Q&A with Dr. Elise A. Myers, Technical Services Manager, Merck

 Q1: What is the link between IBV, vaccinations, and E.Coli infections?

 Escherichia coli (E. coli) are generally considered to be opportunistic bacteria. This means that in order to infect and cause disease in birds, there generally has to be some other disease or factor that “opens the door” creating conditions that are favorable for the E. coli bacteria. There is an incredibly long list of factors that have been shown to increase the chicken’s susceptibility to E. coli, including:

  • The host’s immune status (ability for immune system to respond to challenge);
  • The presence of mycotoxins in feed; and
  • Infections with some viruses.

This means that when we are troubleshooting an E. coli issue, we need to look at reducing the number of potential risk factors that may increase the birds’ susceptibility to E. coli. With the elimination of each additional risk factor, we get closer and closer to “closing the door” on E. coli.

One of the first things that we often address in these situations are improving cleaning and disinfection practices as well as improving water sanitation. However, once these basic elements are taken care of, we need to dig a little deeper.  This first means designing a vaccination program and managing the bird to protect the immune system. For example, excessive periods of stress (environmental, social etc.), and viruses like Infectious Bursal Disease virus can impair the immune system, reducing the bird’s ability to respond to vaccinations and also to field disease challenges.

A more specific consideration for this discussion is the design of your respiratory vaccination program with respect to timing and application of live vaccines. When done correctly, the reaction from a live bronchitis vaccine in the airsacs of the bird should clear in approximately 9-10 days post-vaccination. However, too often we think of a multi-age site as separate, individual barns, and fail to consider the potential for movement of vaccine virus between barns. In other cases, we achieve such poor coverage during application of vaccine that there are populations of birds within a barn that do not receive the vaccine, and receive their first “exposure” to bronchitis virus after it is shed by other birds in the barn. This can lead to prolonged reactions in the respiratory tract, and this “opens the door” for E. coli infection of respiratory origin. When this occurs, the E. coli infection may spread from the respiratory tract to other body systems including the reproductive tract, leading to egg-yolk peritonitis (1). Because we so often see this link between respiratory disease and E. coli infections, it is important that all of the birds in a poultry house or, on a multi-age site, achieve uniform protection against respiratory pathogens at the same time.

 Q2: How has this problem typically presented itself?

Most often this problem is observed when birds are stressed and coming into peak egg production. We often, but not always, notice a drop in production closely associated with subsequent elevated mortality. Mortality generally is diagnosed as “Colibacillosis” or E. coli infection. On closer examination of diagnostic tests, it becomes evident that these events are associated with repeated bronchitis challenge.

Q3: Why does it show up most often in loose housing?

 Since there are so many risk factors involved with the development of E. coli infections in poultry, it is not surprising that birds in alternative systems tend to experience more challenges than we were accustomed to in conventional systems. One of the major challenges that we see with loose housing, particularly in dry climates, is dust. As birds navigate the system and exhibit normal behaviours such as dust bathing, there is a large amount of dust that is created in the poultry house. 90% of dust in poultry barns has been reported to be in the respirable range (meaning it can be breathed in) so the possibility of bacteria, along with other biologically active compounds (endotoxins, spores etc.) reaching the respiratory tract of these birds is high (2).

In addition to the great deal of dust present in these systems, achieving good, uniform coverage with respiratory vaccines (Infectious Bronchitis and Newcastle Disease) can be particularly challenging. Birds in these systems occupy different spaces of the house at different times of day, and are not always uniformly distributed throughout the house. For this reason, spray vaccinating these types of birds requires careful consideration of bird behavior and the development of a farm-specific spray vaccination plan.

Water vaccination in these systems can also prove challenging when we consider the volume required to do so, and the temperature requirements of these types of vaccines. Recent research from the University of Georgia showed that when bronchitis vaccine was prepared with room temperature water, titer dropped 1 log immediately, and gradually declined to 0 (3). In a study of the efficacy of infectious bronchitis vaccines in the field they found that for every 1°C higher temperature between 6-18°C, there was an average 3.2% lower antibody response (4). This means that if we are using room temperature water to reconstitute our vaccine we have a potential 48.1% reduction in antibody response! Even if every bird does drink at the water line or gets sprayed by the sprayer, if the vaccine has already been killed by mishandling, we have still not effectively vaccinated our flock. Poor vaccination leaves our birds not only open to field infection, but also increases our chances of having “rolling vaccine reactions” that can in turn leave birds being more susceptible to E. coli infections. Again, in order to prevent prolonged or “rolling vaccine reactions”, we need to aim to get every bird in the poultry house vaccinated at the same time with a protective dose of vaccine.

 Q4: What should a producer do as first steps if they suspect this might be an issue on their farm?

