184
TRANSACTIONS OFTHBROYALSOCIETY OFTROPICAL MEDICINE ANDHYGIENE (1992)86, 184-186
Prevalence of hookworm infection and its association among resettlers in Gambela, Ethiopia Tesfaye Bulto*, Fisseha Haile Meskal, Tekola Endeshaw and Amare Dejene P.O. Box 1242, Addis Ababa, Ethiopia
with low haematocrit National Research Institute of Health,
Abstract
A cross-sectionalsurvey of hookworm infection and haematocrit (HCT) levels was conducted in 7 resettled villages and 3 indigenous villages on samplepopulations selectedby two-stagerandom sampling. Of 614 resettled personsand 187 indigenous persons, 65.5% and 60.4% respectively were infected with hookworm. Mean haematocritsfor 664 resettled and 222 indigenous personswere 33.1% and 35.2%, respectively. A significant association(odds ratio=2*65) was found between low haematocrit level (below the median for the samnleoouulation) and hookworm infection in the resettled population. Suggestionsare made on the need for f;rthe;studies and intervention programmes. Introduction
Hookworm disease, caused by both Ancylostoma duodenale and Necator americanus, is widespread in the humid western and south-western lowlands of Ethiopia (ARMSTRONG & CHANE, 1975; MCCONNELL & ARMSTRONG,1976; LEYKUN & TEDLA, 1985; TEDLA, 1986;
TEDLA & YEMANEH,1985). A study conducted in the Gambela Resettlement Scheme,3 months after the arrival of the resettled population, found an overall prevalence rate of 75% hookworm infection in the indigenous population and only 4.3% in the resettlers (ESHETEet aZ., 1986). Hookworm infection can causeor precipitate serious anaemiain a community whosestaplefood hasa low iron content (WHO, 1963, 1968). The present study was therefore conducted to monitor the appearanceof this problem in the immigrant population in Gambela, 5 yearsafter the establishmentof the resettlementscheme. Study area and population
One of the major resettlement schemesestablishedin south-west Ethiopia, following the 1984-1985 drought that affected the northern part of the country, was in Gambelaadministrative region. Gambelais 700 km west of Addis Ababa at about latitude 8”N and longitude 34”E, at an altitude of about 500 m. The mean annual rainfall is 1200 mm and mean relative humidity is between 45% and 75% (ANONYMOUS, 1979). There are 6 major resettlement sites in Gambela,each with 4 to 9 villages uniformly organized as co-operative farms. Each village has a population of 1000to 1200and the total resettled population at the time of the study was 37 575. The indigenous population in the vicinity of the resettlement schemesbelongs to the Anuak tribe. Although formally organized into a farmers’ association,the Anuaks produce no cash crops, and the adult males still travel away from their villages to gold fields or to coffeegrowing areasto make money. Materials and Methods
The study subjects were selected using a two-stage random sampling technique. Depending on size of the site, one or 2 villages were first randomly selectedfrom eachresettlement site. Indigenous villages were selected, basedon their proximity to the resettlementsites and accessibility. In the secondstage,the villages selectedwere censusedand a representativesamplesizefor eachvillage was determined basedon the proportions indicated by a previous study (ESHETEet al., 1986) to provide a confidence interval of 95%. The number of householdsrequired was then estimated and randomly selected, and all members of the selectedhouseholdswere included in the study. Heads of the selected households were informed of the study and requestedto take all membersof their householdsto the clinic for examination the follow*Authorfor correspondence.
ing day. At the clinic, a record was compiled for each subject containing name, code number, age and sex. The subjects were then interviewed, examined by a physician and their haematocrit was determined. An attempt was alsomadeto collect a stool specimenfrom eachsubject. Haematocrit determinations were made on capillary blood collected by finger prick in heparinized capillary tubes, which were centrifuged for 5 min. Stool specimenswere collected in cups containing 10% formalin and transported to the National Research Institute of Health in Addis Ababa for examination by the formol-ether concentration method (RITCHIE, 1948). Data were entered into a computer using D-Base III+@ and analysis was done first by SPSSPC+~ using descriptive techniques. The statistical significanceof differencfs between groups was tested by Student’s t test and x . The median haematocrit level of the sample populations was used asa dichotomized cut-off point and the statistical association between low haematocrit (below the median level) and hookworm infection was measuredby determining the odds ratio and 95% confidenceinterval (95% CI). Results
The overall male to female ratio of the samplepopulation was 1:1.1 for the resettled population and 1: 1.7 for the indigenous people. Among the indigenous population, more females participated in the study than males becausemost of the latter were away from their villages at the time of the study. Of 683 resettled personsand 232 indigenous persons sampled, 89.9% and 80.6%, respectively, provided stool specimens. The haematocrit was determined for 97.2% of resettled personsand 95.7% of the indigenous personssampled. The overall prevalencesof hookworm infection in the resettled and indigenous population above 6 months of age were 65.5% and 60.4% respectively (Table 1). The overall mean haematocrit for the resettled and indigenous personswas 33% and 35% respectively (Table 2). The difference between the prevalencerate of hookworm in the 2 populations was not significant, but the difference in the mean haematocrit levels was significant (FYO.0005, t test). The highest rate of hookworm infection (86.2) and the lowest mean haematocrit level (29%) were observed in Barro-5 resettled village. The lowest hookworm prevalencerate (29.9%) and the highest mean haematocrit level (36%) were observedin the resettled village known asOuballa-31. Among the indigenous villages, Kirre had the highest hookworm infection rate (86%) but it also had the highest meanhaematocrit (36%). The associationof low haematocrit with hookworm infection had a crude odds ratio of 2.65, (95% CI= 1.8-3.9) and 1.33 (95% CI=O.67-2.64) in the resettled and indigenouspopulations respectively. As shown in Table 3, the associationbetween low haematocrit and hookworm infection in the resettled population, when adjusted for
