THE VARIED ROLES OF SNAILS - National Universities Commission

The species of snails used depends on the geographical
region but generally S. haematobium and S. intercalatum
develop in snails of the genus Bulinus (Planorbidae). S.
mansoni develop in Biomphalaria where as develop in
Oucomelania.
Through a series of asexual multiplicative division in the
snail, a single miracidium will give rise to thousands of
cercariae all of the same sex.
When man enters the water the cercariae penetrate the skin,
often between the hair follicles and after between 4 – 12
weeks depending on the species, eggs start appearing in
either urine or faeces.
Persons with Schistosomiasis may be asymptomatic or may
manifest a spectrum of disease conditions. Acute
schistosomiasis or Katayama fever occurs after the initial
exposure and infection in S. mansoni or S. japonicum. This
febrile condition results as a result of hypersensitivity
reaction to schistosomal antigens. The patients complain of
flu like illness with fatigue, headache and might sweat
without the snail intermediate host the infection of man or
animals is impossible.
Schistosomiasis is endemic in Nigeria and studies show
that infection is focal and aggravated by developmental and
agricultural projects. Several studies in Nigeria show that
children within the age group 10 – 14 bear the most burden
of the disease which depends on the human water contact
patterns due to domestic, recreational and agricultural
imperatives, and also follows the socio economic status of
people in the endemic areas. Studies such as those of
Cowper (1973), Iheagwam and Okafor (1984), Adekolu-
John and Abolarin (1986), Anya and Okafor (1986),
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