Summary
Report type: immediate notification
Started: 10 Sep 2022
Confirmed: 15 Sep 2022
Reported: 20 Oct 2022
Reason for notification: new strain in the country
Causal agent: highly pathogenic avian influenza virus
Serotype: H5N4
Nature of diagnosis: clinical, laboratory
This event pertains to a defined zone within the country.

Outbreak location: Teton County, Montana, USA
Started: 10 Sep 2022
Epidemiological unit: backyard
Animals affected:
Species / Susceptible / Cases / Deaths / Killed and disposed of /
Slaughtered or killed for commercial use / Vaccinated
Birds (domestic) / 2610 / - / - / 2610 / - / -

Affected population: A backyard producer. Clinical signs
included lethargy, depression, and death. State officials have
quarantined the affected [premises]. Depopulation was completed on 16
Sep 2022. Disposal was completed on 16 Sep 2022. Cleaning was
completed on 19 Sep 2022. Disinfection was completed on 19 Sep 2022.

Epidemiology
Source of the outbreak(s) or origin of infection: unknown or
inconclusive

Epidemiological comments: Highly pathogenic avian influenza (HPAI)
H5N4, Eurasian lineage goose/Guangdong clade 2.3.4.4b was confirmed on
a backyard producer premises in Teton County, Montana. This lineage is
highly pathogenic for poultry and is a reassortant of the initial
Newfoundland-like virus introduced December 2021 with North American
wild bird lineage segments PB2, PB1, NP, and NA. This is the 1st
confirmed case of HPAI H5N4 in poultry in the United States. NOTE:
this outbreak was first reported on follow-up report 31 for the
ongoing H5N1 event 4309 in the United States; the N-type was
characterized on 10/17/2022.

Control measures at event level
Domestic control measures applied: zoning, surveillance outside the
restricted zone, surveillance within the restricted zone, quarantine,
movement control

Control measures different from event level, additional measures:
disinfection; official disposal of carcasses, by-products, and waste;
stamping out

Diagnostic test results
Laboratory name and type / Species / Outbreaks / Test / First result
date / Last result date / Result
National Veterinary Services Laboratories (NVSL), Ames, Iowa / bird /
1 / gene sequencing / 15 Sep 2022 / 17 Oct 2022 / positive
National Veterinary Services Laboratories (NVSL), Ames, Iowa / bird /
1 / real-time reverse transcription polymerase chain reaction
(rRT-PCR) / 15 Sep 2022 / 17 Oct 2022 / positive