Exploring mechanisms of photosensitivity

Authors: Collett MG
Publication: New Zealand Veterinary Journal, Volume 58, Issue 2, pp 110, Apr 2010
Publisher: Taylor and Francis

Animal type: Cattle, General, Sheep
Subject Terms: Disease/defect, Liver/hepatic disease, Mycotoxicosis, Photosensitivity, Poisoning - plant, Toxicology
Article class: Abstract

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Abstract:

The quantitative measurement of phytoporphyrin (=phylloerythrin) in the serum or plasma of photosensitive farm animals is useful in order to categorise the photosensitivity as primary or secondary. Chronic cases of sporidesmin toxicosis, or facial eczema, normally a disease occurring in autumn, can become clinically photosensitive in spring due to the relentlessly progressive cholangiohepatitis that culminates in the retention of phytoporphyrin.
The causes of spring eczema in calves and adult cattle are unknown. In calves, spring eczema appears to be primary. In older cattle, some cases are secondary and others primary; recent cases in Southland confirm the latter. Occasional cases of spring eczema are acute and very severe, and require humane destruction. For unknown reasons, spring eczema in Jersey cattle causes unusually severe ear lesions.
Limited work has shown that rape (Brassica napus) scald in sheep is a primary photosensitivity, while that due to turnips (B. rapa) in cattle is secondary. The search for the cause(s) of spring eczema and the agent(s) responsible for Brassica spp. photosensitivity continues.

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