This special edition of EGG-NEWS provides commentary on recent publications, reports and events relating to highly pathogenic avian influenza (HPAI).  As of mid-April, outbreaks have ceased among large egg production and pullet rearing complexes.  Notwithstanding this hiatus, evident since the beginning of March, incident cases are reported among backyard flocks, turkey growing facilities and at live bird markets suggesting extension from reservoirs of infection.  Cessation of new cases in large egg production complexes is attributed to the end of seasonal migration of waterfowl that have now settled into their annual breeding cycle.  Sporadic cases are probably due to shedding of H5N1 virus by non-migratory domestic birds.  Given experience in recent years we can anticipate a resurgence of infection in the fall as the southward migration commences impacting farms along the Pacific, Central and Mississippi flyways.  This period of low HPAI activity should be used to strengthen biosecurity and to initiate protective vaccination of rearing pullets in high-risk areas in order to develop an immune population that will be challenged during the third and fourth quarters of 2025.

Noteworthy publications and events over the past two weeks relating to HPAI are reviewed for the benefit of subscribers:-

HPAI Vaccination Work Group Submits Proposal

A working group comprising Drs. John Clifford, Craig Rowles, Travis Schaal and David Swayne distributed a proposed vaccination plan dated April 1, 2025, to respond to highly pathogenic avian influenza (HPAI) in the U.S. egg industry.  The Working Group was convened by the United Egg Producers and the American Egg Board representing U.S. egg producers. The document includes factual information on the availability and efficacy of vaccines and incorporates sections on monitoring for effective immunization and surveillance to facilitate certification for export.

Essentially the document confirms what many in the industry have recognized as the futility of the USDA-APHIS response of attempting to ‘stamp out” the endemic infection given the unprecedented depopulation of over 130 million egg laying hens on more than 130 farms since the onset of the current H5N1 epornitic that commenced in 2022.

The summary correctly maintains that “a new approach to reduce layer and pullet flock susceptibility to HPAI virus should be considered to increase resistance to infection, reduce viral shedding and importantly reduce the risk of a potential mutation event that may lead to further HPAI infection in human.”  The document suggests a program under which flocks could be vaccinated with a priority for replacement pullets.  The report correctly stresses the need for high levels of biosecurity, echoing the recommendations of the World Organization of Animal Health. 

Vecor vaccination  in ovo  or S.Cut to chicks with booster

Oil-emulsion vaccine im during rearing

The report failed to stress the impact of flock depletion on egg prices and the cost to consumers that exceeded $15 billion in 2022 and considerably more in 2024 with an additional escalation in prices peaking at $8.50 per dozen at retail in late February 2025, reflecting the loss of approximately 30 million hens over an eight-week period.

The zoonotic potential of H5N1, deserved more than seven lines in a text extending over 13 pages.  Virologists and epidemiologists involved in monitoring aspects of the molecular biology of influenza have constantly stressed the risk of emergence of a zoonotic strain of H5N1 with possible human-to-human transmission.

One of the authors of the report is a distinguished researcher and has extensive experience in international regulation of avian diseases.  A member of the committee authoring the document is a prior Chief Veterinary Officer of the USDA responsible for the response to the 2015 HPAI epornitic.  Following retirement, he has served as an advisor to the USA Poultry and Egg Export Council that has a single-purpose commitment to maintaining the export volume of broiler leg quarters.  It does not appear from the document that his affiliation in any way affected his scientific objectivity. It would have been possible to have made a more definitive and stronger case for vaccination with a broader representation from among the industry.

The return of incident cases during the fall migration of waterfowl is inevitable. The current ongoing outbreaks may be attributed to resident avian and mammalian carriers. Recognition that the infection can be transmitted by the aerogenous route invalidates even strict structural and operational biosecurity and places large complexes with power ventilation at risk. The need for vaccination especially in high-risk regions along the Mississippi and Pacific flyways is self-evident.  The proposal to vaccinate pullets is obvious but will delay creation of an immune population due to the biological time restraints associated with rearing. 

The report notes, “Vaccination of caged in-lay hens is challenging and potentially unachievable in cage-free operations.” This appears to be a questionable assertion.  When the industry was confronted with severe coryza in 2023, egg producers effectively administered oil emulsion vaccines by the intramuscular route to hens in both cages and aviaries in the face of infection.

This commentator strongly supports the recommendation contained in the summary, “The industry believes that it time to enhance our overall strategy to control the virus through implementing vaccination in egg laying flocks.”  In contradistinction he final paragraph relating to “acceptability to the federal government, state animal health officials” is the major defect of the report inducing a wishy-washy, non-definitive approach ending with “We look forward to further discussion with USDA about the proposal.” 

Effectively if the broiler segment of the poultry industry is still opposed to vaccination of egg production flocks and possibly growing turkeys in high-risk regions, despite appropriate monitoring and surveillance, all we will have is more discussion and temporizing without action.  The so-called four-pronged program advocated by the newly appointed Secretary of Agriculture is effectively smoke-and-mirror, more of the same widow dressing.  It appears that USDA-APHIS either through disinclination to accept realities or acting under the duress of exporters will continue to discuss, research, evaluate, and consider vaccination while continuing to implement whack-a-mole flock depopulation at the expense of taxpayers, producers and consumers. The essence of the report is reminiscent of the sentiments attributed to St. Jerome who prayed for chastity-- but not right away.

