Treyfish
Moderator
2024 Highly Pathogenic Avian
Influenza (H5N1) - Michigan
Dairy Herd and Poultry Flock
Summary
Epidemiological Investigations of HPAI H5N1 Genotype B3.13 in
Michigan Dairy Herds and Poultry Flocks: Observations on viral
spread between premises and mitigation recommendations
June 9, 2024
1. Executive Summary
Highly Pathogenic Avian Influenza (HPAI) H5N1 viral infection in dairy cattle was first confirmed on a Texas dairy
premises on March 25, 2024. Dairy cattle from an HPAI affected dairy premises in Texas – non-clinical and
undetected at the time of the cattle movement – were shipped to Michigan, arriving on March 8, 2024. Clinical
signs were first observed in the premises’ resident cattle on March 20, 2024. On April 1, 2024, a commercial
poultry premises reported clinical signs associated with HPAI. The flock was confirmed infected on April 2, 2024.
Whole genome sequencing (WGS) of viruses from the dairy and poultry premises identified Eurasian lineage
goose/Guangdong clade 2.3.4.4b, genotype B3.13 on both premises and suggests likely indirect transfer of virus
from the dairy premises to the poultry premises.
In early April 2024, the Michigan Department of Agriculture and Rural Development (MDARD) invited a USDA
Epidemiological Strike Team into Michigan to investigate the links between HPAI affected dairy premises and
evidence of spillover into poultry premises. This report summarizes the findings from field epidemiological
investigations of disease spread between premises for 15 dairy herds and 8 poultry flocks confirmed with HPAI
genotype B3.13 in Michigan.
After interstate animal movement initially introduced the HPAI genotype B3.13 virus into a Michigan dairy,
continued disease transmission within the state is determined to be multifactorial. Transmission between farms is
likely due to indirect epidemiological links related to normal business operations such as numerous people,
vehicles, and other conveyances frequently moving on and off the affected dairy premises, with many of these
indirect links shared between premises. Importantly, disease spread due to independent introduction of the virus
onto dairy or poultry premises from migratory waterfowl is not supported based on both genomic and
epidemiological data analysis.
Key findings identified to date and potential risk factors for local transmission include:
• Shared personnel between premises
o 20% of affected dairies’ employees and 7% of dairies’ employees family members work on other
dairy premises
o 7% of affected dairies’ employees also work on poultry premises; 13% of affected dairies’
employees have family members who work on poultry premises
o 31% of dairies have employees who own livestock or poultry at their personal residence
• Shared vehicles between premises
Page 2 of 10
o 62% of affected dairy premises use shared vehicles to transport cattle, with only 12% of premises
cleaning vehicles before use
• Frequent visitors on/off premises
o 100% of affected dairy premises have regular visits by veterinarians, nutritionist/feed consultant,
and/or contract haulers (e.g., cattle or manure); the majority of these visitors have direct contact
with cattle
o 40% of affected dairy premises have regular visits for deadstock removal, with 20% having direct
contact with cattle
53% of affected dairies utilized the same deadstock removal company and 40% had
animals removed from the premises by that company within 30 days prior to clinical
onset
o Milk haulers visit dairy premises, on average, 34 times within a 30-day time period
93.3% of affected dairy premises are part of the same milk co-op with at least one other
affected dairy premises within the state (i.e., only one of the affected dairy herds is part
of a milk co-op that none of the other 14 affected dairy herds belong to)
Based on the epidemiological findings, the majority of links between affected dairy premises, and between dairy
and poultry premises, are indirect from shared people, vehicles, and equipment. As such, HPAI disease spread
between dairy and poultry premises can be mitigated by identifying potential interconnections between
operations (people, conveyances, etc.) and increasing biosecurity practices on all premises and associated animal
businesses (e.g., milk haulers, deadstock/contract haulers and other shared vehicles/trailers between premises,
livestock markets). Identifying as many affected herds as possible will assist in assessing the scope of the event
and allow decision-makers to better manage the response.
