What Causes Photosensitization In Horses?

Photosensitization is a serious skin condition in horses and cattle caused by a hazardous combination of certain plants and ultraviolet (UV) light. Certain plants contain photodynamic agents, which then cause a reaction in the animal’s body that leads to ultra-sensitive skin.

What causes horse photosensitivity?

Primary photosensitivity typically occurs when a horse eats a plant that contains a photodynamic compound that reacts to the ultraviolet rays in sunlight. When these compounds circulate in the blood near the surface of unpigmented (pink) skin, the resulting chemical reaction damages tissue.

How can horses prevent photosensitivity?

Sunburn and Photosensitivity in Horses

1. Keep horses stalled during the hours of most intense sun, and avoid turning horses out without access to shade.
2. Use a child-safe human sunblock preparation on areas that are likely to burn.
3. Reapply sunblock regularly.

What causes the liver dysfunction that results in Photosensitization?

If the liver is unable to metabolize certain chemicals normally, they accumulate in the blood. A common cause of hepatogenous photosensitivity is poisoning by grazing plants toxic to the liver or ingesting blue-green algae (cyanobacteria) or fungal toxins.

Which pigment is responsible for Photosensitization?

The photosensitizing agent, phylloerythrin (a porphyrin), accumulates in plasma because of impaired hepatobiliary excretion. Phylloerythrin is derived from the breakdown of chlorophyll by microorganisms present in the GI tract.

What weeds cause photosensitivity in horses?

Primary Photosensitivity
John’s Wort, buckwheat, perennial ryegrass, whiteheads) can cause skin problems when horses ingest or even touch them. Photosensitivity is a severe dermatitis (skin inflammation) that occurs when certain plant pigments damage nonpigmented skin cells with sun exposure.

What is equine Photosensitisation?

Photosensitization is a condition in which skin becomes overly sensitive to ultraviolet light (sunlight). This condition is not sunburn, although the difference can be difficult to distinguish.

How do you reverse photosensitivity?

The single-most effective tool for combating photophobia is precision-tinted glasses, specifically those tinted with FL-41. Research has shown these lenses to relieve even the most chronic of light-sensitive individuals, whether they have migraine, blepharospasm, post-concussion syndrome or another disorder.

How do I get rid of photosensitivity?

To treat chemical photosensitivity reactions, corticosteroids are applied to the skin and the substance that is causing the reaction is avoided. Solar urticaria can be difficult to treat, but doctors may try histamine (H1) blockers (antihistamines), corticosteroids applied to the skin, or sunscreens.

How do you calm photosensitivity?

Topical corticosteroids and cool compresses may alleviate drug-induced photosensitivity. The use of systemic corticosteroids should be reserved for the most severe cases. If sunscreens are not the cause of the photosensitivity, they should be used liberally.

What is the most common type of photosensitization?

(uroporphyrin I, coproporphyrin I, protoporphyrin III) Secondary (Hepatogenous) Photosensitization (Type III): Most common form observed in livestock. Occurs when an animal ingests plants that contain phylloerythrin.

What is for examples of photosensitization?

The type of photosensitivity produced due to direct ingestion of photodynamic substances or metabolically activated agents is called primary photosensitization For example, plants belonging to species such as Hypericum (Fig. 15.14), Fagopyrum (Fig. 15.15), and Parthenium produce primary type of photosensitivity.

What plants cause liver failure in horses?

Pyrolyzadine Alkaloids (PA) Toxicity
They include ragworts and groundsels. Every part of the plant of these two genera is toxic to horses whether fresh or dry. Consumption of these plants causes liver damage. Cell growth is slowed and cells are unable to divide.

What is the mechanism of photosensitivity?

When a drug induces photosensitivity, exogenous molecules in the skin absorb normally harmless doses of visible and UV light, leading to an acute inflammatory response. In phototoxic reactions, the damage to tissues is direct; in photoallergic reactions, it is immunologically mediated.

What makes a good photosensitizer?

The ideal photosensitizer would be a chemically pure drug with specific uptake by the target tissue, minimal dark toxicity (i.e., activated only upon irradiation), high photoactivity (high quantum yield of ROS), rapid clearance to avoid phototoxic side effects, and strong absorption at relatively long wavelengths (∼630

Do buttercups cause photosensitivity?

For example, photosensitive agents are present in St John’s Wort and buttercups (which can also be toxic to horses). A horse may also suffer from photosensitisation, secondary to liver failure. Affected horses will scratch or rub their skin when exposed to sunlight and may develop skin lesions including blisters.

What is the most toxic plant to horses?

Nine poisonous plants horses should avoid

• Ragwort. While ragwort has a bitter taste and is rarely eaten by horses when it is growing, when it is wilted or dried it becomes more palatable.
• Foxglove.
• Deadly nightshade.
• Buttercups.
• Acorns.
• Yew.
• Privet.
• Rhododendron.

What drugs increase sensitivity to sunlight?

There are certain types of medicines that can cause sensitivity to the sun. Some of these include: Antibiotics (ciprofloxacin, doxycycline, levofloxacin, ofloxacin, tetracycline, trimethoprim) Antifungals (flucytosine, griseofulvin, voricanozole)

What causes equine encephalomyelitis?

Eastern equine encephalitis (EEE) is an extremely rare but serious and often fatal infection that causes encephalitis or inflammation of the brain. It is spread by the bite of a mosquito infected with EEE virus (EEEV). EEEV can also infect a wide range of animals including mammals, birds, reptiles, and amphibians.

How do you treat equine encephalomyelitis?

Treatment

1. No vaccine or specific antiviral treatments for EEE are available.
2. Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms.
3. In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.

How do I know if my horse has EIA?

A horse may develop a mild fever or lose its appetite — signs that may go unnoticed. Chronic: Clinical signs of EIA (fever, depression, weight loss, anemia and pinpoint-sized hemorrhages on the mucous membranes) are most likely seen in this phase.