Strangles (equine distemper) is a

contagious Contagious may refer to: * Contagious disease Literature * Contagious (magazine), a marketing publication * ''Contagious'' (novel), a science fiction thriller novel by Scott Sigler Music Albums *''Contagious'' (Peggy Scott-Adams album), 1997 * ...

upper respiratory tract infection An upper respiratory tract infection (URTI) is an illness caused by an acute infection, which involves the upper respiratory tract, including the nose, sinuses, pharynx, larynx or trachea. This commonly includes nasal obstruction, sore throat, t ...

of horses and other

equines ''Equus'' , is a genus of mammals in the family (biology), family Equidae, which includes horses, donkeys, and zebras. Within the Equidae, ''Equus'' is the only recognized Extant taxon, extant genus, comprising seven living species. Like Equida ...

caused by a Gram-positive

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

, ''

Streptococcus ''Streptococcus'' is a genus of gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occurs ...

equi''. As a result, the lymph nodes swell, compressing the

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struc ...

larynx The larynx (), commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...

, and

trachea The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...

, and can cause airway obstruction leading to death, hence the name strangles. Strangles is

enzootic Enzootic is the non-human equivalent of endemic and means, in a broad sense, "belonging to" or "native to", "characteristic of", or "prevalent in" a particular geography, race, field, area, or environment; native to an area or scope. It also has t ...

in domesticated horses worldwide. The contagious nature of the infection has at times led to limitations on sporting events.

Signs

Shetland pony with strangles (side view)

A horse with strangles typically develops abscesses in the lymph nodes of the head and neck, causing coughing fits and difficulty swallowing. Clinical signs include

fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...

up to 106°F and yellow-coloured nasal discharge from both the nose and eyes. Abscesses may form in other areas of the body, such as the abdomen, lungs, and brain. This is considered a chronic form of strangles called "bastard strangles", which can have serious implications if the abscesses rupture. Horses develop this form of strangles when their immune systems are compromised or if the bacteria rapidly invade the body.

Complications

Possible complications include the horse becoming a chronic carrier of the disease,

asphyxia Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can i ...

due to enlarged

lymph nodes A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

compressing the

windpipe The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the la ...

, bastard strangles (spreading to other areas of the body),

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...

guttural pouch Guttural pouches are large, auditory-tube diverticula that contain between 300 and 600 ml of air. They are present in odd-toed mammals, some bats, hyraxes, and the American forest mouse. They are paired bilaterally just below the ears, behind the ...

filled with

pus Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...

es,

purpura haemorrhagica Purpura haemorrhagica is a rare complication of equine strangles and is caused by bleeding from capillaries which results in red spots on the skin and mucous membranes together with oedema (swelling) of the limbs and the head. Purpura hemorrhagica ...

, and

heart disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...

. The average course of this disease is 23 days.

Cause

The disease is spread by an infected horse when nasal discharge or pus from the draining

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inclu ...

s contaminate pastures, feed troughs, brushes, bedding, tack, etc.

Prevention

Both intramuscular and intranasal vaccines are available, although their efficacy is rated at no more than 50%. Isolation of new horses for four to six weeks, immediate isolation of infected horses, and disinfection of stalls, water buckets, feed troughs, and other equipment can help prevent the spread of strangles. As with any contagious disease, hand washing is a simple and effective tool.

Treatment

As with many streptococcal infections,

beta-lactam antibiotics β-lactam antibiotics (beta-lactam antibiotics) are antibiotics that contain a beta-lactam ring in their chemical structure. This includes penicillin derivatives (penams), cephalosporins and cephamycins (cephems), monobactams, carbapenems and ...

(e.g

penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...

s) are the most effective treatments, but some authorities are of the opinion that use of antibiotics is

contraindicated In medicine, a contraindication is a condition that serves as a reason not to take a certain medical treatment due to the harm that it would cause the patient. Contraindication is the opposite of indication, which is a reason to use a certain tre ...

once abscesses have begun to form, as they predispose to

lymphatic Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to ...

spread of the infection (bastard strangles), which has a much higher mortality rate. After an abscess has burst, keeping the wound clean is important. A diluted

povidone-iodine Povidone-iodine (PVP-I), also known as iodopovidone, is an antiseptic used for skin disinfection before and after surgery. It may be used both to disinfect the hands of healthcare providers and the skin of the person they are caring for. It may a ...

solution has been used with good results to disinfect the open hole, flushing the inside with a syringe-tipped catheter or with a

teat A teat is the projection from the mammary glands of mammals from which milk flows or is ejected for the purpose of feeding young. In many mammals the teat projects from the udder. The number of teats varies by mammalian species and often corre ...

cannula A cannula (; Latin meaning 'little reed'; plural or ) is a tube that can be inserted into the body, often for the delivery or removal of fluid or for the gathering of samples. In simple terms, a cannula can surround the inner or outer surfaces ...

, followed by gentle scrubbing to keep the surrounding area clean. Symptomatic therapy is an alternative treatment, and is where warm packs are used to mature the abscesses so making them less painful and more comfortable for the horse, but once the abscesses have been matured, they must be kept clean to prevent further infections. This treatment for ''S. equi'' only helps reduce pain for the horse rather than curing the infection.

Outcomes

Strangles has an 8.1%

mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of de ...

. Mortality is lower in cases without complications than it is in cases of bastard strangles. The disease is very contagious and

morbidity A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

is high. Precautions to limit the spread of the illness are necessary and those affected are normally isolated. An isolation period of 4–6 weeks is usually necessary to ensure that the disease is not still incubating before ending the quarantine.

Epidemiology

Equines of any age may contract the disease, although younger and elderly equines are more susceptible. Young equines may lack immunity to the disease because they have not had prior exposure. Geriatric equines may have a weaker immune system.

References

External links

Strangles information sheetAmerican College of Veterinary Internal Medicine consensus statement on StranglesStrangles in Horses, fact sheet, MSU Extension serviceStrangles in Horses, Merck Vet Manual
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