Published a study that evaluated vaccination campaigns against avian influenza

Researchers from the Centre de Recerca en Sanitat Animal (CReSA) participated in a study published in Clinical and Vaccine Immunology with the objective to evaluate two vaccination campaigns carried out between 2006 and 2008 in zoos and wildlife centers. To date, this is the most comprehensive study reported concerning number of animals and species.

Avian influenza (AI) virus has been considered a great threat during last years, especially after the outbreaks caused by H5N1 HPAI virus. Aquatic wild birds, including Anatidae (ducks, geese and swans) and Charadriidae (shorebirds), are widely considered to be the natural reservoir of AI virus. In 2002 an outbreak of H5N1 HPAI virus in Hong Kong caused mortality in a wide range of avian species, including migratory birds and resident waterfowls. In 2005, another outbreak of H5N1 HPAI virus killed over 6,000 water birds, in northwest China. Vaccination campaigns, together with good surveillance programs, are an important key to prevent and control future outbreaks.

Due to unprecedented morbidity and mortality caused by H5N1 HPAI virus and given the value of birds kept in zoos, in 2005 the European Commission directive 2005/744/EC allowed vaccination against AI virus in such birds in zoos, under strict surveillance. In 2006, 15 Spanish zoos and wildlife centers underwent a vaccination program with a commercial inactivated H5N9 vaccine. Between November 2007 and May 2008, birds from 10 of these centers were vaccinated again with a commercial inactivated H5N3 vaccine, as decided by the Spanish government.

The current study was designed to assess the immunological response elicited after each vaccination individually; and also to observe and compare the effect of successive heterologous vaccines.

To date, this is the most comprehensive study reported concerning number of animals and species. To evaluate the humoral immune response induced after both vaccinations, specific antibody titers were determined by hemagglutination inhibition (HI) test. Higher HI titers indicate higher antibody response. Results obtained by HI demonstrate that both vaccines are efficient, eliciting high HI titers (>100). However, we observed heterogeneity in the antibody responses in vaccinated birds, which varied greatly, not only between taxonomic orders but also between species of a single order and even within species. The most interesting finding is that, although some avian species (those belonging to Psittaciformes order) did not show HI titers for any of the single vaccination; when priming with H5N9 and subsequently boosting with the H5N3 vaccine induced a significant antibody response (>32), albeit at lower titers than the others. To design future vaccination strategies in exotic wild birds, it is important to evaluate both, the response against the vaccine and the durability of HI antibodies. On average, the birds had titers less than 20, meaning that 1.5 years after vaccination, we cannot detect HI titers in serum samples.  An important alternative to increment the immune response and protect a wide number of wild birds against a possible infection with H5N1 HPAIV is a primer (H5N9)-boost (H5N3) vaccine strategy. The results obtained with the present study, together with the results from similar Studies carried out in other EU countries are an important tool to design future vaccination protocols.

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These results have been published in: Comprehensive Serological Analysis of Two Successive Heterologous Vaccines against H5N1 Avian Influenza Virus in Exotic Birds in Zoos. Júlia Vergara-Alert, Hugo Fernández-Bellon, Núria Busquets, Gabriel Alcántara, María Delclaux, Bienvenido Pizarro, Celia Sánchez, Azucena Sánchez, Natàlia Majó and Ayub Darji. Clinical and Vaccine Immunology, May 2011, p. 697-706, Vol. 18, No. 5.

Data were collected during a program coordinated by the Iberic Association of Zoos and Aquariums (Asociación Ibérica de Zoos y Acuarios) and the Spanish Government to assess the efficacy of vaccination. This work was partially supported by the AGL2007-60434/GAN project funded by the Spanish Government and by the EUROFLU project (SP5B-CT-2007-044098) funded by the European Union. We are grateful to staff at participating zoos for their collaboration and kind help in data compilation, including Rocío Canales Merino (Safari Park Vergel), Loles Carbonell (Jardín Zoológico de Valencia), Sergio Fernández Hernández (Selwo Marina and Selwo Aventura), Daniel García Párraga (L'Oceanogràfic), Candelaria González Villavicencio (Águilas Jungle Park), Ayose Melián Melián (Palmitos Park), Tania Monreal Pawlowsky (Marineland Mallorca), Miguel Angel Quevedo Muñoz (Zoo Botánico Jerez), José María Rodríguez Linde (Oasys Parque del Desierto de Tabernas), and Fernanda Valdés García (Senda del Retiro), as well as staff at Faunia, Zoo Aquarium de Madrid, Zoo de Fuengirola, and Parc Zoològic de Barcelona.

To contact with the author of this paper:

Júlia Vergara Alert
PhD student
Tel. no.: +34 935814527
Fax: +34 93 5814490
Edifici CReSA. Campus UAB
08193 Bellaterra (Barcelona) Spain

Download the full paper: Clinical and Vaccine Immunology

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