Biology and Epidemiology of Dengue Viruses in the El Paso and the Surrounding USA and Mexico Border Communities
Dengue is considered one of the most important human arboviral diseases worldwide. Dengue cases have increased in the last three decades in the Americas, especially along the United States (US)- Mexico (MX) border region, where the main vector of dengue, Aedes aegypti mosquito, is widely distributed. Explosive outbreaks of dengue in northern Mexico have been associated with imported and local transmission of dengue in the US border communities, especially in the Southeast Texas area, also known as Rio Grande Valley. Due to the unknown if dengue virus (DENV) is present in other areas in the US border located west of the Rio Grande Valley, the main aim of this dissertation is to understand the biology and epidemiology of dengue virus in El Paso and surrounding US and MX border communities. The first aim was to determine if dengue is endemic in El Paso, Texas and Ciudad Juarez, Mexico border communities based on the serological evidence of DENV. A serosurvey for DENV antibodies among a cohort of humans in Anapra, Ciudad Juarez and pregnant women in El Paso, Texas was conducted between 2015 and 2016. Overall, 14.1% (11/78) and 8.3% (4/48) of past and recent DENV infection, respectively were detected in Ciudad Juarez. DENV serotype 1 neutralizing antibody was mainly detected in the seroconverted individuals which also did not have a travel history outside Ciudad Juarez, suggesting locally acquired dengue infection. By contrast, the past evidence of DENV in El Paso, Texas was 0.74% (11/1472), suggesting no autochthonous dengue transmission occurred in El Paso, Texas unlike other seroprevalence rates reported in dengue-endemic areas. The second aim was to evaluate the vector competence of Ae. aegypti mosquitoes from the US border region (El Paso and Rio Grande) to dengue and the effect of viral dose and temperature. El Paso and Rio Grande Ae. aegypti mosquitoes displayed a varied infectivity rate according to the dengue viral strain, ranging from 60% to 100% for DENV-2 (FSB 3381) and DENV-2 (328298) strains, while the infectivity rate was significantly low (4% to 13%) for DENV-2 (16681) strain. Disseminated infection rates of DENV-2 (FSB 3381) and DENV-2 (328298) in El Paso and Rio Grande Ae. aegypti mosquitoes significantly increased through the incubation period and reached the highest rate (80% to 100%) at 14 days of incubation. A low transmission rate of DENV-2 (FSB 3381) and DENV-2 (328298) ranging from 2% to 3% was observed in El Paso and Rio Grande Ae. aegypti mosquitos’ saliva. Furthermore, a lower dengue viral exposure dose (FSB 3381 and 328298) significantly decreased the infectivity rates in El Paso and Rio Grande Ae. aegypti mosquitoes and delayed the viral dissemination. Elevated temperatures (28°C and 32°C) increased the infectivity and viral replication of DENV-2 (FSB 3381) in El Paso and Rio Grande Ae. aegypti mosquito body, while disseminated infection rates differed between Rio Grande (16.6%) and El Paso (64%) mosquitoes at low temperatures (24°C). Finally, the third aim was to isolate and characterize a dengue virus from the Mexican/US border and evaluate its effects on the vector competence on the US border Ae. aegypti mosquitoes. A DENV-1 genotype V was isolated from a febrile patient displaying a viremia of 2.69 log 10 PFU/mL in Ciudad Juarez in 2015. Five amino acid changes in the DENV-1 isolate were unique in comparison to other Mexican DENV isolates. No travel history was reported in the patient before the onset of illness, suggesting locally acquired dengue infection in Ciudad Juarez. Infectivity rates in El Paso and Rio Grande Ae. aegypti mosquitoes to DENV-1 isolate were significantly associated with the viral ingested dose. Furthermore, El Paso mosquitoes were more susceptible (dose to infect 50% mosquitoes [MID50] < 4 log 10 PFU/mL) to DENV-1 isolate than Rio Grande mosquitoes (MID50= 5.23 log 10 PFU/mL). A 4 log 10 PFU/ml exposure dose of DENV-1 isolate was able to completely disseminate in the infected bodies of El Paso and Rio Grande mosquitoes at 14 days of incubation. The transmission rate of DENV-1 isolate in El Paso and Rio Grande Ae. aegypti mosquitoes ranged from 3.23% to 5.71%. The variation in the vector competence observed in this study can be linked to genetic interactions between the viral strain and the Ae. aegypti strain (gene by gene interactions) and potential salivary gland barriers in Ae. aegypti from the US border region. Overall, this is the first study that described the epidemiology of dengue in El Paso and Ciudad Juarez border communities and the interaction between Ae. aegypti from the US border and DENV and contributed to its understanding in the US border region.
Infante, Pedro Miguel Palermo, "Biology and Epidemiology of Dengue Viruses in the El Paso and the Surrounding USA and Mexico Border Communities" (2022). ETD Collection for University of Texas, El Paso. AAI29998812.