Prominent Health Advocate Comments on the Need for Vaccination Against HPAI

Dr. Scott Gottlieb, a physician, investor in medical companies and a director of pharmaceutical enterprises previously served as the 23^rd Commissioner of the Food and Drug Administration in the first administration of President Trump.  He recently authored a commentary pointing to the need for vaccination of poultry flocks using currently available commercial off-the-shelf products.  In his commentary he justifiably castigated Robert F. Kennedy, Jr., Secretary of the Department of Health and Human Services, who advanced the inane suggestion that HPAI should be allowed to spread unchecked through flocks in the hope that a few survivors would express genes for resistance to avian influenza.

Dr. Gottlieb correctly maintains that the egg industry must use the current seasonal quiescent stage of the epornitic before resumption of migration in the fall to establish immunity among flocks at risk.  He expresses this sentiment as, “We have vaccines for bird flu made by American companies and used overseas but so far federal officials don’t seem poised to use them here.”  He points to the deployment of vaccines in France, China and Mexico among other nations and cast doubt on the various distortions of science advanced by opponents of vaccination to support ongoing exports of broiler leg quarters.

Applying logic and common sense, Dr. Gottlieb notes that, “The avian influenza strains now in circulation have persisted continuously among birds and mammals for nearly two years and there’s growing evidence that it could become a permanent feature of North America – part of a the new normal to which the poultry industry must inevitably adjust for both the physical and economic health of Americans.”

Influenza H5N1 is clearly endemic in the U.S. and in the poultry industries of many nations. The incidence rate can be suppressed to some extent by strict structural and operational biosecurity involving investment and management.  Notwithstanding the stringency of biosecurity, there is little that can be done to prevent aerogenous transmission especially into power-ventilated houses located on multi-aged egg production complexes.

Avian influenza is effectively The Newcastle Disease of the 2020s. During the 1970s Velogenic viscerotropic  Newcastle disease (VVND=END) in Europe, Asia and Africa was in every way as catastrophic as avian influenza but was effectively controlled principally by vaccination supported by biosecurity.

It is questioned why a clear thinking and well-connected physician should have a greater appreciation of the risks, consequences and potential control measures to reduce the economic and potential zoonotic impact of avian influenza compared to the administrators of USDA-APHIS. Is the firm recommendation for vaccination advanced by Dr. Gottlieb an expression of epidemiologic reality or is it that Dr. Gottlieb is an independent scientific voice unfettered by conflicts of interest? 

Introduction of the SAVE Our Poultry Act

U.S. Representatives Sarah McBride, (D-DE) and Mike Lawler, (R-NY) introduced the Supporting Avian Virus Eradication (SAVE) Our Poultry Act that is intended to elevate the standard of biosecurity and to encourage research into protection including immunization.

In announcing the proposed legislation, Rep. McBride stated, “The SAVE Our Poultry Act is about supporting our farmers and their efforts to protect their animals, their markets and their future.”  According to an April 10^th release by Rep. McBride, the intended legislation would:

• Authorize USDA research grants to study highly pathogenic avian influenza
• Analyze the impact of poultry vaccination on international trade and market access
• Fund enhanced biosecurity practices and disinfection methods for poultry producers

The press release justifiably notes the high prices for eggs as a result of depopulation of flocks and pointed to the support by the National Chicken Council (NCC) representing broiler producers, the United Egg Producers and regional poultry associations with members at risk of or having experienced losses as result of HPAI. Specifics of the Bill that would amend the Food, Agriculture, Conservation and Trade Act of 1990 emphasizes HPAI as a “high priority research and extension area”.

Among other components the bill makes provision for grants to colleges and universities to “research the effectiveness of vaccines across poultry species, improve formulations of vaccines and improve the delivery mechanisms for vaccines.  This is in itself commendable but ignores the reality that both subunit vector vaccines are available off-the-shelf together with inactivated oil emulsion products that could be deployed immediately following approval and authorization for use by USDA-APHIS.  Ongoing research is obviously beneficial, but the infection is expected to return within months and research envisaged in the SAVE Our Poultry Act would do nothing to reduce losses in 2025 through 2026.

A provision of the bill goes to the core of the disinclination by USDA to allow vaccination.  The SAVE Our Poultry Act would involve “assessing the potential implications of vaccination on domestic and international poultry markets including trade and market access considerations.”  It is evident that the broiler segment of the U.S. poultry industry through its lobbying and the influential Broiler Caucus has effectively prevented the application of vaccination to the detriment of the turkey and egg production segments irrespective of sentiments expressed by the NCC. 

Congressional Response to the Secretary of the Department of Health and Human Services

The poultry industry and human epidemiologists should be alarmed by the misinformed, and incendiary statements by Robert F. Kennedy, Jr. Secretary of the Department of Health and Human Services as reported in the New York Times on March 18^th, relating to “letting avian flu run through flocks so we can identify the birds and preserve those that are immune to it.”  This appalling approach to end the bird flu epidemic is unworthy of even cursory consideration.

