Evidence of bovine viral diarrhea virus transmission by back pond water in experimentally infected piglets

Abstract

Swine can be infected by bovine viral diarrhea virus (BVDV). However, transmission routes among pigs are still unknown. The objective of the present study was to induce experimental infection of BVDV-1 in weaned piglets and to assess the potential transmission through pen back pond water, used to facilitate heat exchange of the pigs housed in barns. Two repetitions (BP1 and BP 2) were performed using 12 piglets proven to be free BVDV (n=6 per repetition) allocated into three groups: control, sentinels and infected with two piglets each. The piglets were placed in stainless steel isolators. The infected group received an inoculum containing BVDV-1, Singer strain. The piglets remained in the cabinets for 25 days, during which samples of nasal swab were collected daily and blood sampled weekly. At the end, the piglets were euthanized, necropsied and organ fragments were collected for histopathology, immunohistochemistry and RT-PCR. In the first experiment (BP1) the infected animals shed the virus between days 6 and 21 post-infection. Regarding the sentinel group, shedding occurred in only one piglet, on the 20th day after infection, and seroconversion was observed on the 25th day post-infection. In BP2, infected piglets I3 and I4 shed the virus on days 4 and 21 post-infection, respectively. Only one sentinel piglet (S3) she the virus on day 13 post-infection. Therefore, it was concluded that pigs can become infected with BVDV-1 and shed potentially infectious viral particles consequently, being able to transmit the virus to other pigs through back pond water.

Bovine Viral Diarrhea Virus: Recent Findings about Its Occurrence in Pigs

“…Clinical signs similar to CSF, and sudden death [ 24 ] were also observed when the BVDV strain was isolated from both pigs and cattle from the same farm [ 24 ]. On the other hand, several recent studies with experimental infection did not report the presence of clinical signs of infection [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. This may occur due to an inadequate level of viremia or a low virulence strain, biotype of the virus, host adaptation and/or route of inoculation [ 31 , 32 , 33 , 34 , 35 ].…”

“…Three studies were separately conducted with three groups of two weaned piglets separated by isolation cabinets: the challenged, sentinel, and control groups. The isolation cabinets were arranged to allow only a specific route of transmission, namely airborne, nose-to-nose [ 25 ], and by back pond water [ 26 ]. Although all challenged piglets shed the virus and seroconverted, only transmission by the back-pond water was confirmed since sentinel animals also shed the virus and seroconverted in this study.…”

“…The course of BVDV infection in pigs will depend on the virulence of the viral strain and the pig immune response [ 66 ] and may be limited [ 44 ]. Even so, the presence of the virus in the nasal secretions of infected animals demonstrated that pigs could act as a source of infection, thus facilitating the spread in the herd [ 26 , 27 ]. Although BVDV does not pose the same threat to pig herds as it poses to ruminants, it may lead to the development of a range of clinical signs and culminate in a serological cross-reaction with the CSFV, interfering negatively in classical swine fever monitoring and surveillance programs, and misleading diagnosis of the disease [ 10 ].…”

Thermostabilization of viruses via complex coacervation

“…However, in the context of complex coacervation, we must balance the charge state of our viruses with that of the two complexing polypeptides. 42 Therefore, because both PPV 58 and BVDV are stable at pH 8.0, 59 we elected to perform our experiments at a solution pH of 8.0 using 10 mM HEPES as a neutral, zwitterionic buffer. This solution condition maximizes the negative charge of the virus particles while limiting the loss of charge from the poly(lysine).…”

Prevalence of Bovine Viral Diarrhea Virus Infections in Pigs on Jeju Island, South Korea, from 2009–2019 and Experimental Infection of Pigs with BVDV Strains Isolated from Cattle

“…In addition, the failure to detect BVDV in fecal and nasal samples infers that BVDV transmission is unlikely to occur between pigs. However, other papers suggest that the presence of the virus in the nasal secretions of infected pigs could act as a source of infection, thereby facilitating spread within the herd [ 32 , 38 ]. Although BVDV does not pose the same threat to pig herds as it does to ruminants, it may interfere with CSF monitoring and surveillance programs, leading to misleading diagnosis of the disease [ 11 ].…”