Avian Influenza a deadly threat

Transcription

1 Avian Influenza a deadly threat Nobilis Influenza Vaccines Complementing an AI eradication strategy

2 Highly Pathogenic Avian Influenza A deadly threat to world poultry production Avian influenza (AI) viruses (Influenzavirus A genus of the Orthomyxoviridae family) are divided into subtypes on the basis of: 15 haemagglutinin antigens (H1-15) 9 neuramidase antigens (N1-9). AI viruses infecting poultry are further divided into two distinct groups: highly pathogenic avian influenza (HPAI) (bird flu or fowl plague) - may result in flock mortality as high as 1% - restricted to subtypes H5 and H7, although not all viruses of these subtypes cause HPAI. - classified as a list A disease by the World Organisation for Animal Health (OIE) low pathogenic avian influenza (LPAI) - clinical signs range from asymptomatic to mild respiratory disease, depression and egg production problems in laying birds - concomitant infection with other organisms or suboptimal environmental conditions may cause more serious disease. During the past decade a notable increase in the number of reported cases of HPAI has been seen. Summary of the number of reported HPAI outbreaks Period Years Reported outbreaks 3 years years years (1 in Asia) The recent HPAI H5N1 epizootic in Asia affecting ten countries in the region has raised the international profile of AI. The transmission of the avian influenza virus to humans, with often lethal consequences, has further raised public concern. Source unknown Source unknown Control strategies must be based on knowledge of the major pathways of spread of the HPAI viruses, their persistence in the environment, susceptibility to inactivation, and the proven efficacy of vaccines to prevent infection and/or disease. The main measures available to prevent, control and eradicate HPAI are: Effective disease surveillance for early detection and reporting of outbreaks. Enhanced biosecurity of poultry farms and associated premises. Control of movement of birds and products that may contain virus, including controls at the interface of infected and uninfected areas. Changes to industry practices to reduce risk. Rapid, humane destruction of infected poultry and poultry at high risk of infection. Disposal of carcases and potentially infective material in a biosecure and environmentally acceptable manner. The proper use of vaccination. All of these control measures reduce risk but none used in isolation is sufficient. FAO - September 24 (1)

3 Nobilis Influ Protect against infection Significant reduction in virus replication Lohmann Brown layers were vaccinated at 12 weeks of age with Nobilis Influenza H7N1 (.25 ml - half of the recommended dose). Challenged 5 weeks later with HPAI H7N1 (A/chicken/ Italy/445/99). Protective antibody levels develop within 3-4 weeks of vaccination. HI Hi Titre Titre (log2) (Log 2) Antibody titre Weeks Post Vaccination Re-isolation titre of AI virus from organs Log 1 EID Legend 3 dpc Control = Titre of virus isolated from controls 3 days post challenge. 3 dpc Vaccinated = Titre of virus isolated from vaccinated birds 3 days post challenge. 6 dpc Vaccinated = Titre of virus isolated from vaccinated birds 6 days post challenge. (No controls survived till 6 days post challenge.) Lungs Trachea Liver Pancreas Proventriculus Jejenum Caecal Tonsils Cloaca/Bursa Spleen Kidney Ovary Brain Source: Dr Werner - Federal Research Centre for Virus Diseases of Animals, Riems, Germany. If H5N1 HPAI virus enters a vaccinated flock it will encounter birds that have an increased resistance to infection, which reduces the likelihood of birds becoming infected. If some birds do become infected the quantity of virus they excrete is reduced, reducing the risk of onward transmission. In properly vaccinated poultry exposed to field virus, infection is highly unlikely to proceed through the flock. FAO - September 24 (1)

4 enza Vaccines and reduce viral shedding Significant reduction in virus shedding 3 week old SPF chickens vaccinated with.5ml Nobilis Influenza H5 Challenged 3 weeks later with an HPAI H5N1 isolate (Asia, 23) % Shedders 2 Days Post Challenge % Oral Cloacal Field Experience Ellis et al. (2) reported the successful interruption of HPAI H5N1 virus transmission on three infected farms in Hong Kong (December 22 to January 23). Success ascribed to implementation of strict quarantine measures, depopulation of affected sheds, increased biosecurity and vaccination of unaffected sheds and surrounding farms with Nobilis Influenza H5. On two farms infection spread to recently vaccinated sheds - low rate of H5N1 mortality recorded, 9 to 18 days post vaccination - H5N1 related deaths stopped from 19 days post vaccination - intensive monitoring by virus culture showed no evidence of asymptomatic shedding 2 Control Vaccinated Reduction of virus titer excreted from vaccinated chickens of between 1 thousand and 1 thousand times compared to excretion from unvaccinated controls. Average Virus Titre from Shedders Conclusions Nobilis Influenza H5 (inactivated AI H5N2) was able to protect chickens from disease caused by HPAI H5N1 and interrupt virus transmission from 19 days post vaccination. 7 6 Oral Cloacal Log1 EID Control Average HI titer three weeks post vaccination of 7 log 2. No clinical signs observed in the vaccinated birds All control chickens showed severe clinical signs and died post challenge Vaccinated Source: Dr D.E. Swayne DVM PhD, Southeast Poultry Research Laboratory, USDA/ARS, Athens, Georgia. The main objectives of vaccination are to reduce the production losses caused by the disease, to reduce the risk of spread of AI virus to animals and humans by reducing the shedding of viruses in the environment, to create (by way of vaccine induced immunity) barriers between infected and free areas/compartments and to help in the control and eradication of the disease. FAO - September 24 (1)