Five members of the House of Representatives addressed a letter to the Secretary on April 1^st condemning his statement and demanding reports and copies of communications among the Department of Health and Human Services, the USDA, the Centers for Disease Control and Prevention and the National Institutes of Health regarding mitigation of avian influenza.

In the first instance it is noted that avian influenza will ultimately kill in excess of 98 percent of an infected flock.  During the clinical phase, vast quantities of virus are generated resulting in the potential for inter-farm spread especially where complexes are located in close proximity.  Even if a small proportion of a flock were to survive an outbreak of avian influenza their value for breeding would be negligible given that the commercial generation of broiler, turkey and egg-production flocks are hybrids. The program of “stamping-out” has in all probability reduced farm-to-farm spread notwithstanding the depopulation of 170 million commercial poultry since the onset of the 2022 epornitic.

To add insult to injury, the Secretary of Agriculture, Brooke Rollins apparently embraced the distorted logic expressed by Secretary Kennedy despite confusingly advancing a “four-pronged strategy” incorporating nothing new and funded by  a proposed $1 billion in an attempt to suppress HPAI.

The five members of the House, including Rep. Raja Krishnamoorthi (D-IL), Ranking Member of the Subcommittee on Healthcare and Financial Services and Rep. Gerald E. Connoly (D-VA), Ranking Member of the Committee on Oversight and Government Reform requested a list of non-governmental experts consulted by HHS relating to any federal response to avian influenza.  The Representatives also requested “a full and complete list of individuals who recommended that the federal government would allow avian flu to run through the flock in an effort to build immunity” together with their credentials and past involvement with the federal government.  The letter to Secretary Kennedy raised the justifiable issue of a potential zoonotic infection and stressed the need to “combat, contain and eliminate avian influenza, requiring a concerted and coordinated effort across all relevant federal agencies.”

Secretary Kennedy is devoid of scientific credentials. He has surrounded himself with sophists and charlatans expressing unconventional policies to prevent human infections. He has embraced conspiracy theories on disease and related topics that have been debunked by both U.S. and international scientist and agencies. As a Secretary of the HHS he is entitled to his personal opinions but not a selective or distorted expression of facts

Zoonotic Implications of HPAI

The zoonotic aspect of HPAI was reviewed in a published interview prepared by Dr. Eric Rubin Editor-in-Chief and Dr. Lindsey Baden, Deputy Editor of the New England Journal of Medicine who discussed infectivity of HPAI with virologist Dr. Yoshihiro Kawaoka.  Of concern is the circulation of H5N1 genotype D.11 and B3.13 in avian species and dairy herds respectively.  Although the incidence rate of bovine influenza H5N1 is declining more than 1,000 herds have been diagnosed with possibly many more infected. Both structural deficiencies and a lack of effective biosecurity within the U.S. dairy industry have contributed to dissemination of the virus.  It does not help that the Administration has terminated personnel involved in response to COVID and have effectively disbanded the group of scientists including epidemiologists, virologists and logisticians concerned with preparedness for a future pandemic.  Signing a Presidential Executive Order has transitory political effect but does not necessarily prevent the inevitable emergence of an infection with epidemic or pandemic potential at some time in the future.

Rubin, E. et al outbreak update-H5N1 New England Journal of Medicine 2025 doi.org/10.1056/nejme 2502267

Aerogenous Transmission of H5N1 Confirmed

EGG-NEWS has consistently maintained that highly pathogenic avian influenza (HPAI) can be transmitted by the aerogenous route either as a bioaerosol or entrained on excreta and dust to be moved by wind.  A comprehensive epidemiologic investigation involving field observations, meteorology and molecular studies confirmed the spread of an outbreak of H5N1 from a commercial duck farm to unrelated egg production farms over a distance of five miles.  The case report with appropriate documentation involved an outbreak in the Czech Republic.  The authors note that their findings “underscore the importance of considering windborne spread in future outbreak mitigation strategies.”  Anecdotal and experimental data confirm the possibility of airborne infection extending from waterfowl excreting virus.

The USDA-APHIS has long held that “biosecurity of an acceptable standard will provide protection against HPAI.”  This is a false presumption given the ability of the virus to be transmitted over relatively long distances by the aerogenous route.  As noted by the authors of the Czech paper, power-ventilated egg production housing is extremely vulnerable given the volume of air displaced by fans. Exhaust rates may range from 200,000 to 600,000 cfm per 100,000 hens depending on climatic conditions.  Among the many failures of USDA-APHIS to address appropriate preventive measures has been a neglect of field epidemiology.  The only conclusions that can be drawn from superficial telephone-administered surveys is that proximity to waterfowl preceding an outbreak was a significant risk factor.  This would indirectly correspond with the observations in this significant publication.

