Simplifying the phytohaemagglutinin skin-testing technique in studies of avian immunocompetence

1. Researchers involved in ecology and toxicology, as well as many other as pects of avian biology, use phytohaemagglutinin (PHA) skin testing as a mea ns of evaluating the immune status of individuals. 2. Immune function, one measure of individual quality, can be used as a sen sitive, non-lethal variable that may be negatively affected in animals expo sed to degraded, contaminated or otherwise disturbed ecological zones. 3. Typically this test has been applied by challenging one wing web with th e immunostimulant PHA, while the other 'control' wing is injected with phos phate buffered saline (PBS). Injection sites on the wing web are measured b efore and 24 h after injection with PHA or PBS. The immune response is cons idered to be the difference between the two wings. 4, Results from PHA skin tests conducted on 608 birds in seven studies repr esenting passerines, waterfowl, upland game birds and raptors are examined. 5. Numerous advantages to eliminating the PBS injection as the experimental control are: (i) decrease by half, the time required for testing; (ii) dec rease handling-related stress on the birds (proportional to handling time); (iii) reduce the probability of errors at injection time; (iv) spare the o ther wing for different tests or uses (e,g. tuberculin DTH testing); and (v ) decrease the coefficient of variation that is due to measurement inaccura cies. 6, The only disadvantage identified is that hypersensitive individuals (out liers) could be missed, which in this case represents 2 of 608 individuals.