Schistosomiasis

Schistosomiasis

1. Schistosomiasis Dr. Sachin Adukia Dept. of Internal Medicine

2. Nomenclature and Classification The causative pathogen belong to Genus Schistosoma , live in blood vessel and cause schistosomiasis . People call them blood flukes. There are five species infecting human body. They are: 1. Schistosoma japonicum 2. Schistosoma mekongi 3. Schistosoma haematobium 4. Schistosoma mansoni 5. S. intercalatum

3. Schistosoma japonicum I.   Morphology 1. Adult worms are elongated cylindrical in shape, unlike other flukes. Two sexes are separate, gray white in color, but the female is much dark and slender, the male is shorter and thicker, sickle-like. In human body the male usually embraces the female into its gynecophoral canal appears “ K ”like (or the female usually resides in male’s gynecophoral canal).

4. Male: 10-20 x 0.5-0.55mm in size, oral sucker at top near by ventral sucker. Just behind the ventral sucker there is a longitudinal groove- gyncophoral canal in which the female normally resides. The esophagus is divided into two branches in front of the ventral sucker, and then unite to form a cecum at the posterior third part of the body. Seven testes are situated one by one, each has a delicate efferens which combine to form the vas deferens and dilate to become a seminal vesical opening in the genital pore just behind ventral sucker.

5. Female: Longer and slender than the male, much dark colored thread-like, 12-26x 0.1-0.3mm in size. The digestive system is similar to that of male. The vitellaria are located in the posterior part of the body surrounding the cecum . The unbranched , oval ovary lies in the mid-portion of the body. The uterus lies in the anterior portion of the body filled with 50-300 eggs arranged in a single row, arising from ootype to genital pore behind the ventral sucker.

6. Paired male and female adult worms. The female schistosomulum is the darker, curled worm within the male's gynacophoric canal

7. 2.  Mature egg is oval in shape, slight yellow in color, 89 x 67 µ , shell is thin without an operculum but with a lateral spine

8. 3.  Cercaria is infective stage. It is composed of the body and forked tail (including tail stem and fork) and has 5 pairs of penetrating glands in the body.

9. Life cycle 1. Site of inhabitation : the portal vein system, mainly in the inferior mesenteric vein. 2.   Infective stage : cercaria 3.   Infective route : by skin 4.   Intermediate hosts : Oncomelania snail 5. Reservoir hosts : mammals such as buffalo, cattle, wild rodents, goat, monkey, pig, fox. 6.  Eggs are main pathogenic factor: (They are inlaid in the liver and intestinal wall. Some of them are discharged in feces to complete its life cycle). 7. The development in human body requires 25-30 days. Cercaria can live 1-3 days. Life span of the adults is about 20-30 years.

10. Eggs inlaid in the portal areas and intestinal wall (SEA type IV allergy) Local tissues necrosis, proliferation and fibrosis intestinal ulcers, Liver cirrhosis stool with blood, Pus and eggs Spleen Portal vein hypertension syndrome Enlargement Function failure Immunity Anemia Collateral circulation between portal vein and ascites , albumin reduced, secondary infection vena cava are established emaciation Esophageal Umbilical Hemorrhoids varicosity ulceration Hemorrhage of superior digestive tract Die of hepatic coma, superior digestive tract bleeding and infective complication

11. Symptoms and Signs (1) Initial phase : It is characterized by fever, dry cough ( pneumonitis ), urticaria due to adolescents migration. (2) Acute stage: The characteristics symptoms is dysentery. The patient may pass stool with blood, pus and mucus 5-10 times per day with a large number of eggs. Chill, fever, and malaise occur. (3) Chronic stage: Chief manifestation of the patients are interval diarrhea or dysentery. The patients experience fatigue, general condition and strength deteriorate, loss of weight and interest, retardation of both physical and mental growth in children. Spleen and liver enlargement, anemia, in women menopause, sterility and abortion may occur. This stage may last from several years to 20 years.

12. (4) Terminal stage : is characterized by portal vein hypertension syndrome, common saying, abdomen distention looks like a big drum, emaciation looks like a fire wood. Ascites , emaciation, varicosity, splenomegaly and anemia are commonly found. The patients die of secondary infection, upper digestive tract bleeding, hepatic coma. ** Ectopic lesion: The damage to the central nervous system ( brain,spinal ) may cause paralysis ( monoplegia , hemiplegia ).

13. Ascites , emaciation, varicosity, and splenomegaly

14. Diagnosis The symptoms, signs and history of living in endemic areas only give a presumptive diagnosis. The definitive diagnosis depends on the pathogen examination. 1. Stool examination: ( i ) Direct fecal smear for acute stage (ii) Concentration method: Water sedimentation method and miracidia hatching test can be done at same time; nylon net method may be used 2. Biopsy can be done by proctoscope for terminal stage. 3. Immunological tests are subsidiary for reference only.

15. Treatment In severe acute schistosomiasis , management in an acute-care setting is necessary, with supportive measures and consideration of glucocorticoid treatment. Once the acute critical phase is over, specific chemotherapy is indicated for parasite elimination. For all individuals with established infection, treatment to eradicate the parasite should be administered. The drug of choice is praziquantel administered PO as a total of 40 or 60 mg/kg in two or three doses over a single day. Praziquantel treatment results in parasitologic cure in 85% of cases and reduces egg counts by >90%.

16. Specific Treatment Infection Drug of Choice Adult Dose and Duration Blood Flukes   S. mansoni , S. intercalatum , Praziquantel S.haematobium   20 mg/kg, 2 doses in 1 day S. S. japonicum , S. mekongi   Praziquantel 20 mg/kg, 3 doses in 1 day

17. Prevention and Control Transmission of schistosomiasis is dependent on human behavior. It is prudent for travelers to endemic areas to avoid contact with all freshwater bodies, irrespective of the speed of water flow or unsubstantiated claims of safety Control measures have been used, including application of molluscicides , provision of sanitary water and sewage disposal, chemotherapy, and health education The ultimate goal of research on prevention and control is the development of a vaccine.

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