they reach the liver, where they mature and mate. Finally migrate to their final site and start to lay eggs.
Disease in animals
- The occurrence of cercarial dermatitis animals is less significant than man.
Disease in man
- Aberrant migration of cercariae through skin penetration develops cercarial dermatitis, which causes allergic reactions (early hypersensitivity reactions). IgE antibodies are predominant a week after cercarial dermatitis.
- Symptoms include intense itching and development of macules / red spots at the site of penetration of cercariae, but vanish within 10 to 24 hours. Scratching of skin macular rash may result in secondary bacterial infection.
Diagnosis
- Based on history of recent exposure to water sources and clinical signs.
- Serology by ELISA to measure IgE antibodies, which is presumptive and should be compared with history and clinical sign.
Treatment
- Symptomatic treatment should be provide.
Preventin and control
-
Praziquantel @ 22.5 mg per duck or water fowl is effective against adult parasite, if given during the pre-patent period.
-
Rice-field worker can apply copper oleate cream of dimethyl phthalate cream on their skin before getting in to the field.
-
Swimmers should dry off their skin immediately after bathing to avoid skin penetration of cercariae.
-
Control of snail population using molluscicides.
|
Participants