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VMS 2004 > Retroviruses > Flashcards

Retroviruses Flashcards

1
Q

What is the classification of retroviruses?

A
  • RNA genome
  • Icosahedral capsids
  • Enveloped (inactivated by solvents, detergents and heat)
  • More resistant to UV
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1
Q

Name 4 common characteristics of retroviruses

A
  1. Infect wide range of mammals
  2. Host adapted and rarely cross host barriers
  3. Diseases induced by retroviruses are diverse and have distinct pathogenic mechanisms
  4. They integrate into the host cell genome (activate specific genes)
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2
Q

Name 4 characteristics of Alpharetroviruses

A
  • Tumour forming
  • Very well studied
  • Need to have an understanding of tumour cell biology
  • Oncogene discovery
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3
Q

What is Jaagskiekte sheep retrovirus responsible for in sheep?

A

It is responsible for contagious lung tumours
(ovine pulmonary adenocarcinoma)

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4
Q

How is Jaagskiekte transmissed?

A

Via aerosol spread

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5
Q

What are the main symptoms of Jaagsiekte sheep retrovirus?

A

The symptoms are similiar to pneumonia
General loss of condition and breathing difficulties
* watery discharge from the nose

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6
Q

What clinical sign is unique to OPA?

A

over-production of fluid in the lungs

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7
Q

What are sheep affected by OPA invariably more susceptible to?

A

other types of pneumonia, particularly pasteurelliosis

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8
Q

What cells does EBL target?

A

Targets B cells
* the clonal expansion and accumulation of B cells creates tumours

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9
Q

How is EBL mainly transmissed?

Give 3 ways

A
  • mainly via milk to calves from dams
  • Can be iatrogenic
  • Mechanical transfer from biting insects
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10
Q

What are the usual post mortem findings for EBL?

A
  • Abomsal tumours that may result in diffuse thickening of the mucosa and sub-mucosa with associated ulceration and haemorrhage
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11
Q

What may you see in the EBL serology?

A
  • AGIDT on single sera.
  • ELISA on serum on single and pooled sera.
  • ELISA on single and bulk milk.
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12
Q

What is equine infectious anaemia also known as

A

Swamp Fever

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13
Q

Where does equine infectious anaemia have increased prevalence?

A

Warm humid environments

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14
Q

How is EIA transmissed iatrogenically?

A
  • Re-using needles
  • Blood/ Plasma donation to young foals
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15
Q

How is EIA transmissed mechanically?

A
  • Via biting insects, such as horseflies and deerflies
16
Q

What does it mean when we say that retroviruses rarely cross host barriers?

A

Typically only affects one species or closely related species

Retroviruses typically affect mammals

17
Q

What is the capsid shape of retroviruses?

A

Icosahedral

18
Q

What sense is the RNA?

A
  • Positive sense
  • BUT contains reverse transcriptase
  • this means it can convert into DNA to integrate into the host cell
19
Q

How many copies of the RNA genome are there?

A

two copies

20
Q

What is the meaning of the retrovirus being enveloped?

A
  • Inactivated by solvents, detergents and heat
  • More resistant to UV
21
Q

When provirus DNA enters the cell where is it integrated into the host genome?

A

In areas of active transcription

22
Q

What is the function of Gag and Gag-Pol Polyproteins?

A

Polyproteins that are responsible for synthesising a new virus

23
Q

What do sheep with OPA not respond to?

A

Antibiotics

24
Q

How many sheep are invariably lost to OPA?

A
  • Affected flocks may lose 1-5% sheep per annum
  • More than 20% in some cases
25
Q

What should you do if you have a sheep flock with recurring pneumonia?

A

They should be investigated so you can determine if OPA is an underlying factor

26
Q

What are the three main clinical signs of EBL?

A
  1. Neurological manifestations
  2. weakness/ general debility
  3. inappetence/ weight loss
27
Q

How much may the milk production reduce in a cow with EBL?

A

2.5%

28
Q

What may you see in the serology of EBL?

A
  • AGIDT in single sera
  • ELISA on serum in single and pooled sera
  • ELISA on single and bulk milk
29
Q

What are lentiviruses characterised by?

A

Retroviruses that are characterised by their ability to evade the immune system and have long incubation periods

30
Q

What are the clinical signs of acute EIA?

A
  • lethargy, anaemia, pyrexia, thrombocytopenia, emaciation
31
Q

What are the clinical signs of EIA when they are in the ‘inapparanet carrier state’

A
  • Asymptomatic due to strong immune control
32
Q

How quickly may horses with acute EIA die?

A

may die within 2-3 weeks

33
Q

What are the main clinical signs of chronic/ recurring EIA?

A
  1. Fever- generally around 40.5
  2. Depression- generally listless
  3. Wasting away
  4. Blood shows a marked drop in RBC count
  5. Oedema- horses may show swelling under the skin in legs and chest
34
Q

What do over 90% of EIA infected horses look like?

A
  • No overt clinical abnormalities
  • they survive as reservoirs of infection
  • have dramatically lower concentrations of EIAV
35
Q

What is considered to be the ‘gold-standard’ test for EIA?

A

the AGID test

uses serum to detect antibodies

36
Q

Where do retroviruses replicate within the cell?

A

They begin replication in the cytoplasm,- then pro-virus integrates into the host genome and replication continues within the nucleus

37
Q

How do the retroviruses replicate (simply)

A
  1. Single stranded RNA enters the cytoplasm
  2. Converted into DNA
  3. DNA integrates into the host genome in the areas of active transcription
  4. Provirus DNA is used to produce mRNA
  5. mRNA enters the cytoplasm and is used as a template to produce proteins and virions
38
Q

What are the four main methods of EIA transmission?

A
  • Iatrogenic (needles)
  • Mechanical (flies)
  • Aersols
  • Vertical (in-utero/ milk)

VMS 2004 (34 decks)

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