Vet's Corner with Dr. Dan Rice
How a vaccine works
By Dan Rice, D.V.M.
Antibodies are specialized protein molecules that are produced by lymphoid cells, which are part of a dog’s immune system. Antibodies destroy or neutralize specific antigens, which may be disease-causing particles such as viruses or bacteria, often called pathogens. Pathogens have varying antigenicity (disease-causing capacity), which refers to their virulence or infectiousness.
Vaccines are prepared by several methods. A virus may be modified or attenuated by some method to reduce its potency, or virulence, resulting in a MLV (modified live virus) vaccine. Or, a living virus may be killed by chemicals or heat to produce a vaccine that has even lower antigenicity than an attenuated one. Either type has a place in immunizing a dog, but any vaccination must be administered before the puppy is exposed to the pathogen.
Bacterial pathogens are treated to make them incapable of causing disease, and technically are called bacterins, but are usually called “bacterial vaccines.”
Passive immunity: A dam’s antibody level is influenced by many factors such as her past vaccinations, nutritional state, disease exposure, and general health. Some of those antibodies pass through the pregnant dam’s placenta to each fetus and each pup also receives additional antibodies in the dam’s colostrum (first milk). Those maternal antibodies protect a puppy for a limited time but they eventually disappear. That temporary protection is called passive immunity, which is why competent dog breeders always breed a bitch with excellent conformation, and also possesses superior health, being fed a premium diet, and that has received recent vaccination(s).
A puppy’s immune system is not functional at birth and any neonatal (newborn) pup has only a very slight ability to produce its own antibodies. Passive immunity antibodies soon begin to disappear from a puppy’s bloodstream and when they fall below a protective level, the puppy’s health is at risk.
Vaccinating a pup while its maternal antibodies are present will result in some vaccine particles being neutralized by those antibodies. Thus a narrow vaccination window exists after a puppy’s maternal antibody levels are nearly depleted but before it is exposed to living pathogens.
Veterinarians have researched and studied that phenomenon extensively to try to determine the best time to vaccinate a puppy but, the exact best time to vaccinate all puppies is unpredictable because each dam-and-pup pair is unique unto itself. According to veterinary immunologists, most, if not all, of the passive immunity is gone from a puppy’s bloodstream by eight weeks of age. The dose of a vaccine is the same, regardless of the size and breed of dog.
Active immunity occurs when a dogs’ immune system is triggered by any means to produce antibodies. A vaccination or an exposure to a live, virulent pathogen, will trigger the system to produce antibodies. If the invading virus is a vaccine, the puppy produces antibodies, builds immunity to the pathogen, and is protected from the disease. However if the invading virus is a virulent pathogen, the pup may succumb to the disease, but if the puppy survives the disease, a long-term immunity will result. Each additional vaccine will stimulate more antibody production and higher immunity, which is the reason for booster shots.
A veterinarian may administer a multivalent (combination) vaccine that contains more than one virus species, and protects against several diseases. Or the clinician may give a series of monovalent (single) vaccines administered a week or ten days apart. A monovalent product allows your veterinarian to determine its effectiveness and whether or not it causes a reaction. The downside of that technique is that a pup will need to see your veterinarian more frequently, and several monovalent vaccines will undoubtedly cost more than a single dose of a combination vaccine. Blood tests to check antibody level (titer) are usually included in that vaccination scheme. In either event, booster vaccinations are scheduled to assure that the dog continues to produce a protective level of active immunity.
Arbitrary vaccination schedules are generally obsolete. A puppy should most certainly be vaccinated, but its age, number and frequency at which vaccines are given should be structured to fit its individual needs. Vaccinations also should be considered according to the region of the world in which the dog resides and diseases that are endemic (prevalent) in that region. In other words, disease exposure potential varies according to the area in which you reside or to which you travel.
What causes a dog's nail's to be brittle? My dog has had a nail split three times in the last month. Could this be a problem with diet? --Thanks Rebecca
Dr. Dan's Response
If the same nail has split several times, it may be caused by an injury to the “quick” or upper, vascular-and- nerve-containing portion of the nail. Have you ever hit your fingernail with a hammer? It is possible that the dog has suffered a trauma to the nail in some way. Have you seen your cat carrying a hammer?
You might try trimming the nail as short as possible on a weekly basis to see if the injury will eventually grow out. That may take several months. An injury of any kind might be corrected by a veterinarian, depending on what caused the injury, how extensive it is, etc. If the injury is extensive or is causing repeated and painful problems, it is possible that the veterinarian will advise surgical removal of the nail.
Diet might be involved if several different nails are involved. In which case, I would advise you to consider your dog’s diet. If it is fed dry, inexpensive food, the diet may be deficient in fatty acids and fat-soluble vitamins. Other signs of that deficiency are dry skin, dry coat, excessive shedding, etc.
In which case I would advise spending a bit more and feeding a premium dry food. Adding a fatty acid-vitamin supplement will be more expensive than changing diet and usually is not necessary. Of course, you can try adding a bit of vegetable oil to the dog’s diet daily. The dose will depend on the weight of the dog.