Nagy, A. et al bioRxiv doi.org/10.1101/2025.02.12.637829

Editorial Comment

The Economic Impact of HPAI

There is no purpose in tiptoeing around the failure to adopt vaccination against HPAI in high-risk areas.  The broiler industry may or may not lose a part of their market for leg quarters that represent over 97 percent of shipments of USDA-inspected broiler products valued at $4.5 billion in 2024.  Although this restraint is significant in terms of volume and monetary value, the ban on vaccination requires a broader perspective.  The USDA-APHIS has expended over $2 billion in indemnity payments and logistics from the Commodity Credit Corporation.  Individual egg producers have experienced disproportionately higher losses as a result of their inability to supply markets during the period required to repopulate their complexes.  Consumers have been forced to pay high prices for eggs, far exceeding the potential loss that may be experienced through export markets.  In 2022, the average price of eggs was conservatively $2 per dozen higher than it would have been in the absence of HPAI, costing consumers an incremental $15 billion on their grocery expenditures.  In 2024 the cost to consumers as a result of HPAI was infinitely higher given the differential between average shelf price and values that would otherwise have prevailed.  The loss of 30 million hens during the first two months of 2025 was reflected in an escalation in egg prices peaking at $8.58 per dozen at wholesale on February 28^th but declining thereafter to $3.27 per dozen by the end of March. Notwithstanding this decline, the escalation in egg prices attained 60.4 percent in March 2025 compared to twelve months previously.  The disproportionate escalation in the price of eggs should be compared to an increase of 0.5 percent for food-at-home during March.  Within this category, dairy items increased by 2.2 percent, poultry meat by 0.9 percent, cereal and bakery products by 1.1 percent. Fruit and vegetables declined by 0.7 percent. and the fish and seafood category was down by 1.5 percent.

In reviewing the export market for broiler leg quarters, it is noted that volumes are declining but unit prices are moving in the opposite direction although with a net decline in total annual value.  The question arises as to whether importing nations would continue to purchase leg quarters if preventive vaccination were to be permitted for egg-production flocks in high-risk areas. Vaccination would be subject to appropriate monitoring and surveillance in accordance with World Organization of Animal Health (WOAH) or negotiated standards. It is envisaged that USDA-APHIS could certify that broiler flocks of origin contributing to exports were free of HPAI at the time of slaughter.  It is also important to note that many of the nations importing U.S. leg quarters do so on the basis of low cost with an average unit price of $1,424 prevailing over the first two months of 2025 covering 479,000 metric tons.  Many importing nations are endemic with respect to HPAI and in some cases deploy vaccines against the infection. This would facilitate exports in accordance with the rules of the WOAH. 

The USDA-APHIS has been stubbornly remiss in their failure to negotiate terms under which U.S. producers could justifiably export broiler leg quarters from non-infected flocks.  For more than three years the Agency has labored under the misplaced presumption that HPAI is exotic in the U.S. and that the disease could be eradicated following an anachronistic “stamping-out” program.  The fallacy in the APHIS playbook is the failure to accept that infection is disseminated by millions of wild bird reservoirs on a seasonal basis together with introduction by migratory marine birds cohabitating with waterfowl in the Canadian Maritime provinces and in Alaska with extension down into British Colombia.

For the edification of APHIS there is adequate anecdotal and scientific evidence of introduction of infection on to farms by the aerogenous route. This reality means that even the strictest biosecurity does not provide absolute protection against H5N1 and other highly pathogenic avian influenza viruses suggesting a phased shift in the approach to vaccination.

Reducing the Capacity of the U.S to Respond to Zoonotic HPAI

The ongoing mass dismissals in the U.S. Food and Drug Administration will have an adverse effect on testing consumer dairy products although it is generally accepted that pasteurization inactivates bovine influenza H5N1 strain B3-13 virus.  Similar reductions in staffing at the Centers for Disease Control and Prevention will compromise detection of possible zoonotic infection that appears to be increasing in complexity and significance.  Mass layoffs have affected 40 cooperating laboratories within the FDA Veterinary, Laboratory Investigation and Response Network and also the USDA National Animal Health Laboratory Network responsible for aspects of routine and diagnostic activities.  Critical reductions have occurred among the personnel of the National Animal Health Laboratory Network that coordinates activities between the USDA National Veterinary Services Laboratory and the approximately 60 state and university laboratories throughout the U.S. This commentator gives little credence to a USDA spokesperson that averred that job reduction “will not compromise the critical work of the department including its ongoing response to avian influenza.”

Stop Press: 60-Minutes Segment on HPAI

The 60-Minutes airing on April 20^th focused on bovine influenza H5N1 with little coverage of HPAI in poultry other than the obvious impact on egg prices. The greatest deficiency was a lack of ‘assurance’ that avian influenza is not transmissible to consumers through eggs.  APHIS was disinclined either through governmental restraint or lack of photogenic administrators, from participation in the program.

The Bottom Line

It is hoped that well-intended Congressional action, comments by informed commentators and scientific publications will break the de facto veto exercised by the broiler sector over vaccination as a modality to suppress outbreaks of HPAI in turkey and egg-producing flocks. Further temporizing proposed in the form of additional “discussion” and “research” is disingenuous. Delay will be both costly and represent a risk of emergence of a potentially zoonotic strain. The Administration should sincerely work towards reducing the price of eggs over the long term, limit public sector expenditures on control and avoid even the smallest risk of a catastrophic pandemic. Those in authority in the  USDA and DHHS would be well advised to heed the advice of epidemiologists, avian health practitioners, the WOAH and informed observers regarding the efficacy and desirability of vaccination to establish immune populations with appropriate surveillance in high-risk areas.

