Journal of Applied Sciences & Environmental Management, Vol. 9, No. 3, 2005, pp. 37-43

The Epidemiology of Schistosoma haematobium in Odau Community in  the  Niger  Delta  Area of  Nigeria

*AGI, P I; OKAFOR, E J

Department of Animal and Environmental Biology, Faculty of Science, University of Port Harcourt, Nigeria

Code Number: ja05056

ABSTRACT:

A study was conducted between August 2001 and July 2002 to investigate  the current pattern of prevalence and intensity of Schistosoma   haematobium infection at  Odau Community in the Niger Delta Area  of  Nigeria.. Three hundred urine specimens  were examined from randomly sampled individuals aged between 0 years and 73 years. More than 50%  of the participants were under the age of 20 years, and the population sampled had a male to female ratio of 37:23. Quantitative microscopic counting of Schistosoma haematobium eggs was carried out. Two hundred  and fifty  participants  out of  the three  hundred examined  were positive  for  the infection, representing  an overall estimated prevalence of  83.3%.  The   infection rate  peaked  (93.0%) in the  10-14 years  age  category.  A significant negative  correlation (r =0.306,  P < 0.1) was  found  between age  and  intensity  of infection. The age and sex  pattern of Schistosoma haematobium infection as  obtained  from the  study area  showed  a typical  peak  prevalence  in  early  adolescence with  males  having a higher  prevalence  rate  (84.9%) than females’  (80.9%) (χ² = P > 0.01). The  high rates  of  prevalence  and   intensity of  Schistosoma haematobium  observed  in the  present  study clearly  indicated  that  Odau  Community  is  facing  a great  health burden especially the children  and  women who had severe  infections. @JASEM

Schistosomiasis is a wide spread parasitic infection caused by blood flukes of the genus Schistosoma and transmitted by specific fresh water snails. The infection is reported to have plagued the humans since the ancient times (El-Harvey et al; 2000). Some of the factors which influence the transmission of schistosomiasis in an endemic area include the presence of snail intermediate hosts of the parasites and human contact with the infected waters.  Out of the three main human infecting species of Schistosoma (S. haematobium, S. mansoni  and S. japonicum), S. haematobium is the predominant species in Africa being endemic in about 53 countries in Africa and the Middle East (Ejezie, 1991; Ogbe, 1995). Urinary schistosomiasis, caused by S. haematobium is noted to be more prevalent in Nigeria than intestinal schistosomiasis due to the wider distribution of its snail host Bulinus species (Ejeizie, 1991; Ugbomoiko, 2000) This is in addition to indiscriminate passing of urine containing S. haematobium eggs into water supplies containing the snail host (Southgate and Rollinson, 1987).

Records of prevalence and intensity of urinary schistosomiasis in areas of endemicity show an infection  pattern which seems to peak in individuals in their first two decades of life, and with varing rates (Ogbe, 1995, El-Harvey et al; 2000). When compared with their adult counterpart, children with schistosomiasis notedly harbour greater worm burden and are more intensely infected due to the high transmission rates of the parasite and the frequency of exposure to infection sites (Ogbe, 1995). Individuals who are encountering the infection for the first time may exhibit severe infections irrespective of their age and sex. In countries  with  a long  history of  schistosomiasis research studies   have identified  the risk factors for infection  with S. haematobium  as  male gender, an age  < 20 years,  living in smaller  rural communities, exposure  to canal  waters,  reagent  strip  detected  haematuria and proteinuria, and  a history  of  burning  micturition (El-Harvey et al;  2000;  Abdel-Wahab et al; 2000; Gabr et al;  2000). 

