Bovine respiratory disease (BRD), or pneumonia, is the most common cause of death in cattle over 4 months of age. A variety of commercially available vaccines are available to protect against the microorganisms that cause BRD, but cattle can still contract BRD even when vaccinated. This article reviews some of the more common causes of perceived or actual BRD vaccine failure or lack of efficacy.
Senior Technical Services Veterinarian / Vaxxinova
Set expectations
First, we need to understand what is and is not a failure of the BRD vaccine. In the field of herd production medicine, is a BRD-related illness or death of one or two calves a failure? If you only have a few calves, it may seem that way. In production systems where hundreds or thousands of calves are reared and fed in the background, the loss of one or several calves in a group can be considered a major success. may be considered. Some production systems using very high-risk calves may tolerate morbidity or disease rates of 30% to 40% and mortality rates of 10% to 15% or more. For other production systems that purchase low-risk vaccinated calves or background calves, less than 5% to 10% disease and less than 2% to 3% mortality may be the goal. Importantly, the amount of disease and mortality that can be tolerated depends on the type of cattle purchased, the producer’s risk tolerance, and the management system.
We also consider response to treatment. Calves vaccinated against BRD respond better to treatment than unvaccinated calves. If a group of vaccinated calves develops BRD but recovers with less treatment, has lower mortality, and requires less labor and drug costs than unvaccinated calves, then Is it considered a failure?
The calf has pneumonia but has been vaccinated
Bovine respiratory vaccines may fail for several reasons. Causes usually fall into one of three general categories. Either animals fail, vaccines fail, or humans and management fail.
animal failure
The term nonresponsiveness or primary vaccination failure refers to the failure of a normal healthy animal to mount a sufficient protective antibody response after primary or booster vaccination. This phenomenon affects approximately 2% to 10% of healthy vaccinated people.
In young cows, the presence and interference of maternal or colostral antibodies with the response to vaccination may also reduce the response to vaccination. Generally, calves younger than 3 months of age are under the protection and influence of colostrum antibodies received at birth. Historically, veterinarians have been educated and producers have been instructed not to vaccinate calves under 3 months of age due to maternal antibody interference. More recent data indicate that this is not the case for the use of modified live vaccines (MLVs). Vaccination at a young age may be beneficial. It’s frustrating when the biggest, most magnificent calves get sick with BRD. These calves are often the oldest calves with lower maternal antibodies and defenses than younger calves.
First heifers tend to have lower colostrum quantity and quality than more mature cows. Heifers also have less maternal experience than older cows in the herd. Calves born to heifers tend to have lower maternal antibody levels and a higher risk of BRD than calves born to adult cows. It is common for BRD to affect heifer calves more than adult calves.
Vaccines do not stimulate immunity
The quality of the vaccine itself is very important. If the vaccine is not manufactured properly or there are problems with the antigen used, it may not produce the desired immune response. Fortunately, all commercial and autologous vaccines are manufactured under USDA licenses intended to ensure vaccine quality.
Using a vaccine that is not compatible with the target microorganism (antigen) or the specific pathogen strain present in the herd may provide insufficient protection. Antigen problems occur more often than many people realize. Complete BRD protection against all possible pathogens is not available in a single product or injection. Do not expect protection against microorganisms not included in the vaccine used. Mutations in biological strains are also a major concern when a lack of vaccine efficacy is suspected. The article “The Importance of Strain Variation in Vaccines” by Randy Sherbraun in the May 2024 issue of Progressive Cattle explores how strain variation in organisms can negatively impact the effectiveness of bovine respiratory vaccines. It provides an excellent overview of what’s going on.
Vaccines can contain either MLV or inactivated killed bacteria. Although MLV contains microorganisms that have been modified by the manufacturer to not cause clinical disease, the microorganisms can still replicate in the animal and stimulate immunity after vaccination. MLV respiratory vaccines are often considered more effective than inactivated vaccines.
