Use of a saline gradient for the diagnosis of schistosomiasis

The development of novel methods for parasitological diagnosis that are both highly sensitive and low in cost has been strongly recommended by the World Health Organization. In this study, a new technique for diagnosis of schistosomiasis mansoni is proposed based on the differential sedimentation of eggs when subjected to a slow continuous flux of 3 percent saline solution through a porous plaque. This influx suspends low-density faecal material, effectively cleaning the sample. The remaining sediment covering the porous plaque surface is then transferred to a glass slide and examined under a bright field microscope. Twelve Kato-Katz slides were used for comparison in the present study. Our results suggest that the saline gradient method detects a signifi-cantly higher number of eggs than the 12 Kato-Katz slides (p < 0.0001). We also found microscopic inspection to be quicker and easier with our newly described method. After cleaning the sample, the obtained sediment can also be conserved in a 10 percent formaldehyde solution and examined for at least 45 days later without statistically significant egg count differences.

A new miracidia hatching device for diagnosing schistosomiasis

It is still imperative to develop a parasitological technique highly sensitive for diagnosing schistosomiasis in epidemiological and individual surveys. A simple and cheap hatching device with a collecting container was manufactured and tested under experimental conditions. Twelve Kato-Katz slides were performed as golden standard for comparison. Quantitative results can be carried out by counting miracidia in a plate and parasite load can be calculated (miracidia/gram of feces). Statistically significant values were higher in the hatching test. More sensitive results, with statistical significance, were achieved using 1.5 g of feces (which corresponds to 36 Kato-Katz slides) than by using the Kato-Katz method. Advantages of this technique and its limitations are presented.

Obtención de metacercarias de Fasciola hepatica en Lymnaea cubensis y relación parásito-hospedero en ratas Wistar y ratones Balb/c / Fasciola hepatica metacercarie collection in Lymnaea cubensis, and parasite-host-relation in Winstar rats an Balb/c mice

Fueron realizados dos experimentos, en experimento I con dos métodos (necropsia y bolsa de polietileno) para colectar y comparar las metacercarias obtenidas, el experimento II que fue desarrollado para determinar la potencia invasiva de las metacercarias obtenidas en un biotipo artificial, usando ratas Wistard y ratones Balb/c inoculados con 20 y 5-10 metacercarias, respectivamente. Se encontró que el número de metacercarias obtenidas con el uso de las bolsas de polietileno es considerablemente superior (P< 0.01) a las obtenidas por disección con un total de 1 442 metacercarias y una media de 12.87 por hospederos, mientras que en el método de las bolsas de polietileno la media fue de 29.31 y el total de 3 313. La potencia invasiva (PI) y la extensión de la invasión (EI) en las ratas fue más alta en la tercera semana (PI, 23 por ciento; EI, 80 por ciento), similar a los ratones inoculados con 10 metacercarias (PI, 23 por ciento; EI, 80 por ciento). Hubo 100 por ciento de hígados afectados por ambas dosis en la tercera semana. Se concluye que el método de las bolsas de polietileno es más efectivo que la disección facilitando la obtención de gran número de formas invasivas con alta calidad, limpieza y fácil desprendimiento de las metacercarias desde la superficie de enquistamiento: así como el hecho de que la potencia invasiva y la extensión de la invasión obtenida valida su uso en las investigaciones con modelos de Fasciola hepatica en ratas y ratones con dosis apropiadas de 20 y 10 metacercarias por ratas y ratones, respectivamente

Sedimentation in parasitological coproscopy

A sedimentation technique is described, in which a fecal suspension is placed on top of an aqueous sucrose solution of specific gravity 1.015 g/cm3. Using 100 by 15 mm test tubes, duplicate gravity sedimentation experiments were made using homogenized fecal suspensions (single-columns) and fecal suspensions placed on top of clear columns (double-columns). Egg and cyst counts, and turbidity determinations were made in the sediments obtained after definite time intervals. Most Ascaris lumbricoides, Trichuris trichiura and Ancylostomidae eggs sedimented within 20 minutes in single-and between 30 and 60 minutes in double-columns. Giardia duodenalis cysts required longer periods to sediment in double-than in single-columns; after 180 minutes (the maximum period of observation), double-column sediments produced 60.0% of the counts of single-columns. Double-column sediments were consistently less turbid than single-column ones