Seroprevalence of porcine respiratory coronavirus infection in Spanish breeding sows

The seroprevalence of porcine respiratory coronavirus (PRCV) among breeding sows was estimated in Castilla y León, the largest region in Spain, by a cross-sectional study. Serum samples (1247) were taken from sows from 58 different herds for this purpose throughout 1988 and were tested by a monoclonal antibody-capture ELISA (MACELISA), a test which detects antibodies to both transmissible gastroenteritis virus (TGEV) and PRCV. In order to discriminate positive sera to both coronaviruses, a blocking inhibition ELISA was used for all MACELISA-positive sera. By MACELISA, 31.4% of sera tested were positive and all of them were confirmed specifically as PRCV-positive by blocking inhibition ELISA, thus ruling out the presence of TGEV in the sampled area: 64% of the farms had at least one PRCV-seropositive sow, indicating that the infection was widespread Farms were classified into three categories, according to size and management practices. No significant differences were found in the prevalence rates among the three farm types; there was, however, a highly significant correlation between increasing farm size and increasing within-farm seropositivity.     

Pathogenicity of concurrent infection of pigs with porcine respiratory coronavirus and swine influenza virus

Combinations of porcine respiratory coronavirus (PRCV) and either of two swine influenza viruses (H1N1 or H3N2) were administered intranasally and by aerosol to six- to eight-week-old specific pathogen-free pigs. The clinical responses, gross respiratory lesions and growth performances of these pigs were studied and compared with those of single (PRCV, H1N1 or H3N2) and mock-infected animals. PRCV infection caused fever, growth retardation and lung lesions, but no respiratory symptoms. Infection with swine influenza viruses caused rather similar, mild symptoms of disease, with H1N1 infection being the least severe. Combined infections with influenza viruses and PRCV did not appear to enhance the pathogenicity of these viruses. Furthermore, viruses were isolated more frequently from tissues and nasal swabs taken from 'single' than 'dual' infected animals, suggesting a possible in vivo interference between replication of PRCV and swine influenza virus.     

Experimental fetal infection with bovine viral diarrhea virus. I. Virological and serological studies.

The serological and virological results of an experimental infection of bovine fetuses with bovine viral diarrhea virus are presented. Four fetuses, 120-165 days gestational age, were inoculated in utero with a second passage virus strain. Two fetuses received a sham-inoculum. A humoral immune response in the virus-inoculated fetuses, was demonstrated three weeks later. In three fetuses only IgM and IgG1 were detectable. The serum from the fourth fetus also contained IgG2 and IgA. Bovine viral diarrhea virus-neutralizing antibodies were detected in two fetuses. These two fetuses inoculated at 135-150 days gestational age, represent the youngest reported bovids, giving a specific response in three weeks following an experimental infection with bovine viral diarrhea virus. The fetal sera did not contain heat-labile factors, which could mediate the neutralization. The virus was not reisolated from any of the fetuses, but viral antigen was nevertheless demonstrated by immunocytochemical methods in sections of several of the fetal organs, primarily lymphoid tissues.     

A serological survey of canine respiratory coronavirus in New Zealand

ABSTRACT

Aims: To determine the seroprevalence of canine respiratory coronavirus (CRCoV) in New Zealand dogs, and to explore associations with age, sex, breed, month, and geographical region of sampling and reported presence of clinical signs suggestive of respiratory disease.

Methods: A total of 1,015 canine serum samples were randomly selected from submissions to a diagnostic laboratory between March and December 2014, and were analysed for CRCoV antibodies using a competitive ELISA. Logistic regression analysis was used to determine associations between seroprevalence of CRCoV and breed category, age, sex, sampling month, region, and reported health status of dogs.

