Survey of equine rotaviruses shows conservation of one P genotype in background of two G genotypes

Equine Rotavirus A under the One Health Lens: Potential Impacts on Public Health

Group A rotaviruses are a well-known cause of viral gastroenteritis in infants and children, as well as in many mammalian species and birds, affecting them at a young age. This group of viruses has a double-stranded, segmented RNA genome with high genetic diversity linked to point mutations, recombination, and, importantly, reassortment. While initial molecular investigations undertaken in the 1900s suggested host range restriction among group A rotaviruses based on the fact that different gene segments were distributed among different animal species, recent molecular surveillance and genome constellation genotyping studies conducted by the Rotavirus Classification Working Group (RCWG) have shown that animal rotaviruses serve as a source of diversification of human rotavirus A, highlighting their zoonotic potential. Rotaviruses occurring in various animal species have been linked with contributing genetic material to human rotaviruses, including horses, with the most recent identification of equine-like G3 rotavirus A infecting children. The goal of this article is to review relevant information related to rotavirus structure/genomic organization, epidemiology (with a focus on human and equine rotavirus A), evolution, inter-species transmission, and the potential zoonotic role of equine and other animal rotaviruses. Diagnostics, surveillance and the current status of human and livestock vaccines against RVA are also reviewed.

Zoonotic RVA: State of the Art and Distribution in the Animal World

Rotavirus species A (RVA) is a pathogen mainly affecting children under five years old and young animals. The infection produces acute diarrhea in its hosts and, in intensively reared livestock animals, can cause severe economic losses. In this study, we analyzed all RVA genomic constellations described in animal hosts. This review included animal RVA strains in humans. We compiled detection methods, hosts, genotypes and complete genomes. RVA was described in 86 animal species, with 52% (45/86) described by serology, microscopy or the hybridization method; however, strain sequences were not described. All of these reports were carried out between 1980 and 1990. In 48% (41/86) of them, 9251 strain sequences were reported, with 28% being porcine, 27% bovine, 12% equine and 33% from several other animal species. Genomic constellations were performed in 80% (32/40) of hosts. Typical constellation patterns were observed in groups such as birds, domestic animals and artiodactyls. The analysis of the constellations showed RVA's capacity to infect a broad range of species, because there are RVA genotypes (even entire constellations) from animal species which were described in other studies. This suggests that this virus could generate highly virulent variants through gene reassortments and that these strains could be transmitted to humans as a zoonotic disease, making future surveillance necessary for the prevention of future outbreaks.

Complete Genome Sequencing Reveals Unusual Equine Rotavirus A of Bat Origin from India

Rotaviruses are the most common viral agents associated with foal diarrhea. Between 2014 and 2017, the annual prevalence of rotavirus in diarrheic foals ranged between 18 and 28% in Haryana (India). Whole-genome sequencing of two equine rotavirus A (ERVA) isolates (RVA/Horse-wt/IND/ERV4/2017 and RVA/Horse-wt/IND/ERV6/2017) was carried out to determine the genotypic constellations (GCs) of ERVAs. The GCs of both the isolates were G3-P[3]-I8-R3-C3-M3-A9-N3-T3-E3-H6, a unique combination reported for ERVAs so far. Both the isolates carried VP6 of genotype I8, previously unreported from equines. Upon comparison with RVAs of other species, the GC of both isolates was identical to that of a bat rotavirus strain, MSLH14, isolated from China in 2012. The nucleotide sequences of the genes encoding VP3, NSP2, and NSP3 shared >95.81% identity with bat RVA strains isolated from Africa (Gabon). The genes encoding VP1, VP2, VP7, NSP1, and NSP4 shared 94.82% to 97.12% nucleotide identities with the human strains which have zoonotic links to bats (RCH272 and MS2015-1-0001). The VP6 genes of both strains were distinct and had the highest similarity of only 87.08% with that of CMH222, a human strain of bat origin. The phylogenetic analysis and lineage studies revealed that VP7 of both isolates clustered in a new lineage (lineage X) of the G3 genotype with bat, human, and alpaca strains. Similarly, VP4 clustered in a distinct P[3] lineage. These unusual findings highlight the terra incognita of the genomic diversity of equine rotaviruses and support the need for the surveillance of RVAs in animals and humans with a "one health" approach. IMPORTANCE Rotaviruses are globally prevalent diarrheal pathogens in young animals including foals, piglets, calves, goats, sheep, cats, and dogs along with humans. The genome of rotaviruses consists of 11 segments, which enables them to undergo reshuffling by reassortment of segments from multiple species during mixed infections. In this study, the prevalence of equine rotaviruses was 32.11% in organized equine farms of North India. The complete genome analysis of two ERVA isolates revealed an unusual genomic constellation, which was previously reported only in a bat RVA strain. A segment-wise phylogenetic analysis revealed that most segments of both isolates were highly similar either to bat or to bat-like human rotaviruses. The occurrence of unusual bat-like rotaviruses in equines emphasizes the need of extensive surveillance of complete genomes of both animal and human rotaviruses with a "one health" approach.

