Age affected: Piglets pre-weaning.
Causes: Fighting wounds; bacterial infection.
Effects: Infected wounds on face.
Facial dermatitis in piglets is caused by fighting which leaves scars and scratches on the face. These are subsequently colonised by bacteria such as Staphylococcus hyicus, the cause of greasy pig disease. The fighting is part of the natural establishment of teat order and occurs after pigs are born. In the first week of life, fighting may be more apparent if they are part of a large litter, or if there is interruption in the supply of milk as a result of mastitis or agalactia.
Fighting may reccur if there is disease in the litter, leading to displacement of one of the higher-ranking piglets, or if the gland supplying the high-ranking piglet become less attractive. The lesions are caused by the canine teeth and consist of shallow scratches which become infected. In severe cases, they may lead to widespread scab formation and act as a focus for the initiation of greasy pig disease (exudative epidermitis).
The condition is not transmissible, but does develop repeatedly when the conditions under which it arises persist. Key to its occurrence is the supply of milk to each piglet, and this is governed in part by teat numbers and the number of piglets in the litter. The severity of the lesions and their persistence does, however, depend upon the bacteria present in the herd, so the presence of S. hyicus and other bacteria such as Treponema pedis which colonise skin lesions may allow certain features of the condition to be passed from piglet to piglet.
The condition becomes apparent within the first week of life, initially as scratches and later as spreading brownish scabs which may become blackish if extensive or seriously infected. They may be sufficiently severe to obscure the eyes or the corner of the mouth and the infection may subsequently spread all over the skin in exudative epidermitis. Piglets in litters where facial dermatitis is occurring may weigh up to 0.5 kg less than piglets with clipped teeth at weaning.
Scratches are usually visible and fighting may be seen. In late and severely infected cases, the thick brown or blackish scabs may have to be distinguished from milk encrusted with dirt around the mouth which is easily removed, infection and abscessation following faulty tooth clipping, or the early stage of greasy pig disease. In greasy pig disease, lesions resembling brown flakes are found in the armpits and groin and not just on the face. The organisms involved may be identified by removing a scab and sampling the underside. S hyicus is the most common organism involved, but deep or severe lesions may contain streptococci and anaerobes including fusobacteria and spirochaetes.
The lesions of facial dermatitis can be seen and recorded at the post-mortem examination of piglets, but specific examination of them is unusual. When investigated in the laboratory, there is local skin damage, inflammation and crusting of the surface of the surface of the wounds which often contains clumps of bacteria.
Treatment of the infections is possible using penicillin, ampicillin, amoxicillin, lincomycin or tylosin given orally in piglet dosers or by injection. The scabs can be bathed in a skin disinfectant such as cetrimide or chlorhexidine. The condition can be prevented by carefully clipping the teeth of all litters within 24 hours of birth where this is allowed. Removing underlying causes such as overcrowding by fostering piglets from large litters, or rearing them artificially to leave one animal per functioning teat, and prompt treatment of agalactia may also reduce fighting and reduce facial dermatitis.