Results: Overall, 538/1,015 (53.0%) samples were seropositive for CRCoV, with 492/921 (53.4%) positive dogs in the North Island and 46/94 (49%) in the South Island. Age of dog, sampling month, region, and presence of abnormal respiratory signs were included in the initial logistic regression model. Seroprevalence was higher in dogs aged ≥3 compared with ≤2 years (p?<?0.01). The lowest seroprevalence was observed in July (30/105; 28.5%) and August (32/100; 32%), and the highest in June (74/100; 74%). Seroprevalence in dogs from Auckland was higher than in dogs from the Hawkes Bay, Manawatu, Marlborough, and Waikato regions (p?<?0.05). Abnormal respiratory signs (coughing, nasal discharge, or sneezing) were reported for 28/1,015 (2.8%) dogs sampled. Seroprevalence for CRCoV tended to be higher among dogs with respiratory signs (67.9 (95% CI?=?47.6–83.4)%) than dogs with no reported respiratory signs (52.6 (95% CI?=?49.5–55.7)%).

Conclusions: Serological evidence of infection with CRCoV was present in more than half of the dogs tested from throughout New Zealand. Differences in CRCoV seroprevalence between regions and lack of seasonal pattern indicate that factors other than external temperatures may be important in the epidemiology of CRCoV in New Zealand.

Clinical relevance: Our data suggest that CRCoV should be included in investigations of cases of infectious canine tracheobronchitis, particularly if these occur among dogs vaccinated with current vaccines, which do not include CRCoV antigens.     

Seroprevalence of porcine respiratory coronavirus in selected Korean pigs

A total of 446 serum samples from 88 herds in Korea were examined for antibody to porcine respiratory coronavirus (PRCV) using blocking enzyme-linked immunosorbent assay (ELISA). All serum samples were collected from 24- to 26-week-old finishing pigs between December 1998 and June 1999. By ELISA, 237 out of 446 sera tested (53.1%) and 54 out of 88 sampled herds (61.3%) were positive against PRCV. Of 446 sera from 88 herd tested, 185 (41.5%) serum samples from 22 (25%) herds were seronegative against PRCV and transmissible gastroenteritis virus infection. Our data suggested that seropositive herds for PRCV are distributed diffusely throughout South Korea.     

Isolation of a porcine respiratory, non-enteric coronavirus related to transmissible gastroenteritis

A porcine respiratory, non-enteric virus which is related to the coronavirus transmissible gastroenteritis virus (TGEV) has been isolated in pigs and in cell culture. The isolate was designated TLM 83. It has become very widespread and enzootic among the swine population in Belgium and in other swine raising countries. It causes an infection of the lungs and appears to spread by aerogenic route. It does not replicate in the enteric tract. The experimental infection in conventional and gnotobiotic pigs in isolation remains subclinical. The infection, either experimental or in the field, results in the formation of antibodies which neutralise the classical enteric TGEV. Based on this relationship, this virus is assumed to be a new TGEV-related porcine respiratory coronavirus or TGEV itself which has totally lost its tropism for the enteric tract.     

Pathogenicity of experimental infection with 'pneumotropic' porcine coronavirus

Virus localisation and lesions were studied in 14-one-week-old piglets following combined intranasal-oral inoculation with a British isolate of 'pneumotropic' porcine coronavirus (PCV) and were compared with the effects of transmissible gastroenteritis virus (TGEV) infection in five piglets. Unlike TGEV-infected piglets, all PCV-inoculated piglets remained clinically healthy. Seroconversion was detected at seven days after inoculation. Mild bronchointerstitial pneumonia involving terminal airways was consistently present at two days after infection and thereafter. Both PCV and TGEV infected bronchiolar epithelium and alveolar macrophages but, unlike TGEV, replication by PCV in villous enterocytes was limited and did not cause villous atrophy.     

猪繁殖与呼吸综合征血清学检测技术研究进展

猪繁殖与呼吸综合征(PRRS)又称蓝耳病,是由猪繁殖与呼吸综合征病毒(PRRSV)引起的以妊娠母猪的繁殖障碍以及仔猪和成长猪的呼吸困难为主要特征的传染病。目前,血清学检测是猪繁殖与呼吸综合征病毒抗体检测最常用的方法,文章对血清中和试验、酶联免疫吸附试验、过氧化酶单层细胞试验、间接免疫荧光试验等猪繁殖与呼吸综合征病毒抗体诊断技术的原理及其应用现状作一综述,并对各种检测方法的优缺点进行了分析。     

