Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

[AlaskaDenise]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

This underscores the problems with the lack of scale in wild bird testing, making it a less useful resource

Are there other effective ways to test large bird populations?

Could the water from lakes be tested, i.e., if lakes known to accomodate large migratory populations were tested every ?2? weeks, could they expect to find sufficient evidence of AI?

.

[canagica]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Could the water from lakes be tested, i.e., if lakes known to accomodate large migratory populations were tested every ?2? weeks, could they expect to find sufficient evidence of AI?
.

It's a great question, and AFAIK, still in the process of being figured out. There was a recent paper published in the Journal of General Virology 89:509-519 that looked at finding AI in pond sediments

Prevalence and diversity of avian influenza viruses in environmental reservoirs

Andrew S. Lang, Anke Kelly and Jonathan A. Runstadler2

Little is known about the ecology and evolution of avian influenza in the natural environment, despite how these affect the potential for transmission. Most work has focused on characterizing viruses isolated from hosts such as waterfowl, and there have also been several instances of isolation and detection from abiotic sources such as water and ice. We used RT-PCR to amplify and characterize the influenza virus sequences present in sediments of ponds that are used heavily by waterfowl. The detection rate of influenza virus was high (>50 %). Characterization of the viruses present by sequencing part of the haemagglutinin (HA) gene showed that there is a diverse collection of viruses in these sediments. We sequenced 117 partial HA gene clones from 11 samples and detected four different HA subtypes (H3, H8, H11 and H12), with approximately 65 % of clone sequences being unique. This culture-independent approach was also able to detect a virus subtype that was not found by sampling of birds in the same geographical region in the same year. Viruses were detected readily in the winter when the ponds were frozen, indicating that these sediments could be a year-to-year reservoir of viruses to infect birds using the ponds, although we have not shown that these viruses are viable. We demonstrate that this approach is a feasible and valuable way to assess the prevalence and diversity of viruses present in the environment, and can be a valuable complement to more difficult viral culturing in attempting to understand the ecology of influenza viruses.

And while AIs can be found in water and ice, it's still not clear how effective our testing is, but again, it could potentially be very useful and was incorporated in the US testing scheme. (From the 2006 USDA press release outlining the U.S. testing efforts):

5. Environmental sampling of water and bird feces: Waterfowl infected with or carrying avian influenza viruses release these viruses through the intestinal tract and the virus can be detected in both feces and water in which the birds swim. This provides a means of virus spread to new avian hosts and potentially to poultry or other livestock. Analysis of both water and fecal material from waterfowl habitat can provide evidence of avian influenza viruses circulating in wild bird populations. In 2006, USDA and others plan to collect 50,000 environmental samples from high-risk waterfowl habitats throughout the lower 48 states, Hawaii, as well as from other areas such as Guam and the U.S. Territories and Freely Associated States of the Pacific.

Certainly it's more efficient to test an area than to catch all of the birds in an area, but no one knows how many shedding individuals it would take in order for our testing to detect the virus...Sort of a similar problem to figuring out how many birds we need to test. There are statistical ways to do it, but they're based on some big assumptions (truly random sampling, a pre-determined level of infection, etc.) that are hard to carry out in real life.

That's one reason why it seems like these areas where a poultry outbreak occurs should seem like great targets to test a comprehensive wild bird/environmental testing regime. We already know that the poultry got sick from some vector, so AI had to be in the area. Whether it came from anthropogenic contamination (which we currently test for) or wild birds we can't usually say without a shadow of a doubt...so why not make an earnest effort to find it anywhere it might occur? Saturate the surroundings with environmental testing, quickly estimate the bird population and come up with a number of birds to sample (even if the sampling has to be done via shotgun), and see what might be out there? Use a series of testing methods to see if one works better than another.

There's a set of studies I'd be very interested in...

[mixin]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Here's a little info on water testing from the link I posted:

The concern was that run-off from infected premises may have entered either surface water or ground water. Since no manure was spread onto the fields after the discovery of HPAI, contaminated run-off would have to have occurred during times of depopulation, removal or composting of birds. Rainfall records from the periods of depopulation of the first two infected premises were analysed in the light of infections on three subsequent premises. The rationale was that contaminated surface water would have to travel in ditches downstream from one premises to another and then be introduced mechanically into the susceptible barn by a producer?s dirty boots or a wet farm dog fresh from taking a dip in a ditch. Using surface water drainage maps produced by Resource Management Branch showing the creeks and ditches and the direction of water flow along with farm activity information provided by the producers, it was concluded that transmission by surface water from one farm to another was possible but the risk was likely to be low. As well, several dozen water samples taken from ditches and sloughs scattered across the Matsqui Prairie in early April failed to demonstrate avian influenza virus through laboratory testing.

