News flash: laryngotracheitis (LT) has been spread to backyard flocks by vaccinated birds.  Birds which have been vaccinated with one of the vaccines which cause a carrier state may not be sold or exhibited.  Read your label before you vaccinate!!!  You may do more harm than good.


by Cynthia Smith, DVM

   Commercial layer flocks are vaccinated against many diseases, usually on multiple occasions and often as an aerosol administered to hundreds or thousands of birds at one time.  These birds are tightly confined, genetically similar, and heavily crowded- all prescriptions for rampant disease outbreaks.  Consequently, large scale producers practice extreme biosecurity (not even allowing employees to own or have contact with other poultry,) all in- all out housing (never mixing birds of different ages,) and prophylactic use of antibiotics.

   Backyard poultry lovers, on the other hand, never take their birds anywhere and may have only a few birds, all purchased as chicks.  Many of them have never heard of vaccines for chickens.

    We small flock hobbyists,  on the other hand, deliberately take our birds to shows and fairs- where they are exposed to other birds for days at a time, often mix different ages of poultry in our flocks, and  may buy adult birds from across the country- potentially introducing new groups of diseases from who knows where.  It is not surprising then, that our needs for vaccination are quite different.

   As a veterinarian, fancier, and exhibitor, I have been researching this topic.  I will warn you that I still consider myself a novice, having gotten my first purebred poultry just a little over 4 years ago.  Nevertheless, here are some of my thoughts thus far.  No doubt they will change as I learn more on the subject.

Marek's Disease (MD)

This debilitating illness claimed the lives of over a dozen of my silkies when it was first introduced to my flock after I purchased 2 new birds from Louisiana a few years ago.  Signs of MD include tumor development and neurological signs such as paralysis of a leg or wing.  Often, birds with MD just fade away, sitting in a corner, hunched, with feathers fluffed, while the weight just melts off their bones.  MD is spread via feather dander and is endemic in most flocks of exhibition poultry.  How much damage it does depends on a number of factors:

1.  Genetic Susceptibility-  Some breeds, such as silkies and sebrights, are known for their susceptibility to this disease.  Some lines within a breed may also be less resistant than other lines.  My Polish were always extremely resistant to MD.  I never vaccinated and never lost a bird until I bought some lovely birds from a different bl oodline.  The losses among these individuals were so dramatic that I now vaccinate every chick I hatch for Marek's, rather than just the silkies as I originally started out.  On the other hand, many breeders argue that, by vaccinating and then breeding these birds, we perpetuate genetic weakness.  They are, of course, quite correct.  The Darwinians among us recommend that we vaccinate none of our birds, breed those that survive, and thus produce healthier birds down the line. There is much to be said for this philosophy, particularly in those breeds already noted for their hardiness.  Those who pride themselves on producing heritage and free-ranging breeds, for instance, may wish to deliberately choose NOT to vaccinate, specifically in order to weed out weaker individuals from the genetic pool.  Alternatively, those of us who breed "hothouse varieties," such as Polish and silkies for exhibition, already recognize that these birds, at least with the extreme features (such as large crests) necessary to be competitive, are already man-made creations not adapted to survive in the wild.  Breeders of these varieties are far less likely to be willing to sacrifice what are often the best conformed individuals in a hatch to what is essentially a preventable disease. Similarly, pet poultry people find heavy losses to disease emotionally draining and unacceptable.  They too are likely to vaccinate rather than watch a proportion of their pets die unnecessarily.

2.  Exposure before the age of 16 weeks- Older birds are far more likely to survive infection with MD.  Therefore, experts recommend not mixing birds of different ages, or at least waiting until young birds are 5 months old to introduce them to the flock.

3.  Other poultry- Running turkeys with your chickens is a time-honored way to naturally vaccinate against MD.  Turkeys carry a similar virus which is not p athogenic to chickens but which is genetically similar enough to induce an immune response to the real Marek's virus, rather like cow pox vaccinates humans against small pox.  While it is beneficial to the chickens, co-mingling these 2 species constitutes a risk to the turkeys, as chickens may be a source of the organism which causes "blackhead," a fatal disease of turkeys.  For this reason, many breeders raise the two species separately, but then "salt" the chick feed with dried turkey manure in order to impart the same protection without endangering their turkeys.

Assuming one is neither a Darwinian, nor a turkey-fancier, vaccination against MD is the logical course.  Chicks purchased from a hatchery can arrive vaccinated for a small fee.  The breeder must, however, vaccinate the chicks he/she produces.  As the vaccine itself is inexpensive-about $19-though overnight shipping on ice often raises the price significantly- the small pr oducer's question is more often, "What the heck do I do with 1000 doses?" The vaccine is labelled for use on day-old chicks only.  The small breeder may hatch only a few chicks each week and end up throwing away 98% of the vaccine.  This does become cost-prohibitive in a short time.  Many breeders attempt to split the vial of vaccine, but I have always considered this risky.  Live virus vaccines are notoriously easy to kill and what is the point of vaccinating at all if the vaccine becomes ineffective?  I recently attended a conference on pet poultry medicine, where I was assured by several top people in the field that the MD vaccine is equally effective whether the chick is 1 day, 1 month, or 1 year old.  The trick is that the vaccine will, of course, be rendered ineffective if the bird has already been exposed to MD.  I generally hatch chicks from February until April, then vaccinate everyone at once, along with vaccinating any newly acqu ired chicks or adults at the same time.  I usually call in reinforcements (my 4Hers) for this in order to get through the process in under an hour.  Usually with 1 kid holding birds and the rest taking them out and putting them back in their pens, we go pretty quickly.  I use tuberculin syringes (1 cc total) and preload them with 5 doses.  Then I vaccinate each chick with 0.2cc at the nape of the neck.  By the time I get around to vaccinating, I've usually culled a fair number of my chicks, so the chicks which are sold/given away before the process are not vaccinated.  This year I hatched about 300 chicks but only vaccinated 86.  I always intend to finish hatching by April 1st, always change my mind about a few batches, and end up doing one more follow up round of vaccination for the stragglers.

