The recent incursion of foot-and-mouth disease (FMD) in Indonesia has heightened awareness of the importance of reporting livestock with concerning clinical signs. In this case the owner of a small herd of cows on the Central Tablelands of NSW called the Emergency Animal Disease (EAD) Hotline to report skin lesions that looked like blisters on the nose, feet and teats of one of 40 cows. Tests were negative for vesicular diseases, including FMD, and photosensitisation was diagnosed.
On 11 November 2022, the owner of a herd of 40 Simmental cows with calves at foot and 48 young, weaned cattle, called the EAD Hotline as he was concerned that one cow had blisters on the nose and lesions on feet and teats. The property was visited as soon as practical after the call. The property had mixed improved and native pastures on the Central Tablelands of NSW. The owner reported that there had been no recent introductions of cattle, no overseas visitors and that he and his wife had not travelled overseas in the last few years. The owner reported occasional incursions of feral pigs and some St. John's wort (Hypericum perforatum) in the pastures.
The affected cow was a mature Simmental in fat score 2.5 with a 2-3 week-old calf at foot. The cow was bright and alert and not febrile. She had erosions on the nasal planum and dry peeling skin on the nose with only unpigmented areas affected. She had a dry crusty dermatitis of the unpigmented parts of the distal limbs and all teats, including the supernumerary teats, were dark red with loss of the skin surface. She had a 10 cm diameter dry crusty patch of dermatitis on the pigmented skin on the dorsum of the left shoulder. She had no lesions on the ventral half of the nasal planum, the gingiva or the tongue.
Four more cattle were examined in the yards and the mob of 48 weaned cattle were examined in the paddock. No clinically affected animals were seen.
Given that only the unpigmented skin of the cow was affected, photosensitisation was provisionally diagnosed but blood samples and a swab from the nasal lesions were collected to exclude hepatopathy, FMD and vesicular stomatitis virus (VSV).
A range of tests conducted at Elizabeth Macarthur Agricultural Institute, Menangle and at the Australian Centre for Disease Preparedness at Geelong were negative for FMD and VSV.
Blood tests indicated that the cow was suffering from at least mild liver disease. The farmer also commented that as the season progressed, he observed more St. John's wort in the paddock. Both the St. John's wort and concurrent liver disease were presumed to have contributed to the photosensitisation. The owner reported that the cow recovered and no other animals were affected.