Schistosomiasis

Schistosomiasis

also known as bilharzia (bill-HAR-zi-a) or Snail Fever is a disease caused by parasitic worms. Infection with Schistosoma mansoni, S. haematobium, and S. japonicum causes illness in humans.

Mature worms: Dioecious

Female :long and thin.

Male:short and thick

Eggs: miracidia in it

Schistosomiais is prevalent in tropical and sub-tropical areas, especially in poor communities without access to safe drinking water and adequate sanitation. Of the 207 million people with schistosomiasis, 85% live in Africa.

There are two major forms of schistosomiasis – intestinal and urogenital – caused by five main species of blood fluke

Epidemiology

Table: Parasite species and geographical distribution of schistosomiasis

Species Geographical distribution

Intestinal schistosomiasis

Schistosoma mansoniAfrica, the Middle East, the Caribbean, Brazil, Venezuela, Suriname

Schistosoma japonicum China, Indonesia, the Philippines

Schistosoma mekongiSeveral districts of Cambodia and the Lao People’s Democratic Republic

Schistosoma intercalatum and related S. guineansis

Rain forest areas of central Africa

Urogenital schistosomiasis

Schistosoma haematobium Africa, the Middle East

Sources/Causes

¨Source of infection: humans and mammals

(especially cattle) infected by schistosome

¨Route of transmission: three major

factors* are responsible for the occurrence

of schistosomiasis

¨Susceptibility : everyone is susceptive.

Especially peasant and fisherman

Women doing domestic chores in infested water, such as washing clothes, are also at risk.

Hygiene and play habits make children especially vulnerable to infection.

Three Major Factors

The method of disposal of human

Excreta

The presence of the snail

intermediate host

The contact with cercaria-infected

water

CausesA person infected with schistosomiasis expels eggs in their faeces or urine.

In villages or communities where there is no proper latrine system or sanitation, freshwater sources around the village or community can easily become contaminated with faeces or urine containing the eggs. On contact with water, the eggs hatch and release larvae called miracidia. In order to survive, these tiny larvae must find a specific freshwater snail to inhabit. If the miracidia find the right type of snail, they use it to multiply in several cycles, eventually producing thousands of new parasites, called cercariae, which the snail then releases into the surrounding water.

Humans become infected when they come into contact with contaminated water. In a few seconds the cercariae penetrate the skin and make their way into the person's bloodstream.

2-6 weeks after exposure

COMMUNICABILITY: Not directly transmitted

from person-to-person; infective person will release eggs in urine and feces; infective snails will release cercariae as long as they live (several weeks to 3 months)

INCUBATION PERIOD

•Incubation period is typically 14–84 days for acute schistosomiasis (Katayama syndrome), but chronic infection can remain asymptomatic for years.

•Penetration of cercariae can be associated with a rash that develops within hours or up to a week after contaminated water exposures.

•Acute schistosomiasis is characterized by fever, headache, myalgia, and respiratory symptoms. Eosinophilia is present, as well as often painful hepato- and/or spenomegaly.

•The clinical manifestations of chronic schistosomiasis are the result of host immune responses to schistosome eggs. Eggs secreted by adult worm pairs enter the circulation and lodge in organs and cause granulomatous reactions. Eosinophilia may be present.

Clinical Manifestation

•S. mansoni and S. japonicum eggs most commonly lodge in the blood vessels of the liver or intestine and can cause diarrhea, constipation, and blood in the stool. Chronic inflammation can lead to bowel wall ulceration, hyperplasia, and polyposis and, with heavy infections, to periportal liver fibrosis.

•S. haematobium eggs typically lodge in the urinary tract and can cause dysuria and hematuria. Calcifications in the bladder may appear late in the disease. S. haematobium infection has been associated with increased risk of bladder cancer.

•Rarely, central nervous system schistosomiasis may develop; this form is thought to result from aberrant migration of adult worms or eggs depositing in the spinal cord or brain. Signs and symptoms are related to the site of the granulomas in the central nervous system and can present as transverse myelitis.