Losses due to porcine peproductive and respiratory syndrome in a large swine farm

The aim of the presented studies was to demonstrate losses and economical consequences of Porcine Reproductive and Respiratory Syndrome (PRRS) outbreak in a large swine farm in Poland. Prior to the occurrence of PRRS the piglets' mortality rate did not exceed 6%, losses among weaners and fatteners were lower than 3.5% and the percentage of sows that farrowed before term was 1.4%. During the first month after onset of the outbreak 25.6% of sows farrowed before 110 days of pregnancy, the percentage of mummies was 21.7%, the percentage of piglets that died before weaning was 43.3%, losses among fatteners and weaners were four times greater, and average production of weaned piglets per sow per year dropped from 21.1 to 18.1. Farrowing rate dropped from 80.5 to 47.7% and even 12 months after onset of the outbreak did not reach the level found before the outbreak. Expenses dealing with preventing and treating secondary infections, during the 12 months after the outbreak were on average 60% higher than, those found, during the previous year.     

Sites of replication of a porcine respiratory coronavirus related to transmissible gastroenteritis virus

A porcine respiratory coronavirus (PRCV) was inoculated by aerosol into nine hysterectomy-derived and colostrum-deprived pigs at the age of one week. They were killed at different times after inoculation and tissues were sampled for virus isolation and immunofluorescence. Results indicate that virus replicated to high titres in the respiratory tract. Replication mainly occurred in alveolar cells but also in epithelial cells of nasal mucosa, trachea, bronchi, bronchioli, in alveolar macrophages and in tonsils. After primary replication in the respiratory tract, viraemia occurred. Virus also reached the gastrointestinal tract after swallowing. Subsequently, PRCV was observed to replicate in the ileum. The infection spread within a few days from the ileum to the duodenum. Replication in the small intestine remained limited to a few cells located in or underneath the epithelial layer of villi and, or, crypts. The cell type could not be identified. Virus was isolated from mesenteric lymph nodes in all pigs, but immunofluorescence was not observed. Results show that small changes in molecular structure between transmissible gastroenteritis virus and PRCV resulted in important changes in host cell tropism.     

Virological studies of paramyxovirus type 1 infection of pigeons

Over a period of three months in 1985, paramyxovirus type 1 infection was demonstrated for the first time in Canada, in six flocks of pigeons in Ontario, Alberta, and British Columbia. The paramyxovirus type 1 isolates did not cause clinical disease when serially passaged four times in four-to six-week-old chickens, and isolates were classified as lentogenic before and after such serial passage. Further cases of paramyxovirus type 1 clinical disease have not been reported since the last of these six outbreaks in August 1985.     

Sero-epidemiological survey of porcine respiratory coronavirus (PRCV) infection in breeding herds in southeastern Spain.

In 1987 we conducted a sero-epidemiological survey in the Murcia Region (South-East Spain) to discover the prevalence and spread of PRCV-infection among breeding pigs and farms and determine the association between herd size and geographical zone with PRCV-infection. The Murcia Region was divided into four geographical zones and the farms classified by size in four categories. The random sample was statistically representative of both the breeding stock and farms in each geographical zone. We analysed 6,000 breeding pigs from 480 farms. The immunological techniques employed were indirect ELISA and blocking ELISA. The prevalence (P +/- IC) of PRCV-seropositive breeding pigs and infected breeding farms was 14.53 +/- 0.89% and 21.87 +/- 7.83% respectively. On 55% of the infected farms, the prevalence of seropositive breeding pigs was 60-100%. PRCV-infection appears spread throughout the four geographical zones of the Murcia Region. However, a significant association (p less than 0.01) was observed between geographical zone and the prevalence of PRCV-infection. A herd size of greater than 50 breeding pigs had a greater risk (p less than 0.01) of PRCV-infection.     

Differentiation between transmissible gastroenteritis virus and porcine respiratory coronavirus using a cDNA probe.

