Outbreak Investigation Report on Avian Influenza in British Columbia, 2014
3. Overview of Outbreak
3.1. Initial Detection
On December 1st, 2014, the Chief Veterinary Officer for Canada (CVO) received notification from the British Columbia (BC) CVO of an NAI suspect on two farms: a broiler breeder farm in Chilliwack (IP1) and a commercial turkey farm in Abbotsford (IP2).
Preliminary testing of samples from the two farms (IP1 and IP2) at the BCMAGRI-AHC in Abbotsford confirmed the presence of H5 avian influenza. The CFIA immediately quarantined the two infected farms.
On December 2, 2014 the CFIA established an incident command post (ICP) in the Animal Health District Office in Abbotsford, BC.
Under official quarantine, movement of poultry, poultry products and by-products on and of farms was not allowed. Farms located within 10 km of the IPs were identified through the provincial Premises ID program.
On December 2nd and 3rd, CFIA staff collected additional samples from IP1 and IP2 for diagnosis as per the NAI HSP. Blood, swab and tissue samples from birds on IP1 and IP2 were sent to the NCFAD for confirmatory testing on December 3rd, 2014.
On December 4th, based on the results from partial sequencing of the virus, the NCFAD confirmed the strain associated with the outbreak as being a highly pathogenic avian influenza H5N2.
The CFIA activated an Emergency Operations Centre (EOC) in collaboration with the province of BC as a Joint Emergency Operations Centre (JEOC), which was co-located with an Incident Command Post (ICP) in the Abbotsford District Office. A national EOC (NEOC) was activated in Ottawa, ON.
3.2. Findings on Infected Premises 1
This multi-staged chicken broiler breeder operation located near Chilliwack, BC is composed of five barns housing the following number of birds:
- Barn 1 (B1) housed 7,000 hens and 1,000 roosters aged 25 weeks;
- Barn 2 (B2) housed 4,500 hens and 300 roosters aged 51 weeks; and
- Barns 3-5 were empty.
On Friday November 28th, 2014, the owner noticed 16 dead birds in B1. These roosters, a.k.a. 'spiking' roosters, were being raised to be sold to other producers. On Saturday November 29th, the owner noted 30 dead birds in B1 and became concerned about the cause.
On the morning of Sunday, November 30th, the farmer noticed 88 dead birds and contacted his veterinarian. The farmer submitted ten carcasses for post mortem and incinerated all remaining carcasses on site. The post-mortem findings were inconclusive, with only non-specific signs of disease present on gross pathology: facial oedema, conjunctivitis, with tracheal and pulmonary congestion.
On December 1st, the producer noted approximately 450 dead birds during his morning walk-through. These birds were removed from B1 to an empty barn where they were secured using a heavy-duty tarp. The private veterinarian collected tracheal and cloacal swabs from live birds in B1 for submission to BCMAGRI-AHC. The tissue samples from the post mortem of the day before were also submitted to the BCMAGRI-AHC.
BCMAGRI-AHC reported results the same day (December 1st) as H5 positive on PCR, with gross lesions compatible with HPAI. The CFIA contacted the owner to inform him of the presumptive positive result. The farm was placed under official quarantine later that evening.
Field epidemiological investigations, were conducted on IP1. It was determined that the HPAI virus isolated from IP1 was likely introduced as a result of an indirect exposure to a wild bird reservoir and to local environmental contamination. Ducks had been seen around the farm. Weather conditions may have increased the number of wild waterfowl and rodents seeking shelter, possibly increasing the likelihood of these animals serving as vectors of the AI virus. In addition, wild waterfowl were observed in the draining ditch on the farm. The owners were away from November 4th to 20th, leading to an increased potential for possible biosecurity lapses by employees.
The movement tracing investigation identified two high-risk contact farms in the city of Abbotsford. These two farms (IP3 and IP4) had received spiking roosters on November 28th and 27th from IP1 and developed clinical signs on December 3rd and 2nd. They were both quarantined and sampled on December 3rd.
3.3. Findings on Infected Premises 2
This commercial turkey operation located near Abbotsford, BC is composed of three barns that housed the following number of birds by age:
- B1: 11,000 males and 3,000 females, aged 2 weeks
- B2: 3,000 turkey hens, aged 12 weeks
- B3: 11,000 turkey toms, aged 12 weeks
The first clinical sign noted was a decrease in water consumption in B3 on November 26th, followed by increased mortality over the next few days, and massive mortality on December 1st:
- November 27th: 18 toms dead
- December 1st: 60 - 70% toms dead
- December 3rd: almost all birds were dead in B3
On November 28th, the farmer called his private veterinarian. The veterinarian went into B3 only. He noted that the birds were bright, alert, and responsive. He performed on-site post-mortems of five dead birds, plus one sick bird. On necropsy, the trachea and lungs looked normal; there was splenomegaly, and possible pericarditis. There was bloody fluid present in the abdominal cavity. He suspected a bacterial infection, and provided the owner with antibiotics.
On December 1st, due to the dramatic increase in mortalities, the veterinarian came back to the farm and took samples; six carcasses and three sets of swabs were submitted to BCMAGRI-AHC. The presumptive positive results NAI subtype H5 were obtained and the farm was placed under official quarantine on the same day. On December 4th, birds in B2 began to demonstrate an increase in mortality.
Based on the detailed epidemiological investigation that followed, it was determined that this IP had no direct links to IP1 (different bird types, did not share personnel or equipment, used different hatcheries, feed companies and veterinarians).