Identification of a Ruminant Origin Group B Rotavirus Associated with Diarrhea Outbreaks in Foals

Equine rotavirus group A (ERVA) is one of the most common causes of foal diarrhea. Starting in February 2021, there was an increase in the frequency of severe watery to hemorrhagic diarrhea cases in neonatal foals in Central Kentucky. Diagnostic investigation of fecal samples failed to detect evidence of diarrhea-causing pathogens including ERVA. Based on Illumina-based metagenomic sequencing, we identified a novel equine rotavirus group B (ERVB) in fecal specimens from the affected foals in the absence of any other known enteric pathogens. Interestingly, the protein sequence of all 11 segments had greater than 96% identity with group B rotaviruses previously found in ruminants. Furthermore, phylogenetic analysis demonstrated clustering of the ERVB with group B rotaviruses of caprine and bovine strains from the USA. Subsequent analysis of 33 foal diarrheic samples by RT-qPCR identified 23 rotavirus B-positive cases (69.69%). These observations suggest that the ERVB originated from ruminants and was associated with outbreaks of neonatal foal diarrhea in the 2021 foaling season in Kentucky. Emergence of the ruminant-like group B rotavirus in foals clearly warrants further investigation due to the significant impact of the disease in neonatal foals and its economic impact on the equine industry.

Equine rotavirus infection

This review briefly describes the virus classification, clinical signs, epidemiology, diagnosis, disinfection, and vaccines related equine group A rotavirus (RVA) infection. Equine RVA is one of the most important pathogens causing diarrhoea in foals. The main transmission route is faecal–oral, and the clinical signs are diarrhoea, fever, lethargy, and anorexia (decreased suckling). Some human RVA rapid antigen detection kits based on the principles of the immunochromatographic assay are useful for the diagnosis of equine RVA infection. The kits are used in daily clinical practice because of their rapidity and ease of handling. Equine RVA is a non-enveloped virus and is more resistant to disinfectants than enveloped viruses such as equine influenza virus and equine herpesvirus. Although amphoteric soaps and quaternary ammonium compounds are commonly used in veterinary hygiene, they are generally ineffective against equine RVA. Alcohol products, aldehydes, and chlorine- and iodine-based compounds are effective against equine RVA. Inactivated vaccines have been used for equine RVA infection in some countries. Pregnant mares are intramuscularly inoculated with a vaccine, and thus their colostrum has abundant antibodies against RVA at the time of birth. According to G and P classification defined in accordance with the VP7 and VP4 genes, respectively, the predominant equine RVAs circulating in horse populations globally are G3P[12] and G14P[12] equine RVAs, but the vaccines contain only the G3P[12] equine RVA strain. Ideally, a G14P[12] equine RVA should be added as a vaccine strain to obtain a better vaccine effect.

Genetic linkage of capsid protein-encoding RNA segments in group A equine rotaviruses

Rotavirus virions are formed by three concentric protein layers that enclose the 11 dsRNA genome segments and the viral proteins VP1 and VP3. Interactions amongst the capsid proteins (VP2, VP6, VP7 and VP4) have been described to play a major role in viral fitness, whilst restricting the reassortment of the genomic segments during co-infection with different rotavirus strains. In this work we describe and characterize the linkage between VP6 and VP7 proteins based on structural and genomic analyses of group A rotavirus strains circulating in Argentinean horses. Strains with the VP7 genotype G3 showed a strong association with the VP6 genotype I6, whilst strains with G14 were associated with the I2 genotype. Most of the differences on the VP6 and VP7 proteins were observed in interactive regions between the two proteins, suggesting that VP6 : VP7 interactions may drive the co-evolution and co-segregation of their respective gene segments.

Quantification of human infection risk caused by rotavirus in surface waters from Córdoba, Argentina

Fecal contamination of water is a worrying problem because it is associated with the transmission of enteric pathogenic microorganisms that can cause many infectious diseases. In this study, an environmental survey was conducted to assess the level of viral contamination by viable enterovirus and rotavirus genome in two recreational rivers (Suquía and Xanaes) of Córdoba, Argentina. Quantitative microbial risk assessment (QMRA) was calculated to estimate the risk of rotavirus infection. Water sampling was carried out during a one-year period, the presence of total and fecal coliforms was determined and water samples were then concentrated for viral determination. Cell culture and indirect immunofluorescence were applied for enterovirus detection and RT-qPCR for rotavirus quantification. Coliform bacteria levels found in Suquía River often far exceeded the guideline limits for recreational waters. The Xanaes exhibited a lower level of bacterial contamination, frequently within the guideline limits. Enterovirus and rotavirus were frequently detected in the monitoring rivers (percentage of positive samples in Suquía: 78.6% enterovirus, 100% rotavirus; in Xanaes: 87.5% enterovirus, 18.7% rotavirus). Rotavirus was detected at a media concentration of 5.7×10(5) genome copies/L (gc/L) in the Suquía and 8.5×10(0)gc/L in the Xanaes. QMRA revealed high risk of rotavirus infection in the Suquía, at sampling points with acceptable and non-acceptable bacteria numbers. The Xanaes showed significantly lower health risk of rotavirus infection but it proved to be a public health hazard. The viral occurrence was not readily explained by the levels of bacteria indicators, thus viral monitoring should be included to determine microbiological water quality. These findings provide the first data of QMRA for recreational waters in Argentina and reveal the need for public awareness of the health implications of the use of the river waters.

