Immunity associated with bovine respiratory viruses after intranasal vaccination

by Katie Navarra

Respiratory disease is a significant issue cattle producers must deal with on a daily basis. It’s been estimated it has cost the industry nearly $900 million with death and production losses, with the result of survival of a BRD, according to Christopher Schneider, technical services with Merck Animal Health.

“It’s been mentioned that it is the number one disease of concern at the beef industry, probably the number two economic disease, and it continues to be a challenge as we try to raise animals in larger and larger production systems,” he explained during a recent webinar hosted by the Dairy Calf and Heifer Association.

In general, respiratory vaccines do not prevent disease, but rather lessen the severity and significance of clinical signs or effects. Vaccines come in multiple forms, with intranasal vaccines considered one of the most effective. Administering intranasal vaccines quickly establishes immunity for future respiratory protection.

“The nasal route of administration actually spurs a different immune response in cattle” than injectable vaccines, Schneider said. “This makes intranasal vaccines a key tool for producers battling respiratory illness in cattle, which has remained one of the top challenges to cattle health for decades.”

The complex mucosal immune system

The mucosal immune system is made up of a diverse series of systems working together, including the eyes and the nasal and oral systems. Even the tissues that line the gastrointestinal tract are involved with establishing immunity. Factors from the external environment, both good and bad, trigger immune responses.

“If we can expose it to certain types of antigens at the right period of time, we can enlist it in a protective response or at least an immune response that’s beneficial to the animal and helps them work different,” he said.

Intranasal vaccines provide a rapid immune response in advance of predictable disease challenges, especially in younger cattle – for example, spring processing and branding in beef cattle or weaning and early pen moves in dairy cattle.

“Intranasal vaccines provide local immunity, IgA and measurable interferons, at the site of pathogen entry, i.e. nasal mucosa and oral pharynx,” Schneider explained. “These vaccines offer rapid onset of immune protection at the site of entry of the pathogens associated with bovine respiratory disease.”

Vaccination timing

Planning vaccinations to coincide with known disease challenges means administration timetables vary between beef and dairy. Two products on the market include label claims that intranasal vaccines can be given to calves less than a week old.

“This is typically in an attempt to protect hutch calves from early pneumonia events that we see at 30 to 45 days of age,” Schneider explained. “In beef, it would be more typical to see them given at the first processing time, ‘branding,’ which is at about 60 days.”

Revaccination is necessary and based upon duration of immunity (DOI). Administering boosters is recommended ahead of disease stressors such as comingling, weaning and others that may arise after the initial date of inoculation has elapsed.

Change can feel overwhelming, and with many farms traditionally using injectable vaccines, making the switch to intranasal vaccines can feel daunting. Schneider said farmers sometimes shy away from intranasal vaccines because they think they are difficult to administer. Even though the intranasal method is different, Schneider has found that people and animals quickly become accustomed to the delivery and often find it easier and less stressful.

In addition to delivery method, the biggest difference between injectable and intranasal vaccines is the affect on an interferon response in an individual animal.

“These vaccines typically illicit a vibrant local interferon response,” he said. “The effect of this response specifically related to disease state [pneumonia] is less well understood.”

Immunologists are still investigating the practical significance of many of the immune-related responses that can be measured in studies.

“The gold standard here is challenge studies. When properly vaccinated, do we see reduced disease outcomes (sickness, virus shedding, etc.) in animals challenged with the agent in the vaccine?” he asked.

Trying intranasal vaccines

Intranasal vaccines are like any of the other modified live vaccine and need to be maintained in cold storage until given. On vaccination days that are 90 – 95º, keeping the product in a cooler with an ice pack after it is mixed is important. Any left over product should be thrown away.

“I would not store these products, or any modified live vaccine, in the fridge and try to get to it tomorrow or the next day,” Schneider said. “The efficacy is based on being used relatively soon after reconstitution.”

Jerseys are generally recognized as more sensitive to the effects if endotoxin, gram negative bacteria cell wall and some injectable vaccine adjuvants (the part of the vaccine that helps stimulate a vigorous immune response). This is particularly an issue with calves, according to Schneider. Therefore, using intranasal (IN) technology helps veterinarians and producers vaccinate these animals with a smaller antigen mass at the site of infection.

“IN vaccines typically have a less stimulatory adjuvant and are generally thought to be less physiologically ‘stressful’ on the animals compared to injectables,” he said. “I am not aware of specific studies that have looked at this, and it is basically an anecdotal feeling within the industry.”

Immunization strategies using the mucosal immune system are excellent and likely superior ways to enhance immunity in cattle for respiratory disease, according to Schneider.

“Intranasal vaccines are effective in their ability to stimulate a measurable immune response that protects young animals in challenge studies,” he said. “There is compelling scientific support showing its effectiveness in combating bovine respiratory disease in young dairy calves.”

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