The Lymphatic System: Part 2

Conditions of the Lymphatic System

In the Lymphatic System Part 1, we learned about lymph and its role within the equine body. Check out the link if you missed Part 1 then join us back here to learn more about conditions of the lymphatic system.

Today we will take a look at some examples of problems associated with the lymphatic system – some you may be familiar with, or even had experience with, during your time as a horse owner:

1) OEDEMA: in simple terms, oedema means a subcutaneous swelling that distorts and stretches the overlying skin. As we learned in Part 1, due to reduced flow in the distal region of the horse’s limbs as well as the fact that the lymph vessels are having to move lymph upwards against the force of gravity to travel back up the legs, back pressure can develop in the following:

VENOUS CAPILLARIES: This causes more fluid to be forced through the walls into the space between the tissue cells, therefore becoming interstitial fluid. This interstitial fluid needs to be absorbed by the lymphatic system to prevent waterlogging.

LYMPHATIC VESSELS: This is a knock-on effect from the back pressure within the venous capillaries as there is an increase in interstitial fluid and this puts more of a load on the lymphatic system which needs to absorb this extra fluid and transport it, with no muscular contraction, back up the legs.

Ultimately, what tends to happen is that the excess fluid fills the subcutaneous (under the skin) spaces of the lower limb which produces a soft swelling. These swelling are oedema, and is the most common area that it occurs, however it is not only the lower limbs that are associated with oedema. Oedema can occur for pathological and non-pathological reasons, as explained below.

PATHOLOGICAL CAUSES:

• A blockage due to infection/disease within the system or due to an allergic reaction that can cause inflammation and lymph node enlargement, resulting in a blockage.

• Overloading of the lymphatic system, which tends to happen as a result of the above compromising the lymphatic system’s ability to drain the area.

Pathological blockages/overloading can occur anywhere along the lymphatic system and can take some time to clear.

NON-PATHOLOGICAL CAUSES – EXTERNAL & INTERNAL

Examples of external mechanical forces that affect the flow of lymph are:

• Incorrectly fitted bandages (too tight or insufficient padding).

• Chronic scarring which has thickened the surrounding tissue causing a partial blockage.

Examples of internal mechanical forces that affect the flow of lymph are:

• Underlying new bony prominences

• A heavily pregnant mare with pressure from the foetus inside the womb

• Dietary blockages (a biochemical effect) such as overfeeding – especially protein-rich nutrients that can change osmotic pressure (as discussed in Part 1) or freshly harvested hay fed too soon before the nitrogen is fully converted.

Oedema is painless and slightly cold to the touch plus pressure from a thumb or finger should cause a dent that, upon release, will refill. It is important to identify this type of painless oedema from an inflammatory oedema that is usually warm to the touch and does not dent on thumb pressure and is usually painful for the horse. If in doubt, always contact your horse’s veterinarian.

2) LYMPHANGITIS

In simple terms, lymphangitis is an infection spreading up the lymphatic vessels of the leg causing hot, painful swelling. Lymphangitis can sometimes be mistaken as “filled legs” from oedema but it is far more serious and painful for the horse.

Often, lymphangitis is caused by an infected wound on the lower leg that has gone unnoticed. When untreated, the infection can spread rapidly up the lymphatic vessels causing hot, painful swelling, usually of the entire limb, however lymph glands and vessels are particularly swollen. Similarly, lymphangitis can occur due to an infection lying dormant in the lymph glands of the proximal (top) region of the limb; they become inflamed as a result of filled legs restricting flow and therefore the body’s ability to flush out the infection – the infection then spreads rapidly down the limb.

SYMPTOMS OF LYMPHANGITIS

• Hot, painful swelling of affected limb(s)

• Painful to digital pressure (touch)

• Lymphatic vessel standing out like a cord

• Fever & obviously ill

• Obviously lame

• Possibly holding foot off the ground

• Serum may ooze from the skin where close to the bone

Hind legs tend to be more commonly affected than forelegs and horses that are frequent sufferers of filled legs from oedema are more prone to the problem with it often occurring in the same leg as a result of an ever-increasing fibrosis thickening.

COMMON TREATMENT OF LYMPHANGITIS (these are just examples - always consult your horse’s veterinarian for a personalised treatment plan)

• High doses of antibiotics to control infection

• Anti-inflammatory drugs such as Phenylbutazone and diuretics to reduce inflammation & swelling

• Pain killers to enable short periods of walking to help promote drainage

• Hot poultice followed by massage and bandaging of the leg from the hoof upwards

If prompt veterinary advice and comprehensive treatment are not given, the infection can become chronic, often resulting in permanent thickening of the leg. Even with correct and immediate treatment, however, some horses are still left with a fibrous thickening for life.

PREVENTION IS BETTER THAN CURE

• Always inspect legs for cuts etc. especially on horses with long feathers which can hide infected wounds.

