Rotavirus serotype G3 predominates in horses

Incidence of rotavirus and circulating genotypes in Northeast Brazil during 7 years of national rotavirus vaccination

Background and Aims

Rotavirus causes severe diarrhoea and Brazil introduced the Rotarix G1P[8] vaccine in 2006. We aimed to describe changes in rotavirus incidence and diarrhoea epidemiology before and after vaccine introduction.

Methods

Design: (i) hospital-based survey of children with diarrhoea (2006–2012); (ii) diarrhea-mortality and hospitalization surveillance (1999–2012).

Setting

(i) Aracaju and (ii) state and national level.

Results

1841 children were enrolled and 231 (12.5%) had rotavirus. Rotavirus was less frequent from January-June than from July-December (9.4% versus 20.9%, p<0.01), but the seasonal variation was less defined after 2009. Very few rotavirus cases (8–3.9%) were detected in 2011, with an increase in 2012 (13–18.5%). In 2006, unvaccinated children were more likely to have rotavirus, but thereafter unvaccinated and vaccinated children had equally low incidence. Older children and those with rotavirus were more likely to have severe diarrhea episodes. The most frequent genotype from 2006 to 2010 was G2P[4]; except in 2009, when most cases were G1P[8]. Very few G2P[4] were detected from 2011 and 50% cases in 2012 were G8P[4]. Diarrhoea-hospitalizations decreased nationally from 89,934 (2003) to 53,705 (2012; 40.3% reduction) and in the state from 1729 to 748 (56.7% reduction). Diarrhoea-deaths decreased nationally from 4368 in 1999 to 697 in 2012 (84% reduction, p<0.001) and in the state from 132 to 18 (86% reduction). These changes were much larger after vaccine introduction.

Conclusions

The vaccine was associated with substantial reductions in rotavirus incidence and diarrhoea-hospitalizations and deaths. The G2P[4] genotype predominance disappeared over time and may be replaced by other heterotypic genotypes.

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.

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.

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.

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.

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.

Identification of bovine rotaviruses in Venezuela: antigenic and molecular characterization of a bovine rotavirus strain

Two serotypes of bovine group A rotaviruses were demonstrated by enzyme-linked immunoassay (ELISA) and polyacrylamide gel electrophoresis (PAGE) in 20 of 171 faecal samples collected from diarrhoeic calves in two dairy farms in Venezuela. By serotyping ELISA using G and P serotype-specific monoclonal antibodies, bovine rotaviruses (BRV) circulating on one farm were identified as serotype G6, while BRVs circulating on the other farm were identified as serotype G10. Only one BRV (033) could be successfully isolated in MA104 cells, and the nucleotide sequences of the VP7 and the VP8* trypsin-cleavage product of the VP4 were determined. Cross-neutralization tests and comparative sequence analysis showed that BRV 033 belonged to serotype G6 and genotype P1. This is the first report of BRVs identified in Venezuela.

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

DIG-labelled ssRNA probes were prepared from variable regions of VP4 and VP7 cognate genes, and used in hybridization assays for P and G genotyping of group A cell culture-adapted equine rotaviruses and fecal samples collected from foals with and without diarrhea. The probes confirmed known P and G serotypes of sixteen cell culture-adapted strains. From one-hundred and twenty-one rotavirus-positive samples, 83 reacted when tested for their P and G genotype specific probes. From these, 71 were found to contain G3 P12 genotypes, and 11 G14 P12 genotypes. No sample reacted with H1 or L338 P and G genotype probes. This suggests that the equine rotavirus population is conservative, containing predominantly one P genotype and two G genotypes. One isolate (26/94) whose dsRNA was visualized in an agarose gel did not react with any of the equine probes, and was found to belong to G8 and P1 genotypes. This is the fourth example of a single unique equine isolate (after H1, L338, and R-22). The remaining thirty-eight untypable field isolates had no detectable dsRNA after storage for 1 to 3 years.

Prevalence of G and P serotypes among equine rotaviruses in the faeces of diarrhoeic foals

Variant types of VP4 and VP7 gene segments of faecal rotaviruses from diarrhoeic foals were identified by restriction endonuclease digestion of reverse transcription/polymerase chain reaction (RT/PCR) products. The variants observed were correlated with serotypes by determination of the sequence of representative RT/PCR products (entire coding sequence for VP7 and the VP8 region of VP4) and comparison to published sequences of equine G and P serotype genes. Both G and P serotypes could be predicted for 95/116 (82%) strains, P serotype only for a further 8 (7%) strains and G serotype only for 1 (1%) strain. All characterised strains belonged to the same P serotype, P12, although minor sequence variations were observed. Of those strains able to be assigned to G serotypes, 84/96 (87.5%) belonged to serotype G3A, and 12/96 (12.5%) belonged to serotype G14. Comparison of G serotyping by ELISA to the RT/PCR method showed that serotyping equine rotaviruses by currently available ELISA methods was prone to error. This study establishes the restricted serotypic diversity of equine rotaviruses, and the significance of serotype G14.

