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

Atlija, M., Prada Jimenez de Cisneros, J.M., Gutiérrez-Gil1, 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, 97. (doi:10.1186/s12917-016-0723-7) (PMID:27283535) (PMCID:PMC4901511)

[img]
Preview
Text
119910.pdf - Published Version
Available under License Creative Commons Attribution.

1MB

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.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Atlija, Miss Marina and Prada Jimenez de Cisneros, Dr Joaquin and Stear, Professor Michael
Authors: Atlija, M., Prada Jimenez de Cisneros, J.M., Gutiérrez-Gil1, B., Rojo-Vázquez, F.A., Stear, M.J., Arranz, J.J., and Martínez-Valladares, M.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Journal Name:BMC Veterinary Research
Publisher:BioMed Central Ltd
ISSN:1746-6148
ISSN (Online):1746-6148
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in BMC Veterinary Research 12:97
Publisher Policy:Reproduced under a Creative Commons License

University Staff: Request a correction | Enlighten Editors: Update this record

Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
629831The influence of selective breeding on MHC diversityMichael StearBiotechnology and Biological Sciences Research Council (BBSRC)BB/L004070/1RI BIODIVERSITY ANIMAL HEALTH & COMPMED