ARCHIVED - Report on the Outbreak of Notifiable Avian Influenza (H5N2) in Manitoba, Canada

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November 2010

Table of Contents

Synopsis

Low-pathogenicity notifiable avian influenza (NAI) was identified on a turkey breeder production farm north of Winnipeg, Manitoba, on November 23, 2010. All birds on this infected premises (IP) were humanely destroyed in the barns. The carcasses were subjected to in-barn biologic heat treament and subsequently disposed of in a landfill approved by the Manitoba government.

The virus was identified as an H5N2—the same virus subtype identified during the avian influenza outbreaks in the Fraser Valley of British Columbia in 2005 (H5 in turkey, California, 2002) and in 2009 (H5 in wild bird, California, 2007). The virus sequence identified during this outbreak was most closely related to wild birds (H5 in wild bird, Ontario, 2005; also N2 in wild bird, Minnesota, 2006).

A complete epidemiological investigation was undertaken into potential sources of avian influenza and opportunities for further spread of disease. There were no commercial poultry operations within a three-km radius of the IP; however, movement restrictions were placed on four commercial premises that raised or handled poultry that were epidemiologically linked to the IP. Epidemiologically and statistically valid active surveillance was completed for all premises under movement restrictions. NAI was not detected on any of these premises.

Movement restrictions on poultry and poultry products from the epidemiologically linked premises (ELP) were removed 21 days after the last possible date that a contact with the IP occurred. Negative test results for NAI from the final on-farm surveillance sampling were required prior to removing the restrictions. Restrictions on the IP were released 21 days following the completion of Canadian Food Inspection Agency (CFIA)-approved cleaning and disinfection.

Post-outbreak surveillance was conducted by using the existing Canadian Notifiable Avian Influenza Surveillance System (CanNAISS) structure, in accordance with the World Organisation for Animal Health (OIE) Terrestrial Animal Health Code (2010).

Introduction of the virus to the IP is believed to have resulted from contact with wild birds.

1. Manitoba Poultry Industry

Manitoba's poultry industry has over 350 producers and farms. Most farms are family run operations with 10 000 to 30 000 birds per flock. The commercial industry is confined to the southern half of the province's 647 797 square kms (250 116 square miles), with a high concentration in the Steinbach area (Figure 1).

Several avian influenza surveillance activities were active in Manitoba in 2010. The CanNAISS—conducted by the CFIA—targeted NAI in commercial poultry, and the national wild bird influenza survey—coordinated by the Canadian Co-operative Wildlife Health Centre (CCWHC)—included wild birds from Manitoba. The Manitoba government has an inventory of poultry operations and also conducts its own surveillance of wild birds and poultry flocks in co-operation with producers, veterinarians and wildlife officials.

Broiler Chicken and Turkey Sector

A total of 4 CFIA-registered hatcheries support the broiler chicken sector, which is composed of 119 registered broiler farms and 24 registered broiler hatching egg farms. Approximately 30 million broiler chickens are raised in Manitoba each year, which represents 4.6% of Canadian production.

There are 51 registered turkey farms and 8 turkey breeder farms in Manitoba, representing 7.2% of Canadian production. One registered hatchery supplies day-old poults to the grower farms in the province. The hatchery sets approximately 6.3 million eggs each year. Approximately 40 to 50% of this hatchery's production is exported to the U.S. The hatchery also obtains genetic stock for replacement breeders from a primary breeder in Canada and occasionally from the U.S.

Table Egg Sector

There are 158 registered table egg producers and 10 table egg breeder flocks in Manitoba. A total of 12 stand-alone pullet growing operations supply replacement laying hens to industry. A total of 2 registered hatcheries support the table egg industry in Manitoba.

Figure 1:Location of Poultry Production Types in Manitoba

Figure 1: Location of Poultry Production Types in Manitoba. Description follows.
Description for Figure 1 - Location of Poultry Production Types in Manitoba

This map shows the concentration of poultry farms in Southern Manitoba, based on information from the 2006 Census of Agriculture.

