Could ivermectin have a synergic effect with albendazole in hydatidosis therapy?

The efficacy of a combination of ivermectin (IVM) and albendazole (ABZ) used as a chemoprophylactic treatment and as treatment of secondary hydatidosis is described for the first time. IVM treatment alone was not effective against Echinococcus granulosus, either when the protoscolices were recently inoculated or when they had developed to the metacestode stage. However, the efficacy of IVM and ABZ when used in combination as a prophylactic treatment was 95.72% and 87% with respect to the number and the wet weight of cysts, respectively. These results were higher than in the treatment of secondary hydatidosis, which were 44.8% and 45.26%, respectively. The ultrastructural changes in the germinal layer of the cysts after the treatments are also described.

Could ivermectin have a synergic effect with albendazole in hydatidosis therapy?

The efficacy of ivermectin (IVM) alone, albendazole (ABZ) alone and a combination of both (IVM + ABZ) against Echinococcus granulosus protoscolices was studied by means of in vitro incubation. The maximum protoscolicidal effect was detected when we used IVM+ABZ in combination. In this case, protoscolex viability dropped to 35% in comparison with 50% for IVM alone and 82.5% with ABZ alone 18 days post-incubation. Only the protoscolices incubated with IVM + ABZ did not develop into cysts following their inoculation into mice. The changes in ultrastructure induced in the protoscolices after the different drug incubations are also described. The incubation of cysts with IVM and IVM + ABZ shows that IVM + ABZ in combination is more effective than IVM alone as only when we incubated the cysts with IVM + ABZ did they completely lose their infectivity to mice. This occurred after only 10 days post-incubation. Cellular alterations were also more marked with IVM+ABZ incubations with: (1) the presence of residual bodies, (2) numerous lipids droplets and (3) vacuoles in the cytoplasm of cytons. However, the truncated microtriches and the nuclei remained unaltered after 10 days.

Relationship between the efficacy of praziquantel treatment and the cystic differentiation in vivo of Echinococcus granulosus metacestode.

The cyst differentiation of protoscolices inoculated in NMRI mice was studied in detail. Although the laminated layer began its formation at 21 days post-infection (p.i.), we could not identify this structure in all parasites until 34 days p.i.. At 34 days p.i., all protoscolices were transformed into the metacestode stage. Subsequently, the efficacy of praziquantel (PZ) was studied in different stages of development of the parasite. We have found a different PZ susceptibility in both earlier stages and well-developed cyst. PZ treatment exhibited a high efficacy at the beginning of cyst differentiation and a zero efficacy in the mature metacestode when the cystic layers were totally developed. The relationship between the tegumental ultrastructural changes occurring during the vesicular evolution of protoscolices in NMRI mice and the efficacy of PZ treatment is discussed in the present study.

Depolarization of the tegument precedes morphological alterations in Echinococcus granulosus protoscoleces incubated with ivermectin.

The nematocidal activity of ivermectin (IVM) largely arises from its activity as a potent agonist of muscular and neuronal glutamate-gated chloride channels. A cestocidal effect has also been suggested following in vitro treatments, but the molecular basis of this activity is not clear. We studied the effect of IVM on the metacestode stage of the tapeworm Echinococcus granulosus by assessing the viability, ultrastructure, and tegumental membrane potential as a function of drug concentration and incubation time. Concentrations of 0.1 and 1.0 microg/ml of IVM had no effect on any of these three parameters for up to 6 days of treatment. A concentration of 10 microg/ml, however, elicited a sequence of alterations that started with a approximately 20-mV depolarization of the tegumental membrane, and was followed by rostellar disorganization, rigid paralysis and, eventually, loss of viability. It is likely that the IVM-induced depolarization of the tegument acts as the signal that initiates the cascade of degenerative processes that leads to the parasite's death. This would place the tegument as the primary target of action of IVM on cestodes. As an appropriate chemotherapy for the hydatid disease is still lacking, the cestocidal effect of IVM reported here is worth considering.

Combined praziquantel and albendazole chemoprophylaxis in experimental hydatidosis.

The results of the chemoprophylaxis of experimental hydatidosis with a combination of praziquantel and albendazole are presented. In vivo studies were performed on NMRI mice injected with protoscolices of Echinococcus granulosus. The treatment was the same as that previously used by us, but reducing the treatment period to only 1 month. Four months after injection , the mice were killed and autopsied. Developed hydatid cysts were counted, weighed and processed for observation by transmission electron microscopy. The efficacy of the present treatment was 97.7% and 97.15%, in number and weight of the cysts respectively, only slightly lower than that obtained by us after 4 months of treatment. Moreover, the few cysts that had developed in the treated mice showed severe damage to their ultrastructure.

Chemoprophylactic praziquantel treatment in experimental hydatidosis.

