Poster Presentation Australian and New Zealand Metabolomics Conference 2018

Investigating effects of gastrointestinal nematodes on earthworms using a metabolomic approach (#105)

Linda M Samuelsson 1 , Dave Leathwick 2 , Tania Waghorn 2 , Alec Mackay 3 , Nicole Schon 4
  1. Food Nutrition & Health Team, AgResearch Ltd, Palmerston North, New Zealand
  2. Animal Health Team, Animal Science Group, AgResearch Ltd, Palmerston North, New Zealand
  3. Farm Systems Team, Farm Systems & Environment Group, AgResearch Ltd, Palmerston North, New Zealand
  4. Soil Biology Team, Forage Science Group, AgResearch Ltd, Lincoln, New Zealand

Introduction: Gastrointestinal nematodes in livestock are detrimental to animal health, reducing animal growth rates and costing New Zealand’s pastoral sector $700 million dollars a year alone. While anthelmintic drenches can reduce parasite numbers, increasing resistance to anthelmintics worldwide may reduce their efficiency. Hence, finding alternatives for reducing parasitic nematodes in livestock are essential.

Previous studies have shown that parasitic nematode numbers are reduced when earthworms are present in the soil. The mechanism for this reduction is yet unknown but could be caused by either digestion in the earthworm gut or simply by mechanical abrasion from soil particles during passage through the earthworm gut. The objectives of this study was to A) determine gastrointestinal nematode mortality during passage through the earthworms gut and B) measure metabolites in the earthworms to gain insight into the mechanism of nematode mortality.

Methods: Earthworms (Lumbricus rubellus) were divided into two groups and fed either sheep dung infected with the gastrointestinal nematode Haemonchus contortus or non-infected sheep dung for 8 days. Nematode numbers were counted in earthworm casts. Polar metabolites were extracted from the posterior part of the earthworms and analysed by 1H NMR spectroscopy.

Results: Earthworms caused mortality of gastrointestinal nematodes during their passage through the earthworm gut: Nematode numbers in earthworm casts from feeding on infected sheep dung were reduced by 97-100%. Thirty metabolites were identified and quantified in the posterior earthworm extracts with alanine, succinate, glutamate, glutamine and glucose being the most abundant. No statistically significant difference in metabolite concentrations were found between earthworms fed infected and non-infected dung. These results suggest that the mechanism causing nematode mortality in the earthworm gut is likely to be of a mechanical nature (e.g. abrasion) rather than biochemical since metabolites in the host were not affected.