[A practical immunologic skin test for piglets]

At present immune system performance in pigs is decreasing, particularly as a result of environment quality deterioration. Immunological skin tests can also be used to determine the degree of immune system impairment in piglets. A practical immunological skin test was carried out in 48 weaned piglets with the body weight of 15-30 kg. The test was located on the piglets' backs after bristles had been shaved off. The test consists in intradermal injections of a physiological saline (900 micrograms NaCl in 0.1 ml), histamine (100 micrograms in 0.1 ml) and phytohaemagglutinin (0.1 ml; Institute of Sera and Vaccines, Praha). The size of the papule (in 20 minutes) and the size of the induration (in 24 hours) were measured in two perpendicular directions, and the mean value (in mm) was calculated from the measured data. In 20 minutes the average size of the papule was 9.4 mm after the application of the physiological saline and 20.5 mm after histamine application (Fig. 1). In 24 hours after phytohaemagglutinin application the average size of the induration was 15.9 mm (Fig. 2). In twenty minutes the increased reaction to histamine (the papule larger than 24 mm) was observed in four piglets (8.3%); these piglets show the predisposition to allergic diseases (Fig. 3). In another four piglets (8.3%) the decreased reaction to phytohaemagglutinin (endurance of 13 mm and less) was observed in 24 hours; these are piglets with the decreased cellular immunity (Fig. 4). The increased reaction to histamine and the decreased reaction to phytohaemagglutinin were found only in one (2.1%). Piglets with abnormal dermal reaction can represent the risky part of the pig subpopulation which adapt themselves less easily to the stress on large pig farms. A veterinary surgeon and his assistant can examine by this test 20 piglets in the herd. This skin test was recommended as a practical cheap screening test for use in pig herds to evaluate preliminarily the predisposition to allergic diseases and cellular immunity of piglets.