The concern that ground water could be a source of viral transmission was discussed with authorities from BC Water Land and Air Protection and the Drinking Water Program of the Fraser Health Authority. Both reported that while no measurements of ground water flow were being done in the area, given the flat topography and sand and fine gravel sediments in the area, expected groundwater flow would be less than one metre per day. Questionnaires administered to the owner/manager of each infected premises indicate that only Premises 1 and 2 used wells (sand point), while Premises 3-5 obtained their water from a municipal water system. Research on another type of virus (enteroviruses) indicate that they may traverse 60-70 meters in a vertical direction and 500 meters horizontally. Given the distances between the farms, slow ground water flows and only two premises using well systems, it was considered highly unlikely that contaminated ground water had spread the HPAI virus from one commercial operation to another.

However, it is not inconceivable that contaminated surface water from a field near the index premises drained downward into the farm well bed some 18 feet below the ground surface and through this means found its way into the water supply to the barn. In this way, the LPAI strain may have entered the index flock as an original point of entry in February.

[Oracle]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

If you want a lesson in how to spread H7N3, read the Fraser Valley outbreak synopsis (link above).

What they didn't know: HPAI is transmissible in feathers/dust (report date is 2005).

At location 1, workers dumped culled birds on conveyors belts, which then dumped them at height into dumpsters, where the dead birds were collected and ground-up for composting. They composted the carcasses - and just where did they bury the carcass compost material, hmmm?

Harsh lesson number one: practice good biosecurity, even if you think it's a low pathogenic strain (although the virus was typed as H7, it was initially deemed as a low pathogenic strain, due to the slow onset and relatively mild symptoms at the index case site).

At location 2, a previously approved euthanasia method employed also caused substantial feather and dust dispersal, because the equipment used required placement outdoors.

Harsh lesson number two: if you fail at first, you may still not get it right the second time.

"An adjacent barn on the index premises containing a younger flock of 9030 birds (24 weeks of age) began to show an alarming rise in mortality on February 17, 2004 such that by the 19th, 1500 birds were found dead on that day alone. Infection of this second flock on the index premises with the mutated strain of the avian influenza virus constituted the beginning of the
HPAI outbreak event."

Harsh lesson number 3: old birds (54 weeks-old) may not die quickly of H7 strains, but young birds will. That is apparently what happened in the 8-day period between the initial vet report of infection in flock 1 and outbreak in younger birds (24 weeks-old). Second barn is downwind of first barn. These barns are equipped with large, powerful fans that exhaust ejecta dust, feathers and volatilized liquids. Very high titers of viral particles were isolated in high volume gas samplers placed within barns, and similar collectors placed outside of barns also detected virus, albeit at low numbers.

"Three weeks later a second premises 1.6 km away showed signs of
infection, then one week later three more premises (2-3 km) south and west became infected."

The first 2 barns were upwind of barns 3, 5 and 6, but sufficiently far from cluster point 2 that they were assumed to be a moderate wind-dispersal risk, given wind speed, rising Spring temperatures, distance and ultrafine particulate composition of barn litter and feather dust materials.

Harsh lesson number 4: crappy biosecurity by poultry farm service people, after the 'horse has left the barn' will probably spread the infection to adjacent facilities, as it most likely did in this case.

If you are taking notes, you may want to jot down this point: in many of the photos that accompanied reports of culling of infected flocks in India, Bangladesh, Thailand, China and Vietnam, Egypt - it is highly likely that the disposal methods released feather dust, aerosol fluids, ground, fine feathers and fecal matter contaminated bedding dust. All contributed as transmission sources. Well-meaning, but not so well trained district 'inspectors' may have then transported dust-stabilized virus on clothing to nearby farms during surveillance visits afterwards.

"Two weeks later, 11 additional commercial premises were identified as infected and in this way the epidemic began slowly and picked up speed as more flocks became infected. By the time the outbreak was brought under control, infected farms appeared in three clusters, each of which had a diameter of 5-6 km (over the course of more than one month).

There is also mention of leaking carcass disposal trucks, but it's prudently dismissed as probably not a high risk factor. Unless the trucks are driving right by your facilities. A map would have been nice, as it would have shown the roughly rectangular prairie locale, bounded by river on two sides, with farm roads and one main highway between pickup and distant disposal (local landfill). No mention is made of leaking liquid sampling, but Provincial health officials were worried enough to call in decontamination services to treat the congealed muck that had drained off trucks at unloading points, into nearby ditches.

