History

Fact Explanation
Skin rash Cercarial dermatitis, also known as swimmer's itch, is an itchy allergic reaction caused by larvae of Schistosoma cercariae parasites in class trematoda that enter the skin. Swimmer's itch develops on exposed areas of the skin after contact with these larval forms when they mistakenly penetrate the person's skin rather than its usual host, a duck. The rash does not occur following the initial contact. Repetitive exposure develop a stronger hypersensitivity reaction. Initial itchy or tingling sensation usually settles quickly, leaving the infected individual with tiny red spots at the sites of larvae penetration. After several hours those red spots develop into papules (raised bumps) or hives (a rash of round, red , itchy weals). Within the next 1-2 days they blisters (a small bubble on the skinfilled with watery liquid) develop which may spontaneously resolves with time. [1,2,3,4,5]
Itching As the larvae of schistosoma enters the exposed skin a itchy or tingling sensation appears. But this settles within 1-2 hours. After few hours of asymptomatic period, an acute onset itching reappears in a more extensive form due to the allergic reaction. Abrasions caused by severe itching can predispose to secondary bacterial infections. [1,2,3]
Population at risk Individuals who go often for swimming in lakes and rivers where migrating aquatic birds inhibits have a risk of getting exposed. The infestation is more common in the hot summer weather. It is more common among children who does not wear swimming suits.[1,2,3]
References
  1. FARAHNAK A, ESSALAT M. A study on cercarial dermatitis in Khuzestan province, south western Iran. BMC Public Health [online] 2003 Nov 7:35 [viewed 26 July 2014] Available from: doi:10.1186/1471-2458-3-35
  2. BRANT SV, COHEN AN, JAMES D, HUI L, HOM A, LOKER ES. Cercarial dermatitis transmitted by exotic marine snail. Emerg Infect Dis [online] 2010 Sep, 16(9):1357-65 [viewed 26 July 2014] Available from: doi:10.3201/eid1609.091664
  3. LéVESQUE B, GIOVENAZZO P, GUERRIER P, LAVERDIèRE D, PRUD'HOMME H. Investigation of an outbreak of cercarial dermatitis. Epidemiol Infect [online] 2002 Oct, 129(2):379-86 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/12403114
  4. Cercarial dermatitis. Its characteristics and prevention. Chin Med J (Engl) [online] 1977 Mar, 3(2):109-10 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/408107
  5. HARDING JR. Cardiff's tropical disease: cercarial dermatitis. Med Hist [online] 1978 Jan, 22(1):83-8 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/345025

Examination

Fact Explanation
Rash Tiny red spots at the sites of larvae penetration is an early sign. Monomorphic maculopapular eruptions in parts of the human skin that comes in contact with the infecting water can be inspected. Blister formation occurs a day after the exposure. Itching may results in secondary bacterial infections. [1,2,3,4]
References
  1. Cercarial dermatitis. Its characteristics and prevention. Chin Med J (Engl) [online] 1977 Mar, 3(2):109-10 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/408107
  2. FARAHNAK A, ESSALAT M. A study on cercarial dermatitis in Khuzestan province, south western Iran. BMC Public Health [online] 2003 Nov 7:35 [viewed 26 July 2014] Available from: doi:10.1186/1471-2458-3-35
  3. LéVESQUE B, GIOVENAZZO P, GUERRIER P, LAVERDIèRE D, PRUD'HOMME H. Investigation of an outbreak of cercarial dermatitis. Epidemiol Infect [online] 2002 Oct, 129(2):379-86 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/12403114
  4. BRANT SV, COHEN AN, JAMES D, HUI L, HOM A, LOKER ES. Cercarial dermatitis transmitted by exotic marine snail. Emerg Infect Dis [online] 2010 Sep, 16(9):1357-65 [viewed 26 July 2014] Available from: doi:10.3201/eid1609.091664

