RESULTS

Description of the study population - The mean age of respondents to the questionnaire was 39.4 years [standard deviation (SD)=16.3, median age=35.5 years] and more than 95% of respondents were females. The age of the 240 subjects sampled ranged from 2 to 84 years with a mean age of 20.6 years (SD=19.3, median age=11.0). Fifty-three percent of those sampled were female and 47% male. Seventy-one percent of respondents had some formal education; the majority (51.6%) had some primary education (completed 1-6 years) and 19.4% had some years of secondary education (completed 7-12 years).

Prevalence and intensity of A. lumbricoides and T. trichiura - The overall prevalence of A. lumbricoides and T. trichiura in these four communities was 45% (95% CI 39.0-51.9) and 38% (95% CI 31.8-44.4), respectively (Table I). Over a quarter (25.8%) of the 240 stool specimens examined had double infection of both A. lumbricoides and T. trichiura. Table I shows the differences in prevalence and intensity of Ascaris and Trichuris infection by age group and community. Overall, infections of Ascaris were mostly moderate and light, except in El Chaguite where there were heavy infections. There were primarily light infections of T. trichiura, except again in El Chaguite where moderate infections were observed. There were no heavy infections of T. trichiura.

El Llano had the lowest prevalence overall of both A. lumbricoides and T. trichiura and the least number of T. trichiura infections across all age groups. Twenty-two percent of the population surveyed in this community was infected with Ascaris and 11% were infected with Trichuris. Most infections, including one case of heavy infection and two cases of moderate infection with Ascaris, were found in children 2-4 years old and 5-12 years old. However, there were no infections of Trichuris in the 2-4 age group.

El Chaguite was the community with the highest prevalence of Ascaris and Trichuris; 82% of those surveyed had infections of Ascaris and 71% had infections of Trichuris. El Chaguite had much higher rates of infection in all age groups with A. lumbricoides and T. trichiura. Most infections of T. trichiura occurred in those 5-12 years old followed by individuals >12 years old.

The prevalence of Ascaris in Santa Ines and El Chaguite-Belen was 29% and 52%, respectively. The prevalence of Trichuris in each of these communities was 30% and 43%, respectively. In Santa Ines, individuals aged 2-4, had the highest frequency (40%) of moderate Ascaris infection, while those aged 5-12 and >12 had substantial frequencies (close to 30%) of both moderate and light infections. Individuals aged 5-12 years had the highest frequency (48%) of light infections of T. trichiura. Twenty percent of those >12 years old had light infections of Trichuris. In El Chaguite-Belen the highest frequency of infection (moderate and light) of Ascaris and Trichuris occurred in those aged 5-12, followed by those aged >12. There was only one infection of Ascaris or Trichuris in children aged 2-4 in this community (Table I).

Fig. 2 shows the overall intensity of A. lumbricoides infections in all the communities. Children aged 2-4 had the heaviest infections while children aged 5 to 12 were most frequently infected with moderate and light infections compared to other age groups. Overall, there were more intense infections (heavy and/or moderate) of Ascaris than Trichuris in all age groups. Fig. 3 shows the overall intensity of T. trichiura infections in all the communities. Children aged 5 to 12 more frequently had moderate and light infections of Trichuris compared to other age groups. There were more light infections of Trichuris in children aged 5 to 12 than there were light infections of Ascaris in the same age group. Also, individuals >12 years were more frequently infected with light infections of Trichuris than they were with light infections of Ascaris.

Socio-demographic characteristics of household by infections of A. lumbricoides and T. trichiura - Univariate analysis was used to examine relationships between socio-demographic variables reported for the households and infections of A. lumbricoides and T. trichiura. Infections of A. lumbricoides by household associated with infections of T. trichiura and vice versa (p=0.001) (Tables II, III).