The highest concentration of farms, with over 40 poultry farms per municipality, is near Winnipeg, Portage La Prairie, and Duck Mountain Provincial Park.

Areas moving further away from these points have 0 - 39 farms.

2. Summary of the Findings on the Infected Premises

On November 19, 2010, a private veterinarian visited the IP to examine a turkey breeder flock that was reported by the owner to be depressed, to have decreased egg production and to have decreased feed consumption of two days' duration. Pharyngeal swabs and fresh tissues were submitted to Manitoba's Veterinary Diagnostic Services Laboratory (VDSL). Similar clinical signs were observed by the owner in a second barn on the IP on November 20, 2010.

On November 23, Manitoba's VDSL notified the CFIA that the samples had tested positive for the presence of influenza A virus on matrix PCR and positive for the H5 subtype on the real time RT-PCR assay. A CFIA investigation team was deployed to the IP that same day to conduct an epidemiologic investigation and collect samples for submission to the national reference laboratory—the National Centre for Foreign Animal Diseases (NCFAD) in Winnipeg, Manitoba. The protocols and procedures in the Notifiable Avian Influenza (NAI) Hazard Specific Plan and the Procedures for Investigation of Suspected Notifiable Avian Influenza were followed.

The samples from the provincial laboratory were also submitted to the NCFAD for confirmatory testing. Ancillary genetic testing subsequently demonstrated that the virus was an H5N2 sub type of low pathogenicity.

Virus Description

Complete gene sequences for 2 virus isolates were sequenced in their entirety. The sequences of both isolates were essentially identical. All 8 gene segments show 99% identity with avian influenza viruses that have been isolated from free-living aquatic birds in Canada and in the U.S. during the past 10 years. The closest match for the H5 segment was A/mallard/Ontario/499/2005 (H5N1), which is a low-pathogenic avian influenza virus of North American lineage that was isolated during the 2005 influenza virus survey in wild birds. The closest match for the N2 segment was A/mallard/Minnesota/464334/2006 (H5N2). These results support the hypothesis that the virus responsible for this outbreak is of wild bird origin.

The IP 1 was one of eight turkey breeder operations that supplied turkey hatching eggs to a single turkey hatchery in the province. The hatchery is located approximately 26 km north of the infected premises. Both premises were placed under quarantine to control movement of poultry and poultry-related products on or off the premises.

2.1. Management of the Infected Premises

The IP 1 was a turkey breeder farm that supplied 30 000 eggs per week to the hatchery (part of a turkey multiplier system). The premises consisted of one replacement rearing barn (Barn 1), which was empty at the time of the outbreak; one tom barn (Barn 2), with approximately 600 toms; and two turkey hen barns (Barn 3 and Barn 4), each containing approximately 3800 birds at the time of the investigation. On November 23, 2010, all of the birds on-farm were 44 weeks of age. See Figure 2 for a site map of the premises.

The farm operated as a closed production system; however, cull birds from the production barns were periodically sent to slaughter. The last shipment of cull birds was made to a federally registered slaughter establishment on October 19, 2010.

Eggs were disinfected on-site and transported to the hatchery.

The water source for the farm was a municipal potable water line that was subjected to treatment regimes and routine testing protocols set by the Manitoba government.

Disposal of dead birds was by incineration and on-site burial.

Figure 2. NAI-2010-MB-01 Infected Premises Site Map

Figure 2. NAI-2010-MB-01 Infected Premises Site Map. Description follows.
Description for Figure 2 - Infected Premises Site Map

This site map shows the infected premises, which includes:

  • An empty barn previously used as a replacement barn
  • A tom barn, which housed 600 birds
  • Two hen barns, which housed 3800 birds each
  • Five feed bins
  • A machine shed
  • Hay shed
  • A power house
  • A house
  • A water pipeline entry and three water lines
  • A well, which was out of use for the last 18 months
  • A driveway

Biosecurity:

Site entry included a shower in / shower out protocol with dedicated barn clothes and footwear for all staff, including the insemination crew. Footwear was dedicated to each barn.

