morphology and geographical distribution of the worm as well as epidemology, its lifecycle , its definitive and intermediate host,various life stages egg, cercarie ,adult worm, the disease schistosomiasis, its symptoms and control medication,diagnostic stages,management, bilharziasis
2. INTRODUCTION
Schistosoma is the only trematode that invades through the skin.
Five species of schistomes infect humans
Schistosome haematobium causes urinary tract disease the other species
causes intestinal disease
GEOGRAPHIC DISTRIBUTION
Schistosoma haematobium-Africa, some in Middle East, Turkey, and India
Schistosoma mansoni-Africa and America
Schistosoma japonicum-Far east Asia, Some parts of Africa
Schistosoma mekongi- Southeast Asia
Schistosoma intercalatum- central and west Africa
3. EPIDEMIOLOGY AND MORPHOLOGY
Approximately 250 million people are infected with schistosomes and
600 million people are at risk
Adult worms are 10 to 20mm long
Schistosomes have separate sexes
The male has a canal in which the slender female worm resides
4. THE EGG
Eggs penetrate the intestinal or bladder mucosa and are passed in
stool or urine
Other eggs remain within the host organ or are transported through the
portal system to the liver
Excreted eggs hatch in freshwater, releasing miracidia, the first larval
stage
Miracidia enters snails
5. THE CERCARIE
Infective stage
Cercarie penetrate human skin within a few minutes after exposure
When they penetrate they lose their forked tail and transform into schistosomula
Schistosomula mature and reach mesentric veins(S.mansonii, S.japonicum. )
,bladder vessels (S.haematobium)where they live and ovulate for duration of
hosts life
10. PERIOD OF COMMUNICABILITY
Life span-5to 10 years, so infected human can excrete eggs up to 10 years
An infected snail can release cercarie from several weeks to 3 months of its life
An infected snail can lay eggs 300-3000/day
11. SCHISTOSOMIASIS
SCHISTOSOMIASIS OR BILHARZIA
Disease affecting many people in developing countries.
‘Acute schistosomiasis'- snail fever and cutaneous schistosomiasis
Low mortality rate, schistosomiasis can also be very debilitating
Bilharzia or bilharziosis, named after Theodor Bilharz, who first described the
cause of urinary schistosomiasis in 1851.
13. DIAGNOSTIC STAGE
Schistosoma haematobolium
Eggs found in urine of urinary Schistosomiasis patients
Oval egg with terminal spine
Schistosoma mansoni
Eggs found in stool of intestinal Schistosomiasis patients
Oval egg with lateral spine
14. MANAGEMENT
Contaminated water should be avoided
Sanitary disposal of sewage
Prevent contamination of water by feces and urine
Destruction of snails
Treat the patients
No vaccine is available
Praziquantel is effective against all species
