Viral Respiratory Disease Flashcards
(105 cards)
1
Q
clinical signs of viral airway disease
A
fever, lethargy, anorexia, serous nasal discharge, lymphadenopathy, cough
+/- multiple horses affected
2
Q
treatment of viral respiratory disease
A
- supportive care
- rest, NSAIDs, maybe abx, maybe antivirals (usually stay away tho)
3
Q
why is making an etiologic dx important? (testing)
A
influences outbreak control measures!!
- biosecurity measures: mode of transmission
- length of quarantine period
- vaccination protocols
4
Q
what tests detect antigen or genome?
A
virus culture
PCR assays
immunodetection
ELISA assays
5
Q
T/F: a suspicion of EVA requires testing and reporting
A
true: is a reportable disease, better to be safe than sorry
6
Q
what tests detect antibodies?
A
serologic assays
typically requires demonstration of seroconversion (4x increase in the titer): exception is EHV-1 CF serology
7
Q
your horse has acute nasal discharge and you want to determine the etiology. what test is best to do?
A
nasal swab
if it was a couple weeks after and symptoms were resolved; would do serology (ab response is increasing days after shedding)
7
Q
if you have an outbreak in a group of animals, who do you want to test?
A
- sick horses at varying stages
- +/- healthy contacts
- collect all potential samples (serum, whole blood, swabs)
- immunlogically “naiive” animals
8
Q
resp and ocular disease in young horses herpes
A
EHV-1/4
9
Q
abortion herpes horses
A
EHV- 1/4
10
Q
CNS disease herpes horses
A
EHV-1
11
Q
genital lesions and coital exanthema
A
EHV- 3
12
Q
what herpes virus causes abortions?
A
EHV-1
13
Q
T/F: gammaherpesviruses are much more host adaptive
A
true; very long infective periods and long viremia periods as well
potential causes of asthma, ocular issues, but clinical significance remains largely unknown
14
Q
what group of herpesviruses do we mainly see in horses?
A
alphaherpesviruses: EHV 1, 3, 4
15
Q
clinical signs of EMPF
A
coughing, weight loss, fever, exercise intolerance, respiratory distress
16
Q
what causes equine multinodular pulmonary fibrosis?
A
EHV-5: gammaherpesvirus
17
Q
EHV-5
A
- widely distributed throughout horse pop’ln, even in asymptomatic horses
- equine multinodular pulmonary fibrosis
- gammaherpesvirus
18
Q
how does EMPF get induced by EHV-5?
A
some indication that the virus is not a problem as long as lungs are healthy. when something happens to lung tissue, a healing response and fibrous response gets activated, and you get an overwhelming disease process
= exuberant scar tissue formation because the virus is present. not the virus itself causing the issues, but is a lung injury happening in the face of this virus that causes this
19
Q
what family of herpesviruses have longer periods of active replication and thus more opportunities for spread?
A
gammaherpesvirus
20
Q
what is the host range of EHV-4?
A
horses
20
Q
EHV-1 and EHV-4 are examples of
A
alphaherpesviruses
21
Q
what is the host range of EHV-1?
A
horses + camelids
camelids: neuro disease, ocular disease
22
Q
how does EHV-1 affect camelids?
A
- neurologic disease
- ocular disease: blindness, retinitis, chorioreitinits, optic neuritis
23
clinical signs of EHV-1 and 4
fever, lethargy, anorexia, serous nasal dc, lymphadenopathy, cough
23
does EHV-1 or EHV-4 affect camelids?
EHV-1
24
abortions with EHV-1
- intrauterine or after
- occur 9-120 days p.i
- often during late gestation (after 7 months)
- fetuses typically fresh
25
are neonatal foals susceptible to EHV-1 ?