This special edition of EGG-NEWS is intended to update subscribers with recent events relating to HPAI with commentary. The past week was dominated  by the as yet single case of HPAI in a commercial farm in Brazil and the implications arising from the event. A case  of HPAI in a large egg-production complex in Arizona in late May suggests that infection may be introduced onto farms from sources other than seasonally migrating waterfowl that are currently in their breeding areas. 

The messages to be conveyed in this edition are:-

•   HPAI should be recognized as a panornitic. This dictates radical changes to traditional restraints on international trade in poultry and products. Import regulations should be amended to conform to WOAH principles and standards including regionalization, compartmentalisation, vaccination and surveillance
•   HPAI is endemic in the U.S. especially impacting  regions corresponding to the four migratory flyways.
•   Biosecurity, however stringent does not provide absolute protection
•   Vaccination against H5 avian influenza is required as an adjunct to biosecurity for U.S.egg-producing and turkey flocks in high-risk areas, subject to surveillance and certification of freedom from infection at the time of harvest or shipment of eggs

On May 16^th, the Brazil, Ministry of Agriculture reported a confirmed outbreak of highly pathogenic avian influenza (HPAI) in a broiler breeder farm with 17,000 birds located in the Municipality of Montenegro in the state of Rio Grande do Sul.  The farm concerned  Is contracted to Vibera Foods that has an association with Tyson Foods. The farm was rapidly depopulated and eggs were retrieved from hatcheries in the state in addition to facilities in Minas Gerais and Parana states.

The outbreak occurred concurrently with a diagnosis in a bird sanctuary in Sapucaia do Sul, approximately 30 miles from the index case. It is presumed that this facility with a lake and the index farm were infected  concurerently by migratory birds rather than by direct or indirect contact. Brazil has reported numerous diagnoses of avian influenza H5N1 in migratory birds along the Atlantic littoral but prior to the present report the infection has not occurred in commercial flocks. 

Predictably the report resulted in importing nations imposing embargos that will impact exports over the short term but may have longer term implications for both Brazil and world broiler trade if additional cases emerge or are disclosed especially if in multiple states. At the outset, the U.S. broiler industry should refrain from Schadenfreude, that unique Teutonic characteristic of deriving pleasure in someone else’s misfortune.  Brazil expects to resume exports in the near future since many customer nations are imposing only limited localized embargos and will follow the World Organization of Animal Health (WOAH) limitation of 28 days following completion of decontamination. Despite an optimistic statement from the USA Poultry and Egg Export Council concerning acquisition of new markets, U.S. integrators are currently unable to supply the whole birds and other products exported by Brazil.

Investigations subsequent to the Rio Grande do Sul outbreak failed to confirm HPAI in commercial farms located in Ipumirim in Santa Catarina and in Aguiarnopolis in Tocantins state. In addition a number of backyard flocks have yielded negative results.

To place the importance of Brazil in perspective, production in Brazil during 2025 will attain 15,250 million metric tons representing 14.4 percent of world output of 105.8 million metric tons, excluding feet. Production in Brazil is approximately 70 percent of projected U.S. output of 21.7 million metric tons.

Domestic consumption in Brazil will attain10.17 million metric tons in 2025, equivalent to a per capita value of 47.9 kg. assuming a population of 212 million.  According to USDA estimates, Brazil will export 5.3 million metric tons comprising a diverse range of RTC products in 2025 representing 37 percent of world trade and 1.7 times the volume of U.S. exports of 3.3 million metric tons, with 97 percent as leg quarters.  In 2024 Brazil exported 5.3 million metric tons valued at $9.94 billion at a unit price of $1,878 per ton.  In comparison the U.S. exported 3.3 million metric tons valued at $4.8 billion equivalent to a unit price of $1,459 per metric ton, reflecting a preponderance of relatively low-value leg quarters.

Exports of poultry products from Brazil including fertile eggs, breeding stock and RTC could be severely impacted given initial nationwide embargos by China, the E.U. and South Korea. Some nations recognizing their respective needs for chicken from Brazil have imposed state or regional embargos including Japan, Saudi Arabia and the United Arab Emirates among 17 nations.

The potential for disruption in trade from Brazil can be judged by 2024 exports:

During the first quarter of 2023 neighbors of Brazil including Argentina, Bolivia, Uruguay, Peru and Ecuador reported HPAI, strain H5N1 in wild birds, backyard flocks and some commercial farms.  In addition, Peru reported the death of over 1,000 sea lions and more than 65,000 migratory marine birds.  At this time, Brazil announced that suspect cases of HPAI in Rio Grande do Sul and Amazonas states were negative for the pathogen.  Producers in Brazil implemented extreme biosecurity measures to prevent infection, given the probability of introduction of the disease into commercial flocks by migratory birds following the pattern in north and central America and also in Asia and Africa.  By May 15^th 2023, Brazil had diagnosed 139 cases of HPAI in wild birds and subsistence poultry but inexplicably not on commercial farms as defined by the World Organization of Animal Health.

Carlos Favaro, the Minister of Agriculture for Brazil announced an emergency program to combat HPAI in August 2023 as a result of the extensive infection among migratory birds.  This was in recognition that any outbreak of HPAI in a commercial flock would trigger national, regional or state bans on shipments by importers including China and middle-East nations.

