Feline Origin of Rotavirus Strain, Tunisia, 2008

Mouna Ben Hadj Fredj, Elisabeth Heylen, Mark Zeller, Imene Fodha, Meriam Benhamida-Rebai, Marc Van Ranst, Jelle Matthijnssens, and Abdelhalim Trabelsi

Author affiliations: Sahloul University Hospital, Sousse, Tunisia (M. Ben Hadj Fredj, I. Fodha, M. Benhamida-Rebai, A. Trabelsi); University of Monastir, Monastir, Tunisia (M. Ben Hadj Fredj, I. Fodha, M. Benhamida-Rebai, A. Trabelsi); University of Leuven, Leuven, Belgium (E. Heylen, M. Zeller, M. Van Ranst, J. Matthijnssens)

Abstract

In Tunisia in 2008, an unusual G6P[9] rotavirus, RVA/human-wt/TUN/17237/2008/G6P[9], rarely found in humans, was detected in a child. To determine the origin of this strain, we conducted phylogenetic analyses and found a unique genotype constellation resembling rotaviruses belonging to the feline BA222-like genotype constellation. The strain probably resulted from direct cat-to-human transmission.

Group A rotaviruses (RVAs) are a leading cause of severe acute gastroenteritis in infants and young children. An infectious RVA virion is a triple-layered icosahedral particle that contains 11 segments of double-stranded RNA (1). The outer protein layer is formed by virus capsid protein (VP) 4 (P antigen) and VP7 (G antigen), each of which is used for binomial nomenclature (1). At least 27 G genotypes and 35 P genotypes have been identified (2). Globally, only 6 G/P-genotype combinations are of epidemiologic relevance to humans: G1P[8], G3P[8], G4P[8], G9P[8], and G12P[8], which are typically found in combination with a Wa-like genotype constellation (I1-R1-C1-M1-A1-N1-T1-E1-H1), and G2P[4], which is found in combination with a DS-1-like genotype constellation (I2-R2-C2-M2-A2-N2-T2-E2-H2) (3).
Certain G genotypes rarely encountered in humans are commonly associated with RVA strains from animals (4). For example, G6 RVA strains are occasionally detected in humans but are a common genotype in cattle (4). Complete genomes have been determined for 11 human G6 RVA strains: 7 G6P[14], 2 G6P[9], 1 human–animal reassortant G6P[6], and 1 unique G6P[11] (5–9).
The P[9] genotype is commonly associated with the G3 or G6 genotype and is believed to be typical for feline and canine RVA strains (4). A few G3P[9] and G3P[3] RVA strains have been detected in humans, and they are believed to be the result of direct interspecies transmission from cats or dogs to humans, possibly in combination with reassortment (10–13).
Previously, 2 genotype constellations among feline and canine RVA strains, cat97-like and AU-1-like, were described (13). The genotype constellations were G3-P[3]-I3-R3-C2-M3-A9-N2-T3-E3-H6 and G3-P[9]-I3-R3-C3-M3-A3-N3-T3-E3-H3, respectively. Recently, the complete genomes of a feline strain (RVA/cat-wt/ITA/BA222/2005/G3P[9]) and 2 feline-like human RVA strains (RVA/human-wt/ITA/PAI58/1996/G3P[9] and RVA/human-wt/ITA/PAH136/1996/G3P[9]) were shown to possess a distinct genotype constellation, G3-P[9]-I2-R2-C2-M2-A3-N1/N2-T3/T6-E2-H3 (11), representing a tentative third feline genotype constellation (BA222-like). This tentative third feline BA222-like genotype constellation is an intriguing genotype mosaic, sometimes possessing Wa-like nonstructural protein (NSP) 2 or NSP3 gene segments and partially resembling the genotype constellation found in RVA strains from cattle and other artiodactyla (5,7,10,11). Full-genome sequences of unusual human RVA strains are being analyzed to detect interspecies transmission, reassortment, and evolutionary relationships between human and animal RVAs (10,11).
In 2008, during continuous surveillance for human RVA in Tunisia, we identified an unusual G6P[9] strain in an 8-month-old hospitalized child (14). To understand the evolution and origin of this unusual strain, RVA/human-wt/TUN/17237/2008/G6P[9] (hereafter referred to as strain 17237), we conducted phylogenetic analyses.