If a producer suspects that their flocks may be experiencing repeat E. coli infections, the very first thing that they need to do is to rule out the basic management-related sources of E. coli. Consider cleaning and disinfection practices, water sanitation, and dust levels in the barn. Low relative humidity can be particularly problematic when trying to manage dust levels, so steps should be taken to address any excessive dust. Next, producers should involve their veterinarian to evaluate how they are doing “now” with their current vaccine program and vaccination practices, and to identify where there may be room for improvement. Most often this will involve serology (bloodwork) to measure the type of responses to commonly encountered diseases that your flock may have encountered. A local veterinarian can be a powerful tool when tackling this type of issue because they will have knowledge of current disease challenges in the area and can help build a personalized vaccination program to address any issue identified on serology or farm visits. Following any changes to vaccine handling, application, or changes to the vaccination program, additional testing will be required to continue to measure your success.

I would strongly encourage serological testing on a regular basis, not only to measure your progress as your personalized program develops, but also to gain an understanding of what your “normal” looks like in a good flock compared to a bad flock. By having a baseline, your veterinarian can have a clear picture of what your farm should look like, and make more rapid decisions in the face of health challenges. In addition, submitting birds for necropsy, or simply saving your mortality for your veterinarian to evaluate on a farm visit can allow for the collection of other types of samples (swabs, tissues) that can help your veterinarian to rule out any concurrent disease challenges.

Q5: What are the most critical factors for success producers should consider when building their vaccination plan?

 It is important to distinguish between a vaccination program and a vaccination plan. When we say vaccination program, this is something that will be determined by a veterinarian who understands the farm and local disease challenge. A vaccination program involves the selection of products to be used, target ages for use of each product and application methods. The vaccination plan should be created using the vaccination program as a backbone, and should focus on things like vaccine handling and application, in other words “how you’re going to get it done”.

A vaccination plan has two main goals: 1) keep the vaccine alive and 2) deliver it to all of the birds. In order to keep your vaccine alive, your vaccination plan should take into consideration vaccine-specific factors like the sensitivity of vaccine to temperature, as mentioned above. Other vaccine specific factors include things like pH, with viruses like infectious bronchitis virus surviving better at a pH of 6.0 than pH of 8.0 (5). For this reason, many producers now use refrigerated distilled water, which tends to be slightly more acidic than most dechlorinated municipal water coupled with a vaccine stabilizer for spray vaccination.

A vaccination plan that includes water vaccination via pump and tank may require more ingenuity, such as freezing blocks of water treated with stabilizer tablets to add to vaccine tanks to help prolong cool water temperatures and in turn extend vaccine survival. Stabilizers that contain dye may be particularly useful when establishing how uniform your vaccine uptake may be since they allow for tongue staining checks of birds following vaccination.

Further considerations include things like whether or not the lights are turned on, dimmed or turned off during vaccination. We know that lights-on during vaccination increased IgM antibody response by 41% (4), but some flocks may require adjustments to this recommendation due to flock behavior. Likewise, we know that having the ventilation turned off during spray vaccination increased IgM antibody response by 15.5% (4); however, environmental temperatures at some times of the year may require adjustments to your plan. Getting good coverage may also require more than one vaccinator in the barn. We know that larger flocks can be more challenging to vaccinate with research showing a 1% lower IgM antibody response for every 1000 bird increase (4). Therefore a “practice run” using only water with stabilizer may help to determine at what pace you need to walk through the house with your particular sprayer and what kind of coverage can be achieved.

It’s important to continuously measure and review your progress with your veterinarian to be sure that your vaccination plan and program are meeting your farm specific needs.

Q6: If IBV vaccinations cause so many problems, wouldn’t it be better/easier to just not vaccinate?

 We need to remember that the problem with rolling or prolonged vaccine reactions with the products that we have registered in Canada have less to do with the products themselves and much to do with how these products are handled and applied. All vaccines are tested for safety and would not gain approval for their registered use if they were known to cause disease. When handled and applied appropriately, vaccines do exactly what they were intended to do- prevent the severe disease that can result from infection with field viruses. Problems arise most often when vaccines are mishandled and applied without consideringthe potential for the development of rolling reactions or when birds that are not suitable for vaccination (ex. sick birds) are vaccinated.

Although some regions have less field virus challenge than others, the decision to vaccinate and the development of a vaccination program should be one made with your veterinarian based on the known risk of a particular disease in your region. In most cases, the consequences of potential secondary infections following poorly applied vaccine are minimal compared to the potential costs of a field bronchitis challenge.

Q7: Who can I go to if I have further questions about this issue?

 For further information, please contact your local veterinarian!

Special thanks to Leanne Cooley of LH Gray & Sons Ltd and Greg Brown of Archer’s Poultry Farm

References:

1-World Poult. Sci. J. 53: 351-368. 1997

2- Poultry Science, Volume 91, Issue 3, 1 March 2012, Pages 604–615

3- Dr. Brian Jordan, University of Georgia 2015

4- Avian Pathology (April 2010) 39(2), 123-131

5- Diseases of Poultry 12th Ed, 2008