Comparison of two commercial kits and an in-house ELISA for the detection of equine rotavirus in foal feces

Group A rotaviruses (RVA) are important infectious agents associated with diarrhea in the young of several animal species including foals. Currently, a variety of diagnosis methods are commercially available, like ELISA, latex agglutination and immunochromatographic assays. These commercial tests are mainly designed for the detection of human RVA; its applicability in veterinary diagnosis has been poorly studied. The aim of this study was to compare the sensitivity and specificity of two commercial diagnostic kits, Pathfinder™ Rotavirus and FASTest Rota® strip, with an in-house KERI ELISA, for the detection of equine RVA. A total of 172 stool samples from Thoroughbred foals with diarrhea were analyzed. The presence of equine RVA in samples in which only one of the three methods showed positive results was confirmed by RT-PCR. A sample was considered "true positive" when RVA was detected by at least two of the methods, and "true negative" when it tested negative by the three assays. Following these criteria, 50 samples were found positive and 122 were found negative, and were handled as reference population for the assay validation. Pathfinder™ Rotavirus assay showed 32% sensitivity and 97% specificity, FASTest Rota® strip, 92% sensitivity and 97% specificity, and KERI ELISA, 76% sensitivity and 93% specificity. Pathfinder™ Rotavirus showed 77%, FASTest Rota® strip 95%, and KERI ELISA 88% accuracy to correctly classify the samples as equine RVA positive or negative. Pathfinder failed specifically to detect equine RVA G3P12I6 genotype; such performance might be related to the specificity of the monoclonal antibody included in this kit. According to our results, differences among VP6 genotypes could influence the sensitivity to detect equine RVA in foal feces, and thus assay validation of diagnostic kits for each species is necessary. In conclusion, FASTest Rota® strip is more suitable than ELISA Pathfinder™ Rotavirus for the screening of rotavirus infection in foals. The KERI ELISA showed an acceptable performance, and could be considered a proper economic alternative for equine RVA diagnosis.

Exotic rotaviruses in animals and rotaviruses in exotic animals

Group A rotaviruses (RVA) are a major cause of viral diarrhea in the young of mammals and birds. RVA strains with certain genotype constellations or VP7-VP4 (G-P) genotype combinations are commonly found in a particular host species, whilst unusual or exotic RVAs have also been reported. In most cases, these exotic rotaviruses are derived from RVA strains common to other host species, possibly through interspecies transmission coupled with reassortment events, whilst a few other strains exhibit novel genotypes/genetic constellations rarely found in other RVAs. The epidemiology and evolutionary patterns of exotic rotaviruses in humans have been thoroughly reviewed previously. On the other hand, there is no comprehensive review article devoted to exotic rotaviruses in domestic animals and birds so far. The present review focuses on the exotic/unusual rotaviruses detected in livestock (cattle and pigs), horses and companion animals (cats and dogs). Avian rotaviruses (group D, group F and group G strains), including RVAs, which are genetically divergent from mammalian RVAs, are also discussed. Although scattered and limited studies have reported rotaviruses in several exotic animals and birds, including wildlife, these data remain to be reviewed. Therefore, a section entitled "rotaviruses in exotic animals" was included in the present review.

Global distribution of group A rotavirus strains in horses: a systematic review

Group A rotavirus (RVA) is a major cause of diarrhea and diarrhea-related mortality in foals in parts of the world. In addition to careful horse farm management, vaccination is the only known alternative to reduce the RVA associated disease burden on horse farms. The precise evaluation of vaccine effectiveness against circulating strains needs enhanced surveillance of equine RVAs in areas where vaccine is already available or vaccine introduction is anticipated. Therefore, we undertook the overview of relevant information on epidemiology of equine RVA strains through systematic search of public literature databases. Our findings indicated that over 99% of equine RVA strains characterized during the past three decades belonged to two common genotypes, G3P[12] and G14P[12], whereas most of the minority equine RVA strains were probably introduced from a heterologous host by interspecies transmission. These baseline data on RVA strains in horses shall contribute to a better understanding of the spatiotemporal dynamics of strain prevalence in vaccinated and non-vaccinated herds.

Whole genomic analyses of equine group A rotaviruses from Japan: evidence for bovine-to-equine interspecies transmission and reassortment events

Equine group A rotaviruses (RVA) are a major cause of severe diarrhea in foals. The whole genomes of only six common and three unusual equine RVA strains have been analyzed so far. To date, there are no reports on whole genomic analyses of equine RVAs from Asian countries. We report here the whole genomic analyses of three common (strains RVA/Horse-tc/JPN/BI/1981/G3P[12], RVA/Horse-tc/JPN/HH-22/1989/G3P[12] and RVA/Horse-tc/JPN/CH-3/1987/G14P[12]) and an unusual (RVA/Horse-tc/JPN/OH-4/1982/G6P[5]) equine RVA strains isolated from diarrheic foals in Japan. Strains BI, HH-22 and CH-3 shared a largely conserved genotype constellation (G3/G14-P[12]-I2/I6-R2-C2-M3-A10-N2-T3-E2-H7) with each other and with those of common equine RVAs from other continents. Phylogenetically, most of the genes of BI, HH-22 and CH-3 were closely related to those of other common equine RVAs. On the other hand, the NSP2 genes of BI and CH-3 formed a distinct lineage, and were distantly related to the other, major equine RVA cluster within the NSP2-N2 genotype. The NSP4 gene of HH-22 appeared to originate from possible reassortment events involving common equine RVAs and co-circulating bovine or bovine-like equine RVAs, revealing the presence of a bovine RVA-like NSP4 gene on a typical equine RVA genetic backbone. All the 11 gene segments of the unusual equine RVA strain OH-4 were found to be more closely related to those of bovine and bovine-like human RVAs than to those of other RVAs, providing the first conclusive evidence for artiodactyl(likely bovine)-to-equine interspecies transmission events. Taken together, these observations provided important insights into the genetic diversity of equine RVAs.

