(17) - Large Animal Photosensitivity

Question 1

1. Photosensitivity is associated with substances that absorb energy from ultraviolet light and transfer it to body cells.
2. Although photosensitized animals seldom die, appreciable economic losses can be associated with photosensitivity.
3. The substances causing photosensitization can be ingested, injected or acquired via contact with the skin

Answer 1

d

Question 2

1. Primary photosensitization occurs when the preformed or metabolically produced photodynamic agent does what?

Answer 2

1. reaches the skin by ingestion, injection, or contact.

Question 3

1. Hepatogenous photosensitization is associated with chronic, severe liver disease and resultant high levels of what?
2. Hepatic disease may occur secondary to the ingestion of hepatotoxic plants or the ingestion of the hepatotoxin, sporidesmin, produced by the fungus Pithomyces chartarum which grows on pasture, especially rye grass during summer and fall.
3. What is the most common form of photosensitization in large animals?

Answer 3

1. phylloerythrin (derived from chlorophyll) in the skin.

3. Hepatogenous photosensitization

Question 4

1. Congenital photosensitization is caused by what?
2. Bovine congenital porphyria is a form of congenital photosensitization characterized by reddish brown discoloration of the teeth and bones (fluoresce with Wood’s light) and photodermatitis due to what?
3. It is autosomal recessive and is associated with the presence of what in the blood, urine and feces?
4. Bovine congenital protoporphyria is characterized by what in young calves?
5. It is autosomal recessive and is associated with increased levels of protoporphyrin in the blood and tissues.
6. Do teeth and bones fluoresce under wood’s light?

Answer 4

1. aberrant pigment synthesis (porphyrin or heme).
2. accumulation of porphyrins in the tissue.
3. uroporphyrin I and coproporphyrin I
4. extreme photosensitization and photophobia
5. no

Question 5

1. Lesions are often restricted to what areas? but, in severe cases, may extend into the surrounding dark-skinned areas as well.
2. The eyelids, lips, face, ears, perineum, and coronary band region are commonly involved
3. There is usually an acute onset of erythema, edema, and variable degrees of pruritus and/or pain often progressing to oozing, necrosis, slough, and ulceration.
4. Photodermatitis confined to the distal extremities, muzzle, and ventrum is strongly suggestive of what?

Answer 5

1. light-skinned, sparsely haired (but, in severe cases, may extend into the surrounding dark-skinned areas as well.)
2. photocontact reactions induced by pasture plants, environmental sprays, or topical medicaments.

Question 6

1. Diagnosis of photosensitization is based on history, physical examination, liver profile or liver function tests, porphyrin studies, and skin biopsies.
2. Liver function tests should be performed on all animals with photosensitization, whether they are
   showing clinical signs of liver disease or not.
3. The number of animals at risk compared with the number of animals affected helps to determine
   what?
4. The distribution of the photodermatitis aids in determining what?

Answer 6

3. whether the photodermatitis is photosensitive (many animals affected) or photoallergic (one animal affected).
4. whether the photodynamic agent is systemic or contactant.

Question 7

1. avoid sunlight
2. Stop the intake of photosensitizer or hepatotoxin.
3. Systemic therapy for hepatic disease and other extracutaneous disorders
4. The photodermatitis may be ameliorated with what?
5. Systemic antibiotics may be required if what is present?
6. What may be indicated if necrosis and sloughing are severe?

Answer 7

4. systemic glucocorticoids ad nonsteroidal anti-inflammatory agents
5. secondary pyoderma
6. Surgical debridement

Question 8

1. In general, the prognosis is favorable for primary photosensitization but poor for What?

Answer 8

1. hepatogenous photosensitization and porphyria.