Avian Influenza Animal Control and Vaccinations Dr. Pravit - PowerPoint PPT Presentation

Avian Influenza Animal Control and Vaccinations Dr. Pravit Choomkasien, DVM.

Learning Objectives 1. Control of Infected poultry • Process for culling • Safety of personnel • Chemical disinfection and sanitation measure 2. Vaccination for Prevention • Overview of AI Vaccine • Advantage and disadvantage of AI vaccination • Administration of AI Vaccine • Recommendation made when AI is detected in vaccinated flock

Culling Infected Animals

Planning for Culling When planning to AI disposed poultry, the following should be considered: – Minimising handling and movement of animals – Culling the animals on the affected premises – The species, number, age and size of animals to be culled, and legal issues involvement – Methods of culling the animals, and their cost – Destruction after culling – The health and safety of personnel conducting the culling (PPE) – The presence of other nearby premises holding animals.

Methods Used for culling of Poultry Method Use Dislocation of the neck Both large and small numbers of birds such as fancy breeds or pigeons Decapitation Small numbers of poultry conducted in an a defined area to prevent contamination Large numbers of birds such as Gaseous agents in poultry units Both large and small numbers of Put the live birds in the birds in areas where further without any treatment sags contamination will not occur Burning or Burying

Dislocation of the Neck (Un-humane culling) • Manual – one stretch or bend of the neck to sever spinal cord • Mechanical – pliers crush cervical vertebrae and cause damage to spinal cord – Depending upon the type of poultry, the following tools can be used: • Pliers • Burdizzo • Bone cutters • Secateurs (Not applicable)

Decapitation (Un-humane culling) • Animals should be restrained • Removal of the head should occur quickly, using a sharp blade or guillotine – Technique is quick and easy – Death is not immediate – Blood may contaminate area and therefore proper disinfection is needed (Not applicable)

Carbon Dioxide Gas (Humane culling) 1. Place in air-filled container – 30% = loss of consciousness – At least 3 minutes 2. Remove after unconsciouness – Cervical dislocation or exsanguination 3. Exposure for 20-30 minutes – Death in neonatal or juevenile – Can be filled in advance to accelerate anesthesia 4. If no CO 2 available, use dry ice – Placed in container, under gauze floor – Animals placed in container, until unconsciouness or dead (Not applicable)

Alternate Gaseous Agents (Humane culling) • Gaseous anesthetic agents – halothane, enflurane and isoflurane – piped into container or on wool/gauze at the bottom of container – expensive and should be conducted in well-ventilated room – ether not recommended • Hydrogen cyanide gas – safety concerns restrict use • Carbon monoxide – Readily available, but fumes must be cooled • Methyl bromide – Is also capable of neutralizing or destroying virus, but environmental concerns restrict its use (Not applicable)

Carcasses destruction after culling Burning : Small number Burying : Both small and large number (by Hoe or Backhoe)

Safety Burying 1. Hole should be located far from well, pond, or other animals 2. Hole should be at least 1 meter deep 3. Quicklime should be added to the bottom and borders of the hole. 4. Place all birds and other contaminated objects in the hole 5. Cover with quicklime 6. Cover with earth or topsoil

Animal Vaccinations for Avian Influenza

Overview of Vaccines Tested and available: • Inactivated (killed) whole AI virus • Good efficacy against H5 subtype • Good resistance to infection • Reduced amount of virus in environment • Administered by injection • Differentiating Infected from Vaccinated Animals Potential future vaccine: • New recombinant fowlpox vaccine

Inactivated Vaccines • Homologous – – Contains same strain as virus in the field – Field tested in Mexico/Pakistan • Prevents clinical disease • Reduces amount of virus shed into environment – Impossible to differentiate vaccinated from field- exposed • Heterologous – – Contains same strain, but has a heterologous neuraminidase – Same clinical and shedding results, but • antibodies against neuraminidase create field marker

Commercial AI Vaccine for Poultry (at present available) • Gallumine Flu (H 5 N 9 ) from Merial comp. France • Nobilis influenza (H 5 N 2 ) From Intervet Comp. Netherland • Poulvac I AI (H 5 N 9 ) From Fort Dodge Comp. USA • AI Vaccine H5N1 (No detail) China