Equine rotaviruses--current understanding and continuing challenges

Equine rotaviruses were first detected in foals over 30 years ago and remain a major cause of infectious diarrhoea in foals. During this time, there has been substantial progress in the development of sensitive methods to detect rotaviruses in foals, enabling surveillance of the genotypes present in various horse populations. However, there has been limited epidemiological investigation into the significance of these circulating genotypes, their correlation with disease and the use of vaccination in these animal populations. Our knowledge of the pathogenesis of rotavirus infection in foals is based on a limited number of studies on a small number of foals and, therefore, most of our understanding in this area has been extrapolated from studies in other species. Questions such as the concentrations of rotavirus particles shed in the faeces of infected foals, both with and without diarrhoea, and factors determining the presence or absence of clinical disease remain to be investigated, as does the relative and absolute efficacy of currently available vaccines. The answer to these questions may help direct research into the development of more effective control measures.

Equine G3P[3] rotavirus strain E3198 related to simian RRV and feline/canine-like rotaviruses based on complete genome analyses

Equine group A rotavirus (RVA) strains are the most important cause of gastroenteritis in equine neonates and foals worldwide, and G3P[12] and G14P[12] are epidemiologically the most important genotypes. The genotype constellation of an unusual Argentinean G3P[3] RVA strain (RVA/Horse-wt/E3198/2008/G3P[3]) detected in fecal samples of a diarrheic foal in 2008 was shown to be G3-P[3]-I3-R3-C3-M3-A9-N3-T3-E3-H6. Each of these genotypes has been found typically in feline and canine RVA strains, and the genotype constellation is reminiscent to those of Cat97-like RVA strains. However, the phylogenetic analyses revealed only a distant relationship between E3198 and known feline, canine and feline/canine-like human RVA strains. Surprisingly, a rather close relationship was found between E3198 and simian RVA strains RVA/Simian-tc/USA/RRV/1975/G3P[3] for at least 5 gene segments. RRV is believed to be a reassortant between a bovine-like RVA strain and a RVA strains distantly related to feline/canine RVA strains. These analyses indicate that E3198 is unlikely to be of equine origin, and most likely represents a RVA interspecies transmitted virus, possibly in combination with one or more reassortments, from a feline, canine or related host species to a horse. Further studies are in progress to evaluate if this strain was a single interspecies transmission event, or if this strain started to circulate in the equine population.

Complete molecular genome analyses of equine rotavirus A strains from different continents reveal several novel genotypes and a largely conserved genotype constellation

In this study, the complete genome sequences of seven equine group A rotavirus (RVA) strains (RVA/Horse-tc/GBR/L338/1991/G13P[18], RVA/Horse-wt/IRL/03V04954/2003/G3P[12] and RVA/Horse-wt/IRL/04V2024/2004/G14P[12] from Europe; RVA/Horse-wt/ARG/E30/1993/G3P[12], RVA/Horse-wt/ARG/E403/2006/G14P[12] and RVA/Horse-wt/ARG/E4040/2008/G14P[12] from Argentina; and RVA/Horse-wt/ZAF/EqRV-SA1/2006/G14P[12] from South Africa) were determined. Multiple novel genotypes were identified and genotype numbers were assigned by the Rotavirus Classification Working Group: R9 (VP1), C9 (VP2), N9 (NSP2), T12 (NSP3), E14 (NSP4), and H7 and H11 (NSP5). The genotype constellation of L338 was unique: G13-P[18]-I6-R9-C9-M6-A6-N9-T12-E14-H11. The six remaining equine RVA strains showed a largely conserved genotype constellation: G3/G14-P[12]-I2/I6-R2-C2-M3-A10-N2-T3-E2/E12-H7, which is highly divergent from other known non-equine RVA genotype constellations. Phylogenetic analyses revealed that the sequences of these equine RVA strains are related distantly to non-equine RVA strains, and that at least three lineages exist within equine RVA strains. A small number of reassortment events were observed. Interestingly, the three RVA strains from Argentina possessed the E12 genotype, whereas the three RVA strains from Ireland and South Africa possessed the E2 genotype. The unusual E12 genotype has until now only been described in Argentina among RVA strains collected from guanaco, cattle and horses, suggesting geographical isolation of this NSP4 genotype. This conserved genetic configuration of equine RVA strains could be useful for future vaccine development or improvement of currently used equine RVA vaccines.

Molecular characterization and analysis of equine rotavirus circulating in Japan from 2003 to 2008

Using a total of 2018 fecal samples collected between 2003 and 2008 from foals with diarrhea, the molecular epidemiology of group A equine rotaviruses circulating in Japan was investigated by the reverse transcription-polymerase chain reaction (RT-PCR) typing and sequence analysis of the VP4 (P type) and VP7 (G type) genes. A total of 1149 samples showed positive reactions with RT-PCR, of which 462 samples (40.2%) were positive for G3 type, 502 samples (43.7%) were positive for G14 type, and 185 samples (16.1%) were positive for both G3 and G14 types. To examine P types, 59 G3 and 56 G14 positive samples were used. The majority of the samples (96.5%) were characterized as P[12] type. In a phylogenetic analysis, the VP4 gene of the P[12] type in Japan was found to be conserved for a long time. The VP7 sequences of the G3 type were found to be clustered in the same group as the HO-5 strain, which is a G3 strain that was isolated in 1982 in Japan. In contrast, the VP7 sequences of the G14 type, which were in circulation between 2003 and 2008, were clustered differently from those of the G14 type strains isolated in Japan in the late 1990 s. These results suggest that the VP7 gene of the G3 type has been conserved over 25 years, while the VP7 gene of the G14 type circulating between 2003 and 2008 appears to have re-emerged in or invaded Japan around 2000.