Hatchery Truck:

The scheduled pick-up of eggs took place Mondays, Wednesdays and Fridays. A dedicated egg truck from the hatchery was used for this purpose. The driver followed biosecurity procedures that were developed by the hatchery. The truck was washed after each delivery of eggs to the hatchery. Racks used for transporting the eggs to the hatchery were dedicated to the farm and were washed and disinfected at the hatchery in a designated area prior to being returned to the farm.

Artificial Insemination Crew:

The artificial insemination (AI) crew attended the premises on two consecutive days once per week. There is a written biosecurity protocol that was followed by the members of the AI crew. Insemination and semen collection equipment was dedicated to the farm.

2.2. Premises Location

IP 1 is located approximately 10 km north of Winnipeg. With the exception of the turkey flock, there were no other commercial livestock on the premises. The nearest commercial poultry operation, ELPI-2, was approximately 3.4 kms from the premises. There were no other commercial operations with susceptible species within a 10 km radius of IP 1.

2.3. Geographic Location and Wild Birds

The IP was located on the Mississippi flyway (Figure 3) and was close to a marsh that is one of the major migratory stops for many ducks, geese and shorebirds on the flyway. The owner reported that there were Canada Geese around the IP feeding on grain up until the arrival of snow on November 10, 2010.

Figure 3. The Mississippi Flyway (Texas Parks and Wildlife Department. Available at: http://www.tpwd.state.tx.us/huntwild/wild/birding/
migration/flyways/mississippi/).
The red marker represents the location of Winnipeg, MB.

Figure 3. The Mississippi Flyway (Texas Parks and Wildlife Department). Description follows.
Description for Figure 3 - The Mississippi Flyway (Texas Parks and Wildlife Department)

This map shows the south to north path of the Mississippi Flyway through North America. Winnipeg is on the flyway.

The bird migration route generally follows the Mississippi River in the United States and the Mackenzie River in Canada. The main end points are North-Central Canada and the region surrounding the Gulf of Mexico.

3. Epidemiological Investigation

In accordance with the CIA's NAI Hazard Specific Plan and the OIE Terrestrial Animal Health Code (2010), all poultry, poultry products and things exposed to poultry or poultry products associated with the IP were subject to movement tracing for a 21-day period prior to the onset of clinical signs of avian influenza.

3.1 Tracing

Premises with epidemiological linkages via direct or indirect contacts to the IP were named ELPs. ELPs were numbered according to the IP to which they were linked and the order in which the linkage was determined chronologically. Thus, ELP1-1 refers to the first premises epidemiologically linked to the first infected premises (in this outbreak, the hatchery). In this outbreak, there was only one IP, and all ELPs are designated ELP1-#.

3.1.1. Critical Period

The critical period is the period from the estimated date of introduction or the maximum incubation period (as cited by the OIE) prior to the onset of clinical signs. Field determination of the critical period is typically done by establishing when the earliest clinical signs were detected in the flock and counting back the period of time considered to be the maximum incubation period. For low pathogenicity strains of avian influenza, especially where the virus is not well adapted to poultry, determining when clinical signs started can be challenging because respiratory signs may be absent. The egg production records were analyzed to determine when a statistically significant drop in egg production occurred. This date was determined to be November 7, 2010, which in turn means that October 17, 2010, was the earliest possible date of introduction.

3.1.2. Direct Contacts

Direct contacts were defined as movements of poultry, either onto (trace-in) or off (trace-out) the IP.

Within the identified critical period, there was one movement of poultry off the IP. This was a movement of cull birds to slaughter on October 19, 2010. This movement was investigated, and it was determined that there was no risk of spreading the infectious agent to other poultry operations. There were no movements of poultry onto the premises within the identified critical period.