YES. in utero infx vs after birth
- born sick or become sick 1-2 days after
- rapidly progressive viral pneumonitis
- may survive 1-2 weeks
26
neurological disease in horses virus
EHM: equine herpesvirus myeloencephalopathy
- severity can vary clinical signs
- slight hindlimb incoordination to paralysis (urine dribbling, reduced anal and tail tone can occur, all the way to limb issues
26
poster child of horse with EHM (equine herpesvirus myeloencephalopathy)
hindlimb ataxia, bladder dysfx, reduction in tail and anal tone
26
you see a horse with hindlimb ataxia, bladder dysfx, reduction in tail and anal tone. what do you immediately diagnose
EHV-1
27
what herpesvirus causes abortion and neurologic signs?
EHV-1
27
Equine herpes viruses are
Ubiquitous (latency)- once you get it, you are infected. Most horses we deal with are latently infected
28
T/F: elimination of equine herpes viruses from horse populations is impossible
True
29
What herpesvirus was able to be eliminated by culling infected animals?
Pseudorabies
29
Epidemiology of equine herpesvirus
Latent carrier state
Deactivation during periods of stress
Virus shed in nasal secretions
Infection of susceptible contacts
Virus shed in nasal secretions
Establishment of latency
Repeat
37
What are situations where herpesvirus will reactivate in horses?
Transport, handling, rehousing, weaning, high doses of steroids, coming back from shows, springtime
Start to see outbreaks in horses that have contact with others who are shedding during these times
38
Reactivation from latency (EHV)
Transport, handling, rehousing, weaning, high doses of steroids
- typically asymptomatic
- results in “silent” shedding
- potential for disease appearance in closed horse populations
39
Why might some vets be cautious about giving horses steroids?
There has been talk about it causing reactivation of EHV. Dr Landolt not very worried tho
40
Pathogenesis of EHV 1
- virus enters the cell via receptor
- replicates in resp epithelium
- “hitches a ride” in WBC (lymph’s + others)
- goes to regional lymph nodes (submandib!)
- replicates again in submandib ln
- virus-infected cells leave ln and cause a cell-associated viremia*** virus sits within the cell, is not free floating within the bloodstream
- adhere to endothelial cells which allows the virus to jump from WBC into the endothelial cells which, where it again causes endothelial inflammation, which bring sin inflammatory cells
- virus in the immune privileged sites will cause vasculitis
- the vasculitis is what causes the inflammation that goes a long; is not necessarily the virus but is the adherence that leads to vasculitis, which then causes hemorrhage and infarcts
41
Why is pathogenesis of EHV 1 unique?
Causes a cell-associated viremia: is not free-floating, virus is in the cell. Has implications for treatment and vaccines
Not every EHV-1 causes the same level of this viremia; viruses that are most prevalent for neuro disease or abortions are typically a higher tittered viremia than viruses that don’t have significant systemic consequences
42
How long does EHV-1 cell-associated viremia persist for?
Up to 21 days and is prerequisite for abortion and myeloencephalopathy
43
In the pathogenesis of EHV-1, what needs to happen before you will get abortion and myeloencephalopathy?
EHV-1 cell-associated viremia!!
44
Pre-requisite for abortion and myeloencephalopathy in EHV-1
Cell-associated viremia
45
How does myeloencephalopathy result from EHV-1?
Vascular injury after endothelial cell infection leading to vasculitis, thrombosis, ischemia of neutrophil
46
Neuropathogenic EHV-1
Single AA substitution in the polymerase gene 83% neurological isolates
- not 100% associated between non neuropathogenic vs neuropathogenic
- BUT this strain seems to be spreading easier than the non-neuropathogenic strains
- somewhat of a difference in terms of outbreak severity depending on which isolate you are dealing with
47
Non-neuropathogenic strain of EHV 1
AA substitution absent in 95% of non neurological isolates
BUT not always 100% associated between
48
T/F: the level of viremia will correlate to the chances of subsequent neurological disease
True: the longer and stronger the viremia present, the more chances there are that the patient will get severe consequences like neuro disease
49
T/F: infection with neuropathic strain does not have to result in CNS disease
True
Neuro attack rate varies between outbreaks: factors influence this like immunity, age, infectious dose, breed
50
Younger horses are more likely to get what presentation of EHV 1?