Failure of human resources and management
Management failure is often the main reason for the perceived failure of bovine BRD vaccines. Vaccination of calves at an early age, when maternal antibodies are still present, may interfere with the vaccine’s ability to stimulate a protective immune response. It is also not recommended to vaccinate too late or too close to the risk of BRD. Although some vaccines claim to provide protection within days of administration, it often takes weeks to develop a full response. Vaccination in a truck or sales shed may be convenient, but it is not optimal for a protective immune response.
Vaccines must be stored at specific temperatures. If the vaccine is not stored within the recommended temperature range, its effectiveness may be compromised. Administering the vaccine incorrectly, such as using the wrong injection site or injection method, can reduce the effectiveness of the vaccine. To stimulate the immune response and ensure maximum efficacy, MLV must replicate in the animal. If MLVs are mishandled by improper storage, such as by getting too hot or freezing before administration, microorganisms may be killed and unable to reproduce after administration, resulting in a reduced or incomplete immune response. There is. The vaccine is available as a “no booster” one-dose product and a traditional two-dose product that requires an initial vaccination and a booster shot. Single-dose products are typically developed with producer convenience in mind rather than vaccine efficacy. Failure to administer booster shots properly can be a major cause of vaccine failure. Vaccine selection and product handling are important to optimize BRD protection.
Cow nutrition plays an important role in vaccine effectiveness. Proper nutrition ensures your immune system has the resources it needs to function optimally. Proper nutrition includes providing adequate levels of proteins, vitamins, and minerals that are essential for the production of antibodies and other immune responses. Lack of energy can lead to poor animal performance and poor physical condition, which can weaken the immune response to vaccines. Deficiencies in trace minerals such as zinc, selenium, and copper can impair immune function. These minerals are essential for various immune processes, including the production of white blood cells and antibodies. Immune cells and antibody synthesis require appropriate proteins. Protein deficiency can cause a weakened immune response and reduce the effectiveness of vaccines. Proper nutrition helps maintain overall health and reduces stress and the chance of co-infections that can interfere with the immune response to vaccines. Ensuring cows receive a balanced diet containing all the necessary nutrients can greatly increase the effectiveness of vaccination programs. Sick cows stop feeding and their normal trace mineral, energy and protein intake can rapidly decline due to reduced feed intake and increased immune system requirements.
Stress from weather factors, nutritional deficiencies, or pre-existing health problems can weaken the immune system and make it less responsive to vaccines. Stress causes the release of cortisol, a hormone that can suppress the immune system. This suppression can reduce the body’s ability to respond effectively to vaccines. Stress can lead to decreased production of antibodies and white blood cells, which are important for the immune response. This means that even if the vaccine is administered correctly, the immune system may not produce enough antibodies or white blood cells to provide sufficient protection. Stressed cows are more susceptible to infections and may have a compromised immune response to vaccines. If the animal is already fighting an infection, its immune system may not fully respond to the vaccine.
Stress can cause changes in behavior and affect how cattle are handled and respond to vaccinations. For example, stressed animals can be difficult to handle, which can lead to inappropriate administration of vaccines. Stress often reduces feed intake, which can result in nutritional deficiencies. Low-stress cattle handling is promoted to improve cattle welfare and minimize handling stress. In a low stress handling study conducted at Iowa State University, 18.8% of conventionally handled calves were treated for respiratory disease, compared to 7.4% of calves treated with low stress. It was proven that it was. Conventionally processed calves had lower hot carcass weights compared to low stress calves (728 lbs vs. 757 lbs, p = 0.0074). This study provides evidence that handling procedures to minimize stress in newly adopted calves are associated with improved health and performance in feedlot cattle.
conclusion
For bovine respiratory vaccines to be effective, effective cattle management, vaccine selection, timing, and nutrition are required. When combined with realistic expectations, BRD vaccination of cattle can be very beneficial and rewarding. Managing stress by responding appropriately and minimizing environmental stressors can help improve the effectiveness of vaccination programs. Working with a veterinarian who is knowledgeable about cattle diseases, management styles, and herd BRD risk factors is critical to a successful herd health program.
