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Bulletin No. 15 - Summer 2003
Parasitology- No Category
VERCRUYSSE J, GEURDEN T.
Mange diagnosis.
Pig Progress, June 2003: 7-8
Current antiparasitic treatments are recommended without actually knowing the status of the pigs on a farm. This is due to difficulties in diagnosis, the high cost of laboratory tests compared to the cost of antiparasitic treatment, and the lack of advice on diagnosis in routine parasite control programs. Sarcoptic mange, caused by the Sarcoptes scabiei var suis mite, can be diagnosed as follows: On the farm, the presence of crusts in the ears is often diagnostic of mange, and should be confirmed by ear scrapings of growing pigs. High levels of pruritus (a scratching index of >0.4 scratching incidents per fattening pig per quarter hour) are suggestive of mange, but lack specificity and sensitivity. Conclusive diagnosis requires a finding of mites in ear scrapings. Recently, serological tests (ELISA) have been developed to demonstrate specific antibodies to S. scabiei. There are several considerations when using these tests - Specificity is high, but sensitivity is low in sows. Sensitivity of 60% in currently-available commercial tests is achieved by high cut-off points. These tests are not quantitative, and antibodies may remain detectable for 6-9 months after treatment in chronically infested animals. Young animals may not have developed specific antibodies perhaps due to interference of maternal antibodies. At the slaughterhouse, mange is diagnosed through the examination of carcasses for skin lesions. Dermatitis scores have been shown to have specificity of at least 75-80%. However, in using dermatitis scores diagnostically, it must be remembered that other parasites such as lice, Demodex mites and allergic reactions can also cause dermatitis.
