Photo by Shaman Shay on UnsplashMonkeys have been used in scientific research for decades, often bred in captivity for the production and testing of vaccines. Bred in captivity, these monkeys had fewer viral infections than captured primates and provided clean cell cultures that could be grown.
Rhesus macaque monkeys can also produce neutralizing antibodies against a strain of HIV called the Tier 2 virus, and though the vaccine has not begun clinical trials yet, scientists are hopeful for its success. Researchers at Beijing-based SICOVAL Biotech gave doses of the vaccine to eight macaques and three weeks later introduced the SARS-CoV-2 into their lungs, and none broke out in full-blown infection.
The results in mice have shown vaccines could be promising for women carrying the BRCA1 and Bra 2 gene mutations, who are at a higher risk of developing breast or ovarian cancer. Photo by vaun0815 on UnsplashLike mice, rats are often used to test medical breakthroughs and have been the subjects for cancer treatments for years.
They have been used in studies on mucosal immunization against antigens and pathogens that enter through mucous membranes that line the mouth, nose, eyelids, trachea (windpipe), lungs, stomach, intestines, ureters, urethra, and bladder. Pigs have been deemed one of the most appropriate and reliable models for testing vaccines because their physiology and immune systems are very similar to humans.
Pigs also have tonsils and their skin's dermis-to-epidermis ratio is similar to humans, making them a viable medical test subject. In addition, their large litter sizes make them attractive for researchers, though they become more difficult to handle as they grow and require more substantial penning.
Early bacteriologists mimicked the human body environment by creating solutions of sugars, salts, and meat extracts, which would help grow bacteria and viruses in the lab. Though many discoveries since have leaned toward synthetic vaccines, some still require nutrients that are provided most easily from animal products like serum, blood, amino acids, and sugars.
Viral vaccines require living cells for production, and their growth is often aided by fetal calf serum. This has caused some concern from the food and drug administration over the years, as some bovine-derived products could potentially carry bovine spongiform encephalopathy (BSE, also known as mad cow disease).
Perhaps you’re already in the rhythm of planning immunizations for your horses and have scheduled a spring veterinary visit. Here, our sources will answer some common vaccination queries we’ve received from our readers.
ACVIM-LAIM, professor and head of Equine Internal Medicine and Surgery at Kansas State University, in Manhattan. “With aging or disease, there is a natural reduction in responses induced by the immune system.” Older horses or those with disease (such as pituitary pars intermedia dysfunction, or equine Cushing’s) might need to be vaccinated in a slightly different manner than younger or more healthy horses.
“Stress, such as experienced during long-distance transport and/or strenuous exercise, directly reduces the level of immune response that a host (the horse) can provide.” Always immunize well in advance of any anticipated stress (this also includes foaling, weaning, etc.) Every horse, regardless of location, age, or sex, should be vaccinated against Eastern and Western encephalomyelitis, West Nile virus, tetanus, and rabies.
“Immunologic memory is the (body’s) immune response against an infectious pathogen that reacts more quickly after the immune system has been primed with an initial series of vaccines,” says Julia Felipe, DVD, MS, PhD, Dial. Achim, associate professor at Cornell University’s College of Veterinary Medicine, in Ithaca, New York, who has a special interest in equine immunology.
For pathogens that pose a high risk for infection, such as those abundantly found in the environment or transmitted by mosquitoes or by direct or close contact between horses, veterinarians recommend periodic vaccination. Take tetanus for example: Horses live in an environment rich with equine fecal matter that contains the causative bacterium Clostridium retain.
This potential for exposure (e.g., through a wound) means horses should receive annual boosters against tetanus, says Davis. Horses might also require more frequent boosters against respiratory and mosquito-borne viruses, depending on their risk of pathogen exposure.
Similarly, veterinarians administer mosquito-borne virus vaccines in advance of mosquito season to confer the highest level of immunity, and in warmer climates horses might need boosters twice a year. “A great deal of work has established guidelines for each vaccine,” Davis stresses.
“Deviation from recommended protocols could put horses at greater risk to develop disease.” “Nevertheless, some killed vaccines (e.g., those against EEE, WEE, tetanus) induce robust production of neutralizing antibodies that are effective in controlling these specific infections.
Davis says the advantages of intramural vaccines are twofold: The protection is both local (mucosal) and rapid. Upon exposure, the horses develop variable severity and duration of disease; the virus spreads among the group until all have developed disease and recovered or had previous exposure that provides protective immunity.
Compare this scenario to a group of 30 horses whose owners or managers have applied excellent EIC vaccine protocols. If a single horse out of 30 is not vaccinated or has low-level immunity against the virus, yet the majority of horses are protected from infection, then the virus does not become embedded in the group and, therefore, has limited ability to cause disease in a single at-risk individual.
If a horse has received an initial priming vaccine series and is late or misses one annual booster, he is likely to respond appropriately to a booster vaccination with an effective anapestic immune response, says Davis. “If a horse must receive the full primary immunization series, then five weeks may be needed in order to include a booster,” adds Felipe.
Ideally, horse owners should consult their veterinarians about vaccine protocols and practices. Another consideration is the possibility of a serious adverse event such as a severe allergic reaction (anaphylaxis) or a life-threatening infection with anaerobic bacteria (Clostridia) at the injection site.
“Although such complications are uncommon, they do occur occasionally and are handled best by a veterinarian who has extensive experience with vaccine preparation and administration,” Davis says, adding that in many states and by law, a veterinarian must administer rabies vaccinations. The haunches are probably not the best choice, because if an abscess forms, which rarely occurs, that area is difficult to drain.
Many inject the neck because of its easy access and safety for the person administering the vaccine. Most vaccine reactions are mild and transient, occurring within 24 to 48 hours following immunization and resolving within two to three days.
Reactions involve any of the following: local soreness or swelling at the injection site, a stiff gait, mild fever, lethargy, and/or reduced appetite. Giving a horse a non-steroidal anti-inflammatory drug (NSAID) might hasten resolution, but talk to your veterinarian before administering anything.
If a horse has a known vaccine sensitivity, giving an NSAID at the time of immunization can help forestall an adverse reaction. You and your veterinarian have an established professional relationship that allows you to make informed decisions for your horses.
Equine veterinarians are knowledgeable about protecting against communicable diseases relative to your geographic area, and they are also familiar with your individual horse’s current and unique state of health and risk of exposure. Achim, interim director of Kansas State University’s Veterinary Health Center.
Eastern and Western equine encephalomyelitis (EEE and WEE) are named for their geographic distribution. Rabies, once signs appear, is 100% fatal in all mammals (including horses, humans, dogs, cat, skunks, foxes, and raccoons).
Tetanus is caused by the bacteria Clostridium retain, which are abundant in horses gastrointestinal (GI) tracts and feces, said Davis. “Things like penetrating (puncture) wounds, subsolar (inner hoof) abscesses, and even invasive medical procedures can put an unvaccinated horse at risk.” The disease is neurologic, causing extremely painful muscle spasms, and usually fatal.