Retroviruses

summary

-helical nucleocapsid

-icosahedral capsid

-enveloped (acquired)

-v fragile in enviro

-cytoplasm replication

transmission

general

-close contact

-transfer of body fluids

-general retrovirus

-general retrovirus

replication

-unique

-provirus inserted into host cell’s DNA

-provirus may stay transcriptionally silent for long periods (months/years)

-may continue to transcribe

endogenous

general

-transmitted horizontally

-if incorporated into germline DNA will be inherited

-ERVs are defective with no production of virus

-some can have beneficial effects in hosts

-ERVs can cause disease in:

• cats

• mice

• koalas

• humans

Abs

-can be used to detect viruses in individuals

-no enviro reservoir of virus

-

how do oncogenetic retroviruses produce tumors?

-virus effects cell oncogene (chronic transformation)

-virus posesses an oncogene (acute transformation)

oncoviruses:

chronic transformation

-provirus inserts nearest cellular proto-oncogene → increase unit expression

-slow oncogenesis → require requires chance event to occur

-not every animal will develop neoplastic change

oncoviruses:

Acute transformation

-directly oncogenic

v-onc usually displaced another viral gene → gene is defective and requires help (replication competent helper)

-not as common as chronic transformation

avian lymphoid leucosis

poultry

-horizontally and vertically (egg)

-if infected vertically or during first few days → persistent viremic but Ab neg

-if infected over 1 wk → can mount immune response, clear virus and no tumors

-low mortality rate

-⬇ egg production, hatchability

avian lymphoid leucosis

control

-no vx

-breed for resistance

Feline leukemia virus

Factors for outcomes

–age

– Dose of virus at time of infection

Feline and leukemia virus

Immunity

– Older cats, Mount immune response, and clear virus

– Young cats have been effective immune response → persistent viremia

Feline leukemia virus

Symptoms

– Lymphoid and myeloid leukemia

– Lymphosarcoma

– Bone marrow aplasia → anemia

– Immunosuppression

– Reproductive failure

– glomerulonephritis

– Osteosclerosis

Feline leukemia virus

Most common symptoms

– Lymphoid and myeloid leukemia

– Lymphosarcoma

– Anemia

– Immunosuppression

– Leukemic bone marrow

– Lymphosarcoma kidney

FeLV:

subgrps

A

B

C

T

FeLV:

subgrp A

-most common

-source of other subgrps

FeLV:

which subgrp is associated with tumors?

B

FeLV:

which subgrp is associated with anemia?

C

FeLV:

which subgrp is associated with immunodeficiency?

T

FeLV:

transmission

-shed in saliva, secretions/excretions

-high in multi cat households, catteries

FeLV:

dx

-need to detect persistent viremia (they are the ones who develop disease)

-Ag detected in blood

-ELISA, rapid Ag tests

-Ab test not useful because anyone exposed to virus will test (+)

FeLV:

Vx

-recombinant vx is available in Aus

-must test before vx

enzootic bovine leukosis

Summary

(EBL)

-persistent lymphocytosis in 30% of infected animals

-lymphosarcoma in 5% of infected animals

– Long incubation period, persistent infection

– Transmission: blood transferred between animals

– Insect of vectors can also transmit

– No vaccine

– Control programs: Ab testing

EBL

Dairy freedom program

– EBL has been eradicated from Australian Derry herds

– Objective: protect, enhance Australia's access to international export trade

– EBL free from December 31, 2012

– Continued bulk milk, monitoring called maintenance of freedom

– Any infections must be reported to state CVO's

– Annual EBL status report given to international trading partners

– Beef herds still have low levels of EBL

– Dairy herds must be separated from untested beef herds

lentiviruses

-slow progressive disease

– Transmission: close contact, transfer of body fluids

medi-visna virus

(ovine Progressive Pneumonia)

– Sheep and goats

– Incubation: 2 to 3 years

– Slow progressive pneumonia (maedi) → dyspnoea, wasting → death

– Slow demyelination (visna) → neurological signs, wasting → death

– Global except Australia: strict quarantine, virus fragility

Caprine arthritis encephalitis virus

CAEV

-goats

-transmission: colostrum

-in Aus

-symptoms: lesions in jts, brain, lungs, mammary glands

CAEV:

CAE scheme

-flock management

-2 neg blood tests of all goats over 6 mo for initial accreditation

-annual or biennial re-accreditation

-if infection occurus, loose accreditation until all reactor animals are removed from herd

-must meet all vet and lab costs, fee to Biosecurity QLD

Equine infectious anemia

EIA

– Symptoms: fever, anemia, abnormal, iron metabolism, increased, gammaglobulin levels, immunosuppression

– Acute death or recurrent episodes with progression

– North Australia

- transmission: biting arthropods

Feline immune deficiency virus

FIV

– Initial symptoms: fever, anemia, lymphadenopathy → eventual immunosuppression → secondary infections

– Long incubation period

– Transmission: biting/fighting (high prevalence and males)

– Killed vaccine available

– DX: antibodies in serum