Endemicity of schistosomiasis in some parts of Anambra State, Nigeria

Investigation on the prevalence of infections with schistosoma was carried out amongst inhabitants of two local government areas (LGAs), Nigeria between October 2007 and September 2008. A total of 2064 randomly selected subjects had their urine and stool samples examined for eggs of Schistosoma and 323 (15.7%) were excreting eggs of S. haematobium in their urine with geometric mean egg count (GMEC) of 10.1 eggs/10 ml of urine. No eggs of S. mansoni were found. Prevalence of infection varied between 12.8 and 19.8% between the LGAs, but the differences were not statistically significant (P>0.05). Prevalence also varied significantly between the age groups (P<0.05) with peak occurring among persons aged 11 to 20 years and decreased thereafter. There was a close association between haematuria and the presence of eggs of S. haematobium in the urine (P<0.05). People that tested positive for schistosomiasis were 26.4 times at greater risk (P<0.001) of haematuria as compared to those who tested negative. The result indicated 83.1% sensitivity and a specificity of 91.4%. Farmers (OR=2.31; P<0.05) were significantly at greater risk of schistosomiasis infection as compared to the artisans. The importance of these findings and their implications for control of the disease in Anambra State are discussed.


INTRODUCTION
Schistosomiasis (also known as Bilharziasis) is the disease caused by a blood fluke (trematode) of the genus Schistosoma.The intermediate host is aquatic snail.Adult schistosome worms live in mammalian host.Schistosomiasis ranks second to malaria in terms of prevalence and persistence with grave public health and socio-economic importance in endemic communities (Sleigh et al., 1998;Utzinger et al., 2003;Kazibwe et al., 2006).Five species of schistosomes are recognized as important metazoan parasites of humans.They include schistosoma mansoni, Schistosoma haematobium and schistosoma japonicum which are widespread, while schistosoma intercalatum and schistosoma mekongi have more restricted distribution (Rollinson and Simpson, 1987;WHO 2002).
S. mansoni, the causative agent of intestinal schistosomiasis, is transmitted by aquatic snail of the genus Biomphalaria which thrives in irrigation canals and along lake shores (Jordan, 2000).S. haematobium which causes urinary schistosomiasis is transmitted by aquatic snails of the genus Bulinus, which inhabit less permanent water bodies (Nwoke, 1989).*Corresponding author.E-mail: feldendiagnostics@yahoo.com.
Urinary schistosomiasis is an infectious disease of the tropics and sub-tropics, but highly preventable.It is one of the most widely spread among the parasitic helminthic infections that affect man.It is an occupational risk encountered in rural areas of developing countries, where potable water is scarce.The disease is indicated by the presence of blood in urine and sometimes by pains on urinating or after urinating.Man contacts the disease when he comes in contact with infected water bodies while carrying out necessary daily activities such as farming, fishing, laundry, bathing and swimming (Dalton and Pole, 1978;Wright, 1988).These socio-economic activities and symptoms are not uncommon among the inhabitants of Anambra State, Nigeria, especially in the chosen Local Government Areas.
With many rivers, ponds, irrigated farming and burrow pits, Anambra State has diverse freshwater environments that offer numerous favourable habitats for aquatic snails that serve as intermediate hosts.Some symptoms and comolications are associated with this disease.These include swimmer's itch, dysuria, haematuria and suprapubic pain (Nagi et al., 1999).Knowledge on the endemicity of the disease in the chosen study area is important, because of the existing physical features and lack of social amenities in the area.In Amagunze village, Enugu State, Nigeria, Ozumba et al. (1989), reported 79% prevalence of S. haematobium, and intensity of 49 eggs/10 ml of urine among 119 school children aged 5 to 12 years.In a survey conducted in one secondary school and three primary schools near Agulu Lake in Anambra State, Ekejindu et al. (1999) recorded prevalence rate of 11.8% with a geometric mean egg count of 9.9 eggs/10 ml of urine.In Imo State Nigeria, Nnoruka (2000) reported prevalence ranging from 14.2 to 44.9% with geometric mean egg counts of 16 to 46% eggs/10 ml of urine.Thus, this work will also serve the purpose of bridging the information gap for adequate control of the disease in the state.The objectives of this paper were to elucidate factors influencing the existence or spread of schistosomiasis and to determine the endemicity of schistosomiasis in the study areas.

