Entamoeba sp. in a city in the Amazon interior in Brazil: Microscopic parasitological, immunological, and molecular diagnosis

Humans can become infected with different parasites, including intestinal protozoa that can cause diarrhea, dysentery, or even death. These parasites affect mainly individuals living in situations of low socioeconomic conditions, an economic and social context found in most cities in the Amazon interior. The main objective of this study was to evaluate the frequency of <i>Entamoeba</i> sp., with an emphasis on <i>E. histolytica</i>, in patients treated at the Municipal Laboratory of Oriximiná, a city located in the Amazon interior. In 2019, 294 fecal samples were obtained from people treated at the city's laboratory. All samples that showed <i>Entamoeba</i> cysts via microscopic parasitological techniques or that were positive by immunodiagnosis to <i>E. histolytica</i>/<i>E. dispar</i> complex were subjected to polymerase chain reaction (PCR) to identify positivity for <i>E. histolytica</i>, <i>E. dispar</i>, and <i>E. moshkovskii</i>. When the 81 fecal samples considered positive for <i>Entamoeba</i> were subjected to PCR, DNA amplification was observed in 37/81 (45.7 %) samples. <i>E. histolytica</i> was the most diagnosed species in 31/81 (38.3 %), and <i>E. dispar</i> was detected in 22/81 (27.2 %). All reactions performed for <i>E. moshkovskii</i> were negative. The mixed molecular diagnosis of both <i>E. histolytica</i> and <i>E. dispar</i> was confirmed in 16 (19.8 %) fecal samples. Analysis of risk factors revealed that diarrhea was significantly associated with infection by <i>Entamoeba</i> sp. and that the consumption of vegetables produced at home was associated with infection by the complex (<i>p</i> ≤ 0.05). Most of the PCR-positive samples were obtained from residents of neighborhoods from the outskirts of the city, which has the city's lowest socioeconomic indices. The results obtained in this study highlight the precariousness of basic sanitation in these cities, since the detected pathogens, including the pathogenic species <i>E. histolytica</i>, are transmitted mainly through contaminated water and food. Notably, this is the first study to confirm via molecular diagnosis the circulation of <i>E. histolytica</i> in cities in the Amazon interior of Brazil.