Llama Health Issues

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Feeding Ruminant Protein to Ruminants is Banned
Guidelines for Llama Vaccinations

Ig’s and the Immune System, 

A Short Primer by Stephen Mulholland

In most discussions of animal immunity and vaccinations, you will come across references to "Ig". This is an abbreviation for "immunoglobulin." An immunoglobulin, or Ig, is a protein molecule that is produced by the immune system to help recognize invading organisms (bacterial, viral, fungal, and parasitic worms) and mark them for elimination by other cells of the immune system. Ig’s are more commonly known as “antibodies.”  Measuring the Ig level, or quantity of antibodies, in the blood therefore provides a good indication of the health and capabilities of the immune system.

When a baby mammal is born, it has no antibodies at all, and is therefore very vulnerable to infection. The mother's colostrum contains a large number of antibodies produced by the mother to be passed on to the young. These antibodies provide protection in the weeks and months after birth while the baby's own immune system is developing. The stronger the mother's immune system, the better the protection that the baby receives via the colostrum: this is why it is recommended to give the mother a vaccine booster shot a few weeks before birth, as it boosts her antibody levels against common paddock diseases, and this improved protection is passed on to the cria. If the baby does not get any colostrum, it is very vulnerable to infection and is much more likely to die. A plasma infusion can save such an at-risk cria by providing it with the antibodies of an adult animal.

Vaccination presents the immune system with a sample of what some of the common and deadly infectious organisms look like. Vaccinating an animal in the first few days after its birth is pointless as there are not enough immune cells in the blood stream to effectively respond – it has its mother's antibodies, but no means yet of producing its own.  To give a cria's own immune system enough time to develop, its first vaccination should be given six weeks after birth, with a second dose four to six weeks later. The repetition induces the immune system to create “memory cells,” which are antibody (Ig) producing cells that circulate in the blood and watch for more invaders. The memory cells can last for months or years. By giving periodic booster vaccinations, we refresh the population of memory cells, keeping the immune
system primed to fight off those invaders.

The primary components of the immune system are the leukocytes, or “white blood cells”, manufactured in the bone marrow and released into the blood stream. Leukocytes come in many different varieties, but they are all designed to work together to identify foreign invaders and destroy them. The combined mass of cells of the immune system is about the same as the liver, making the leukocytes, as a group, one of the largest “organs” in the body.

A subtype of the leukocyte is the lymphocyte.  Broadly speaking, there are two different classes of lymphocytes, the T-lymphocytes (T-cells) and B-lymphocytes (B-cells).  The T-cells are involved in what are known as “cell mediated responses”: these respond to cells which have foreign bodies displayed on their surface and can eliminate virus-infected and cancerous cells. T-cells can also respond to chemical signals to activate and search for invading bacteria. The B-cells are involved in the production, presentation, and retention of antibodies.

Immunoglobulins  are the primary tools of the B-cells. Specialized B-cells wander the body looking for cells or particles that are foreign. Finding an invader is only the first step. The rest of the immune system must be notified and mobilized. Almost any large molecule (protein, carbohydrate, fat) can induce an immune response. These molecules are known as antigens, which stands for “antibody generators”, and a single bacterium or virus may be covered by thousands of them. The antigens are chopped up into small pieces, and those pieces are then presented to the antibody-producing cells.

Every day the body produces millions of different antibody-producing cells in the bone marrow. Each of these cells produces a different, unique antibody. The end-tips of the antibodies have what is known as a “variable region” that is different for every antibody and forms a unique three-dimensional shape. If that antibody finds an antigen that has the mirror inverse of the shape at the variable-tip, then the antibody and antigen will bind to on another like a key fitting into a lock.  When that happens the B-cell that makes that particular antibody knows it has a “winner” and starts to mass-produce that antibody. An invader coated in antibodies can be easily identified and eliminated. The antibodies coating the surface of invading bacteria or virus often have an additional effect of preventing them from attacking the body or reproducing, speeding their elimination.  A single infectious organism can trigger the production of dozens or even hundreds of different antibodies against it, as there will be lots of different “fits” -- since each organism has many different antigens on its surface.  These first antibodies vary in their efficiency for targeting the foreign invader, but as time goes on the response will “mature” as the immune system adapts and produces antibodies better able to target the invading antigens.

Vaccines are mixtures of antigens that can activate the immune system without causing an infection. One common tool for making a vaccine is to use heat-killed bacteria or viruses. The immune system is thus presented with the shell of the invader, and can start producing antibodies against those antigens.

Because we are exposed to millions of different antigens, the immune system has a method to distinguish occasional threats from persistent threats. If it wasted all its efforts mass-producing antibodies against infections you will never experience again, it could not be ready for the more dangerous diseases.  For this reason there are memory cells. When an infection runs for a long time, or if a creature gets infected by the same disease again and again, some of the best antibody-producing cells will convert into memory cells. These are antibody-producing cells that are effectively in storage. They drift through the bloodstream, often for years, waiting and watching for the invader for which they optimized to reappear. If that invader comes back, the memory cell immediately kicks into gear: it makes thousands of copies of itself, starts cranking out antibodies, and mobilizes the rest of the immune system against the attacker. This speeds the response time of the immune system from weeks to days, or even hours.

Vaccinations are  typically given in two doses four to six weeks apart because this is the best method to activate the immune system (first dose), and then cause a maturation of the response and the production of memory cells (second dose). Booster shots cause the memory cells to activate and reproduce, increasing their numbers in the bloodstream. This is necessary because the memory cells do eventually die, so without periodic boosters the immunity would gradually fade. For most human vaccines we know how long the memory cells against various antigens last, and thus doctors prescribe different periods for booster shots (3 years, 10 years, etc.). In camelids, the lifespan of the memory cells is not known, but as the common vaccines are known to only provide about 12 months of protection in cattle and sheep it is recommended that booster shots be given at least once and preferably twice per year to ensure protection.

If you ever give a new type of vaccine (such as switching from 5 in 1 to 10 in 1) you need to give the two doses, about six weeks apart, to trigger the production of the memory cells.           

Recommendations for vaccinations:

Many different vaccines are available.

Ask your vet about what is best for you.

Newborn cria

1 ml of vaccine at 6 weeks, subcutaneous injection

1 ml of vaccine at 10-12 weeks, subcutaneous injection

Adults

2 ml of vaccine every 6-12 months, subcutaneous injection.

Adult animals should be given a booster shot every 6 to 12 months. Once a year may be enough, twice a year provides additional security. Most animals in NZ need some selenium supplementation, and the vaccine is a good time to do so. Selenated vaccines should not be given to newborn animals, as it can result in a selenium overdose. If you are unsure of the selenium levels in local feed, consult your vet.