The four communities differed markedly from each other with respect to the prevalence of infections by both parasites, but only A. lumbricoides infection was significantly associated with infection by location of the household (p=0.03) (Table II). A higher percentage of households located in El Chaguite or El Chaguite-Belen, had members infected with A. lumbricoides than households in El Llano or Santa Ines. There were significant differences in prevalence between communities. When El Chaguite was compared univariately with the other three communities, in every instance, living in El Chaguite was significantly associated (p<0.01) with infections of A. lumbricoides or T. trichiura.

There was an association between the number of children 2 to 5 years old and the number of children 6-14 years old living in a household, and infection by A. lumbricoides in members of the household (p=0.001, p=0.001, respectively) (Table II). Households with children in these age groups had a greater frequency of Ascaris infection compared to households with no children in these age groups (Table II). Similarly, the number of children 6-14 years old in the household was also associated with infections of T. trichiura (p=0.01) (Table III). Households with children in this age group had a greater frequency of Trichuris infections than those households with no children in the age group.

Education was associated with A. lumbricoides infection within households (p=0.01) (Table II). A lower proportion (25%) of family members was infected with A. lumbricoides in households where the respondent had a secondary education than in households where the respondent had no formal education (66.7%).

Gender was examined as a possible variable associated with parasitoses. Approximately 45% of males and 45% of females of all ages surveyed were infected with A. lumbricoides. Approximately 41% of males and 35% of females of all ages were positive for infections with T. trichiura. There was no significant difference with respect to gender regarding infection with either Ascaris (p=0.97) or Trichuris (p=0.35) in the population surveyed. Also, there was no significant difference between gender with reference to intensity for Ascaris (p=0.64) or Trichuris (p=0.20) infections.

Associations between sanitary practices and infections of Ascaris or Trichuris by household was also examined. In this respect, certain variables such as lack of a latrine (p=0.04, p=0.03) (Tables II, III), respondents defecating in a site other than the latrine (p=0.01, p=0.04) (Tables II, III), children defecating in a site other than the latrine (p=0.02) (Table II), and children with a recent history of diarrrhea (p=0.002) (Table II) were associated with infections of either A. lumbricoides or T. trichiura respectively. In each case, households that did not own a latrine, or households where respondents and children did not always use the latrine for defecation, or where children were reported with diarrhea, had a higher percentage of members with infections of either helminth.

The most common reason given by respondents who did not always use the latrine for defecation, was that the family did not own one (31.6%). Other common reasons given were that the latrine was broken (26.3%) or that it was too far (21.1%). Twenty-one percent of respondents had reasons other than those given above. The most common reasons given by respondents for children not always using the latrine was that the children did not know how to use it because they were too young (30%), that the latrine was too far (20%), and that the household did not own one (20%). Another 16.7% said that the latrine was broken, and 13.3% indicated other reasons.

Although most individuals (73.7%) did not know how someone could become infected with Ascaris, when specifically asked and shown the preserved specimen of Ascaris, 34.4% recalled that someone in the household had passed a worm at some time. The answers respondents gave to the question of how children became infected with worms in general varied, but most (40.3%) thought that "dirty hands or filth" was the cause. However, over a third of respondents (33.9%) did not know how children acquired worms. The remainder (25.9%) thought that water, candy, milk, eating bad food, etc. caused worms in children.

Multivariate analysis of variables associated with infections of A. lumbricoides and T. trichiura - Multivariate analysis was performed on all the variables with p-value of 0.05 or less by univariate analysis for both A. lumbricoides and T. trichiura, in order to eliminate confounding variables. Multivariate analysis identified the following variables as those statistically associated with infections of A. lumbricoides: number of children aged 2-5 or 6-14 living in the household (p=0.01 and p=0.04, respectively), report of recent history of diarrhea in children in the household (p=0.01) and members of the household coinfected with T. trichiura (p=0.02). The only variable that was associated with T. trichiura infection was the number of children 6 to 14 years old living in the household (p=0.01) (Table IV).

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