Schistosomiasis

Question 1

Geographical distribution

Answer 1

S Haematobium: Nile Valley in Egypt, Saudi Arabia, Yemen, Syria, Iran, • giving rise to urinary manifestation
2. S. Mansoni: Hyperendemic in Nile valley, S. arabia, Yemen, Sudan, Sporadically on Mediteranean coast viz Libya and S. America.
3. S. Japonicum: Common in China, Japan and far east. S. Mansoni, S. Japonicum affect intestinal tract

Question 2

Problem in Libya

Answer 2

There are three endemic foci in Libya
• Sebha and Derna: S. Haematobium
• Taourga: S. Mansoni was imported into Libya from Egypt (Nile valley is endemic)
Similarly movement of people from Fezzan to the coastal belt of Libya

Question 3

Agent Factor:

Answer 3

Blood flukes of the genus Schistosoma

Question 4

Vector (Intermediate hosts):

Answer 4

Fresh water snails (cannot survive in saline waters). • These snails breed in lakes, ponds, streams, dams, drains, irrigation channels.

Question 5

Host Factors

Answer 5

Age: 10-15 years
• Sex: Males > females
• Low socio-economic status
• Movement of people
• Occupation: Fishermen, Farmers & Agriculturist. Human habit of polluting : water supplies by- bathing, swimming, wading or washing clothes & utensils in polluted stream.
• Immunity: some degree of immunity to all Schistosomal infections occur in humans.

Question 6

Aims of Control programs :

Answer 6

1. To limit the spread of infection
2. To reduce the morbidity.
3. To eradicate the disease

Question 7

Incubation period & Mode of Transmission

Answer 7

Incubation period: long weeks to few years.
Mode of Transmission:
Man gets the infection by coming in contact with infected water containing Cercariae (infective stage).
They are attracted to the body & penetrate the skin of the human.

Question 8

The control measures

Answer 8

1. Prevention of human contact with infected water
2. Snail Control
3. Chemotherapy

Question 9

Chemotherapy that is the most effective & widely used drug for control of Schistosomiasis.

Answer 9

Praziquantel

Question 10

How to control snails:

Answer 10

• Physical method: sound water management (Drainage of swamps)
• Chemical method: use molluscicides.
• Biological method: use of competitors e.g. S .American snail will feed on eggs & young snails (in Egypt).
• Use of predators: certain species of fish

Question 11

How Prevent of Human Contact with infected Water :

Answer 11

• Provision of safe water supply for bathing, swimming, washing, drinking etc.
• Safe & hygienic disposal of animal & human excreta.
• Health Education