Effect of giardiasis combined with low-protein diet on intestinal absorption of glucose and electrolytes in gerbils

High-fat diet increases the severity of Giardia infection in association with low-grade inflammation and gut microbiota dysbiosis

Exogenous factors that may influence the pathophysiology of Giardia infection remain incompletely understood. We have investigated the role of dietary fat in the pathogenesis of Giardia infection. Male 3 to 4-week-old C57BL/6 mice were fed either a low fat (LF) or a high fat (HF) diet for 12 days and challenged with G. duodenalis. In infected animals, the trophozoite burden was higher in HF + Giardia mice compared to the LF + Giardia group at day 7 post infection. Fatty acids exerted direct pro-growth effects on Giardia trophozoites. Analysis of disease parameters showed that HF + Giardia mice exhibited more mucosal infiltration by inflammatory cells, decreased villus/crypt ratios, goblet cell hyperplasia, mucus disruption, increased gut motility, and elevated fecal water content compared with LF + Giardia. HF diet-dependent exacerbation of Giardia-induced goblet cell hyperplasia was associated with elevated Atoh1 and Muc2 gene expression. Gut microbiota analysis revealed that the HF diet alone induces a taxonomic shift. HF + Giardia mice exhibited microbiota dysbiosis characterized by an increase of Firmicutes and a decrease of Bacteroidetes and significant changes in α- and β-diversity metrics. Taken together, the findings suggest that a HF diet exacerbates the outcome of Giardia infection. The data demonstrate that elevated dietary fat represents an important exogenous factor promoting the pathophysiology of giardiasis.

Giardia spp. and the Gut Microbiota: Dangerous Liaisons

Alteration of the intestinal microbiome by enteropathogens is commonly associated with gastrointestinal diseases and disorders and has far-reaching consequences for overall health. Significant advances have been made in understanding the role of microbial dysbiosis during intestinal infections, including infection with the protozoan parasite Giardia duodenalis, one of the most prevalent gut protozoa. Altered species composition and diversity, functional changes in the commensal microbiota, and changes to intestinal bacterial biofilm structure have all been demonstrated during the course of Giardia infection and have been implicated in Giardia pathogenesis. Conversely, the gut microbiota has been found to regulate parasite colonization and establishment and plays a critical role in immune modulation during mono and polymicrobial infections. These disruptions to the commensal microbiome may contribute to a number of acute, chronic, and post-infectious clinical manifestations of giardiasis and may account for variations in disease presentation within and between infected populations. This review discusses recent advances in characterizing Giardia-induced bacterial dysbiosis in the gut and the roles of dysbiosis in Giardia pathogenesis.

Extra-intestinal and long term consequences of Giardia duodenalis infections

Giardiasis is the most common waterborne parasitic infection of the human intestine worldwide. The etiological agent, Giardia duodenalis (syn. G. intestinalis, G. lamblia), is a flagellated, binucleated protozoan parasite which infects a wide array of mammalian hosts. Human giardiasis is a true cosmopolitan pathogen, with highest prevalence in developing countries. Giardiasis can present with a broad range of clinical manifestations from asymptomatic, to acute or chronic diarrheal disease associated with abdominal pain and nausea. Most infections are self-limiting, although re-infection and chronic infection can occur. Recent evidence indicating that Giardia may cause chronic post-infectious gastrointestinal complications have made it a topic of intense research. The causes of the post-infectious clinical manifestations due to Giardia, even after complete elimination of the parasite, remain obscure. This review offers a state-of-the-art discussion on the long-term consequences of Giardia infections, from extra-intestinal manifestations, growth and cognitive deficiencies, to post-infectious irritable bowel syndrome. The discussion also sheds light on some of the novel mechanisms recently implicated in the production of these post-infectious manifestations.

Impact of protein malnutrition on histological parameters of experimentally infected animals with Giardia lamblia

Giardiasis is one of the most common parasitic diseases worldwide, and the disease is an important cause of diarrhoea and malabsorption in children and immunosuppressed individuals. However, there is no evidence that characterises malnutrition as an aggravating factor for this disease. We evaluated changes in villi structures to examine the association between malnutrition and Giardia lamblia infection. We used 32 gerbils, divided into 4 groups: Control (CT) and Control Infected (CTIn), which each received a 20% protein diet, Malnourished (MN) and Malnourished Infected (MNIn), which each received a 5% protein diet. Groups CTIn and MNIn were inoculated with 1×10(6) trophozoites of G. lamblia, while the remaining groups were mock infected. Seven days post-infection, all groups were sacrificed, and the proximal portions of the small intestines were collected for the analysis of villus height, mucus area and extent of Giardia infection. Gerbils fed with a low-protein diet had significantly lower body weights. Malnourished infected animals presented significantly increased production of mucus, suggesting a synergism occurs between malnutrition and Giardiasis, potentially to control the adhesion of Giardia in the mucosa. Villus height was significantly lower in group MNIn compared to CTIn. This work suggests that malnutrition contributes to severity of Giardiasis by decreasing the intestinal absorption capacity via shortening of the villi.