2. Background
After more than a month of investigations into dramatically decreased milk production and changes in milk
composition in dairy herds in Texas, on March 25, 2024, the cause was confirmed to be the highly pathogenic
avian influenza (HPAI) H5N1 virus of Eurasian lineage goose/Guangdong clade 2.3.4.4b, genotype B3.13. The HPAI
H5N1 virus is detected at high levels in milk of infected cows and at lower levels in nasal swabs and urine of
infected cows; manure does not appear to be a meaningful viral source and is unlikely to transmit the virus.
Whole genome sequencing (WGS) analysis suggests an initial single spillover event of the virus from wild birds to
dairy cattle, most likely occurring in the Texas panhandle in December 2023, with onward spread of the virus to
eight other states (Nguen et al, 2024).
On March 29, 2024, HPAI was confirmed on a Michigan dairy cattle premises with disease introduction traced
back to movement of lactating dairy cattle from an affected dairy premises in Texas which was non-clinical at the
time of animal movement. The Texas dairy herd was detected shortly after cattle movement into Michigan
occurred when the Texas herd displayed clinical signs. On April 2, 2024, HPAI was confirmed on a commercial
poultry premises in Michigan; WGS supports this premises was infected with the same B3.13 genotype as the first
Michigan affected dairy with directional movement of the virus from the dairy premises to the poultry premises.
On April 10, 2024, a team of USDA epidemiologists (Epidemiological Strike Team) was invited by the Michigan
Department of Agriculture and Rural Development (MDARD) to deploy to Michigan to rapidly investigate
detections of HPAI in Michigan dairies with evidence of spillover into poultry premises. A USDA Incident
Management Team (IMT) was also deployed to Michigan at the same time to support the state’s HPAI poultry
response; epidemiologists from both groups communicated daily during deployment and regularly after
demobilization to discuss details about affected premises.
Page 3 of 10
This report summarizes the findings from the Strike Team’s field epidemiological investigations of disease spread
between premises for 15 dairy herds and 8 poultry flocks confirmed with HPAI H5N1 genotype B3.13 in Michigan.
3. Epidemiologic Investigation Methods…:tiphat:
lots more
https://www.aphis.usda.gov/sites/default/files/hpai-h5n1-dairy-cattle-mi-epi-invest.pdf
Influenza (H5N1) - Michigan
Dairy Herd and Poultry Flock
Summary
Epidemiological Investigations of HPAI H5N1 Genotype B3.13 in
Michigan Dairy Herds and Poultry Flocks: Observations on viral
spread between premises and mitigation recommendations
June 9, 2024
1. Executive Summary
Highly Pathogenic Avian Influenza (HPAI) H5N1 viral infection in dairy cattle was first confirmed on a Texas dairy
premises on March 25, 2024. Dairy cattle from an HPAI affected dairy premises in Texas – non-clinical and
undetected at the time of the cattle movement – were shipped to Michigan, arriving on March 8, 2024. Clinical
signs were first observed in the premises’ resident cattle on March 20, 2024. On April 1, 2024, a commercial
poultry premises reported clinical signs associated with HPAI. The flock was confirmed infected on April 2, 2024.
Whole genome sequencing (WGS) of viruses from the dairy and poultry premises identified Eurasian lineage
goose/Guangdong clade 2.3.4.4b, genotype B3.13 on both premises and suggests likely indirect transfer of virus
from the dairy premises to the poultry premises.
In early April 2024, the Michigan Department of Agriculture and Rural Development (MDARD) invited a USDA
Epidemiological Strike Team into Michigan to investigate the links between HPAI affected dairy premises and
evidence of spillover into poultry premises. This report summarizes the findings from field epidemiological
investigations of disease spread between premises for 15 dairy herds and 8 poultry flocks confirmed with HPAI
genotype B3.13 in Michigan.
After interstate animal movement initially introduced the HPAI genotype B3.13 virus into a Michigan dairy,
continued disease transmission within the state is determined to be multifactorial. Transmission between farms is
likely due to indirect epidemiological links related to normal business operations such as numerous people,
vehicles, and other conveyances frequently moving on and off the affected dairy premises, with many of these
indirect links shared between premises. Importantly, disease spread due to independent introduction of the virus
onto dairy or poultry premises from migratory waterfowl is not supported based on both genomic and
epidemiological data analysis.
