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Original Papers
Gastroenteritis and foodborne illness
INTRODUCTION
Group A rotavirus is the most common cause of viral gastroenteritis in young children and animals worldwide [1-3]. The virus particle has an 11-segment double-stranded RNA genome encoding six structural viral proteins (VP1-4, VP6, VP7) and six non-structural proteins (NSP 1-5/6) [4]. The two outer capsid proteins, VP4 and VP7 are used to classify rotavirus strains into P (protease-sensitive) and G (glycoprotein) serotypes, respectively, based on neutralization determinants located on the surface of VP4 and VP7 [5, 6]. To date, 37 P types and 27 G types have been reported, of these, 15 P types and 12 G types have been identified in humans and animals [7, 8].
There have been persistent efforts made towards the development of effective rotavirus vaccines. However, success of rotavirus immunization mostly depends on incorporation of prevalent genotype(s) in the vaccine. Several researchers have reported that G1-G4 are the predominant genotypes circulating globally [9-11]. The two rotavirus vaccines, a live human monovalent strain and a polyvalent human-bovine reassortant strain [12, 13] include only the predominant four G types. However, circulation of unusual rotavirus strains have been reported repeatedly in different parts of the world, e.g. the prevalence of [P6]G9 strains in India [14], [P6]G8 strains in Malawi [15], and [P8]G5 strains in Brazil [16]. Moreover, lack of host restriction in rotaviruses facilitates the emergence of reassortant strains [17]. There have been several reports regarding human rotavirus genotypes commonly found in animals [18, 19]. In India, the northeastern (NE) states is an agrarian region where animal rearing is an essential part of farming. This provides ample opportunity for humans and animals to share a common habitat. Such conditions generate the scope for rotavirus co-circulation during mixed infections in young children and animals with diarrhoea. Moreover, in some settings, close contact of humans with farm animals could generate an opportunity for inter-species transmission and gene reassortment [20, 21]. Genetic diversity between individual rotavirus genotypes is now suspected to be more extensive than previously anticipated. This may potentially alter the immune response to vaccination. Several studies have evidenced the predominance of subtypes or genetic lineages of an individual genotype. Jin et al. [22] identified four distinct lineages of G1...