Similar to IP1, exposure to the HPAI virus through indirect exposure to contaminated wild birds is likely how the virus was introduced into IP2. It was also determined that the virus was unlikely to have spread from this IP, as there was limited traffic onto and off the farm.
3.4. Laboratory Findings
Sequencing of the H5N2 virus obtained from samples of poultry on infected farms and analysis of the results indicated that it was a reassortant virus. The genome of all Influenza A viruses contains eight RNA gene segments, including hemaglutinin (H) and neuraminidase (N) genes, of which the H is the main gene segment involved in determining the pathogenicity. Based on sequence analysis, avian influenza viruses can be broadly categorized into Eurasian (Europe and Asia) and North American lineages. The new H5N2 virus detected in BC contains five of eight gene segments from highly pathogenic Eurasian H5N8 virus, including the H5 gene, and three of eight segments from typical North American viruses, including the N2 gene (originating in wild birds). It was the first time a Eurasian HPAI H5 lineage virus had been a cause of outbreaks of avian influenza in domestic poultry in North America. In addition, it appears that this particular reassortant virus with Eurasian and North American avian influenza virus gene segments had not been observed anywhere before, although all eight gene segments have been identified in either Asia/Europe or North America.
3.5. Outbreak Progression and Spread
In total, 11 commercial operations (three commercial turkey, one table egg layer and seven broiler breeder) and one non-commercial mixed bird farms were infected with the H5N2 virus. These farms were located in three distinct geographical clusters.
The mode of introduction of the AI virus and the originating farm could be determined for three of these farms: IP3 and IP4 were deemed to have been infected by males from IP1 that were introduced at a time when IP1 was infectious. IP6 was contaminated by IP5 after sharing a catching crew and by being located nearby (the two IPs are separated by the private farm driveway). Links among infected farms suggesting a specific mode of transmission of the virus were not identified for any other IPs in the outbreak.
The incubation period following the movement of infected birds was reported to be 4-5 days. For all other investigations into the potential mode of introduction of the virus into an IP we used an estimate of seven days. This is based on the fact that the length of the incubation period is dependent on the dose and source of exposure. It is expected that direct contact with infected birds would lead to a higher infective dose than indirect contact, such as the presence of a contaminated service provider (NAI-HSP).
The main clinical sign observed in all infected flocks was increased mortality. Other signs included a drop in egg production and reduced water consumption. The mean time period between the appearance of clinical signs and detection was 1.4 days with a range of zero to four days. This time period decreased as the outbreak progressed, indicating the success of surveillance and tracing activities.
The following table provides a description of events associated with each IP identified during the outbreak.
Table 1: Description of events associated with each IP in the HPAI outbreak in British Columbia in 2014-2015.
|IP#||Location||Type||# Birds in affected barn||Detection (H5) Table Note 1||Destruction Completed||Disposal (BHT Completed)||C&D Completed||Quarantine released|
|1||Chilliwack||Broiler breeder||13,000||Dec. 1||Dec. 5||Jan. 8||Feb. 13||Mar. 7|
|2||Abbotsford||Turkey||28,000||Dec. 1||Dec. 6||Jan. 3||Feb. 10||Mar. 5|
|3||Abbotsford||Broiler breeder||14,000||Dec. 3||Dec. 7||Dec. 28||Jan. 16||Feb. 7|
|4||Abbotsford||Broiler breeder||27,000||Dec. 2||Dec. 8||Jan. 6||Jan. 28||Feb. 19|
|5||Abbotsford||Turkey||30,000||Dec. 6||Dec. 10||Dec. 26||Jan. 13||Feb. 4|
|6||Abbotsford||Turkey||30,000||Dec. 9||Dec. 11||Dec. 27||Jan. 16||Feb. 7|
|7||Abbotsford||Broiler breeder||18,000||Dec. 10||Dec. 13||Jan. 15||Feb. 13||Mar. 7|
|8||Abbotsford||Broiler breeder||9,000||Dec. 10||Dec. 13||Jan. 3||Jan. 17||Feb. 9|
|9||Abbotsford||Broiler breeder||6,000||Dec. 10||Dec. 14||Jan. 6||Jan. 21||Feb. 12|
|10||Langley||Table Egg Layer||53,000||Dec. 13||Dec. 16||Jan. 24||Mar. 3||Mar. 25|
|11||Langley||Broiler breeder||12,000||Dec. 17||Dec. 19||Jan. 12||Feb. 3||Feb. 25|
|NC-01||Aldergrove||Non-commercial||85||Dec. 19||Dec. 20||Done at IP11||Feb. 21||Mar. 15|
|NC-02||Chilliwack||Non-commercial||95||Feb. 2||Feb. 3||Feb. 6||Feb. 19||Mar. 13|
- Table Note 1
Represents the day when non-negative H5 PCR test result were obtained.
3.6. Outbreak Conclusion
On January 9th, 2015, the NEOC was deactivated. The ICP and JEOC in Abbotsford remained functional in order to support the remaining field activities required for quarantine removal and deliver post-outbreak surveillance.
On February 2nd, 2015, a second non-commercial farm of approximately 100 birds (laying hens) with HPAI was detected. Sequencing results obtained on February 7th determined that the virus involved was an H5N1. Investigation determined that this was an incidental incursion most likely from wild birds. This premises was placed under quarantine on February 2nd, 2015 and the birds were destroyed the following day. Cleaning and disinfection was completed February 19th, 2015.
On June 3rd, 2015, in accordance with Article 10.4.3.1 of the OIE Terrestrial Animal Health Code, the province of British Columbia regained its disease-free status with regard to NAI. The OIE was notified on June 8th, 2015.
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