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Diseases of Food Animals > Introduction to Viruses of Food Animals > Flashcards

Introduction to Viruses of Food Animals Flashcards

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1
Q

how do foreign avian viruses enter the US?

A

primarily migration of wild infected birds, importation, and carried in feed

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2
Q

why are backyard flocks a problem for commercial poultry farms?

A

there is not as much regulation for backyard flocks which could introduce disease to commercial poultry populations that have good biosecurity programs

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3
Q

virus defintion

A

a small micro-organism comprising nucleic acid and a protein coat that only replicates in living intact cells of other organisms

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4
Q

viruses have a ______ relationship with their hosts

A

parasitic

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5
Q

virus nucleic acid

A

DNA or RNA

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6
Q

virus structure

A

nucleic acid with protein capsid and sometimes a lipid envelope

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7
Q

virus size

A

much smaller than bacteria, 1000 x smaller, 20 nanometers to 0.3 microns

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8
Q

viruses cause many important diseases of food animals including

A

bovine viral diarrhea, herpesvirus, rabies, avain influenza

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9
Q

viruses also cause zoonotic diseases including

A

rabies and orf

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10
Q

rabies zoonoses

A

rarely contracted from food animals, most commonly contracted from bat bites

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11
Q

orf

A

infection in newborn goats and lambs from parapox

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12
Q

avian influenza zoonoses

A

caused by virus and could lead to potential human pandemic

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13
Q

many viral diseases are reportable and/or foreign animal diseases

A

regulated federally or at the state level

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14
Q

reportable viral diseases include

A

rabies and vesicular stomatitis

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15
Q

foreign animal viral diseases include

A

foot and mouth disease, virulent avian influenza, virulent newcastle disease, hog cholera

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16
Q

most viruses have a _____ host range than bacteria

A

narrower

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17
Q

PRRS virus host range

A

only pigs, host restricted

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18
Q

rabies host range

A

all mammals, large host range

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19
Q

ovine herpes virus 2 (OHV2) host range

A

sheep carry silent infection but can cause severe disease in cattle and bison

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20
Q

virion structure: naked

A

non-enveloped viruses are generally hardier and persist longer in the environment

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21
Q

virion structure: enveloped

A

enveloped viruses are generally more susceptible to disinfectants that melt membranes

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22
Q

viral classification factors

A

RNA or DNA, shape, enveloped or non-enveloped, single or double stranded, positive or negative sense

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23
Q

why is virus classification and structure important?

A

for controlling and preventing disease

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24
Q

virus transmission types

A

horizontal and vertical

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25
Q

horizontal transmission

A

animal to animal

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26
Q

horizontal transmission routes

A

respiratory aerosols, feco-oral route, and direct contact

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27
Q

vertical transmission

A

mother to fetus

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28
Q

vertical transmission routes

A

mother to fetus or mother to newborne via milk

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29
Q

why is it important to know viral transmission routes?

A

for prevention and control of viral disease

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30
Q

what does the lytic replication cycle cause?

A

acute disease

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31
Q

lytic cycle pathway

A

virus enters into cell, hijacks host machinery to replicate, causes cell damage and virion release to infect other cells, causes tissue damage and disease

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32
Q

the lytic cycle is important in acute viral infections including

A

BRSV, rotavirus, coronavirus, rabies, acute BVD

33
Q

if the animal survives virus is usually cleared from the body

A

true

34
Q

latent infections are formed from

A

herpesvirus

35
Q

acute infection

A

sudden onset and short duration

36
Q

latent infection

A

persistant and sub-clinical

37
Q

what does the lysogenic replication cause?

A

chronic and latent infections

38
Q

lysogenic replication cycle pathway

A

virus attatches to cell and penetrates to release nucleic acid, the nucleic acid gets integrated into host genome and the host cell divides to multiply the viral genome

39
Q

what disease is the lysogenic replication cycle important for?

A

chronic viral infections, diseases with long incubation periods, and latent infections like small ruminant lentivirus

40
Q

incubation period

A

time from infection to disease onset

41
Q

viruses have preference for replication in specific organs and cell types

A

true

42
Q

bovine respiratory syncytial virus replicates in which cells

A

lung airway cells to cause viral pneumonia

43
Q

bovine popular stomatitis virus replicates in what tissue

A

nose, oral cavity, and esophagus

44
Q

why is it important to know what organs and tissues viruses target?