Brazil has remained free of reported avian influenza until the recently disclosed outbreak.

In mid-July 2024, Brazil suspended exports of all poultry products following mortality on a single table-egg production farm that was eventually diagnosed as velogenic, viscerotropic Newcastle disease (END) acquired following contact with wild birds.  After prompt depopulation and appropriate quarantine measures with surveillance, exports resumed with corresponding assurances to importers.  At the time it was questioned whether the specific case was in fact END since response to this infection would have been the same as an isolated case of HPAI. 

Brazil has a history of withholding information on diseases which may impact exports.  This is exemplified by Tom Vilsack, then USDA Secretary of Agriculture, addressing a formal letter to the Government of Brazil requiring improvement in detection and reporting of bovine spongiform encephalopathy. He stated “I urge Brazil in the strongest terms to continue its progress in streamlining timely animal disease reporting.”  The admonition by the USDA followed delays in reporting BSE with two cases of atypical infection diagnosed without prompt notification to the WOAH or importers.  Punitive import restrictions were imposed by trading partners on beef from Brazil following the revelation leading to the rejection of 140,000 metric tons of beef valued at $20 billion.  The fact that Brazil repeatedly failed to report cases of BSE raises the question of HPAI in commercial flocks.  The seven nations surrounding Brazil have reported H5N1 infection in free-living birds, backyard flocks or commercial farms but Brazil has only acknowledged extensive infection in migratory birds.

Conclusions can be derived from the most recent report of HPAI in a commercial flock in Brazil with implications for world trade:-

• HPAI is a panornitic occurring on all inhabited continents and including the Antarctic, affecting marine mammals and birds.  Accordingly, the question of “freedom” from highly pathogenic avian influenza and self-serving attempts to discriminate against exporters reporting localized or regional outbreaks is considered as factious.

• Avian influenza strain H5N1, clade 2.3.4.4b is endemic among migratory marine birds some species of which die of infection and others remain clinically unaffected carriers and disseminators of the pathogen.  Interaction among migratory marine birds and waterfowl through cohabitation on waterways and along coastal areas creates the risk of infection for susceptible commercial flocks.  Given that the pathogen can be transmitted by the aerogenous route over distances that may exceed one mile, even the most stringent biosecurity measures cannot assure absolute protection.

• The patchwork arrangement of trade agreements specifying embargos on entire nations, states or provinces or even regions are generally unjustified especially when importing nations report cases of HPAI in wild birds and free-living mammals and in their own commercial flocks.

• It is possible with PCR technology to confirm whether flocks of origin for exports are free of infection at the time of harvest allowing for certification under WOAH guidelines. 

• Given the geographic extent of both Brazil and the U.S. as the major exporting nations, imposition of countrywide bans is based either on ignorance of the epidemiology of HPAI or the misapplication of phytosanitary regulations to protect local industries.

• Despite the regularly updated recommendation of WOAH, there is an evident lack of uniformity in both adoption and recognition of diagnostic standards, certification and export regulations.  A point in question is compliance with the 28-day period following flock depopulation and decontamination following an outbreak of HPAI or END.  Some nations impose a 60-day embargo and in the case of China resumption of trade may be delayed for years. Harmonization and compliance with scientific standards is overdue.

• The overwhelming lesson from the ongoing panornitic, in progress since 2022, is that current methods of prevention are inadequate given the epidemiology of the infection.  Accordingly, the WOAH acceptance of preventive vaccination should be more extensively applied as an adjunct to biosecurity. Administration of commercially available effective vaccines should establish immune populations and would reduce inter-farm spread within a given area and will absolutely reduce expenditure on depopulation with accompanying indemnity.

Avian influenza should be regarded as the Newcastle disease of the 2020s.  During the 1970s END was in every way as catastrophic as HPAI and the infection is effectively suppressed in nations where a high level of immunity is achieved through diligent vaccination.

A diagnosis of H5N1 Highly Pathogenic Avian Influenza in a single flock in the State of Rio Grande do Sul has disrupted exports. Domestic consumers in Brazil may benefit, at least over the short term. Given a population of 212 million per capita domestic consumption is 48kg (106lb) and is equivalent to 65 percent of annual production.  

This will indirectly benefit the Government of President Luiz Lula da Silva, currently criticized for high food prices.  Over the past twelve months through April, food prices increased by 7.8 percent with poultry and eggs up by 12.3 percent.

Economists consider that the beneficial effect from increased domestic supply and hence, a decline in prices will be transitory.  If the outbreak of HPAI is contained, exports will resume.  In the event that the disease spreads, extensive depopulation may reduce availability.  The consequence will be an increase over existing prices for poultry meat, the staple animal protein for much of the population.

Despite the fact that migratory waterfowl are now established in their summer breeding grounds, outbreaks of highly pathogenic avian influenza (HPAI) persist.  The latest case in Maricopa County, AZ, involving a complex of 2.3 million hens indicates the persistence of infection.  Sequencing of the implicated virus will determine whether it is an avian-related D1.1 or a cattle B3.13 strain that will provide evidence of the source and route of infection.  The outbreak in Arizona was preceded by an April 30^th case involving 0.6 million hens in Aurora, SD. 

