BVDV 2018 Flashcards
What are the different subtypes of BVDV?
BVDV1a-u
BVDV2a-d
What is thought to be the most common subtype of BVDV?
BVDV1b
What type of virus is BVDV and how does this complicate how effective vaccines are?
BVDV is a single-stranded RNA virus, meaning it is heterogenous and genetic and antigenic changes are expected.
The RNA polymerase of BVDV lacks proofreading, mutations and substitutions are expected.
Mismatches between vaccine strains and field strains can compromise the efficacy of these vaccines, but the amount of antigenic variation in the viruses currently in circulation is unknown.
What contributes to the establishment of PI animals, in regards to genetic variation>
Mutation rate of BVDV in infected pregnant animals appears to be higher than in non pregnant animals. The virus variants might arise as a result of chance or because of a specific replicative advantage.
This not only contributes to virus persistence and spread in the population, but also greatly diversifies the virus.
What happens to the BVDV infection in crias and piglets, when they are congenitally infected?
These animals are born viremic and seronegative to the infecting BVDV but clear the infection upon seroconversion after several weeks to months of life.
Do heterologous hosts shed BVDV efficiently and cause transmission to susceptible animals?
PI heterologous hosts have had BVDV detected in nasal swabs for the entire life of the animal. Another possible mode of viral shedding appears to be seen in semen of PI heterologous hosts.
There is strong evidence that BVDV is shed by acutely infected and PI heterologous hosts providing potential for transmission to other animals.
How might BVDV be maintained in heterologous populations?
Exposure to infected cattle is the most plausible source of infection. Also, heterologous hosts could be incidental spillover hosts, maintain BVDV independent of cattle contact or contribute to BVDV maintenance together with other artiodactyl hosts.
Can currently available diagnostic tests developed for cattle be accurately used in heterologous species?
There is low quality evidence that BVDV diagnostic testing methods available for cattle are appropriate for testing of BVDV infection in heterologous hosts.
How does BVDV affect lymphocyte actions?
Blood lymphocytes from calves with BVDV-induced immunosuppression had lethargic responses to mitogen stimulation, as compared to healthy cattle.
How does BVDV affect neutrophils?
Neutrophils from PI cattle have decreased ability of phagocytosis of Staph. aureus, decreased cytochrome C reduction, reduced function of the antimicrobial myeloperoxidase-H2-O2-halide system, and decreased antibody-independent cell-mediated cytotoxicity.
Multiple studies have found the degree of viremia (BVDV) after experimental challenge to be related to the severity of resulting disease. Why might this occur?
Viruses reaching higher viral titers in blood may be associated with more severe disease, due to: replication characteristics of the virus leading to higher titers or the ability of the virus to induce a greater degree of immunosuppression, allowing it to replicate more efficiently or a combination of both.
High evidence has shown that BVDV infection leads to decreases in blood concentration of neutrophils, lymphocytes, or platelets, or both lymphocytes and platelets.
List evidence for the role that BVDV plays in BRDC.
- Asooc. with BVDV infection with naturally occurring resp disease.
- Increases in BRD morbidity and death in cattle or groups exposed to PI cattle, versus individuals or groups not exposed.
- Gross or microscopic resp pathology in cattle experimentally challenged with BVDV
- Resp disease of increased severity in cattle challenged with BVDV at or near the time cattle are challenged with other agents, as compared to control cattle challenged with the other agent as alone
Do MLV and KV vaccines provide similar protection against the different clinical manifestations of BVDV infection in cattle.
There is high quality evidence that clinical protection offered by MLV BVDV versus KV BVDV vaccines to pregnant cattle is not similar. MLV vaccines provide better clinical protection against fetal infection, abortion and generation of PI calves.
What are the primary goals of BVDV vax of young nonpregnant cattle?
Prevention of morbidity (viremia, pyrexia, nasal discharge, diarrhea, leukopenia and thrombocytopenia) and death.
What are the primary goals of BVDV vax of pregnant cattle?
Prevention of early embryonic death, abortion, and generation of PI/seropositive calves after acute BVDV infection during gestation.