A

important for understanding what tissues are damaged, what clinical signs may show, treatment and diagnosis

45
Q

why is it important to know how and how long viruses survive in the environment?

A

for biosecurity measures, control of the disease, and how to clear the environment

46
Q

robust viruses include

A

circovirus and parvovirus

47
Q

robust virus transmission

A

direct or distant contact transmission

48
Q

fragile viruses include

A

lentiviruses, influenza, porcine reproductive and respiratory syndrome

49
Q

fragile virus favorable environment

A

cold and moist conditions

50
Q

fragile virus transmission

A

direct or close contact transmission

51
Q

how are viral diseases diagnosed?

A

manifestation in specific organs and diagnostic testing

52
Q

clinical exam for diagnosis of viruses

A

organ system involved and consider bacterial or viral causes

53
Q

diagnostic confidence

A

some viruses can be identified with confidence, like orf causing inflammation of the lips, but most require laboratory testing to confirm a diagnosis

54
Q

samples needed for diagnosis of viral diseases

A

blood, secretions, excretions, and necropsy

55
Q

diagnostic sample: blood

A

direct virus detection or serology for antibodies

56
Q

diagnostic sample: secretions

A

used in live animals, nasal, oral, or ocular samples

57
Q

diagnostic sample: excretions

A

feces for suspect viral enteritis

58
Q

diagnostic sample: necropsy

A

tissues are often preferred over secretions and feces when the animal has died

59
Q

direct detection of virus

A

electron microscopy, PCR, fluorescent antibody test, virus isolation in cultured cells, viral metagenomics, serology for detection of antibodies

60
Q

electron microscope advantages

A

identify new viruses not specifically tested for, good for disease where large amounts of virus is produced

61
Q

virus where large amounts of virus is produced example

A

viral enteritis

62
Q

electron microscope disadvantages

A

low sensitivity and expensive

63
Q

most common cause of viral diarrhea in calves in the first few weeks of life

A

bovine rotavirus and bovine corona virus

64
Q

enveloped virus shape

A

flexible and variable in shape

65
Q

capsid virus shape

A

regular and geometric shape

66
Q

virus isolation in cell culture for disease diagnosis

A

clinical specimen is cleaned up to remove bacteria and dead cells, cytopathic effect is observed in cell culture

67
Q

cell culture advantages

A

grow intact virus and can use for future research and sequencing genomes

68
Q

cell culture disadvantages

A

takes 2-4 weeks, not all viruses cause cell death, low sensitivity, expensive, may grow zoonotic viruses

69
Q

fluorescent antibody testing for rabies virus

A

transfer brain sample to slide, add fluorescently labeled antibodies and observe under fluorescent light

70
Q

fluorescent antibody testing advantage

A

rapid turnaround, approx. 2 hours

71
Q

detection of viral DNA or RNA through polymerase chain reaction

A

dependent on DNA primers binding directly to nucleic acids, amplification of target DNA is specific to the microbes being tested

72
Q

PCR advantages

A

very sensitive, specific, quick, and cheap

73
Q

PCR disadvantages

A

false negative results due to viral mutagenesis, variation in viruses can bind to primers, RNA viruses are highly variable, some PCR cannot detect all strains, and prone to false positives due to contamination

74
Q

how is PCR used for diagnosis of viral diseases?

A

clinical specimen, nucleic acid extraction, if RNA it is reverse transcribed into cDNA, if DNA it is directly amplified by PCR and amplified DNA is detected

75
Q

why is viral metagenomics important?

A

searching for novel viruses when a novel virus is suspected, tracking viral strains during outbreaks, and sequencing genomes of isolates to see which vaccines to use

76
Q

co-infections are very common in food animals including

A

calf diarrhea: rota or corona virus and E. coli
bovine pneumonia: BRSV and pasteurella multocida/mannheimia hemolytica
bovine pneumonia: BVD and pasteurella multocida/mannheimia hemolytica
procine circovirus disease: mainests with co-infection

77
Q

why is synergism important for co-infection?

A

results in more severe disease and increased mortality rates, important for management and control

78
Q

what should be used in cases of concurrent bacterial infection?

A

antibiotics

Diseases of Food Animals (6 decks)

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