3.1.3 Indirect Contacts

Indirect contacts were defined as contact with vectors or fomites capable of carrying an infectious organism, so that transmission to susceptible animals could take place.

A qualitative risk assessment was undertaken as to the potential for transmission by indirect contact. All premises deemed to represent potential risk were subjected to quarantine and surveillance testing.

Hatchery

Hatching eggs were removed from the farm and delivered to the hatchery three times per week. The eggs were disinfected prior to leaving the farm, and the truck followed biosecurity procedures as outlined by the hatchery. Contact with the IP was considered significant. The hatchery was placed under quarantine on November 24, 2010, to control movement of poults until a more detailed evaluation of the risk level could be completed. No poults left the hatchery after the infected farm was identified, and all poults en route were recalled. The hatchery was identified as ELP1-1.

The hatchery was registered by the CFIA as a Hazard Analysis Critical Control Point (HACCP) hatchery and was last audited by an Agency veterinary inspector on November 20, 2010. All airflow moves in one direction—from incubators to hatchers to the rest of the facility. Water treatments include ultraviolet treatment, chlorination and reverse osmosis. All equipment was maintained in excellent condition and kept clean.

A sign-in log was maintained at the hatchery for all visitors who must declare that they have not had contact with domestic or wild birds, swine or processors for 72 hours prior to entry. Entry into the hatchery was via showers, and hatchery-supplied clothing and footwear must be worn.

Eggs were picked up from breeder flocks using dedicated vehicles. Vehicles were washed and disinfected at the end of each day of use and stored on-site at the hatchery. The driver did not enter the source flock barns.

All eggs were washed and sanitized at the breeding farm. No floor eggs or dirty eggs were accepted at the hatchery. The eggs were placed on clean trays that sat on racks that were loaded onto the hatchery egg trucks. Farm racks were taken off the truck at the hatchery in the egg receiving room, and racks were labelled with a sticker to mark them as farm racks. Trays were transferred from farm racks to incubator racks prior to progressing through the hatchery. The farm racks were pressure washed and disinfected before being returned to farms. Farm racks never crossed over to the “clean” side of the hatchery.

Eggs could be tracked throughout the whole hatchery system using a unique identifier that indicates source flock and date of lay.

Eggs from the IP and from premises that were under restrictions as a result of an epidemiological link to the IP were present in the hatchery. A decision was made to destroy all eggs in the hatchery, complete a cleaning and disinfection of the hatchery, and start the hatching process with eggs sourced only from breeding farms that were not implicated in the outbreak response. The eggs and hatchlings were destroyed under CFIA supervision using an on-site macerator and disposed of in a provincially approved landfill on December 4, 2010. The cleaning and disinfection of the hatchery was approved by the CFIA, and the quarantine removed on December 23, 2010.

Private Veterinarian

On November 18, 2010, a private veterinarian was called to the IP because the owner noticed a drop in egg production. At that time, the veterinarian examined some dead birds. He returned on November 19 to perform necropsies and obtain samples.

After visiting the IP, the veterinarian visited a turkey grower operation. He used standard biosecurity procedures before entering the barn and did not visit another poultry farm for three days following this visit.

The contact with the turkey grower operation was considered significant. The premises were placed under quarantine on November 24, 2010, and surveillance testing was carried out. The premises were identified as ELP1-2.

Artificial Insemination Crew

An artificial insemination crew had contact with the IP several times within the critical period, including on November 23, 2010. The crew serviced a total of three breeder operations and two brooder operations. Each production system was closed with each breeder flock using a dedicated brooder facility. There was no outside or shared use of the brooder barns, and no other brooder premises were used. The three breeder flocks all supplied hatching eggs to the same hatchery (ELP1-1).

The hatchery set the schedule for insemination and vaccination visits. Each breeder flock was visited twice per week on consecutive days. All premises had shower in / shower out procedures with controlled access. All equipment used for semen collection and insemination was dedicated to each facility. The transport vehicle for the crew was supplied by the hatchery and was washed prior to each farm visit.

