Infectious Bronchitis

by K. J. Theodore



     Chickens do not suffer from the Common Cold. Your bird may have one of many upper respiratory ailments, such as Infectious Coryza, Infectious Bronchitis, a CRD, or perhaps some other form of respiratory distress including bacterial, fungal, or viral infection. But chances are, they donít have the Common Cold.

     Since Iíve already written about Infectious Coryza, Iím going to concentrate this time on one of the other possibilities, INFECTIOUS BRONCHITIS, since it is the most contagious.           

     Infectious Bronchitis (or IB) is a common viral disease of the Coronaviridae. Coronaviruses are typically specie-specific and IBV only effects chickens. Waterfowl kept in the same housing as an infected chicken flock are not at risk. It would also be extremely rare to find a chicken IB virus isolation within other poultry such as turkeys, etc.

     IB is found worldwide but in varying strains with more emerging all of the time. This is why vaccination is not always effective. Most vaccination programs will include strains specific to your particular area of the world, but it is sometimes difficult to include all of the strains that are also emerging in that same area. While vaccination may be a good prevention measure, you must accept the fact that your birds could become exposed to a strain not covered by the vaccination. To avoid maternal antibody resistance to vaccination, chicks should be vaccinated for IB at the age of two weeks.

     The primary target of the IB virus is the trachea, which results in tracheal rales (rattling), but also includes such symptoms as coughing, sneezing, chirping, and a loss or reduction in egg production. Less common symptoms include a nasal discharge and wet eyes. Some sinus swelling may also occur but this is rare and usually only seen in very young chicks. In some hens, you may also find a fluid (yolk) buildup in the abdomen. Not all birds will show symptoms. But ALL birds will have the virus.

     In a more virulent strain, IB can attack the kidneys and in these cases, the bird will typically show no upper respiratory symptoms but will become drooped (tail down). In these cases, death is almost certain within 24 hours and there is almost nothing you can do to reverse the kidney failure. Another possibility that includes the kidneys is if the bird recovers the initial upper respiratory symptoms, but then fails later due to kidney damage that was caused by the virus. The virulent strain that attacks the kidneys can usually be confirmed by necropsy with the finding of kidneys that are swollen and pale. It is not uncommon to have more than one strain of IB infect the same flock at the same time.

     Infectious bronchitis is highly contagious and its rate of spread can sometimes be used as a strong determination of which of the various diseases a flock has when upper respiratory symptoms occur. It would not be uncommon for the entire coop to be infected within 24-48 hours. If a bird on one end of your coop shows severe upper respiratory symptoms one day, and a bird on the very opposite end becomes ill within 24 hours, chances are that you are dealing with IBV. Exposure usually occurs from aerosolized virus particles that are put out into the coop air by sick birds. The virus has also been known to travel approximately 1,200 yards on the wind. However, initial infection is probably caused by one of two routes Ė exposure to a sick bird at a poultry show or swap or exposure to a carrier that comes into your coop that has come from another flock that is either currently ill or was very recently ill. Although a carrier state has been confirmed with IB, it is not the primary source of infection since the shedding of virus post infection lessens with time, and it is even possible to produce IB-free chicks from infected hens.

     Airsacculitis can develop as a common secondary infection with IB. The disease can also cause poor weight gain and a severe drop in potassium and sodium may occur. Since IB is a viral infection, there is no treatment. However, in order to combat some of the problems that occur as a result of the infection that have the potential of causing death due to the combination of factors, there are some things that you can do. One of them is to treat the entire flock for secondary bacterial infections with a water-soluble broad-spectrum antibiotic for 7-10 days. Tetracyclines and chlortetracycline may be effective for this purpose. If you have a particularly valuable bird that is showing upper respiratory symptoms, then treatment with a broad-spectrum injectable antibiotic may be more effective. Run the full course though, as they usually show marked improvement after just three days of treatment. If the bird is only showing a drooped posture with no other symptoms, then I would not subject them to antibiotic treatment since it cannot be processed properly if the bird is suffering from kidney failure. Youíre best advised in these cases to either cull or isolate, keep warm and well fed and watered and stress-free to see if the bird pulls through. It would be rare if they did though once they reach that stage.

     Another action you can take is to provide supplementary heat if the weather is cold. Cold stress is a major factor in the birdsí ability to recover from IB. If weather permits and cold stress would not occur as a result, then a complete air exchange of the coop with fresh air once a day during infection would be beneficial to keep the viral count down in the air. Another very important action you can take is to fog the coop with Oxine three times a day through the duration of the infection. You will be reducing the viral particles as you fog and any fog that the birds breath in would help reduce some of the virus in the trachea that is present. Unfortunately, this only works if the temperature is above freezing Ė otherwise, guess what you get when you fog? Yup Ė snow!

     To combat the drop in potassium and sodium, a good electrolyte (minerals) supplement should be provided right away. In some cases, you may have to provide the supplement separately from the medication since some medications are not as effective in the presence of calcium. Creative thinking should play a role here. A good probiotic and vitamin supplement will surely help as well.

     Since IB is sensitive to most common disinfectants, cleanup after an infection should not be a problem. If you are able to fog through the illness, chances are that youíve already been cleaning up the virus as you fogged. Recover usually occurs around two to three weeks after initial infection.

     A lifetime side effect of IBV in hens is a potential for the reduction in lay and/or quality of the eggs she does lay. For example, the eggs may have reduced hatchability, inferior whites (watery and broken), loss of pigment, and rough or soft shells. You should be able to tell after full recovery and full return to lay.

     One of the things about IB that I found interesting is that it appears to be more or less severe based on a specific breed, breed variety, and/or sex (males are more likely to die than females). I also found it interesting that although there is no human health risk with IB (the IB virus in chickens is significantly different than the human bronchitis virus), it is not uncommon for neutralizing antibody titers to be found in the blood of those who work with an infected flock. Thereís no known significance to this fact but I found it interesting that even though we cannot get IB from our chickens, we will build immunity to it.


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