VET CLINIC
In association with
Mark Andrews, BVM&S CertEP MRCVS, of
Equine Science Update
we are pleased to provide the latest Equine Veterinary Information
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STRANGLES
Strangles is an acute, contagious infectious disease that affects specimens of the equines. The patient is usually a foal or a young horse. It will usually manifest itself in abscess formation in the lymph nodes of the head and also high fever.
THE BACTERIA:
Strangles is caused by a bacteria called Streptococcus equi - a group C, Gram positive Streptococcus. The bacteria is very resistant to outside factors, and can survive in dried puss and discharge for weeks. At a temperature of 70 degrees Celsius (around 158 degrees F) it takes around two hours to kill it, and it is also very resistant to disinfectants.
EPIDEMIOLOGY:
Infection happens via inhalation or per os (via the food or drink). Sick horses will cough and little drops will spread out for other horses to inhale or to infect the bedding or feed. Infection through little wounds in the skin has also been discussed as a source, and also via breeding (the abscesses will then affect the genital area and the perineum). There are clinically healthy horses that can also spread the disease.
SYMPTOMS:
Most typical cases will be seen with fever and catarrhactic inflammation in the upper respiratory tractus and abscess forming in the head's local lymph glands. The typical patient is a foal over 2 months of age, and also weanlings and young horses, but also adult horses and older horses can be infected. The horse will get infected easier if they are reduced in some way in advance, like a cold, over worked. other infections etc. Incubation is 4-8 days (but can vary from 1-14 days in extreme cases). First symptoms: High temperature, clear seromucous (clear and slimy) nasal discharge, red mucous membranes in the nose. After a couple of days the temperature will sink, but will increase again when the formation of abscesses in the lymph nodes starts. The horse will be tired and exhausted and will not eat. The throat will be infected, and after a while the mandibular lymph nodes will become painful and swollen. There will be a diffuse, warm and tender swelling underneath the jaw. After 8-10 (2-4 weeks in older horses) days the abscesses will mature into swellings that will lose the hairs on the surface, and open up to the surface, pouring out lots of yellow, thick puss. Fever will then drop. For several days the abscess will drain puss and liquid to the surface, and after 2-3 weeks, the Strangles is normally over. The horse can show quite a bit of discomfort from the infection, and will in some cases stand with the head stretched out. They will have a cough, and will have difficulties eating and swallowing. The nasal discharge will become more and more like puss. Drinking is difficult as the back part of the soft palate is swollen from the infection. In more serious cases death may occur in less than a week, the cause of death will vary with what turn the disease makes. This was the typical horse.
In some cases less typical, the symptoms might not be so clear to what the cause is. Maybe a stable full of horses with runny noses and no fever, then some of them get draining abscesses. Other horses will get abscesses in different lymph nodes, and some will not show much from the outside. This can cause problems in swallowing and breathing. Some abscesses can also open and drain to the inside of the throat, which could increase the danger of suffocation and pneumonia if the puss runs down the windpipe. The abscesses can also open into the air sacs. With internal spreading, the infection can also spread throughout the body to larger lymph nodes, intestines, lungs, kidneys, heart, skin and brain and cause different other conditions. A pyemia can also occur with outbreaks of abscesses virtually anywhere in the body.
A horse that has undergone an infection usually has a long period of immunity, but this seems to wear off in some cases and make the horse susceptible to the Str. equi infection again.
After effects: Some times paralysis of some larynx muscles resulting in roaring, some times serious dermatitis, some times damage to the heart muscle that makes the horse unsuitable for hard work. Purpura haemorrhagica (wide spread subcutaneous oedema and haemorrhagic swellings particularly in legs and underneath the chest and abdomen) is a follow up to infectious disease, especially strept-infections like Strangles. Symptoms: Will appear a few days- 2 weeks after previous infection, or overlapping. More common in grown horses. First symptoms are usually bleeding (points or stripes, but can gather to make larger areas) in the mucous membranes, and some times you can see them in unpigmented skin. You can also find oedematous swellings in different parts of the body. After a while, from the affected areas there will be fluids penetrating through the skin, some times clear and runny, some times more like pus, some times also clear liquid mixed with blood. Ulcerations can also happen. Shortly after you will see subcutaneous swellings, mostly on the legs, head, and underneath the chest and abdomen (often including the prepuce in males, making it difficult for them to urinate). The swellings can take on huge proportions. The skin over the swellings will be penetrated by sticky yellowish fluids that can dry into crusts, some parts of the skin can get necrotic and fall off. The huge swellings in the head and throat can make it very difficult for the horse to eat, drink and swallow.
TREATMENT AND PREVENTION:
The bacteria is very susceptible to penicillin and sulphonamides. It might also be a point to increase the maturing of the abscesses and also to open them surgically when mature enough (when a distinct pocket or capsule filled with puss has been built within the lymph node). Make sure the horse has a snug place to be stabled, but with fresh air, and also easily digestible feeds that are also easy to chew and swallow.
Isolation and restrictions on movement of horses. New protective clothing to prevent spreading when people move from yard to yard.
Vaccination: Different vaccines have been developed with varying effect. There are different opinions as to whether the vaccines work or not.
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