To our knowledge, this is the first study describing the prevalence of infections in a representative sample of the largest urban metropolitan area of the U.S.-Mexico border. We found that H. pylori
infection is highly prevalent in this population, at levels comparable with those reported among the Mexico-born U.S. population.13
However, the prevalence of Taenia
spp. among U.S. immigrants from Mexico underscores the -appropriateness of a call for action on the emerging nature of neurocysticercosis in the U.S.14
Moreover, our study further characterizes that Mexican Americans (and particularly immigrants from Mexico, who largely populate the U.S.-Mexico border) tend to be a high-risk group for infection with H. pylori
Our previous study2
evaluating the use of urine-diverting latrines in Ciudad Juarez had found Giardia
in 82.0% and 70.0% of the samples, respectively, while the present study found them at 2.7% and 1.9%, respectively. However, in the earlier study2
the samples of biosolid waste were obtained from the urine-diverting toilets rather than from identifiable individuals in a representative population-based sample.
Our findings on the prevalence of intestinal parasites are very different from those reported in children in U.S. areas along the border with Mexico.15–18
The differences could be real or could reflect differences in the populations studied (facility-based vs. population-based) and in the sampling methodologies and organisms ascertained. It can be argued that the sustained development of the infrastructure in water supply and sanitation associated with the economic boom of the maquiladora
industry in Ciudad Juarez could be responsible for the low prevalence of infections. In addition, the region is in the middle of the large Chihuahuan Desert, and the dry, sandy soil provides an adverse environment for the survival of geo-helminths.
The findings on the prevalence of Giardia
spp. (4%) and Cryptosporidium
spp. (1% to 3%) are consistent with the reported frequency of infection with these parasites in the U.S. On the other hand, we found that 38% of the study population was infected with H. pylori
, which was the most prevalent infection of the GI tract in this population. The status of H. pylori
infection does not mean that the individual has precancer lesions; however, it seems from volunteer studies that most infected people develop a so-called H. pylori
gastritis with intense polymorphonuclear cell infiltration and interleukin-8 induction in gastric mucosa even in the absence of infections with cagA gene strains.19
Given that infections with most of the pathogens studied—such as Cryptosporidium
—typically last no more than three months while the duration of H. pylori
infections tends to be lifelong, we cannot draw conclusions as to the incidence of infection with each pathogen.
When comparing infection prevalence on either side of the border, our study findings suggested that the prevalence of Taenia
spp. was significantly higher on the U.S. side of this study population, probably due to the use of mass deworming campaigns among schoolchildren in Mexico that have proved successful.19
This intervention, as well as the dry and urban setting that ensures safe drinking water and sanitation to almost 100% of the population, could also explain the relatively low prevalence of helminths.
Some of the limitations of our study are worth discussing, including the relatively low response of 51% submission of fecal samples. However, it should be noted that we obtained the consent and interview from the household head, whereas other members of the household may have been less inclined to participate. Surveys using only interviews on average obtain response rates of 70% to 85%;20
one study of migrant farm workers obtained a 50% response rate for fecal specimens.21
Second, the study lacked the statistical power to detect increased PRs >3.5 for Cryptosporidium spp., Giardia spp., E. dispar, A. lumbricoides, N. americanus, and Cyclospora spp. We failed to find an association between the prevalence of H. pylori infection and the occurrence of domestic fecal contamination, which could be due to limited microbiological sampling. It is also possible that participants disinfected their kitchens in anticipation of the visits.
We did not collect specific data on individuals who live/work in both cities (i.e., commute or have family members on the other side of the border). Border crossing in 2004 between these two cities was extensive, according to our data:3
52% of residents in Ciudad Juarez and and 48% of residents in El Paso crossed the border at least once a month. One-third of residents of Ciudad Juarez reported never crossing to El Paso, and almost one-fifth of residents of El Paso said they never visited Ciudad Juarez. Our study did not find any association between these patterns and the prevalence of any of the infections examined (data not shown).
Handwashing was associated with the prevalence of fecal coliforms on the hands of meal preparers in the study population,4
giving support to the importance of within-household H. pylori
transmission via the fecal-oral route. Other cross-sectional studies have documented such evidence of self-reported hygienic behaviors and prevalence of H. pylori
which is consistent with transmission—at least most times—through the oral-fecal route. The protective effect of handwashing on the prevalence of H. pylori
infection in this population is noteworthy, as a large binational health education campaign has been in place, the “Handwashing Viva Las Manos” campaign, which received more than $3.2 million from the Paso del Norte Health Foundation. Our data suggest that these types of programs need continuing support, as almost one-sixth of the population reported that they do not always wash hands after using the toilet.