Study area
The study areas are two LGAs in Anambra State, namely, Orumba North and Orumba South.These lie between longitude 6°37′E and 7°27′E and latitude 5°40′N and 6°48′N.The area has typical semitropical rainforest vegetation, characterized by fresh water swamps.It has a humid climate with a temperature of about 30.6°C (87°F) and a rainfall between 152 and 203 cm annually.The major rivers in the state are Rivers Niger, Anambra, Ulasi and Ezu.But there are other smaller streams, lakes, ponds and burrow pits.The inhabitants are predominantly farmers and the area lacks pipe bornewater.The inhabitants make use of water mainly from streams, rivers, and ponds for all their domestic activities and as the major sources of drinking water.The selection of the study area was Ugochukwu et al. 55 based on the long existing lack of social amenities in the areas.

Sample collection (Urine/Stool)
Informed consent was obtained from all the people before sample collection.The study was on people of ages between 0 and 60 years.This population was made up through selections from the three thousand questionnaires distributed to the schools and other relevant establishments chosen for the research.This work started with the researchers visiting the twenty-one communities in the study area for fact findings.There, some elderly people were approached for discussions on relevant issues about their communities.
Questions were asked about their sources of water for drinking and other domestic activities.Information on nearness to existing streams and rivers and existence of ponds and similar stagnant waters and their public uses were sought.The occupation of the people especially the nature of farming activities was discussed.The elders willingly answered the questions.Information obtained placed sixteen communities' suspects for existence of Schistosoma and eliminated five for lack of Schistosoma friendly environments.
The choice of ten communities, five for each LGA, was made through random sampling amongst the sixteen suspect communities.Similar exercise was performed in the choice of primary and secondary schools for sample collection.Other sources of people for sampling were the LGA headquarters, health centres, people from large families and some in their work places.The questionnaires which contained necessary questions about schistosomiasis were given to the selected people from the choice schools, other chosen establishments and places.Finally, two thousand and sixty four questionnaires that were correctly answered were selected for the work.Arrangements were later made with the people for the sample collection.Following the mobilization of the communities, 2064 persons were randomly selected from the two LGAs as study participants Figure 1.A personal data form was used to obtain the following community, village, household names/code, age, sex, occupation and school.Two wide-mouthed, screw-capped, prenumbered, sterilized plastic containers were given to each person, to collect stool and urine samples.The subjects were instructed on how to collect the stool and urine samples.Urine samples were collected between the hours of 10 am and 2 pm along with the stool samples.For urine, they were instructed to collect mid-stream urine not less than an estimated volume of 10 ml and have the last few drops of the urine passed included in the bottles.The last drops often contain the highest number of eggs (Chessbrough, 2002).Females in their monthly periods were remarked and excluded from visible haematuria counts.This was necessary to avoid false (positive) results (Savioli and Mott, 1989).Urine samples were collected between the hours of 10 am and 2 pm along with the stool samples.These were taken to the laboratory in ice-block packed coolers where they were processed and analysed.

Examination of urine for eggs
Urine examination for S. haematobium eggs was carried out on the 2064 samples.The standard centrifugation method as described by Cheesbrough (2002) was employed.The content of each specimen bottle was well mixed after which a sterile disposable 10 ml syringe was used to draw urine sample into centrifuge tube and this was centrifuged for 5 min at 3,000 rpm.The supernatant was decanted while the sediment was re-mixed by tapping the bottom of the tube and a little drop placed on a slide.This was covered with a cover slip and examined microscopically, using ×10 and ×40 objectives and eggs of S. haematobium identified by their possession of   terminal spine.This process was carried out on the remaining sediments.The total counts were summed up before eggs/10 ml of urine was calculated for each sample.

Examination of stool for eggs
To detect the eggs of S. mansoni, qualitative and quantitative analyses were done on the stool samples.For direct qualitative examination, the stool samples were first homogenized with an applicator.A light emulsion of the homogenized stool was made on the slide with normal saline using an applicator, covered gently with a cover slip.This was subsequently examined microscopically using ×10 and ×40 objectives, respectively.For the quantitative method, the formol-ether concentration technique as described by Cheessbrough (2002) was used.

Biomedical testing (Rapid Screening) of urine samples for haematuria
All the urine samples of the 2064 subjects were screened for blood (haematuria) except those whose blood presence was visible.Haematuria was assessed using chemical reagent strips (medi-test Combi-9).The strip is prepared to detect blood in urine.The blood detecting area contains a peroxidase compound and O-tolindine as chromogen.The principle of the test is based on the pseudo- peroxidative activity of haemoglobin and myoglobin which catalyses the oxidation of an indicator by an organic hydroxide producing a green colour.Urine with blood was recorded variously as positive (+, ++, +++) or negative when these changed from yellow to light, deep or very deep green, respectively or negative when there is no colour change.The test was performed by dipping the strip into fresh urine sample for approximately two seconds.It was removed and the tip of the strip tapped lightly on the edge of the urine container to remove the excess urine.The strip was then matched and compared with the colour chart on the label (Cheesbrough, 2002).The results of the colour changes that took place within two seconds were recorded.