Fowl Pox

This is a horrible disease-very painful for the birds involved and often, though not always, fatal.   The disease is primarily blood-borne, being spread by mosquitoes and fight wounds.  The stunning little show bird I bought last summer got into a fence fight with another rooster.  It took me a long time to realize that the 2 birds' fight wounds on their faces and combs were not healing because they were now infected by fowl pox.  It was mosquito season here, so by the time I figured it out,  8 good birds, including the expensive Florida import who started the whole thing, were dead.  Many others were saved with good nursing care.  Pox lesions start out looking like a vesicle or blister, then crust over.  There are wet and dry pox forms- primarily relating to whether the bird has internal lesions as well as external.  The wet or internal form is more likely to be fatal.  We stopped the cycle by vaccinating every bird on the place, and you can bet I will continue to vaccinate yearly rather than ever go through that again!  (No tice how all my lessons seem to be learned the hard way...)

This vaccine is given in the wing web with a nasty-looking little 2 pronged instrument that you poke all the way through the wing.  It's pretty creepy the first few times.  There are 2 different vaccines: a weaker vaccine for use in birds as young as one day old, and a vaccine for birds over the age of 6 weeks which produces a longer lasting immunity.  This year, I used the weaker product.  Several young birds and adults still became ill- sitting all fluffed up in a corner, obviously feeling poorly.  I saved all of these birds as long as I took them inside for a couple of days and gave them a little TLC (vitamins, food, warmth, etc.)  The one bird I procrastinated on did die.

Laryngo-trancheitis (LT)

As I write this, the LT vaccine lingers in my refrigerator, unused as yet.  When I attended the Polish and silkie nationals in Tennessee last year, I heard multiple horror stories about this virus wiping out entire flocks after a show.  The problem is that LT vaccine is generally administered as an eyedrop- a live virus given directly on mucus membranes.  It works by actually causing a mild form of the disease and renders the bird a carrier.  I have been reluctant to use this vaccine precisely because I often sell or give away birds to other fanciers and I have no desire to cause them trouble by sending in a carrier  bird to possibly infect their clean flock with LT.  I also feel a vaccinated bird is a real risk to the unvaccinated bird in the cage next to it at a show.  Indeed, it may actually be the practice of vaccinating for LT which is responsible for the frequent show-related outbreaks.  I have been very interested in the 2 "vector" vaccines, which incorporate part of the LT virus in a larger virus in order to vaccinate for both diseases without creating a carrier sta te for either.  These are now in commercial use.  One of these incorporates a vaccine for MD with LT.  The problem with this vaccine is that it must be stored and shipped in liquid nitrogen, raising the cost to astronomical for the small producer.

The second vaccine is more promising, this is Vectormune FP LT- produced by Ceva.  This vaccine- given in the wing web and stored at regular refrigerator temperatures- would protect against both fowl pox and LT without producing a carrier state.  It can be purchased only from the company in lots of 10 and must be used within an hour like most of the other vaccines.  I believe cost was about $50-$60 a vial.  I tried to get other fanciers to go in with me on the product, then contacted Peter Brown, DVM at First State Veterinary Supply to see if his company would consider carrying the vaccine for individuals to purchase in smaller lots.  It was his opinion that the vaccine may no t provide adequate protection against  LT,  He advises vaccinating with a product known as LT-IVAX, produced by Schering Plough.  Although this vaccine is again, a live virus given as an eye drop, the company claims it is a greatly weakened vaccine which will not produce a carrier state as will the other eye drop vaccines.  As I said, I have yet to use it.

In summary, should you vaccinate your small flock?  If you never bring in adult birds and practice strict confinement after shows and fairs, maybe not.  On the other hand, it is a terrible thing to watch your birds die from a preventable disease- I should know.  An important caveat is that all these vaccines are live viral vaccines and, as such, potentially contagious to other birds while their bodies are establishing immunity to the pathogen.  Therefore, timing of vaccination is critical!!!  Don't be like me and get up one Saturday, say, "Oh, I think I'm finished hatching, let's vaccinate everyone," only to realize that evening that you've just knocked every chicken  you own out of the big Spring show the following month.  Birds should not be vaccinated within 60 days of a show to be safe and some birds, which are known carriers, ought not to be exhibited at all.  I hope my experiences, and mistakes, may be useful to someone else.

Cynthia Smith, DVM

Fowl Pox