Poultry Infectious Diseases

Question 1

What is antigenic shift

Answer 1

glycoprotein reassortment

Question 2

What is antigenic drift

Answer 2

glycoprotein point mutation

Question 3

What are the two notifiable diseases of poultry

Answer 3

Avian influenza

Newcastle disease

Question 4

Describe the general features of Newcastle disease

Answer 4

paramyxovirus
enveloped RNA virus with surfce protein spikes - H, N and F
Is capable of antigenic drift but not shift
Does not have a segmented genome
Has a helical nucleocaspid
causes respiratory, enteric and neurological signs
vaccine available for prevention

Question 5

What are the 5 presentations of Newcastle virus

Answer 5

• Lentogenic - mild, respiratory tract infection
• Mesogenic - respiratory and neurological signs, low mortality
• Neurotropic - respiratory and neurological signs, gut lesions absent, high mortality
• Asymptomatic enteric - avirulent infection, primary replication in the gut
• viscerotropic velogenic - acute, lethal gut haemorrhage

Question 6

Describe the clinical signs of Newcastle disease

Answer 6

General signs:

• appetite loss
• listlessness
• dehydration
• abnormal thirst
• dehydration
• emaciation
• ruffled feathers
• huddling
• depression

neurotropic signs:

• tremors
• star gazing
• twisted neck
• incoordination
• convulsions
• paralysis of wings and legs

viscerotropic signs:

• intestinal haemorrhage
• greeny-yellow diarrhoea
• lymphoid nodules

pneumotropic signs:

• rales
• sneezes and cough
• nasal discharge
• laboured breathing
• head shaking
• greeny yellow diarrhoea

Question 7

Describe the general features of Avian Influenza

Answer 7

• Type A is the one of concern
• enveloped RNA virus
• has H and N glycoprotein spikes
• capable of antigenic shift and drift
• has a helical nucleoplasmid and a segmented genome
• has a wild bird reservoir
• causes respiratory, neurological and enteric signs
• able to replicate in a wide range of tissues causing necrosis, congestion and haemorrhage

Question 8

Describe the clinical signs seen with Avian influenza

Answer 8

drop in egg production and loss of quality
respiratory distress
lack of appetite
diarrhoea
pasty vent
conjunctivitis
nasal disharge
coughing, sneezing and rales
dehydration
haemorrhage of skin and muscle

Question 9

Describe the transmission of avian influenza

Answer 9

spread via aerosol, excreted in faeces and respiratory secretions
egg shell can also be contaminated but no in-ovo transmission occurs
fomites and water sources aid spread
difficult to control, no available vaccine
free range birds at higher risk due to contact with wild birds

Question 10

What type of virus is chicken anaemia virus?

Answer 10

circovirus

Question 11

2. How is chicken anaemia virus transmitted?

Answer 11

Horizontal (chicken to chicken) via feather follicles and faeco-oral transmission and vertical (chicken to offspring/egg) also in semen

Question 12

What are the clinical signs of chicken anaemia virus?

Answer 12

Clinical signs: anorexia, pallor, anaemia, leukopenia, depression, lethargy, skin and muscle haemorrhage

Question 13

What organs does chicken anaemia virus target?

Answer 13

Thymus, bone marrow, spleen - causes atrophy and haemorrhage

Question 14

What can be used as control for viruses on poultry farms?

Answer 14

Vaccination (injection, water, spray, in-ovo), good nutrition, good ventilation, good hygiene, all in all out systems with a full clean between each batch, rodent and wild bird control, ensure food and water sources are uncontaminated, good biosecurity, good temperature control

Question 15

What type of virus causes Marek’s disease?

Answer 15

Oncogenic herpes virus – mardivirus

Question 16

Name the 4 manifestations of Marek’s disease

Answer 16

Ocular, cutaneous (tumours of the feather follicles), visceral (tumours of the heart, ovaries, muscles and lungs) and neurological (causes transient paralysis of legs and wings plus eye lesions)

Question 17

How is the Marek’s virus transmitted?

Answer 17

Virus excreted in feather follicles and inhaled

Question 18

How is Marek’s controlled?

Answer 18

Vaccine given at 1 day old

Question 19

What type of virus causes infectious bursal disease?

Answer 19

A non-enveloped, double stranded RNA virus

Question 20

How is IBD transmitted?

Answer 20

Faeco-oral transmission – very environmentally stable

Question 21

What is the pathogenesis of IBD?

Answer 21

Virus infects the thymus and attacks B cells reducing the number which also results in decreased number of plasma cells and a drop in antibody production resulting in body wide immunosuppression resulting in immune suppression and decreased response to vaccines

Question 22

What are the clinical signs of IBD?

Answer 22

Depression, ruffled feathers, vent pecking, dehydration, haemorrhage, bursal lesions

Question 23

Describe the general features of avian mycoplasmas

Answer 23

• look like fried egg colonies
• gram -ve bacteria
• Mycoplasma gallisepticum is respiratory
• mycoplasma synoviae is respiratory and causes arthritis
• mycoplasma meleagridis causes air sacculitis in turkeys

Question 24

Describe the general features of infectious bronchitis

Answer 24

• type 3 coronavirus
• affects chickens and game birds
• incredibly contagious
• affects food conversion ratio, growth and egg production and quality
• respiratory signs common but not always present
• if affected at a young age can cause abnormal oviduct development resulting in poor or no egg production , can also lead to egg peritonitis
• certain strains cause nephritis
• the virus can be isolated from eggs
• vaccine available

Question 25

Describe the general features of Avian Rhinotracheitis

Answer 25

• pneumovirus
• mainly affects turkeys and chickens - chickens have milder symptoms
• causes coughing, sneezing, nasal and ocular discharge, drop in egg production and poor egg quality (loss of shell) - egg peritonitis can occur
• disease can be complicated by Ecoli causing oedema of the head and in-coordination
• spread via mucous, aerosol, fomites and wild birds
• virus targets the epithelium of the trachea and turbinates then the oviduct epithelium after entering the blood stream
  live vaccine given to young birds and killed vaccine by injection before laying

Question 26

Describe the general features of salmonella enterica

Answer 26

• main types affecting poultry - typhimirium and gallinarium
• low clinical significance but is a public health risk
• vaccine available
• clinical signs: anorexia, dullness, dehydration, retarded growth, enteritis, septicaemia, inflammation of the kidneys, liver, intestines and spleen