Fraser Menzies Veterinary Epidemiology Unit DARD Photos from: http://www.50pluslife.com/2015/08/04/highly-pathogenic-avian-influenza-what-does-it-mean-for-city-dwellers/
HPAI Avian flu outbreaks in domestic poultry during last 12 months LPAI
Orthromyxovirus virus family Influenza A Influenza B Influenza C Infects birds and mammals Responsible for all flu pandemics Influenza A magnified 100,000 times Photo from: http://www.doc.govt.nz/nature/pests-and-threats/wildlife-health/nz-wildlife-diseases/
Subtype defined by their H (haemagglutinin) and N (neuraminidase) For example: Influenza H5N1 Influenza H7N7 Influenza A H and N are proteins on the surface of the virus H important in gaining entry to the host cells and hence in causing infection/disease Adapted from: http://www.historyofnimr.org.uk/mill-hill-essays/essays-yearly-volumes/2010-2/the-2009-h1n1-swine-flupandemic-dont-panic-but-you-are-all-going-to-die/
All subtypes found in birds, particularly aquatic birds (wildfowl) H1 H2 H3 H4 H5 H6 H7 H8 H9...... H16 Main human flu subtypes Haemagglutinin (H) H5 and H7 are the only subtypes that cause highly pathogenic avian influenza. Only ones you have to worry about (to date anyway!)
N1 N2 N3 N4 N5 N6 N7 N8 N9 Neuraminidase (N) 9 different Ns Can get any combination of H and N H that is important, not the N Unless it is highly pathogenic avian influenza H5N1! H1N1 H2N1 H3N1.... H16N1 H1N9 H2N9.. H16N9 H1N1 H1N2 H1N3.... H1N9
HPAI and LPAI HPAI = highly pathogenic avian influenza = severe disease LPAI = low pathogenic avian influenza = mild or subclinical disease Difference caused by the H and its ability to invade to host cells in different organs BUT you do get HPAI and LPAI within the same subtype e.g. LPAI H7N7 and HPAI H7N7 In poultry, flu virus often enters as LPAI and switches to HPAI after a period of time
HPAI versus LPAI HPAI: all systems affected -Depression -Coughing/sneezing/diarrhoea -Loss of appetite -Egg laying stops -Nervous signs -Swelling and blue colour in head and neck (comb/wattles) -Sudden death -HIGH MORTALITY LPAI: respiratory/gut only -Mild respiratory disease -Depression -Drop in egg production -Subclinical: may only see changes in water and feed consumption +/- slight egg drop Domestic poultry
Differential diagnosis for HPAI Newcastle Disease Infectious Bronchitis (IB) Infectious Laryngotracheitis (ILT) Mareks Disease (MD) Avian Encephalomyelitis (AE) Infections with Avian Pneumovirus 1: Turkey Rhinotracheitis (TRT), Swollen head syndrome (SHS) Acute Fowl Cholera Heat exhaustion Water deprivation Some toxins
LPAI/HPAI sources Natural cycle within wild water fowl (ducks & geese) No obvious clinical effect on natural hosts Large amounts of virus excreted in faeces/droppings Infected by ingestion (faecal-oral transmission cycle) Virus survives for long periods in water especially when protected from sunlight by mud or vegetation e.g. wader bird environment ideal
Major flyways for migratory wildfowl along with main sources of winter migration (shown in red) Migrations allow for mixing of different species from different locations This includes mixing of migratory birds with local waterfowl
Wintering Waterbird populations Northern Ireland s key sites Mean pop 2009/10 2013/14 = 257900 (total waterbirds) higher turnover populations Lough Foyle 34300 Larne Lough 7700 Belfast Lough 23800 Lough Neagh and Beg 46400 Outer Ards 15600 Upper Lough Erne 7350 Carlingford Lough 6750 Dundrum Inner Bay 11600 Strangford Lough 70100 Source: I Enlander, NIEA
Wintering and staging grounds have high densities of mixed species (breeding season low density) Infect local wild birds Risk from infected droppings (tramp into poultry house) >1 million birds winter in Ireland
Avian influenza outbreaks in poultry Numerous experiences have shown that: Primary source of infection is from wild birds - direct contact - indirect (infection brought into poultry house) Secondary spread amongst other flocks by fomites - contaminated people or equipment Good biosecurity critical - limit access to birds - Cleanse then disinfect Applies to prevention of nearly all infectious diseases
Highest risk Lower risk Infection risk gradient Bird to bird contact Anything entering the poultry house Area immediately surrounding the house The rest of the farm yard Visitors to the farm house Increasing biosecurity focus
Time window for virus spread Potential period for onward transmission of LPAI/HPAI to other producers Worst case scenario - 21 days+ Best case scenario - 3 days Even best case scenario - at least one egg collection from site Days / Weeks / Months LPAI/HPAI infects flock Suspect reported Disease confirmed Clinical signs/production changes Veterinary Investigation
Prompt eradication of avian influenza depends on: Early detection of the infection Rapid destruction of infected birds Good biosecurity to prevent further spread
Prompt eradication of avian influenza depends on: Early detection of the infection Rapid destruction of infected birds Good biosecurity to prevent further spread YOU DARD YOU/DARD
Good biosecurity House entrance is a critical control point Physical separation of dirty and clean sides Dedicated foot wear for use in the house
Cleanse then disinfect
History of HPAI Was known as fowl plague First recognised in USA in 1924-25 Regular classical outbreaks around the world LPAI H5/H7 infections mutating to HPAI outbreaks HPAI H5N1 - surfaced in South East Asia in 2003 - circulating as HPAI in wild birds and causing disease in them - infection and deaths in humans - Spread west through Europe and Africa - Still circulating in Asia
HPAI H5N1 distribution in Jan-Jun 2006 Spread partly wild birds partly domestic bird movements
Human infections HPAI H5N1 (400+ deaths) LPAI H7N9 (300 deaths) HPAI H7N7 (some deaths) Requires close bird contact Live bird markets No human-human transmission Several mutations before adapted to humans
HINI 2009 pandemic Flu viruses are messy at reproducing themselves mistakes = mutations = antigenic drift Infection with more than one flu virus at a time swapping of genetic material = reassortment = antigen shift Previous triple assortment (bird/human/pig) with a new pig strain added. Little immunity from previous flu vaccines resulted in the pandemic Evidence of spread from humans to pigs Vet. Record (2010) 166, 642
The H7N9 Reassortment Example Source = Eurosurveillance https://flutrackers.com/forum/forum/welcome-to-the-scientific-library/h7n9-research-studies-papersacademia/160229-euro-surveill-possible-pandemic-threat-from-new-reassortment-of-influenza-a-h7n9-virusin-china
Influenza: One health approach Medics: Public Health Medics: Lab based Ornithologists Annual flu NI stakeholder meeting Vets: Epidemiology Vets: Lab based International organisations World Health Organisation (WHO) World Health Organisation for Animal Health (OIE)
Summary Widespread low levels of flu viruses naturally circulating in wild fowl Migratory wild birds pose a threat Continuous ongoing risk from direct/indirect contact with wild birds Good biosecurity practices and vigilance are the best protection Human flu epidemics can be occur through exchange of genetic material between flu viruses Sporadic human cases of avian flu do occur but no human-to-human transmission has occurred