A multi-event capture-recapture analysis of Toxoplasma gondii seroconversion dynamics in farm cats - PubMed (original) (raw)

A multi-event capture-recapture analysis of Toxoplasma gondii seroconversion dynamics in farm cats

Julie Alice Simon et al. Parasit Vectors. 2018.

Abstract

Background: Domestic cats play a key role in the epidemiology of the parasite Toxoplasma gondii by excreting environmentally-resistant oocysts that may infect humans and other warm-blooded animals. The dynamics of Toxoplasma gondii seroconversion, used as a proxy for primo-infection dynamics, was investigated in five cat populations living on farms.

Methods: Serological tests on blood samples from cats were performed every three months over a period of two years, for a total of 400 serological tests performed on 130 cats. Variations in seroconversion rates and associated factors were investigated using a multi-event capture-recapture modelling approach that explicitly accounted for uncertainties in cat age and serological status.

Results: Seroprevalence varied between farms, from 15 to 73%, suggesting differential exposure of cats to T. gondii. In farms with high exposure, cats could become infected before reaching the age of six months. Seroconversion rates varied from 0.42 to 0.96 seroconversions per cat per year and were higher in autumn and winter than in spring and summer.

Conclusion: Our results suggest inter-farm and seasonal variations in the risks of exposure to T. gondii oocysts for humans and livestock living on farms. The paper also discusses the role of young cats in the maintenance of environmental contamination by T. gondii oocysts on farms.

Keywords: Blotting paper; Capture-recapture; Domestic cats; Infection dynamics; Misclassification; Multi-event modelling; Serological titres; Toxoplasmosis.

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Conflict of interest statement

All the cat experiments in this study were approved by the French Ministry of National Education, Higher Education and Research and by the Ethics Committee of Champagne-Ardenne (Approval no. 5387) and were conducted according to French regulations on ethics in animal experimentation. Each owner of the respective farms gave consent to perform the study on the property.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Fig. 1

Location of the five study sites in the Ardennes region in France

Fig. 2

Fig. 2

Diagrams of the biological process (a) and the observational process (b) used in multi-event CMR models. The diagram a describes the initial states and the conditional transitions between states from one sampling session to the next and the diagram b describes the recorded events for each cat at a given sampling session. The names of parameters corresponding to transitions and events and the effects tested on these parameters are indicated under each step of the processes. Effects written in bold correspond to the effects considered in the initial model. The detailed matrices used to estimate each parameter are presented in Additional file 1

Fig. 3

Fig. 3

Seroconversion rates estimated by the best retained model. The model considers the interactive effects of cats age (≤ 6 months and > 6 months) and population (farms A, B, C, F and T) and an additive effect of season (Spring, Summer, Autumn and Winter). Error bars represent standard errors

Fig. 4

Fig. 4

Occurrence probabilities of antibody titre classes in cats assigned as seropositive according to the best retained model. The model considers the effect of farms and sampling sessions. The white bars represent sessions before methodological improvements in sampling, and the black bars represent sessions after these improvements. Error bars represent standard error

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