SCHISTOSOMIASISFEBRUARY 24, 2015

Schistosomiasis, also called bilharzia or bilharziasis, snail fever, or Katayama fever.

Schistosomiasis  is a disease caused by parasitic worms of the Schistosoma type.

SPECIES OF SCHISTOSOMA S. japonicum- causes Asian

intestinal schistosomiasis. S. mansoni- causes intestinal

schistosomiasis that lodges in the blood vessels.

S. haematobium- causes urinary schistosomiasis.

S. intercalatum and S. mekongi

SNAIL HOSTSThe different species of Schistosoma have different types of snails serving as their intermediate hosts; these hosts are as follows : Biomphalaria for S. mansoni Oncomelania for S. japonicum Tricula (Neotricula aperta)

for S. mekongi Bulinus for S.

haematobium and S. intercalatum

S. japonicum

S. mansoni

S. haematobium

S. intercalatum S. mekongi

INCUBATION PERIOD 4-6 weeks usually pass before egg

production begins. Cercariae reach the portal venous

system several days post-infection . Toxemic schistosomiasis may develop

6-8 weeks post infection. Urinary schistosomiasis may develop

10-12 weeks post infection. Adult schistosomes may live 20 to 30

years.

MODE OF TRANSMISSION

Eggs hatch releasing miracidia (larvae/larval stage)

Miracidia penetrate snail tissues—Oncomelania hupensis (freshwater snails)

Cercariae released by snail into water ang free-swimming which penetrates the skin especially in cuts or wounds.

Cercariae lose tails during penetration and becomes schistosomulae

After circulation, the schistosomulae migrate to portal blood in liver and mature into adults.

Paired adult worms migrate to: Meseneteric venules of rectum (laying eggs that circulate in the liver and shed in stool) by S. japonicum and S. mansoni

Venous plexuses of bladder and shed in urine by S. haematobium

SIGNS AND SYMPTOMSSymptoms vary with the species of worm and the phase of infection. Heavy infestation (many parasites)

may cause fever, chills, lymph node enlargement, and liver and spleen enlargement.

Initial invasion of the skin may cause itching and a rash (swimmer's itch). In this condition, the schistosome is destroyed within the skin.

Intestinal symptoms include abdominal pain and diarrhea (which may be bloody).

Urinary symptoms may include frequent urination, painful urination (dysuria), and blood in the urine (hematuria).

COMPLICATIONS Gastrointestinal bleeding GI obstruction Malnutrition Schistosomal nephropathy Renal failure Pyelonephritis Hematuria

Hemospermia Squamous cell bladder cancer Sepsis (Salmonella) Pulmonary hypertension Cor pulmonale Neuroschistosomiasis - Transverse myelitis, paralysis, and cerebral microinfarcts

Infertility Severe anemia Low B birth-weight babies Spontaneous abortion Higher risk for ectopic pregnancies

End-organ disease

Portal hypertension Obstructive uropathy Pregnancy complications from vulvar or fallopian granuloma

Carcinoma of the liver, bladder, or gallbladder

SCREENING TESTS KATO-Katz-  is a laboratory

method for preparing human stool samples prior to searching for parasite eggs.

Urine filtration method- test for the presence of S. haematobium.

Blood tests- are occasionally useful in supporting the diagnosis or assessing the severity of schistosomal infection.

Rectal Mucosal Biopsy

TREATMENT AND CURE Praziquantel- used to treat all kinds of schistosoma species

Steroids (Corticosteroids) are used to relieve the symptoms of acute schistosomiasis.

Schistosoma species infection

Praziquantel dose and Duration

Schistosoma mansoni, S. haematobium, S. intercalatum

40 mg/kg per day orally in two divided doses for one day

S. japonicum, S. mekongi

60 mg/kg per day orally in three divided doses for one day

SIDE EFFECTS OF PRAZIQUANTELMore common Drowsiness Increased sweating General feeling of discomfort or

illness Nausea or vomitingLess common Hives or Urticaria

PREVENTION

Avoid swimming or wading in freshwater especially those with open wounds or cuts

Drink safe water Always boil or filter water even for used for bathing

CONTROL Mass treatment of entire communities and targeted treatment of school-age

Improved sanitation could reduce or eliminate transmission of this disease