The amount of eggs excreted and quantified in 10ml of urine specimen expresses the intensity which may be associated with the severity of the internal damage (Loverde and Chen, 1991). In S. haematobium endemic area evidence has shown that long term infections are associated with certain risks of urinary involvement  which manifest as haematuria, proteinuria, pathology of the urinary tract, iron deficiency  anemia and impaired growth (Warren et al;  1979; Stephenson et al; 1985; Belidi-Mengue et al;  1992;  Abdel-Wahab et al; 2000). Severity of the disease may result to bladder cancer later in adulthood (Mustafa et al;  1995) There are continuous increase in the prevalence and intensity of urinary schistosomiasis in many endemic communities in Nigeria (Anosike et al;  1999). S. haematobium infection has been found endemic in Rivers State (Agi, 1995). Few foci of S. mattheei and S. intercalatum have been noted by Arene et al; 1989). The world Health Organization (1985) has recommended that the combined use of antischistosomal drugs with environmental sanitation and health education could drastically reduce the prevalence and intensity of S. haematobium. This method of control has been used for schistosomiasis in some endemic areas with desirable results (Doenhoff et al;  2000; Habib  et al;2000). The present study examines the current  pattern of  prevalence  and  intensity of S. haematobium  infection at  Odau community in the Niger  Delta Area  of  Nigeria.

MATERIALS AND METHODS

Study Area: The study was conducted in Odau, a rural community in Niger Delta Area of  Nigeria made up of mainly peasant farmers. The community is located on latitude 40° 56'N and longitude 60° 27' E, and surrounded by fresh water swamps. Most families are subsistent farmers and fresh water fisher folks. They mainly depend on various ponds and streams for their water related activities. The inhabitants of the community had neither a good road nor hospital facilities and there are no latrines, so urination and defecation are done in the bushes surrounding the village.

Sample Collection: Three hundred individuals were randomly selected for the study. Participation was entirely voluntary and the people were made aware of the study and its benefits by exposing them to health education. Each participant was given a clean 40 ml universal bottle to provide terminal urine between 10.00 am and 2.00 pm. Each bottle was labelled to correspond to the number of the person’s card. Each person was sampled for two consecutive days and a duplicate 10ml urine specimen was filtered from each sample using the Nitrel filtration technique described by Mott et al (1982).

Nitrel filtration equipment  consists  of a 10ml  plastic  syring, a plastic  extension  tube,  a nilon mesh filter and filter supports. The extension  tube was  fitted unto the end of the syringe. The top part of the filter  support  was connected to the adaptor of the syringe while  the bottom held the filter inside and both were tightly  held together by a silicon  gasket. Each urine  specimen  was  thoroughly  mixed and 10ml  drawn into the  syringe. The  urine  was  forced  through the  filter  into the filter  support  and  the residues including  schistosome   eggs  collected  on the  filter.  The filter  was removed  from the  support  with a pair  of forceps,  placed on a clean  glass  microscope  slide  and  stained  with drops  of  Lugol’s   iodine  solution prior  to microscopic examination. The  filters were  observed   under  a  10x objective  lens  of a binoculas  microscope for the presence  of  schistosome  eggs (plate 1).  Few  drops of water were  added  to the edge  of the nilon  mesh filter  during  microscopy to avoid  drying up,  and  for  easier  identification of  the schistosome eggs.   The  number of  eggs  obtained  per  10ml of urine specimen was counted  and  quantified as  intensity  of infection. Urinalysis  was carried  out using  Medi Test ‘Combi 9’ reagent  strip capable  of  detecting urinary  blood, protein and other  parameters.  The  criteria  for the establishment  of S. haematobium infection in a given specimen were, the presence  of  eggs  and / or  positive  urinalysis  test.  Candidates  with  negative  biochemical  and microscopic   tests  were used  as  controls.  Statistical analysis was  done using χ² (chi square)  tests  and  simple  correlation  coefficient r to compare differences, and  for the determination of associations  respectively. 

