Multiple linear regression model for forecasting Bluetongue disease outbreak in sheep of North-west agroclimatic zone of Tamil Nadu, India

G Selvaraju,A Balasubramaniam,M Geetha,D Rajendran,D Kannan

doi:10.5455/vetworld.2013.321-324

Abstract

Aim: A study was undertaken to develop a forecasting model for predicting bluetongue outbreaks in North-west agroclimatic zone of Tamil Nadu, India. Materials and Methods: Eleven bluetongue outbreaks were characterised by active and passive surveillances for a period of twelve years and used in this study. Meteorological data comprising of maximum and minimum temperatures, relative humidity, rainfall and wind speed were collected and used as the multiple predictor variables in the multiple liner regression model. Results: A multiple liner regression model was developed for the North-west zone of Tamil Nadu. Values of the dependant variables were less than or greater than one, and indicated remote or greater chances of bluetongue outbreaks respectively. The monthly mean maximum and minimum temperatures, relative humidity at 8.30 h and at 17.00 h IST, wind speed, and monthly total rainfall of 29.1 - 31.0°C, 20.1 - 22.0°C, 80.1 - 85.0%, 65.1 - 70.0%, 3.1 - 5.0 km/h and < 200 mm respectively, were identified as the ideal climatic conditions for increased numbers of bluetongue outbreaks in this zone. Conclusion: Based on the values obtained from the prediction model, stake holders can be warned timely through the media to institute suitable prophylactic measures against bluetongue, to avoid economic losses due to disease.

Highlights

Bluetongue (BT), an infectious and noncontagious disease of ruminants, is caused by BT virus (BTV), an RNA virus which belongs to the Orbivirus genus of the family Reoviridae [1]
Outbreak data: Bluetongue outbreak particulars were collected by both active and passive surveillances as per protocol prescribed by Martin [13]
It is concluded that based on results of the prediction model, stake holders may be continuously advised about possible future bluetongue outbreaks through the media, for instituting suitable prophylactic measures to avoid economic losses due to the disease

Summary

Introduction

Bluetongue (BT), an infectious and noncontagious disease of ruminants, is caused by BT virus (BTV), an RNA virus which belongs to the Orbivirus genus of the family Reoviridae [1]. The disease is characterized by mortality rates as high as 70% in highly susceptible sheep populations [2]. The estimated annual economic loss due to BT outbreak was Rs. 52 lakhs in TamilNadu and about $ 3 billion worldwide [3,4]. Bluetongue is endemic in Indian states of Tamil Nadu, Andhra Pradesh, Karnataka, Maharashtra, Gujarat, Rajasthan, Haryana, Himachal Pradesh and Jammu and Kashmir. In Tamil Nadu, 22 out of 23 districts were reported to be affected by the BTV [5]. More than 27 Culicoides species have been identified in India, and Culicoides imicola, C. peregrinus, C. oxystoma and C. brevitasis are the predominant species involved in the transmission of BT in Tamil Nadu [5, 6,7]

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