RESUMEN
The role of zinc (Zn) in the immunological expulsion of the nematode Nippostrongylus brasiliensis (Nb) from the small intestine of the rat was investigated. Three groups of 28 rats each were fed a basal diet providing either 3 mg Zn/kg for the zinc-deficient group (-Zn) or 40 mg Zn/kg for ad libitum-fed and pair-fed controls. After 6 wk each group was divided into two equal subgroups and infected with either 1000 or 4000 infective Nb larvae/rat. The -Zn rats showed significant reductions (P less than 0.001) in food intake, weight gain and food conversion efficiency when compared to the rats fed ad libitum but not when compared to the pair-fed controls. Plasma zinc concentration in the -Zn rats (0.50 microgram/ml) was significantly lower than in both ad libitum-fed (1.33 micrograms/ml) and pair-fed (1.45 micrograms/ml) controls (P less than 0.001). The recovery of worms from the rats 3, 7 and 12 d postinfection was similar for the corresponding day and dose of infection in all groups. Expulsion was almost complete in all groups by 12 d post-infection. There were no significant differences in size and fecundity of worms recovered from the different groups of rats on 7 d postinfection. However, over the whole period of infection, the -Zn rats excreted significantly more parasite eggs than did controls (P less than 0.001). These results indicate that although zinc deficiency affected growth performance of the rats, it did not affect the establishment or expulsion of Nb. Impairment of the immune response of the zinc-deficient rat was manifested only by a significant increase in the number of parasite eggs excreted in feces.