Vaccines given to neonatal calves are an effective means of providing protective immunity and a critical element of creating a supportive foundation for future respiratory health. Intranasal choices arrived decades ago with limited implementation but recently have returned, this time pushing to the forefront.
Categories and delivery
Today, these vaccines all contain modified-live options, says University of Saskatchewan professor Philip Griebel. Most are viral-based, but some bacterial and viral combination versions are also available. These modified-live vaccines protect against IBR, PI3 and BRSV, the major respiratory diseases in young cattle.
“BVD, the other major respiratory challenge, isn’t represented in the intranasal vaccines, as this virus tends to cause more problems as a system infection affecting the blood, bone marrow and other sites within the body,” Griebel says. Injectable bovine viral diarrhea (BVD) vaccines are normally used in cows passing on high levels of maternal antibodies to protect offspring against BVD during the first five to six months of life.
“Maternal antibodies to IBR, PI3 and BRSV usually transfer at lower levels. Since they don’t last as long, it’s important to vaccinate young calves because of waning maternal antibodies much earlier in life.”
Delivering intranasal products, especially in older cattle, has been problematic as controlling the head is difficult. Their use in young calves is more straightforward.
“Elevate the head so it’s horizontal and level,” he said. “Newer products feature a colored dye in the diluent indicating whether vaccine or nasal secretions are leaking out.”
Reasons for return
Amelia Woolums, professor in the department of pathobiology and population medicine at Mississippi State University, outlines two main reasons intranasal vaccines have returned to prominence.
First, she described studies, including some European research, which compared intranasal and injectables, focusing on BVD. They found intranasal vaccines could induce stronger immunity since very young calves have higher levels of maternal antibodies from colostrum. These antibodies have the potential to bind to vaccines and keep them from functioning to their potential.
Secondly, Woolums says immunity is made up of both systemic and mucosal actions.
“Surfaces covered with mucous – the respiratory, gastrointestinal and urogenital tracts – have some immune components that defend them in a different way than the systemic which supports the body tissues and blood. Evidence exists showing when we vaccinate on a mucosal surface, we may get a superior future response.”
She explains when the weakened organisms of modified-live intranasal vaccines are given in the nostrils, they begin to replicate, causing the immune system to recognize them, similar to a mild infection. The epithelial and sentinel cells on the mucosal surface collaborate to spur it to action.
Maternal antibody interference
Griebel outlines the main issue with using an injectable soon after birth is: The MLV injectables contain weakened live viruses which infect cells to replicate and amplify the immune response.
“If we inject an MLV into a young calf and maternal antibodies are circulating in the blood, it will bind to the vaccine virus and block it from infecting cells and initiating this response.”
Most maternal antibodies from colostrum are present in the blood, protecting a calf from infection should a virus or bacteria get inside the body. Other types of antibodies secreted in the nose, tears and intestines are not prominent in colostrum but specifically designed to be present at surfaces exposed to the environment. Intranasal vaccines avoid the issue of maternal antibodies as they enter the mucosal surface of the nose, infecting the cells there, replicating properly without interference.
Timing and progression
Woolums believes timing is important when considering initial and booster treatments.
“There’s some research showing longer is better, giving a second dose after two or three months in comparison to only one month. For roughly two weeks, the immune system is busy responding to an initial delivery. We want to give it time to respond to the first dose before giving a second. Around two to three months is good.”
Griebel agrees and adds purebred producers regularly handling calves at birth might vaccinate within the first week. Commercial operations may choose turnout or branding, when calves reach 4 to 8 weeks old. Research has shown using intranasal at these times will provide reasonable immune response lasting until weaning – but not strong enough to prevent serious respiratory diseases.
He suggests providing more immunity at the virus infection site with an intranasal at turnout may also give more protection against summer-type pneumonias.
Due to the problems of safely handling larger heads, an intranasal given shortly after birth or at branding when calves are still of manageable size, followed by an injectable at 5 to 6 months old, may be the beneficial choice. If a head bar is available, an intranasal booster provides a rapid onset of protection within three to five days.
“That’s an ideal combination,” Griebel says. “An intranasal at branding then, if we’re not preconditioning, using an intranasal booster before or at weaning. If calves are infected with a high viral dose three or four days later, they would have solid protection.”
A 2015 trial by the University of Georgia compared subcutaneous MLV boosters with intranasal boosters 60 days after an initial intranasal vaccination at 1 to 3 weeks old. Results suggested the intranasal booster may be a more effective route to enhance immunity against BRSV in young calves previously primed with an intranasal MLV.
Woolums points to research showing an initial intranasal primary followed by an injectable booster gives broader immunity than either two doses of injectable or intranasal, although she warns none of these products and combinations provide extremely long-lasting protection.
In the future, she would like to see more research aimed at increasing length of defense against respiratory pathogens. Driven by the COVID-19 pandemic strategies, she envisions more companies testing RNA vaccines although, due to their expense, they may initially target the companion animal industry rather than cattle.