Recurrent rotavirus diarrhoea outbreaks in a stud farm, in Italy

A total of 47 stool samples were collected at the same stud farm from young foals with rotavirus diarrhoea and from their stud mares. Illness involved foals during three consecutive winter seasons. Infection in the farm appeared firstly in January-February 2008. After vanishing in the warm seasons, cases reappeared in March 2009 and 2010. Determination of the rotavirus G- and P-types was carried out using nested RT-PCR in samples collected in 2009 and 2010. A total of 19 of 47 samples resulted positive for rotavirus. The G type was determined in 19/47 samples, whereas the P genotype was determined in 17/47 samples. All equine strains presented a G14 VP7 in combination with a P[12] VP4, suggesting persistence of the same viral strain in the stud farm, during at least two consecutive winter periods. Sequence analysis of the genes encoding the outer capsid rotavirus proteins VP7 and VP4 revealed that the virus had a close relationship between strains recently isolated in the rest of Europe.

Evaluation of rapid antigen detection kits for diagnosis of equine rotavirus infection

We evaluated antigen detection kits for human rotavirus with regard to their usefulness for diagnosing equine rotavirus infection. Limiting dilution analyses showed that of the seven kits investigated the Dipstick `Eiken' Rota (Dipstick) had the highest sensitivity to two serotypes of equine rotavirus. The Dipstick did not cross-react with several equine intestinal pathogens. An investigation using 249 fecal samples indicated that the sensitivity of the Dipstick was 81.9% and 47.3%, and its specificity was 98.2% and 99.0%, and its concordance rate was 92.8% and 68.3%, compared with values obtained using reverse transcription polymerase chain reaction and reverse transcription loop-mediated isothermal amplification, respectively. Although a negative result does not preclude the possibility of equine rotavirus infection, the Dipstick would be useful as routine test for diagnosing equine rotavirus infection in daily clinical practice because of its ease of handling.

Detection of equine rotavirus by reverse transcription loop-mediated isothermal amplification (RT-LAMP)

Reverse transcription loop-mediated isothermal amplification (RT-LAMP) was applied to detection of equine rotavirus. Because equine rotavirus of the single P genotype, P[12], is predominant in the equine population worldwide, an RT-LAMP primer set was designed to target the genotype P[12] sequence and thus detect equine rotavirus. The detection limit of the RT-LAMP assay was 10(3) copies of viral RNA, whereas that of semi-nested RT-PCR for genotype P[12] was 10(5) copies. The RT-LAMP assay specifically amplified genotype P[12] but did not amplify the other P genotype strains. The RT-LAMP assay did not amplify any pathogens related to equine intestinal disorder other than rotavirus. Using 96 diarrheal stools, the RT-LAMP assay detected equine rotavirus in 58 samples, whereas semi-nested RT-PCR only detected equine rotavirus in 25 samples. The RT-LAMP assay did not detect equine rotavirus with fecal samples collected from nine healthy foals. These results indicate that the RT-LAMP assay is specific for equine rotavirus and more sensitive than semi-nested RT-PCR. Because it is easy to manipulate without the need for a thermal cycler or gel electrophoresis, the RT-LAMP assay should be applicable to diagnosis of equine rotavirus infections in diagnostic laboratories.

Rotavirus disease and vaccination: impact on genotype diversity

Temporal and spatial fluctuations in the genotype distribution of human rotaviruses are continuously observed in surveillance studies. New genotypes, such as G9 and G12, have emerged and spread worldwide in a very short time span. In addition, reassortment events have the potential to contribute substantially to genetic diversity among human and animal rotaviruses. With the recent introduction of the two rotavirus vaccines, RotaTeq and Rotarix, in many countries, it appears that the total number of hospitalizations due to rotavirus infections is being reduced, at least in developed countries that implemented a universal immunization program. However, continued surveillance is warranted, especially regarding the long-term effects of the vaccines. No data analyses are available to clarify whether rotavirus vaccine introduction would allow other rotavirus P and G genotypes, which are not covered by the current vaccines, to emerge into the human population and fill the apparent gap. This kind of data analysis is essential, but its interpretation is hampered by natural and cyclical genotype fluctuations.

Molecular characteristics of German G8P[4] rotavirus strain GER1H-09 suggest that a genotyping and subclassification update is required for G8

A rare G8P[4] rotavirus, designated GER1H-09, was detected in a stool sample from an infant suffering from repeated episodes of emesis for 2 days without diarrhea. Sequencing of all genomic RNA segments was performed, and complete coding sequences were determined. The VP7 amino acid sequence revealed a close phylogenetic relationship to human G8P[6] and G8P[8] isolates from Slovenia and Africa. GER1H-09 shared typical amino acid residues within variable regions VR3 to VR7 with those strains, and their subclassification as lineage G8-II rotaviruses is proposed. The variability in VR3 was identified as the likely reason for the failure in genotyping G8-II rotaviruses by commonly used multiplex PCR. Furthermore, the sequences of associated structural and nonstructural proteins showed high amino acid identities to DS-1-like rotaviruses. The genotype composition of GER1H-09 (G8-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2) suggests the occurrence of reassortment events between G8 genotypes and human DS-1-like G2P[4] rotaviruses.

