Limiar de positividade e sensibilidade dos métodos de Faust et al. e Lutz para detecção de cistos de Giardia duodenalis / Positivity threshold and sensitivity of methods of Faust et al. and Lutz for detection of Giardia duodenalis cysts

Objetivo: O presente estudo teve como objetivo determinar e comparar o limiar de positividade e a sensibilidade dos métodos de centrífugo-flutuação em sulfato de zinco (Faust et al.) e sedimentação espontânea (Lutz) para o diagnóstico de cistos de Giardia duodenalis. Métodos: Para obtenção de amostras fecais com quantidades conhecidas de cistos de G. duodenalis, amostras positivas para o parasito foram purificadas e quantificadas, e posteriormente alíquotas com diferentes quantidades foram adicionadas a amostras fecais negativas para parasitos. Após a contaminação de oito amostras negativas com quantidades variando entre 1.000 e 200.000 cistos por grama de fezes (c/g/f), as mesmas foram submetidas aos métodos de Faust et al. e Lutz, onde o primeiro se mostrou mais sensível para a detecção de cistos de G. duodenalis. Resultados: O limiar de positividade do método de Faust et al. foi de 11.000 c/g/f, e do método de Lutz foi de 100.000 c/g/f, portanto, cargas parasitárias inferiores a esses limiares levariam a resultados falso-negativos. Conclusão: O método de Lutz não é adequado para o diagnóstico de giardíase, portanto deve ser sempre utilizado em conjunto com o método de Faust et al.

Objective: The present study aimed to determine and compare the positivity threshold and sensitivity of the methods of zinc sulfate centrifugal flotation (Faust et al.) and spontaneous sedimentation (Lutz) for the diagnosis of Giardia duodenalis. Methods: To obtain fecal samples containing known amounts of G. duodenalis cysts, the samples with the parasite were purified and quantified, then aliquots with different amounts were added to fecal samples negative for parasites. After the contamination of eight negative samples with amounts ranging between 1.000 and 200.000 cysts per gram of feces, they were subjected to methods of Faust et al. and Lutz, where the first was more sensitive for the detection of G. duodenalis cysts. Results: The positivity threshold of the method of Faust et al. was 11.000 c/g/f, and the method of Lutz was 100.000 c/g/f, so parasitic loads below those thresholds would lead to false-negative results. Conclusion: The method of Lutz is not suitable for the diagnosis of giardiasis, therefore must always be associated with the method Faust et al.

Trypanosoma cruzi vector infection rate is underestimated in some localities in the state of Bahia

Bahia was the last Brazilian state declared free of Chagas disease transmission by Triatoma infestans in 2006. The program designed to control vector transmission of Chagas is currently active, and all potential triatomines collected by the Bahia State Department of Health officials are most frequently diagnosed as negative for Trypanosoma cruzi when analyzed by the conventional parasitological direct method. The aim of the current study was to investigate whether triatomines from Bahia are free of T. cruzi infection using a more sensitive diagnostic methodology, namely the kinetoplastid-DNA polymerase chain reaction (kDNA-PCR). With the help of health officials, 51 triatomines were analyzed from peridomicile areas within the central north region of the state of Bahia. The majority (60.8%) were Triatoma brasiliensis, 29.4% were Triatoma pseudomaculata, and 9.8% were unidentified nymphs. Only one insect tested potentially positive for T. cruzi by the conventional parasitological direct method, and 31.4% were positive for T. cruzi DNA by kDNA-PCR. Almost half the infected insects (41.9%) were T. brasiliensis, a species with high potential for T. cruzi transmission. These results demonstrate that the number of infected triatomines with high transmission potential of T. cruzi may be greater than expected in four localities in the state of Bahia

High occurrence of Calodium hepaticum (syn. Capillaria hepatica) spurious infection in a village in the Atlantic Forest of southern Brazil

Calodium hepaticum (syn. Capillaria hepatica) is a nematode of the Capillariidae family that infects rodents and other mammals. In Brazil, human spurious infections of C. hepaticum have been detected in indigenous or rural communities from the Amazon Basin, but not in the southern states of the country. Here, we report the highest occurrence (13.5% of 37 residents) of C. hepaticum human spurious infection detected in Brazil and the first record in a southern region, Guaraqueçaba. The finding is explained by the area being located in the Atlantic Forest of the state of Paraná, surrounded by preserved forests and because the inhabitants consume the meat of wild mammals.