Milk cows and chickens made disease control a reality in the beef industry. In fact, the two critters helped make vaccines available to both man and beast. Though a bit oversimplified, 18th-century milk cows and their milkmaids were the forerunners of vaccines. In the late 1700s, an English country physician, Edward Jenner, noticed milkmaids exposed to cowpox didn't contract smallpox. It gave him the idea to inoculate a child with cowpox. Afterwards, Jenner challenged the child several times with the smallpox virus - he never fell ill. The early era of vaccines was born.
The science of vaccination is actually credited to Louis Pasteur. In the late 1800s, he was researching fowl cholera and after a lab shutdown, Pasteur inoculated some chickens with leftover Pasteurella. They didn't die. In fact, Pasteur found that they were protected from subsequent infection with fresh virulent Pasteurella. He repeated this with rabies, anthrax and other organisms.
We've Come A Long Way We've come a long way in little more than 100 years. Today, vaccines are targeted, accurate disease preventers when used properly.
Louis Perino, veterinarian and professor at West Texas A&M University, Canyon, TX, says the relative youth of immunology provides room for growth and improvement.
"We started by isolating bacteria from dead animals, putting it in others and if they died of the same disease, you knew you were on track," Perino says. "That falls apart in modern times with multifactoral diseases such as bovine respiratory disease (BRD) and scours.
"Multifactoral diseases must have several factors in addition to the organic causes, such as stress and dehydration, to occur. Merely inoculating the animal with an organism may not cause the disease," he says.
Fortunately, the ways disease-causing bugs are isolated and studied are more sophisticated now, Perino says. Researchers grow them, study them, analyze their DNA and determine which pieces of the bug are important to disease causation and prevention. This ability to isolate bits and pieces results in purer, more specific vaccines.
Biotechnology has improved vaccines in two areas, Perino says.
"First is pathogenesis, or the origin of disease. Biotechnology helps us better understand how a pathogen causes disease in its host," he says. "Secondly, biotechnology helps improve the manufacturing of vaccines by improving our ability to manipulate the bugs. If we know and understand which part of the bug an animal uses to protect itself, we can remove that piece, grow it and deliver it to the animal effectively."
Methods of inactivating pathogens have improved as well. Originally, pathogens were killed chemically or by heat inactivation, which affected vaccine efficacy.
"We're gentler today with how we kill the bugs and have the pieces we need survive. Plus, we've learned how to attenuate the bugs, or render them unable to cause disease," Perino says. "Once we know the DNA code, we target the mutation and perhaps even delete the gene that causes a disease.
"Adjuvants are better, too," Perino adds. "Our ability to enhance the immune response with adjuvants is key to making better vaccines. All killed vaccines contain adjuvants and they appear to be able to enhance some aspects of an immune response in live vaccines."
Perino adds that pathogenesis studies have increased understanding of how organisms create disease. This has allowed vaccine manufacturers to target, isolate and introduce fewer antigens to the animal. For example, understanding how Pasteurella causes pneumonia has resulted in vaccines containing the key fractions needed to build immunity. The latest generation of clostridials has fewer antigens as well.
Where We're Headed "The vaccines today are better, but those of 15 years ago were worthwhile, too," Perino says. "We continue doing the same things, but at a higher level because science and technology have advanced. We keep improving vaccine features we know are important.
"I'm excited about recent improvements that allow us to produce higher quality products and still provide disease prevention. Cytotoxin-based Pasteurella vaccines are a good example of how a vaccine targets the same tools the bug uses to cause disease."
Vaccines directly impact the larger picture, too. Perino says that a vaccine that prevents disease is one less instance of antibiotics that must be used.