Mapping environmental factors to Fasciola hepatica at farm-level

Qin, Qi (2019) Mapping environmental factors to Fasciola hepatica at farm-level. MSc(R) thesis, University of Glasgow.

Abstract

Fascia/a hepatica is a common parasite, which affects sheep and cattle. In past decades, due to wet weather and the increasing temperature in summer and early autumn, the risk of sheep and cattle infection by F. hepatica has significantly increased, and it has also caused enormous economic loss. Th·e distribution of F.-hepatica is profoundly affected by environmental conditions including precipitation, temperature, soil moisture, and vegetation type and can be predicted on a regional scale by environmental data. In the UK, a large numnber of farms are small or medium­ sized, and the current-parasite forecast system works on a national scale postal area scales, which is too broad to provide a precise forecast or enable the development of within-farm management strategies. Hence, there is a need to map the environment data to F. hepatica at the farm level.

This study examined the relationships between F. hepatica and environmental factors at the within-farm and within-field levels, useing earth observation techniques and geographic infor­mation systems (GIS) to analyse the potential contribution of environmental factors to the den­sity of F. hepatica on pasture. Five study fields within two farms in Scotland, Cochno and Dumgoyne, were used i this study. Nine variables grouped within four categories were used to describe the environmental conditions: 1) remote sensing indices: normalized difference water index (NDWI) and normalized difference vegetation index (NOVI); 2) soil properties: soil moisture and soil temperature; 3) topographical factors: elevation, slope, and aspect; 4) grazing grass: grass height and grass weight. Two variables were used to describe the intensity of F. hep­atica in pasture grass: count of metacercarial cysts and yield of metacercariae (the number of metacercarial cysts per gram pasture). Univariate negative binomial regression models of each environment factors were built against the number of metacercariae per 0.1 gram. Subsequently, the significant variables were used in a multivariate regression model. The environmental condi­tions were diverse among the five fields and the F. hepatica density also varied quite widely. The results of this study showed that there were strong associations among environmental variables. These associations result in complex interactions when modelling the environment to F. hep­atica. Relationships among environmental variables and metacercarial density measures were quite inconsistent. Although the NDVI, grass weight, soil moisture and slope in particular fields showed significant relationships with F. hepatica, the remote sensing indicators tested would not be useful for determining parasite concentrations within farm-level.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences
• Supervisor's Name: Barrett, Dr. Brian and Jonsson, Prof. Nicholas
• Date of Award: 2019
• Depositing User: Miss Qi Qin
• Unique ID: glathesis:2019-8726
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 Jun 2019 14:29
• Last Modified: 05 Mar 2020 21:31
• Thesis DOI: 10.5525/gla.thesis.8726
• URI: https://theses.gla.ac.uk/id/eprint/8726