lecture 4- BVDV and BLV Flashcards
what is BVDV
bovine viral diarrhea virus
How many types of BVDV are there
2 types with many classifications within each type
what are the envelope proteins of interest in the genome of BVDV
E ms, E1, E2
true or false: BVDV only infects bovine
false!!
is it likely that wildlife carry BVDV and transfer it to cows?
no- more likely the other way around
what are the requirements to be a potential wildlife reservoir for BVDV? 4 things
1) be susceptible to BVDV
2) shed BVDV (and replicate)
3) maintain BVDV in the population (shed it enough to maintain)
4) have sufficient contact with cattle that allow spillback infections
what happens with pigs that get BVDV
poor conception rates, abortion, stillborn piglets, often no clinical signs
what are hairy shakers?
sheep infected with BVDV that present with neurological signs/tremors
If a cow is infected with BVDV during her first month of pregnancy, what typically happens? why?
early emryonic death and return to estrus
BVDV infects mom and then the fetus who has no immunity
If a cow is infected with BVDV during her 2-4th month of pregnancy, what typically happens? why?
The calf will be persistently infected with BVDV and will be antibody negative. it is possible that abortion/malformation could occur too.
this happens because the fetus cannot yet distinguish between self and non-self antibodies
what does it mean if a cow is a PI for BVDV?
They are a carrier of the disease and will be shedding it, despite having no clinical signs. They are immunosuppressed.
If a cow is infected with BVDV during her 5-9 months of pregnancy, what typically happens? why?
the calf might be born normal with positive antibodies, or they might be aborted / have malformations
at this point the calf can recognize self from non-self, so can respond with antibodies to fight off infection.
what is the pathogenesis of BVDV?
oronasal infection
tonsils
regional lymphnodes
blood circulation
lymphoid tissue of the GI track and lungs
thymus/bone marrow/spleen
all other organs (depending on virulence)
in PIs, which organs test positive for BVDV? why is this significant?
all organs are BVDV positive, leading to immunosuppression
what does it mean if a PI calf is infected with cytopathic BVDV? how does it occur?
This happens in PI’s and is indicative of mucosal disease, in that this form causes cell death.
it occurs by a genetic mutation occurring in the non-cytopathic form of BVDV.
What does it mean if a PI cow is infected with non-cytopathic BVDV?
The disease is able to replicate without causing disturbance/cell death.
what are the clinical signs mucosal disease?
discharge from nose, foaming from mouth, lesions in oral cavity/esophagus
what is the genetic basis for mucosal disease?
non-cytopathic virus is mutated via RNA recombination at the NS2 NS3 junction, resulting in production of the NS3 protein next to NS2-3 polyprotein
why is mucosal disease considered a “fluke of evolution”?
it kills PIs (fast!)
What is the most effective way to eradicate BVDV?
euthanasia of PIs
how does vaccination affect the prevalence of PIs?
in unvaccinated herds, it is a ticking time bomb before an outbreak occurs, then nearly all calves will become PI
is vaccinating PIs out of the herd effective?
no- its too late.
what is BLV
bovine leukemia virus
why is BLV important to the dairy industry?
- decreased milk production
- decreased cow longevity
- clinical leukosis
- export restrictions
- animal welfare
- consumer concerns
can cows overcome BLV?
no- once they are infected, they are always infected
is BLV significant in Canada?
yes! upwards of 90% of herds are infected
what kind of virus is BLV
deltaretrovirus
what cells does BLV infect?
B-lymphocytes (cells that make antibodies)
what is the viral mechanism of BLV?
makes a copy of genome and inserts that into the DNA of cow
what are the 3 ways that the immune system can respond to BLV?
- asymptomatic / aleukemic stage
- persistent lymphocytosis
- leukemia/lymphoma
how does infection of CD5+ B cells by BLV impact B cells and T cells?
polyclonal expansion of B cells (increasing) and abnormal function of T cells and monocytes (decreased)
in what 2 ways does BLV cause tumors?
- cis- activate oncogenes by inverting into genome
- trans- virus produces mediators that induce tumors
what are clinical signs of BLV?
retrobulbar process -> exophtalmus, generalized edema, enlarged lymphnodes, cardial lymphosarcoma, other lymphosarcomas (spleen, intestinal)
how is BLV transmitted between animals?
blood, colostrum, milk, in utero, natural breeding, iatrogenic, bulls
what is used to test for BLV
blood or milk using antibody test
how do you manage BLV?
biosecurity, minimize blood, monitor colostrum/milk
what does it mean to have a high proviral load?
many cells contain copies of integrated provirus
are proviruses (like BLV) silent?
no!
is there a vaccine for BLV?
no
what family is BVDV a part of?
Flaviviridae
What family is BLV a part of
Retroviridae
what is the structure of BVDV (Flavi)
enveloped, positive sense (ssRNA)
what is the structure of BLV?
enveloped, positive sense
what is the replication strategy of BVDV?
ssRNA+ (viral genome acts as mRNA)
recall the family is Flavi
what is the replication strategy of BLV?
ssRNA+ retro (virion reverse transcriptase –> ssDNA –> cellular pol2 –> mRNA)
retroviruses insert into host genome