Part Manifestation

Skin swimmer’s itch, jaundice

Abdomen Hepatomegaly, splenomegaly,

lymphadenopathy

Intestine Dysentry

Visceral Inflamed liver (Big belly)

Brain Headache, dizziness, convulsion

Cerebral Schistosomiasis

•Reaction to schistosoma egg

•Cross blood brain barrier

•Increases ICP w/ focal neurologic sign.

COMPLICATION

1. Medical Treatment- Praziquantel is the drug of choice. However, it will

only treat mature worms (they can take 40 days to reach maturity), so taking the drug immediately after swimming is unlikely to be effective. ¨

Dose:chronic schistosomiasis > 10mg/kg, tid. Po, for 2 days, total 60mg/kg

Acute schistosomiasis > 10mg/kg,tid. po,for 4 days, total 120mg/kg

Vice reaction: slight and short.

Heteropathy

¨Acute schistosomiasis: rest, nutrition, and supportive theraphy. Cortical hormone can be used in minidose for severe toxic

symptoms.

¨Terminal schistosomiasis: treated as liver cirrhosis, and treat for complications

M-onitor the patient closely for developing any complication

S-mall feeding should be done

C-orrect fluid and electrolyte balance

O-bserve for the presence of hematuria

P-rovide quiet, clean, comfortable environment

E-at nutritious food rich in fiber

Schistosomiasis is increasingly encountered among travelers returning from the tropics; signs and symptoms of travelers may differ from those of local populations. During 1993–2005, schistosomiasis was diagnosed in 137 Israeli travelers, most of whom were infected while in sub-Saharan Africa. Clinical findings compatible with acute schistosomiasis were recorded for 75 (66.4%) patients and included fever (71.3%), respiratory symptoms (42.9%), and cutaneous symptoms (45.2%). At time of physical examination, 42 patients (37.1%) still had symptoms of acute schistosomiasis, chronic schistosomiasis had developed in 23 (20.4%), and 48 (42.5%) were asymptomatic. Of patients who were initially asymptomatic, chronic schistosomiasis developed in 26%. Diagnosis was confirmed by serologic testing for 87.6% of patients, but schistosome ova were found in only 25.6%. We conclude that acute schistosomiasis is a major clinical problem among travelers, diagnostic and therapeutic options for acute schistosomiasis are limited, and asymptomatic travelers returning from schistosomiasis-endemic areas should be screened and treated.

Surveillance

PREVENTION AND CONTROL

S-creen carefully your drinking water. Boiling is assurance.

C-ommunity health taeching

H-eat bath water for 5 minutes at 150o F

I-mprove farming through proper irrigation and drainage to reduce snail density.

S-afe water

T-owel drying after an accident

O-mit swimming or wading in fresh water

Follow these precautions when in countries where schistosomiasis occurs: •Avoid swimming or wading in fresh water. Swimming in the ocean and in chlorinated swimming pools is generally thought to be safe.•Drink safe water. Because there is no way to make sure that water coming directly from canals, lakes, rivers, streams, or springs is safe, either boil water for 1 minute or filter water before drinking it. Boiling water for at least 1 minute will kill any parasites, bacteria, or viruses present. Iodine treatment alone will not guarantee that water is safe and free of all parasites.

•Heat bath water for 5 minutes at 150o F. Water held in a storage tank for at least 48 hours should be safe for showering.

•Vigorous towel drying after an accidental, very brief water exposure might help to prevent the Schistosoma parasite from penetrating the skin. However, do not rely on vigorous towel drying to prevent schistosomiasis.

Prevention and Control

Quiz1. What are the 3 major species of schistosome which cause the disease?

S. haematobium, S. japonicum, and S. mansoniS. haematobium, S. nyctea, and S. alulaS. mekongi, S. pithecophaga, and S. echnodermaS. japonicum, S. annelida, and S. mansoni

2. Why is a common name for schistosomiasis "snail fever"?

A schistosome's first host in life is a tiny snailA schistosome is symbiotic with a tiny snailA schistosome is a type of venomous snail"Snail Fever" is not a name for schistosomiasis.

