Mammary glands in several livestock species can harbor the H5N1 avian influenza virus, according to a new study from Iowa State University that researchers say points to a need for broader monitoring of farm animals beyond the dairy cattle herds where the virus has circulated in recent years.
The finding expands the range of species that may be susceptible to infection and suggests that current surveillance programs, which have focused heavily on poultry and dairy cows, could be missing transmission pathways in other animals. Researchers involved in the work say the results underscore the importance of widening testing and monitoring efforts across livestock operations to catch potential outbreaks earlier.
Avian influenza has long been a concern for poultry producers, but the virus's jump into mammals has alarmed public health officials because it increases the opportunities for the pathogen to adapt in ways that could eventually pose a greater risk to humans. Since the current H5N1 outbreak began affecting dairy herds in the United States, scientists have been working to understand how the virus spreads between animals and what tissues it can infect.
The Iowa State study adds to that effort by identifying mammary gland tissue as a potential site of viral replication in multiple livestock species. That finding is significant because milk and milking equipment have already been implicated in the spread of the virus within and between dairy farms. If other animals can also carry the virus in their mammary tissue, the implications for farm biosecurity and worker safety could be broader than previously understood.
Researchers say the results do not mean that all livestock are equally susceptible or that the virus is spreading widely in every species examined. Rather, the study highlights the need for more comprehensive surveillance so that public health and agriculture officials can detect infections when and where they occur. Without expanded testing, cases in less-monitored animals could go unnoticed, giving the virus more chances to circulate and potentially change.
The study comes as health authorities continue to monitor H5N1 infections in dairy workers and poultry farms across the country. While human cases have so far been relatively mild and no sustained person-to-person transmission has been documented, each new infection in a mammal is viewed as an opportunity for the virus to mutate. That makes understanding which animals can carry the virus and where in the body it replicates a priority for researchers.
Iowa State's findings are likely to inform discussions among veterinarians, public health agencies, and agricultural producers about how to strengthen surveillance systems. Such systems would need to cover not only dairy cattle and poultry but also other livestock that may come into contact with infected animals or contaminated environments. The researchers stress that early detection remains one of the most effective tools for preventing wider outbreaks.
For now, the study serves as a reminder that influenza viruses can move in unexpected ways through agricultural systems. As H5N1 continues to evolve, scientists say that keeping a close watch on a wider range of species will be essential to protecting both animal and human health.
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