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  Morphological and genetic diversity of whipworms (Trichuris spp.) recovered from pigs and humans
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 Ophav:
Nissen, Sofie1, Forfatter
Nejsum, Peter1, Vejleder
Christensen, Henrik1, Vejleder
Thamsborg, Stig Milan1, Vejleder
Tilknytninger:
1Det Biovidenskabelige Fakultet, København, Danmark, diskurs:18              
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 Abstract: The two nematodes, Trichuris suis and Trichuris trichiura are believed to be two separate but closely related species, i.e. being reproductive isolated but difficult to distinguish by morphological characters. In areas where humans and pigs live in close proximity a zoonotic transmission might be a hazard. Furthermore, eggs of T. suis populations have potential in treating patients with autoimmune-related diseases in the western part of the world. In both cases there is a strong need for knowledge on the genetic diversity within and between Trichuris spp. in the two hosts, which was the aim of the present study. Sympatric worm material isolated from 10 humans and 5 pigs in Uganda supplemented with T. suis from Tanzania, Denmark and USA and T. trichiura from England, was obtained. Based on morphology, worms from the two hosts could only be discriminated by the length of the male spicule (student t-test, p<0.001). The second internal transcribed spacer (ITS-2) in the ribosomal DNA was amplified by PCR and cloned. Between 1 and 6 clones from 20 worm were sequenced, which resulted in a total of 94 sequences (49 human-derived and 45 pig-derived) that could be allocated into as many as 56 different haplotypes. A very large intra-individual variation was found within the human-derived sequences (0.2 – 45.0%) compared to the pig derived sequences (0.2 – 1.4%). This was due to the fact that the human-derived worms consisted of two main ITS-2 sequence types; one of them being unique (69% of the human-derived sequences, consensus sequence 481 nucleotides long) and the other being identical to the sequence type found in pig-derived worms (31% of the human-derived worms, consensus sequence 531 nucleotides long).
The phylogenetic relationship between ITS-2 sequences for nine Trichuris spp. was established using neighbor joining based on sequences obtained from GenBank and on consensus sequences made in the present study. The topology of the tree seemed robust and the clades in the tree reflected the hosts’ physiology.
The molecular results indicated that the whipworms found in pigs belong to a genetically distinct species (T. suis) whereas the whipworms in humans showed a considerably larger variability either related to ancestral polymorphism or more recent cross-breeding between T. trichiura and T. suis.
 Abstract: Piskeorme i mennesker og grise, Trichuris suis og Trichuris trichiura, er længe blevet anset for at være to tæt beslægtede, men dog forskellige arter. De to rundorme anses for at være adskilte reproduktivt, men er svære at skelne fra hinanden morfologisk. I den tredje verden, hvor grise og mennesker lever tæt sammen kan en zoonotisk overførsel af T. suis være en potentiel fare for mennesker. Ydermere ser T. suis æg ud til at være lovende i behandlingen af auto-immune sygdomme, som til stadighed bliver mere udbredte i den vestlige verden. Der er således to hovedårsager til, at der er behov for viden om den genetiske diversitet indenfor og mellem de to Trichuris arter, som det var formålet at undersøge i dette studie. Sympatrisk materiale, der var isoleret fra 10 mennesker og 5 grise fra det samme geografiske område i Uganda suppleret med T. suis fra Tanzania, Danmark og USA og T. trichiura, blev indsamlet. Det eneste morfologiske træk, der adskilte de to typer orme var længden af hannernes spikel (student t-test, p&gt; 0,001). Et ikke-kodende område i det ribosomale DNA, ITS-2, blev opformeret vha. PCR og klonet. DNA fra mellem en til seks kloner fra i alt 20 orm blev sekvenseret, hvilket resulterede i 94 sekvenser (49 fra orm isoleret fra mennesker og 45 fra orm isoleret fra grise). De 94 sekvenser faldt indenfor 56 forskellige haplotyper. Orm isoleret fra mennesker udviste en meget stor intra-individuel variation (0,2 – 45,0 %). Dette kunne tilskrives det faktum, at der var to overordnede sekvenstyper indenfor ormene isoleret fra mennesker. Den ene sekvenstype var unik for orm afledt fra mennesker (69% af sekvenser fra orm, der stammede fra mennesker, konsensussekvens 481 nukleotider lang), den anden type var identisk med den type, der fandtes i orm isoleret fra grise (31% af sekvenser fra orm, der stammede fra mennesker, konsensussekvens 534 nukleotider lang). Slægtskabet mellem 8 ITS-2 sekvenser fra Trichuris spp. fra GenBank samt for de to konsensussekvenser lavet i dette studie blev bestemt vha. neighbor joining. Træets topologi virkede robust og grupperingen af ormene i tre grupper afspejlede i høj grad værternes fysiologi. De molekylære resultater i dette studie indikerer, at piskeormene fundet i grise tilhører en genetisk særskilt art (T. suis) hvorimod ormene fundet i mennesker viste en langt større variation, der enten skyldes en nedarvet polymorfi eller mere nutidige krydsninger mellem T. trichiura og T. suis.
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Bogmærk denne post: https://diskurs.kb.dk/item/diskurs:12779:2
 Type: Speciale
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Sprog: English - eng
 Datoer: 2009
 Sider: 63 pages
 Publiceringsinfo: København, Danmark : Institut for Veterinær Sygdomsbiologi
 Indholdsfortegnelse: -
 Note: Master programme in parasitology, Parasitology
 Type: Speciale
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