Help vaccines do their job in the summer heat

Preventing disease caused by bacterial pathogens associated with Bovine Respiratory Disease (BRD) should be on every herd health calendar for cattle of all types and sizes. BRD complex associated with Mannheimia (Pasteurella) haemolytica for example is known for its severity and rapid onset in cattle, particularly after they experience stress.

Vaccines are a great tool to help combat any number of cattle diseases, including BRD. However, to get the most protection vaccines can offer, producers need to keep a few things in mind — especially as temperatures heat up.

Dr. John M. Davidson, professional services veterinarian with Novartis Animal Health, advises producers to be mindful of weather conditions when working and vaccinating cattle in the heat of summer.

“Heat stress can trigger a variety of health issues for cattle,” notes Davidson. “One of the challenges of heat stress is that it limits an animal’s ability to build an immune response. So administering vaccines in high heat or excessively humid conditions should be avoided whenever possible. It’s always better to work and vaccinate cattle early in the day when ambient temperatures are cooler.” 

Davidson also reminds producers to monitor the number of gram-negative vaccines they are administering to cattle at the same time. “This is especially important during hot weather,” he says. “There are a quite a few gram-negative bacterial diseases we protect against with vaccines, including M. haemolytica, formerly known as Pasteurella haemolytica.”

The challenge is that the majority of vaccines licensed for protection against respiratory disease bacteria contain whole cells of the target bacteria, like M. haemolytica for instance. The cell walls of these bacteria contain lipopolysaccharide, or LPS, also known as endotoxin. And the LPS endotoxin has a negative impact on an animal’s overall system—specifically its immune system.

“The effect of LPS is cumulative,” explains Davidson. “That’s why there are recommended limits on the number of gram-negative bacterial vaccines administered to cattle. This is especially important for calves and lightweight cattle. Producers should always consult with their veterinarian for guidelines on calfhood vaccinations against respiratory disease because every operation has a unique set of circumstances or risk factors. 

Temperature Effects

Heat stress can lower an animal’s natural barriers to bacteria¹, increasing the potential for LPS levels to rise and adding to the cumulative effect.

“That’s why it’s even more important not to overload cattle with gram-negative vaccines in the heat of summer,” cautions Davidson. “Unfortunately, we are not able to predict which animals are more sensitive to the effects of heat stress and LPS endotoxin. However, we do know that certain weather conditions and vaccines containing whole cells of target bacteria can increase the likelihood of an unfavorable response.”

Fortunately, newer vaccine manufacturing processes enable us to minimize the inclusion of the endotoxin or LPS-containing portions of the bacterial cell wall. A good example is NUPLURA® PH, the newest M. haemolytica vaccine to enter the U.S. marketplace. NUPLURA PH is not a traditional “whole-cell” vaccine. It’s unique in that its principle components are outer protein membranes (OMPs) that have been extracted and purified.

These OMPs are joined by a recombinant leukotoxoid and an adjuvant. This production process reduces the amount of the whole-cell wall present in the vaccine and, therefore, lowers the potential for a reaction to LPS endotoxin.

“To get the maximum response from vaccines, it’s important that we don’t overwhelm the animal’s immune system,” Davidson says. “In the summertime, this means avoiding working cattle if the temperature is above 85 degrees F with humidity above 40%, or at higher temperatures with lower humidity.”²

Management Considerations

To maximize the effectiveness of your vaccination program:

• Always consult with your veterinarian regarding vaccination protocols as part of your herd’s total health program.
• Properly store products.
• Vaccinate healthy animals.
• Administer vaccines using good hygiene and according to label directions.
• Understand there’s a higher potential for adverse reactions in hot weather and high humidity. Keep proper treatments on hand, like epinephrine, to quickly address any adverse animal reaction.
• Use these heat stress guidelines and the accompanying temperature-humidity index chart from the Kansas Department of Agriculture to reduce the effects of heat stress.

Keep in mind that making good vaccine choices is only one part of preventing costly diseases in cattle. Good nutrition is the cornerstone of animal health management and along, with mineral supplementation, is essential for vaccine efficacy.

¹Lambert GP. Stress-induced gastrointestinal barrier dysfunction and its inflammatory effects. J of Animal Sci. 2009; 87:E101-E108.

²Bagley C. Vaccination Program for Beef Calves. Accessed June 11, 2012.

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