STUD NOTES

PLASMA - A BLOODY GOOD BACK UP!

The availability of commercial frozen plasma that is collected and packaged professionally, has provided us with a safety net for foals that experience Failure of Passive Transfer, or where antibody levels dip as they are called upon to combat illness in the sick foal. With frozen plasma we can now effectively establish, or reinstate desirable immunoglobulin levels in the young foal where colostrum is no longer an option.

The commercial plasma collected comes from donors that are tested free of a wide range of diseases such as EIA, Equine Morbillivirus, EHV 1 & 4, Ross River Fever and so on. It is also free of maternal haemolytic agents that can attack the foal’s red blood cells (through colostrum or milk) and are found in blood stream affected mares.

Commercial plasma does not contain any additives or preservatives and is frozen at harvesting. This means plasma is very sensitive to how it is stored, thawed and handled by the end user.

Naturally, all of the above facts result in a product that is not cheap at face value. By the time you have finished reading this article, I will however, have you convinced that plasma is cost effective in the scheme of things.

Reasons for plasma administration:

• Failure of Passive Transfer (FPT)

This topic is widely covered in my articles about
IgG testing and Colostrum and Immunoglobulin

If, for whatever reason, the foal has failed to receive desired immunoglobulin levels outside the window where Passive Transfer can take place, then we can use plasma. In other words, colostrum is no longer an option to boost the antibody levels and plasma is now the course of action. This is perhaps the most common use of plasma.

• Sick foals

Despite ‘Best Practice’ when dealing with IgG levels in the correct time frames, young foals still can, and do, get sick. When challenged by pathogens (a broad term for disease producing microorganisms or material), the foal will combat illness by using its own natural antibodies. This will in turn deplete the antibody reserve and can place the foal in a compromised position. If these reserves are decreased below critical point, the foal will probably become ill. Antibody levels will possibly spiral downwards, and seriously threaten the foal who may lose the ability to fight the disease in question. Immediate use of antibiotics is the first line of defence with the combination of correctly prescribed drugs for bolstering antibody levels being an extremely effective practice in assisting the sick foal.

Foals can be born very ill. This is what we term a septic foal: the foal has a blood infection at, and often prior to birth. The foetus has been challenged ‘in utero’ by a pathogen presence during the pregnancy so the foal is born with a sepsis. In this case we have a foal that is born with no antibodies, and worse … is sick, requiring immediate help. The fastest way to get antibodies into the blood is with plasma. Plasma administration places immunoglobulins directly into the bloodstream where they can immediately go to work: just like calling in the army!

The fastest way to take the illness head on is with drugs such as antibiotics which directly act on the bug in question. Providing the foal colostrum from the mare will provide the foal with nutrition and antibodies, but is a much slower delivery.

In this circumstance we will most likely use all three treatment procedures - drugs, colostrum and plasma

• Colostrum Banks low or non existent

Colostrum Banks are extensively covered in my article on Colostrum and Immunoglobulin.
An unfortunate fact is that colostrum banks are difficult to maintain with high levels of reserve … even for large farms such as Yallambee. Where small farms are concerned, there quite often isn’t the opportunity to have spare colostrum on hand. So, where sufficient colostrum is not available, and the window of passive transfer has closed, plasma is now the only option to get the antibody levels of the foal up to the desired adequate levels.

Here’s a situation that we, as a farm, can be faced with: our colostrum bank may not be as high as we would like. We have a mare running milk, and she has run most or all her colostrum out - not an unusual circumstance. In fact, at the time of writing I have three such mares in the foaling paddocks. These foals will need the approximate equivalent to 1 litre and probably more for a bigger foal, of high quality colostrum. This would mean we would need donations to our bank from 3-6 mares, depending on the quantities we were able to steal from these individual donors.

(Remembering, of course, that our donor group is restricted)

This one mare running milk is going to have a significant impact on our bank. The question here is: do we use up all this colostrum on one foal? (This is a considerably cheaper option for the owner than using plasma).

Next consideration: there are a great number of foals that just need a simple top up using one donation from our bank to get their IgG levels over the 800mg/dl at the cost of say $25-50.

Effectively, 3-6 individual foals can have cheap top ups with the same amount of colostrum it takes to give one foal whose mother has lost her own supply.

Should this owner be exposed to the possibility of us having to use the expensive plasma because we have run our colostrum banks dangerously low with foals such as the one mentioned above?

Of course, the answer is ‘NO’ - no way should owners who only need access to a ‘top up’ dose of colostrum be exposed to the possibility of having to use plasma if at all possible.

Generally, when this scenario arises we would give the foal that requires large quantities of colostrum a combination of colostrum (as much as we feel we can afford) from our bank, and plasma administration top up. I hope the reader appreciates some of the dilemmas we face with this subject.

Administering Plasma to the Foal

Commercially collected and packaged plasma is a reasonably recent phenomenon. Once IgG testing came into the equation, it actually opened up a whole new tin of worms. We now knew foals were failing their IgG tests, and approximately by how much. At the time, for varying reasons, a large percentage of foals were tested outside the time frame where colostrum could be used to reach the desired level.

So where did we get the plasma from?

It came from the mother of the foal and this was not a simple procedure. We needed fancy stuff such as a good bleeding needle, anti coagulant and blood donor bags and lines big enough to accommodate fast flow of blood from mare to bag. What we did was place the anticoagulant into the blood donor bags (the large bags sourced from human blood banks and were three litres in capacity). For the purpose of appreciation here, I have a photo of my bleeding needle - I have two of these big suckers: still used today for emergency blood transfusion. To drive this needle in requires local anaesthetic and a small cut to break the skin over the jugular. Once the blood was collected we would hang the bag in the fridge until the red blood cells had settled from the plasma. We would then draw off the plasma into another sterile bag for intravenious administration. Collection bags became more sophisticated later on, where drawing off was made much simpler. Oh, and of course a stitch was required to stop the bleeding on the mare once we finished collection. Then we had to set up fluid lines with blood filters to administer the plasma intravenously to the foal.

