ABSTRACT
Introduction: Infectious diseases in the suckling period of pigs are common and cause financial losses. To improve the health of the piglets and decrease the use of antibiotic drugs, sufficient immunological protection is necessary. In suckling piglets, the oral intake of antibodies is a highly effective measure for protection. We tested whether antibodies in spray-dried blood plasma of pigs can be absorbed by newborn piglets after oral application. Materials and Methods: The spray-dried plasma was positive for antibodies against the porcine reproductive and respiratory syndrome virus (PRRSV), the porcine circovirus 2 (PCV-2), the porcine epidemic diarrhoea virus, the porcine parvovirus and others. The study was conducted on 210 suckling piglets in a pig breeding farm in Austria. The newborn piglets were randomly divided into four groups: K, P, P+bov and P24. Group K received no treatment;group P received spray-dried plasma orally before the first intake of colostrum;group P+bov received spray-dried plasma dissolved in bovine colostrum;and group P24 received spray-dried plasma 24 hours after birth. In addition to blood samples of the mother sows, blood samples were taken from the piglets on days zero, one, seven, ten and 14 after application of the spray-dried plasma. The serum was tested by ELISA for the antibodies in the spray-dried plasma. The antibody resorption and clinical outcome were compared between the groups.
ABSTRACT
PURPOSE: According to the European Public Health Authority guidance for ending isolation in the context of COVID-19, a convalescent healthcare worker (HCW) can end their isolation at home and resume work upon clinical improvement and two negative RT-PCR tests from respiratory specimens obtained at 24-h intervals at least 8 days after the onset of symptoms. However, convalescent HCWs may shed SARS-CoV-2 viral RNA for prolonged periods. METHODS: 40 healthy HCWs off work because of ongoing positive RT-PCR results in combined nasopharyngeal (NP) and oropharyngeal (OP) swabs following SARS-CoV-2 infection were invited to participate in this study. These HCWs had been in self-isolation because of a PCR-confirmed SARS-CoV-2 infection. NP and OP swabs as well as a blood sample were collected from each participant. RT-PCR and virus isolation was performed with each swab sample and serum neutralization test as well as two different ELISA tests were performed on all serum samples. RESULTS: No viable virions could be detected in any of 29 nasopharyngeal and 29 oropharyngeal swabs taken from 15 long-time carriers. We found SARSCoV- 2 RNA in 14/29 nasopharyngeal and 10/29 oropharyngeal swabs obtained from screening 15 HCWs with previous COVID-19 up to 55 days after symptom onset. Six (40%) of the 15 initially positive HCWs converted to negative and later reverted to positive again according to their medical records. All but one HCW, a healthy volunteer banned from work, showed the presence of neutralizing antibodies in concomitantly taken blood samples. Late threshold cycle (Ct) values in RT-PCR [mean 37.4; median 37.3; range 30.8-41.7] and the lack of virus growth in cell culture indicate that despite the positive PCR results no infectivity remained. CONCLUSION: We recommend lifting isolation if the RT-PCR Ct-value of a naso- or oropharyngeal swab sample is over 30. Positive results obtained from genes targeted with Ct-values > 30 correspond to non-viable/noninfectious particles that are still detected by RT-PCR. In case of Ct-values lower than 30, a blood sample from the patient should be tested for the presence of neutralizing antibodies. If positive, non-infectiousness can also be assumed.