Key findings identified to date and potential risk factors for local transmission include:
• Shared personnel between premises
o 20% of affected dairies’ employees and 7% of dairies’ employees family members work on other
dairy premises
o 7% of affected dairies’ employees also work on poultry premises; 13% of affected dairies’
employees have family members who work on poultry premises
o 31% of dairies have employees who own livestock or poultry at their personal residence
• Shared vehicles between premises
Page 2 of 10
o 62% of affected dairy premises use shared vehicles to transport cattle, with only 12% of premises
cleaning vehicles before use
• Frequent visitors on/off premises
o 100% of affected dairy premises have regular visits by veterinarians, nutritionist/feed consultant,
and/or contract haulers (e.g., cattle or manure); the majority of these visitors have direct contact
with cattle
o 40% of affected dairy premises have regular visits for deadstock removal, with 20% having direct
contact with cattle
53% of affected dairies utilized the same deadstock removal company and 40% had
animals removed from the premises by that company within 30 days prior to clinical
onset
o Milk haulers visit dairy premises, on average, 34 times within a 30-day time period
93.3% of affected dairy premises are part of the same milk co-op with at least one other
affected dairy premises within the state (i.e., only one of the affected dairy herds is part
of a milk co-op that none of the other 14 affected dairy herds belong to)
Based on the epidemiological findings, the majority of links between affected dairy premises, and between dairy
and poultry premises, are indirect from shared people, vehicles, and equipment. As such, HPAI disease spread
between dairy and poultry premises can be mitigated by identifying potential interconnections between
operations (people, conveyances, etc.) and increasing biosecurity practices on all premises and associated animal
businesses (e.g., milk haulers, deadstock/contract haulers and other shared vehicles/trailers between premises,
livestock markets). Identifying as many affected herds as possible will assist in assessing the scope of the event
and allow decision-makers to better manage the response.
2. Background
After more than a month of investigations into dramatically decreased milk production and changes in milk
composition in dairy herds in Texas, on March 25, 2024, the cause was confirmed to be the highly pathogenic
avian influenza (HPAI) H5N1 virus of Eurasian lineage goose/Guangdong clade 2.3.4.4b, genotype B3.13. The HPAI
H5N1 virus is detected at high levels in milk of infected cows and at lower levels in nasal swabs and urine of
infected cows; manure does not appear to be a meaningful viral source and is unlikely to transmit the virus.
Whole genome sequencing (WGS) analysis suggests an initial single spillover event of the virus from wild birds to
dairy cattle, most likely occurring in the Texas panhandle in December 2023, with onward spread of the virus to
eight other states (Nguen et al, 2024).
On March 29, 2024, HPAI was confirmed on a Michigan dairy cattle premises with disease introduction traced
back to movement of lactating dairy cattle from an affected dairy premises in Texas which was non-clinical at the
time of animal movement. The Texas dairy herd was detected shortly after cattle movement into Michigan
occurred when the Texas herd displayed clinical signs. On April 2, 2024, HPAI was confirmed on a commercial
poultry premises in Michigan; WGS supports this premises was infected with the same B3.13 genotype as the first
Michigan affected dairy with directional movement of the virus from the dairy premises to the poultry premises.
On April 10, 2024, a team of USDA epidemiologists (Epidemiological Strike Team) was invited by the Michigan
Department of Agriculture and Rural Development (MDARD) to deploy to Michigan to rapidly investigate
detections of HPAI in Michigan dairies with evidence of spillover into poultry premises. A USDA Incident
Management Team (IMT) was also deployed to Michigan at the same time to support the state’s HPAI poultry
response; epidemiologists from both groups communicated daily during deployment and regularly after
demobilization to discuss details about affected premises.
Page 3 of 10
This report summarizes the findings from the Strike Team’s field epidemiological investigations of disease spread
between premises for 15 dairy herds and 8 poultry flocks confirmed with HPAI H5N1 genotype B3.13 in Michigan.
3. Epidemiologic Investigation Methods…:tiphat:
lots more
https://www.aphis.usda.gov/sites/default/files/hpai-h5n1-dairy-cattle-mi-epi-invest.pdf