Natural transmission of group A rotavirus within a pig population

Five litters of piglets born within two days of each other, together with their dams, were investigated for faecal excretion of group A rotavirus antigen from birth to two months old. All the 50 piglets in these litters became infected with the virus between 19 and 35 days old. Rotavirus excretion was first seen in one litter which was housed with other litters not included in this study. Two days later, piglets of the second litter in another farrowing room began to excrete rotavirus, and then infection spread to the other three litters in the same room. Within each of these litters, one or two piglets were infected early and thereafter infection spread to other piglets. It took four to 10 days for rotavirus to infect every piglet within a litter, and 16 days in total before all piglets in the five litters were infected. No rotavirus antigen was demonstrated in faeces from sows during the investigation period.     

Group A rotavirus excretion patterns in naturally infected pigs

Cross-sectional and cohort studies were conducted in a piggery to investigate the excretion pattern of group A rotavirus in pigs. The cross-sectional survey revealed that 47 (9 per cent) of 521 pigs sampled were excreting rotavirus in the faeces. No rotavirus antigen was detected in the faeces of pigs either less than one week or over two months old. The prevalence of infection increased with age over the sucking period, and was greatest at five weeks old. Diarrhoea was observed in only eight (17 per cent) of the pigs excreting rotavirus. Sixteen piglets from four litters were selected and faecal samples collected daily from each animal from birth to two months old. All the piglets excreted group A rotavirus and the range of ages at which they first became infected was between 13 and 39 days. The average duration of excretion in individual piglets was 7.4 days. Ten of 13 sucking piglets which excreted rotavirus developed diarrhoea soon after it was first detected.     

Verification of sensitivity and specificity of group a rotavirus detection in piglets faeces with monoclonal blocking ELISA methods

Monoclonal antibodies to group A rotavirus Vp6 protein were prepared and used for verification of three blocking enzyme-linked immunosorbent assay (ELISA) modifications to detect rotavirus A. Selected competitive blocking ELISA (CB-ELISA) and electron microscopy (EM) were used for examination of 194 field faecal samples of piglets affected with diarrhoea. Rotavirus was detected in 43 samples (22.2%) by CB-ELISA method, whereas in 26 (13.4%) samples by EM examination. However, of 26 samples positive by EM, rotavirus A was detected by CB-ELISA in 19 (73.1%) samples; indicating the share of group A rotavirus in all cases of gastroenteritis caused by rotavirus. The sensitivity and specificity of the CB-ELISA was verified both by inclusion of control samples containing transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhoea virus (PEDV) in each analysis and by comparative examination of samples with the commercial ELISA kit. The CB-ELISA sensitivity was positively affected by examination of samples in the presence of chelating agent.     

Use of polymerase chain reaction for the differentiation of Group A bovine rotavirus G6, G8, and G10 genotypes in the North Island of New Zealand

AIM: To determine the presence of Group A rotavirus G6, G8, and G10 genotypes in calves in the North Island of New Zealand. METHODS: Faecal samples from 730 calves (<6 weeks old) with diarrhoea were collected during 2006 and 2007 from seven regions in the North Island of New Zealand. The samples were screened for the presence of Group A rotavirus antigen, using a commercial ELISA. Forty-one samples from different farms were randomly selected out of the 385 ELISA-positive samples and tested using PCR for the presence of G6, G8, and G10 genotypes of rotavirus. RESULTS: The PCR analysis of 41 antigen-positive field samples revealed that 37 (90%) contained genotype G6, three (7%) genotype G10, one sample (2%) had both G6 and G10 genotypes, and none contained genotype G8. CONCLUSIONS: Rotavirus genotype G6 was the predominant genotype found in this preliminary study and was present in all seven regions studied. Genotype G10 was also found in some regions of the North Island, whereas genotype G8 was not found in any sample. CLINICAL RELEVANCE: This is the first report on rotavirus G genotypes present in calves in the North Island of New Zealand.     

