On April 24th the USDA announced mandated testing for HPAI before interstate movement of dairy cattle. The Federal order became effective April 29th. Cattle to be moved across state lines must be tested to confirm freedom from influenza-A virus using approved sampling and assays at an accredited Animal Health Laboratory Network facility. The requirement for testing prior to interstate movement does not address the situation under which dairy animals can be assigned to an abattoir within state, representing the risk of horizontal transmission and possible exposure of workers to H5N1 virus from infected carcasses. It is noted that dairy animals represent seven percent of all beef produced in the U.S. predominantly in ground form.
The emergence of H5N1 in dairy herds with close to 40 identified herds in nine states, is based on the self-reported presence of clinically affected cows. Obviously at the present time the prevalence and distribution of bovine influenza-H5N1 is unknown. A recent survey detected 58 positive PCR assays out of 150 samples of commercial milk from ten states. This procedure identified H5 viral RNA but not viable virus. This finding suggests widespread infection with excretion of virus by clinically unapparent cases in herds. The saving grace for the milk industry and consumers is that pasteurization will effectively inactivate any H5N1 virus shed by viremic but clinically unaffected cows.
Wastewater assays* have indicated high levels of H5 influenza RNA in 59 out of 190 plants in Texas where bovine influenza H5N1 was initially confirmed. It would be instructive to determine whether discarded milk contains viable H5N1 since this factor might have contributed to the apparent spike in recovery.
The USDA has initiated investigations to monitor the presence of bovine influenza-H5N1 in beef. Paralleling the recovery of RNA sequences from milk, APHIS will assay ground beef from retail stores and FSIS will screen muscle tissue from culled dairy cows. It will be important to determine whether bovine influenza-H5N1 has spread to cow-calf and feedlot operations and if avian reservoirs have disseminated infection beyond dairy cows.
Predictably the USDA, CDC and production associations representing milk production have circled the wagons and have justifiably confirmed a low (or more realistically a
negligible) risk of infection from consuming pasteurized milk. This is a scientifically supported position but release of data from intensive field and molecular epidemiologic investigations will be necessary to allow agencies to make valid and substantiated comments and recommendations.
Dr. Katelyn Jetelina, an epidemiologist with an extensive following, noted that, “A communication void will be filled with confusion, mistrust and misinformation.” Based on our collective experience during the COVID pandemic, she correctly notes that consumers have questions and if they can’t find authoritative answers, they will turn to less credible sources resulting in misinformation and malicious rumor. She noted, “During an outbreak top-down credible and consistent communication is necessary. Equally important is actively equipping trusted messengers including mass media, scientists, physicians and community leaders so that they can communicate from the bottom up.”
The emergence of bovine influenza-H5N1 has implications for exports. Columbia has imposed restrictions on both beef and poultry from entire states reporting bovine influenza-H5N1. Countries wishing to protect domestic industries or those intent on imposing embargoes for political purposes will soon follow the initiative of Columbia. It is hoped that concern over embargoes will not restrain surveillance to determine the extent and distribution of bovine influenza-H5N1 among both dairy and possibly the beef segments of production. At the present time, swineherds that have been tested have proven to be negative but surveillance in this industry is necessary given the susceptibility of hogs to avian and mammalian influenza viruses.
USDA has issued directives concerning detection of possible occupational exposure on both live animal operations and packing facilities. The current circulating H5N1 is susceptible to available antiviral medication that has been stockpiled. Candidate H5 vaccines could be rapidly produced using conventional or mRNA-nanoparticle technology. We may be a long way from a zoonotic infection but our recent experience with COVID and warnings regarding the potential for mutations in large susceptible (ie unvaccinated) poultry flocks should be heeded.
*Wolfe, M.K. et al Detection of hemagglutinin H5 influenza A virus sequences in municipal wastewater treatment plants with increases in influenza A in spring 2024. MedRx iv. doi.org/10.1101/2024.04.26.24306409