Surface and groundwater transport discussion are pointless; runoff and groundwater are hydraulically predisposed to move into the nearby Fraser River. And that brings us to the probable source: riverine wetlands immediately downriver of the index site. My bet is on passerine species that probably picked up the infection from local aquatic bird habitat, while scavenging for seed, berries, or insects.

Why this time of year? That wetlands habitat is thawing, and virus is moving into the water column, deposited via infected wild fowl droppings. Smaller birds are well known to be 'visitors' to large poultry barns - it's a free source of food in the leaner time of the year. Passerines have been identified as carriers of both H5 and H7, when exposed to a large viral load; you see them all the time, darting in and out of stores homegoods stores that peddle garden supplies. Some species, like starlings, are adept, urban-adapted scavengers. This may provide an alternative explanation to human-aided transport of virus to remote outbreak locations, and also provides a clue on outbreak timing.

Thanks for posting the link to this study; it provided substantially more material for constructive discussion than did the Saskatchewan outbreak case.

[AlaskaDenise]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Interesting input in the above posts.

Oracle makes a good point - to design an effective testing protocol, you need to factor in species-specific behaviors. Scavengers will transfer virus differently than lake dwellers. Lake dweller behaviors are very different - some live in higher densities (e.g., Snow Goose) while others (e.g., Loons) only have one breeding pair per lake.

While spring thaws transfer virus into water, test results will temporarily show higher levels. I tested local stream water for a couple of years & during spring thaws we showed higher levels of e-coli - and I would assume that had we tested for AI we might have found some.

Mixin's quote - "several dozen water samples taken from ditches and sloughs scattered across the Matsqui Prairie in early April failed to demonstrate avian influenza virus through laboratory testing" shows how difficult this approach can be.

Canagica's statement - "it's more efficient to test an area than to catch all of the birds in an area," is an approach well worth trying. It would need to include water, dust, soil, etc.

.

[mixin]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

http://pubs.rddc.gc.ca/BASIS/pcandid/www/engpub/SF If you search the words: aerosol sampling, it will bring up the report on the follow-up sawdust testing they did.

Just to add... I've found Canadian studies tend to be really thorough and easy to read & understand.

[Malcolm]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Aerosol sampling was negative in the Canada study referenced above----looks like they were very meticulous.

A key to influenza viral survival is MOISTURE.

[mixin]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Malcolm, I wonder if you and I read the same article: The study was designed well but poorly thought out, imo.

Actually, they did find viral doses but only with the XMX sampler.

What is evident from this study is the virus was circulating in the barn sampled and in the surrounding environment. The estimated viral load yielded a value of 292 viral doses/m3 of barn air. The quantitative, spatial and temporal nature of the dispersion however remains undefined. It would be speculative to say more about the possibility of airborne dispersion without conducting a better-designed study to define viral presence in and around contiguously infected barns. Geomorphic mapping detailing viral plumes and their dynamics based on a meteorological continuum would be especially useful.

Yes, the wind really does change directions; it's best to be prepared to move equipment and have equipment powerful enough to do the job.

At farms B and C there were dead infected animals. The slit samplers should have captured particles from the exhaust fans. However, the slit samplers were all placed approximately 75-100m on opposite sides of the barn along the line of the forecast winds for the area. As the winds were variable it was not practical to shift the sampling array once set up. Because of the shifting winds it is possible that viral aerosols might not have reached the sampling sites. In addition, the sampling rate of the slit samplers was 30 lpm (as compared to the high volume XMX sampler which collected 800 lpm) which may have been insufficient to capture adequate material above a detectable limit. This speculation was partially confirmed by tracer smoke (electric smoke generator and smoke grenades provided to CFIA by the RCMP) that was used to determine the volume and direction of airflow from the barn exhaust fans. (figure 3). In both locations the exhaust fans were directed into the wind, resulting in smoke being forced back towards the barns and up over the roof. This meant that the exhausted air particles were well above ground level and would not be low enough to be sampled by the slit samplers positioned nearby (figure 4).

The negative results from the slit samplers may have resulted from a number of factors. As shown in table 1, there were no live viruses sampled from farm A. At this farm, the animals were not yet dying from infection and CFIA swab samples from these birds were positive only for PCR tests. Thus it is conceivable that no viable airborne infectious particles were produced at the time the slit samples were taken.

Unfortunately, they didn't think the virus would survive the impact from this machine so they only took 16 samples. Seems like tests showing dead virus would be better than no virus at all.

This suggested that the virus was hardy enough to withstand the physical impact imposed by this high volume sampling system.

Yes, one really should clean the tester after each sample.

