by Sally Colby
Newborn calves begin life without a fully functional immune system – their only hope for immediate protection against disease is passive immunity acquired through maternal antibodies in colostrum.
However, even calves that receive maternal antibodies from their dams’ colostrum are subject to disease. Dr. Nathan Erickson, assistant professor, Department of Large Animal Clinical Sciences at Western College of Veterinary Medicine, explained that maternal antibodies in colostrum provide initial immunity for calves, usually for the first few months of life. Calves that don’t receive adequate antibodies from colostrum suffer from failure of passive transfer.
“Many aspects affect the ability of the calf to get adequate passive transfer,” said Erickson. “Quite often, heifers have poor quality colostrum. Adequate nutrition will result in a cow having better quality colostrum.” The immune status of the heifer or cow also plays a role in colostrum quality. Adult females vaccinated in a good program should have adequate immunity and produce sufficient antibodies in colostrum to pass to calves.
Colostrum and/or blood tests can determine whether a calf has received adequate antibodies for disease protection. However, it’s impractical to perform these tests on every calf born in a beef herd. It’s also impractical to administer modified live vaccines to young calves for disease protection because maternal antibodies are known to interfere with the calf’s ability to mount a good immune response. Erickson explained maternal antibody interference as a blocking of the response of the vaccine that’s administered to a calf that already has adequate maternal antibodies in its system. The process of vaccinating young calves with a systemic vaccine is an exercise in wasted time, money and potentially more stress on the young animal.
To override the potential interference of vaccines with maternal antibodies, there’s an alternative: intranasal or mucosal vaccination. Mucosal vaccination is a local vaccination that targets the surfaces of specific tissue – in this case, the mucosal tissue in the nostrils. “We are priming the immune tissue in the surface layers,” Erickson explained. “It’s a different part of the immune system and a different antibody response. In a systemic vaccination, we are stimulating IgG (immunoglobulin G) antibodies. A mucosal vaccination stimulates IgA (immunoglobulin A) antibodies.” The response from a mucosal vaccination is much faster and can occur as quickly as 40 hours. However, mucosal vaccinations have a shorter duration in the animal compared to an animal properly immunized with a systemic vaccine.
“Systemic vaccination depends on the response from the lymph nodes that create its own circulating antibodies,” said Erickson. “It takes a little bit of time for the response, maybe three to four weeks.” A systemic vaccination might have longer duration than a mucosal vaccine, but that depends on when the calf was initially vaccinated and whether it was properly boosted if a booster was required.
Erickson explained the main benefit of mucosal vaccination for respiratory diseases: they bypass maternal immunity. “We don’t have the same effect where we have a challenge or interference with maternal antibodies,” he said, explaining the differences between systemic and mucosal vaccines. “It bypasses the maternal antibodies because it acts at the site of infection and has less impact on IgG. We should get rapid onset of disease control.” While the duration of mucosal vaccines is shorter, there may be some priming of the immune system for future immunizations.
Calfhood mucosal vaccinations are most effective when the cow herd is well-vaccinated and can provide good passive transfer. Erickson said mucosal vaccination is a good measure prior to periods of high risk of exposure to disease, and when maternal antibodies are waning during the pre-turnout time, depending on when calves are born.
Erickson listed some common viruses and bacteria most likely to challenge calves, including bovine herpes virus type 1 (IBR), bovine parainfluenza virus type 3, bovine respiratory syncytial virus (BRSV), Mannheimia haemolytica, Pastuerella multocida, Histophilus somni, Bovine coronavirus (BoCV) and bovine viral diarrhea virus types 1 and 2 (BVD). Erickson added there’s debate about whether BVD is a direct cause of respiratory disease, but BVD causes severe immunosuppression, which allows secondary infections to strike. He urged producers to work with their veterinarian to determine which bacteria and viruses should be included in vaccines.
When administering mucosal vaccines, a cannula must be used for both single and multi-dose syringes. The cannula ensures delivery of the vaccine far enough into the upper respiratory tract to illicit a response. To limit the chance of spreading disease, replace the cannula every calf with neonatal calves. With weaned calves, replace it after every 10 calves.
The calf’s head position is critical for effective vaccination. The head should be elevated to ensure a sufficient amount of vaccine reaches and coats mucosal surfaces. Elevation is especially important in young calves. For weaned calves, make sure the head is secured safely in the head gate and not aimed downward. If calves are vaccinated in the first 24 hours of life, they should be well-dried prior to vaccination.
Mucosal vaccines contain ample material for effective immunization, so if the calf sneezes immediately after the vaccine is administered, there’s still plenty of vaccine to reach mucosal tissue. Erickson said a more important concern is maintaining the calf’s head in a level or slightly elevated position that ensures the vaccine won’t drip out.
Erickson reminded producers that mucosal vaccines are live vaccines that are mixed with a diluent prior to administration. Vaccines should be mixed gently – rapid agitation can affect viability. Once the vaccine is mixed, it should be used within an hour of preparation and not exposed to extreme heat, cold or light. “The immune response depends on replication of the virus or bacteria,” said Erickson. “Making sure they survive until the vaccination process is important.” Erickson added that a cooler is an effective means of keeping vaccines at optimum quality as calves are being worked.
Ideally, calves should receive a mucosal vaccine without any other procedures such as dehorning, tagging or other routine tasks. However, this is impractical, so quiet, careful handling ensures calves’ best chance at a good immune response.
Erickson said vaccine programs should be tailored to meet specific herd management and disease concerns. “Some herds have respiratory disease outbreaks at certain times of the year, so try to boost immunity just prior to when that occurs,” he said. “Blanket generic protocols aren’t always optimal for every herd, so it’s best to work with your veterinarian to develop the best plan, especially now that we have so many options.”