Interactive effects of protein nutrition, genetic growth potential and Heligmosomoides bakeri infection pressure on resilience and resistance in mice

Effects of Cashew Nut (Anacardium occidentale L.) Seed Flour in Moderately Malnourished Children: Randomized Clinical Trial

The monitoring and combined use of dietary supplements to restore adequate growth are paramount and highly recommended in child malnutrition, an important public health problem. The objective of this study was to analyze the effects of cashew nut seed flour in children with moderate malnutrition, treated at primary healthcare services. This is a randomized clinical trial conducted from April to October 2017 in the city of Imperatriz, Brazil. The sample comprised 30 children born at term, aged between 2 and 5 years, and newly diagnosed with malnutrition (60 days or less), randomized into experimental and control groups. The intervention consisted of daily intake of cashew nut seed flour. There was intragroup statistically significant difference in the glucose levels of children who were assigned to the control group (p=0.02) and in the glycated hemoglobin in the experimental group (p < 0.01). Intergroup analysis of glycated hemoglobin levels showed statistically significant differences in favor of the experimental group (p=0.01). HDL and LDL had, respectively, increased and decreased in the experimental group. The use of cashew nut seed flour in a 24-week period had positive effects on glycated hemoglobin, HDL, and LDL parameters in moderately malnourished children.

Resistance and tolerance to mixed nematode infections in chicken genotypes with extremely different growth rates

Fast growing broilers are less able to cope with fitness related challenges. As the allocation of metabolic resources may be traded off between performance and defence functions in parasitized hosts, we hypothesized that fast growing broilers are more sensitive to mixed nematode infections compared with slower growing genotypes under the same environmental conditions. Therefore, we compared male birds of genotypes selected for either meat production (Ross-308, R) or egg production (Lohmann Brown Plus, LB) or for both purposes (Lohmann Dual, LD), to assess their resistance and tolerance to mixed nematode infections with Ascaridia galli and Heterakis gallinarum. While infections reduced feed intake in all three genotypes, feed conversion efficiency was not affected. Infections impaired growth performance only in R birds, indicating lower tolerance in the fast growing genotype compared with slower growing LB and LD genotypes. Impaired tolerance in R birds was associated with a relative nutrient scarcity due to an infection-induced lower feed intake. Resistance to experimentally induced infections depended on host genotype as well as on the worm species involved. Overall, the A. galli burden was higher in R than LB, whereas the burden of LD was not different from that of R and LB. In contrast, the H. gallinarum burden of first generation worms was similar in the three genotypes. Susceptibility to re-infection with H. gallinarum was higher in LB than in LD, whereas very low levels of re-infection were observed in R birds. Our data collectively suggest that resistance and tolerance to mixed nematode infections are sensitive to growth rate in chickens. These differences amongst genotypes may partly be associated with a mismatch between the actual nutrient supply and genotype-specific nutrient requirements.

Does selection for growth rate in broilers affect their resistance and tolerance to Eimeria maxima?

Chickens exhibit varied responses to infection with Eimeria parasites. We hypothesise that broilers selected for increased growth rate will show lower resistance and tolerance to a coccidian challenge. 288 chickens of fast (F) or slow (S) growing lines were inoculated with 0 (control), 2500 (low-dose), or 7000 (high-dose) sporulated E. maxima oocysts at 13 days of age in two consecutive rounds. Gain and Intake were measured daily and their values relative to BW at the point of infection were calculated over the pre-patent (days 1-4 post-infection), acute (d5-8 pi), and recovery (d9-12 pi) phases of infection to assess the impact of infection. Levels of plasma carotenoids, vitamins E and A, long bone mineralisation, caecal microbiota diversity indices, and histological measurements were assessed at the acute (d6 pi) and recovery stage (d13 pi). In addition, we measured the levels of nitric oxide metabolites and the number of parasite genome copies in the jejunumat d6pi. In absolute terms F birds grew 1.42 times faster than S birds when not infected. Infection significantly reduced relative daily gain and intake (P < 0.001), with the effects being most pronounced during the acute phase (P < 0.001). Levels of all metabolites were significantly decreased, apart from NO which increased (P < 0.001) in response to infection on d6pi, and were accompanied by changes in histomorphometric features and the presence of E. maxima genome copies in infected birds, which persisted to d13pi. Furthermore, infection reduced tibia and femur mineralisation, which also persisted to d13pi. Reductions in measured variables were mostly independent of dose size, as was the level of parasite replication. The impact of infection was similar for S and F-line birds for all measured parameters, and there were no significant interactions between line x dose size on any of these parameters. In conclusion, our results suggest that line differences in productive performance do not influence host responses to coccidiosis when offered nutrient adequate diets.

Effects of protein malnutrition on tolerance to helminth infection

Infection tolerance is the ability of a host to limit the health effects of a given parasite load. A few recent studies have demonstrated genetic variation for tolerance, but little is known about how environmental factors affect tolerance. Here, we used the intestinal nematode Heligmosomoides polygyrus in laboratory mice to test for effects of protein malnutrition on tolerance. We performed an experiment where two different mouse strains (CBA and BALB/c) were fed either adequate-protein food or low-protein food, and trickle-infected with different doses of H. polygyrus larvae during four weeks. We found that protein malnutrition decreases tolerance measured as intestinal barrier function, but only in one of the strains (BALB/c); that is, there was a host genotype-by-environment interaction for tolerance. We conclude that nutritional status can affect tolerance and that sensitivity of tolerance to malnutrition may differ between host genotypes.

Evaluation of biochemical, hematological and parasitological parameters of protein-deficient hamsters infected with Ancylostoma ceylanicum

BACKGROUND

Hookworms infect millions of people worldwide and can cause severe clinical symptoms in their hosts. Prospective cohort studies in Brazil show high rates of hookworm reinfection in malnourished children compared to well-nourished children, despite previous treatment. Additionally, soil-transmitted helminth (STH) infections can worsen the nutritional status of affected populations. Therefore, this study aims to clarify the effects of host malnutrition during Ancylostoma ceylanicum infection and how this infection affects host physiological parameters using a hamster model.

METHODOLOGY/PRINCIPAL FINDINGS

Hamsters were divided into four experimental groups: normal diet or low-protein diet (also referred to as "malnourished") and A. ceylanicum infection or no infection. More severe pathogenesis was observed in the infected malnourished group, as demonstrated by significant decreases in the hemoglobin concentration, erythrocyte number and packed-cell volume compared to the non-infected malnourished group. Greater numbers of adult parasites and eggs were observed in the malnourished group compared to the control group; however, the oviposition rate was lower in the malnourished group. In general, greater values of total lipids were observed in malnourished animals compared to control animals, including lipids excreted in the stool.

CONCLUSIONS

In this work, we have demonstrated that animals fed an isocaloric low-protein diet presented more severe pathogenesis when infected with A. ceylanicum. The increased lipid concentration in the liver and blood is related to the conversion of the excess carbohydrate into fatty acids that increase the concentration of triglycerides in general. Triglycerides were excreted in the feces, indicating that infection associated with malnutrition caused a greater loss of these molecules for this group of animals and confirming the hypothesis that both nutrition and infection are responsible for the malabsorption syndrome. Taken together, the results found in this work confirm the hypothesis that the nutritional condition of the host greatly influences the course of the infection.