And, all of this had to be performed in a sterile manner.

Quite a bit of work really! Thank goodness we can now just buy it, and of a much superior quality than we were able to collect. Although plasma is regarded as expensive, the effort to self collect would add up to just as much, if not more and we have the quality control. Sure, we don’t get ‘local’ farm immunoglobulins in purchased plasma, but the horses they use are hyper-immunised so they have high antibody levels relating to all general illnesses a foal is likely to be challenged with.

Once it is determined that plasma supplementation is required, we need to get organised fairly quickly. For those foals that are receiving plasma due to illness, intravenous fluid therapy lines would already be in place, so it is just a matter of hooking the plasma bag into the system.

For foals that require a top up as a result of low immunoglobulin levels, plasma supplementation is not an emergency procedure but should be done at the first opportunity - inside a day or two. Plasma is supposed to be administered into the bloodstream at a slow drip rate to avoid reactions.

It’s a shame we can’t just run it in flat out - it would be much simpler. Administration lines are needed, just as fluid therapy and we use a bag of Hartmann’s as part of the set up, and to dilute the plasma for easier flow. The Hartmann’s is used to initially fill the lines and connect to the catheter in the foal’s vein preventing any wastage of the precious plasma. Once the fluid lines are established as working efficiently, we will then hook in the plasma. Using the set up in our foal hospital, we do not need to remain present whilst the plasma is running in but we do keep a close eye on things.

How much Plasma?

Plasma is packaged in bags that contain 220mg/dl at the volume of 1 litre bags that hook straight into fluid administration lines. Due to the expense of the plasma, we do not want to open up any more than we need. This is where our accurate IgG testing comes into play and using the DVM system we get precise readings of our IgG levels.

Say the foal has a final reading of 677mg/dl, then we would most likely only need one bag of plasma. If the level was 408mg/dl - more would be required, probably two bags at least. In this event, after the two bags have been administered, an IgG test would be performed before opening subsequent plasma bags.

For the sick foals, the same applies - we can check IgG levels and then use plasma as required. The DVM system is extremely useful here as we are not guessing how much plasma we require - too little plasma is of little use, and too much is expensive and wasteful.
The very sick foal may need daily checking of IgG for a couple of days as they draw on this plasma resource as part of combating the illness. As they are likely to still be on maintenance supportive fluids, adding a bag of plasma is simple.

Reasons for the high cost of Plasma for the end user

• Initial purchase cost from collector/supplier
• Transportation and storage of a sensitive, frozen product - we store our plasma in our home freezer, so should there be a power issue, the plasma thawing is less likely to be overlooked! Frankly I would rather use that space up for frozen chips to feed my two sons with massive appetites, but looking after the viability of pre purchased plasma is more important.
• The middle man - of course
• Holding costs - We will store at one time at least three bags of plasma to have on hand when required.
• Method of administration - IV fluid lines
• Sensitivity - The product must remain properly frozen at all times without the chance of thawing & re freezing to remain fully viable. When ready for consumption, thawing has to be done slowly. If too anxious and you thaw it in water that is too warm, you may as well pour your plasma down the sink. And no, microwave thawing is not an option. Plasma contains protein: just imagine what happens when you microwave an egg!

Commercial plasma, once thawed has a refrigerated viability of 20 days.

Other uses for Plasma

• Oral administration for young foals: this still goes on, and is not a practice we use here. There is a school of thought that there is a benefit to giving a neonate or sick foal a charge of about 100ml of plasma orally. It works, but to a lower level and is a costly way to use an already expensive product.
  
  
• Uterine infusion: we used to do this a lot … treat mares that were high risk of not going in foal with plasma infusion. I do know of a very good local vet that still uses this from time to time. Back when we used to collect on farm I used to bleed large quantities from a gelding, and package the plasma in ready to use doses in syringes and freeze it. We’d know who was going to be treated with it in advance, so we’d just go to the deep freeze and pull out a dose
  
  
• Eye treatments: often plasma is used as part of an eye mix to treat eye ulcers and the sort. Only a small amount is required so just taking a few blood collection vials from the patient, spinning down and drawing off the plasma is no big deal.
  
  
• Wounds: I have used plasma on bad wounds, but usually if I am finishing off an already opened bag. It would be a mighty expensive treatment otherwise, but I must say I feel that it is beneficial if the opportunity is there to include it in the wound recovery regime.

After playing around with colostrum supplementation, IgG testing, plasma and sick foals for many years, I maintain that plasma, although pricey at face value for the end user, is very cost effective. Recovery of a foal already predisposed with illness has a considerably better chance of speedy and full recovery and limits the depths of illness it may reach. For foals with low immunoglobulins as a result of Failure of Passive Transfer it is amazing how often they contract some form of illness such as joint ills, lung related illness and so on. A sick foal under 20 days or so of age (which is when the foal has built up more immunities of its own) is something that can be very effectively averted with correct management, and plasma is very much a part of that management.

We all know how much it costs to recover from a sick foal with one of the above mentioned scenarios, and it’s a hell of a lot more than the plasma … especially if you end up at a veterinary hospital. Not only that, the ongoing price of a sick foal is the compromise in growth - at an age which is quite profound.