Respiratory disease over neuro disease
Older horses would get neuro disease more over resp disease
51
How do you diagnose EHV-1?
- whole blood sample: PCR, virus isolation (best sample to take when viremic)
- tissue sample: PCR, virus isolation
- serum sample: serology
- nasal swab: PCR, virus isolation (best test to do when there is just infection in the nasal area)
52
Why is a serum sample for EHV-1 diagnosis not useful?
The virus is IN THE CELLS, and thus a serum sample would not be useful in this case. Need a whole blood sample, or have lab do Buffy coat
53
Herpes is associated with what types of fevers?
Bi-phasic fevers: once the virus becomes viremic, see a fever again
54
Why do you want to sample an aborted fetus for EHV-1?
Tissues are full of virus! Very easy to find virus within aborted fetal tissue or placental tissue
Consequence: contamination and biosecurity! If you have an abortion happening, you have a lot of environmental contamination happening and need to be careful.
55
T/F: fetal tissues are less useful for EHV-1 diagnosis
False- they are VERY useful and full of virus. BUT need to be careful about contamination and spread and biosecurity!!
56
If you are doing serology on a possible EHV1 horse and the titer comes back positive, what is the reporting process? What are the downsides of serology on these horses?
Lab has to report, and state vet will find out. But if horse has had exposure or has been vaccinated, then it will show up positive. So the single diagnostic test is kinda pointless unless you are doing the acute and convalescent test and showing that the horse has seroconverted.
57
Husbandry of EHV-1/4
Difficult to prevent taking virus onto a property because you could have a latent carrier. Difficult to control this
Separate pregnant mares and young populations to reduce spread of virus from different populations (ie trailers and shows are instances where reactivation is likely; isolate the pregnant horses from the horses that travel!)
58
EHV-1/4 vaccination
- bit of a conundrum: technically 2 vax available for EHV1. Majority are killed vaccines, but MLV available
- problem: neither one induces a long lasting immunity (neither does natural infx), so length of duration is problem, but also type of immunity is a problem
- the virus is inside the cells: the virus is not easily attacked by antibodies, so what we want to induce is a CTL response. Neither of these vaccines are good at inducing that kind of response
- neither vaccine on the market will claim that they can protect the horses from neuro disease because they cant; neither vaccine induces good enough immunity
Why vaccinate? They can reduce the chances (if have good enough immunity at mucosal surfaces) that the horse will eat infected and reduce the amount that is being shed at the nasal surfaces
59
T/F: vaccination of EHV1 does not protect against neurological disease
True. No vaccine can claim this
Some chance that it will protect against abortion though; don’t really know why tho
If horse populations have been vaccinated with high titered vaccines, abortion rates have decreased
60
Antivirals for EHV 1?
Yes they exist- used esp in horses with neuro disease. Research not super solid though. May reduce signs, but other studies show that it’s not super useful. Dr landolt doesnt use antiviral drugs, esp in a horse that already has neurological disease.
Plus they aren’t cheap and can cause nasty side effects like kidney disease. Need to ask if they are worth being used
61
When should you isolate horses when you are dealing with an EHV outbreak?
Isolation for 28 days after last new infection. Spread primarily thru contact, limited aerosol spread
62
How is EHV spread primarily?
Spread primarily thru contact, has limited aerosol spread
63
Vaccine details with EHV-1
- short lived immune response
- inactivated EHV 1 vax: reduce shedding, reduce abortions, protect from resp disease
- modified live: cytotoxic T cell response?
- no vaccine protects against neuro disease!!!
64
EHV-1 is a ___________ in Colorado
Reportable disease!!
65
T/F: EHV-1 cases with abortion signs is reportable
False. EHV-1 is reportable no matter what, but some vets will say it only matters when there is neuro signs so need to be careful. Often state vet won’t care until it is neuro signs; then they will take over
State vet or other control agencies will dictate quarantine and biosecurity protocols
66
What sequelae does EHV-1 cause?
