It is the first time since the end of the 1800s that the fly, Oestrus ovis, has been reported in Sweden, according to the National Veterinary Institute (SVA).
Larvae of the parasite were found in sheep on Gotland when a ewe with symptoms was put down and autopsied. When other slaughtered sheep on Gotland were subsequently examined, larvae were found in several adult animals from different parts of the island, indicating that it is widespread. The sheep are infected in late summer, a few weeks after the fly's mating.
"Often, the animals show no symptoms, but sometimes nasal discharge and sneezing are seen. The sheep become restless when the adult flies swarm, which can result in reduced feed intake," says Eva Osterman Lind, parasitologist at the National Veterinary Institute, SVA, in a press release.
It is currently unknown whether the fly, which develops from the larvae, occurs on the mainland, but sheep owners are urged to be extra careful in following quarantine rules for sheep.
The larvae can be treated with the medicine ivermectin.
