Time series analysis of bovine venereal diseases in La Pampa, Argentina.

Leonardo L Molina,Javier Caballero-Villalobos,Antón García,José Perea,Elena Angón,Ricardo H Moralejo,Michele Tizzoni

doi:10.1371/journal.pone.0201739

Leonardo L Molina, Javier Caballero-Villalobos + Show 5 more

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https://doi.org/10.1371/journal.pone.0201739

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Abstract

The venereal diseases bovine trichomoniasis (BT) and bovine genital campylobacteriosis (BGC) cause economic losses in endemic areas like La Pampa province in Argentina where beef cattle are usually extensively managed. This study used data compiled between 2007 and 2014 by a Provincial Program for the Control and Eradication of venereal diseases in order to develop and analyze retrospective models of time series for BT and BGC. Seasonality and long-term trend were explored with decomposition and simple regression methods. Autoregressive Integrated Moving Average models (ARIMA) were used to fit univariate models for the prevalence and persistence of BT and BGC. Autoregressive Integrated Moving Average with Explanatory Variable models (ARIMAX) were used to analyze the association between different time series, replacement entries and herd samplings. The prevalence and persistence of BT and BGC have decreased from 2007 to 2014. All the BT and BGC time series are seasonal and their long-term trend is decreasing. Seasonality of BT and BGC is similar, with higher rates of detection in autumn-winter than is spring-summer. Prevalence and persistence time series are correlated, indicating their changes are synchronic and follow a similar time pattern. Prevalence of BT and BGC showed the best fitting with the ARIMA (0,0,1)(0,1,1)12 model. While for persistence of BT and BGC, the best adjustment was with the same model with no seasonal difference where the current number of cases depends on the moving averages of the month and the previous season. Including covariates improve the fitting of univariate models, in addition, estimations using ARIMAX models are more precise than using ARIMA models. The time distribution of the samplings could be increasing the false negative ratio. According to the obtained results, the ARIMA and ARIMAX models can be considered an option to predict the BT and BGC prevalence and persistence in La Pampa (Argentina).

Highlights

Bovine trichomoniasis (BT) and bovine genital campylobacteriosis (BGC) are two venereal diseases caused respectively by Tritrichomonas foetus protozoan and the Gram (-) Campylobacter fetus subspecies venerealis [1, 2]
Seasonal indices were obtained from the original time series and reveal the seasonality of the testing of herds, replacement entries, BT and BGC prevalence and persistence (Table 1)
ARIMAX models obtained smaller Akaike information criterion (AIC) and Schwartz Bayesian criterion (SBC) than their corresponding univariate Autoregressive Integrated Moving Average models (ARIMA) models, which indicates that the fitting performance improved with the inclusion of the covariate variables

Summary

Introduction

Bovine trichomoniasis (BT) and bovine genital campylobacteriosis (BGC) are two venereal diseases caused respectively by Tritrichomonas foetus protozoan and the Gram (-) Campylobacter fetus subspecies venerealis [1, 2]. Both agents are transmitted during coitus and colonize the reproductive tract of cows and bulls. There is neither effective treatment nor vaccination, which makes even more difficult to implement control plans in the endemic zones [7] Both diseases are still associated to economic losses due to breeding failure

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