• Treat all wounds, however small, immediately to help prevent the spread of infection.

• Avoid leaving your horse standing for long periods of time with no form of exercise.

3) STRANGLES

In its simplest form, strangles is a disease primarily associated with the upper respiratory tract caused by infection from a contagious bacterium called Streptococcus Equi. Symptoms of strangles interfere with swallowing and breathing, hence the name “strangles” which is symptomatic of choking or strangulation. The disease is highly contagious and has an incubation period of between 3-10 days. It only affects horses.

Streptococcus Equi is a pus-producing germ that circulates in both the vascular and lymphatic systems. It is more common in very young or very old horses but can strike at any age. It is passed on by direct contact with an infected or carrier animal, indirect inhalation or ingestion of fomites. Contaminated bedding, grooming kits, tack, feeding utensils and troughs are all possible sources of contamination. Entry into the system is gained at the back of the throat and settles quickly in the tonsils and adjacent lymph nodes before spreading to lymph nodes of the back of the head and neck, causing the familiar swelling and abscesses associated with the disease. Rarely does it spread beyond these lymph nodes, however, if it is absorbed into the bloodstream it can spread rapidly throughout the body.

The salivary glands often associated with Strangles.

SYMPTOMS OF STRANGLES

• Depression.

• High temperature.

• Slight cough.

• Loss of appetite due to soreness to swallow & loss of smells to detect “safe” foods.

• Tender swellings behind the ears, angle of the jaw, and between arms of the lower jaw.

• Obstruction of the respiratory system which can cause stress.

• The horse will often stand with its head stretched out to aid breathing.

• Slight respiratory noise due to pressure on larynx and pharynx from lymph node swellings

• One or more glands will continue to swell and burst after a few days, releasing quantities of pus.

Once the glands have swollen and burst, most horses recover relatively quickly with minimal complications, however in the very young or old, the bacterium can spread via the circulatory system and cause abscesses in the lungs and brain or via the lymphatic system into the lymph nodes of the abdomen. Complications such as these are referred to as “Bastard Strangles” and the prognosis is poor.

COMMON TREATMENT OF STRANGLES (these are just examples - always consult your horse’s veterinarian for a personalised treatment plan)

If you have any reason to suspect possible strangles, the horse should be immediately isolated and the Veterinarian called. Formal diagnosis is obtained via laboratory tests of a swab taken from the nasal mucosa or pus from a burst abscess. However, whilst waiting for the Veterinarian to arrive and subsequently for results to come back, here are some immediate actions you can take to minimise the spread of this contagious disease:

• Isolate the infected horse.

• Disinfect food containers, grooming kit and where possible, the handler of the horse.

• Everything that has been in contact with the infected horse should be washed thoroughly.

• All possibly contaminated bedding should be incinerated.

• All buildings should be sterilised.

• Careful nursing of the animal – abscesses should be encouraged to mature and burst with constant application of heat (bathing in warm water or using a heat pad).

• Sometimes it is necessary to lance the abscess.

• Steam inhalation can help to aid breathing.

• Offer soft/palatable food

• The horse must remain in isolation until given the all-clear by the vet (usually after a number of consecutive clear swabs over a two-week period).

Antibiotic treatment is not prescribed in most cases as it is thought by some that such medication can actually delay the development and subsequent bursting of the abscesses and can increase the possibility of “bastard strangles” forming.

Recovery can begin after the glands have burst, however, the period of recovery is long, slow, and gradual and it is important to stay vigil and follow veterinary advice.

PREVENTION IS BETTER THAN CURE

Good housekeeping is essential and could save you a lot of time, hassle and heartache by hopefully, vastly reducing the chance of infection breaking out on your yard. By following sensible guidelines you can help reduce the risk of an outbreak, however, any yard with horses coming and going on a regular basis cannot realistically prevent the risk altogether. It is also important to remember that horses can be carriers without showing any visual symptoms. General house-keeping tips to minimise the risk of strangles include:

• Isolate new horses where possible for a minimum of 2 weeks.

• Ask a vet to swab all horses at the first sign of “out of character” nasal discharge.

• Avoid sharing grooming kits, rugs, stables etc.

• Disinfect stables after a horse has left and before a new horse moves in.

• Be vigilant at all times and never become complacent to aid in early detection.

• If strangles is identified, act quickly and consult your Veterinarian immediately.

So now you can see how the lymphatic system plays a vital role within your horse’s body yet is very often overlooked or simply not understood by many owners. This series is just a snippet of knowledge that I have gained through my Equine Massage training and personal research. Always consult your vet for any advice relating to the medical diagnosis and treatment of your horse, but knowing what to look for and being aware of such conditions can be very helpful.

I hope you have enjoyed my Lymphatic System Series. I will be uploading informative blogs such as this on a regular basis so to make sure you don’t miss out, please “Like” my Facebook page Equilibriagold and check out my website blog regularly www.equine-therapy.co.uk/blog

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