Samples 3-6, which also were positive on the original PCR were not believed to be true positives, but rather resulted from the ?flushing? of residual material remaining in the sampler from samples one and two. This was supported by the rapid decrease in the concentration as determined by the semi-quantitative PCR, with samples 3 and 4 being two logs lower and with samples 5 and 6 being negative with the less sensitive PCR. The sampler was decontaminated after sample 7.

Although slit sampling technology has been successfully used for the collection of SARS virus indoors, it was not effective in collecting Avian influenza virus outdoors, as shown in this situation. The concentration of any circulating virus 75-100m from the barns was probably too low to be collected by the relatively low flow rate (30 lpm) of the slit samplers. In addition, the concept of using a fixed sampling position based on the forecast prevailing winds was not optimal as the local micrometeorology (interaction of wind with buildings and trees around the sampling area) resulted in shifting winds and dispersal of air from the barns (figure 3) at least 5-10m above ground level and far above the samplers.

[Malcolm]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Excuse me mixin.

Negative in the outside air----I am not surprised they found it in the barn air.

MOISTURE is KEY to viral survival.

Influenza virus is not gong to blow in anyone's open window and infect them.

DRY dust and feathers could not carry viruses past one day.

WATER is a crucial carrier of viruses and needs significant study.

[Oracle]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Testing for AI in nearby water bodies two months after the initial outbreak isn't likely to capture a transient wave of HPAI. You will only find low concentrations of residual LPAI - this has been repeatedly demonstrated in recent years. When you test is as important as where you test.
The concept of testing when a viral population subset is most likely present is not a difficult one.

The comment on 'moisture' requirement for viral survival is quasi-correct; a viral lipid coat with a slow melt crystalline phase (broad melt temperature) does wonders for protection against freezing and dessication.

[Malcolm]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

viral survival on surfaces

http://www.pandemicflu.gov/plan/healthcare/influenzaguidance.html

Management of Environmental Surfaces

Background: Environmental Reservoirs and Hand Transfer of Virus
Influenza A and B viruses can persist on dry environmental surfaces, both porous and nonporous. Laboratory studies conducted to evaluate this persistence document survival periods that vary widely in length, depending on environmental factors. Low relative humidity levels (e.g., < 50%) and cool, ambient temperatures are associated with longer periods of activity. Influenza A virus can survive on hard, nonporous surfaces (e.g., stainless steel, hard plastic) for 24 ? 48 hours and on porous materials (e.g., cloth, paper) for < 8 ? 12 hours in ambient temperatures (1). Virus persistence on surfaces increases up to 72 hours when those surfaces are moist or wet (2).

http://www.ncbi.nlm.nih.gov/pubmed/17494568

Persistence of H5 and H7 avian influenza viruses in water.


Oracle--I could use some links for your statements of fact. I disagree with almost all of them!

[mixin]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

The positive sample 10 was notable in that it was not collected at an infected premise but as part of a random collection of samples in different parts of Abbotsford. It was collected in an open field approximately 800 m away from farm B. We felt this was a true positive since samples 8-9 and 11-16 were all negative showing that there was no possibility of any cross contamination between samples. Although positive by the original PCR it was shown to be negative by culture and by the less sensitive semi-quantitative PCR. This indicates that the concentration was very low. Since the sample
was collected during daylight hours it was unlikely to find live virus in the sample. Any viable virus would probably have been inactivated by sunlight.

I really would like to see testing on airborne particles done again with proper equipment.

[Malcolm]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

I really would like to see testing on airborne particles done again with proper equipment.

Mixin---if there is no moisture and sunlight hits an influenza virus---it is soon destroyed.

The foremost human influenza transmission danger will always be your own hands, and/or being coughed and/or sneezed on once a pandemic begins. Think about viral load---the outside and open air will never contain sufficiently high enough quantity of virus to infect a human being.

That is the basis for the age old practice of airing out a room.

[mixin]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Large chicken operations can be pretty nasty places and I'm not sure if all the stuff that flies through the air is totally dry. The above test did find virus on dust outside of the barns so I'm not conviced it would be impossible for transmission in that manner. If the fans are running at night, with a gentle breeze blowing, the dust particles could travel quite a distance.

I just finished a lengthy Canadian study on the transmission of seasonal influenza and the panel found very little proof in the studies it reviewed that *hands* or *long-range* were likely methods of transmission; but they didn't rule the possibilities out. Most likely, kissing or coughing/sneezing on a person spreads the virus.

[Malcolm]

Re: Canadian Govt: Large Saskatchewan Chicken Farm - Highly pathogenic H7N3

Please post your study, mixin----and other links for your controversial data as well. I disagree with it. The positive virus they found outside was not viable.

Hands are number one viral carriers--colds, flu, norovirus, etc.