SUMMARYIntestinal parasites are an important cause of morbidity and mortality. Immunocompromised individuals may develop more severe forms of these infections. Taking into account the immunity impairment in patients suffering from chronic renal failure (CRF), we will determine the prevalence and associated symptoms of intestinal parasites in these patients. Controls without CRF were used for comparison. Stool samples were collected and processed for microscopic identification of parasites using the Formalin-ether concentration method. For Cryptosporidium diagnosis, the ELISA technique was used. One hundred and ten fecal samples from hemodialysis patients were analyzed, as well as 86 from a community group used as control group. A result of 51.6% of intestinal parasites was observed in hemodialysis patients and 61.6% in the control group. Cryptosporidium and Blastocystis were the most common infections in patients with CRF (26.4% and 24.5%, respectively). Blastocystis was the most common infection in the control group (41.9%), however no individual was found positive for Cryptosporidium. Among the CRF patients, 73.6% were symptomatic, 54.3% of these tested positive for at least one parasite, in contrast to 44.8% in asymptomatic patients (p = 0.38). The most common symptoms in this group were flatulence (36.4%), asthenia (30.0%) and weight loss (30.0%). In the control group, 91.9% were symptomatic, 60.8% of these tested positive for at least one parasite, in contrast to 71.4% in asymptomatic patients (p = 0.703). A significant difference between the two groups was observed with regard to symptoms, with bloating, postprandial fullness, and abdominal pain being more frequent in the control group than in the hemodialysis group (all p < 0.05). Comparing symptomatic with asymptomatic, there was no association in either group between symptoms or the prevalence of parasitic infection, nor with the type of parasite or with multiple parasitic infections. Patients with chronic renal failure are frequent targets for renal transplantation, which as well as the inherent immunological impairment of the disease itself, results in immunosuppression by medication. For this reason, carriers of intestinal parasites with pathogenic potential can develop serious clinical complications influencing the success of transplantation. This fact, coupled with the high prevalence of intestinal parasites and the dissociation between symptoms and infection in CRF patients, suggests that the stool test should be incorporated in routine propedeutics. Furthermore, preventive measures for the acquisition of parasites through the fecal-oral contamination route should be introduced.

The present study evaluates the prevalence of enteroparasitosis in the urban slums of Belo Horizonte, Brazil and the risk of transmitting enteroparasites to the family members of infected individuals. Stool samples were collected and examined at clinical laboratories near each slum. Individuals were identified and classified as positive for parasitosis (IP z ), and individuals with negative stool tests were classified as negative for parasitosis (IP 2 ) and enrolled as control patients. We collected samples from 594 patients, of which 20.2% and 79.8% were classified as IP z and IP 2 , respectively. In addition, 744 family members (FIPs) effectively participated in the study by providing fecal samples. In total, 1338 participants were evaluated. Of these, 34.6% were tested positive for parasitosis. Blastocystis was the most prevalent parasite, infecting 22.4% of individuals. Among FIPs, the overall prevalence was 46.1%. Of these, 50.6% and 44.7% were classified as FIPs z and FIPs 2 , respectively. These results showed that IP z did not impact the prevalence of infection within the studied communities, not constituting index cases of specific risk behaviors, suggesting that, in fact, these communities are exposed to similar oral-fecal routes of contamination.

The chemotherapeutic agents used for the treatment of giardiasis are often associated with adverse side effects and are refractory cases, due to the development of resistant parasites. Therefore the search for new drugs is required. We have previously reported the giardicidal effects of metronidazole (MTZ) and its analogues (MTZ-Ms, MTZ-Br, MTZ-N(3), and MTZ-I) on the trophozoites of Giardia lamblia. Now we evaluated the activity of some giardicidal MTZ analogues in experimental infections in gerbils and its effects on the morphology and ultrastructural organization of Giardia. The giardicidal activity in experimental infections showed ED(50) values significantly lower for MTZ-I and MTZ-Br when compared to MTZ. Transmission electron microscopy was employed to approach the mechanism(s) of action of MTZ analogues upon the protozoan. MTZ analogues were more active than MTZ in changing significantly the morphology and ultrastructure of the parasite. The analogues affected parasite cell vesicle trafficking, autophagy, and triggered differentiation into cysts. These results coupled with the excellent giardicidal activity and lower toxicity demonstrate that these nitroimidazole derivates may be important therapeutic alternatives for combating giardiasis. In addition, our results suggest a therapeutic advantage in obtaining synthetic metronidazole analogues for screening of activities against other infectious agents.

A new colourimetric method to be used for the screening of compounds with giardicidal activity was developed. After the end of drug incubation, the remaining viable cells were fixed with methanol and stained by methylene blue. The inclusion of methylene blue by Guardia lamblia trophozoites was measured spectrophotometrically to determine the anti-giardial activity of metronidazole. The 50% inhibitory concentration (IC(50)) was 1.96 +/- 0.13 microM. The reliability of this method was assessed by comparison with the IC(50) obtained using a haemocytometer to get the number of viable cells (1.82 +/- 0.43 microM). This method provides a feasible, cheap and reliable method to determine the anti-giardial activity of drugs.