No abstract

Immunization evaluation surveys have shown a wide variation across regions, states and different strata of the society.

Background Up to 60% of US visitors to Mexico develop travelers’ diarrhea (TD). In Mexico, rates of diarrhea have been associated with the rainy season and increase in ambient temperature. However, the seasonality of the various diarrheagenic Escherichia coli pathotypes in travelers has not been well described. Objective To determinate if ambient temperature and rainfall have an impact on the acquisition of TD due to different diarrheagenic E. coli pathotypes in Mexico. Methods We conducted a cohort study of US adult students traveling to Cuernavaca, Mexico that were followed during their stay and provided a stool sample with the onset of TD. The presence of E. coli was analyzed by a direct fecal multiplex PCR for common E. coli pathotypes including enterotoxigenic, enteropathogenic, enteroinvasive, shigatoxin producing and enteroaggregative E. coli (ETEC, EPEC, EIEC, STEC and EAEC respectively). The presence of pathotypes was correlated with daily rainfall, average, maximum and minimum temperatures. Results 515 adults were enrolled from January 2006 to February 2007. The weekly attack rate of TD for newly arrived travelers was lower in the winter months (range 6.8 to 16.3%) than in summer months (range 11.5–25%; p=0.05). The rate of ETEC infection increased by 7% for each degree centigrade increase in weekly ambient temperature (P=0.003). In contrast, EPEC and EAEC were identified in similar proportions during the winter and summer seasons. Conclusions Temperature variations in Central Mexico influenced the rate of ETEC but not EAEC associated diarrhea in US visitors. This epidemiological finding could influence seasonal recommendations for the use of ETEC vaccines in Mexico.

The T/T genotype in position codon 632 of the lactoferrin gene is associated with susceptibility to diarrhea in North Americans traveling to Mexico.