Differential Diagnoses

Fact Explanation
Insect bites Insect bites and stings can be simply divided into 2 groups: venomous and non-venomous. For most people, insect bites or stings cause a mild reaction. Venomous stings usually cause a stinging sensation or pain with redness and swelling of the area. Itch is usually not a concern. In some people who are sensitive to insect venom, a sting may cause a severe allergic reaction known as anaphylaxis. This results in facial swelling, difficultly breathing and an itchy rash (urticaria) over most of the body. This can be life-threatening so immediate medical attention and treatment needs to be sought.
Human schistosomiasis There are three species of schistosome which commonly cause disease in man: Schistosoma mansoni, S. haematobium and S. japonicum. Cercarial penetration of the skin may cause local dermatitis (‘swimmer’s itch’). After a symptom-free period of 3–4 weeks, systemic allergic features may develop, including fever, rash, myalgia and pneumonitis (Katayama fever). These allergic phenomena are common in non-immune travellers, but are rarely seen in local populations, who are usually exposed to infection from early childhood onwards. If infection is sufficiently heavy, symptoms from egg deposition may start to appear 2–3 months after infection.
Sea bather’s eruption Sea bather's eruption is a rash that affects areas of the skin covered by a bathing suit, rather than exposed areas, after swimming in the sea. It is caused by stings from the stinging cells (also called nematocysts) of the larval forms of certain sea anemones and thimble jellyfishes. A tingling sensation under the bathing suit (breasts, groin, cuffs of wetsuits) is often first noticed while still in the water. Over several hours it becomes an itch, which can last for several weeks.
Contact dermatitis Contact dermatitis is a common inflammatory skin condition characterized by erythematous and pruritic skin lesions that occur after contact with a foreign substance. There are two forms of contact dermatitis: irritant and allergic. Irritant contact dermatitis is caused by the non–immune-modulated irritation of the skin by a substance, leading to skin changes. Allergic contact dermatitis is a delayed hypersensitivity reaction in which a foreign substance comes into contact with the skin; skin changes occur after reexposure to the substance. The most common substances that cause contact dermatitis include poison ivy, nickel, and fragrances. Contact dermatitis usually manifests as erythema and scaling with relatively well-demarcated, visible borders. The hands, face, and neck are usually involved, although any area can be affected.
References

Management - General Measures

Fact Explanation
Protective ointments Mild itching will be resolved spontaneously. If the itching is spread in a wide area, when the reaction begins, the skin should be lightly rinsed with isopropyl alcohol and then coated with calamine lotion. [1,2,3]
Anti-inflammatory drugs Antihistamines and topical corticosteroids (1% hydrocortisone) may be beneficial to suppress the allergic reaction and thereby provides symptomatic relief for both itching and rash. If the reaction is severe, oral steroids (prednisone) may be appropriate. [1,2,3]
Antibiotics Abrasions caused by severe itching can predispose to secondary bacterial infections. Topical antibiotic skin creams such as fucidin, mupirocin or oral cloxacillin can be used. [4,5]
Epsom salts Bathing in epsom salt (Magnesium sulfate) added water provides symptomatic relief for itching. Bath sprinkled with oatmeal is an alternative. [1,2,3]
Sodium bicarbonate Sodium bicarbonate (baking soda) has found to be one of the most effective treatments. Topical application as a paste or bathing sprinkled with sodium bicarbonate provides instant relief from itching. [1,2,3]
Prevention Toweling immediately after leaving the water may be helpful as a primary preventive method before the larvae enter the exposed skin. Because the cercariae are present in greatest concentration in shallow, warmer water (where the snails are), swimmers should try to avoid these areas. Niclosamide is a antihelmintic drug. Water resistant sun cream with 0.1%-1% niclosamide has been shown to be highly effective. Treating waterfowl which includes ducks, geese and fowls (hosts for schistosma) in order to reduce transmission has been considered. [1.2,3,4,5]
References
  1. HARDING JR. Cardiff's tropical disease: cercarial dermatitis. Med Hist [online] 1978 Jan, 22(1):83-8 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/345025
  2. FARAHNAK A, ESSALAT M. A study on cercarial dermatitis in Khuzestan province, south western Iran. BMC Public Health [online] 2003 Nov 7:35 [viewed 26 July 2014] Available from: doi:10.1186/1471-2458-3-35
  3. LéVESQUE B, GIOVENAZZO P, GUERRIER P, LAVERDIèRE D, PRUD'HOMME H. Investigation of an outbreak of cercarial dermatitis. Epidemiol Infect [online] 2002 Oct, 129(2):379-86 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/12403114
  4. BRANT SV, COHEN AN, JAMES D, HUI L, HOM A, LOKER ES. Cercarial dermatitis transmitted by exotic marine snail. Emerg Infect Dis [online] 2010 Sep, 16(9):1357-65 [viewed 26 July 2014] Available from: doi:10.3201/eid1609.091664
  5. Cercarial dermatitis. Its characteristics and prevention. Chin Med J (Engl) [online] 1977 Mar, 3(2):109-10 [viewed 26 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/408107