Professional paper
Photosensitization in domestic animals
Dražen Đuričić
orcid.org/0000-0002-8013-2091
; Mount-trade d.o.o., Garešnica, Garešnica, Croatia
Charlotte Stiles
; Faculty of Veterinary Medicine University of Zagreb, Zagreb, Croatia
Abstract
Photosensitivity (photosensitization) is an abnormal, skin and associated dermal tissue reaction that results from direct exposure to sunlight (ultraviolet radiation), following ingestion or contact with secondary reactive plant products accumulated beneath the skin. There are four types of photosensitization. Type I or primary photosensitization occurs when the photodynamic agent is either ingested or absorbed through the skin. The agent enters the systemic circulation in its native form, where it results in skin cell membrane damage after the animal is exposed to ultraviolet light. Examples of primary photosensitizing agents include hypericin from St. John’s wort (Hypericum perforatum) and fagopyrin from buckwheat (Fagopyrum esculentum). Type II photosensitization occurs due to inherited defective functions of the enzymes involved in blood synthesis. The photodynamic metabolites (porphyrin) accumulate in some body tissues, such as bones and teeth (for ex. Bovine congenital erythropoietic protoporphyria). Type III (hepatogenous) or secondary photosensitization is the most common type of photosensitivity reaction seen in domestic animals, which occurs when the liver is unable to excrete phylloerythrin, a metabolite of chlorophyll, from the forage the animal has eaten. Normally, phylloerythrin is secreted into the intestine by the biliary system and excreted through the feces. In Type III photosensitivity, hepatic damage and the biliary transport mechanism prevents the excretion of phylloerythrin, allowing the photodynamic substance to enter the circulatory system and accumulate under the skin. It is important that ingestion of hepatotoxic plants in herbivores is frequently linked to type III photosensitization. Type IV, or idiopathic photosensitivity, occurs following the ingestion of certain plants, such as alfalfa. The reason is obscure or idiopathic. The clinical signs are similar regardless of the cause. Affected animals are photophobic immediately when exposed to sunlight. Lesions appear in white-haired, nonpigmented or hairless areas, such as the nose and udders. Erythema and skin edema develop first. If sunlight exposure is prolonged, lesions may progress to vesicle and bulla formation, serum formation, serum exudative dermatitis, ulceration, scab formation, and skin necrosis. The final stage involves skin sloughing.
Keywords
buckwheat; livestock; photosensitization; porphyrin
Hrčak ID:
295159
URI
Publication date:
1.6.2022.
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