Poultry Infectious Diseases Flashcards
What is antigenic shift
glycoprotein reassortment
What is antigenic drift
glycoprotein point mutation
What are the two notifiable diseases of poultry
Avian influenza
Newcastle disease
Describe the general features of Newcastle disease
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
What are the 5 presentations of Newcastle virus
- 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
Describe the clinical signs of Newcastle disease
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
Describe the general features of Avian Influenza
- 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
Describe the clinical signs seen with Avian influenza
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
Describe the transmission of avian influenza
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
What type of virus is chicken anaemia virus?
circovirus
- How is chicken anaemia virus transmitted?
Horizontal (chicken to chicken) via feather follicles and faeco-oral transmission and vertical (chicken to offspring/egg) also in semen
What are the clinical signs of chicken anaemia virus?
Clinical signs: anorexia, pallor, anaemia, leukopenia, depression, lethargy, skin and muscle haemorrhage
What organs does chicken anaemia virus target?
Thymus, bone marrow, spleen - causes atrophy and haemorrhage
What can be used as control for viruses on poultry farms?
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
What type of virus causes Marek’s disease?
Oncogenic herpes virus – mardivirus
Name the 4 manifestations of Marek’s disease
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)
How is the Marek’s virus transmitted?
Virus excreted in feather follicles and inhaled
How is Marek’s controlled?
Vaccine given at 1 day old
What type of virus causes infectious bursal disease?
A non-enveloped, double stranded RNA virus
How is IBD transmitted?
Faeco-oral transmission – very environmentally stable
What is the pathogenesis of IBD?
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
What are the clinical signs of IBD?
Depression, ruffled feathers, vent pecking, dehydration, haemorrhage, bursal lesions
Describe the general features of avian mycoplasmas
- 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
Describe the general features of infectious bronchitis
- 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
Describe the general features of Avian Rhinotracheitis
- 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
Describe the general features of salmonella enterica
- 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