5 Eradication of HPAI The ultimate goal for any AI control program is to eradicate HPAI Standard approach Quarantine and increased biosecurity Culling and safe disposal of infected flocks Culling and safe disposal of high risk contact flocks in a quarantine zone Intensive monitoring for positive flocks in a surveillance area surrounding the quarantine zone. Success dependant on Timely detection and confirmation of index case (first infected flock) Coordinated effort in establishing and policing the quarantine zone Infrastructure to rapidly cull and safely dispose of all infected and high risk contact flocks Identifying and eliminating/managing the source of infection Vaccination compliments an eradication program as an additional control measure valuable in creating a buffer zone, so called ring vaccination - All flocks in the quarantine zone are culled - A surrounding buffer zone is vaccinated - good chance for immunity to develop prior to virus exposure protecting high risk flocks repopulation of previously infected areas - free range poultry - poultry in endemic areas or with known close contact with other avian carrier species (e.g. ducks and other waterfowl) protecting valuable breeding stock protecting informal poultry population - backyard flocks - hobby poultry - fighting cocks In an uninfected country with no infected neighbours, the risk of infection would be negligible and veterinary authorities would not normally consider routine vaccination. However, in a country in which domestic waterfowl, live bird markets or wild birds are reservoirs of virus, the poultry industry is at higher risk of infection. In such situations, veterinary authorities would be more likely to consider vaccination as one of the control measures. FAO - September 24 (1)

6 Nobilis Influenza Vaccines Complementing an eradication strategy Recommended vaccination schedule* Emergency Vaccination Schedule: Primary vaccination administered to all poultry irrespective of age. Booster vaccination 4-6 weeks later. (if primary vaccination is administered before 3 weeks of age a revaccination at weeks of age is recommended) Vaccination of Replacement Flocks: In high risk areas (active infection) primary vaccination (.25ml) is recommended at day old to establish early immunity. Two booster vaccinations (.5ml) are recommended at 4-6 and weeks of age. In areas with high infection pressure revaccination at midlay may be indicated. In low risk areas, or where poultry flocks are reared in an AI free zone with the intention of future transfer into an AI positive zone. Primary vaccination (.5ml) administered at 4 weeks of age and booster vaccination (.5 ml) administered at weeks of age. * Under all circumstances vaccination schedules implemented should comply with requirements of national regulatory authorities Description Inactivated avian influenzavirus Type A antigen (subtype as specified per product) prepared as a water-in-oil emulsion vaccine. Administration: intramuscular or subcutaneous (lower back of the neck) injection. Presentation: 5 ml bottle equivalent to 1 doses. Intervet Avian Influenza Vaccine Range Vaccine Name Nobilis Influenza H5 Nobilis Influenza H5+ND Nobilis Influenza H7N1 Nobilis Influenza H7N7 Nobilis Influenza H9N2 Nobilis Influenza H9N2+ND References 1. FAO Recommendations on the Prevention, Control and Eradication of Highly Pathogenic Avian Influenza (HPAI) in Asia - September Avian Pathology (24) 33, Vaccination of chickens against H5N1 avian influenza in the face of an outbreak interrupts virus transmission. T.M. Ellis, C.Y.H.C. Leung, M.K.W. Chow, L.A. Bisset, W. Wong, Y. Guan and J.S. Malik Peiris. Visit AI Subtype H5N2 H5N2 H7N1 H7N7 H9N2 H9N No part of this brochure from Intervet International bv may be reproduced or transmitted in any form or by any means without written permission from Intervet International bv 24, Intervet International bv, The Netherlands. Intervet International bv P.O. box AA Boxmeer The Netherlands Phone: Fax: info@intervet.com