Echinococcosis in sub-Saharan Africa: emerging complexity.

Parasitology Unit, University of Hohenheim, 70599 Stuttgart, Germany.
Veterinary Parasitology (Impact Factor: 2.38). 04/2011; 181(1):43-7. DOI: 10.1016/j.vetpar.2011.04.022
Source: PubMed

ABSTRACT Cystic echinococcosis occurs in most regions of sub-Saharan Africa, but the frequency of this zoonosis differs considerably among and within countries. Especially human cases seem to be focally distributed. A number of environmental and behavioural factors partially explain this pattern, i.e. density of livestock, presence of dogs, uncontrolled slaughter, and hygiene. In addition, the various taxa of Echinococcus spp. are known to differ considerably in infectivity to different host species including humans. Genetic characterizations of isolates, which are necessary to evaluate the impact of this factor - so far done in only a few countries - indicate that the diversity of Echinococcus spp. in Sub-Saharan Africa is greater than on any other continent. The very incomplete data which are available show that sympatrical taxa may infect different hosts, others may be geographically restricted, some life cycles involve livestock, others wild animals. Possible implications of this complexity for public health, livestock economy and conservation are briefly discussed.

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    ABSTRACT: The present study investigates the damages of high intensity focused ultrasound (HIFU) to transplanted hydatid cysts in abdominal cavities of rabbits with aids of ultrasound contrast agent (UCA) and superabsorbent polymer (SAP) alone or in combination. A rabbit model with transplanted hydatid cyst was established by implanting hydatid cyst isolated from infected sheep liver, and HIFU was used to ablate the transplanted cysts with the aid of UCA and SAP alone or in combination. The hydatid cyst with thin wall, good elasticity, approximately spherical, and a diameter of approximately 30 mm was selected for the following experiments. According to our previous studies, a mixture of 0.1 g SAP and 0.5 ml anhydrous ethanol, and the solution of 0.1 ml UCA SonoVue, or both materials were injected into different cyst before HIFU ablation, respectively. The cyst inoculated with the SAP and UCA alone or in combination was immediately implanted into the abdominal cavity of rabbit for HIFU ablation at a dosage of 100 W acoustic powers. The ablation mode was spot scanning at the speed of 3 mm/s. Every target point was scanned three times; every ablating time lasted 3 s. The distance of each ablated layer was 5 mm. The total ablation time depended on the volume of cyst. The comparison of ultrasound image for each layer of hydatid cyst was made before and after HIFU ablation. The protoscolices in ablated cysts were stained by trypan blue exclusion assay, and their structures were observed by light microscopy. To estimate ablation effects of HIFU to the walls of hydatid cysts, the ultrastructure changes of cyst walls were examined by electron microscopy. The pathological changes of rabbits' skins through which ultrasound penetrated were observed to investigate the side effects of HIFU ablation. The results demonstrated that HIFU had some lethal effects to hydatid cysts in vivo, namely, echo enhancements of ultrasound images of cysts, increases in mortality rate of protoscolices from 15.19 % (HIFU alone) to 48.66 % (HIFU + SAP), 38.67 % (HIFU + UCA), and 67.75 % (HIFU + SAP + UCA), respectively, serious structural damages of protoscolices, and destructions or even disappearance of laminated layers and germinal layers in the walls of hydatid cysts ablated by HIFU aided with UCA and SAP alone or in combination. This study demonstrated that destructive effects of HIFU to transplanted hydatid cyst could be enhanced by UCA and SAP alone, but the destruction of HIFU aided with a combination of UCA and SAP to hydatid cysts was more effective than those aided with UCA or SAP alone. The enhanced thermal and cavitation effects of HIFU induced by UCA and SAP might be involved in the enhanced destructive effects of HIFU on hydatid cysts. There were no evidences of pathological changes on rabbits' skins overlying the hydatid cysts after HIFU ablation. The results suggested that the rabbit model with transplanted hydatid cyst may serve as an optional animal model for the experiments of HIFU ablation to hydatid cyst in vivo, and the materials of UCA and SAP were proved as enhancing agents of HIFU ablation to hydatid cysts, and HIFU at a dosage of 100 W acoustic powers was a safe and feasible parameter to ablate the hydatid cysts in this special animal model. These results laid a theoretical foundation for improving HIFU therapy for cystic echinococcosis by inoculation of UCA and SAP into hydatid cysts.
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