Info

Human

United States

G9 (?)

Human

Poland

Source: Modified from Ref. [2].

Source: Modified from Ref. [2].

Confirmation of species identity was obtained by phy-logenetic analysis (Fig. 1) using data from the complete mitochondrial genomes recently obtained for both strains. Of public health significance is the fact that the sheep strain is infective to humans but, probably, noninfective to horses. The horse strain appears to be poorly infective to sheep and may be noninfective to humans. This is borne out by the DNA data as, to date, the horse strain (G4 genotype) has not been reported in sheep or humans, and the sheep strain (G1 genotype) has not been identified in horses.

It has been recognized for some time that E. granulosus is maintained in two cycles of transmission on mainland Australia. One principally involves domestic sheep, whereas the other involves numerous species of macropod marsupials (kangaroos and wallabies). There is interaction between these cycles through a range of carnivores (domestic dogs, feral dogs, dingoes, and red foxes) which are definitive hosts. Early evidence led to their proposed designation as distinct strains but subsequent molecular analysis indicates that only the common sheep strain is present. In biological, epidemiological, and molecular features the common sheep strain can be regarded as homogeneous except in Tasmania where morphological distinctiveness, a significantly shortened prepatency period, and molecular evidence have indicated that a variant of the common E. granulosus genotype (designated genotype G2) occurs there. The G2 genotype is also

Fig. 1 Inferred relationships among species and genotypes of Echinococcus, using Taenia crassiceps as an outgroup. (From Ref. [9].) Concatenated sequences of mitochondrial DNA genes [atp6, nad1 (partial) and cox1 (partial)] were analysed. A distance matrix was constructed from inferred amino acid (aa) sequences (alignment was 451 aa long with 168 variable aa sites 67 aa parsimony-informative sites) using a Poisson correction for multiple hits and the tree constructed using the minimum evolution approach. Five hundred bootstrap resamplings were carried out. Branches with bootstrap support values less than 50% are indicated with an asterisk. EgrGl, EgrG4, EgrG6-EgrG8 are the different genotypes of E. granulosus. Units on scale bar: changes per site. The branches indicated by an asterisk were supported by fewer than 50% of the resampled data sets and therefore should be regarded as poorly supported. It is clear that EgrG4, EgrGl, E. vogeli, and E. oligarthrus are almost equidistant from each other in terms of mt sequences. Furthermore, the E. granulosus G1 and G4 genotypes are also almost equidistant from the G6-8 genotype cluster, although there is some structure in this latter group. E. multilocularis appears as basal within the genus, but again the branch placing it there is rather poorly supported. Given this, recognition of the sheep-dog (G1 genotype) and the horse-dog (G4 genotype) strains (and possibly also the G6-8 genotypes) as separate species is appropriate. The discrete nature of the two forms is quite clear and the molecular and phylogenetic evidence from this and previous studies suggests the case for reinstatement of their formal taxonomic status as subspecies/species is now proven.

Fig. 1 Inferred relationships among species and genotypes of Echinococcus, using Taenia crassiceps as an outgroup. (From Ref. [9].) Concatenated sequences of mitochondrial DNA genes [atp6, nad1 (partial) and cox1 (partial)] were analysed. A distance matrix was constructed from inferred amino acid (aa) sequences (alignment was 451 aa long with 168 variable aa sites 67 aa parsimony-informative sites) using a Poisson correction for multiple hits and the tree constructed using the minimum evolution approach. Five hundred bootstrap resamplings were carried out. Branches with bootstrap support values less than 50% are indicated with an asterisk. EgrGl, EgrG4, EgrG6-EgrG8 are the different genotypes of E. granulosus. Units on scale bar: changes per site. The branches indicated by an asterisk were supported by fewer than 50% of the resampled data sets and therefore should be regarded as poorly supported. It is clear that EgrG4, EgrGl, E. vogeli, and E. oligarthrus are almost equidistant from each other in terms of mt sequences. Furthermore, the E. granulosus G1 and G4 genotypes are also almost equidistant from the G6-8 genotype cluster, although there is some structure in this latter group. E. multilocularis appears as basal within the genus, but again the branch placing it there is rather poorly supported. Given this, recognition of the sheep-dog (G1 genotype) and the horse-dog (G4 genotype) strains (and possibly also the G6-8 genotypes) as separate species is appropriate. The discrete nature of the two forms is quite clear and the molecular and phylogenetic evidence from this and previous studies suggests the case for reinstatement of their formal taxonomic status as subspecies/species is now proven.

present in Argentina, possibly having been introduced with Merino sheep exported from Australia to Argentina.[10]

Camel-Dog (G6 Genotype) Strain

Two distinct strains of E. granulosus have been identified by molecular methods in Kenya. The sheep strain of E. granulosus occurs in sheep, cattle, goats, and man, with the camel strain (G6 genotype) infecting camels and occasionally goats. DNA analysis has clearly indicated that the camel-dog strain (G6 genotype) of E. granulosus as well as the cosmopolitan, common sheep strain (G1 genotype) also occurs in Iran and China. DNA studies have indicated that the camel strain is infectious to humans and circulates between intermediate hosts including camels and cattle in Mauritania; if the sheep strain is present, it is rarely found there.

As well as Mauritania, molecular studies of E. granulosus from Argentina, Iran, and Nepal have reported the presence of the G6 genotype in several human subjects. This has potentially important implications for public health and implementation of hydatid control programs where the camel strain is involved in E. granulosus transmission. The camel strain has a shorter maturation time in dogs than the common sheep strain which is the form generally associated with human infection.

Bovine Strain (G5 Genotype)

Until the early 1990s, all surgically obtained human isolates of E. granulosus examined by isoenzyme and DNA analysis conformed to the common domestic sheep strain. However, a partly calcified hydatid cyst removed from an 11-year-old Dutch boy typed by PCR/RFLP analysis and cox1 and nad1 sequence comparisons with known genotypic sequences showed clearly that the patient was infected, not with the sheep strain, but with the genetically distinct bovine or cattle strain (G5 genotype) of E. granulosus. This strain has also been shown to infect humans in Argentina.[11] Thus, in regions where the bovine strain occurs, cattle may act as reservoirs of human infection. As is evident from scrutiny of Table 1, DNA analysis indicates that several E. granulosus genotypes (G2, G5, G6, G7, G8, and G9) are infective to humans.

Pig-Dog Strain (G7 Genotype)

Analysis of E. granulosus from Polish patients indicated they were not infected with the common sheep strain (G1 genotype) of E. granulosus. Instead, the isolates shared similar DNA sequence with the previously characterized pig-dog strain (G7) genotype but exhibited some clear differences. Accordingly, it was proposed that these human isolates represented a distinct E. granulosus genotype (designated G9). Subsequent studies of human and pig isolates from Poland, Slovakia, and Ukraine failed to confirm the existence of this genotype but have provided evidence for the almost exclusive presence of the G7 genotype.[12] Confirmation of the existence of the G9 genotype and identification of the reservoir(s) of human hydatid disease in Poland and other countries in Central and East Europe remain unresolved.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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