Respiratory, neonatal, and neurologic disease and abortion
67
T/F: vaccination for EHV-1 may protect from infection and reduces shedding but does NOT protect from neurologic disease
True
68
Equine influenza is in what viral family?
Orthomyxoviridae
69
Equine influenza
- orthomyxoviridae
- H3N8 (equine-2)
- H7N7 (equine-1)
The 1 + 2 is an old designation^
- most of the time is just referred to as H3N8 and H7N7
- H7N7 has mostly disappeared from equine population , but some serology can be positive (ie virus circulating at low levels)
70
What is the primary equine influenza agent?
H3N8
H7N7 not usually included in vaccines anymore. Both subtypes of H3N8 will be included in the vaccine
71
T/F: equine influenza viruses change over time like human ones
True; has antigenic drift, but not as fast as humans. (Ie in humans the vaccine is new every year)
In horses, these vaccines were updated in 2008 but since then haven’t had much of an update bc the drift of equine influenza is a lot slower than drift in human influenza.
72
Clinical signs of equine influenza
Fever, lethargic, anorexia, serous nasal discharge, lymphadenopathy, cough
Can affect multiple horses
In contrast to herpes, influenza causes a COUGH!
73
If you have a horse with a severe cough and you think it is respiratory disease, you have equine herpes and equine influenza come to mind. Which is most likely to be the cause?
Equine influenza: causes a severe cough that can persist for a long time in contrast to herpes which doesnt causes a severe cough
This spreads very easily!! Can spread to susceptible horses very easily
74
influenza transmission
- efficient replication of virus in airways
- efficiently spread thru direct contact, fomites, resp droplets, aerosols
75
difference between aerosols and droplets
droplets are very large and thus don't travel very far, whereas aerosols are very small: less than 5 micrometers and stay in the air for a long period of time
76
equine influenza has a high morbidity but a low mortality. what are complications of equine influenza?
bacterial pneumonia, myocarditis
77
what is the most common complication of equine influenza?
bacterial pneumonia
78
pathogenesis of equine influenza
- replicates in respiratory epithelial cells
- influenza infects airway tissue
- airway cells are damaged = loss of cilia function (which clears resp tract)
- reduced airway clearance can result in bacterial bronchopneumonia
79
diagnosis of equine influenza
- nasal swab sample: PCR, virus isolation, etc if acute infx and showing resp disease
- once horse has mounted an immune response, can look for antibodies using serology and look for seroconversion
80
does equine influenza cause viremia?
no, whole blood will be useless
81
control of equine influenza
1. husbandry: can prevent it from coming in by quarantine, esp horses that have traveled.
- probably also want to separate resident horses, travel horses, etc
- horses that travel once a year should be quarantined upon their return
2. vaccination: in contrast to herpes, flu vaccines are good vaccines. not great at long lasting immunity so a lot of people with show horses will vaccinate twice yearly
- vaccine prevents well against clinical disease and virus shedding
3. anti viral drugs: hardly ever an indication to use them because the virus doesn't really kill the animal so these drugs are not really warranted.
82
when should you isolate an equine influenza patient?
21 days after last new infection: very efficient spread by droplets (up to 50 yards)
without testing do this, if you do targeted testing can shorted the isolation period tho
83
inactivated vaccination for equine influenza factors
- quantity and quality depends on the viral antigen quality and quantity
- virus strain
- adjuvants
- protects against homologous virus
- want to do 3 initial vaccine administrations
84
MLV for equine influenza factors
- very good vaccine, induces good mucosal immunity in the resp tract
- cold-adapted
- single dose: useful!
