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The complete nucleotide sequence of the mitochondrial (mt) DNA molecule of the liverfluke, Fasciola hepatica (phylum Platyhelminthes, class Trematoda, family Fasciolidae), was determined. It comprises 14462 bp, contains 12 protein-encoding, 2 ribosomal and 22 transfer RNA genes, and is the second complete flatworm (and the first trematode) mitochondrial sequence to be described in detail. All of the genes are transcribed from the same strand. Of the genes typically found in mitochondrial genomes of eumetazoans, only atp8 is absent. The nad4L and nad4 genes overlap by 40 nt. Most intergenic sequences are very short. Two larger non-coding regions are present. The longer one (817 nt) is located between trnG and cox3 and consists of 8 identical tandem repeats of 85 nt, rich in G and C, followed by 1 imperfect repeat. The shorter non-coding region (187 nt) exhibits no special features and is separated from the longer region by trnG. The gene arrangement resembles that of some other trematodes including the eastern Asian Schistosoma species (and cyclophyllidean cestode species) but it is strikingly different from that of the African schistosomes, represented by Schistosoma mansoni. The genetic code is as inferred previously for flatworms. Transfer RNA genes range in length from 58 to 70 nt, their products producing characteristic 'clover leaf' structures, except for tRNA(S(UNC)) and tRNA(S(AGN)) lacking the DHU arm.

Unlike other members of the genus, Echinococcus granulosus is known to exhibit considerable levels of variation in biology, physiology and molecular genetics. Indeed, some of the taxa regarded as 'genotypes' within E. granulosus might be sufficiently distinct as to merit specific status. Here, complete mitochondrial genomes are presented of 2 genotypes of E. granulosus (G1-sheep-dog strain: G4-horse-dog strain) and of another taeniid cestode, Taenia crassiceps. These genomes are characterized and compared with those of Echinococcus multilocularis and Hymenolepis diminuta. Genomes of all the species are very similar in structure, length and base-composition. Pairwise comparisons of concatenated protein-coding genes indicate that the G1 and G4 genotypes of E. granulosus are almost as distant from each other as each is from a distinct species, E. multilocularis. Sequences for the variable genes atp6 and nad3 were obtained from additional genotypes of E. granulosus, from E. vogeli and E. oligarthrus. Again, pairwise comparisons showed the distinctiveness of the G1 and G4 genotypes. Phylogenetic analyses of concatenated atp6, nad1 (partial) and cox1 (partial) genes from E. multilocularis, E. vogeli, E. oligarthrus, 5 genotypes of E. granulosus, and using T. crassiceps as an outgroup, yielded the same results. We conclude that the sheep-dog and horse-dog strains of E. granulosus should be regarded as distinct at the specific level.

Based on hemagglutinin (HA) and neuraminidase (NA), influenza A virus is divided into 18 different HA (H1 to H18) and 11 NA types (N1 to N11), opening the possibility for reassortment between the HA and NA genes to generate new HxNy subtypes (where x could be any HA and y is any NA, possibly). In recent four years, since 2010, highly pathogenic avian influenza (HPAI) viruses of H5N1 subtype (HPAI A/H5N1) have become highly enzootic and dynamically evolved to form multiple H5 HA clades, particularly in China, Vietnam, Indonesia, Egypt, Cambodia, and Bangladesh. So far, after more than 10 years emerged in Vietnam (since late 2003), HPAI A/H5N1 is still posing a potential risk of causing outbreaks in poultry, with high frequency of annual endemics. Intragenic variation (referred to as antigenic drift) in HA (e.g., H5) has given rise to form numerous clades, typically marking the major timelines of the evolutionary status and vaccine application in each period. The dominance of genetically and antigenically diversified clade 2.3.2.1 (of subgroups a, b, c), clade 1.1 (1.1.1/1.1.2) and re-emergence of clade 7.1/7.2 at present, has urged Vietnam to the need for dynamically applied antigenicity-matching vaccines, i.e., the plan of importing Re-6 vaccine for use in 2014, in parallel use of Re-1/Re-5 since 2006. In this review, we summarize evolutionary features of HPAI A/H5N1 viruses and clade formation during recent 10 years (2004-2014). Dynamic of vaccine implementation in Vienam is also remarked.

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