Richards Ks

Comparison of albendazole, mebendazole and praziquantel chemotherapy of Echinococcus multilocularis in a gerbil model.

The efficacy of albendazole (50 mg/kg/d), mebendazole (50 mg/kg/d) and praziquantel (500 mg/kg/d) against established intraperitoneal infections of Echinococcus multilocularis in gerbils was compared by monitoring parasite weight and making ultrastructural observations on treated and untreated material. Praziquantel was the most active protoscolicidal agent, reducing protoscolex viability to less than 2%, although it did not inhibit cyst growth. Albendazole was the most effective agent in reducing cyst growth and was, when compared with other regimes significantly more effective than mebendazole (p less than 0.05), praziquantel (p less than 0.01) or untreated controls (p less than 0.01).

Echinococcus granulosus: in vitro maintenance of whole cysts and the assessment of the effects of albendazole sulphoxide and praziquantel on the germinal layer

Small entire cysts of Echinococcus granulosus of human and animal origin were cultured in vitro in the presence or absence of albendazole sulphoxide (1000 micrograms/litre) or praziquantel (500 micrograms/litre) for 10 or 11 d, and subsequently passaged into the peritoneal cavity of gerbils to assess viability by continued cyst growth. Viability was reduced in the presence of albendazole sulphoxide, and disintegration of the germinal layer immediately after culture was demonstrated at the ultrastructural level. Praziquantel had no apparent effect on cyst growth.

Echinococcus multilocularis: in vivo results of therapy with albendazole and praziquantel

The effects of albendazole and praziquantel on the growth of Echinococcus multilocularis were studied in cotton rats. Albendazole (20 and 50 mg/kg) reduced parasite weight and increased the length of survival of infected animals but viable infection was present after treatment. In an in vitro system albendazole sulphoxide entered cysts of E. multilocularis passively. Praziquantel 100 mg/kg was ineffective but 500 mg/kg significantly inhibited growth. A combination of albendazole and praziquantel was no more effective than either agent alone.

Combination chemotherapy of Echinococcus granulosus — in vitro studies

Both benzimidazole carbamates and isoquinoline compounds have activity against protoscoleces of Echinococcus granulosus in culture in vitro; combinations of albendazole sulphoxide and praziquantel are more effective than either agent alone.

Determination of minimum effective concentration of praziquantel in in vitro cultures of protoscoleces of Echinococcus granulosus

The minimum effective concentration of praziquantel against protoscoleces of Echinococcus granulosus (ovine strain) was determined in vitro; 20 micrograms/litre gave statistically significant results. No difference was seen between the sensitivity of ovine and equine protoscoleces at 50 micrograms/litre. Morphological observations on treated protocsoleces and passage into gerbils both suggested that the eosin-exclusion technique overestimates viability. Electron microscopy of treated protoscoleces showed severe, disruptive tegumentary damage. Praziquantel is thus an extremely active protoscolicidal agent that may have an important peri-operative role in preventing recurrence.

Echinococcus granulosus equinus: variation in the germinal layer of murine hydatids and evidence of autophagy.

The germinal layer of sterile 9-month-old murine peritoneal cysts of Echinococcus granulosus equinus shows interrelated variation in depth, tissue integrity, metabolic reserves and the number of autophagic lamellar bodies present. These features are similar in large and medium-sized cysts from the same host, whether occurring singly or within cyst masses. Deep germinal layers (greater than 16 micron) are lipid- and glycogen-rich and possess numerous autophagic vacuoles with 6 nm period lamellar stacks asymmetrically disposed peripherally; shallow layers (less than 12 micron), with indications of degeneration, have depleted metabolic reserves and fewer lamellar bodies. These bodies are formed by smooth endoplasmic reticulum encirclement of small glycogen masses followed by further sequestration, and eventually definition of glycogen particles may be lost. Autophagy of mitochondria and cytoplasmic vesicles also occurs. The presence of lysosomal enzymes within the layer suggests autolysosomal compartmentalization of excess substrate and effete material. Mucopolysaccharide bodies, containing material similar to that exocytosed to form the laminated layer matrix, occur and are formed from fusion and autophagy of Golgi-derived vesicles. These bodies may also develop peripheral 6 nm period lamellar stacks, but of limited depth. Mucopolysaccharide bodies are the dominant feature of the germinal layer of very small cyst-mass cysts in which laminated layer production is considered to be arrested. They thus represent a repository for the unreleased mucopolysaccharide material.

Comparison of Albendazole and Praziquantel therapy of Echinococcus granulosus in naturally infected sheep.

The effects of albendazole (10 mg kg-1 day-1) and praziquantel (50 mg kg-1 day-1) for 6 weeks on naturally infected sheep with pulmonary cysts of Echinococcus granulosus of proven viability were studied. Immediately following therapy, one of three sheep treated with praziquantel had viable cysts and 7 months later one of two sheep had viable cysts. One sheep died during albendazole therapy, but 7 months following therapy only one of five sheep had viable cysts. Electron microscopy demonstrated necrotic germinal layer tissue in most albendazole-treated cysts and praziquantel also had an effect on cyst ultrastructure. These data suggest that recurrence in humans treated with albendazole may be small. Whilst praziquantel was not particularly effective in this animal model, its clear effect on the ultrastructure suggests that an increased dose and combination therapy with albendazole may be more effective.

Rapid recovery of Echinococcus granulosus following successful albendazole therapy in a gerbil model

Peritoneal Echinococcus granulosus in gerbils was treated with albendazole. Both early and late infections were studied; response to albendazole therapy and the ability of the parasite to recover after treatment was found to depend on dose and length of therapy. Even after treatment at 50 mg/kg for 2 months late infections retained the ability to recover over 3 months.

Ultrastructure and microanalyses of the protoscolex hooks of Echinococcus granulosus

The rostellar distal cytoplasm of Echinococcus granulosus protoscoleces is characterized by extensive basal membrane infolding, prominent hemidesmosomes and is subtended by a lamina reticularis with microfibrils of approximately 10 nm diameter that occasionally show a 55 nm banding periodicity. The rostellar hooks, in 2 rows, each have a blade, guard and handle region and possess a central amorphous pulp, a middle microfibrillar medulla with microfibrils of approximately 4 nm diameter, and a complex outer cortex in all but the proximal region of the guard and the base of the handle. In these regions additional material, of similar electron density to the medulla, but lacking the fibrillar substructure, occurs and gives the areas a lobed appearance. Energy-dispersive X-ray microanalysis of whole hooks demonstrated the presence of sulphur and trace quantities of phosphorus. X-ray near-edge absorption spectra resembled those of cystine, feather and hair and showed the sulphur to be predominantly in the form of disulphide linkages. X-ray diffraction patterns of whole hook preparations revealed 2 diffuse rings with equatorial spacings of 7.99 A and 15.22 A, thus differing from vertebrate keratins.

Perioperative prophylactic chemotherapy of Echinococcus granulosus: determination of minimum effective length of albendazole therapy in in vitro protoscolex culture.

Protoscoleces of Echinococcus granulosus were cultured in vitro in 500, 250 or 100 μg/1 albendazole sulphoxide for 1, 3, 7, 10, 14d and then ‘recued’ (R) into drug-free medium for the remainder ofthe culture period. Successful minimum lengths of therapy were much longer than for praziquantel, and only at 500μg/1 was the 10dR treatment as effective as continuous therapy for 28d. Treatment with 100 μg/1 both in continuous culture and in the ‘R’ experiments was ineffective over a 35d period. The results are compared with those from similar experiments using praziquantel.