Protozoa are eukaryotic microbes that are responsible for several important human diseases. Some protozoa infect the gastrointestinal tract via ingestion and cause diarrheal disease. Most notable among the intestinal protozoa are Entamoeba histolytica, Giardia, and Cryptosporidium. These pathogens can contribute to undernutrition by decreasing the absorption of nutrients and are particularly problematic in undernourished children from resource-poor areas. Another common mode of transmission of pathogenic protozoa is via arthropod vectors. Among the vector-transmitted protozoa, the malaria parasite is the most important. Malaria and other blood-borne protozoan diseases are associated with hypoglycemia and acidosis associated with the anaerobic metabolism of the parasite. Other important protozoan diseases include trichomoniasis, African trypanosomiasis, Chagas disease, leishmaniasis, and toxoplasmosis. In general, our knowledge about protozoan infections and nutrition is rather limited. Most studies show that the decreased immunity associated with undernutrition exacerbates disease pathogenesis.

Nutrition and Protozoan Pathogens of Humans: A Primer

On the possible relationship between AIDS and nutrition

MACROPHAGE ACTIVITY WAS STUDIED IN RATS INFECTED WITH TRYPANOSOMA LEWISI IN THREE PROTOCOL GROUPS: one group was fed complete diet, a second group was given a vitamin B(12)-deficient diet, and a third group was fed a pair-fed control (calorically restricted) diet. Throughout the observational period, in animals fed complete and pairfed diets, marked increases in acid phosphatase levels in peritoneal macrophages were directly related to the degree of parasitemia. Acid phosphatase levels in rats deprived of vitamin B(12) were approximately one third that of animals with an adequate supply of the vitamin. Irrespective of the diets, the infection with T lewisi also elicited increased macrophage phagocytosis of polystyrene latex particles and macrophage spreading. Both of these activities occurred at a much slower rate in the vitamin B(12)-deficient animals.

Interaction of nutrition and infection: macrophage activity in vitamin B12-deficient rats infected with Trypanosoma lewisi.

Nutrition and infection have been interacting in humans for millennia, with undernutrition typically increasing susceptibility and exacerbating pathogenicity of infectious agents. In the past half-century, overnutrition as manifested in obesity has emerged as a definitive risk factor for increased severity and higher mortality in the clinical course of a number of infectious diseases, most recently COVID-19. Detailed clinical management of suboptimal nutritional status is the topic of textbooks of clinical nutrition, but we highlight key elements here. Among these are the interactions of nutritional status with major infectious agents causing diarrhea, pneumonia, parasitism, AIDS, bacterial diseases, and others. We highlight paradoxes such as malnutrition down -modulating the severity of malaria. We highlight the clinical implications addressed in the first 15 chapters of this book that are now facing the global community such as the role of obesity in health. We highlight principles in causal thinking, illustrating the complexity associated with unraveling mechanisms responsible for nutrition-infection interactions and their contribution to the health of persons from every background. Finally, we revisit the classic 1968 World Health Organization (WHO) monograph Interactions of Nutrition and Infection, bringing its timeless messages forward a half-century.

Public Health and Clinical Implications of Nutrition-Infection Interactions

Various kinds of nutrition are required for the appropriate functioning of the immune system. Vitamins are vital nutrients involved in multiple biological reactions. Due to high turnover rates and biological activities, vitamin supplies are essential for the appropriate functioning of immune cells. Moreover, accumulating evidence has revealed that vitamins exhibit specific functions in the control of selected immune cells. Thus, excessive or insufficient intake of vitamins leads to impaired immune responses and consequently results in the development of immune diseases or a high susceptibility to infection. In this article, we focus on the diverse but specific immunologic functions of vitamins in the control of host immune responses and their association with infectious and immune diseases.

Immunity and Nutrition: the Role of Vitamins

A metabolic imbalance technique was employed to study vitamin B(12) deficiency in rats infected with Trypanosoma lewisi. Throughout the observational period, animals on the deficient diet had lowered serum vitamin B(12) levels compared with complete and pair-fed animals. The decline in the level of the vitamin, ten days after the initiation of the experiment, continued progressively until the termination of the study. Body weight gains and food consumption in rats on complete, vitamin B(12)-deficient, or pair-fed diets and inoculated with T lewisi showed significant increase over inoculated controls. The rates of body weight and food consumption in vitamin B(12)-deficient animals were significantly less than that of the adequately fed animals.The indices of lowered resistance to infection in the vitamin B(12)-deficient rats were manifoid. Deficient rats suffered earlier and higher parasitemia followed by persistent infection. The delay in the synthesis of the reproductive inhibiting antibody (ablastin) resulted in prolonged variability in the length of the trypomastigotes. Severe depression in the primary and secondary antibody responses (IgG and IgM) to in vivo immunization of sheep erythrocytes was also observed in the deficient animals. In comparison, the level of IgG antibody decreased approximately one fifth the control values.

Interaction of nutrition and infection: effect of vitamin B12 deficiency on resistance to Trypanosoma lewisi.

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Interaction of nutrition and infection: effect of vitamin B12 deficiency on resistance to Trypanosoma lewisi.