3. How does a schistosome normally enter the body?

Through the noseThrough the urethraThrough the skinThrough drinking water

4. How many eggs does an adult female schistosome pass daily?

3000 to 10000, depending on species500 to 1000, depending on species200 to 2000, depending on species300 to 5000, depending on species

5. True or false: The eggs of the schistosome are what do the damage to your system.

6. What are the 2 major forms of schistosomiasis?

7. Spell CORRECTLY the first stage of a schistosome's life after the egg. Answer: (1 word, begins with an "M", 10 letters)

Urinary and RectalKidneys and IntestinalIntestinal and LiverIntestinal and Urinary

8. Around Lake Volta in Ghana, approximately what percent of children have a certain form of schistosomiasis?

70%20%50%90%

9. Over time, what hazard can a certain form of schistosomiasis cause?

Liver cancerPoliomylitisTrypanosomiasisBladder cancer

10. How long does it take for the schistosome to enter the body?

10 to 30 min.30 to 60 seconds3 to 6 days5 to 10 min

11. Which of these drugs can be used for treating ALL forms of schistosomiasis?oxamniquinepraziquantelmetrifonatecinchona

12. Schistosomiasis affects the digestive organs. Which of these organs will schistosomiasis NOT affect? (freebee question)

Gall bladderHeartSmall intestineLiver

13. True or false: Schistosomiasis hinders children's academic performance?

14. Which of these is NOT a symptom of schistosomiasis?

hemorrhaging of the liver

sneezing

itchy rashcoughing

15. Is Schistosomiasis fatal to its human victims?

Yes

Absolutely NeverRarelySometimes

 What are the 3 major species of schistosome which cause the disease?

S. haematobium, S. japonicum, and S. mansoni. S. mekongi IS a schistosome species, believed to be very closely related to S. japonicum

 Why is a common name for schistosomiasis "snail fever"?

A schistosome's first host in life is a tiny snail. Other common names include bilharzia and bilharziasis after the scientist who discovered it, Theodor H. Bilharz.

 How does a schistosome normally enter the body?

Through the skin. It is possible for it to enter through the urethra or drinking water, but it wouldn't survive for very long if it did.  How many eggs does an adult female schistosome pass daily?

200 to 2000, depending on species. It will pass these eggs for up to 5 years.

 True or false: The eggs of the schistosome are what do the damage to your system.

T. What the schistosomes do is just suck blood and lay eggs. The eggs lodge into your organs.

 What are the 2 major forms of schistosomiasis?

Intestinal and Urinary. They live in these areas and feed on blood.

Spell CORRECTLY the first stage of a schistosome's life after the egg.

Miracidium. The second stage is circaria, then schistosomulum, and then schistosome.

   Around Lake Volta in Ghana, approximately what percent of children have a

certain form of schistosomiasis? 90%. Urinary schistosomiasis is what they have.

 Over time, what hazard can a certain form of schistosomiasis cause? Bladder cancer. The risk of bladder cancer w/ urinary schistosomiasis is 32 times the normal US rate.

 How long does it take for the schistosome to enter the body?

30 to 60 seconds. They enter painlessly through the skin.

 Which of these drugs can be used for treating ALL forms of schistosomiasis?

praziquantel. Praziquantel is for all forms, metrifonate treats urinary, and oxamniquine treats intestinal. Cinchona treats malaria.

 Schistosomiasis affects the digestive organs. Which of these organs will schistosomiasis NOT affect? (freebee question)

Heart.

 True or false: Schistosomiasis hinders children's academic performance?

T. Surprising, isn't it!

 Which of these is NOT a symptom of schistosomiasis?sneezing. The rash is caused when the schistosomes enter the skin.

 Is Schistosomiasis fatal to its human victims?

Sometimes. Only if linked with cancer in Egypt, otherwise it's treated quite easily!