The contact the insemination crew had with the IP and the other breeder operations was considered to be significant. These premises were identified as ELP1-3 and ELP1-4. These premises were placed under quarantine on November 25 and November 29, respectively, and surveillance testing was carried out.

Summary

The investigation determined that there were eight separate premises that had indirect contact with the infected premises during the critical period. A total of four of these premises required follow-up testing based on assessment of risk associated with the contact involved.

Figure 4. Epidemiologically linked premises

Figure 4. Epidemiologically linked premises. Description follows.
Description for Figure 4 - Epidemiologically linked premises

This diagram shows how the epidemiologically linked premises (referred to as ELPs) were linked to the infected premises (a turkey breeder referred to as IP1).

IP1 and ELP1-1, ELP1-2, ELP1-3, and ELP1-4 were quarantined.

ELP1-1 is a hatchery that was epidemiologically linked to IP1 via eggs.

ELP1-2 is a turkey grower that was epidemiologically linked to IP1 via a private veterinarian.

ELP1-3 is a turkey breeder that was epidemiologically linked to IP1 via the insemination crew.

ELP1-4 is a turkey breeder that was epidemiologically linked to IP1 via the insemination crew.

ELP1-5 is a turkey brooder that was epidemiologically linked to IP1 via the insemination crew and to ELP 1-4 via birds.

ELP1-6, ELP1-7 and ELP1-8 are turkey breeders that were not quarantined but were epidemiologically linked to IP1 via an industry rep.

Figure 5. Location of epidemiologically linked premises relative to the infected premises

Figure 5. Location of epidemiologically linked premises relative to the infected premises. Description follows.
Description for Figure 5 - Location of epidemiologically linked premises relative to the infected premises

This diagram shows the location of epidemiologically linked premises (referred to as ELPs) in relation to the infected premises (referred to as IP1).

ELPs1-2a, a turkey grower linked to IP1 via a vet visit, and ELPs1-2b, a layer identified in the trace-out, are shown within a 10-kilometre radius of IP1.

The following are shown outside of a 25-kilometre radius of IP1:

  • ELPs1-1, a hatchery linked to IP1 via eggs
  • ELPs1-3, a turkey breeder linked to IP1 via insemination
  • ELPs1-4, a turkey breeder linked to IP1 via insemination

3.2. Surveillance

There were no commercial poultry operations located within three kms of the IP. There were three ELPs identified that were subjected to surveillance testing. The fourth epidemiologically linked operation, the hatchery, was not included in surveillance testing.

An end date for surveillance testing on an ELP was determined by adding 21 days to the last date that a contact could have resulted in the movement of virus between the infected premises and the ELP in question. The period of 21 days is the maximum incubation period for NAI as determined by the OIE Terrestrial Animal Health Code (2010).

Base-line Surveillance

All premises linked to the IP were subjected to statistically valid sampling for the detection of antibody and virus at the time that they were identified. The sample collection occurred at the time the premises were issued movement control documents. The sample set included the following:

  1. Oropharyngeal and cloacal swabs from 60 birds from each barn. These samples were tested using a RT-PCR assay.
  2. Serum samples from 20 birds in each barn. These samples were tested using c-ELISA.

Summary of Results:

Baseline surveillance was conducted on ELP1-2, ELP1-3 and ELP1-4. Negative results for the presence of NAI were received for all premises.

3.2.1 Pre-Movement testing

Pre-movement surveillance was conducted to ensure that all poultry and poultry products licensed for movement from a quarantined operation (e.g. to slaughter) were negative for NAI. The sample set included oropharyngeal and cloacal swabs from 60 birds in each barn that was shipping poultry or poultry products and 20 birds from each other barn on the premises; this was collected within 72 hours of the movement occurring. Samples were tested using a RT-PCR assay.

