Strongyloidiasis in humans: diagnostic efficacy of four conventional methods and real-time polymerase chain reaction

Abstract INTRODUCTION: Strongyloides stercoralis is an intestinal parasitic nematode that causes hyperinfection and/or a dissemination syndrome in hosts, which is often difficult to diagnose. This study aims to compare the diagnostic efficacy of four conventional methods used to diagnose strongyloidiasis with real-time polymerase chain reaction (qPCR) to detect S. stercoralis in fecal samples. METHODS: We analyzed 143 fecal samples collected from Colombian regions with varying degrees of risk for intestinal infections caused by S. stercoralis to assess the validity, performance, overall efficiency, and concordance of the qPCR using a direct stool test, modified Ritchie concentration technique, agar plate culture, and Harada-Mori technique as reference tests. RESULTS While four fecal samples were positive for S. stercoralis using conventional methods, 32 were positive via qPCR. The diagnostic sensitivity of the qPCR was 75% [95% confidence interval (CI): 20.07-100%], whereas its specificity, negative predictive value, negative likelihood ratio, and Youden's J index were 78.42% (95% CI: 71.22-85.62%), 99.09% (95% CI: 96.86-100%), 0.32 (95% CI: 0.06-1.74), and 0.53, respectively. In addition, the estimated kappa index between the qPCR and the conventional methods was 0.12 (95% CI: -0.020-0.26). CONCLUSIONS: The diagnostic sensitivity of qPCR to detect strongyloidiasis is analogous to that of conventional parasitology methods, with an additional advantage of being capable of identifying the parasite DNA at low sample concentrations.

Gastrointestinal helminths of two populations of wild pigeons (Columba livia) in Brazil / Helmintos gastrointestinais de duas populações de pombos de vida livre (Columba livia) no Brasil

Abstract The present study analyzed gastrointestinal helminth communities in 265 wild pigeons (Columba livia) living in the municipalities of São Paulo and Tatuí, state of São Paulo, Brazil, over a one-year period. The birds were caught next to grain storage warehouses and were necropsied. A total of 790 parasites comprising one nematode species and one cestode genus were recovered from 110 pigeons, thus yielding an overall prevalence of 41.5%, mean intensity of infection of 7.2 ± 1.6 (range 1-144) and discrepancy index of 0.855. Only 15 pigeons (5.7%) presented mixed infection. The helminths isolated from the birds were Ascaridia columbae (Ascaridiidae) and Raillietina sp. (Davaineidae). The birds' weights differed according to sex but this did not influence the intensity of infection. The overall prevalence and intensity of infection did not differ between the sexes, but the prevalence was higher among the birds from Tatuí (47.8%). The gastrointestinal helminth community of C. livia was characterized in the two areas studied and parasite homogeneity was observed over the 12 months analyzed at both locations. These results make contributions to the current literature on health aspects of wild C. livia populations.

Resumo O presente estudo analisou comunidades gastrointestinais de helmintos em 265 indivíduos de Columba livia de vida livre nos municípios de São Paulo e Tatuí, estado de São Paulo, Brasil, durante um ano. As aves foram capturadas em áreas de armazenamento de grãos e sementes e necropsiadas. Um total de 790 parasitos representando uma espécie de nematódeo e um gênero de cestoide foram recuperados de 110 pombos com uma prevalência geral de 41,5%, intensidade média de infecção de 7,2 ± 1,6 (amplitude 1-144) e índice de discrepância de 0,855. Somente 15 (5,7%) pombos tiveram uma infecção mista. Os helmintos isolados das aves foram Ascaridia columbae (Ascaridiidae) e Raillietina sp. (Davaineidae). O peso das aves foi diferente entre os sexos, mas não influenciou a intensidade de infecção. A prevalência geral e a intensidade de infecção não foram diferentes entre sexo, mas a prevalência foi maior nas aves de Tatuí (47,8%). A comunidade gastrointestinal de helmintos de C. livia foi caracterizada nas duas áreas estudadas e uma homogeneidade de parasitos foi observada nos 12 meses analisados, em ambas localidades. Os resultados contribuem para a literatura atual sobre aspectos sanitários de populações de C. livia em vida livre.

La helmintología según la filosofía de la ciencia de Imre Lakatos / Helminthology according to the philosophy of science of Imre Lakatos

RESUMEN A pesar de que en distintas ramas de la biología se ha utilizado la filosofía de la ciencia de Lakatos, no se ha hecho esto con la helmintología. Aquí utilizamos su metodología de programas de investigación científica (PIC) para reconstruir la historia de la disciplina en cuestión. Sostenemos que el primer PIC de la biología lo inauguró Aristóteles, y en su cinturón protector hay un pequeño grupo de hipótesis auxiliares que se refieren a los helmintos. Ese programa se mantuvo vigente hasta el siglo XVII, época en la que surgen dos PIC rivales en helmintología: el internalista y el externalista. A partir de la segunda mitad del siglo XIX, el PIC internalista fue abandonado, mientras que el externalista amplió considerablemente su cinturón protector durante el siglo XX. El abandono del PIC internalista se debió a los experimentos cruciales de Küchenmeister, que permitieron la consolidación del PIC externalista.

ABSTRACT Lakatos’s philosophy of science has been used for different branches of biology, however this has not been true for helminthology. Therefore, this article examines the possibility of using his methodology of scientific research programmes (SRP) for reconstructing the history of the discipline of helminthology. It is upheld that the first SRP in biology was inaugurated by Aristotle, and its protective belt included a small group of auxiliary hypotheses referring to helminths. This programme continued up until the 17th century, when two rival programmes in helminthology arose: the internalist and the externalist. After the second half of the 19th century the internalist SRP was abandoned, while the externalist considerably broadened its protective belt during the 20th century. The internalist programme was abandoned due to the crucial experiments of Küchenmeister, which permitted the consolidation of the externalist SRP.