Lethal effects of praziquantel and albendazole, on the cercariae of Echinochasmus sp. (Dietz, 1909) in-vitro

Abstract

Echinochasmidae are considered one of the digenean intestinal parasites of carnivorous mammals and humans. Some larvicidal medications, such as praziquantel and albendazole, were employed to interrupt the life cycle of Echinochasmidae, which may cause harmful and serious effects on the domestic fish, ducks, and humans in our ecosystem. Cercariae of Echinochasmus sp. (gymnocephalus type) were harvested by exposing snails to strong artificial illumination. The emerging cercariae were exposed in vitro to different concentrations of praziquantel and albendazole at the same period of incubation 12 h. Using probit analysis in SPSS version 25, the lethal concentrations 50 and 95% were determined. They were 0.036 and 0.82 ppm, respectively, for praziquantel and 5.3 and 9.2 ppm, respectively, for albendazole. The ultrastructural changes using scanning electron microscope on the tegumental surface of the treated cercariae with the two drugs were compared to the untreated cercariae. The untreated cercariae have a pear-shaped body with a long tail. The oral sucker is armed with a spiny collar and decorated with ciliated and unciliated sensory papillae. The cardinal ventral sucker has a thick, muscular wall. The cercarial tail is decorated with parallel longitudinal tegumental processes and spherical, unciliated papillae. In comparisons, cercariae treated with both drugs lost all healthy morphological features, but in varying degrees and effects between the two drugs. Our findings suggest that the use of both drugs can be recommended during the design of control strategies to combat this type of intestinal parasite.

Keywords: Albendazole; Echinochasmus; Gymnocephalus cercariae; Lanistes; Praziquantel.

Fig. 1

The mortality rate of the cercariae of Echinochasmus sp. at various concentrations of both drugs, praziquantel and albendazole, respectively, was exposed at 12 h. a The effects of praziquantel on the cercariae of Echinochasmus sp. at lethal doses of 0.025, 0.5, and 0.1 ppm, respectively. b The effects of albendazole on the cercariae of Echinochasmus sp. cercariae at lethal doses of 5, 6, and 7 ppm, respectively. (Note: The number above the columns means the maximum value of the number of dead cercariae ± SD of each dose.)

Fig. 2

a–f Scanning electron micrographs (SEMs) of untreated cercariae of Echinochasmus sp. (in group 1) emerged from the freshwater snail, Lanistes carinatus. a Ventral view of the cercariae of Echinochasmus sp., showing a pear-shaped cercarial body (B) and an elongated tail (T) (scale bar 20 µm). b Sub-terminal oral sucker (OS), surrounded by ciliated sensory papillae (arrow head) and armed with spines (thick arrows) (scale bar 5 µm). c Ventral sucker of cercariae (Vs) had a slightly triangular shape, B; cercarial body (scale bar 10 µm). d Cercarial tail (T) has longitudinal tegumental processes and is decorated with small, spherical papillae (scale bar 5 µm). e The tail end of cercariae (TE) that is decorated with a few unciliated sensory papillae (arrow) (scale bar 1 µm). f The anterior part of the dorsal tegumental cercaria body (TB) has a rough appearance with a few scattered unciliated sensory papillae (arrow) (scale bar 5 µm)

Fig. 3

a–f Scanning electron micrographs (SEMs) of the treated cercariae of Echinochasmus sp. with praziquantel (in group 2). a Ventral view of the cercariae of Echinochasmus sp. showing a semi-quadrated cercarial body (B) and a deformed tail (T) (scale bar 20 µm). b The oral sucker (OS) was contracted, destroyed, and devoid of sensory papillae and spines (scale bar 10 µm). c Ventral sucker of cercaria (Vs) was shrunken (scale bar 10 µm). d Cercarial tail (T) was broad and flattened with two dents and the disappearance of tegumental papillae and processes (scale bar 10 µm). e The tail end of treated cercariae (TE) was devoid of any sensory papillae and tegumental processes (scale bar 5 µm). f The cercarial body tegument (TB) was deformed (scale bar 5 µm)

Fig. 4

a–f Scanning electron micrographs (SEMs) of the treated cercariae of Echinochasmus sp. with albendazole (in group 3). a Ventral view of the cercariae of Echinochasmus sp., showing a semi-cardiac cercarial body (B) and swollen tail (T) (scale bar 20 µm). b The oral sucker (OS) was destroyed, very contracted, and still armed with spines (thick arrows). The ciliated sensory papillae appeared without the cilia (arrows) (scale bar 5 µm). c Ventral sucker of treated cercaria (Vs) was elongated and deformed (scale bar 10 µm). d Cercarial tail (T) was peeling, flattened with two dents, and without any tegumental structures (scale bar 10 µm). e The tail end of treated cercariae (TE) was paddle-shaped and devoid of any sensory papillae or tegumental processes (scale bar 5 µm). f Lateral view of the treated cercarial body (TB) showed a rough-looking surface due to the presence of rows of blurred tegumental protrusions (scale bar 5 µm)