#18,892
Although quickly overshadowed by the news of the spillover of HPAI H5N1 into Texas and Kansas dairy herds (announced only 3 days later), just over 18 months ago we saw the first confirmed infection of goats with H5N1 in the United States (see Minnesota BOAH Statement On HPAI H5N1 Infected Goat Kids).
These goats were being raised on a `mixed species' farm, which was then experiencing an outbreak of H5N1 in ducks and chickens.These were the first detections of clade 2.3.4.4b H5N1 in ruminants in the United States, although cattle have previously been successfully infected in the laboratory with older clades (see A Brief History Of Influenza A In Cattle/Ruminants).
Has HPAI ever been detected in small ruminants?
In March 2024, USDA’s National Veterinary Services Laboratories (NVSL) confirmed HPAI in very young goat kids on a Minnesota farm that also had poultry infected with HPAI. The goats shared the same pasture and water source with the infected chickens and ducks before they were depopulated, while kidding. This situation led to the newborn goats being exposed to high levels of virus. Adult goats on the premises tested negative for the virus.
NVSL identified the virus infecting the goats and poultry on the farm was B3.6. This is a very common genotype that is circulating in our North American wild bird flyways and has sporadically infected poultry flocks in 2023 and 2024. The virus causing the disease in dairy cattle is B3.13.
Two months later we learned that Alpacas - again on a `mixed-species farm' - in Idaho, had been infected with HPAI H5N1 (see USDA: HPAI H5N1 Detected In Alpacas).
This time, however, it was from the `bovine' B3.13 genotype, which had spilled over into the farm's poultry.
Since then we've seen serological evidence of HPAI exposure in goats and sheep in Pakistan, last March the UK's Defra reported H5N1 Detected In Domestic Sheep with Mastitis, and in May; serological evidence of H5N1 in sheep in Norway.
Despite these findings, surveillance for HPAI H5 in cattle, sheep, goats, and other livestock is passive; meaning mild or asymptomatic carriage is unlikely to be detected.
Although nearly 1,100 herds have been reported as infected since March of 2024, the USDA's Dairy Herd Status Program website only shows 124 herds (out of an estimated 36,000) from 21 states enrolled in the voluntary herd monitoring program.
For nearly a year it was assumed that only the `bovine' B3.13 genotype was capable of infecting dairy cows. But in February of this year two states reported outbreaks of genotype D.1 in dairy cows (note: we've also seen genotype D1.2 in pigs).
Recent studies (see Nature: A Mathematical Model of H5N1 Influenza Transmission in US Dairy Cattle) suggest that significant under-reporting of H5N1 in dairy herds is likely.
To put it kindly, in the United States - and around the globe - surveillance and testing of livestock is far from optimal. Spillovers that were once thought unlikely, or are now considered rare, could actually be far more common than we know.
All of which brings us to a recent study, published in Cell Reports, which finds that goats are highly susceptible to HPAI H5N1, and that they can transmit it to suckling goats.
Due to its length, and technical nature, I've only reproduced the abstract and some excerpts. Follow the link to read it in its entirety. I'll have a bit more after you return.
Dairy cow- and avian-origin clade 2.3.4.4b H5N1 induce severe mastitis in lactating goats and transmission to suckling goats
Tamiru N. Alkie1 ∙ Carissa Embury-Hyatt1 ∙ Anthony V. Signore1 ∙ … ∙ Samira Mubareka7,8 ∙ Richard Webby9 ∙ Yohannes Berhane yohannes.berhane@inspection.gc.ca …
Download PDF
Highlights
- Cow- and avian-origin A(H5N1) caused severe mastitis in goats
- Infected goats shed viruses in milk, transmitting A(H5N1) to suckling kids
- Both viruses infected goat respiratory and mammary cells, which express sialic acid receptors
- Findings show underestimated A(H5N1) risk in ruminants, urging better livestock surveillance
Summary
The emergence of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b has led to unprecedented spillover and spread among US dairy cows, raising concerns about transmission to other ruminants.
We inoculated two groups of lactating goats via intramammary and respiratory routes with Cow-H5N1 (genotype B3.13) or avian-H5N1 (genotype B1.2) virus. Both groups developed severe clinical mastitis and shed viruses in milk, resulting in transmission to suckling kids.
Viral RNA was detected in nasal and oral swabs and various tissues, and virus-neutralizing antibodies were present in serum, milk, and bronchoalveolar lavage fluid. In vitro, both viruses replicated efficiently in goat respiratory and mammary epithelial cells. Mammary tissue expresses both α2,3- and α2,6-linked sialic acid receptors.
These findings demonstrate that goats are highly susceptible to H5N1 infection, with mammary tropism facilitating transmission to offspring, and underscore the need for increased surveillance in ruminant livestock.
(SNIP)
The detection of higher titers of infectious virus in milk from naturally infected dairy cows1 raises concerns regarding the potential zoonotic transmission through the consumption of unpasteurized milk. Standard pasteurization temperature effectively inactivate the A(H5N1) virus in milk.45,46 However, experimental studies involving raw infected cow milk in animal models have shown severe outcomes.47,48
Goat milk is an essential part of the diets in many Asian and European countries, particularly in India, Pakistan, Bangladesh, Turkey, and Italy, which are major producers and consumers, even though it is not consumed in large quantities worldwide. Acutely A(H5N1)-infected lactating goats produce milk with high virus loads that can spread to vulnerable animals or infect humans who drink unpasteurized milk.
Additionally, handling infected goats may present occupational health risks.
As the outbreaks of HPAI in dairy cows continue and new genotypes with mammalian adaptive mutations emerge, the inclusion of lactating goats or sheep in HPAI surveillance programs seems sensible. The tropism of clade 2.3.4.4b viruses for mammary glands is likely due to the expression of specific sialic acid receptors. The duplicability of clinical disease in lactating goats after A(H5N1) infection suggests their potential use as a model for studying HPAI pathogenesis and vaccine efficacy testing against these viruses. Goats offer several advantages, including feasibility and relatively shorter gestation periods.
Despite constant calls for more surveillance, aggressive testing, and the timely sharing of information (see here, here, here, here, here, here, and here), there are few signs that these pleas are being taken seriously by most governments, agencies, or stakeholders.
The world continues to treat the spread of HPAI as more of an economic or political concern, than a potential public health threat.
