Schistosoma japonicum infection and serum and tissue concentrations of retinol and zinc in pigs

The effects of Schistosoma japonicum infection on the concentrations of zin c in serum, liver, spleen and muscle and on the concentrations of retinol i n serum and liver were studied in 48 pigs. Twenty-four of the pigs were eac h infected by intramuscular inoculation with 2000 cercariae of S. japonicum in medium and the rest were similarly inoculated with parasite-free medium , as controls. On each of weeks 4, 11, 17 and 24 post-inoculation (PI), 12 pigs (six of which were infected) were killed. Tissue samples were collecte d at necropsy. Blood samples were taken prior to infection and at necropsy from all pigs, and bi-weekly from the pigs killed 24 weeks post-infection. In an analysis of variance in which serum retinol was the dependent variabl e, the interaction infection X time was found to be significant (P = 0.009) . The main reason for this significance was that the concentration of retin ol in the sera collected from infected pigs at necropsy at 11 weeks PI was significantly lower than in the control pigs killed at the same time (P = 0 .02). Although, overall, infection led to higher zinc concentrations in the liver (P = 0.04) and spleen tissue (P = 0.01), it had no apparent effect o n liver retinol, muscle zinc or serum zinc. However, among the pigs which w ere tested bi-weekly, serum zinc was consistently lower in the infected pig s than in the controls (P = 0.01). The transient declines seen in the concentrations of retinol and zinc in se ra from the infected pigs were not accompanied by similar changes in the ti ssue concentrations, and may reflect an acute-phase response to infection. Schistosoma japonicum infection in pigs is considered a useful model of S. japonicum infection (and probably also of S. mansoni infection) in humans. Similar effects, if they occur in the human infections, map lead to misclas sification of vitamin-ii and zinc status in endemic populations if this sta tus is based on serum retinol and serum zinc.