Rhabdoviridae and retroviridae

Question 1

Rhabdoviridae

Answer 1

-ssRNA

replicate in cytoplasm

Question 2

Rhabdovirus: Lyssavirus

Answer 2

• Rabies virus

- Australian bat lyssavirus

Question 3

Rabies pathogenesis

Answer 3

• transmitted by bites of infected animal
• bats act as reservoir host
• aerosols in caves where bats roost
• contamination of scratches, abrasions, open wounds or mucous membranes w saliva of infected animal
• saliva has lots of virus
• local replication in muscles–> specific resceptors for neurotransmitters–> virus entrry into nerve and travels to CNS
• released at axon terminals where it can infect non-nervous tissues such as salivary glands

Question 4

Rabies prevention and control

Answer 4

• quarantine and vaccination
• avoid contact w unfamiliar animals
• desex

Question 5

Bovine ephemeral fever

Answer 5

• 3 day sickness

- arthropod- borne viral disease of cattle

Question 6

Bovine ephemeral fever epidemiology

Answer 6

• transmission through mosquitoes and midges

- after rainfall

Question 7

Bovine ephemeral fever pathogenesis

Answer 7

• blood sucking insects acquire virus when feeding on infected animals
• virus multilplies in vector, shed in saliva, transmitted to host during feed
• virus effects endothelium of small blood vessels
• systemic inflammatory response

Question 8

Bovine ephemeral fever Diagnoses

Answer 8

• clinical signs

- ELISA

Question 9

Control Bovine ephemeral fever

Answer 9

• vector control
• vaccination
• restrict movement of cattle

Question 10

Retroviridae

Answer 10

+ ss RNA (diploid)

Question 11

Unique properties of retroviruses

Answer 11

• RNA in this virus is not used as mRNA but is transcribed by reverse transcriptase –> copy DNA
• cDNA is inserted into host genome by integrase function of RT enzyme
• retroviruses are RNA viruses that incorporate their genome into the host genome by cDNA

Question 12

How do retroviruses cause cancer?

Answer 12

• rapidly transforming retroviruses may contain viral oncogenes

Question 13

TAX and REX gene

Answer 13

Bovine leukaemia has regulatory genes called TAX and REX that may disrupt the regulatory growth pathways and lead to neoplasia

Question 14

Avian leukosis virus (ALV) group

Answer 14

• tumour in birds

- transmitted vertical and horizontal; close contact ,saliva, faeces

Question 15

Bovine leukaemia virus (BLV)

Answer 15

• transfer of blood or secretions (colostrum/milk) containing lymphocytes; horizontal or vertical direct transmission
• biting flies

Question 16

Feline Immunodeficiency Virus

Answer 16

• bites from infected cat
• blood; transfusion
• vertical; milk from FIV queen