Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes (Trematode worms) of the genus schistosoma. (According to WHO )
It is also called bilharzia named after a Germany Theodore Bilharz who discovered it in Cairo during 1851.
EPIDEMIOLOGY:
The disease is very common in poor rural people living or doing their activities in stagnant or slowly moving fresh water like in the Nile valley dwellers in tropical and subtropical areas.
78 countries have reported this disease including Tanzania but the disease is mostly found in Egypt in which it has been there for many centuries and estimates show that atleast 258 million people need preventive chemotherapy each year by 2014 and atleast 90% of patients live in Africa.
In Tanzania the disease affect school aged kids, fishermen and farmers mostly poor and people living in lake shores of Victoria, Tanganyika, Nyasa and near river banks.
The prevalence is higher in men than in women because most of men jobs like fishing and farming predispose them more to these worms as compared to women.
Transmission occurs when people with the disease contaminate fresh water with excreta containing parasite eggs which hatch in water follows the cycle through intermediate hosts (snails) in particular and then a larval form of the parasite from the snail penetrate the skin of a person in contact to cause the disease.
Most infections are intestinal and urogenital but pulmonary cases has been occuring even though rarely. Also eggs in skin, adrenal glands, genitalia, eyes and the brain has been found together with their symptoms.
There are five species of schistosoma worms:
Schistosoma mansoni is a specie which cause intestinal schistosomiasis mostly. it lays eggs which have lateral spines and its intermediate host specie is called Biomphalaria. Common in Africa, middle east and South America.
Shistosoma japonicum is a specie which cause intestinal schistosomiasis too, lay eggs which have lateral knobs and its intermediate host is called Oncomelania. It is common in China, Indonesia and Philipines (Asia)
Schistosoma mekongi is a specie that cause intestinal schistosomiasis. its intermediate host is Tricula (Neotricula aperta). Common in Cambodia and people's democratic republic of Lao.
Schistosoma guineensis/intercalatum Also causes intestinal schistosomiasis, its intermediate host is Bulinus for intercalatum and Bulinus forskalii for guineensis to be more specific.Bulinus forskalii is more common in West Africa. the specie is also found in central Africa.
Schistosoma hematobium is a specie that causes urogenital schistosomiasis and it lays eggs which has terminal spines. its intermediate host is Bulinus species and very common in Africa, Middle east and France.
SYMPTOMS OF SCHISTOSOMIASIS:
In some books are categorized into three stages which are:
a) itching
b) fever, urticara, eosinophilia symptoms
c) presinusidal portal hypertension symptoms
But the following are general symptoms of schistosomiasis:
a) Abdominal pain, diarrhoea, blood in stool
b) Abdominal distension
c) Engorged abdominal vessels
d) Hematuria
e) Vaginal bleeding
f) Pain during sexual intercourse
g) Infertility
h) Hematemesis
Symptoms depend with the type of schistosomiasis the patient has, neurological symptoms will be present if the patient has cerebral schistosomiasis and the same goes to pulmonary schistosomiasis.
PREVENTION AND CONTROL:
Large scale treatment of at risk population groups (preventive chemotherapy), access to safe and clean water, improved sanitation, hygiene education and snail control are some of the ways to prevent and control schistosomiasis.
Treatment of the disease is by the use of PRAZIQUANTEL mostly. Dosage is 20mg/kg body weight 3 doses 4 hours apart OR 40mg/kg to 75mg/kg body weight as a single dose which is the treatment of choice in most health facilities.
THE LIFE CYCLE OF SCHISTOSOMA SPECIES:
-Eggs in faeces or urine goes into stagnant water
-After 16 hours they hatch in fresh water releasing Miracidia
-Miracidia penetrates snail tissue
-Sporocyst in snail's liver is formed as the result of miracidia growth. this takes 4 to 8 weeks
-Primary sporocyst develop into secondary and finaly into cercaria
-A bifid tail cercaria is released by the snail into fresh water, in most cases leaving the snail dead. cercaria can stay alive in water for up to 3 days.
-The cercaria will penetrate the skin of a person in contact, goes through lymphatic system and loses its tail to become Schistosomula as it enters circulatory system.
-Schistosomula can circulate through the body but it will mature only in portal veins and portal blood in liver.
-Paired adults migrate to mesenteric venules of rectum, bowel or venous plexus of bladder and lay eggs.
-Hundreds of ova can be produced a day. S. hematobium has high affinity to vesical venous plexus. in the bladder; damage is caused by the blockage of venules by the eggs and worms and egg spike at the terminal of the egg.
-These eggs will pass in stool or urine into stagnant fresh water to start the cycle all again.
SURGICAL COMPLICATIONS:
1) SCHISTOSOMIASIS OF BLADDER AND BLADDER CANCER
Bladder cancer is 3 more common in male than in females. There is a strong relationship between bladder schistosomiasis and cancer as how it is explained later.
Pathophysiology:
This was covered in the part of schistosoma life cycle to some extent.
Clinical features:
-Urticaria lasting about 5 days (swimmer's itch)
-Following incubation period of 4 to 12 weeks; intermittent fever, sweating, sometimes asthma, marked esinophilia with leukocytosis.
-Intermitent painless terminal hematuria.
How does bladder cancer occur?
