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Implementation of an extended ZINB model in the study of low levels of natural gastrointestinal nematode infections in adult sheep

Atlija, M., Prada, Joaquin, Gutierrez-Gil, B., Rojo-Vázquez, F.A., Stear, M.J., Arranz, J.J. and Martínez-Valladares, M. (2016) Implementation of an extended ZINB model in the study of low levels of natural gastrointestinal nematode infections in adult sheep BMC Veterinary Research, 12 (1).

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Abstract

Background: In this study, two traits related with resistance to gastrointestinal nematodes (GIN) were measured in 529 adult sheep: faecal egg count (FEC) and activity of immunoglobulin A in plasma (IgA). In dry years, FEC can be very low in semi-extensive systems, such as the one studied here, which makes identifying animals that are resistant or susceptible to infection a difficult task. A zero inflated negative binomial model (ZINB) model was used to calculate the extent of zero inflation for FEC; the model was extended to include information from the IgA responses. Results: In this dataset, 64 % of animals had zero FEC while the ZINB model suggested that 38 % of sheep had not been recently infected with GIN. Therefore 26 % of sheep were predicted to be infected animals with egg counts that were zero or below the detection limit and likely to be relatively resistant to nematode infection. IgA activities of all animals were then used to decide which of the sheep with zero egg counts had been exposed and which sheep had not been recently exposed. Animals with zero FEC and high IgA activity were considered resistant while animals with zero FEC and low IgA activity were considered as not recently infected. For the animals considered as exposed to the infection, the correlations among the studied traits were estimated, and the influence of these traits on the discrimination between unexposed and infected animals was assessed. Conclusions: The model presented here improved the detection of infected animals with zero FEC. The correlations calculated here will be useful in the development of a reliable index of GIN resistance that could be of assistance for the study of host resistance in studies based on natural infection, especially in adult sheep, and also the design of breeding programs aimed at increasing resistance to parasites. © 2016 The Author(s).

Item Type: Article
Divisions : Faculty of Health and Medical Sciences
Authors :
NameEmailORCID
Atlija, M.
Prada, Joaquinj.prada@surrey.ac.uk
Gutierrez-Gil, B.
Rojo-Vázquez, F.A.
Stear, M.J.
Arranz, J.J.
Martínez-Valladares, M.
Date : 2016
DOI : 10.1186/s12917-016-0723-7
Uncontrolled Keywords : Egg count, Gastrointestinal nematodes, IgA, Prevalence, Sheep, ZINB
Additional Information : Unmapped bibliographic data: C7 - 97 [EPrints field already has value set] LA - English [Field not mapped to EPrints] J2 - BMC Vet. Res. [Field not mapped to EPrints] C2 - 27283535 [Field not mapped to EPrints] AD - Universidad de León, Departamento de Producción Animal, Campus de Vegazana s/n, León, 24071, Spain [Field not mapped to EPrints] AD - University of Glasgow, Institute of Biodiversity, Animal Health and Comparative Medicine, Bearsden Road, Glasgow, G61 1QH, United Kingdom [Field not mapped to EPrints] AD - Princeton University, Department of Ecology and Evolutionary Biology, Princeton, NJ 08540, United States [Field not mapped to EPrints] AD - Instituto de Ganadería de Montaña, CSIC-ULE, Grulleros, León, 24346, Spain [Field not mapped to EPrints] AD - Universidad de León, Departamento de Sanidad Animal, Campus de Vegazana s/n, León, 24071, Spain [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints] M3 - Article [Field not mapped to EPrints]
Depositing User : Rebecca Cooper
Date Deposited : 03 Jan 2019 09:23
Last Modified : 07 Jan 2019 14:07
URI: http://epubs.surrey.ac.uk/id/eprint/850093

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