In the present study, new data on the chemoprophylactic treatment of experimental hydatid disease with praziquantel are presented. In vivo studies have been performed reducing the treatment to 1 and 2 months. NMRI female mice inoculated with protoscolices of Echinococcus granulosus were treated with praziquantel 48 h p.i. at a dose of 600 mg/kg, 5 days a week for 1 or 2 months. After 4 months p.i. the animals were killed, and the cysts obtained were counted, weighed and processed for observations by means of transmission electron microscopy. Both wet weight and number of hyaline cysts found in treated mice were significantly lower than those found in control groups in both experiments (1 and 2 months of treatment), obtaining a high efficacy in all cases. Moreover, severe ultrastructural damage in the treated cysts was seen compared to the control cysts. The reduction in treatment time lays the basis for an important advance in the control and prevention of hydatidosis.

Praziquantel and albendazole in the combined treatment of experimental hydatid disease.

The combination of praziquantel and albendazole (PZ + ABZ) used in the present study demonstrated an efficacy of 100% when used as chemoprophylactic treatment because no viable hydatid cysts developed after mice had been injected with protoscolices. However, when the PZ + ABZ combination was used for the treatment of 4-month secondary experimental hydatidosis, no significant difference was found between the control and treated mice, although severe damage to the cyst ultrastructure of the treated mice was observed.

In vitro effect of praziquantel and albendazole combination therapy on the larval stage of Echinococcus granulosus.

Protoscolices of Echinococcus granulosus were incubated in vitro with praziquantel (PZ), albendazole (ABZ), or a combination of both (PZ + ABZ). PZ and ABZ displayed slower protoscolicidal activity when applied separately than when used in combination. Despite the low PZ + ABZ concentrations used, protoscolex viability dropped rapidly (within 15 days). At this time, cysts did not develop following their inoculation into mice. The ultrastructural changes induced in the protoscolices by PZ + ABZ were (a) the loss of sucker concavity, (b tegumental contraction of the soma region, (c) the formation of digitiform tegumental extensions, (d) destruction of the tegument, and (e) the degeneration of parenchyma cells as reflected by the presence of numerous lamellar bodies. The PZ + ABZ treatment was effective only against small cysts, which had collapsed at 10 days postinoculation (p.i.). This treatment caused the following alterations: (a) loss of cyst turgidity at 6 days p.i.; (b) separation of the laminated and germinal layers; (c) loss of microtriches; (d) the appearance of numerous lipid droplets in the inner region of the germinal layer, (e) vacuolation of the cyton cytoplasm; and (f) the formation of abundant autophagosomes, which finally led to loss of the integrity of the germinal layer.

Ultrastructural study of the papillae and presumed sensory receptors in the scolex of the Gymnorhynchus gigas plerocercoid (Cestoda: Trypanorhyncha).

The ultrastructure of the papillae and presumed sensory receptors in the tegument of the scolex of Gymnorhynchus gigas plerocercoid were investigated by scanning and transmission electron microscopy. Four distinct types of putative sense receptor (including three uniciliated and one nonciliated) are described for the first time in G. gigas, and this investigation is the first detailed ultrastructure study of tegumental receptors carried out in trypanorhynch cestodes. Microtriches arranged in clusters with a dome-shaped pattern seemed to be papillae that contained a ciliated sensory receptor (type I). The density of these papillae was greater in the center of the bothridial adherent surface near the tentacle orifice than in the lateral margins of the bothridia or in the pars post-bothridialis. The type I receptor is characterized by a long cilium anchored in the nerve bulb by a dense basal body but lacks rootlets. The bulb contains one or two electron-dense collars, numerous electron-lucent neurovesicles, and some mitochondria. The type II receptor presents a short cilium retracted into an invagination of the tegument that arises from the basal body. The bulb contains one electron-dense collar and numerous electron-lucent vesicles, but the rootlets are absent. The type III receptor is also a ciliated receptor embedded in a bulb wider than that of types I and II, and it differs from type II in that it possesses two electron-dense collars and small rootlets associated with the basal body. No electron-lucent vesicle was found in the bulb of this type III receptor. The type IV receptor is a nonciliated receptor localized under the surface with no contact to the outside. It consists of a flattened bulb that contains two electron-dense collars and striated rootlets associated with a band of microfilaments. A comparison of the ultrastructural features of receptors in different cestodes is presented.

Echinococcus granulosus: praziquantel treatment against the metacestode stage.

The efficacy of praziquantel against the metacestode of Echinococcus granulosus was studied by means of in vitro incubations or in vivo experiments. The results of in vitro incubations indicated that the effectiveness of praziquantel was higher when the parasite material comprised cysts from cyst masses than in the case of intact cysts that retained their adventitial layer. Ultrastructural alterations in the germinal layer of collapsed cysts incubated in vitro were detected. The results obtained in mice after 4 months of treatment demonstrated no significant difference between the control and treated groups with regard to the number and wet weight of developed cysts. However, ultrastructural alterations were detected in the cyst tissue that were similar to those described in the in vitro experiment. In contrast, the effect of chemoprophylaxis on the number and the wet weight of developed cysts was extremely significant as compared with the control value, the efficacy being 99.41% and 98.32%, respectively. Moreover, ultrastructural observations of the cyst tissue revealed loss of its integrity, and no intact cyton was observed in the germinal layer of the developed cyst.