Molecular characterization of equine rotavirus in Ireland

Group A rotaviruses are important causative agents of severe, acute dehydrating diarrhea in foals. A total of 86 rotavirus-positive fecal samples, collected from diarrheic foals from 11 counties in three of the four provinces of Ireland, were obtained from the Irish Equine Centre in Kildare during a 7-year (1999 to 2005) passive surveillance study and were characterized molecularly to establish the VP7 (G type) and VP4 (P type) antigenic specificities. Fifty-eight samples (67.5%) were found to contain G3 viruses, while in 26 samples (30.2%) the rotaviruses were typed as G14 and in 2 samples (2.3%) there was a mixed infection, G3 plus G14. All samples except for two, which were untypeable, were characterized as P[12]. Fifty-eight percent of the samples were obtained from County Kildare, the center of the Irish horse industry, where an apparent shift from G3P[12] to G14P[12] was observed in 2003. By sequence analysis of the VP7 protein, the G3 Irish strains were shown to resemble viruses of the G3A subtype (H2-like) (97.1 to 100% amino acid [aa] identity), while the G14 Irish strains displayed 93.9 to 97.1% aa identity to other G14 viruses. In the VP8* fragment of the VP4 protein, the P[12] Irish viruses displayed high conservation (92.3 to 100% aa) with other equine P[12] viruses. Worldwide, G3P[12] and G14P[12] are the most prevalent equine rotavirus strains, and G3P[12] vaccines have been developed for prevention of rotavirus-associated diarrhea in foals. Investigations of the VP7/VP4 diversity of the circulating equine viruses and the dynamics of strain replacement are important for better assessing the efficacies of the vaccines.

Diversity in Indian equine rotaviruses: identification of genotype G10,P6[1] and G1 strains and a new VP7 genotype (G16) strain in specimens from diarrheic foals in India

Rotaviruses causing severe diarrhea in foals in two organized farms in northern India, during the period from 2003 to 2005, were characterized by electropherotyping, serotyping, and sequence analysis of the genes encoding the outer capsid proteins. Of 137 specimens, 47 (34.31%) were positive for rotavirus and exhibited at least five different electropherotypes (E), E1 to E5. Strains belonging to different electropherotypes exhibited either a different serotype/genotype specificity or a lack of reactivity to typing monoclonal antibodies (MAbs) used in this study. Strains belonging to E1, E2, and E5 exhibited genotype G10,P6[1], G3, and G1 specificities and accounted for 19.0, 42.9, and 9.5% of the isolates, respectively. Though they possessed G10-type VP7, the E1 strains exhibited high reactivity with the G6-specific MAb, suggesting that the uncommon combination of the outer capsid proteins altered the specificity of the conformation-dependent antigenic epitopes on VP7. E3 and E4 strains accounted for 28.6% of the isolates and were untypeable. Sequence analysis of VP7 from E4 strains (Erv92 and Erv99) revealed that they represent a new VP7 genotype, G16. The detection of unexpected bovine rotavirus-derived G10,P6[1] reassortants, G1 serotype strains, and a new genotype (G16) strain in two distant farms reveals an interesting epidemiological situation and diversity of equine rotaviruses in India.

G8 rotavirus strains isolated in the Democratic Republic of Congo belong to the DS-1-like genogroup

Several G8P[6] and G8P[8] rotavirus strains were isolated from hospitalized patients in the Democratic Republic of Congo in 2003. To investigate their overall genomic relatedness and to determine to which genogroup they belonged, the complete genomes of strains DRC88 (G8P[8]) and DRC86 (G8P[6]) were determined. Genomic comparison of these two African G8 strains revealed that 10 out of their 11 gene segments, except for VP4, were nearly identical (>98.9% identical at the nucleotide level), suggesting that this rare G8P[8] rotavirus strain originated recently from a reassortment between a common G8P[6] strain and a strain with a P[8] specificity. A very close evolutionary relationship between 9 out of the 11 gene segments of DRC88 and DRC86 and rotavirus strains belonging to the DS-1-like (G2P[4]) "genogroup" was found, and several possible reassortment events preceding the occurrence of G8P[8] and G8P[6] human rotaviruses were hypothesized. Since the genes of G2P[4] rotavirus strains are very well adapted to infect humans, the acquirement of a new VP7 (G8) gene, and especially the replacement of P[6] (believed to be of animal origin) by P[8] (most common in human rotaviruses), might make DRC88-like rotaviruses very well equipped to become a predominant human rotavirus strain and an important pathogen on the African continent and the rest of the world. These findings have important implications for rotavirus vaccine development and highlight that typing of new rotavirus strains by merely sequencing their VP7 and VP4 genes provides us with only the tip of the iceberg regarding rotavirus diversity.

A rotavirus strain isolated from pig-tailed macaque (Macaca nemestrina) with diarrhea bears a P6[1]:G8 specificity

A distinct rotavirus strain (PTRV) was isolated in cell cultures from a stool sample obtained from a diarrheic 3-year-old female pig-tailed macaque (Macaca nemestrina) that was born at the breeding colony of the University of Washington in Seattle. Unlike other known simian rotavirus strains including vervet monkey rotavirus SA11 which bears P5B[2]:G3 or P6[1]:G3 specificity, rhesus monkey rotavirus MMU18006 with P5B[3]:G3 specificity, pig-tailed macaque rotavirus YK-1 with P[3]:G3 specificity and rhesus monkey rotavirus TUCH with P[24]:G3 specificity, the cell-culture-grown PTRV strain was shown to bear P6[1]:G8 specificity as determined by VP4 (P)- and VP7 (G)-specific neutralization assays as well as gene sequence analyses. The virus in the original diarrhea stool was also shown to bear genotypes P[1] and G8. In addition, the PTRV strain exhibited a "long" electropherotype, subgroup I specificity and NSP4 genotype A specificity. The PTRV probe formed (i) 8-9 hybrid bands with genomic RNAs of various bovine rotavirus strains and (ii) only 2-3 hybrid bands with simian rotavirus RNAs as demonstrated by RNA-RNA hybridization, suggesting a possible bovine origin of the virus. Serologic analysis of serum samples obtained from selected pig-tailed macaques in the colony suggested that a rotavirus bearing P[1]:G8 specificity was endemic among macaques for at least 8 years (1987-1994). This is the first report describing an isolation of a simian rotavirus bearing a non-G3 VP7 and possibly a P6[1] specificities. Because of its unique simian serotype, this virus may prove to be valuable in challenge studies in a non-human primate model in studies of rotavirus immunity.