185 Table 1. Distribution of hookworm infection in Gambela, Ethiopia, by population, age and sex
4s (years)
Resettl;~~;ulatioion Indigenouspopulation Male Total Male Female Total Infected No. Infected No. Infected No. Infected No. Infected No. Infected examined (%) examined (%) examined (%) exazned (%) examined (%) examined (%)
0.5-5 6-14 15-44
All 345 ages
58 67
ii
z:: 2
291
68
iz 143 332:
2:
:: 63
103 171 237
2:
22 32 3
614 103
66
;:
100
;i :“7 :“4
z’;t
:7
53
62
120 15
2
:: 64
ii 2 :“o 187
Table 2. Haematocrit of resettled and indigenous population in Gambela, Ethiopia compared with a study in Helegen, north-west Ethiopia
Age (years)
E
Resettledpopulation SDb Median Range
x
Indigenouspopulation SD Median Range
Populationof Helegen” x SDb Range
33.9 4.8 ii 13-47 33.7 2.9 z; 26-40 38.9 4.8 ;;g;:; 32.9 4.9 19-44 34.6 3.3 23-43 38.9 5.0 2 15 (femalesonly) 32.3 5.7 33 13-43 36.1 4.0 36 25-49 40.1 ;:“9 25.7-54-5 215 (malesonly) 33.8 7.3 1l-47 38.6 4.6 30-48 40.7 30.9-50.5 All subjects 33.1’ 5.9 zi 11-47 35.2’ 3.8 2: 23-49 ‘ZEIN & MEKONNEN, 1987. b?i=Mean,SD=standarddeviation. ‘Difference betweenmeansfor resettledand indigenouspopulationsis significantat P
TRANSACTIONS OFTHBROYALSOCIETY OFTROPICAL MEDICINE ANDHYGIENE (1992)86, 184-186
Prevalence of hookworm infection and its association among resettlers in Gambela, Ethiopia Tesfaye Bulto*, Fisseha Haile Meskal, Tekola Endeshaw and Amare Dejene P.O. Box 1242, Addis Ababa, Ethiopia
with low haematocrit National Research Institute of Health,
Abstract
A cross-sectionalsurvey of hookworm infection and haematocrit (HCT) levels was conducted in 7 resettled villages and 3 indigenous villages on samplepopulations selectedby two-stagerandom sampling. Of 614 resettled personsand 187 indigenous persons, 65.5% and 60.4% respectively were infected with hookworm. Mean haematocritsfor 664 resettled and 222 indigenous personswere 33.1% and 35.2%, respectively. A significant association(odds ratio=2*65) was found between low haematocrit level (below the median for the samnleoouulation) and hookworm infection in the resettled population. Suggestionsare made on the need for f;rthe;studies and intervention programmes. Introduction
Hookworm disease, caused by both Ancylostoma duodenale and Necator americanus, is widespread in the humid western and south-western lowlands of Ethiopia (ARMSTRONG & CHANE, 1975; MCCONNELL & ARMSTRONG,1976; LEYKUN & TEDLA, 1985; TEDLA, 1986;
TEDLA & YEMANEH,1985). A study conducted in the Gambela Resettlement Scheme,3 months after the arrival of the resettled population, found an overall prevalence rate of 75% hookworm infection in the indigenous population and only 4.3% in the resettlers (ESHETEet aZ., 1986). Hookworm infection can causeor precipitate serious anaemiain a community whosestaplefood hasa low iron content (WHO, 1963, 1968). The present study was therefore conducted to monitor the appearanceof this problem in the immigrant population in Gambela, 5 yearsafter the establishmentof the resettlementscheme. Study area and population
One of the major resettlement schemesestablishedin south-west Ethiopia, following the 1984-1985 drought that affected the northern part of the country, was in Gambelaadministrative region. Gambelais 700 km west of Addis Ababa at about latitude 8”N and longitude 34”E, at an altitude of about 500 m. The mean annual rainfall is 1200 mm and mean relative humidity is between 45% and 75% (ANONYMOUS, 1979). There are 6 major resettlement sites in Gambela,each with 4 to 9 villages uniformly organized as co-operative farms. Each village has a population of 1000to 1200and the total resettled population at the time of the study was 37 575. The indigenous population in the vicinity of the resettlement schemesbelongs to the Anuak tribe. Although formally organized into a farmers’ association,the Anuaks produce no cash crops, and the adult males still travel away from their villages to gold fields or to coffeegrowing areasto make money. Materials and Methods
The study subjects were selected using a two-stage random sampling technique. Depending on size of the site, one or 2 villages were first randomly selectedfrom eachresettlement site. Indigenous villages were selected, basedon their proximity to the resettlementsites and accessibility. In the secondstage,the villages selectedwere censusedand a representativesamplesizefor eachvillage was determined basedon the proportions indicated by a previous study (ESHETEet al., 1986) to provide a confidence interval of 95%. The number of householdsrequired was then estimated and randomly selected, and all members of the selectedhouseholdswere included in the study. Heads of the selected households were informed of the study and requestedto take all membersof their householdsto the clinic for examination the follow*Authorfor correspondence.