Differentiating Infected from Vaccinated Animals • Same haemagglutinin (H) as challenge virus • Different neuraminidase (N) Results: – Homologous H group = clinical protection of 93%, regardless of vaccine scheme – Serological survey showed almost perfect agreement with sensitivity = 98.1 and specificity = 95.7 respectively – Could be an effective strategy to control AI infections in poultry Source: Avian Pathology (2002) 32, 47-55

Recombinant Vaccines 1. Utilizes bacteria or yeast to produce large quantities of a single viral protein 2. Protein then purified and injected into animal, which develops antibodies against the protein causing protection from the disease • NOTE: Currently only licensed and field tested in Mexico, using a fowlpox virus expressing the H5 antigen

Results of Recombinant Study - Mice • Genetically engineered adenovirus to express all or parts of avian influenza hemagglutinin (HA) on its surface • Based upon sequenced strain of H5N1 from Vietnam Vector Results Adenovirus: no H5N1 genes • 3 Days - Substantial weight (empty vector) loss • 6-9 Days – All mice dead Adenovirus w/ wild-type • Mild and short lived weight H5N1 loss • All mice survived infection Source: Journal of Virology, February 15, 2006

Results of Recombinant Study - Chickens Vector Results Adenovirus: no H5N1 genes • All chickens died within 2 (empty vector) days of exposure Adenovirus w/ wild-type • All chickens survived H5N1: Subcutaneously exposure and developed strong HA antibody response Adenovirus w/ wild-type • Half of the chickens died H5N1: Intranasally and half survived Source: Journal of Virology, February 15, 2006

Poultry Vaccination Schedule - Minimum age for Second shot first injection Emergency All poultry, 4-6 weeks later regardless of age 4-6 weeks (1 st ) Replacement Flocks At birth ( High Risk Areas) 16-18 weeks (2 nd ) Replacement Flocks 4 weeks 16-18 weeks ( Low Risk Areas) Layers 8 days 36 days Broilers*** 8 days Should not given ***Vaccination of broiler chickens in principle is discouraged, as there isn’t sufficient time to develop adequate immunity

Sample Vaccination Schedule – Geese and Ducks Notes: Minimum age Second shot The first infection for first is not given to the injection birds in the month Duck ready for 3 weeks 4 weeks later prior to their departure from the foie gras farm production The second shot is Geese 4 weeks 3 weeks later not carried out on birds due to leave the farm during the week scheduled Other ducks 3 weeks 4 weeks later for the second shot Source: Official Journal of the EU, 25.2.2006, L 55/51

Vaccine Strategies • Stamping-out – destruction of all poultry in a defined area (1km to >10 km) and “at risk” farms • Vaccination areas – well defined, manageable zones that are as self contained as possible, limiting the need to transfer poultry across borders • Monitoring – assessment of vaccination should be done one month after 2 nd vaccination. Serological methods may vary.

Vaccine Strategies for Different Situations H5/H7 virus Index Evidence of Population Policy pathogenicity case spread to in density flock industrial area sector HPAI/LPAI Backyard No High/Low Stamping-out HPAI/LPAI Backyard Yes Low Stamping-out High Vaccination HPAI/LPAI Industrial No High/Low Stamping-out HPAI/LPAI Industrial Yes Low Stamping-out High Vaccination Source: OIE 71 SG/12/CS3 E: The Use of Vaccination as an Option for Control of Avian Influenza

Monitoring Measures

Actions when a Case is Detected in a Vaccinated Flock • Immediate quarantine of infected site • Depopulation of flock, preferably with disposal of the birds on site (burial) • Disposal of litter, onsite to limit risk of spread – Burial – Piles covered with resistant sheet of plastic • Eggs, egg-trays, animal feed, etc. should be destroyed • Intensified surveillance – 3-5 km. radius – Sudden mortality of sentinels should be investigated • Limit movement of poultry and poultry-related products for at least 21 days after cleaning/disinfection of site Source: Guidelines for the Administration of Nobilis Influenza H5 Vaccine as Part of an Avian Influenza Strategy

Advantage and Disadvantage of AI Vaccine Advantage Disadvantage • Reduce susceptibility to • Difficult to diagnose when infection human case occurred. • Reduce duration of virus • Cannot differentiate of shedding infected poultry if no sentinel birds • Reduce viral Load in the environment • Much more works for monitoring • Good for layers and breeders flocks • Not good for broiler flocks