Summary of Results:
Pre-movement testing was performed on ELP1-2 (sampled December 5, 2010) and on ELP1-3 (sampled November 29, December 2 and 6). All tests on all samples were negative for NAI. There was no pre-movement testing for ELP1-4 because there were no movements of poultry or poultry products during the time that the premises were under quarantine.

3.2.2. Quarantine Release testing

Surveillance testing was also conducted to ensure the NAI-free status of the premises prior to release of quarantine. The sample set included oropharyngeal and cloacal swabs from 60 different birds from each barn. Samples were tested using a RT-PCR assay.

Summary of Results:

Quarantine release testing was performed on ELP1-2 (sampled December 7), ELP1-3 (sampled December 9) and ELP1-4 (sampled December 7). All tests on all samples were negative for NAI.

Table 1. Summary of Testing performed on ELPs
Premises Testing Type Sampling Date Results
ELP1-2 BaselineNovember 24, 2010Negative
ELP1-2 Pre-movementDecember 5, 2010Negative
ELP1-2 Quarantine ReleaseDecember 7, 2010Negative
ELP1-3 BaselineNovember 25, 2010Negative
ELP1-3 Pre-movementNovember 29, 2010Negative
ELP1-3 Pre-movementDecember 2, 2010Negative
ELP1-3 Pre-movementDecember 6, 2010Negative
ELP1-3 Quarantine ReleaseDecember 9, 2010Negative
ELP1-4 BaselineNovember 29, 2010Negative
ELP1-4 Quarantine ReleaseDecember 7, 2010Negative

4. Disease Control Actions

4.1. Movement Restrictions

Movement restrictions were placed on the IP and on all ELPs deemed at risk of spreading disease.

A licence issued by the CFIA was required to permit movement of poultry, poultry product and by-products, or anything used in respect to poultry (farm equipment, transport vehicles, feed, sawdust, etc.). In accordance with the NAI Hazard Specific Plan, a pre-movement testing and licence issuance system was implemented for birds moving to slaughter and hatching eggs moving to hatcheries. Licences were only issued after receiving official negative surveillance results. Restrictions remained in place on all ELPs until it was demonstrated that poultry on the premises were free from NAI infection.

Table 2: Summary of Quarantines
Premises Quarantine Date Quarantine Release Date Control Reason Production Type
IP 1 November 23, 2010February 22, 2011Infected PremisesTurkey Breeder
ELP1-1 November 24, 2010December 23, 2010Indirect ContactTurkey Hatchery
ELP1-2 November 24, 2010December 12, 2010Indirect ContactTurkey Grower/Table Egg
ELP1-3 November 25, 2010December 12, 2010Indirect ContactTurkey Breeder
ELP1-4 November 29, 2010December 08, 2010Indirect ContactTurkey Breeder

4.2. Destruction

An order for the destruction of all turkeys on the IP was issued on November 24, 2010. The turkeys on the IP were humanely destroyed on November 28 using whole barn gas flooding with carbon dioxide (CO2). Representatives from organizations responsible for animal welfare in the province of Manitoba reviewed and approved the protocols used.

4.3. Disposal

Composting of poultry carcasses on site was used by the CFIA. The first stage of composting was equivalent to an in-barn Biologic Heat Treatment (BHT) process. The CFIA protocol for this process requires the temperatures to be greater than or equal to 37°C and be sustained for six consecutive days. CFIA disposal specialists recorded temperatures throughout the compost pile on a daily basis. On December 14, 2010, the BHT was completed and the compost pile was moved outside the barn. The material was then transferred to a provincially approved landfill, and this process was completed on December 16, 2010.

4.4. Cleaning and disinfection of facilities and equipment

Cleaning and disinfection activities must meet the standards set out by, and be approved by, the CFIA. Adherence to the procedures is enforced and documented through a series of inspections by CFIA personnel. All areas and equipment potentially contaminated with NAI virus were included in the Cleaning and Disinfection Protocol.

