Environmental and structural factors associated with bacterial diversity in household dust across the Arizona-Sonora border.

We previously reported that asthma prevalence was higher in the United States (US) compared to Mexico (MX) (25.8% vs. 8.4%). This investigation assessed differences in microbial dust composition in relation to demographic and housing characteristics on both sides of the US-MX Border. Forty homes were recruited in the US and MX. Home visits collected floor dust and documented occupants' demographics, asthma prevalence, housing structure, and use characteristics. US households were more likely to have inhabitants who reported asthma when compared with MX households (30% vs. 5%) and had significantly different flooring types. The percentage of households on paved roads, with flushing toilets, with piped water and with air conditioning was higher in the US, while dust load was higher in MX. Significant differences exist between countries in the microbial composition of the floor dust. Dust from Mexican homes was enriched with Alishewanella, Paracoccus, Rheinheimera genera and Intrasporangiaceae family. A predictive metagenomics analysis identified 68 significantly differentially abundant functional pathways between US and MX. This study documented multiple structural, environmental, and demographic differences between homes in the US and MX that may contribute to significantly different microbial composition of dust observed in these two countries.

Aedes aegypti (Diptera: Culicidae) Longevity and Differential Emergence of Dengue Fever in Two Cities in Sonora, Mexico.

Dengue virus, primarily transmitted by the Aedes aegypti (L.) mosquito, has rapidly expanded in geographic extent over the past several decades. In some areas, however, dengue fever has not emerged despite established Ae. aegypti populations. The reasons for this are unclear and have sometimes been attributed to socio-economic differences. In 2013 we compared Ae. aegypti adult density and population age structure between two cities in Sonora, Mexico: Hermosillo, which has regular seasonal dengue virus transmission, and Nogales, which has minimal transmission. Larval and pupal abundance was greater in Nogales, and adult density was only higher in Hermosillo during September. Population age structure, however, was consistently older in Hermosillo. This difference in longevity may have been one factor that limited dengue virus transmission in Nogales in 2013, as a smaller proportion of Ae. aegypti females survived past the extrinsic incubation period.

Prevalence of Asthma in School Children on the Arizona-Sonora Border.

BACKGROUND: Mexican-born children living in the United States have a lower prevalence of asthma than other US children. Although children of Mexican descent near the Arizona (AZ)-Sonora border are genetically similar, differences in environmental exposures might result in differences in asthma prevalence across this region. OBJECTIVE: The objective of this study was to determine if the prevalence of asthma and wheeze in these children varies across the AZ-Sonora border. METHODS: The International Study of Asthma and Allergy in Children written and video questionnaires were administered to 1753 adolescents from 5 middle schools: Tucson (school A), Nogales, AZ (schools B, C), and Nogales, Sonora, Mexico (schools D, E). The prevalence of asthma and symptoms was compared, with analyses in the AZ schools limited to self-identified Mexican American students. RESULTS: Compared with the Sonoran reference school E, the adjusted odds ratio (OR) for asthma was significantly higher in US schools A (OR 4.89, 95% confidence interval [CI] 2.72-8.80), B (OR 3.47, 95% CI 1.88-6.42), and C (OR 4.12, 95% CI 1.78-9.60). The adjusted OR for wheeze in the past year was significantly higher in schools A (OR 2.19, 95% CI 1.20-4.01) and B (OR 2.67, 95% CI 1.42-5.01) on the written questionnaire and significantly higher in A (OR 2.13, 95% CI 1.22-3.75), B (OR 1.95, 95% CI 1.07-3.53), and Sonoran school D (OR 2.34, 95% CI 1.28-4.30) on the video questionnaire compared with school E. CONCLUSIONS: Asthma and wheeze prevalence differed significantly between schools and was higher in the United States. Environmental factors that may account for these differences could provide insight into mechanisms of protection from asthma.

Microclimate and human factors in the divergent ecology of Aedes aegypti along the Arizona, U.S./Sonora, MX border.

This study examined the association of human and environmental factors with the presence of Aedes aegypti, the vector for dengue fever and yellow fever viruses, in a desert region in the southwest United States and northwest Mexico. Sixty-eight sites were longitudinally surveyed along the United States-Mexico border in Tucson, AZ, Nogales, AZ, and Nogales, Sonora during a 3-year period. Aedes aegypti presence or absence at each site was measured three times per year using standard oviposition traps. Maximum and minimum temperature and relative humidity were measured hourly at each site. Field inventories were conducted to measure human housing factors potentially affecting mosquito presence, such as the use of air-conditioning and evaporative coolers, outdoor vegetation cover, and access to piped water. The results showed that Ae. aegypti presence was highly variable across space and time. Aedes aegypti presence was positively associated with highly vegetated areas. Other significant variables included microclimatic differences and access to piped water. This study demonstrates the importance of microclimate and human factors in predicting Ae. aegypti distribution in an arid environment.