Human rotavirus strains circulating in Venezuela after vaccine introduction: predominance of G2P[4] and reemergence of G1P[8].

BACKGROUND: Rotavirus (RV) is the most common cause of severe childhood diarrhea worldwide. Despite Venezuela was among the first developing countries to introduce RV vaccines into their national immunization schedules, RV is still contributing to the burden of diarrhea. Concerns exist about the selective pressure that RV vaccines could exert on the predominant types and/or emergence of new strains. RESULTS: To assess the impact of RV vaccines on the genotype distribution 1 year after the vaccination was implemented, a total of 912 fecal specimens, collected from children with acute gastroenteritis in Caracas from February 2007 to April 2008, were screened, of which 169 (18.5%) were confirmed to be RV positive by PAGE. Rotavirus-associated diarrhea occurred all year-round, although prevailed during the coolest and driest months among unvaccinated children under 24 months old. Of 165 RV strains genotyped for G (VP7) and P (VP4) by seminested multiplex RT-PCR, 77 (46.7%) were G2P[4] and 63 (38.2%) G1P[8]. G9P[8], G3P[8] and G2P[6] were found in a lower proportion (7.3%). Remarkable was also the detection of <5% of uncommon combinations (G8P[14], G8P[4], G1P[4] and G4P[4]) and 3.6% of mixed infections. A changing pattern of G/P-type distribution was observed during the season studied, with complete predominance of G2P[4] from February to June 2007 followed by its gradual decline and the reemergence of G1P[8], predominant since January 2008. Phylogenetic analysis of VP7 and VP4 genes revealed a high similarity among G2P[4] and global strains belonging to G2-II and P[4]-V lineages. The amino acid substitution 96D → N, related with reemergence of the G2 genotype elsewhere, was observed. The G1P[8] strains from Caracas were grouped into the lineages G1-I and P[8]-III, along with geographically remote G1P[8] rotaviruses, but they were rather distant from Rotarix® vaccine and pre-vaccine strains. Unique amino acid substitutions observed on neutralization domains of the VP7 sequence from Venezuelan post-vaccine G1P[8] could have conditioned their re-emergence and a more efficient dissemination into susceptible population. CONCLUSIONS: The results suggest that natural fluctuations of genotypes in combination with forces driving the genetic evolution could determine the spread of novel strains, whose long-term effect on the efficacy of available vaccines should be determined.

Genotyping of human rotaviruses circulating among children with diarrhea in Valencia, Venezuela.

Rotavirus infection is the most common cause of severe gastroenteritis during childhood worldwide, especially in developing countries. Two rotavirus vaccines are available for childhood immunization programs. Evaluation of the vaccine performance will benefit from knowledge of the epidemiological features of rotavirus infection in regional settings. Limited information on the molecular characteristics of the rotavirus types circulating in Venezuela is available. Eighty seven (89.7%) of the 97 ELISA rotavirus positive stool samples collected from children with diarrhea aged <5 years during 2003 in Valencia (Carabobo State), were G-, P- and NSP4-genotyped by RT-PCR and/or automated sequencing. Four common combinations, G3P[8]/NSP4-E1, G2P[4]/NSP4-E2, G9P[8]/NSP4-E1, and G1P[8]/NSP4-E1 were responsible for 50.6%, 35.6%, 5.7%, and 1.1%, respectively of cases of rotavirus diarrhea, most of them (66%) in children ≤12 months. One uncommon G8P[14]/NSP4-E2 strain was also detected. Temporal fluctuation of genotype distribution occurred, but no differences by age, diarrhea severity score, sex, treatment type or patient medical attention were observed, except for the G3P[8]/NSP4-E1, associated with a more severe dehydration than any other type (P < 0.01). The results confirm the broad diversity among rotavirus strains circulating in Venezuela prior to vaccine implementation, showing the predominance of G3, significant proportion of G2 and moderate circulation of G9 strains. Epidemiological surveillance is needed to detect the emergence of new genotypes that could escape protection induced by vaccination.

Precisión de la refracción objetiva por wavefront comparada con la refracción subjetiva tomada como prueba de oro / Precission of objective refraction by wavefront compared to subjective refraction taken as a test of gold

Introducción: la refracción subjetiva es utilizada como prueba de oro; incorpora la participación neurosensorial del paciente para definir la mejor visión corregida. Métodos: este trabajo tiene como objetivo analizar las diferencias por medio de vectores y análisis estadístico de los datos que resultaron de comparar la refracción subjetiva frente a la refracción objetiva, medida por los mapas de aberración por wavefront (longitud de onda). Resultados: se evaluaron 156 ojos con refracción subjetiva y refracción objetiva ORK (wavefront Schwind: instrumento que analiza todas las aberraciones ópticas que llegan al ojo), y las diferencias que se encontraron en miopes, hipermétropes, astigmatismos hipermetrópicos y astigmatismos miópicos, fueron menores de 0.50 dioptrías (70 porciento) con una variación en los ejes hasta en 25 grados. Conclusión: se encontraron diferencias promedio significativas entre la refracción subjetiva tomada como prueba de oro y el Coas (unidad de medida objetiva guiada por longitudes de onda) definido como refracción objetiva. A pesar de encontrar diferencias menores de 0.50 dioptrías, es de gran importancia clínica al momento de realizar una adaptación de gafas, lentes de contacto y/o programación para cirugía refractiva.