Cross-reactive, serotype- and monotype-specific neutralization epitopes on VP7 of serotype G3 and G5 porcine rotavirus strains

VP7 specific monoclonal antibodies raised against serotype G5 porcine rotavirus strains isolated in Venezuela showed either a serotype G5- or monotype-specific pattern of reactivity by neutralization against a panel of 53 group A rotavirus isolates representative of all established G serotypes. Monoclonal antibodies raised against two G3 porcine strains were either specific for a subset of porcine G3 strains or reactive with another subset of porcine G3 strains and with most G5 strains. Neither were reactive with G3 strains from other species. Analysis of neutralization resistant mutants selected with these monoclonal antibodies indicated that epitopes defined by cross-reactive, serotype- and monotype-specific monoclonal antibodies overlap functionally and that binding and neutralization by these antibodies depended on specific amino acid residues in the region A or C of VP7. Results indicate that a high degree of monotypic variation occurs among G5 and G3 porcine rotavirus strains and the existence of at least one common epitope shared by G5 and G3 porcine strains, in the major neutralization domain of these VP7s.

Serological and genomic characterisation of group A rotaviruses from lambs

Four lamb rotaviruses were characterised serologically by reactions with monoclonal antibodies and genomically by hybridisation assays and sequencing. Each was found to be distinct. Three viruses belonged to the bovine genogroup and were of subgroup I. These viruses possessed serotypes G3, G6, and G10. Their corresponding P types were P1, P11, and P14 respectively. The only previous isolation of a rotavirus with VP4 of type P14 was also from lambs. The fourth isolate was G9P8, which is the first record of a G9 rotavirus from a species other than man.

Prevalence of neutralizing antibodies to 9 rotavirus strains representing 7 G-serotypes in sheep sera

Neutralizing antibodies to 9 rotavirus strains representing serotypes G1, G3, G5, G6, G8, G9, and G10 were investigated in 212 ovine serum samples from 3 age groups, 1-week-old lambs, 2- to 3-months-old lambs and adult sheep. All sera from 1-week-old lambs had neutralizing antibodies to all 9 rotavirus strains. Both neutralizing antibody titers and prevalences to all 9 strains markedly decreased in the 2- to 3-months-old lamb group and increased again in the adult sheep group. Also, adult sheep sera neutralized a larger number of rotavirus strains than 2- to 3-months-old lamb sera. The highest neutralizing antibody titers and prevalences were found to strains B223 and K923, representing serotype G10, to strain RRV, representing serotype G3, and to strain NCDV, representing serotype G6, indicating that these could be the predominant 3 rotavirus serotypes in Spanish sheep. The rotavirus serotypes infecting sheep observed by us differ from those described for cattle, where G6 is the most prevalent serotype followed by G10, and G3 has been seldom found. Very low prevalences were observed for strains WA and OSU representing serotypes G1 and G5 respectively, suggesting that they probably do not infect sheep and neutralizing antibodies found are derived from heterotypic responses to other serotypes. Intermediate prevalences and titers were found to strains UK (serotype G6), 69M (serotype G8) and WI61 (serotype G9). Neutralizing antibodies distinguished between different strains sharing their VP7 specificity: B223 and K923, a bovine and an ovine serotype G10 strains, and NCDV and UK, two serotype G6 bovine rotavirus strains with different VP4 antigen.

Comparative amino acid sequence analysis of the major outer capsid protein (VP7) of porcine rotaviruses with G3 and G5 serotype specificities isolated in Venezuela and Argentina

Seven porcine group A rotavirus strains isolated in Venezuela were shown to be antigenically related to serotype G3 (five strains) or to serotype G5 (two strains), whereas two strains isolated in Argentina were classified as serotype G5. The serological classification of eight of these strains was confirmed by sequence analysis of the gene encoding the VP7 glycoprotein. A high degree of homology was observed among strains belonging to the same G serotype, although some variations in the serotype-specific regions were detected among different strains. Comparison with the published VP7 amino acid sequences of serotype G3 indicated that most porcine rotavirus strains are more closely related to each other and to human rotavirus strains than to rotavirus strains isolated from other species. Amino acid sequence comparison among serotype G5 porcine strains revealed that Venezuelan porcine isolates were more closely related to the American strain OSU, while the Argentinian strains had a higher similarity to the Australian strain TRF-41. This report confirms the worldwide distribution of these G serotypes among the porcine population.

