Molecular Epidemiological Investigation of Porcine kobuvirus and Its Coinfection Rate with PEDV and SaV in Northwest China.

Porcine kobuvirus (PKV) has circulated throughout China in recent years. Although many studies have detected it throughout the world, its molecular epidemiology has not been characterized in northwest China. To understand its prevalence, 203 fecal samples were collected from different regions of Gansu Province and tested with reverse transcription-polymerase chain reaction. In this study, we tested these samples for PKV, porcine epidemic diarrhea virus (PEDV), and sapovirus and analyzed the amplified 2C gene fragments of PKV. Overall, 126 (62.1%) samples were positive for PKV. Of the 74 piglets samples among the 203 fecal samples, 65 (87.8%) were positive for PKV. PKV infection was often accompanied by PEDV, but the relationship between the two viruses must be confirmed. A phylogenetic analysis indicated that the PKV strains isolated from the same regions clustered on the same branches. This investigation shows that PKV infections are highly prevalent in pigs in northwest China, especially in piglets with symptoms of diarrhea.

Prevalence of antibodies against transmissible gastroenteritis virus and porcine respiratory coronavirus among pigs in six regions in Japan.

A total of 2,703 pig sera from 171 farms in six regions in Japan were screened for virus-neutralizing (VN) antibody against transmissible gastroenteritis virus (TGEV). Although none of the farms had clinical signs of transmissible gastroenteritis (TGE) or vaccination against TGEV, VN antibody was detected in 14.4% of sera at 30 farms (17.5%) across all six regions. On testing of 263 VN antibody-positive sera from 27 farms with a commercial blocking ELISA to distinguish TGEV and porcine respiratory coronavirus (PRCV) antibodies, 78.3% were positive for PRCV antibody only, while 12.5% were positive for TGEV antibody only or both TGEV and PRCV antibodies. Seven of the eight TGEV antibody-positive farms were also positive for PRCV antibody. Five months after the antibody examination, a TGE outbreak occurred at one of these seven farms. These results suggest that most of the detected VN antibodies were to PRCV, and that TGEV infection might be present at some PRCV-positive farms in Japan.

Increased litter survival rates, reduced clinical illness and better lactogenic immunity against TGEV in gilts that were primed as neonates with porcine respiratory coronavirus (PRCV).

Establishing immunological memory in female piglets at a young age with PRCV was effective in inducing a secondary immune response to a limiting dose of virulent TGEV given orally 13-18 days prior to farrowing. Subsequently, because of passive antibody transfer, the offspring of these primed gilts were more efficient in surviving a lethal TGEV challenge. An average survival rate of 89% occurred in 6 litters of piglets from primed gilts that were boosted with 2.8 x 10(6) plaque forming units (PFU) of TGEV whereas 76% of the piglets survived in three litters that suckled primed gilts boosted with 3.0 x 10(5)PFU of TGEV. Non-primed gilts given identical pre-farrowing doses of TGEV had litter survival rates of 63 and 55%, respectively. Moreover, both groups of litters from primed gilts suffered less clinical illness (as measured by the extent of weight loss post-challenge) than control litters. Priming of the piglets as neonates and boosting the pregnant gilts produced an anamnestic systemic immune response and correspondingly higher milk titers in the primed gilts compared to control animals. Thus, priming piglets with PRCV was beneficial in providing resistance to TGEV and could be incorporated into a vaccine strategy that yields better protection against TGEV.

Comparison of serologic testing and slaughter evaluation for assessing the effects of subclinical infection on growth in pigs.

OBJECTIVE: To compare serologic testing with slaughter evaluation in assessing effects of subclinical infection on average daily weight gain (ADG) in pigs. DESIGN: Cohort study. ANIMALS: 18 cohorts (30 to 35 pigs/cohort) of pigs on/farms. PROCEDURE: Blood samples were collected, and pigs were weighed at 8, 16, and 24 weeks of age. Sera were tested for antibodies to porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), transmissible gastroenteritis virus (TGEV), pseudorabies virus, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae. At slaughter, skin, nasal turbinates, lungs, and liver were examined. Associations between ADG and results of serologic testing and slaughter evaluation were examined by use of multiple linear regression. RESULTS: Pathogens that had a significant effect on any given farm during any given year and the magnitude of that effect varied. However, at 16 and 24 weeks of age, a higher antibody titer was consistently associated with a lower ADG. Mean differences in ADG between seropositive and seronegative pigs were 18 g/d (0.04 lb/d) for SIV, 40 g/d (0.09 lb/d) for PRRSV, 38 g/d (0.08 lb/d) for M hyopneumoniae, and 116 g/d (0.26 lb/d) for TGEV. Of the evaluations performed at slaughter, only detection of lung lesions was consistently associated with a decrease in ADG. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that subclinical infection with any of a variety of pathogens commonly found in swine herds was associated with a decrease in ADG. Serologic testing was more effective than slaughter evaluation in assessing the impact of subclinical infection on ADG in these pigs.

Comparison of a monoclonal antibody capture ELISA (MACELISA) to indirect ELISA and virus neutralization test for the serodiagnosis of transmissible gastroenteritis virus.

An enzyme-linked immunosorbent assay (ELISA) in which the antigen is captured to the plate by monoclonal antibodies (MACELISA) was developed for the detection of antibodies to transmissible gastroenteritis virus (TGEV). The viral antigen was semipurified from TGEV-infected cells by simple ultracentrifugation. MACELISA results with 258 field sera were compared with those of a standard indirect ELISA and with the virus neutralization test (VNT). Sensitivity, specificity, and kappa values of MACELISA indicated a strong correlation with VNT results, whereas an indirect ELISA was less sensitive and much less specific than VNT. The serologic response of 4 pigs orally inoculated and intraperitoneally boostered with TGEV was compared using the 3 tests. Its sensitivity, specificity, and ability to use unpurified antigen make the MACELISA the advisable first step in TGEV serodiagnosis.

Fluid therapy trials in neonatal piglets infected with transmissible gastroenteritis virus.

The main purpose of this study was to evaluate the effectiveness of an oral fluid therapy alone or combined with parenteral administration of a 5% dextrose solution to attenuate the clinical signs and the pathophysiological consequences of transmissible gastroenteritis in neonatal piglets. Eighteen two day old conventional piglets were infected with transmissible gastroenteritis virus while six others were used as controls (Group 1). At the onset of diarrhea, infected piglets were divided into three groups of six (Groups 2, 3 and 4). Piglets in group 2 were not treated and were fed a milk replacer ad libitum. Piglets in group 3 were removed from the milk replacer and placed on an oral glucose-glycine-electrolyte solution ad libitum. Those in group 4 were placed on oral fluid therapy and received a 5% dextrose solution intraperitoneally at the rate of 25 mL/kg of body weight once a day. Blood samples were collected in heparin within minutes after the infected piglets became comatose and from the controls at four or five days of age. The following variables were measured: packed red cell volume, blood pH, total plasma protein and bicarbonate, blood urea nitrogen, and plasma glucose, creatinine, chloride, inorganic phosphorus, sodium, potassium, magnesium and calcium. Vomiting and diarrhea appeared 12 to 24 hours postinoculation in the infected piglets. There was a sudden and rapid progression into a comatose and moribund state one or two days later whether the infected piglets were treated or not.(ABSTRACT TRUNCATED AT 250 WORDS)