Comparison of direct electron microscopy and enzyme immunoassay for the detection of rotaviruses in calves, lambs, piglets and foals

Direct electron microscopy (EM) and enzyme-immunoassay (rotazyme) results for the detection of rotaviruses in 346 enteric specimens from calves, lambs, piglets and foals were compared. The rotazyme test was at least 3 times more sensitive than direct EM in diagnosing infection. Rotavirus antigen was demonstrated by rotazyme in 22% of 280 scour samples and in 27% of 66 samples from non-scouring animals. There was an association between diarrhoea and higher amounts of rotavirus antigen. This prevalence of rotaviruses detected in animals with diarrhoea highlights the significant involvement of other pathogens identified in the study including Eimeria, Cryptosporidia, Escherichia coli, Campylobacter, and other viruses.     

Rotavirus associated diarrhoea in nursing piglets and detection of antibody against rotavirus in colostrum, milk and serum

A blocking method of ELISA for the detection and quantification of antibody against porcine rotavirus in serum, colostrum and milk has been compared with a plaque reduction test. The results obtained with the two techniques correlated (Fig. 1). Antibody against rotavirus was demonstrated in 384 serum samples representing 25 swine farms, indicating a widely spread and dense distribution of the infection with porcine rotavirus among Danish swine. The antibody contents in milk samples from 7 gilts and sows from 2 farms with a previously diagnosed problem with rotavirus associated diarrhoe showed a rapid decline during the first few days of the lactation periods (Fig. 1). An increase in the contents of rotavirus specific antibody was observed from day 15 in the milk samples from one of the gilts. The excretion of rotavirus with feces from the 7 litters of piglets were followed through the suckling period. Rotavirus war found in all litters but one and the virus was excreted in periods ranging from 4 to 9 days.     

An Outbreak of Diarrhoea in One-week-old Piglets Caused by Group A Rotavirus Genotypes P[7],G3 and P[7],G5

Thirty-two group A isolates of rotavirus detected in faecal samples from diarrhoeic piglets, were selected for P and G genotyping using a Multiplex RT-PCR. Ten isolates, from animals less than 8 days old, characterized an outbreak of diarrhoea caused by group A rotavirus in animals. P[7],G3 (CRW8-like) and P[7],G5 (OSU-like) genotypes were detected in 5 animals each. Isolates of a group A rotavirus of genotypes compatible with the OSU prototype were those most frequently identified in single infections in older animals (20/32 strains). In addition to these, 20 isolates from piglets with diarrhoea caused by group A rotavirus, collected between May 1998 and June 1999, but not from the outbreak month, were analysed. These isolates were used to compare the types observed on the farm outside the outbreak in May 1999 and the CRW8-like genotype was found in none of these faecal samples. P[7],G5 was the most frequent genotype (10/20 strains). No outbreak of diarrhoea caused by rotavirus in 1-week-old piglets was found in any other period during the 13 months of this study.     

Rotavirus infection in calves in Bangladesh

Faecal samples from 434 calves under 1 year of age (307 diarrhoeal and 127 normal) were collected from three dairy farms and one village in selected areas of Bangladesh. The samples were tested by an enzyme-linked immunosorbent assay (ELISA) to detect the presence of rotavirus antigen. Of 402 dairy calves tested, 28 (7.0%) were positive, of which 21 (7.2%) were from diarrhoeic calves and 7 (6.3%) from non-diarrhoeic calves. Rotavirus infection varied from farm to farm (2.7–9.2%) and there was no positive response from any of the 32 village calves. Rotavirus was most commonly found in calves of 1 week of age or less (up to 22.2% in one group) but was not found in any calves later than 6 months of age. More than 80% of rotavirus-positive samples from diarrhoeic calves exhibited a titre of 128 or more (geometric mean 345±4.5), whereas non-diarrhoeal calves had titres less than or equal to 128 (geometric mean=29±1.9), suggesting that rotavirus infection in calves in Bangladesh was mostly associated with diarrhoea.     