ing day. At the clinic, a record was compiled for each subject containing name, code number, age and sex. The subjects were then interviewed, examined by a physician and their haematocrit was determined. An attempt was alsomadeto collect a stool specimenfrom eachsubject. Haematocrit determinations were made on capillary blood collected by finger prick in heparinized capillary tubes, which were centrifuged for 5 min. Stool specimenswere collected in cups containing 10% formalin and transported to the National Research Institute of Health in Addis Ababa for examination by the formol-ether concentration method (RITCHIE, 1948). Data were entered into a computer using D-Base III+@ and analysis was done first by SPSSPC+~ using descriptive techniques. The statistical significanceof differencfs between groups was tested by Student’s t test and x . The median haematocrit level of the sample populations was used asa dichotomized cut-off point and the statistical association between low haematocrit (below the median level) and hookworm infection was measuredby determining the odds ratio and 95% confidenceinterval (95% CI). Results
The overall male to female ratio of the samplepopulation was 1:1.1 for the resettled population and 1: 1.7 for the indigenous people. Among the indigenous population, more females participated in the study than males becausemost of the latter were away from their villages at the time of the study. Of 683 resettled personsand 232 indigenous persons sampled, 89.9% and 80.6%, respectively, provided stool specimens. The haematocrit was determined for 97.2% of resettled personsand 95.7% of the indigenous personssampled. The overall prevalencesof hookworm infection in the resettled and indigenous population above 6 months of age were 65.5% and 60.4% respectively (Table 1). The overall mean haematocrit for the resettled and indigenous personswas 33% and 35% respectively (Table 2). The difference between the prevalencerate of hookworm in the 2 populations was not significant, but the difference in the mean haematocrit levels was significant (FYO.0005, t test). The highest rate of hookworm infection (86.2) and the lowest mean haematocrit level (29%) were observed in Barro-5 resettled village. The lowest hookworm prevalencerate (29.9%) and the highest mean haematocrit level (36%) were observedin the resettled village known asOuballa-31. Among the indigenous villages, Kirre had the highest hookworm infection rate (86%) but it also had the highest meanhaematocrit (36%). The associationof low haematocrit with hookworm infection had a crude odds ratio of 2.65, (95% CI= 1.8-3.9) and 1.33 (95% CI=O.67-2.64) in the resettled and indigenouspopulations respectively. As shown in Table 3, the associationbetween low haematocrit and hookworm infection in the resettled population, when adjusted for
185 Table 1. Distribution of hookworm infection in Gambela, Ethiopia, by population, age and sex
4s (years)
Resettl;~~;ulatioion Indigenouspopulation Male Total Male Female Total Infected No. Infected No. Infected No. Infected No. Infected No. Infected examined (%) examined (%) examined (%) exazned (%) examined (%) examined (%)
0.5-5 6-14 15-44
All 345 ages
58 67
ii
z:: 2
291
68
iz 143 332:
2:
:: 63
103 171 237
2:
22 32 3
614 103
66
;:
100
;i :“7 :“4
z’;t
:7
53
62
120 15
2
:: 64
ii 2 :“o 187
Table 2. Haematocrit of resettled and indigenous population in Gambela, Ethiopia compared with a study in Helegen, north-west Ethiopia
Age (years)
E
Resettledpopulation SDb Median Range
x
Indigenouspopulation SD Median Range
Populationof Helegen” x SDb Range
33.9 4.8 ii 13-47 33.7 2.9 z; 26-40 38.9 4.8 ;;g;:; 32.9 4.9 19-44 34.6 3.3 23-43 38.9 5.0 2 15 (femalesonly) 32.3 5.7 33 13-43 36.1 4.0 36 25-49 40.1 ;:“9 25.7-54-5 215 (malesonly) 33.8 7.3 1l-47 38.6 4.6 30-48 40.7 30.9-50.5 All subjects 33.1’ 5.9 zi 11-47 35.2’ 3.8 2: 23-49 ‘ZEIN & MEKONNEN, 1987. b?i=Mean,SD=standarddeviation. ‘Difference betweenmeansfor resettledand indigenouspopulationsis significantat P
