Comments
INITIAL SYMPTOMS:
Dysuria, urinary frequency, and hematuria for S. haematobium; The hematuria occurs typically at the end of urination. [CCDM] "Swimmer's itch" is a pruritic papular rash that develops within 24 hours at the site of penetration. [PPID, p. 3219]
FINDINGS:
Cercarial dermatitis occurs within 24 hours of skin penetration and usually consists of papules at sites of entry on the lower legs. Acute schistosomiasis (Katayama fever) is rare in S. haematobium infections. Egg deposition in the lungs may cause pulmonary nodules and cor pulmonale. Other complications of chronic S. haematobium infection are chronic renal failure and transverse myelitis. [Guerrant, p. 851-2] Diseases related to chronic infection include obstructive uropathy, hydronephrosis, pyelonephritis, and bladder cancer. [ID, p. 2378] Repeated pyelonephritis may lead to renal failure. Marked eosinophilia is present early. Eosinophilia may be present or absent in chronic infections. [Guerrant, p. 851, 943] Katayama's fever (fever, lymphadenopathy, urticaria, and eosinophilia) is rare in urinary schistosomiasis. [PPID, p. 3219] Symptoms of pulmonary involvement are cough, dyspnea, and hemoptysis. [Cohen, p. 1918] Eggs can lodge in the spinal cord (transverse myelitis) and CNS (seizures). [Merck Manual, p. 1359]
EPIDEMIOLOGY:
Humans are the main reservoirs, and snails are intermediate hosts for these trematode infections. Human infections commonly last more than 10 years. [CCDM, p. 554-5] Most cases in travelers are acquired in sub-Saharan Africa. People are infected while swimming, bathing, or wading in freshwater in endemic areas. Prevalence rates can exceed 50% in some areas, e.g., Burkina Faso, Mali, Lake Malawi, Lake Tanganyika, Lake Victoria, Omo River, Zambezi River, and the Nile River. "The distribution of schistosomiasis is very focal and determined by the presence of competent snail vectors, inadequate sanitation, and infected humans." Control programs are effective, but there are no international guidelines for certification of elimination. [CDC Travel, p. 309]
For updated text and symptoms of infectious diseases, see iddx.com.
Latency/Incubation
2-6 weeks for Katayama fever; [CCDM, p. 554] First eggs in stool 1-3 months after exposure; [Merck Manual, p. 1358]