Overall prevalence of urinary schistosomiasis in the study area
Out of the 2064 people examined for urinary schistosomiasis, 323 (15.7%) were infected.The overall age related intensity of urinary schistosomiasis in the study area is shown in Table 5.People of ages 11 to 20 years with 14.0 eggs/10 ml of urine had the highest intensity.They closely followed by least were from people of ages 51 to 60 years with 2.3 eggs/10 ml of urine.
Of the 2064 people who participated in the study, 15.7% (n=323) were infected with urinary schistosomiasis, Ugochukwu et al. 57 while 84.3% (n=1741) were uninfected.to 60 years were the least infected with 5 (6.7%)Data indicated that among those infected with schistosomiasis, majority (39.3%) were of the age group 11 to 20 years, followed by those between the age of 21 and 30 years (22.9%).
The age group with the least prevalence of schistosomiasis is 51 to 60 years.With regards to the occupation of subjects, those with the highest frequency of schistosomiasis were farmers (36.2%) followed by students/pupils (22%) and traders (21.4%).The occupational group with the least prevalence of schistosomiasis is the artisans (2.8%).The frequencies of other age and occupational groups are shown in Table 7.
Logistic regression analysis indicated that subjects of age groups 0 to 10 years (odd ratio (OR)=3.53;P<0.01) and 11 to 20 years (OR=3.85;P<0.01) were significantly at greater risk of schistosomiasis infection compared to the age groups 51 to 60 years.However, those in age groups 21 to 30, 31 to 40 and 41 to 50 years had insignificant (P=0.136;P=0.518; P=0.206), greater odds (OR=2.18;OR=1.58;OR=2.09) of schistosomiasis compared to those in group 51 to 60 years.Considering the occupation of subjects, data further indicated that farmers (OR=2.68;P<0.01) and traders (OR=2.31;P<0.05) were significantly at greater risk of schistosomiasis infection as compared to the artisans.In contrast, civil servants, students/pupils and fishermen had insignificantly greater risk of schistosomiasis (OR=1.72,P=0.215; OR=1.62,P=0.258; and OR=2.18,P=0.059) as compared to the artisans.Of the 323 people who had schistosomiasis infection in this study, 50.2% (n=162) presented with haematuria, while 49.8% tested negative for haematuria.Data indicated that among those who had haematuria, majority (51.2%, n=83) were of the age group 11 to 20 years, followed by those of age 0 to 10 years (16.7%, n=27) and 21 to 30 years (16.0%,n=26).The age group with the least prevalence of haematuria is 51 to 60 years (1.2%, n=2).The frequencies of other age groups are as shown in Table 9.
Table 9 indicates that among subjects who tested positive for schistosomiasis infection, 50.2% had haematuria, while 49.8% indicated no haematuria.Amongst those who tested negative for schistosomiasis, 0.7% tested positive for haematuria, while 91.6% tested negative for haematuria.
Logistic regression analysis indicated that subjects of younger age groups (0 to 10, 11 to 20, 21 to 30, 31 to 40, and 41 to 50 years) were not at significantly greater risk of haematuria as compared to those in the age group 51 to 60 years.Data further indicated the sensitivity and specificity of the diagnostic test at each age group.
Furthermore, data indicated that subjects who tested positive for schistosomiasis were 26.4 times at greater risk (P<0.001) of haematuria as compared to those who tested negative for the infection.The test result indicated 83.1% sensitivity and a specificity of 91.4%, thus indicating that the haematuria test may be a very useful diagnostic tool for the detection of infections.

Data analysis
Descriptive data was expressed as frequencies and percentages for categorical data.Logistic regression model was used to determine the predictor risk factors of urinary Schistosomiasis infection and haematuria.Statistical significance was set at P<0.05.All statistics were done using Statistical Package for Social Sciences (SPSS) for windows (version 20.0).