Molecular characterisation of equine group A rotavirus, Nasuno, isolated in Tochigi Prefecture, Japan

In this study, equine group A rotavirus (RV-A), Nasuno, isolated from foal diarrhoea in Tochigi Prefecture, Japan was characterised genetically by sequence analysis of the genome segments encoding VP4 and VP7. The nucleotide and deduced amino acid sequences revealed high homology with P[12] RV-As (94.0-99.3% and 94.9-99.4%) and G3 RV-As (86.9-99.5% and 91.1-99.4%). Nasuno was also classified into P[12] and G3 in the phylogenetic analysis of the nucleotide sequences of the genome segments encoding VP4 and VP7.

Isolation and molecular characterisation of equine rotaviruses from Germany

A total of 26 rotavirus positive faecal samples of diarrhoeal foals, and 8 equine rotavirus isolates were examined. Viral RNA patterns were generated, G typing was performed by PCR, and a P[12]-specific DNA probe was developed for P typing. Furthermore, five equine rotavirus isolates were sequenced in the genomic regions coding for VP7 and part of VP4. Rotaviruses of genotype G3 P[12] were found in 22 faecal samples and G14 P[12] type could be found in 4 faecal samples. These findings confirm that in Germany G3 P[12] is the predominating type of equine rotaviruses.

Close relationship between G8-serotype bovine and human rotaviruses isolated in Nigeria

A bovine rotavirus, NGRBg8, isolated from the feces of a calf with diarrhea in Nigeria was characterized by reverse transcription-PCR, nucleotide sequence analysis, and Northern blot hybridization. The nucleotide sequence of the VP7 gene of the strain was most closely related to that of a Nigerian human G8-serotype strain, HMG035 (99.9%). The NSP1 gene of strain NGRBg8 is highly related (99.4%) to that of a Thai G8 bovine strain, A5-10. Northern blot hybridization revealed a high overall genomic relatedness of bovine strain NGRBg8 with human strain HMG035; all 11 RNA segments hybridized to each other. Thus, the results show the close relationship between G8 bovine and human rotaviruses in Nigeria.

Changes in the prevalence of rotavirus G and P types in diarrheic calves from the Kagoshima prefecture in Japan

G8 bovine group A rotavirus was the most predominant serotype in calf diarrheal fecal specimens examined between 1995 and 1996 in Japan [Vet. Microbiol. 66 (1999) 301]. To date, no evidence that G8 was the most predominant in the typeable specimens has been observed outside Japan. To investigate whether G8 continues to be as common as G6 and G10, the incidence of the main serotypes was determined in the same area (Kagoshima prefecture) between 1997 and 1998 by reverse transcription-polymerase chain reaction. From a total of 104 rotavirus-positive specimens, we successfully identified G type in 79 (76.0%) and P type in 71 (68.3%). The combination of G and P types varied periodically; in 1995, G10P[11] was most common. The most predominant types changed drastically in 1996, and G8 and mixed P types were the most predominant. A dramatic shift of the most predominant type occurred again in 1997 when G6P[5] was most common. This frequency of G6P[5] also continued in 1998. These results suggest that the serotypes prevailing in certain areas change periodically.

Antigenic and molecular analyses reveal that the equine rotavirus strain H-1 is closely related to porcine, but not equine, rotaviruses: interspecies transmission from pigs to horses?

We have sequenced the genes encoding the inner capsid protein VP6 and the outer capsid glycoprotein VP7 of the subgroup (SG) I equine rotavirus strain H-1 (P9[7], G5). The VP6 and VP7 proteins of the equine rotavirus strain H-1 shared a high degree of sequence and deduced amino acid identity with SG I porcine strains and serotype G5 porcine strains, respectively. Previous sequence analyses of the genes encoding the outer capsid spike protein VP4 and the nonstructural proteins NSP1 and NSP4 of equine H-1 strain also revealed a high degree of sequence and deduced amino acid homology with the prototype porcine rotavirus strain OSU (P9[7], G5). We have also confirmed and extended the VP4 and VP7 antigenic relatedness of equine rotavirus strain H-1 to porcine strains of P9[7] and G5 serotype specificities isolated in the United States, Venezuela, Argentina, and Australia based on cross-neutralization studies. In addition, the pathogenicity of tissue culture-adapted equine H-1, H-2, FI-14, FI-23, and L338, and porcine OSU rotavirus strains was compared in the neonatal mouse model. The 50% diarrhea dose (DD50) of equine H-1 was similar to that of porcine OSU and equine H-2 and L338 strains, while the DD50 of equine H-2 was > or = 50 or 315-fold lower than those of equine FI-14 or FI-23, respectively. Our sequence comparison of NSP4 of the rotavirus strains tested potentially identified amino acid residue 136, within the variable region spanning amino acids 130 to 141, as playing a role in virulence. Taken together, there is strong support to suggest that the equine rotavirus strain H-1 may represent an example of interspecies transmission from pigs to horses.