The severe losses that have occurred in 2025 to date include 33.2 million egg-producing hens on 60 farms or complexes. The incidence rate has obviously declined over the past three months but diagnosed outbreaks persist.  Growing turkeys are affected along with individual and obviously under-reported cases in backyard flocks.  Isolation of H5N1 avian influenza virus from live bird markets confirms the presence of undiagnosed supply flocks. Based on the absence of reports there is no certainty that USDA-APHIS is conducting traceback investigations to identify the source farms supplying live markets along the Atlantic seaboard.  The APHIS dashboard relating to detection of highly pathogenic avian influenza in wild birds updated on May 13, indicates isolation of H5N1 virus with a Eurasian genome from diverse states involving both waterfowl, black vultures  during Q1 and swallows during January.

Outbreaks among commercial and backyard flocks since February are indicated below:

This table confirms a declining incidence rate of cases among commercial flocks but unlike previous epornitics, outbreaks have persisted during late spring.

For 2025 to date, and based on an egg -producing population of 285 million hens, losses have attained:

Losses among caged hens are disproportionately high due to the effect of individual large complexes being affected.  Among the cage-free losses most were in large aviary complexes.  Organic and other cage-free hens in barns and in small commercial flocks were relatively unaffected despite regular feed delivery, egg collection and relatively lower levels of biosecurity as compared to in-line complexes.

Despite the USDA whack-a-mole approach to eradication and for the past three years as a program of control, highly pathogenic avian influenza has become endemic in the U.S. High risk areas include wetlands where migratory waterfowl congregate and along the four major flyways.  Although rapid flock depopulation has apparently reduced inter-flock transmission, it is obvious that virus is introduced into large complexes with power ventilation, whether caged or aviary housed, by the aerogenous route. Additional mechanisms include infected rodents, defects in biosecurity, transport and vaccination crews.

For the past three years, the industry has suffered from a lack of epidemiologic information relating to risk factors and specific routes of introduction of virus. It is known that APHIS in conjunction with federal and state wildlife agencies has conducted surveys on free-living mammals and birds in the vicinity of outbreaks on large complexes.  Results have yet to be published. These deficiencies have impeded the design and implementation of innovative methods of protection including vaccination.

Responding to high egg prices and escalating costs for control, the USDA announced a ‘five-pronged’ approach to address HPAI that effectively offered nothing new especially in the immediate and short-term. The program studiously avoided adoption of vaccination as an adjunct to biosecurity alone that clearly fails to offer absolute protection from infection.

The American Association of Avian Pathologists (AAAP) issued a position statement on bovine influenza on April 22^nd.  The release urges an immediate regulatory and industry response.

The AAAP notes the “narrow focus of testing restricted to lactating dairy cows that are moved interstate”.  It was suggested that surveillance should be intensified with specific reference to control areas surrounding positive herds.

The AAAP identified the absence of a national risk-based strategy incorporating scientific and epidemiologic principles that could be applied to reduce the spread of bovine influenza-H5N1.  Control strategies should incorporate a consideration of potential reservoir hosts including avian and mammalian species.

In the opinion of the AAAP, the USDA-APHIS has failed to investigate (or publish) pathways of transmission and risk factors despite emergence of H5N1 infection in the dairy industry as early as February 2024.  This negligence parallels the situation in commercial poultry and free-living birds.

As with poultry, it is evident that an effective vaccine, or series of vaccines, will be required to suppress and control infection.  Accordingly, it will be incumbent on USDA to establish trade agreements that will allow the limited use of H5 vaccine (in cattle as well as poultry) without compromising trade conducted in accordance with World Organization of Animal Health guidelines.

The AAAP emphasized the need for upgraded laboratory capability and resources necessary to maintain a program of surveillance and management of a comprehensive national vaccination program.  The Association urges federal funding for dedicated personnel and laboratory installations and equipment to initiate and sustain a control program consistent with an economically significant infection with a potential zoonotic implication.

In an April 22^nd position statement, the American Association of Avian Pathologists (AAAP) reviewed current realities relating to vaccination of commercial poultry.  At the outset, the Association recognizes that highly pathogenic avian influenza (HPAI) is endemic in the U.S. and has affected all sectors of the poultry industry and has now emerged in dairy herds. Concurrently infection has been diagnosed in terrestrial mammals, companion animals, and domestic wild birds in addition to migratory marine species and waterfowl.  The AAAP panel responsible for the position statement points to the susceptibility of commercial poultry species and the failure to suppress the epornitic in commercial flocks since emergence of infection in 2022.

A case is made for vaccination consistent with the advocacy by EGG-NEWS over the past three years. Creating immune populations, especially in high-risk areas, will reduce the incidence rate by minimizing the susceptibility of flocks that will continue to be exposed to infection.

The position statement recognizes technical limitations relating to vaccination, the most important of which is failure to elicit sterile immunity. Vaccinated flocks if infected will shed virus although at a lower rate and extensive mortality will be suppressed.

