PARASITOLOGY
age and medical history such as: schistosomiasis symptoms; abdominal pain; diarrhoea (more
than three bowel movements per day); bloody stools; weakness; absence from work due
to illness; history of treatment of schistosomiasis.
Each person in the sample was given a physical examination to determine liver and
spleen size. Faecal samples were collected and examined using the Kato–Katz tech-
nique. The parasite eggs per gram stool was calculated from three preparations. All
positive cases were treated with a drug (praziquantel). Egg-positive cases were divided
into three groups using a table of random numbers and adjusted for age and intensity of
infection. Groups A and B were given a single oral dose of 40 mg praziquantel/kg body
weight. Group C had no treatment at all. Group B was given further treatment after
6 months.
The data collected from this population showed that the overall infection was similar
on all five sites. Among those infected there was a significantly higher prevalence in the
males 49% (95/195) over females 28.9% (35/121), P<0.01. Two infected groups were
detected between the ages of 20–29 (54%) and 40–49 (50%). The mean number of eggs
per gram was 34.4 in the lower age group while in the higher group it was found to be
45.8 eggs per gram. Enlargement of the spleen (hepatomegaly) was diagnosed in 37.3%
(118 subjects) and seven were found to have a palpable spleen. However the examina-
tions indicated that enlargement of the liver and spleen was not significantly associated
with egg secretion.
The effect of drug treatment (chemotherapy) was that 12 months post-treatment
77.8% and 84.1% of individuals in groups A and B respectively (the treated groups) no
longer secreted eggs, whereas in the control group C only 14% were still not secreting
eggs.
The above observations must be considered in conjunction with the local topography
and climate. The lake levels rise up to 8 m in May to October. During this time faeces
pass into the lake untreated. Infected snails are found throughout the year but are more
numerous during the main fishing season; and during this period acute schistosomiasis is
more common.
The migrant fisherman themselves were thought to be the most important source
of the infection. However the possibility of a zoonosis, that is an animal reservoir host
existing in the area, was investigated. Ten to fifteen per cent of the local water buffalo
were found to be infected with S. japonicum. This is a much lower rate of infection than in
the human population, but the volume and quantity of excreta from individual animals is
so much larger than from humans that they may be an important source of contamination.n BOX 8.3
There are series of fresh water lakes in northern Huna province covering an area of
15,200 sq. km. A series of small lakes plus rivers drains the high ground and flood waters
rise up to 8 m before draining into the Yangtse river. One lake, the Dongting lake, has a
surface area of 2,691 sq. km. It is the second largest fresh water lake in China and is one
of the most endemic areas for S. japonicumin China. Malaria is not endemic in that region.
There are about 150,000 fisherman and families living in the area and most have extens-
ive contact with the water. In general there are no modern sanitary facilities; and all urine
and excreta enter the lake. The fisherman have no fixed homes and move around the lake
according to the season and water level.