猪A群轮状病毒BJ株的分离与鉴定

轮状病毒是引起幼龄动物和儿童病毒性腹泻的主要病原,轮状病毒的分离鉴定为该病的流行病学调查和分子生物学特性研究奠定了基础。本研究采集北京某猪场腹泻发病仔猪肠内容物,将其接种MA104细胞,分离得到一株能产生明显细胞病变的病毒。对分离毒株进行胶体金、实时荧光定量RT-PCR和免疫荧光等方法鉴定,并对分离毒株的VP4、VP6和VP7基因进行测序及序列分析。结果表明,分离毒株为猪A群轮状病毒。按照A群轮状病毒的最新分类方法,确定该分离株VP4、VP6和VP7基因的基因型分别为P[13]型、I5型和G11型。因此,将该分离株命名为Rotavirus A pig/China/BJ/2015/G11P[13]。     

Isolation and Identification of Porcine Group A Rotavirus BJ Strain

Rotavirus infections are a major cause of viral diarrheas in young animals and children. Isolation and identification of rotavirus make a contribution to epidemiological survey and molecular biology study.A strain of porcine rotavirus was isolated in MA104 cell cultures from the intestinal contents of piglets with diarrhea in Beijing.The virus was identified to be porcine rotavirus by immunochromatography strip test, Real-time RT-PCR, immunofluorescence test and sequencing analysis.According to the sequence analysis, the virus was classified as group A porcine rotavirus, the genotype of VP4, VP6 and VP7 genes belonged to P[13], I5 and G11, respectively.The virus was designated Rotavirus A pig/China/BJ/2015/G11P[13].     

Epidemiological studies of piglet diarrhoea in intensively managed Danish sow herds. III. Rotavirus infection

The prevalence of rotavirus infection was studied in 1090 litters from 26 sow herds. Samples of normal, semifluid and watery stools were examined for rotavirus by an ELISA-test on faeces. Rotavirus was detected in 77% of the herds and in 30.5% of the litters (prevalence rates). The highest prevalence rate was seen in piglets between 21 and 41 days of age. Gilts' litters had a very high prevalence during the first week of life. Apart from this, no difference was found between litters from gilts and older sows. Rotavirus was detected more frequently in semiliquid, loose stools than in normal or watery stools, and an association between virus detection and diarrhoea could not be demonstrated. However, litters which shedded rotavirus during the suckling period had lower weight gains and higher incidence rates of respiratory diseases than virus-free litters. Litters weaned at 2 weeks in battery cages had slightly increased risk of shedding rotavirus compared to litters weaned in more traditional systems. The study revealed that rotavirus is widespread in Danish swine herds. The findings give evidence to suggest that the type of mild diarrhoea in 3-week-old piglets known as steatorrhoea or "white scours" may be associated with rotavirus infection, possibly in combination with E. coli and other agents. The high prevalence in piglets weaned at 2 weeks plus the higher morbidity and mortality among such piglets sustain the conclusion that piglets should not be weaned before 3 weeks of age or below a body weight of 6-7 kg.     

FACTORS CONTRIBUTING TO POSTWEANING DIARRHOEA IN A LARGE INTENSIVE PIGGERY

Some aspects of postweaning diarrhoea (PWD) in a piggery during the first week after early weaning were investigated. A haemolytic enterotoxigenic strain of E. coli (0149: K88: H10) was regularly recovered from piglets with PWD while rotavirus was demonstrated on a number of occasions. Prior to weaning piglets were either free of, or shed very few, haemolytic E. coli in their faeces. However, all piglets were excreting haemolytic E. coli between 5 and 7 days after weaning. The role of rotavirus in PWD was unclear. There appeared to be a direct relationship between serum antibodies to rotavirus in the sow at farrowing and those of the piglets soon after birth. The decline of maternal neutralising antibody to rotavirus coincided with the immediate postweaning period (3 to 5 weeks after birth). This was followed by an increase in antibody levels, 5 to 8 weeks after birth. There was no significant difference in the growth rate between affected and unaffected piglets over a period of 120 days. Medication of water during the first week after weaning had no significant effect on the incidence of PWD in the herd. A change in both the weaner diet and the weaning procedure reduced piglet mortality associated with PWD by more than half.     

The calf reo-like virus (rotavirus) vaccine: an ineffective immunization agent for rotaviral diarrhea of piglets.

Rotavirus, in a commercially available calf vaccine, did not replicate in newborn colostrum-free piglets inoculated orally with one half of a calf dose. Gross and microscopic examination of these vaccinated piglets revealed no lesions consistent with rotaviral infection and vaccinated piglets were susceptible to challenge by porcine rotavirus. Challenged piglets vomited, had diarrhea and became severely dehydrated. Rotavirus was visualized in their gut fluid. Villi in the small intestines were shortened, blunted and fused. Rotaviral antigens were seen in enterocytes.     