Mostly are pure squamous cell carcinoma, associated with chronic irritation caused by stone disease in bladder as the result of metaplasia. They tend to be solid and involves muscles (Detrusor muscles).
Causative agents are schistosome associated bladder carcinogenesis which are:
-N-nitroso compounds which damage cells and were found to be elevated in the urine of patients with bladder schistosomiasis.
-Reduced ability of carcinogen metabolizing agents in late stages of the disease causing prolonged action of N-nitrosamines and inflammatory cell actions which further induce endogenous production of N-nitrosamines and produce Oxygen radicals.
All these may damage host cells DNA causing cancer of the bladder.
This is supported by experiments in animals done by American society for microbiology and also epidemiological and geographical relationship of bladder schistosomiasis and bladder cancer.
Investigations:
Before investigations, bimanual examination of the bladder under general anaesthesia and empty bladder is very important as it can contribute to staging the bladder cancer.
Investigations which can be done are:
a) Urine and stool examination by Kato Katz technique
b) Antibody detection by ELISA using S. mansoni/hematobium adult microsomal antigen (MAMA), this is positive after 1 month of infection and specific to hematobium and mansoni species only.
c) Cystoscopy in which depending on the chronicity of the disease the following may be seen:
-Bilharzial pseudotubercles which are earliest specific appearance of the disease.
-Bilharzial nodules which are caused by fusion of tubercles
-Sandy patches which are result of calcified dead ova with degeneration of the overlying tubercles
-Ulceration as the result of sloughing off of the mucus membrane containing ova
-Fibrosis as the result of secondary infection.
-Granulomas which are caused by agregation of nodules
-Papiloma which are pedinculated parts of the mucosa
-Carcinoma which is the solid mass or tumor with irregular shape and other malignancy features
Treatment:
As explained before; Praziquantel is the treatment of choice for schistosomiasis. The following is a summary on treatment of Bladder cancer:
For non invasive tumors:
-Endoscopic surgery by resectoscope
-Open surgical excision
-Tumor removed by diathermy needke base coagulator
For invasive tumors:
-Open beam radiotherapy (mainly)
-Partial cystectomy
-Radical cystectomy and pelvic lymphadenectomy.
2) PORTAL HYPERTENSION AND ITS SEQUELA
Tropical splenomegaly together with eosophageal varices are two main sequela of Portal hypertension. Tropical splenomegaly is splenic enlargement caused by schistosomiasis, can also be caused by frequent Malaria attacks and can occur at any age. Esophageal varices are congested esophageal veins as the result of inreased resistance in venous blood return to the portal venous system into inferior vena cava through the liver due to portal hypertension. due to their congestion, these veins can easily bleed causing upper GI bleeding.
Pathophysiology:
Splenic enlargement is caused by portal hypertension associated with hepatic fibrosis. Another way in which splenomegaly can occur is through hyperplasia induced by the phagocytosis of disintegrated worms, ova and toxins.
Egg retention and granuloma formation causes periportal fibrosis in a characteristic pipe stem pattern (symmer's pipestem fibrosis) with sparing of hepatocellular function. Thats how portal hypertension occurs and its sequela too like ascites, esophageal varices and splenomegaly.
Note:
Portal hypertension causes porto-systemic collaterals Eg. Venous blood can be pushed more to inferior vena cava causing eggs to reach pulmonary circulation causing pulmonary schistosomiasis hence pulmonary hypertension to corpulmonale.
According to studies, about 18.5% of patients with hepatosplenic schistosomiasis develop portal hypertension.
Investigations:
-Examination of urine and faeces for ova (kato katz technique)
-Liver function test (LFT)
-Enzyme linked immunosorbent assay (ELISA) using MAMA
-Ultrasoun
-Full blood picture (FBP)
Treatments:
-Praziquantel will not significantly reverse most of the complications already caused by schistosomiasis, like reducing the enlarged spleen or returning the portal hypertension to normal so tratment should be targeted on destroying the schistosomes if are still there and also treat the complications of portal hypertension.
In splenomegaly:
-Splenectomy can be done depending in the severity of the condition.
In esophageal Varices:
a) If acute:
-Blood transfusion (BT)
-Fresh frozen plasma and platelets
-Recombinant factor VIIa
-Prophylactic antibiotics
-Vasopressin (0.2-0.8 units/min), it is a potent vasoconstrictor
-Somatostatin (octreotide), a vasoconstrictor through splanchnic nerves
-Balloon tamponade using Sengstaken Blakemore tube
-Endoscopic vein ligation as soon as possible to prevent further bleeding.
b) If not acute:
-Improve life function
-Avoid NSAIDs and Aspirins
-Administer beta blockers
-Prophylactic endoscopic varices ligation
-Surgical shunts which can be:
-Portal caval shunt (Eck fistula)
-Mesocaval hunt (Dacron shunt)
-Distal splenorenal (Warren shunt), this is mostly used
-Transjugular intrahepatic porto systemic shunt
Other complications of schistosomiasis of surgical importance are:
-Ureteral stricture
-Bilharzial urethral stricture
-Prostatoseminal vesiculitis
-Bladder and bladder neck fibrosis
-Recurrent cystitis
-Fistula and sinus can develop in the bladder secondary to schistosomiasis