The major restraint to deployment of commercially available vaccines of various types relates to the potential for trade embargos despite the acceptance of vaccination as an adjunct to biosecurity by the World Organization of Animal Health (WOAH).  Vaccination against avian influenza using rHVT-H5 vaccines has proven effective in the Netherlands, Italy and Belgium.  Other studies have shown the protective effect of inactivated oil emulsion H5 vaccines in numerous countries as a primary immunogenic agent or as a booster.

It is possible to establish a program of surveillance over vaccinated flocks including quantifying immune response applying serology and to confirm freedom from HPAI using PCR.  Available technology and logistics can be applied to certify that export consignments derived from specified flocks are free of infection at the time of harvest.

Currently, trade in poultry products and especially broiler meat is subject to a patchwork of regulations imposed by importers. The most extreme restrictions demand nationwide bans or less onerous state or provincial embargos. The reactions of importers are based on outmoded traditional approaches to control of catastrophic infections, to protect domestic industries from competition or as an economic weapon.  The World Organization of Animal Health accepts vaccination as an adjunct to biosecurity if conducted in accordance with established surveillance.

With the advent of HPAI in Brazil, the infection can be regarded as a panornitic and accordingly, trade should be regulated in accordance with sound epidemiologic and scientific principles. It is now incumbent on exporting nations to press for adoption of uniform policies on diagnosis of avian influenza, control measures including vaccination, enforcement of regionalization and compartmentalization and harmonizing documentation.

USDA-APHIS has long labored under the misconception that HPAI can be eradicated by a program of sequential depopulation.  The Agency has not responded to the endemic status of the infection, involving seasonal reintroduction and dissemination of HPAI virus by migratory waterfowl, the potential reservoir status associated with terrestrial mammals and free-living domestic birds and the reality of aerogenous transmission. An inflexible adherence to past policy has impeded rational decisions relating to suppression of the infection. 

The justifiable concern by the broiler segment of the U.S. poultry industry relating to export embargos should not continue to restrict the deployment of avian influenza vaccination in high-risk areas for egg-production and turkey grow-out flocks.  The cost to the public sector for indemnity and logistics in addition to the burden borne by consumers far outweighs the potential benefits accruing to broiler exports.  The emergence of bovine influenza-H5N1 raises the issue albeit remote of the possibility of mutation to become a zoonotic pathogen capable of contagion. This eventuality should influence veterinary and public health agencies to implement protection of flocks by regulated and strategic vaccination, as advocated by the AAAP.

A recent article in the peer-reviewed journal Vaccines evaluated immunogenicity and efficacy of commercially available vaccines against highly pathogenic avian influenza virus, strain H5N1 in commercial geese raised for slaughter.  In general, an immune response was elicited by all vaccines evaluated, but durability of immunity was dependent on the type of the initial vaccination and the sequence of subsequent booster doses. Challenge under controlled conditions showed protection from clinical disease. Vaccination did not establish sterile immunity, although viral shedding was significantly lower compared to unvaccinated controls.

• Subunit vaccines containing H5 hemagglutinin antigen elicited seroconversion after a single dose and provided clinical protection. 
• A viral vector vaccine delivering genes encoding for H5 antigen resulted in a protective level of antibodies but required a booster for complete protection, and with some viral shedding following challenge.
• An RNA vaccine delivering nucleic acid sequences to stimulate antibody offered full clinical protection following initial vaccination with a booster.
• An inactivated oil emulsion vaccine containing native viral proteins stimulated seroconversion after a single dose but a booster enhanced antibody titer and protection.

The authors concluded that vaccination of geese, irrespective of the type of vaccine administered provided clinical protection and reduced viral excretion.  The results confirmed that vaccines could be incorporated into a program of HPAI prevention for geese that are highly susceptible and represent a significant industry in eastern Europe. 

The need for surveillance of vaccinated flocks was stressed to confirm attainment of protective levels of circulating antibody. Sequencing viral isolates is necessary to detect possible mutations associated with application of vaccination, recommended as an adjunct to biosecurity measure to protect growing geese and presumably other commercial poultry species.

A recent publication* evaluated transmission of H5N1 influenza among dairy cattle in the U.S.  The stochastic model based on 36,000 dairy herds in the continental U.S. attempted to quantify the extent of infection.  As of January 2025, when the article was submitted for peer review, the authors concluded that the infection is under-reported and that outbreaks will increase in Arizona and in Wisconsin.  The model suggests continuing cases associated with movement of dairy cattle coupled with inadequate programs of surveillance and restriction of transport.

Persistence of bovine influenza H5N1 in dairy cattle represents a danger to the poultry industry as confirmed by the 2024 outbreak of highly pathogenic avia influenza (HPAI) in western Michigan and the possibility of cases in Colorado and more recently in Arizona.  Failure to control and suppress bovine influenza will represent an ongoing risk to egg producers given movement of personnel between dairy herds and poultry flocks.  Common feed mills with non-dedicated delivery vehicles represents a risk of cross-industry infection. Proximity of large dairy and poultry farms could result in transmission of HPAI given the possibility of aerogenous spread of virus from large dairy installations to power-ventilated egg-production complexes.

*Rawson, T. et al A mathematical model of H5N1 influenza transmission in U.S. dairy cattle. Nature Communications doi.org10.1038/s41467-025-59554-z April 2025.