Intestinal Helminthiasis among Reproductive Age Women

Intestinal helminth infections are a significant public health problem for Vietnamese women, but prevalence and risk factor data are scarce. The objectives of this paper were to 1) determine the prevalence of helminth infections among women; 2) investigate interactions among intestinal helminth species in individuals and 3) identify risk factors that contribute to intestinal helminth infections. In a nationwide survey conducted in 1995, 9,550 households in 53 provinces were covered using a stratified two-stage cluster survey. Stool specimens were examined by Kato-Katz technique. Of 5,127 women, 76% were infected with one or more helminth species, 36% with hookworm, 59% with Ascaris lumbricoides and 28% with Trichuris trichiura. A. lumbricoides and T. trichiura were more likely to be concurrent than expected by chance. There was significant interaction between prevalence and intensity of infection in all three species. All three helminth species were more common in certain ecologic zones than others. Hookworm infection was associated with farming [Odd ratio (OR)=2.1] and lack of a closed latrine (OR=2.0), A. lumbricoides with use of untreated feces as fertilizer (OR=1.2) and coinfection with T. trichiura (OR=2.1) and T. trichiura with A. lumbricoides co-infection (OR=2.1). Our findings suggest that reproductive-age women, especially rural farmers, should be included among the high priority groups for helminth control programs through mass chemotherapy and improving sanitation. of intestinal parasites in Vietnam. Published estimates report rates of 50-95% for Ascaris lumbricoides, 30-68% for hookworm and <189% for Trichuris trichiura (Nguyen Duy Toan, 2000). The importance of helminth infections is due largely to their impact on nutritional status, including protein energy and micronutrient malnutrition (Crompton and Nesheim, 2002), with resultant effects on hemoglobin levels (Stoltzfus et al, 1997), cognitive development (Nokes et al, 1992a,b; Sakti et al, 1999), productivity (Gilgen et al, 2001), and pregnancy outcomes (Steketee, 2003; Stephenson et al, 2000). Existing data from Vietnam document high rates of helminth inSOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 866 Vol 37 No. 5 September 2006 fections in selected areas (Nguyen Duy Toan, 2000) and a disproportionate impact on women (Needham et al, 1998). However, detailed information with broad geographic coverage is lacking. In 1995, the National Institute of Nutrition (Vietnam), National Institute of Malariology, Parasitology and Entomology (Vietnam), UNICEF (Vietnam), and the Centers for Disease Control and Prevention (USA) conducted a nationwide health and nutrition survey. Anemia rates were measured for all demographic groups. Stool specimens were examined for women of reproductive age only. The results of this extensive survey remain unpublished, although a preliminary analysis was carried out. We performed an analysis of these data to 1) determine the prevalence of helminth infections among women across all regions of Vietnam, 2) investigate interactions among different intestinal helminth species in individuals, and 3) identify risk factors that contribute to intestinal helminth infections. Although the survey was carried out a decade ago, environmental conditions have not changed dramatically in Vietnam such that the information from the survey is still valid for program planning, as are the relationships explored in this analysis. The information also provides a baseline against which to measure public health improvements. MATERIALS AND METHODS Sample design and description of ecologic zones The survey population was chosen in two stages, designed to cover all ecologic zones of the country, and to represent all 53 provinces of Vietnam as defined in 1995 (subsequent changes resulted in the current administrative structure of 65 provinces). Seven geographic zones were defined, grouping provinces by ecologic similarities, such as mountains, river basins and coastal areas (Fig 1). The Northern Mountain region (zone 1) is a large land area, with green hills and barren stony mountains, populated in isolated hamlets with limited transportation, communication and irrigation systems. The Red River Delta (zone 2), which includes the national capital Hanoi, has a high population density and intensive rice farming, making it the Fig 1–Map of Vietnam with ecological regions. Zone 1 North Mountain Zone 2 Red River Delta Zone 3 Central Coast (North) Zone 4 Central Coast (South) Zone 5 Central Highland Zone 6 Northeast South region Zone 7 Mekong River Delta INTESTINAL HELMINTHIASIS AMONG REPRODUCTIVE AGE WOMEN IN VIETNAM Vol 37 No. 5 September 2006 867 second largest rice-producing zone. The Northern Central Coastal region (zone 3) is a narrow strip of coastal land bounded by mountains in the west. Industrial crops, such as peanuts, coffee and rubber, are grown here. The Southern Central Coastal region (zone 4) is characterized by a prolonged dry season, and suffers from shortages of both food and labor. The Central Highland (zone 5) is known for the cultivation of coffee, rubber and other industrial crops. The dry season is prolonged and lack of water is a major constraint in this zone. The Northeast of South region (zone 6), including Ho Chi Minh city (formerly Saigon), is a relatively urbanized zone that benefits from ready access to markets. The Mekong River Delta (zone 7) is the most important rice growing area in the country. Each ecological zone was regarded as a survey zone to avoid the problem of missing large areas with low population density and to allow accurate estimates of parameters by zone. In the first stage of selection, data from the 1990 Vietnamese National survey was used to create zonal lists of communes and the number of households in each commune. For each zone, 20 communes (clusters) were selected using population proportional to size sampling, with a sampling size equal to 1/20 of the total number of households. In the second stage, a systematic random sample of 60 households per commune was selected from an existing list of all children <5 years old. In each household, the youngest child and his or her mother and father were included in the survey.