Sheep farmers in Oxfordshire are being warned to be vigilant after the first reported case of blowfly in the county this year.

Farmers in Bicester have reported cases of blowfly - maggots hatched from the eggs of greenbottle flies that eat the flesh of sheep. The county's farmers are being warned to treat their flocks now to prevent the spread of blowfly, which does not affect humans. The news comes just three days after footpaths across the county were reopened after it was felt that the threat of foot and mouth was significantly decreased in the county.

The warning has come from Novartis Animal Healthcare, which runs a nationwide alert service for farmers and manufactures animal health products.

Novartis professional services manager Lynda Maris said it was crucial that farmers act now to prevent further setbacks to their livelihoods.

She said: "Blowfly is the main parasite to affect sheep in the summer and can cause significant economic loss."

Warm but wet weather had created perfect conditions for blowfly to develop. Ms Maris refused to identify the farms currently suffering with outbreaks because of the stigma that could be attached to them.

She added: "Significant damage can occur within just 24 to 36 hours of blowfly eggs being laid. That is why prevention is the best way of dealing with this."

Farmers have been urged to dip entire sheep flocks in chemical dips or use products that can prevent the maggots eating an animal's flesh.