Hepatogenous photosensitivity outbreak after coccidiosis in grazing Holstein steers

Authors: Nieman, Christine; SCHAEFER, DANIEL - University Of Wisconsin; MARONEY, MICHAEL - University Of Wisconsin; NELSON, KATHRYN - University Of Wisconsin; ALBRECHT, KENNETH - University Of Wisconsin

Submitted to: Veterinary Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2020
Publication Date: 11/24/2020
Citation: Nieman, C.C., Schaefer, D.M., Maroney, M., Nelson, K., Albrecht, K.A. 2020. Hepatogenous photosensitivity outbreak after coccidiosis in grazing Holstein steers. Veterinary Sciences. 7(4):186. https://doi.org/10.3390/vetsci7040186.
DOI: https://doi.org/10.3390/vetsci7040186

Interpretive Summary: This case report was created to share observations of an outbreak of photosensitivity that occurred in grazing Holstein steers in summer of 2015. Holstein calves, approximately 500 lbs, developed clinical signs of photosensitivity ranging from mild irritation/redness of the skin on the muzzle, to sloughing of unpigmented hide. In this case, photosensitivity was considered "secondary photosensitivity", in which previous damage to the liver prevented the removal of photodynamic agents from the blood stream. The liver damage was believed to be caused by a previous coccidosis outbreak that resulted in diarrhea and anorexia. Despite the sudden onset and severity, other than removing calves with severe cases from pasture into the shade in confinement, calves were not treated for photosensitivity. Calves appeared to be healthy with normal eating behavior and good body condition. Calves did not have elevated temperatures, photosensitive areas were not sensitive to touch, and newly regenerated skin was developed under the hide. In this case, clinical signs appeared suddenly and severely in some caes, however, cattle recovered without treatment, and there was no incidence of mortality associated with photosensitivity.

Technical Abstract: Clinical signs of photosensitivity in cattle can occur sporadically and unpredictably. It is believed that cases of photosensitivity may be underreported, causing inaccurate and inflated reports of mortality. Additionally, because secondary photosensitization in grazing cattle occurs when liver damage or dysfunction, photosensitivity can have many potential or associated causes. This case links a previous incidence of coccidiosis to an outbreak of photosensitivity in grazing Holstein steers. Grazing management staff first observed clinical signs of photosensitivity 17 days after an outbreak of coccidiosis and subsequent turnout to spring pastures. Clinical signs were observed in 25% of population. The severity of photosensitivity was variable and ranged from blistered skin on the muzzle to sloughing of unpigmented hair and epidermis. Severely affected cattle were removed from pasture, housed under shade, monitored for infection, and recovered without treatment. Mild cases remained on pasture and recovered without treatment. Photosensitivity did not reoccur in the cattle that remained on pasture or in moderately affected cattle returned to pasture. Photosensitivity did not appear to be associated with pasture weeds, a specific forage species, or variable or extreme weather conditions. The occurrence appears to have been a result of a previous and concurrent coccidiosis outbreak that caused secondary photosensitization through hepatic lipidosis caused by anorexia and dehydration associated with the severe coccidiosis. Although clinical signs appeared suddenly, cattle recovered quickly and without treatment.