Purpura haemorrhagica is a rare complication of equine strangles and is caused by bleeding from

capillaries A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...

which results in red spots on the skin and

mucous membranes A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

together with

oedema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...

(swelling) of the limbs and the head. Purpura hemorrhagica is more common in younger animals.

Pathophysiology

Horses that develop purpura hemorrhagica usually have a recent history of strangles (infection with ''Streptococcus equi'' subsp. ''equi'') or vaccination (intramuscular or intranasal) for strangles. It is thought to be caused by an auto-immune reaction where antibodies against the ''S. equi'' M- or R-protein cross-react with proteins on endothelial cells. This results in

vasculitis Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily caused ...

, leading to subsequent severe peripheral edema in the legs and ventral abdomen, as well as petechiation or

ecchymoses A bruise, also known as a contusion, is a type of hematoma of tissue, the most common cause being capillaries damaged by trauma, causing localized bleeding that extravasates into the surrounding interstitial tissues. Most bruises occur clos ...

over the mucous membranes. Purpura hemorrhagica can also rarely be seen after infection with ''S. equi'' subsp.''zooepidemicus'', ''

Rhodococcus equi ''Rhodococcus equi'' is a Gram-positive coccobacillus bacterium. The organism is commonly found in dry and dusty soil and can be important for diseases of domesticated animals (horses and goats). The frequency of infection can reach near 60%. '' ...

'', ''Corynebacterium pseudotuberculosis'' (causative agent of pigeon fever), equine influenza virus, or equine herpes virus type 1, or without any apparent infection.

Clinical signs

The most common clinical sign is subcutaneous edema of the limbs and hemorrhages on mucous membranes. Other clinical signs include depression, anorexia, fever, elevated heart and respiratory rate, reluctance to move, drainage from lymph nodes, exudation of serum from the skin,

colic Colic or cholic () is a form of pain that starts and stops abruptly. It occurs due to muscular contractions of a hollow tube (small and large intestine, gall bladder, ureter, etc.) in an attempt to relieve an obstruction by forcing content out. ...

epistaxis A nosebleed, also known as epistaxis, is bleeding from the nose. Blood can flow down into the stomach, and cause nausea and vomiting. In more severe cases, blood may come out of both nostrils. Rarely, bleeding may be so significant that low bl ...

and weight loss. Rarely, horses may also develop disseminated intravascular coagulation (DIC), leading to

infarct Infarction is tissue death (necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as an infarct (from the ...

ion of various organs, or chronic

myositis Myositis is a rare disease that involves inflammation of the muscles. This can present with a variety of symptoms such as skin involvement (i.e., rashes), muscle weakness, and other organ involvement. Systemic symptoms such as weight loss, fatigue ...

and muscle atrophy.

Treatment

Treatment usually involves high doses of steroids such as

dexamethasone Dexamethasone is a glucocorticoid medication used to treat rheumatic problems, a number of skin diseases, severe allergies, asthma, chronic obstructive lung disease, croup, brain swelling, eye pain following eye surgery, superior vena ...

. While high doses of steroids may risk

laminitis Laminitis is a disease that affects the feet of ungulates and is found mostly in horses and cattle. Clinical signs include foot tenderness progressing to inability to walk, increased digital pulses, and increased temperature in the hooves. Seve ...

, low doses are associated with refractory cases. Antibiotics are used to treat any residual nidus of ''S. equi''.

Non-steroidal anti-inflammatory drug Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...

s (NSAIDs), such as

phenylbutazone Phenylbutazone, often referred to as "bute", is a nonsteroidal anti-inflammatory drug (NSAID) for the short-term treatment of pain and fever in animals. In the United States and United Kingdom, it is no longer approved for human use (except in th ...

flunixin Flunixin is a nonsteroidal anti-inflammatory drug (NSAID), analgesic, and antipyretic used in horses, cattle and pigs. It is often formulated as the meglumine salt. In the United States, it is regulated by the U.S. Food and Drug Administration ( ...

, may be useful to reduce fever and relieve pain. Intravenous

DMSO Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds ...

is sometimes used as a free-radical scavenger and anti-inflammatory. Additionally, wrapping the legs may reduce edema and skin sloughing. Supportive care with oral or IV fluids may also be required.

Prognosis

Prognosis is good with early, aggressive treatment (92% survival in one study).

Prevention

Purpura hemorrhagica may be prevented by proper management during an outbreak of strangles. This includes isolation of infected horses, disinfection of

fomites A fomite () or fomes () is any inanimate object that, when contaminated with or exposed to infectious agents (such as pathogenic bacteria, viruses or fungi), can transfer disease to a new host. Transfer of pathogens by fomites A fomite is any ...

, and good hygiene by caretakers. Affected horses should be isolated at least one month following infection. Exposed horses should have their temperature taken daily and should be quarantined if it becomes elevated.

Prophylactic Preventive healthcare, or prophylaxis, consists of measures taken for the purposes of disease prevention.Hugh R. Leavell and E. Gurney Clark as "the science and art of preventing disease, prolonging life, and promoting physical and mental hea ...

antimicrobial treatment is not recommended. Vaccination can reduce the incidence and severity of the disease. However, horses with high SeM antibody titers are more likely to develop purpura hemorrhagica following vaccination and so these horses should not be vaccinated. Titers may be measured by

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presen ...

References