Cleaning and disinfection of the physical structures on the IP was initiated after the compost piles were moved out of the barn on December 14, 2010. Cleaning and disinfection was completed February 1, 2011. In accordance with the current guidelines of the OIE Terrestrial Animal Health Code (2010), declaration of freedom from NAI following an outbreak was made three months following the approval of the cleaning and disinfection of the IP.

5.0. Post-Outbreak Surveillance

Following the cleaning and disinfection of the IP, surveillance in the CanNAISS (see section 7) was enhanced in Manitoba (post-outbreak surveillance). The CanNAISS sampling plan in Manitoba was adjusted and included surveillance of NAI in commercial chickens and turkeys, hatchery supply flocks, and table egg layer flocks (prior to cull). This adjusted sampling was in effect during the three months following the date on which the cleaning and disinfection of the IP was approved by the CFIA (February 1, 2011). The design of this surveillance was science based and driven by amendments to the OIE guidelines (Article 10.4.3), with consideration for the re-establishment of trade. A combination of random and targeted sampling were applied, and CanNAISS was applied as well. Both private veterinarians and CFIA staff were involved with blood sample collection, and all diagnostic testing was performed at the NCFAD. As per the CanNAISS protocol, all samples were tested by c-ELISA with a full HI panel used for confirmatory testing. A total of 87 commercial poultry farms were tested for NAI during that period in the province of Manitoba, and all samples were negative.

6. Hypothesis on the source and transmission of the disease

The influenza virus can be transmitted directly from bird to bird through secretions and feces and indirectly through human movement, contaminated feed, fomites, water or equipment. The virus could have been introduced into the IP in one of the following two ways:

  1. The direct or indirect movement of virus from a source poultry premises; or
  2. Exposure to virus in the natural environment through direct or indirect contact with wild birds.

In this outbreak, no trace-in premises were found to be the source of NAI virus to the IP. All premises identified during the trace-in investigations were subjected to epidemiologically valid surveillance for NAI, with negative results reported for each.

Feed and water contamination as potential sources of NAI virus were investigated. The feed mill was inspected, and their processes and written procedures were reviewed. No opportunities for contamination during ingredient mixing were observed. The infected farm used municipal water that is subject to chlorination and routine monitoring overseen by the Manitoba government. Any potential for water contamination that could occur would be addressed by the chlorine treatment. Feed and water contamination did not appear to be a source of NAI virus for the IP.

Although appropriate biosecurity practices were in place for the entry of personnel working within the barns, the practice of opening large doors for varying periods of time to bring straw bedding material into the hen barns could have provided a portal for the entry of wild birds into the barns. It was also noted that the tops of the straw bales were covered with fecal material from wild birds. Both of these situations could have resulted in contact with NAI virus from the wild bird population.

It has been well established that wild birds act as reservoirs of the avian influenza virus and may be the initial source of infection to domestic birds through direct contact or indirectly via the contamination of feed and/or water. The proximity of the Oak Hammock Marsh, a migratory stop and breeding ground for waterfowl and shorebirds, could potentially increase the risk of exposure to wild type influenza A viruses from this transient wild bird population.

Since 2005, The Canadian Cooperative Wildlife Health Centre has coordinated national inter-agency surveillance for the avian influenza virus in wild birds across Canada. The preliminary results for the 2010 study indicate that a number of samples collected in Manitoba were positive for influenza A viruses using the matrix PCR. Some of these samples have tested positive on either the H5 or the H7 RT-PCR.

The sequence data suggests a recent introduction from the wild bird reservoir. In terms of adaptation to poultry, previously documented adaptations—such as deletions in the stalk of the neuraminidase—were not identified. However, a number of studies have shown turkeys to be more susceptible to avian influenza viruses from the wild bird reservoir.