Equine rotaviruses with G14 serotype specificity circulate among venezuelan horses

Two group A rotavirus strains isolated from diarrheic foals in Venezuela were classified as belonging to G14 serotype by cross-neutralization tests and on the basis of the homology of the sequenced VP7 gene. This report confirms that rotavirus strains of G14 serotype specificity circulate among equine populations.

Genetic analysis of equine rotavirus by RNA-RNA hybridization

Serotype G3 equine rotaviruses isolated in Japan made up a common genogroup and were classified into two different genotypes. The genomes of serotype G3 equine rotaviruses with an identical electropherotype (isolated from 1982 to 1989) were very closely related to each other regardless of the year in which they were isolated. Serotype G3 equine rotavirus BI originating from England belonged to the same genogroup of serotype G3 equine rotaviruses isolated in Japan, although BI was classified as having a different genotype. The genomes of both serotype G10 equine rotavirus R-22 and serotype G10 calf rotavirus were closely related to each other.

Characterization of a G14 equine rotavirus (strain CH3) isolated in Japan

Antigenic and genomic properties of equine rotavirus strain CH3 isolated in Japan were studied by cross-neutralization tests and nucleotide sequence determination of the VP4 and VP7 genes. It was shown that the strain CH3 belongs to G14 and shares VP4 genotype with strain H2.

Immunogens of rotaviruses

Rotaviruses cause gastroenteritis in neonates of many animal species including cattle, swine, horses, dogs, cats, chickens and turkeys. Rotavirions are nonenveloped, are about 75 nm in diameter, have a double capsid, and contain 11 double-stranded RNA segments as their genome. Several antigenically distinct groups of rotaviruses have been identified and have been alphabetically designated as A through G. Group A rotaviruses were the first group of rotaviruses isolated and are the most commonly detected rotaviruses in diarrheic animals. Group A rotaviruses have two surface proteins, VP4 and VP7, both of which are important in serotype determination and in inducing neutralizing antibodies and protective immunity. Multiple serotypes of group A rotavirus based on glycoprotein VP7 (designated as G types) and based on VP4 (P types) have been identified. The immune response to rotaviruses is essentially serotype specific, however, cross-reactive or heterotypic epitopes have also been identified. Currently acceptable methods for immunogen quantitation include the induction of neutralizing antibody in host or laboratory animals. The in vivo efficacy of vaccines against rotavirus-associated gastroenteritis remains the standard method against which in vitro methods must be compared. Several animal models have been developed which could potentially be used in evaluating the efficacy of candidate vaccines. Monoclonal antibodies to rotavirus immunogens are also currently available and serve as valuable reagents for in vitro quantitation of rotaviral immunogens.

Genomic relatedness of five equine rotavirus strains with different G serotype and P type specificities

Overall genomic relatedness among five equine rotavirus strains and their relatedness to representative human and animal rotavirus strains were investigated by RNA-RNA hybridization tests. The genomes of strains FI-14, FI-23 and H2 were highly related to one another. Strain L338 had only a low degree of genomic relatedness to the other four equine rotavirus strains. Strain H1 also showed little genetic relatedness to the other equine strains. The genome of the strain H1, however, was highly related to those of porcine rotavirus strains OSU, Gottfried and YM. Genomic relatedness of four equine rotavirus strains (FI-14, FI-23, H2 and L338) to human and other animal rotavirus strains was low, whereas several RNA segments of strain H1 showed a relatedness to those of human strain Wa.

Rotaviral diarrhea

Rotavirus poses a challenge each foaling season to farm managers and veterinarians in intensive horse breeding areas throughout the world. By understanding the epidemiology of the disease as well as characteristics of the virus, veterinarians can make sound recommendations on prevention and control of outbreaks. Even when effective prophylactic products are developed, farm management practices, including quarantine, disinfection, and hygiene, will always need to be in force to prevent any contagious disease outbreak.