The percentage of males excreting eggs was 64.3% while the females were 59.1%. Intensity peak in the male subjects (922 eggs/10ml urine) occurred in the 10-14 years age group. For the females, intensity peaked (985 eggs/10ml urine) in the 0-4 years age group. After age 29 years, no female was found with eggs any longer but egg excretion continued in the males up to the very later years but on very minimal rates, fig. 2.  Heavy intensity (> 1000 eggs/10m/urine) occurred in 39.0% of egg excretes. 19.3% had moderate intensity (500 –1000 eggs/10ml urine), and 41.7% had light intensity (< 500 eggs/10ml urine) Individuals under 20 years had more moderate to heavy intensity than they had light intensity. 23.5% of males with positive egg count had heavy intensity against the 15.5% of the females. Generally the females were more intensely infected than the males, fig. 3. The difference  was  statistically  significant (χ²= p <0.001). The result of urinalysis showed that  haematuria occurred in 72.7%  of the participants while proteinuria occurred in 82.4%, with greater frequency of occurrence in the younger age groups. 

Table 1: Age and sex prevalence of S. haematobium infection  in the  study area.

DISCUSSIONS

This study has examined the prevalence pattern and intensity of Schistosoma haematobium in Odau community in the Niger Delta Area of  Nigeria.  The  infection  pattern  showed  a typical peak  prevalence  in the  early adolescence with males  having  a higher   rate.  This  agrees  with  results of similar  studies in  Schistosoma haematobium  endemic  areas  (Taylor  et al; 1990;  Ekanem  et al; 1994;  Gabr  et  al; 2000).

High prevalence rate of S. haematobium infection has been reported by some other authors in endemic areas (Pugh et al;  1980; Akokun, et al;  1994; Anosike et al;  1999). The high rate of the infection reported in the present study may be suggestive of the level of S. haematobium transmission in various foci in the community. The ponds are the main transmission foci in the community and are distributed all over the place. They provide a natural water source as well as serve as meeting point for the schistosome parasites, their intermediate host and the people. The people depend on these ponds for their fishing occupation, bathing and other domestic needs. Infection foci have also been traced to their farms. These ensure that the people continue being infected and re-infected since no intervention strategy has been carried out in the area. Individuals in their teens who are oftentimes engaged in water related activities that expose them to these infection sites run the risk of acquiring more infection and habouring more worms.

As a rural remote community, the inhabitants are predominantly farmers. The adult males and   females  are exposed  to the  infection. They either contract the infection from the nearby ponds in the community or those in their farms. The higher male prevalence may have resulted from their preponderance in the survey but may not be due to over exposure to the infection sites. There are some reported cases of higher male prevalence in some endemic areas (Pugh and Gilles, 1978; Ekanem et al; 1994). Some other studies have found no significant differences in gender prevalence (Forsyth and Bradley, 1966; Wilkins, 1977). The variations in the infection pattern may be attributed to differences in geographic and environmental setting cultural  and  religious  beliefs  in each endemic area (Wilkins, 1977;  Pugh & Gilles, 1978; Southgate and  Rollinson, 1987). Intensity estimates were based on mean egg counts in 10ml of urine obtained from the candidates. The egg counts rose with decreasing years and reduced with increasing years thus showing a negative correction. This is in agreement with results of intensity studies in other S. haematobium endemic areas (Wilkins, 1987; El-Harvey et al; 2000; Abdel-Wahab, et al; 2000). The intensity hike in children may be attributed to increased worm burden and the high fecundity rate of the parasite, while the opposite was encountered in adult and elderly subjects who probably have reduced schistosome worms  and  less eggs (Ogbe, 1995). Reduced worm burden in patients of older ages may also result from the development of concomitant immunity known to occur in the infection (Woolhouse et al; 1991). The differences in the male and females intensities of infection may reflect the degree of sensitization and host response to the invading parasites as well as the extent of worm burden in the individual subject. Studies of Etim (1995), on water contact activities and schistosomiasis among women in a rural community indicated that more women than men get more severe schistosomiasis infection due to educational and economic backwardness. They may be exposed to more intense infection than their male counterparts. S. haematobium infection has reached a hyperendemic level in the community studied owning to the high rates of the infection and intensity . This shows the degree of health burden faced by the inhabitants especially the women and children who have severe infections. There is therefore the need for an urgent control of Schistosoma haematobium infection in the  community, to alleviate their health problems.

REFERENCES