A plasmid, pG3BS, containing a cDNA clone from the 5' coding region of the peplomer glycoprotein gene appears to be specific for enteric transmissible gastroenteritis virus (TGEV) strains and for live-attenuated TGEV vaccines. This cDNA probe is used to differentiate porcine respiratory coronavirus (PRCV) isolates from TGEV field and vaccine strains by a slot blot hybridization assay. Probe pG3BS also hybridizes to canine coronavirus (CCV) RNA but does not hybridize to antigenically related feline infectious peritonitis virus (FIPV) RNA. The RNAs of 13 enteric TGEV isolates from the United States, Japan, and England, 4 US-licensed live-attenuated TGEV vaccines, and antigenically closely related CCV were detected by pG3BS. The RNAs of FIPV and 3 US isolates of PRCV did not react with pG3BS but were detected by a TGEV-derived plasmid, pRP3. Pigs infected with either PRCV or TGEV test serologically positive for TGEV antibody by the serum neutralization test. Characterization of the virus circulating in a swine herd by the pG3BS probe will differentiate between an enteric TGEV and a respiratory PRCV infection.     

Pathogenicity of three isolates of porcine respiratory coronavirus in the USA

The pathogenicity of three isolates of porcine respiratory coronavirus (AR310, LEPP and 1894) from the USA was assessed in specific pathogen-free pigs. Pigs inoculated with 1894 developed mild respiratory disease and pigs inoculated with AR310 and LEPP developed moderate respiratory disease from four to 10 days after they were inoculated, but all the pigs recovered fully by 14 days after inoculation. Gross and microscopic examination revealed mild (1894) to moderate (AR310 and LEPP) multifocal bronchointerstitial pneumonia from four to 10 days after inoculation. The lesions were characterised by necrotising bronchiolitis, septal infiltration with mononuclear cells, and a mixed alveolar exudate. No clinical signs or microscopic lesions were observed in control pigs that had not been inoculated.     

Experimental infection of pigs with the porcine respiratory coronavirus (PRCV): measure of viral excretion.

Twelve pigs were experimentally infected with a porcine respiratory coronavirus (PRCV) by the oronasal route. Viral excretion was measured daily by two means-deep nasal swabs and air samples obtained in a cyclone sampler. Clinical signs were very slight on infected pigs. Airborne virus could be recovered from day 1 to day 6 post-infection in the cyclone sampler as well as in petri dishes placed in the same loose-box. Viral titres obtained from nasal swabs were significantly correlated with those obtained from air samples. Different collection media were compared. The most efficient media for the collection of infectious viral particles contained a protective agent such as foetal calf serum.     

某猪场猪2型圆环病毒感染的诊断

猪2型圆环病毒(PCV2)是引起断奶仔猪多系统衰竭综合征(PMWS)的主要病原,此外,PCV2还可能与猪皮炎肾病综合征、猪呼吸系统综合征、仔猪先天性震颤等疾病有关.PMWS临床症状主要表现为进行性消瘦,生长发育受阻,皮肤苍白或有黄疸,体表淋巴结肿大,腹泻,贫血和呼吸道症状等.     

Prevalence of porcine reproductive and respiratory syndrome virus and porcine circovirus type 2 in piglets after weaning on a commercial pig farm in Japan

To investigate the transition in concentration of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) and antibody for these viruses in serum, serum samples were collected from 29 pigs on weaning day and at 7, 14, 21, 28, 53, 84, and 120 days after weaning. The concentration of circulated PRRSV and PCV2 in serum was measured by real-time RT-PCR and real-time PCR, respectively. The specific antibody for PRRSV and PCV2 was measured using ELISA. PRRSV was not detected on 0 days post-weaning (dpw). The specific antibody for PRRSV began to increase as the concentration of PRRSV in serum increased, and the level of PRRSV then tended to decrease. PCV2 was detected in 12 of 28 pigs on 0 dpw. The concentration of PCV2 and the specific antibody for PCV2 showed a similar tendency to those of PRRSV. The correlation analysis suggests that a decline in the daily weight gain coincided with an increase in the PRRSV concentration. Pigs with a higher antibody titer against PRRSV or PCV2 on 0 dpw showed the lower level of PRRSV or PCV2, respectively.