Electropherotypes, serotypes, and subgroups of equine rotaviruses isolated in Japan

Electropherotypes (ET), serotypes, and subgroups of equine rotaviruses isolated from foals in Japan were determined. The ETs of 136 isolates from 1981 through to 1991 were divided into six groups: ET-A-ET-F. The ET-A, -B, -C, -D, -E, and -F were present in 3, 1, 121, 9, 1, and 1 strains, respectively. Representative viruses of ET-A, -B, -C, and -D were identified as serotype G3. Viruses of ET-E and -F were identified as serotypes G 10 and G 5, respectively. The four representative viruses of serotype G 3 did not belong to either subgroup I or II. The two viruses of serotypes G 5 and G 10 belonged to subgroup I. Serotype G 3 strains possessing ET-C were prevalent among the foals throughout the study period.

Characterization of full-length and polymerase chain reaction-derived partial-length Gottfried and OSU gene 4 probes for serotypic differentiation of porcine rotaviruses

To determine the VP4 (P type) specificity of porcine rotaviruses, full- and partial-length gene 4 probes were produced from cloned Gottfried and OSU porcine rotavirus genomic segment 4 cDNAs. The gene 4 segments from the prototype Gottfried (VP7 serotype 4) and OSU (VP7 serotype 5) porcine rotavirus strains were selected for study because of their distinct P types and the occurrence of rotaviruses with similar serotypes among swine. Partial-length gene 4 cDNAs were produced and amplified by the polymerase chain reaction (PCR) and encompassed portions of the variable region (nucleotides 211 to 612) of VP8 encoded by genomic segment 4. The hybridization stringency conditions necessary for optimal probe specificity and sensitivity were determined by dot or Northern (RNA) blot hybridizations against a diverse group of human and animal rotaviruses of heterologous group A serotypes and against representative group B and C porcine rotaviruses. The PCR-derived gene 4 probes were more specific than the full-length gene 4 probes but demonstrated equivalent sensitivity. The Gottfried PCR-derived probe hybridized with Gottfried, SB2, SB3, and SB5 G serotype 4 porcine rotaviruses. The OSU PCR-derived probe hybridized with OSU, EE, A580, and SB-1A porcine rotaviruses and equine H1 rotavirus. Results of the hybridization reactions of the PCR-derived gene 4 probes with selected porcine rotavirus strains agreed with previous serological or genetic analyses, indicating their suitability as diagnostic reagents.

Human and bovine serotype G8 rotaviruses may be derived by reassortment

The origin of, and relationship between human and bovine serotype G8 rotaviruses were investigated by genomic hybridisation. Radiolabelled mRNAs of human G8 rotaviruses 69M (isolated in Indonesia) and HAL1271 (isolated in Finland), and bovine rotaviruses KK3 (G10) and NCDV (G6), were used as probes. The products of liquid hybridisation between the probes and the genomic RNA of human and bovine rotaviruses, including bovine G8 rotavirus 678 (isolated in Scotland) and two other Finnish human G8 rotaviruses HAL1166 and HAL8590, were examined by separation in polyacrylamide gels. The genomes of Finnish human G8 rotaviruses were similar to those of bovine G6 and G10 rotaviruses. Neither Indonesian human G8 nor bovine G8 viruses had high levels of similarity to each other or to other bovine and human rotaviruses. Thus these three epidemiologically distinct G8 rotaviruses have different origins and may be derived by reassortment with rotaviruses of a third, as yet unknown, host species. The similarity between the Finnish isolates and the bovine isolate NCDV suggests that they have diverged recently and that these human G8 rotaviruses may be derived from a zoonotic infection, or alternatively, from the live rotavirus vaccine of bovine origin which has been used to vaccinate Finnish children.

Evidence for two serotype G3 subtypes among equine rotaviruses

Ten cultivable equine rotavirus isolates, two of North American, six of British, and two of Irish origin, were compared with standard rotavirus strains and with each other by cross neutralization, neutralization with a panel of monoclonal antibodies (MAbs), hybridization to a simian rotavirus (SA-11) VP7 gene probe, and reaction with rotavirus subgrouping and serotyping MAbs in enzyme-linked immunosorbent assays. Six isolates, two of which had previously been serotyped as G3 by other workers, were found to be serotype G3; one was confirmed to be G5, and three were not related to serotypes G1 to G10. The serotype G3 strains were divisible into two subtypes, G3A and G3B, on the basis of cross neutralization. This division was also apparent in reactions with neutralizing VP7-specific MAbs and in the liquid hybridization assay. Two of the isolates were not bound by either subgroup MAb, six were bound by both subgroup I and II MAbs, and two were bound by only the subgroup I MAb. The assays used in this characterization provide a range of epidemiological information for use in future field investigations.