Small Ruminants | October 2022
Photosensitivity in sheep Since 2019, multiple cases of photosensitivity in sheep caused by sporidesmin are reported in the Netherlands. Sporidesmin, is liver toxic and is formed by the fungus Pithomyces chartarum, which, is formed by the Pithomyces chartarum, which flourishes on dead plant material. The current drought has resulted in extremely favourable conditions for this mould to be
able to grow. The risk of photosensitivity occurring will certainly increase if the autumn is just as humid as previous years. GD warns sheep farmers and veterinarians to be alert on clinical signs of photosensitivity coming autumn. To confirm the diagnosis, further testing is recommended.
ENTV in a three-year-old ram In 2018, we informed you as follows: A nasal tumour was diagnosed in a sheep submitted for pathological examination. Nasal tumours (adenocarcinoma) in sheep may be caused by a virus. In order to determine whether this was the case, samples of the tumour were sent to the Moredun Research Institute in Scotland for further examination. This examination showed that the tumour was indeed caused by a virus; further investigation of this virus was initiated. The farm was visited in order to inspect the animals. According to the farmer, another animal had previously presented the same clinical signs. Such tumours are generally not found in animals younger than two years. In a flock presenting this problem, generally not many animals are affected. As the disease has a viral source, and can spread via contaminated aerosols, measures need to be taken in order to prevent spread further spreading. During the farm visit by GD, the sheep farmer indicated that the sheep had been born at the farm in 2016. Rams had been imported from Germany in 2015. He also informed us that another sheep born in 2016 had already died in 2018, and that he could not exclude that the animal had suffered from
the same disease, in hindsight. The flock was inspected during the visit. No suspect animals were seen. It was agreed that the farmer would contact GD if any abnormalities became visible in the flock. GD also advised avoiding any contact with other sheep, and not selling any live animals. In 2018, there were no reliable tests available for screening of this virus in live sheep.” A veterinarian recently contacted the Veekijker regarding a ram suspected to have a nasal tumour. The animal had been repeatedly treated with antibiotics, and when that did not solve the problem, it was decided to submit the ram for pathological examination. A tumour was indeed diagnosed in the ethmoid bone. Due to the possibility of a viral background, a tissue sample was submitted to the Moredun Research Institution for confirmation purposes, where the suspicion of an infection with the enzootic nasal tumour virus (ENTV) was indeed confirmed. A GD veterinarian then visited the farm. On discussing the situation, there was no clear source of the infection. The ram had been born at the farm and this
farm does not import any animals. The farm does however regularly sell rams for breeding purposes. This type of viral tumour had previously been found in a flock of grazing sheep. There does not seem to be a relationship between the two farms where ENTV was diagnosed. During the farm visit, no clinical signs were observed in the other members of the flock of the ram diagnosed with the tumour. It was agreed that the farmer would contact GD in the event of any new suspected cases. As in 2018, GD also advised avoiding any contact with other sheep, and not selling any live animals. ENTV is not subject to compulsory notification or reporting and as such, the advice given to the sheep farmer is nonobligatory.