Lessons from a study in a rural community from southern Mexico: risk factors associated to transmission and reinfection of gastrointestinal parasites after albendazole treatment

Abstract

Purpose: To determine the prevalence of gastrointestinal parasites and evaluate the effect of a single dose of treatment with albendazole in a sentinel group from a rural community in southern Mexico.

Methods: Stool samples were collected from 1456 individuals aged ≥1 year during consecutive days, and examined for helminth infection using the modified Stoll dilution method. Additionally, 104 individuals were treated with a single dose of albendazole and evaluated over 21 weeks to assess reinfection. Questionnaires were administered to obtain individual and household-level data pertaining to behavior, demography, and socioeconomic status. Risk factors for reinfection after albendazole administration were determined using multiple logistic regression analyses.

Results: The prevalence of Ascaris lumbricoides was 73.9% (95% confidence interval [CI] = 71.56%-76.14%). Albendazole was 100% effective, but eggs began to be detected by 9-12 weeks posttreatment, increasing to 100% after 21 weeks. Logistic regression analysis revealed that all individuals from this study had a probability of reinfection of 1.65× each week after treatment. The prevalence of Trichuris trichiura was 57.2% (95% CI = 54.62%-59.77%) and chemotherapy was 34.7% effective. The prevalence for other minor gastrointestinal parasites ranged from 0.2% to 29.7%.

Conclusion: This was a comprehensive study on gastrointestinal parasites in a rural community from southern Mexico and, to the best of the authors' knowledge, is the first time that the effect of albendazole has been evaluated for a period of over 21 weeks following its administration. Risk factors associated with parasite transmission were linked to poverty and lack of hygiene, such as, defecating in open places, living customs (drinking piped water and/or from a well), and absence of knowledge about transmission life cycle of the parasites. Studies of this kind should be linked to health education and improvement of access to clean water and adequate sanitation to consolidate morbidity control and enhance sustainability.

Keywords: Ascaris lumbricoides; Trichuris trichiura; albendazole; polyparasitism; risk factors.

Figure 1

Cumulative prevalence of Ascaris lumbricoides cases in three age groups (children, teenagers, and adults) over a 21-week period after treatment.

Figure 2

Ascaris lumbricoides reinfection probability, estimated by a logistic regression in function of posttreatment weeks, in 104 volunteers from Texán de Palomeque, Yucatan, Mexico, where X = probability of reinfection in week X.