Sunday, November 13, 2022

Mexico: Senasica Orders Strategic Vaccination Of High-Risk Poultry Against HPAI H5N1



Outside of China, Egypt and parts of Southeast Asia - all places where HPAI H5 has been endemic for a decade or longer - vaccination of poultry against avian influenza is rare. Instead, eradication (culling) remains the preferred method of AI (avian influenza) control. 

But stamping out the virus by killing millions of birds is both traumatic and expensive, and the recent increase in HPAI H5 epizootics around the world has many countries reconsidering their options.

Although poultry vaccines can help protect flocks against HPAI H5, they must be properly applied and frequently updated, and even then they don't always offer complete protection.  Some birds may still become infected, but due to their vaccination status, not show signs of illness.  

The track record of using poultry vaccines to control avian flu has been mixed. 

China's massive H5+H7 poultry vaccination program of 2017 effectively shut down their H7N9 epizootic and the spillover of that virus into humans, but HPAI H5N6 continues to spread (apparently asymptomatically) in poultry, and infect humans (and other mammals), causing severe illness and sometimes death. 

And despite years of using poultry vaccines to control LPAI H9N2 in China, that virus continues to spread, evolve, and spillover into humans (see Emerging Microbes & Inf.: H9N2 Cluster Among Humans, Chickens & Pet Cat - China, 2018).

A 2021 study (see J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China)) by researchers from Shanghai and the Netherlands found the current inactivated virus vaccines used in China against H9N2 to be no match for this rapidly evolving pathogen. 

They warned:

The failure of vaccination might be because of inefficient application, low dose, and low vaccination coverage (especially in the household sector).11,12 Moreover, the continuing transmission in combination with the intensive long-term usage of the inactivated virus vaccine may have led to antigenic changes leading to immune escape.

Some other examples of sub-optimal vaccine performance include:

In 2009's Avian influenza and vaccination: what is the scientific recommendation?, the OIE (now WOAH) reiterated their strong recommendation that humane culling be employed to control avian influenza, and advising that vaccines should only be used as a temporary measure, stating that  `Any vaccination campaign must include an “exit strategy” i.e. a return to classic disease control measures.'

While still discouraging their use, in 2013 the OIE softened the language in their recommendations to allow:

'In short, vaccination should be implemented when culling policies cannot be applied either because the disease is endemic and therefore widely present, or the infection in affected animals is too difficult to detect.'

Until recently, avian flu outbreaks outside of Asia and the Middle East were rare enough that `stamping out' the virus by culling was viewed as preferable to vaccination.  Some of that was based on a fear that international trading partners would be reluctant to buy vaccinated birds, and some of it due to the concerns expressed above. 

But HPAI H5 is no longer rare, and may soon become a perennial threat both in Europe and North America.  

Despite the downsides - between rising inflation, food insecurity, and the economic losses and negative publicity that comes with culling millions of birds - suddenly AI vaccination of poultry is looking a lot more attractive to some countries. 

Two days ago Mexico's SENASICA announced plans to begin vaccinating high-risk poultry against H5N1.  The press release follows, after which I'll have a brief postscript.

Technicians from the Ministry of Agriculture and Rural Development and the National Union of Poultry Farmers designed a vaccination plan aimed at protecting production units located in areas of high health risk.
National Service for Agrifood Health, Safety and Quality | November 11, 2022 | Release
In the presence of highly pathogenic avian influenza (HPAI) AH5N1, the National Service for Agrifood Health, Safety and Quality (Senasica) instructed the strategic vaccination of long-lived birds in high-risk zoosanitary areas.

The agency of the Ministry of Agriculture and Rural Development informed producers of the measure, whose purpose is to protect national poultry production and guarantee the supply of chicken meat and eggs.

Vaccination will be carried out in accordance with a strategic plan designed by the technicians of the General Directorate of Animal Health (DGSA) of Senasica, in coordination with the National Union of Poultry Farmers (UNA), which provides, in the first instance, to protect the progenitor and reproductive birds, since they are the origin of the productive chain, since they are the mothers of the broiler chicks and the hens that lay eggs.

Similarly, the plan considers the protection of poultry production units that are located in areas of high animal health risk and in this way avoid losses in the production of chicken and egg for food.

At this time there are vaccines that three laboratories produced in Mexico for sale abroad, but, given the presence of HPAI AH5N1, it has been requested that they include distribution in this country for UPAs that are authorized by Senasica to Vaccinate your birds.

The DGSA explained that the effectiveness tests of the vaccines currently produced in Mexico were carried out in reference laboratories of the World Organization for Animal Health (OMSA) in other countries, for which the effectiveness of the available biologicals is considered.

In order to have greater certainty, the technicians of the National Center for Diagnostic Services in Animal Health (Cenasa) of Senasica, in coordination with the UNA, are already carrying out tests to verify the response of the biological to the strain that circulates in Mexico.

Control actions advance

So far, technicians from the United States-Mexico Commission for the Prevention of Foot-and-Mouth Disease and Other Exotic Animal Diseases (CPA) of Senasica have confirmed the presence of highly pathogenic avian influenza AH5N1 in nine entities of the country.

It has affected four commercial UPAs, three of them in Sonora and one in Nuevo León, as well as three backyard farms: Chiapas, Chihuahua and Estado de México, with a total of 492 thousand slaughtered birds, which means 0.023 percent of the national poultry inventory, so the supply of chicken and eggs for the national market is not compromised.

Similarly, cases have been reported in wild birds in wetlands in the State of Mexico and Jalisco, in a protected nature reserve in Texcoco, and in parks in Baja California, Aguascalientes, and Puebla.

The agency of the Ministry of Agriculture and Rural Development pointed out that the coordinated work between health authorities and poultry producers has intensified, with the purpose of increasing biosecurity measures in UPAs throughout the country and protecting national chicken production. and egg.

He revealed that since the presence of the virus was detected in farms in Sonora and Nuevo León, Senasica applied internal quarantine, which, among other aspects, implies that in order to mobilize and market poultry products, producers must demonstrate that their farms are free of IAAP AH5N1, through tests that must be carried out in the official laboratories of the Ministry of Agriculture.

With this measure, he explained, the probability of spreading the virus decreases and consumers are given certainty about the health of the poultry products they consume.

(Continue . . .)

In theory, a comprehensively applied, and frequently updated poultry vaccination program should be an effective strategy against avian flu, at least in captive birds.  But in actual practice (see Egypt: A Paltry Poultry Vaccine), those can be difficult standards to maintain. 

Poultry vaccination brings with it a new set of problems, and even has the potential to make a country's avian flu situation worse (see MPR: Poultry AI Vaccines Are Not A `Cure-all’ & New Scientist: The Downsides To Using HPAI Poultry Vaccines)

But given the continued spread of HPAI H5, I expect to see more countries move towards vaccinating poultry against avian flu.  

Hopefully, if they do, they will avoid some of the mistakes of the past.