The bird flu influenza subtype, H5N1, that has been infecting humans with high mortality is the highly pathogenic (HPAI) version of a virus that also exists in a low pathogenic form (LPAI). The high and low path designations refer to effects on poultry, not humans, but only the HPAI versions have been of public health importance. On the other hand, the HPAI strains have all come from LPAI ones via a variety of genetic mechanisms and LPAI strains are themselves of importance to the poultry industry where they decrease productivity of the flock. For these and other reasons there is a need to see if a flock is infected with an LPAI influenza virus subtype. One way to do this is to take blood from a designated bird in the flock to see if it has developed signs of LPAI infection. Since these birds don't get much in the way of symptoms, this often means seeing if they have developed antibodies in their blood to the virus, but it takes time for antibodies to develop after infection and it may take a fairly heavy viral inoculation to get an antibody response. The bird could still be infected with a smaller inoculation but not develop detectable antibodies. Now a new paper in the CDC journal, Emerging Infectious Diseases, reports on how to create a "Super Sentinel" chicken, one that develops antibodies to LPAI faster and with a smaller inoculum than a normal bird.
The key to the Super Sentinel is to put a biologically active protein in its water that enhances the immune response. The protein is a genetically engineered form of chicken interferon (IFN) α which modulates the sentinel chicken's immune response, enabling a faster and more sensitive immune response. The scheme was tested with chickens that were infected with an LPAI H7N2 subtype that had infected commercial flock of laÂ¥ing hens in Connecticity in 2003, causing a drop in food consumption and decreased egg production. But the diagnosis then had been long delayed ( 6 -7 weeks). In this new paper, the authors (Girshick, van der Heide and Sekellick) from the University of Connecticut infected some birds and then caged them with uninfected birds, half of which were given interferon-α laced water and half not. In four independent trials the authors demonstrated that of 16 treated birds caged with two infected ones per cage developed antibodies, 14 developed antibodies within two weeks, while the untreated birds (no interferon in their drinking water), none developed antibodies over the entire 28 day period of the study. They conclude:
Super-sentinel chickens would thus provide a novel means of detecting otherwise inapparent infections of LPAI, thereby buying time for its control or eradication. We envision the introduction into a large flock of a number of small cages containing chickens in which IFN-water replaces plain water. These super-sentinel chickens will serve as sensitive early detectors of LPAI, like the proverbial canary used in mines to detect low levels of toxic gases. Because of the cross-reaction between chicken and turkey IFN-α, super- sentinel turkeys could likely be created in a similar manner. Super-sentinel birds could be replaced every month and possibly returned to production. All strains of chickens tested, including those in the People's Republic of China, have proved to be sensitive to the action of [IFN]. Genetically engineered production of [IFN], treatment with it optimized for dose and duration, and its long half-life in water may make it economically feasible to convert many birds in a flock to super-sentinel status. It also may be prudent to set up super-sentinel birds in areas of high risk for avian influenza virus outbreaks, such as live-bird markets. Surveillance of other families of birds might be possible with species-specific IFN. Further studies are required to test these possibilities and the extent to which rChIFN-? functions as an adjuvant with other strains of avian influenza virus and chickens. (Garshick et al., Emerging Infecitous Diseases; ePub ahead of print)
So this is another arrow in our tiny quiver of preventive measures for detecting and controlling infection in birds, the principal reservoir of influenza A/H5N1 and other subtypes of public health importance. The field is moving forward. Only history will tell if the virus or the humans are winning the race.
I can see is a forest fire on the next ridge...and researchers standing in a row, confidently chatting while holding on to their water-pistols.
In other words...there seems to be a large divide between the theoretical and the practical.
"Epidemiologist says: Thin out sick chickens
Virus says: Thin out stupid people."
Racter Mar 2006.
Super Sentinel Chicken, with his sidekick Fred. To the Super Coupe.
Revere-Its the annual take the vaccination and the pneumovax question. The Gerberdinator says that they are about to ship 130 million doses of the lastest flu vax. So we take the pneumovax each year automatically. Whats your read on the latest vaccine? Is it B with loadings for some A, or is it just last years vaccine sexed up for what they think will happen. Two years ago it was the equivalent of taking an aspirin. No benefit apparently. Also the Gerberdinator said that if you take this it will stop the flu? Now she's a doctor and I am not but I could tell from her tone listening to the briefing that her heart wasnt in that statement. What gives? Do we take it or not? Tom DVM indicates it might be a bad idea for poultry. Whats the difference between a bird and a human?
This is good news. Even though it's only good in detecting the virus in birds, it's still the best thing we can to prevent the virus from spreading.
This is wonderful. Now we can detect the virus earlier and take necessary steps before it spreads and take out more chickens.
Easier is to vaccinate all industrial poultry living longer then 6 weeks.
Those have to be monitored anyway, sentinel chickens are common stuff amongst them. We have that here for 2 years now for free ranging laying hens. Sentinel chickens/animals must be held apart because of bleeding after taking a bloodsample. The other chickens will jump on the bleeding collegue and kill it cause vets don't work in the evening when a bit bleeding isn't a problem because all birds are asleep.
LPAI is just as dangerous in industrial stables as HPAI because a low pathogenic one can easily mutate in a HP one. Thats what happened in Holland in 2003 when LPAI H7N7 mutated into a killing virus. The strange thing is that only layers and broilers got ill and died within 1 or 2 days in a nasty way. The virus was ineffective on backyard fowl. So old chicken breeds, fancy crossbred chickens, ducks, geese, etc, not one individual got sick.
Nevertheless 160.000 pets were killed without a test, and without a trace of illness.
Same in Germany a few weeks ago. September 2006 there was found LPAI H7N7 antibodies and bit virus again in the same region in Holland. They culled all chickens.
It was kept silent which virus type was found to prevent panic amongst the people.
Therefore here its allowed to vaccinate backyard flock and free ranging (commercial) laying hens.
Preventive vaccination against H5N1 will minimize the danger and breeding broilers and layers with a better immunesystem (like backyard flock and old breeds) can prevent mutating a LPAI virus. When the way of housing of industrial birds is changed too (no more mass stables), there will be no more pests, just like in the old days. Todays poultry industry is a dead end road. And the taste is terrible.