Morphology of Echinococcus granulosus protoscolex / Morfología de los Protoescolex de echinococcus granulosus

SUMMARY: Echinococcus granulosus (E. granulosus), is a tapeworm that spreads between intermediate and definitive hosts through the ingestion of fecal matter contaminated with the parasite's eggs. The life cycle consists of differentiation from eggs to oncospheres to embryos, which eventually form cysts in organs like the liver, lungs and others. Within these cysts are protoscolices, an intermediate stage of the parasite which develop into adult tapeworms once they infect their definitive hosts. When these hydatid cysts form in humans, it is known as Cystic Echinococcosis (CE). This disease is treated through surgical excision of the cysts and or chemotherapy with benzimidazole compounds. Understanding the morphology of the intermediate developmental stage of E. granulosus, protoscolex stage, can allow researchers to identify defining structural changes and protein functions that could be used to develop treatment modalities for CE. Unique characteristics in the tegumental surface during the protoescolex stage and proteins associated with cyst fertility have all been identified in previous research studies and bring researchers closer to understanding the underlying mechanisms of E. granulosus development, and consequently, means to disrupt it to achieve better control of the disease.

El Echinococcus granulosus (E. granulosus), es un cestodo que se propaga entre huéspedes intermedios y definitivos a través de la ingestión de materia fecal contaminada con los huevos del parásito. El ciclo de vida consiste en la diferenciación de huevos a oncosferas y embriones, que finalmente forman quistes en órganos como el hígado, los pulmones y otros. Dentro de estos quistes hay protoescólices, una etapa intermedia del parásito que se convierte en su forma adulta (tenia), una vez que infectan a sus huéspedes definitivos. Cuando estos quistes hidatídicos se desarrollan en seres humanos, se les conoce como equinococosis quística (EC). Esta enfermedad se trata mediante la extirpación quirúrgica de los quistes o la quimioterapia con compuestos benzimidazólicos. La comprensión de la morfología de la etapa de desarrollo intermedia del E. granulosus y la etapa de protosclex, puede permitir a los investigadores identificar cambios estructurales definidos y funciones de proteínas que podrían usarse para desarrollar modalidades de tratamiento para la CE. Las características únicas en la superficie tegumentaria durante la etapa de protoescolex y las proteínas asociadas con la fertilidad del quiste se han identificado en estudios de investigación anteriores y acercan a los investigadores a la comprensión de los mecanismos subyacentes del desarrollo del E. granulosus y, en consecuencia, los medios para interrumpirlo para lograr un mejor control de la enfermedad.

Estudio morfocuantitativo de protoescólices y otras estructuras fundamentales de Echinococcus granulosus en hospederos humanos / Morphoquantitative study of protoscolices and other fundamental structures of Echinococcus granulosus in human hosts

La equinococosis quística (EQ) a pesar de ser una enfermedad endémica en diversos lugares del planeta, presenta pocos estudios morfológicos y cuantitativos de las estructuras fundamentales del Echinococcus granulosus en humanos, en especial de los protoescólices. El objetivo de este estudio fue analizar morfocuantitativamente protoescólices y otras estructuras fundamentales de E. granulosus obtenidos de hospederos humanos. Estudio de corte transversal. Se estudiaron 8 especímenes de EQ hepática humana, aplicando un muestreo no probabilístico por conveniencia. Se evaluó las capas quísticas, el líquido y la arenilla hidatídica. Las capas fueron fijadas en formaldehido tamponado a 10 % y procesadas para su inclusión en paraplast. Se realizaron cortes de 5 µm de grosor y fueron teñidas con H-E para su análisis con microscopía óptica. El líquido y arenilla fueron centrifugados y al sedimento obtenido se le realizó análisis directo para determinar las medidas morfométricas de los protoescólices y de los ganchos grandes y pequeños. Se utilizó estadística descriptiva. De los 8 quistes estudiados, 6 eran quistes univesicular, uno multivesicular y un quiste abscedado, cuyas capas laminada y germinativa se encontraban bien definidas. Las vesículas prolígeras presentaban forma redondeada con protoescólices en su interior. Los protoescólices invaginados presentaron un largo y ancho promedio de 140,8 ± 34,3 µm y 106,2 ± 29,5 µm, respectivamente; y los desarrollados un largo de 237,2 ± 53,0 µm y ancho de 128,7 ± 32,0 µm. Los ganchos rostelares presentaron contornos suaves distribuidos en dos filas regulares. El promedio del largo total de los ganchos grandes y pequeños fue 20,1 ± 2,7 µm; el promedio del ancho total fue 7,4 ± 1,2 µm. En conclusión, las características morfocuantitativas de los ganchos de E. granulosus en humanos, son distintos a otras especies hospederas intermediarias y de otros Echinococcus spp. Es posible que el abandono del estado de resistencia de los protoescólices invaginado hasta su desarrollo genere implicancias epidemiológicas de interés.

SUMMARY: Although cystic echinococcosis (CE) is an endemic disease in several parts of the world, few morphological and quantitative studies of the fundamental structures of Echinococcus granulosus in humans, especially protoscolices. The aim of this study was to perform a morphoquantitative analysis of protoescolex and other fundamental structures of E. granulosus from human hosts. Cross- sectional study. Eight human hepatic EQ specimens were studied, applying non-probabilistic convenience sampling. Cystic layers, fluid and hydatid grit were evaluated. The layers were fixed in 10% buffered formaldehyde and processed for embedding in paraplast. Slices of 5 µm thickness were made and stained with H-E for light microscopic analysis. The liquid and grit were centrifuged and the sediment obtained was analyzed directly to determine the morphometric measurements of the protoscolices and the large and small hooks. Descriptive statistics were used. Of the 8 cysts studied, 6 were univesicular cysts, one multivesicular and one abscessed cyst, whose lamellar and germinative layers were well defined. The proligerous vesicles had a rounded shape with protoscolices inside. The invaginated protoscolices had an average length and width of 140.8 ± 34.3 µm and 106.2 ± 29.5 µm, respectively; and the developed ones had a length of 237.2 ± 53.0 µm and width of 128.7 ± 32.0 µm. The rostellar hooks presented smooth contours distributed in two regular rows. The average total length of the large and small hooks was 20.1 ± 2.7 µm; the average total width was 7.4 ± 1.2 µm. In conclusion, the morphoquantitative characteristics of E. granulosus hooks in humans are distinct from other intermediate host species and from other Echinococcus spp. It is possible that the abandonment of the resistance state of the invaginated protoscolices until their development generates epidemiological implications of interest.

Genotype and Phenotype of Echinococcus granulosus Derived from Wild Sheep (Ovis orientalis) in Iran

The aim of the present study is to determine the characteristics of genotype and phenotype of Echinococcus granulosus derived from wild sheep and to compare them with the strains of E. granulosus sensu stricto (sheep-dog) and E. granulosus camel strain (camel-dog) in Iran. In Khojir National Park, near Tehran, Iran, a fertile hydatid cyst was recently found in the liver of a dead wild sheep (Ovis orientalis). The number of protoscolices (n=6,000) proved enough for an experimental infection in a dog. The characteristics of large and small hooks of metacestode were statistically determined as the sensu stricto strain but not the camel strain (P=0.5). To determine E. granulosus genotype, 20 adult worms of this type were collected from the infected dog. The second internal transcribed spacer (ITS2) of the nuclear ribosomal DNA (rDNA) and cytochrome c oxidase 1 subunit (COX1) of the mitochondrial DNA were amplified from individual adult worm by PCR. Subsequently, the PCR product was sequenced by Sanger method. The lengths of ITS2 and COX1 sequences were 378 and 857 bp, respectively, for all the sequenced samples. The amplified DNA sequences from both ribosomal and mitochondrial genes were highly similar (99% and 98%, respectively) to that of the ovine strain in the GenBank database. The results of the present study indicate that the morpho-molecular features and characteristics of E. granulosus in the Iranian wild sheep are the same as those of the sheep-dog E. granulosus sensu stricto strain.

Studies on the Protoscoleces and Hooks of Echinococcus Granulosus from Libya by Scanning Electron Microscope.

Introduction: Protoscolex and hook morphology had been used to identify different strains of Echinococcus granulosus. Method: In the present study, hydatid sand was isolated from infected organs such as liver, lung and spleen from slaughtered animals in several abattoirs in the selected study areas in Libya. Scanning Electron Microscope (SEM) was used to describe the outer surface of the Protoscoleces and the hooks. Result: SEM pictures showed different morphological characters of the outer surface of the different parts of the same protoscolex. Also, the buds on the outer surface of brood capsule, and showed some differences between the large and small hooks. These findings appeared the that there was a correlation with significant statistical difference between the measurements of large as well as small hooks from the same organs of each host as well as between different hosts. Conclusion: Finally, it was difficult to determine whether these cases are not real distortions in the morphology of E. granulosus. They possibly could be caused by mutation or related to a special strain of E.granulosus. Thus, the findings of the present study would suggest that there is a need to consider relationships between the different characters of hooks with different strains of E.granulosus.