There are two different infectious diseases that can strangle a horse by squeezing its throat. Both disorders involve the inflammation of lymph nodes, particularly the nodes of the head and throat region. These diseases can cause airway obstruction leading to death, which explains the name strangles. 'Benign strangles' or equine distemper is enzootic in Europe. 'Malignant strangles' or glanders has not occurred in Europe for the longest time.
Malignant strangles (glanders)
Huge numbers of horses were used during the war from 1914 to 1918 for transport and the cavalry. During that time, hundreds of thousands of horses fell victim to an outbreak of malignant strangles. The illness is caused by a bacterium; but antibiotics did not exist at the time. The last case of glanders that was documented in the Netherlands dates back to 1927. In Germany and Poland, malignant strangles was not extirpated until the end of the fifties. The illness is still enzootic in the Far East. Just how frequently malignant strangles occurs among Chinese horses is not known or the information has not been released. As the Olympic Games took place there in 2008 and horses from all around the world participated, there is a risk that the disease will present itself again in Europe. Horses that have come into contact with glanders must be killed off in the Netherlands in order to ward off a contagious infection.
‘Benign’ strangles (equine distemper)
Nowadays, we only come across the benign type of strangles in our country. It is also called 'equine distemper' and it is caused by a bacterium different from the one that causes the malignant variety. Benign strangles is only contagious among horses, ponies and donkeys; people are not at risk. But the disease is not truly benign: each year brings fatalities among foals and young horses. They develop a high fever and the lymph nodes become inflamed a few days later. The animal has had the worst of it once these burst and pus is released. But if the lymph nodes on both sides of the throat become swollen, the strangles patient can become severely short of breath. And if these abscesses do not rupture to the outside but to the inside of the body, this leads to so-called ‘bastard strangles’ which is generally fatal.
Horses that have been infected with this ‘benign’ strangles bacterium seldom become ill with the disease a second time. They are immune. Which is why vaccination is an obvious choice. But it is not easy to develop such a vaccine. An inoculum was available as early as the seventies, but it did not suffice. A vaccine for strangles was again introduced in the market in 2006, but it was also withdrawn after a few months.
A riding stable owner calls to report a yearling with strangles. He does not say explicitly that such is the case, as he has been in the business for years now and he knows that many veterinary surgeons do not appreciate a ‘layman’ making a diagnosis. But his story leaves little room for doubt. The small stallion has not eaten for some days. The throat is swollen and the animal snores as it breathes. The man fears potential problems with the pension horses and the continuation of the riding lessons. An outbreak of strangles could mean having to shut down the riding stable for weeks. The infection spreads fairly slowly through the stables, but most of the younger horses and ponies do ultimately become ill. The animals infect one another, but the bacterium can also be transferred via a contaminated halter or tools; or via human hands.
I propose that we place the yearling in the last box, with a container of halamid solution in front of the box door. It is used to disinfect the boots of anyone entering and leaving and to disinfect tools. The boxes to the left and right should remain empty and inquisitive persons are to be kept away. Then just wait and see until I have dropped by. That is not until the end of the morning round. Because I want to go home afterwards, have a shower and a change of clothes. I have more house calls to make today.
A number of teenagers, mostly girls, are busy riding and cleaning down horses and ponies when I arrive. And they are chattering. The patient is at the end of the row of boxes with a decontamination container in front of the box door. A rope across the feeding alley keeps everyone at a distance. I am given a dustcoat from the riding stable. The yearling looks pained as it stretches its neck and snores. Thick snot is dripping from its nose. It has a swelling behind its left jaw as large as a coconut that reaches almost to its ear. He has not touched his feed in the trough. The thermometer reaches 40.8 degrees Celsius. It is too late to administer an injection of penicillin: that would only delay the ripening of the abscess without having a healing effect. It is risky to open the abscess using a scalpel: there are major veins and nerves in the throat area. Moreover, it appears the spontaneous breakthrough is not long in the waiting: the swelling is becoming softer. I step into the halamid solution in my boots and I also disinfect the thermometer and my hands.
pus rupturing from a strangles abscess at the side of the throat
We walk along the other boxes and stands. The horses and ponies appear to be fit and they have been eating normally. And there is no visible swelling of nodes. But that is no guarantee: their temperature must be checked; twice a day, for a period of four weeks. There are more than enough takers. A young girl leaves to see to the purchase of the thermometers that are needed. Others divide themselves into a morning- and evening-shift. I am immediately called if any of the animals is found to have a temperature exceeding 38.5 ºC. In that case the animal concerned is administered two injections of penicillin: a fast-acting and a slow-acting penicillin. The infection can be effectively treated in this way, provided that the nodes are not yet swollen. Horses that must be treated in this way must be kept in their box for another week. The other horses are still suitable for riding.
The strangles patient had initially been with the ponies. Moreover, he had been let loose in the outdoor pen together with the other horses. And so there must be more infected animals. But I do not receive a call that afternoon, nor is there any message from the riding stables the next day. Had there been a previous infection with strangles and are the animals now immune? But on the third day, two ponies have a fever. The animals show no signs of being ill: they are lively and have been eating normally. Still, the thermometer indicates forty degrees. They are given an injection with penicillin in each buttock. The slow-acting preparation causes swelling and so injecting it deep in the buttock muscle will least inconvenience the animals. In the weeks to come, I am called to treat one more pony and four horses. There are no more new cases after that.
injection in the buttock
How it ends
None of the treated animals displayed any clinical sign of disease. The strangles patient has virtually completely recovered after three weeks: he is eating normally and is lively. But drops of fluid are still dripping from the lump in his throat. And these contain strangles bacilli. He will therefore have to be kept separate from other animals for a few more weeks. Meanwhile, it has been business as usual at the riding stable.
© Leo Rogier Verberne