- protects up to 12 months
- induces immunity pretty quickly, even after 6 days have a reasonable amount of immunity already induced: good for outbreaks
struggles to show its efficacy against antibody induction because it doesnt demonstrate a strong systemic ab response
85
recombinant vaccine equine vax
- canarypox vector
- protected against challenge with recent isolates
86
what virus can stay viable for years even at subfreezing temperatures (cryopreserved semen)
equine viral arteritis virus
87
clinical signs of EVA
fever, lethargy, anorexia, serous nasal discharge, lymphadenopathy, cough
pink eye, photophobia, nasal dc, ocular dc
whole body vasculitis: skin rash around head and neck, ventral edema, lower limbs, scrotum, mammary glands
88
what are unique signs of EVA in addition to resp signs?
pink eye, photophobia, nasal dc, ocular dc
whole body vasculitis: skin rash around head and neck, ventral edema, lower limbs, scrotum, mammary glands
89
if you have a horse that has a fever with significant edema, what should be on your list of ddx?
EVA!!! if it looks like general vasculitis need to think about EVA
90
T/F: EVA is reportable
true!!
91
abortion of EVA
- exposure of mares >3 months pregnant to EVA may lead to abortion
- abortion occurs 1-3 weeks after viral exposure
- abortion rates may range from 10-70%. strain dependent, so some strains have high rates and some have low
92
neonatal foals with EVA?
- foals infected with EVA in utero may die within 2-4 days after birth due to severe progressive interstitial pneumonia or enteritis
quite fatal!
93
T/F: EVA is very fatal to neonatal foals
true. in contrast to herpes where it is debated
94
epidemiology of EVA
cyropreserved semen is vehicle for it to travel. can also shed thru nasal secretions
- in most cases, virus typically introduced thru semen of a carrier stallion
- virus reservoir: stallion!! maintains infx and ends up in repro tract/testicle and maintained within the testicular tissue of the stallion even after virus has been cleared from the rest of the body.
- stallion breeds mare, gets infected, develops respiratory signs and others, sheds virus in nasal secretions, and now that virus thru nasal shedding can spread to population
- if pregnant mare gets infected, it can result in abortion
- new stallion infected can result in carrier stallion state
95
what is the virus reservoir for EVA and thus the primary focus for control?
carrier stallion
maintains infx and ends up in repro tract/testicle and maintained within the testicular tissue of the stallion even after virus has been cleared from the rest of the body.
96
persistence of EVA is _______ dependent
testosterone-dependent
97
carrier stallion of EVA
- possible short term infertility due to increased temp and scrotal edema
- subsequent fertility not impaired
- virus may localize in accessory sex glands
- carrier state is a testosterone dependent condition
- won't know if the stallion is positive unless you do testing!!
98
how do you diagnose EVA?
1. nasal swab: acute phase when virus shed thru secretions
2. whole blood in viremic phase
3. tissue sample: aborted mare
4. serum sample: look for antibodies after acute infx has passed
5. semen: look for infection in carrier stallion
99
T/F: EVA becomes viremic
true! in contrast to herpes that is cell-associated, EVA is not cell-associated. this is useful for testing reasons! can use blood samples
100
T/F: EVA is cell-associated just like herpes is
false. herpes is cell associated, EVA is not
101
what is 1 way to identify carrier stallions?
some countries will accept testing semen directly, but some countries will do test breeding
- good way to look for carrier stallion
- test breed a stallion to 2 sero negative mares, and follow the mares serologically and if they sero convert, then the stallion was positive for EVA. acceptable way to go about testing for carriers
102
vaccination of stallions with EVA
- if stallion ends up being seropositive after vaccinated, some countries will say that that horse and semen cannot be shipped (some countries will refuse this from a seropositive animal) without additional testing
-
103
what is test breeding?
way to test for a carrier stallion for EVA:
test breed a stallion to 2 sero negative mares, and follow the mares serologically and if they sero convert, then the stallion was positive for EVA. acceptable way to go about testing for carriers
104
before vaccinating a stallion for EVA, you should
consult with state vet!!
105
T/F: EVA is a reportable disease in colorado
true
state vet will dictate quarantine and biosecurity measures