Molecular and serologic characterization of novel serotype G8 human rotavirus strains detected in Blantyre, Malawi

During a 2-year study of diarrhea among children in Blantyre, Malawi, greater than 50% of rotavirus strains genotyped by using reverse transcription-polymerase chain reaction possessed previously unrecognized combinations of the neutralization proteins VP7 and VP4. Serotype G8 rotaviruses, which have been identified recently in several African countries, were found to possess P[4] or P[6] VP4 genotype specificity. Two of these short electropherotype rotaviruses were further investigated: these comprised a P[6], G8 representative strain (MW23) and a P[4], G8 representative strain (MW333). The VP7 gene sequences of both strains exhibited greatest homology to human and animal serotype G8 rotaviruses. Sequence analysis of the VP4 gene of MW23 indicated closest identity to the P2A[6], G9 strain US1205 from the United States. The VP4 gene of MW333 was most closely related to the P[4], G12 strain L26 isolated in the Philippines and the Australian P[4], G2 strain RV-5. The NSP4 gene sequences of both strains were classified in NSP4 genetic group I. RNA-RNA hybridization demonstrated that each of these two strains is related to the DS-1 genogroup of human rotaviruses. Subgroup analysis and virus neutralization confirmed complete antigenic characterization of MW23 as subgroup I, P2A[6], G8 and MW333 as subgroup I, P1B[4], G8. The similarity of the VP7 gene sequences of the prototype strains described in this report to bovine serotype G8 rotaviruses suggests that they may represent human/bovine reassortant viruses.

Simian rhesus rotavirus is a unique heterologous (non-lapine) rotavirus strain capable of productive replication and horizontal transmission in rabbits

Simian rhesus rotavirus (RRV) is the only identified heterologous (non-lapine) rotavirus strain capable of productive replication at a high inoculum dose of virus (>10(8) p.f.u.) in rabbits. To evaluate whether lower doses of RRV would productively infect rabbits and to obtain an estimate of the 50% infectious dose, rotavirus antibody-free rabbits were inoculated orally with RRV at inoculum doses of 10(3), 10(5) or 10(7) p.f.u. Based on faecal virus antigen or infectious virus shedding, RRV replication was observed with inoculum doses of 10(7) and 10(5) p.f.u., but not 10(3) p.f.u. Horizontal transmission of RRV to one of three mock-inoculated rabbits occurred 4-5 days after onset of virus antigen shedding in RRV-infected rabbits. Rabbits infected at 10(7) and 10(5), but not 10(3), p.f.u. of RRV developed rotavirus-specific immune responses and were completely (100%) protected from lapine ALA rotavirus challenge. These data confirm that RRV can replicate productively and spread horizontally in rabbits. In attempts to elucidate the genetic basis of the unusual replication efficacy of RRV in rabbits, the sequence of the gene encoding the lapine non-structural protein NSP1 was determined. Sequence analysis of the NSP1 of three lapine rotaviruses revealed a high degree of amino acid identity (85-88%) with RRV. Since RRV and lapine strains also share similar VP7s (96-97%) and VP4s (69-70%), RRV might replicate efficiently in rabbits because of the high relatedness of these three gene products, each implicated in host range restriction.

Effect of oral rotavirus/iscom vaccines on immune responses in gnotobiotic lambs

A comparison of the effect on the immune responses in gnotobiotic lambs was made between an iscom vaccine prepared from recombinant rotavirus VP6 protein, an inactivated rotavirus/iscom-matrix vaccine and a vaccine comprising inactivated rotavirus alone. All three vaccines induced immunological priming and some degree of protection was observed after a single oral dose. However, different immune responses were induced in response to a virulent infection. The group vaccinated with the rotavirus/iscom-matrix vaccine showed a Th2-like response characterised by rotavirus-specific antibodies and a down-regulation of IFNgamma in jejunal Peyer's patches. Both Th1-like and Th2-like immune responses were induced in the group receiving the VP6 vaccine as seen by significantly increased expressions of IFNgamma and IL-6 in the jejunal Peyer's patch together with an increased percentage of CD8+ T cells in the intestine and rotavirus-specific antibodies at mucosal surfaces. Iscom vaccines given orally have the ability to induce both Th1-like and Th2-like immune responses in a ruminant model.

Single point mutations may affect the serotype reactivity of serotype G11 porcine rotavirus strains: a widening spectrum?

A panel of single and double neutralization-resistant escape mutants of serotype G11 porcine rotavirus strains A253 and YM, selected with G11 monotype- and serotype-specific neutralizing monoclonal antibodies (MAbs) to VP7, was tested in neutralization assays with hyperimmune sera raised against rotavirus strains of different serotypes. Escape mutants with an amino acid substitution in antigenic region A (amino acids [aa] 87 to 101) resulting in a residue identical or chemically similar to those present at the same positions in serotype G3 strains, at positions 87 for strain A253 and 96 for strain YM, were significantly more sensitive than the parental strains to neutralization with sera against some serotype G3 strains. Also, one YM antigenic variant (YM-5E6.1) acquired reactivity by enzyme-linked immunosorbent assay with MAbs 159, 57/8, and YO-1E2, which react with G3 strains, but not with the serotype G11 parental strain YM. Cross-adsorption studies suggested that the observed cross-neutralization by the G3-specific sera was due to the sera containing antibodies reactive with the parental strain plus antibodies reactive with the epitope(s) on the antigenic variant that mimick the serotype G3 specific one(s). Moreover, antibodies reactive with antigenic region F (aa 235 to 242) of VP7 might also be involved since cross-reactivity to serotype G3 was decreased in double mutants carrying an additional mutation, which creates a potential glycosylation site at position 238. Thus, single point mutations can affect the serotype reactivity of G11 porcine rotavirus strains with both monoclonal and polyclonal antibodies and may explain the origin of rotavirus strains with dual serotype specificity based on sequence divergence of VP7.