Retroviruses

Question 1

Retrovirus distinct pathogenic mechanisms ?

Answer 1

inflammation
neurodegeneration
immunodeficiency
cellular transformation (neoplasia)

they integrate into the host cell genome and activate / inactivate specific genes

Question 2

Structure ?

Answer 2

(+) ssRNA
enveloped
gag/pol/env basic structure (made of envelope proteins, polymerase enzymes and other structural proteins)
potential for accessory proteins

Question 3

Replication cycle ?

Answer 3

in the cytoplasm (RNA)
RdDp enzyme needed
makes pro-virus dsDNA and integrates into the host cell genome, where replication can continue in the nucleus

Question 4

What are the most important retroviruses ?

Answer 4

Jaagsiekta Sheep Retrovirus (ovine pulmonary adenocarcinoma, OPA)
Enzootic Bovine Leukosis (EBL)
Equine Infectious Anaemia (EIA), “swamp fever”

Question 5

OPA clinical signs

Answer 5

similar to pneumonia
over-production of fluid in the lungs
watery discharge from the nose
invariably fatal

Question 6

OPA diagnosis, treatment and control

Answer 6

diagnosis = PCR, no specific assay
treatment = none. do not respond to antibiotics
control = no vaccine, remove affected sheep and replace

Question 7

EBL pathogenesis

Answer 7

targets B-cells, starting with leukosis and occasionally progressing to lymphosarcoma

Question 8

EBL transmission

Answer 8

milk
iatrogenic
biting insects

Question 9

EBL clinical signs

Answer 9

60% asymptomatic
30% develop persistent lymphocytosis
signs will depend on site of tumours
- digestive disturbances
- weakness
- neuro
milk drop
enlarged and palpable LNs

Question 10

EBL gross findings

Answer 10

abomasal ulcers
abomasal tumours
heart tumours

Question 11

EBL diagnosis

Answer 11

serology through milk or blood (ELISA)
PCR on whole blood tumours
tumour histology

Question 12

EIA transmission

Answer 12

classic bloodborne infection
iatrogenic
biting insects
aerosol
vertical

Question 13

EIA Clinical signs

Answer 13

acute disease : lethargy, anaemia, pyrexia, thrombocytopenia, emaciation, quick onset so often missed
chronic disease : fever, depression, listlessness, weight loss, anaemia, oedema
inapparent carrier state : 90% of horses in this state. asymptomatic act as reservoirs

Question 14

EIA diagnosis

Answer 14

AGID test is gold standard
- agar gel immunodiffusion assay
- uses serum and detects antibodies
ELISAs and PCRs available

Question 15

EIA control

Answer 15

test and slaughter been seen successfully
be in control of insect vectors