The serum samples taken from Barn 3 (hen barn) on November 23 were all positive for H3, and all the samples were negative for H5 and H7. Serum samples taken from Barn 4 (hen barn) on November 23 were all positive for H3, and 13 of 30 samples tested positive for H5. All of the samples from Barn 4 were H7 negative. Representative samples taken on November 28 (pre-depopulation) from both hen barns were positive for antibodies to H5, while 2/5 of the samples from the toms' barn were positive. This would suggest that there was a rapid spread of virus from Barn 4 to Barn 3 and Barn 2, with sero-conversion occurring during the five days between initial CFIA sampling on November 23 and the pre-depopulation sampling on November 28.

7. Response Structure

7.1. Role of the CFIA

The CFIA is the lead agency for responding to incursions of reportable animal disease such as NAI. Other federal government agencies provide support as required.

7.1.1 Hazard-Specific Plans

The CFIA has developed strategies to deal with potential foreign and reportable disease occurrences. The NAI Hazard Specific Plan forms part of the overall plan to deal specifically with an incursion of NAI. It supplies background information on the disease itself, as well as outlining the principles of control and eradication, disinfection of IP and surveillance.

7.1.2. Animal Health Functional Plan

The emergency response organization and the detailed procedures to implement these contingency plans are set out in the CFIA Emergency Book and the CFIA Animal Health Functional Plan. The CFIA uses the Incident Command System (ICS) to manage the response to the outbreak. For this response, an Emergency Operations Centre was activated in Winnipeg, with logistical and policy support provided by the Western Area Office in Calgary and at National Headquarters in Ottawa.

7.1.3. Canadian Notifiable Avian Influenza Surveillance System

CanNAISS is a joint initiative of government, industry and Canadian farmers to prevent, detect and/or demonstrate the freedom of highly-pathogenic avian influenza and low pathogenic H5 and H7 subtypes of NAI in Canada's domestic poultry flocks. CanNAISS is designed to meet NAI guidelines from the OIE.

CanNAISS provides ongoing surveillance for NAI in the commercial poultry population in Canada. During an outbreak of NAI, CanNAISS provides surveillance on premises and areas not part of the outbreak. CanNAISS continued without interruption in Manitoba and the rest of Canada during the outbreak without detection of NAI.

7.2. Role of Provincial and Municipal Governments

Each provincial government in Canada has entered into an agreement with the CFIA to support activities undertaken in responding to the incursion of a foreign animal disease. The specifics of these agreements are contained in each government's Foreign Animal Disease Emergency Support Plan. The provinces play a key role in establishing and maintaining good working relationships with municipal governments and industry organizations.

During this outbreak, in addition to physical infrastructure, employees from Manitoba Agriculture, Food and Rural Initiatives (MAFRI) were embedded in the emergency operations center. This group provided GIS mapping and veterinary epidemiology support to the CFIA response. MAFRI's support and co-operation during this emergency response is gratefully acknowledged.

Appendix 1: List of Acronyms

AI
Artificial Insemination
AIV
Avian Influenza Virus
BHT
Biologic Heat Treatment
C&D
Cleaning and Disinfection
CanNAISS
Canadian Notifiable Avian Influenza Surveillance System
CCWHC
Canadian Cooperative Wildlife Health Centre
c-ELISA
Competitive Enzyme Linked Immuno Sorbant Assay
CFIA
Canadian Food Inspection Agency
CO2
Carbon Dioxide
ELP
Epidemiologically Linked Premises
FADES
Foreign Animal Disease Emergency Support (Plan)
H
Hemagglutinin
HI
Hemagglutinin Inhibition
HACCP
Hazard Analysis Critical Control Point
ICS
Incident Command System
IP
Infected Premises
LPAI
Low Pathogenic Avian Influenza
MAFRI
Manitoba Agriculture, Food and Rural Initiatives
MB
Manitoba
N
Neuraminidase
NAI
Notifiable Avian Influenza
NCFAD
National Centre for Foreign Animal Diseases
OIE
World Organisation for Animal Health
PCR
Polymerase Chain Reaction
RT
Reverse Transcriptase
USA
United States of America
UV
Ultraviolet
VDSL
Manitoba Veterinary Diagnostic Services Laboratory
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