Community prevalence
Prevalence and intensity of S. haematobium in this area are relatively low (15.7%) and 10.1 eggs/10 ml of urine, respectively, while S. mansoni is not present.According to WHO (1985), this should be considered low, but infection is wide spread in the area.The low prevalence and intensity obtained are in accord with other studies in this area such as Nale et al. (2003) in Adamawa State (11.5%),Ekejindu et al. (2002) in Anambra State (11.8%),Akogun (1986) in Malumfashi, Bauchi State (17%), Istifanus et al. (1990) in Malumfashi (17%), Okoli and Odaibo (1999) among pupils in Ibadan (17.4%), and Fajewonyomi and Afolabi (1994) among pupils in Ile-Ife, Oyo State (20.50%).Among those infected with schistosomiasis, majority (39.3%) were of the age group 11 to 20 years, followed by those between the ages of 21 and 30 years (22.9%).Analysis further indicated that people of age groups 0 to 10 years (OR=3.53;P<0.01) and 11 to 20 years (OR=3.85;P<0.01) were significantly at greater risk of schistosomiasis infection.This is further evidenced by the intensity results where people of 11 to 20 and 0 to 10 years had geometric mean egg count (GMEC) of 14.0 eggs/10 ml of urine and 11.2 eggs/10 ml of urine, respectively as compared to relatively lower egg counts in other age groups.This is because; these age groups are much more in contact with infected water bodies through swimming, laundry and other domestic and commercial activities that need streams and ponds.This is in accord with the age-related pattern of distribution of schistosomiasis in man reported by authors like Egwunyega et al. (1994), Ekejindu et al. (1999), Dunah and Bristone (2000), Daniel et al. (2001) and Nale et al. (2003).The prevalence rates among the communities in the study area ranged from 12.8% in Ndiowu in Orumba North LGA to 19.8% in Omogho for urinary schistosomiasis.The documented reports of these authors support the statement that endemicity is wide spread in Nigeria (Cowper, 1973; Ejezie et al., 1991;Fajewoyomi and Afolabi, 1994;Ekejindu et al., 1999;Anosike et al., 1992).There was a close association between haematuria and the presence of S. haematobium (P<0.05).Data indicated that people who tested positive for schistosomiasis were 26.4 times at greater risk (P<0.001) of haematuria as compared to those who tested negative.The result further indicated 83.1% sensitivity and a specificity of 91.4% thus indicating that the haematuria test may be a very useful diagnostic tool for the detection of schistosoma infections.This agrees with the reports of Akogun and Obadiah (1996), Anosike et al. (2001a) andVender Werf et al. (2003) that had such association.
With regards to occupation of the people, those with the highest frequency of schistosomiasis, were farmers (36.2%).Data further indicated that farmers (OR=2.68;P<0.01) and traders (OR=2.31;P<0.05) were significantly at greater risk of infection.This is because farmers are unavoidably in contact with infected water due to the nature of their duty, and majority of the people in the area are farmers.Most of the traders also combine farming with trading.Considering occupation of the people, those in age groups 21 to 30, 31 to 40, and 41 to 50 years had insignificant (P=0.136;P=0.518; P=0.206) greater odds (OR=2.18;OR=1.58;OR=2.09) of schistosomiasis as compared to those in group 51 to 60 years.This is because these are the age groups that engage in farming business.

Conclusion
It is evident from the results that the study area is endemic for urinary schistosomiasis.This result is similar to what previous authors obtained in some other areas of the state.There is need therefore for urgent health programs aimed at controlling the infection in the state.The state government should see that pipe-born water is provided for every community in the state.Better systems of waste collection and disposal should be put in place to help make the environment more hygienic.Drugs should also be provided for those suffering from the disease.

Table 1 .
Overall prevalence of urinary schistosomiasis in the study area.

Table 2 .
Prevalence of urinary schistostomiasis in Orumba North LGA.

Table 4 .
Overall Age-related prevalence in the study area.

Table 5 .
Age related intensity in urinary Schistosomiasis in the study area.

Table 6 .
Overall prevalence of urinary schistosomiasis according to age groups and occupation of subjects.

Table 7 .
Logistic regression model of the predictors of urinary Schistosomiasis in the people.
*Significant (P<0.05 or P <0.01).† Reference category against which the other categories are matched.‡ Age-adjusted logistic regression analysis.

Table 8 .
Overall prevalence of haematuria according to age groups amongst people who presented schistosomiasis.

Table 9 .
Overall prevalence of haematuria according to Schistosomiasis status.

Table 10 .
Logistic regression model indicating the influence of age and schistosomiasis infection status on haematuria,

Factor Odds ratio 95% Confidence interval P-value (2-tailed) Sensitivity Specificity Age group (years)
Figure 1.Map of Orumba North and South LGAs showing sampling points.