Detección y diferenciación de Entamoeba histolytica y Entamoeba dispar mediante reacción en cadena de la polimerasa en individuos de una comunidad del Estado Zulia, Venezuela / Detection and differentiation of Entamoeba histolytica and Entamoeba dispar by polymerase chain reaction in a community in Zulia State, Venezuela

Differential identification of Entamoeba histolytica and Entamoeba dispar is essential for both appropriate patient treatment and epidemiological purposes. To determine the prevalence of these amoeba infections in Santa Rosa de Agua (Maracaibo, Zulia State, Venezuela), a PCR assay using specific primers for each species was standardized and applied. 204 stool samples were analyzed through direct microscopic examination with SSF (0.85 percent) and lugol, formol-ether concentration, and PCR. Under direct microscopy, 42 individuals (20.58 percent) presented the E. histolytica/E. dispar complex. Meanwhile PCR showed 47 positive cases for these amoebas: 22 E. histolytica (10.78 percent), 16 E. dispar (7.84 percent), and 9 (4.41 percent) mixed infections. There was no significant difference in the presence of E. histolytica and/or E. dispar according to either gender or age. There were no cases of these amoebas in children under 2 years of age. Observed frequency of E. histolytica (31/204) shows the endemic nature of amoeba infection in this community.

La identificación diferencial de Entamoeba histolytica y Entamoeba dispar es esencial para un tratamiento adecuado del paciente y con fines epidemiológicos. Para determinar la prevalencia de E. histolytica y E. dispar se estandarizó y aplicó un ensayo de PCR, utilizando oligonucleótidos específicos para cada especie. 204 muestras de heces de individuos de la comunidad de Santa Rosa de Agua (Municipio Maracaibo, Estado Zulia, Venezuela), fueron analizadas a través del examen directo con SSF (0,85 por ciento) y lugol, concentrado de formol-éter y PCR. Al examen microscópico, 42 individuos (20,58 por ciento) presentaron formas evolutivas del complejo E. histolytica/E. dispar; mientras que la técnica de PCR evidenció un total de 47 casos positivos a estas amibas; de los cuales 22 eran portadores de E. histolytica (10,78 por ciento), 16 (7,84 por ciento) de E. dispar y 9 (4,41 por ciento) presentaron infección mixta. No hubo diferencia significativa al relacionar las variables sexo y presencia de E. histolytica y/o E. dispar, ni con los grupos etarios. No existieron casos de estas amibas, en los menores de 2 años. La frecuencia observada de E. histolytica (31/204), demuestra el carácter endémico de la amibiasis en esta comunidad.

Malaria parasite developmental analyses by the nested polymerase chain reaction method: an implication for the evaluation of mosquito infection rates in epidemiological studies.

A malaria mosquito vector, Anopheles saperoi, and a non-vector, Aedes albopictus, were allowed to feed on mice infected with murine malaria, Plasmodium yoelii nigeriensis, and were subsequently monitored for the development of parasites by the nested polymerase chain reaction (PCR) method, using Plasmodium genus-specific primer pairs. The mosquitos were divided into two parts, head/thorax and abdomen, for DNA analyses. The parasite DNA and murine DNA for each mosquito were examined in parallel. In both groups of mosquitos, murine DNA was detected up to 4 days post-blood meal in both the head/thorax and abdomen. After 4 days, the murine DNA fell below detectable limits. Murine DNA and parasite DNA remained undigested for the first 4 days post-blood meal. Parasite DNA was detected in the abdomen of 25% (3/12) of Ae. albopictus on day five and 10% (1/10) on day six, after murine DNA had fallen below detectable limits. Parasite DNA was not detected in the head/thorax of Ae. albopictus on those days or afterwards in either the head/thorax or abdomen, demonstrating that the parasite detected on days 5 and 6 in the abdomen degenerated and did not develop into mature oocysts or sporozoites. In the vector An. saperoi, parasite DNA was detected continuously in the head/thorax and abdomen for many days after the murine DNA had fallen below detectable limits. The detection rate of parasite DNA in the head/thorax of An. saperoi increased gradually from day 8 post blood meal until it reached a maximum level of 71.4% (15/21 12 days post-infection. Parasite DNA in abdomen reached its maximum level of 81% (17/21) 10 days post-blood meal. The implications of these results for the design and interpretation of epidemiological surveys is discussed.