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Genotypic and phenotypic characterization of Haemonchus contortus in Sweden

Troell, Karin (2006). Genotypic and phenotypic characterization of Haemonchus contortus in Sweden. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2006:36
ISBN 91-576-7085-4
[Doctoral thesis]

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Haemonchus contortus is a blood-sucking nematode of the abomasum in small ruminants. It is responsible for extensive losses and huge animal welfare problems globally. This thesis is based on four publications with the overall aim to characterize H. contortus from Sweden, and includes both genotypic and phenotypic aspects of this parasite. This nematode has by tradition been considered a tropical parasite due to the climatic requirements for its preparasitic lifestages. Its development and survival is dependent on temperature and humidity, and the window of opportunity to complete its life cycle in Sweden is limited. The species status of Haemonchus in Sweden was investigated by comparing the genetic differences in the internal transcribed spacers (ITS-1 and ITS-2) of the ribosomal DNA (rDNA) in worms from Sweden and Kenya. As no fixed differences were found between these isolates they are considered to be distinct populations of the same species, H. contortus. The population structure of H. contortus at a global level was studied by analysing the genetic variability using both amplified fragment length polymorphism (AFLP) and nad4 sequences of the mitochondrial genome. The results show that both the genetic variation and the genetic structure were high between the different isolates, and that populations from each continent mostly formed monophyletic groups in the phylogenetic analysis. The thesis also includes experimental infection studies performed with both fresh and cold- treated infective larvae of either Kenyan or Swedish origin. These investigations covered a range of phenotypic traits, to search for any potential adaptations the parasite might have in order to survive Sweden’s cold temperate climate. In addition, several studies were performed on the development and long-term survival of the parasite in climatic chambers, as well as studies on the overwinter survival of H. contortus on pastures in Sweden. The results show that this parasite can survive winters on pastures. However, the survival capacity was very low and is of limited significance in the transmission between grazing-seasons. Taken together, the results presented in this thesis indicate that H. contortus has a large phenotypic plasticity rather than having undergone any evolutionary adaptation.

Authors/Creators:Troell, Karin
Title:Genotypic and phenotypic characterization of Haemonchus contortus in Sweden
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :May 2006
Number of Pages:52
ALLI. Troell, K., Mattsson, J.G., Aldeborn, A. & Höglund, J. 2003. Pyrosequencing™ analysis identifies discrete populations of Haemonchus contortus from small ruminants. International journal for parasitology 33, 765-771. II. Troell, K., Engström, A., Morrison, D.A., Mattsson, J.G. & Höglund, J. 2006. Global patterns reveal strong population structure in Haemonchus contortus, a nematode parasite of domesticated ruminants (submitted). III. Troell, K., Tingstedt, C. & Höglund, J. 2006. Phenotypic characterization of Haemonchus contortus: a study of isolates from Sweden and Kenya in experimentally infected sheep. Parasitology, 132, 403-409. IV. Troell, K., Waller, P. & Höglund, J. 2005. The development and overwintering survival of free-living larvae of Haemonchus contortus in Sweden. Journal of helminthology 79, 373-379.
Place of Publication:Uppsala
ISBN for printed version:91-576-7085-4
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:haemonchus contortus, nematoda, disease transmission, sheep, goats, adaptation, phenology, climatic factors, environmental factors, sweden, kenya
Keywords:Haemonchus contortus, Sweden, adaptation, phenotypic plasticity, acclimation, overwinter survival, parasitic nematode, sheep
Permanent URL:
ID Code:1145
Department:(VH) > Dept. of Biomedical Sciences and Veterinary Public Health
Deposited By: Karin Troell
Deposited On:23 May 2006 00:00
Metadata Last Modified:02 Dec 2014 10:09

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