Zinc supplementation has been shown to reduce the incidence and prevalence of diarrhea; however, its anti-diarrheal effect remains only partially understood. There is now growing evidence that zinc can have pathogen-specific protective effects. Giardiasis is a common yet neglected cause of acute-chronic diarrheal illness worldwide which causes disturbances in zinc metabolism of infected children, representing a risk factor for zinc deficiency. How zinc metabolism is compromised by Giardia is not well understood; zinc status could be altered by intestinal malabsorption, organ redistribution or host-pathogen competition. The potential metal-binding properties of Giardia suggest unusual ways that the parasite may interact with its host. Zinc supplementation was recently found to reduce the rate of diarrhea caused by Giardia in children and to upregulate humoral immune response in Giardia-infected mice; in vitro and in vivo, zinc-salts enhanced the activity of bacitracin in a zinc-dose-dependent way, and this was not due to zinc toxicity. These findings reflect biological effect of zinc that may impact significantly public health in endemic areas of infection. In this paper, we shall explore one direction of this complex interaction, discussing recent information regarding zinc status and its possible contribution to the outcome of the encounter between the host and Giardia.

Associations between Giardia lamblia infection and low serum concentrations of zinc have been reported in young children. Interestingly, relatively few studies have examined the effects of different dietary zinc levels on the parasite-infected host. The aims of this study were to compare the growth performance and zinc status in response to varying levels of dietary zinc and to measure the antibody-mediated response of mice during G. lamblia infection. Male CD-1 mice were fed using 1 of 4 experimental diets: adequate-zinc (ZnA), low-zinc (ZnL), high-zinc (ZnH) and supplemented-zinc (ZnS) diet containing 30, 10, 223 and 1383 mg Zn/kg respectively. After a 10 days feeding period, mice were inoculated orally with 5 × 106 G. lamblia trophozoites and were maintained on the assigned diet during the course of infection (30 days). Giardia-free mice fed ZnL diets were able to attain normal growth and antibody-mediated response. Giardia-infected mice fed ZnL and ZnA diets presented a significant growth retardation compared to non-infected controls. Zinc supplementation avoided this weight loss during G. lamblia infection and up-regulated the host’s humoral immune response by improving the production of specific antibodies. Clinical outcomes of zinc supplementation during giardiasis included significant weight gain, higher anti-G. lamblia IgG antibodies and improved serum zinc levels despite the ongoing infection. A maximum growth rate and antibody-mediated response were attained in mice fed ZnH diet. No further increases in body weight, zinc status and humoral immune capacity were noted by feeding higher zinc levels (ZnS) than the ZnH diet. These findings probably reflect biological effect of zinc that could be of public health importance in endemic areas of infection.

The effect of zinc (Zn) supplementation for treating diarrhea in children may vary according to the etiological agent. Since Giardia lamblia (G. lamblia) is an important cause of parasitic diarrheal disease worldwide it was of interest to evaluate the effect of different levels of dietary Zn intake on growth performance, Zn status and immune response during infection. CD1 mice were fed 1 of 4 experimental diets: low Zn (ZnL), adequate Zn (ZnA), supplemented Zn (ZnS1) and highly supplemented Zn (ZnS2) diet containing 10, 30, 223 and 1383 mg Zn/kg respectively. After a 10‐day feeding period, mice were orally inoculated with G. lamblia trophozoites and followed on the assigned diet during the course of infection. Giardia‐free mice fed ZnL or ZnA diet were able to attain normal growth while Giardia‐infected mice presented significant growth retardation and lower serum Zn levels. ZnS1 and ZnS2 diets avoided this weight loss during infection, enhanced the production of anti‐G. lamblia IgG and improved serum Zn levels despite the ongoing infection. Maximum growth rate and antibody mediated response were attained in mice fed ZnS1 diet with no further increases by feeding higher Zn levels (ZnS2). These findings reflect biological effect of Zn that could be of public health importance in endemic areas of infection. (Partially published, Nutrients 2013, 5(9), 3447‐3460) Grant Funding Source: Supported by CONACyT

Zinc is an essential micronutrient influencing growth and affecting the development and integrity of the immune system. It was of interest to evaluate the effect of varying dietary zinc level on host resistance to infection. The parasite Giardia lamblia, which infects millions of people around the world was chosen as a model for the study. CD1 mice (80 male 6–8wk old) were fed ad libitum on either low‐zinc, adequate, supplemented 1 or supplemented 2 diet (12.8, 24.6, 57.9 and 309.3 mg Zn/kg diet respectively). After 10 days on the experimental diets, part of the mice from each group were infected with 5×106 G. lamblia trophozoites. Body weight gain was recorded throughout the study. Serum zinc and IgG levels were measured. In all infected dietary groups, seric zinc levels and body weight gain were reduced in comparison to their uninfected counterparts (P=0.03). However, the effects were more pronounced in the low diet group irrespective of the infection. Within 2 weeks following immunization, the mice in all four dietary groups responded by producing significant levels of specific IgG antibodies. Greater IgG antibody response was observed in the zinc supplemented groups when comapred to the low or adequate ones (P<0.05). It appears that zinc supplementation triggers a higher production of IgG and so suggests that zinc was effective in up‐regulating the host's immune response against this parasite.CONACyT 151287