H5N1: A Veterinary Guide

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H5N1: a veterinary guide to the emerging threat

Brazil, the world’s largest chicken exporter (accounting for 35% of global trade), has just been hit by a major H5N1 outbreak at a Tyson-backed farm—prompting both the EU and China to impose 60-day import bans. While we’ve tracked the bird-flu emergency before, the scale of HPAI H5N1 this season demands a deeper dive: since October 2024, nearly 1,200 commercial-poultry outbreaks and over 1,400 wild-bird infections have been logged worldwide through April 2025. It’s high time for a Weekend Rounds–style playbook on this resurging threat.

Global Outbreak Snapshot

Since 2020, clade 2.3.4.4b HPAI H5N1 has spread to every continent except Australia, with 1,200 poultry-farm outbreaks and 1,400 wild-bird cases between October 2024 and April 2025. In December, California declared a state of emergency after detecting H5N1 in wild waterfowl; egg prices in the U.S. soared, then briefly dipped in early May. As the US looked looked abroad for egg providers Brazil’s first large-scale farm infection in Rio Grande do Sul triggered immediate bans from the EU, China, and Argentina, spotlighting how quickly trade can be affected by a global pandemic.

At the same time, policy missteps have raised eyebrows—like the White House’s reported use of 30,000 eggs for an Easter event—and federal cuts to FDA staff responsible for outbreak monitoring have thinned the ranks of those who once formed the first line of defense (1, 2).

Cross-Species Spill-Over Risks

Recent reports underscore H5N1’s capacity to jump species barriers:

• Dairy cattle: Bulk-milk surveillance in multiple states uncovered “silent” infections. Veterinarians caring for herds have tested positive for H5N1 antibodies—often after treating animals without eye or respiratory protection.

• Domestic cats & wildlife: Cases in pet cats, bobcats, and other carnivores present rapidly progressing respiratory and neurologic signs (dyspnea, tremors, seizures) with high fatality rates.

• Pinnipeds: H5N1 has been identified in seals in Antarctica raising the risk of global pandemic.

• Humans: While overall risk remains low, those working closely with infected animals face increased exposure—echoing early COVID-19 zoonotic concerns.

Clinical Red Flags & Diagnostics

Key Signs

• Birds: Acute respiratory distress, neurologic signs, sudden death

• Mammals: Fever, ataxia, neurologic disturbances

Testing Protocols

• Poultry: Oropharyngeal and cloacal swabs

• Cattle: Nasal/oral swabs or bulk-milk PCR

• Felines: Combined nasal/rectal swabs

In the USA, coordinate samples with your state animal-health lab and the USDA’s National Animal Health Laboratory Network for prioritized turnaround.

Biosecurity & Clinic Protocols

• Scenario-Based Planning: AAHA’s new guide walks practices through zoning contaminated areas, donning/doffing PPE, scripted client communications, and staff-health monitoring drills.

• Risk-Based PPE: Use full isolation and enhanced PPE for suspected H5N1 cases; revert to standard precautions for asymptomatic or low-risk patients, per AAHA’s tiered framework.

Reporting & Regulatory Must-Dos

• Report immediately any suspected avian H5 or H7 case to USDA APHIS and your state animal-health official (hotline: 866-536-7593).

• Feline cases are reportable in many jurisdictions—follow Colorado’s guidance for separate exam rooms and strict PPE when handling exposed cats.

• Canadian vets should consult their provincial SARI (Severe Acute Respiratory Infections) protocols and local reporting requirements.

• For our international readers, be aware of reporting guidelines in your region during this emerging threat.

Vaccines & Therapeutics on the Horizon

• Animal vaccines: Preclinical H5N1 vaccines offer 100% protection in poultry and mammal models; commercialization efforts are underway for broader use in dairy herds.

• Antiviral research: While no FDA-approved antivirals exist yet for veterinary patients, supportive care remains crucial—and investigational therapies may emerge soon.

Lessons from COVID-19

• Early detection & data sharing: Rapid, transparent collaboration between wildlife, livestock, and human-health sectors proved lifesaving in 2020. Strengthening these One Health networks now can blunt H5N1’s trajectory.

• Staff resilience: Just as burnout and PPE shortages hampered COVID-19 efforts, USDA staffing cuts threaten our diagnostic capacity. Prioritize cross-training and mental-health support to maintain rapid-response readiness.

Veterinarians are the linchpin in animal and public health. Your vigilance, protocols, and clear communication will determine whether H5N1 remains a contained outbreak or escalates into our next global challenge. Stay prepared—and stay safe.

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Gene-Edited Pigs Gain PRRS Resistance

The FDA has granted conditional approval for a gene-editing technology that knocks out the CD163 receptor in pigs, rendering them fully resistant to Porcine Reproductive and Respiratory Syndrome (PRRS). Developers at several land-grant universities used CRISPR/Cas9 to breed PRRS-immune pigs without off-target effects, marking a potential sea change for an industry that loses an estimated $1.2 billion annually to PRRS between 2016–2020. Read more on DVM 360.

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Phages Edge In as Antibiotic Alternatives

As antimicrobial resistance tightens its grip, veterinary researchers are revisiting bacteriophages—viruses that infect bacteria—as targeted, self-amplifying therapeutics. VIN reports that multiple veterinary centers have launched pilot studies using phage cocktails against MDR Staphylococcus and E. coli in equine and companion-animal infections. Early results show >90% kill-rates in biofilm models, offering hope for chronic-wound and otitis cases unresponsive to conventional antibiotics. Read the whole story on Vin News.

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Quick Hits

Here are some of the other stories that caught our eye and we're following this week from around the veterinary world and animal kingdom: