Comparative study among lactophenol blue, lactophenol solution and proteinase-K lytic solution for rostellar hooks morphometry of Echinococcus granulosus protoscolices

SummaryEchinococcus granulosus is a tapeworm whose life cycle includes dogs and other canines as final hosts, while domestic and wild ungulates act as intermediate hosts for the tissue-invading larval stage (metacestode). E. granulosus has a worldwide geographical distribution. Protoscolices and rostellar hooks of E. granulosus are useful for diagnosis and rostellar hook morphometric features may be useful to discriminate E. granulosus and related species. The present study was aimed to determine a more suitable lytic solution and to obtain a clearest vision for performing morphometric studies on the rostellar hooks of E. granulosus protoscolices. Five fertile hydatid cyst samples were collected from sheep in Kirkuk slaughterhouse, Iraq, during June of 2015. According to the results of the present study, proteinase-K lytic solution is the best approach in morphometric analysis to get a clear vision of rostellar hooks and a safer usage in comparison with solutions containing lactophenol (lactophenol, lactophenol blue).

Genetic and morphometric categorization ofTaenia ovisfrom Sheep in Iran

Little is known about the genetic and morphological characters ofTaenia ovis. The purpose of the present study was to characterize sheep isolates ofT. ovisusing rostellar hook morphometry as well as mitochondrial genes sequence analysis. Ninety sheep specimens ofCysticercus oviswere collected from 18 slaughterhouses in Iran. The mean ±s.d.for total length of large and small hooks were 174.1 ± 6.4 and 116.7 ± 5.4µm, respectively. CO1 and 12S rRNA sequence analysis showed 11 and nine haplotypes, respectively. The level of pairwise nucleotide variations between individual haplotypes of CO1 and 12S rRNA genes were 0.3–1.1 and 0.2–1.0%, respectively. Level of nucleotide variation in CO1 and 12S rRNA betweenT. ovishaplotypes from present study and eight otherTaeniaspecies was found to be 11.3–17.8 and 5.3–16.3%, respectively. Phylogenetic analysis clustered allT. ovisisolates into a single clade comprised of the all CO1 and 12S rRNA haplotypes. CO1 nucleotide difference betweenT. ovis ovisandT. asiaticawas 13.6% that is lesser than the corresponding difference betweenT. ovis ovisandT. ovis krabbei, warranting the designation of two separate species asT. ovisandT. krabbei. Interclass correlation coefficients showed that there was no significant association between rostellar hook length variation and the variability of the mitochondrial genes.

Molecular and morphological characterization of the tapeworm Taenia hydatigena (Pallas, 1766) in sheep from Iran

Although Taenia hydatigena is one of the most prevalent taeniid species of livestock, very little molecular genetic information exists for this parasite. Up to 100 sheep isolates of T. hydatigena were collected from 19 abattoirs located in the provinces of Tehran, Alborz and Kerman. A calibrated microscope was used to measure the larval rostellar hook lengths. Following DNA extraction, fragments of cytochrome c oxidase 1 (CO1) and 12S rRNA genes were amplified by the polymerase chain reaction method and the amplicons were subjected to sequencing. The mean total length of large and small hooks was 203.4 μm and 135.9 μm, respectively. Forty CO1 and 39 12S rRNA sequence haplotypes were obtained in the study. The levels of pairwise nucleotide variation between individual haplotypes of CO1 and 12S rRNA genes were determined to be between 0.3–3.4% and 0.2–2.1%, respectively. The overall nucleotide variation among all the CO1 haplotypes was 9.7%, and for all the 12S rRNA haplotypes it was 10.1%. A significant difference was observed between rostellar hook morphometry and both CO1 and 12S rRNA sequence variability. A significantly high level of genetic variation was observed in the present study. The results showed that the 12S rRNA gene is more variable than CO1.

Rostellar hook morphology of larval Echinococcus granulosus isolates from the Indian buffalo and Iranian sheep, cattle and camel

Isolates of Echinococcus granulosus from the Indian buffalo and Iranian sheep, cattle and camels were characterized on the basis of rostellar hook morphology of the protoscolices. Results obtained indicated phenotypic polymorphism among parasites isolated from different host species. Isolates from buffalo are morphologically quite different from those of the more common sheep and cattle isolates and may represent a different strain, adapted to buffalo. In the Sari region of northern Iran, two morphologically distinct forms of E. granulosus, one in sheep and one in camels, were identified. Total length and handle length of both large and small hooks were considered the most variable characteristics which could be used not only for differentiating parasite isolates from different host species but also the origin of infection in the definitive host. We therefore suggest that larval hook morphology may be considered as a valid criterion for the identification of E. granulosus strains in Iran.

Genetic diversity and genetic differentiation in Echinococcus granulosus (Batsch, 1786) from domestic and sylvatic hosts on the mainland of Australia

Enzyme electrophoresis was used to examine genetic variation within and between populations of Echinococcus granulosus from domestic and sylvatic hosts in western and eastern Australia. Substantial genetic diversity was found within all populations. There was no evidence, however, of genetic differentiation between populations from different hosts or geographic areas. When isolates were grouped into previously described domestic or sylvatic strains on the basis of rostellar hook morphology, most (94%) of the genetic variation occurred within, rather than between strains. These results conflict with the currently accepted theory of separate domestic and sylvatic strains of E. granulosus on the mainland of Australia.

Rostellar hook morphology ofEchinococcus granulosus(Batsch, 1786) from natural and experimental Australian hosts, and its implications for strain recognition

An analysis of the rostellar hooks of Australian isolates ofEchinococcus granulosusrevealed that there was less variation in larval (metacestode) than adult characters and that metacestode characters could be measured directly from adult worms. A factor analysis indicated that two factors, one representing a contrast between number of hooks and their length, and the other representing blade lengths, were sufficient to account for 87.5% of the variance in metacestode hook measurements. These results indicate that rostellar hook morphology is not useful for discriminating strains ofE. granulosusin Australia. The Tasmanian and mainland domestic strains were found to be indistinguishable using rostellar morphology. Although many of the isolates from sylvatic hosts differed from those from domestic hosts, there was not a clear separation as would be expected if two distinct strains existed. Evidence was presented to show that the morphological differences seen in sylvatic hosts could be attributed to host-induced effects, and that the previously accepted existence of two mainland strains should be investigated further.

Histogenesis of the rostellum of Taenia crassiceps (Zeder, 1800) (Cestoda), with special reference to hook development

Histogenesis of the rostellum of Taenia crassiceps is described. The syncytial tegument and various cells take an active part in this differentiation. The increase in number of these cells as well as nuclei associated with the tegument, and changes in their relationship with one another, dominate the process. A specialized portion of the tegument termed the "hook organ" and its function in rostellar hook formation is considered. Rostellar hooks are produced de novo and not from fused microtriches as stated by some. When the hook organ is most active it is not separated from the underlying tissues by the subtegumental circular and longitudinal muscle layer as is the tegument of the adjacent bladder wall. When the rostellar hooks are fully differentiated the hook organ becomes an inner and outer ring of receptacles each with its own hook.

THE COMPARATIVE BIOLOGY AND MORPHOLOGY OF TAENIA OVIS AND TAENIA KRABBEI, WITH OBSERVATIONS ON THE DEVELOPMENT OF T. OVIS IN DOMESTIC SHEEP

The geographic distribution of infections of skeletal muscle and cardiac cysticerci, possibly T. krabbei, in North American Cervidae is related where pertinent to the geographic distribution of T. ovis in domestic sheep. Experiments show that T. krabbei and T. ovis are biologically distinct but morphologically indistinguishable.The T. ovis embryo migrates through the muscle tissue forming a streak when only a few days old. Where the host response is not inhibitory, complete differentiation and rostellar hook development occur about 56 days after exposure. Many parasites are destroyed by the host as differentiating embryos, before rostellar hooks have begun to develop, during hook development, but only rarely after the cyst is differentiated completely. Viable cysts are surrounded by only a thin fibrous wall. Dead and viable cysts occur non-systematically and show no relationship to any particular muscles, body area, or body system.