31 August 2001

Separation vital to clear mange mites from herd

By Hannah Velten

INTERESTED in eradicating mange mites from your pig herd?

It is achievable, in fact many producers are already halfway there with routine treatments, but segregation of clean and dirty pigs is often neglected so reinfection occurs.

That is the view of pig vet David Chennells, who organised a mange eradication programme in a south-east midlands-based pedigree breeding and multiplication herd. The business operates two, 250-sow, continuous-flow indoor breeding to finishing units.

The herd has now been mange-free for 18 months and the business has increased breeding pig sales, thanks to the units improved health status. "In commercial units, eradicating mange also leads to higher carcass revenues as there are fewer blemishes on the skin, so carcasses need less trimming," says Mr Chennells.

"Pigs are also more content, as they are not itchy, feed intakes are optimised and there is less damage to buildings and equipment, as pigs are not rubbing themselves."

Most commercial herds have mange mites, but routinely use injectables or pour-on treatments on sows before they farrow. "The idea is that clean sows produce clean piglets. But there is always the odd sow or boar who continue to carry the mite and reinfect the herd," says Mr Chennells.

The two units in question were already using injectable doramectin (Dectomax). Sows were treated before farrowing and boars twice a year.

"But six months before the main eradication began heavily infested sows and boars were treated every three months and severely infested stock every six weeks."

A successful eradication programme requires planning, capital outlay and labour, warns Mr Chennells. "All breeding sows and boars were treated with doramectin on the same day, moved into clean accommodation and treated again 14 days later, so the units had to be adequately staffed.

"Because some sows were likely to farrow within the 14-day interval, they received their first injection out of synch with the other sows. After weaning, these sows had to be kept separate from the rest of the breeding herd until after their second injection. Any piglets weaned during the programme were also injected once at weaning."

Gilts and potential breeding stock were also treated. All hospitalised pigs were sold as slaughter pigs, regardless of their genetic potential.

Mr Chennells advised the unit to use two injections as a precaution against poor injection technique or thick mange lesions stopping active ingredients reaching the bloodstream.

He estimates that the injection programme used one years worth of doramectin in three weeks at an average cost of £6 a pig. "Although this is an expensive procedure in the short-term, a mange-free herd requires no routine treatments."

But the unit cannot be fully stocked during the programme, says Mr Chennells. "There must be the opportunity to separate clean and dirty stock so there is no chance of reinfection. Buildings need to be cleaned and sprayed with an acaracide, to kill remaining mites, dried and rested for 10-14 days before clean pigs can be moved into them."

April to June is the ideal time of the year to eradicate mange on most units, as buildings dry out rapidly and most units are fully staffed, he says.

"Units need to be out of production for at least two weeks so there is adequate housing. This means planning ahead by talking to marketing groups to see when more pigs can be sold or if they can be sold at a lighter weight."

Alternatively, an outdoor paddock could be set up for dirty stock or a grain storage building used as temporary housing.

Mr Chennells believes the greatest risk of reinfection is movement of staff between dirty and clean areas, so stringent bio-security controls must be established. "The eradication programme is a waste of time unless staff are either designated to only work in one area or change their work clothes and boots before moving between areas." Staff on the units had to wear green overalls in clean areas and red overalls in dirty areas.

Once mange-free progeny – born to treated sows – began to come through the system they were given one precautionary injection, until repeated ear scrapings proved the herd to be mange-free.

After mange eradication clinical disease has also reduced and performance improved because of cleaning and disinfection in growing and finishing accommodation. &#42

MANGE ERADICATION

&#8226 Possible on indoor units.

&#8226 Strict bio-security protocol.

&#8226 Need spare housing.