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Vaccination Stopped Avian Influenza in Mexico

5 October 2012, at 11:55pm

ANALYSIS - The H7N3 avian influenza outbreak in the Los Altos region of the state of Jalisco is under control. Thanks to the quick identification of the virus and production of a vaccine that was successfully used to halt the disease, it has now been well over 40 days since the virus was last isolated, writes Chris Wright, senior editor of ThePoultrySite.

The effect of this outbreak has been devastating to the commercial egg sector in the Los Altos region, Mexico's primary egg production zone. Jalisco state accounts for 55 per cent of the Mexican egg supply. The Los Altos region alone has 60 million layers.

The official statistics indicate a loss of over 22 million laying hens due to highly pathogenic avian influenza (HPAI), which represents 26 per cent of egg production in Jalisco, and 15 per cent of total Mexican egg production.

The various impacts of this outbreak were discussed in the 'Emerging Poultry Disease Course' presented by the ANECA, the Mexican Poultry Science Association and Senasica, the Mexican government's animal health organization, in Mexico City on 27 and 28 September. There were close to 150 participants at this event.

Virus identification

The rapid identification of the virus and production of an autogenous vaccine demonstrates the high level of cooperation between the academic, industry and government sectors, which led to the quick control of this disease.

Back in 2006, as part of a research project at UNAM (the National Autonomous University of Mexico), a low-pathogenic H7N3 avian influenza virus was identified from a migratory duck. This waterfowl was found in an area very far away from Jalisco state. The virus turned out to be very similar to the one that affected the layers in the Los Altos region.

This was the virus that became the seed virus for producing the vaccine. Although it sounds rather simple, it took endless hours of work to get the seed virus to be effective against the active virus in Los Altos, explained Dr Juan Antonio Montañ of the DGSA, part of Senasica.

During this process, said Dr Montaño, it was verified that although the two viruses, from 2006 and 2012, were both H7N3, they were quite different. It could be stated without a doubt that the 2012 Los Altos virus was not related to the virus discovered in 2006. That is to say that the 2012 virus is a new virus and that the 2006 virus has not been circulating in the country for the last six years, undetected. This was a significant finding, in and of itself.

Vaccine production

Once the seed virus was ready it was sent to four laboratories to produce, one being the government lab, Pronabive, and three private ones. The private labs were needed in order to produce enough vaccine doses. Just one month after they received the seed virus, the laboratories had produced the vaccine and layers were being vaccinated in Los Altos. This was a very quick response, by any measure.

The Mexican Poultry Association (UNA) invested significant funds in order to cover the start-up costs for vaccine production, said Jaime Crivelli, UNA President.

Vaccination priorities

Once received, vaccine application was the sole focus of the poultry producers, with an 'all hands on deck' effort, said Dr Ramon Lopez, Hy-Line consultant in Los Altos. The virus primarily affected layers in production and, to a lesser degree, pullets in the rearing stage.

Therefore, the vaccination priority was, in order: layer breeders, pullets, layers in production and broilers. Each bird was given two doses of the vaccine.

The laboratories produced nearly 90 million doses in the first lot. The second lot is currently in production and will produce another 90 million doses.

Vaccination: temporary solution

Dr Assad Heneidi of Senasica has been very involved in monitoring and controlling this outbreak since the very beginning, and he explained that the vaccine is only a temporary solution to the problem. The vaccine is neither registered nor authorized. It can only be used in the Los Altos region of Jalisco, which was the only area in Mexico that was affected by H7N3. Therefore, use of the vaccine is not approved anywhere outside of the Los Altos zone (which is heavily quarantined). Other parts of Mexico have requested use of the vaccine as a preventative measure, but Dr Assad said that the approval will not be given.

The idea is to discontinue using the vaccine as soon as the elimination of the pathogen is confirmed. It is not the solution to the problem. "There must be a focus on biosecurity to guarantee this will not occur again", he indicated.

Dr Assad did not say when they will stop using the vaccine, although he said it could be before the end of the year. In order for the Los Altos region to be declared free of H7N3, the last vaccinated layer will need to have ended egg production and have been culled, which will not be until sometime next year.

Finally, Dr Assad assured the audience that very thorough monitoring for H7N3 is taking place throughout the country. He reiterated that the outbreak never got out of the Los Altos region, not even to other parts of the state of Jalisco.

Further Reading

You can visit the Avian Flu page by clicking here.