For preventing infectious diseases cattle vaccination is a very important activity. But farmers, Vaccinators (para-vets) as well as Veterinarians should be aware of dos and don’ts while carrying out a vaccination campaign.
What are vaccines and their response?
Vaccines are nothing but bacteria/virus or their components and in some cases, even toxins produced by the bacteria are also used to immunize animals. Protein parts of the bacteria are able to cause stimulation of the animal body to produce antibodies hence these components are also called commonly antigens and the chemical these produce when injected in the body are termed ‘antibodies. These antibodies, in fact, fight future infection hence even if the animal is exposed to the same bacteria/virus or antigen it does not suffer from the disease.
Age of First Vaccination
As far as ruminant young ones are concerned these become immune-competent (that means will react to and produce antibodies when exposed to an antigen) at embryonal age of around 150 days. Researchers have proved this by injecting antigens when embryo in the uterus was around that age and could observer antibody response. But, normally in cows, since maternal and fetal membranes have three layers of separation, hence fetus is totally insulated from maternal circulation and no antigen can pass through.
In the case of humans and other animals however, smaller proteins/antigens can pass through placenta hence at the time of birth a child has antibodies circulating in the blood. In contrast in calves, at birth, there are no antibodies in the blood. Colostrum, that is the first three day’s milk after calving is rich in antibodies. When antibodies-rich colostrum is fed to calves within 6-12 hours of birth antibodies pass thorough intestine intact into circulation and provide protection to calves against diseases at least for few more weeks till the time calves are exposed to antigens and are able to produce active antibodies.
The age of first vaccination primarily depends on whether colostrum was fed at the right time and whether colostrum contained enough antibodies. In principle, if the calf had received a good amount and quality of colostrum there will be circulating antibodies that might interfere with vaccination response. For this reason, in colostrum-fed calves, vaccination should be delayed whereas in others vaccinating could be done. As a general rule, in colostrum-fed calves, the first vaccination should be done when a calf is more than six months old whereas in others it could be done earlier, for example, three months. When national vaccination programs are implemented monitoring of antibodies in colostrum of vaccinated cows and un-vaccinated cows as well as antibody titer in post-colostrum fed calf blood are important parameters to decide vaccination frequency in the population.
Should vaccination be done when an animal is suspected to be sick with the same or other diseases?
No, never do that, as it may increase the severity of the disease. If there is already an outbreak of the disease on the farm, the decision of vaccinating other animals on the farm should be taken in consultation with a qualified veterinarian. A practical approach is to separate animals that are showing even early signs of the disease and those without signs but showing fever (if fever is one of the symptoms) should be separated and treated but not vaccinated. Whereas, healthy animals can be vaccinated and separated from diseased animals. Even vaccinated animals should be kept under observation because these might be in the early incubation period and might show symptoms at a later stage.
What about vaccinating animals when there is an outbreak in an area?
Some diseases spread rapidly hence when there is an outbreak of such a disease larger adjoining population should be vaccinated. The factor to consider here is how this disease is transmitted, by animal-to-animal contact, animal-to-human contact, by air, by water and the normal animal movement pattern in the area. Such decisions are usually taken by public policy veterinarians. Farmers are expected to and must comply with such instructions since these are in the interest of the farmers and their animals.
Can vaccination be given to pregnant animals?
This is a commonly asked question. The answer is yes unless the animal is insufficiently advanced pregnancy and in the process of calving. I have vaccinated cows up to 9 months in pregnancy without any problem (unless there is a specific direction not to vaccinated in pregnant animals, especially bacteria/viruses known to cause abortion). I prefer vaccinating pregnant animals twice during pregnancy to ensure that colostrum is rich in antibodies. This can be practiced for more-prevalent diseases, such as colibacillosis in calves. When repeated vaccinations with the same antigen are done the process is called hyper-immunization. This procedure is followed when colostrum and later on milk is required to be rich in particular antibodies (such as Helicobacter pylori, Salmonella typhi, etc.). Colostrum and milk from such hyperimmunized cows are called Health colostrum or Health milk and indicated as a supplement in specific diseases.
Can vaccination and administration of antibodies and antibiotic be done at the same time?
While vaccinating the administration of antibiotics will not produce any harm but antibodies (hyperimmune sera) should never be given at the same time as the antigens will neutralize the antibodies.
Can multiple vaccinations be done at the same time?
In fact, this should be avoided because the antibody response will also be divided and hence against each antigen response will poorer as compared to when single antigen vaccination is done.