We recently received details of a case involving beef cattle who were suspected to have ingested native hogweed (Heracleum sphondylium) and rough chervil (Chaerophyllum temulum). The vet in charge of the case was able to provide images of the plant matter, and as confirmed by our botanist, these species were identified.

The cattle presented with skin inflammation, dorsal alopecia, and photosensitivity. It was suspected that the hogweed was causative of the signs seen; however, rough chervil contains a volatile alkaloid which is known to cause dermal injury to livestock.

Ingestion of hogweed can cause dermal effects, but in most cases phototoxicity is due to actual contact with plant material. Skin reactions occur from contact with the plant in combination with exposure to long-wave ultraviolet light.  Skin damage can result from any activity that involves bruising, cutting, damaging or only touching the psoralen-containing plants in combination with exposure to ultraviolet light. In cases of skin contact with minimal or no damage to the plant, moisture such as dew may be a factor in the phytophototoxic reaction.

Mildly elevated liver enzymes have been reported in equines affected by hogweed, so it was suggested that this be monitored in this case.

There is no antidotal treatment for these species and treatment is largely supportive.  The affected cows should be kept out of sunlight for at least 48 hours post exposure.  Treatment involves analgesia, topical/systemic steroids to manage inflammation as required and antibiotics for any secondary infection.  Hyperpigmentation does not require treatment but affected areas may remain sensitive to sunlight for several months or years, so the continued use of sunblock is advised.

As these are beef cattle, there are potential implications to the food chain and we recommended that this case was discussed with a contact at the Animal and Plant Health Agency.