Frequency of enteropathogen detection in suckling and weaned pigs with diarrhea in Japan.

Fecal samples from suckling (n=153) and weaned (n=116) piglets with diarrhea in Japan were examined for shedding of viral, bacterial, and parasitic pathogens using culture, microscopic, and polymerase chain reaction methods. In suckling piglets, diarrhea was attributed to infection with a single etiologic agent in 60.8% of cases and with combinations of agents in 22.2%. In weaned piglets, diarrhea was attributed to a single etiologic agent in 43.1% and to combinations of agents in 47.4% of cases. Rotavirus was the most prevalent agent in suckling (67.3%) and weaned (65.5%) piglets. The detection of other pathogens was associated with age of the animals examined. Coccidia were predominantly isolated from suckling piglets, whereas Escherichia coli was found predominantly in weaned piglets. Although a relationship was not observed between detection rate of rotavirus and age of piglets, a single group of rotavirus was detected in 87.5% of suckling piglets whereas multiple groups were detected in 51.6% of weaned piglets. The results of this study confirm that diarrhea in piglets can, to a variable degree, be causally associated with multiple agents. Additionally, these results suggest reasons why this syndrome can be difficult to control.     

The shedding of group A rotavirus antigen in a newly established closed specific pathogen-free swine herd.

A longitudinal study was undertaken in a newly established specific pathogen-free (SPF) swine herd to determine the dynamics of rotavirus antigen shedding in a closed swine facility. Pregnant SPF gilts which populated the herd, and their offspring, were monitored weekly for three consecutive lactations. Fecal samples were assayed for the presence of group-specific viral antigen by a solid phase immunoassay (ELISA). Results indicate that in the week prior to farrow, 35% of samples from gilts/sows contained rotavirus antigen. During nursing, 37% of the gilts'/sows' fecal samples also contained virus antigen. Over the course of three farrowings, every gilt/sow in the herd excreted virus antigen. Virus antigen was present in 25% of the samples tested from nursing pigs and in 70% of the samples tested from pigs in the postnursing period; 95% of the litters excreted virus antigen either while nursing or postweaning. Seasonal incidence in virus antigen excretion was noted with proportionally more suckling pigs virus antigen-positive in summer and proportionally more sows/gilts positive during winter. Diarrhea occurred only rarely in the sampled population. Although piglets shed rotavirus subclinically, ELISA positive feces from piglets of each lactation caused severe disease when fed to neonatal gnotobiotic pigs. Electropherotyping of these passaged viruses indicated minor variation in RNA banding patterns over time.     

一种轮状病毒特异抗体ELISA检测方法

在实验室条件下,建立较为快速的轮状病毒抗体ELISA检测方法。利用组织培养的轮状病毒SA11株经初步的浓缩和纯化后,作为包被抗原包被酶标板。SDS-PAGE分析表明,经浓缩纯化后,轮状病毒的主要抗原均存在。将测试血清用SA11中和后,轮状病毒或其抗原免疫血清(肠黏液,粪便悬液)的OD490值比中和前有明显的下降,下降比率大于45％,而对照组血清的OD490值与中和前相比没有明显的变化,下降比率小于9％。表明用此ELISA体系检测轮状病毒抗体具有特异性。     

Detection of a mammalian-like group A rotavirus in diarrhoeic chicken

The present investigation describes detection of a mammalian-like electropherogroup A rotavirus in chicken with diarrhoea. This also records the first detection of a rotavirus in an avian species from India. During the investigation 75 diarrhoeic faecal samples collected from adult chicken were screened for the presence of group A rotavirus antigen by sandwich ELISA. All three samples positive for rotavirus antigen revealed 11 bands of RNA in polyacrylamide gel electrophoresis (PAGE). In contrast to avian group A rotavirus, segment 5 was found to migrate closer to 6 as is the case with mammalian group A rotaviruses. Segments 7, 8 and 9 were found to migrate as a tight triplet, which is characteristic of group A rotavirus.