Producers bringing away-wintered sheep back to the home farm should take care to ensure sheep scab and lice aren’t brought back with them.
Loose wool, severe scratching, weight loss and loss of appetite are all classical symptoms of ectoparasites like sheep scab mites and lice and can have significant welfare, production and financial implications, says independent vet consultant, Tony Andrews.
“Within two weeks lice or mites could have spread through an entire flock, so it is important to catch them early and treat effectively. And with the stress of bringing animals together for housing lowering the immune status of some animals and increased contact enhancing spread, the problem could have significant effects,” he says.
Mr Andrews says in a worst case scenario death can occur for sheep infested with mites. And with it only taking about two weeks for the mite to go through its life-cycle, producers must act quickly and treat for the correct ectoparasite.
However, with the only combined treatment for scab and lice being an organophospate dip, which is not viable for use in pregnant ewes, farmers must find the exact problem, says independent consultant Peter Bates.
“It’s crucial, if farmers are seeing ewes itching vigorously, to get the vet out to identify the problem. It is cheaper to pay for a vet visit than it is to treat for lice and to later find the problem is scab.”
Mr Bates says not only are there financial and health benefits in administering the correct treatment, but only treating infected animals means there is less chance of worm resistance if using an endectocide.
“A risk assessment must be taken of the situation. When there are no symptoms then it’s likely treatment won’t be necessary, unless you suspect your stock may have come in to contact with infected sheep.
“If you know your neighbouring farm has a scab or lice problem and your sheep may have come in to contact – whether by common grazing, breaks in fences, stray sheep or by rams used at tupping, then don’t wait to get it, just treat for it,” he says.
“If you wait and don’t treat infected animals there’s a chance the ewe would have invested more energy in fighting the parasite than in her lamb. This too has financial consequences because, if lambs are born small because they haven’t received enough nutrients, it will cost more money to finish them,” he says.
Identifying lice as the problem is a differential diagnosis for sheep scab, says Mr Bates. “Lice are usually a problem on animals in poor condition with a score less than three, but it’s unsure whether the lice cause the loss of condition or whether they take advantage of the weak animals, indicating underlying problems such as liver fluke.”
For treatment of lice in pregnant ewes, Mr Bates recommends a pour-on pyrethroid. “Although there is some resistance to certain pyrethroids it is a case of trial and error.”
For scab treatment, although dipping would be the best option in non pregnant animals offering up to 20 weeks’ protection, in pregnant ewes an injectable endectocide like ivomectin and moxydectin is best. But Mr Bates says producers should be aware injections only guarantee 28 days’ protection.