Date Published: December 1, 2014
Publisher: Public Library of Science
Author(s): Riza Durmaz, Atila Taner Kalaycioglu, Sumeyra Acar, Zekiye Bakkaloglu, Alper Karagoz, Gulay Korukluoglu, Mustafa Ertek, Mehmet Ali Torunoglu, Yury E. Khudyakov.
Group A rotaviruses are the most common causative agent of acute gastroenteritis among children less than 5 years of age throughout the world. This sentinel surveillance study was aimed to obtain baseline data on the rotavirus G and P genotypes across Turkey before the introduction of a universal rotavirus vaccination program.
Rotavirus antigen-positive samples were collected from 2102 children less than 5 years of age who attended hospitals participating in the Turkish Rotavirus Surveillance Network. Rotavirus antigen was detected in the laboratories of participating hospitals by commercial serological tests such as latex agglutination, immunochromatographic test or enzyme immunoassay. Rotavirus G and P genotypes were determined by reverse transcription polymerase chain reaction (RT-PCR) using consensus primers detecting the VP7 and VP4 genes, followed by semi-nested type-specific multiplex PCR.
RT-PCR found rotavirus RNA in 1644 (78.2%) of the samples tested. The highest rate of rotavirus positivity (38.7%) was observed among children in the 13 to 24 month age group, followed by children in the age group of 25 to 36 months (28.3%). A total of eight different G types, six different P types, and 42 different G–P combinations were obtained. Four common G types (G1, G2, G3, and G9) and two common P types (P and P) accounted for 95.1% and 98.8% of the strains, respectively. G9P was the most common G/P combination found in 40.5% of the strains followed by G1P (21.6%), G2P (9.3%), G2P (6.5%), G3P (3.5%), and finally, G4P (3.4%). These six common genotypes included 83.7% of the strains tested in this study. The rate of uncommon genotypes was 14%.
The majority of the strains analyzed belonged to the G1–G4 and G9 genotypes, suggesting high coverage of current rotavirus vaccines. This study also demonstrates a dramatic increase in G9 genotype across the country.
Rotaviruses are the most important causative agents of severe gastroenteritis in infants and young children worldwide and are responsible for 453,000 deaths in 2008 . More than one-third of deaths attributable to diarrhea and 5% of all deaths in children less than 5 years of age are due to rotavirus infections . They are responsible for 25% to 50% of all hospitalizations for diarrhea in children in both developed and developing countries . Although mortality as a result of rotavirus infection is low in countries with good health care facilities, an 85% mortality rate has been reported in South Asia and sub-Saharan Africa .
The epidemiology of rotavirus-associated diseases shows variation based on the socio-economic condition of the study population and the climate of the different countries (2, 16, 28). Although rotavirus infections can be recorded throughout the year in Turkey, the majority of rotavirus infections are observed from September to May –, , . In parallel to these data, we collected stool samples from infected children throughout the year and the majority of the samples (94.4%) were obtained from September to the end of May. According to previous studies in Turkey, most rotavirus infections were recorded in children aged 12 to 23 months, and a second peak was observed in the 6 to 11 month age group; more than 70% of rotavirus infections occurred in children less than 2 years of age , , . These data agree with results reported from many European countries , –. Our study, conducted on high numbers of children from seven geographic regions, showed that rotavirus mainly infected children from 13 to 24 months of age followed by the 25 to 36 month age group. This current study, which provided the most comprehensive and up-to-date data, indicates that rotavirus infections in Turkey are mainly observed in children aged 13 to 36 months, who might be more prone to acquire rotavirus infection in Turkey. Therefore, further surveillance studies in Turkey should include children less than 5 years old, instead of less than 2 years old.
This sentinel surveillance study carried out in 23 provinces in Turkey from August 2012 to July 2014 provides the most comprehensive and up-to-date information on rotavirus strains circulating in Turkey before the introduction of a rotavirus vaccine program. This report revealed that i) rotavirus infections mainly affect children from 13 to 24 months of age; ii) the number of different G and P genotypes was limited, whereas a very high number (42) of different G–P combinations were observed; iii) a remarkable rate of rotavirus strains were classified in uncommon and/or mixed genotypes; iv) despite heterogeneity among the genotypes observed in our study population, the G1, G2, G3, G4, and G9 genotypes included more than 97% of the rotavirus strains circulating in Turkey; v) available rotavirus vaccines have high coverage rates of rotavirus strains currently circulating in Turkey. This background information can be used to monitor the impact of rotavirus vaccines on future strain prevalence.