Analysis of Streptococcal Infection and Correlation with Climatic Factors in Cultured Tilapia Oreochromis spp. in Taiwan

Pei-Chih Liao,Yi-Lun Tsai,Pei-Chi Wang,Shu-Chu Liu,Shih-Chu Chen,Yao-Chung Chen

doi:10.3390/app10114018

Abstract

Tilapia (Oreochromis spp.), a prominent warm water food fish, is one of the major fish species grown in the aquaculture industry in south-east Asia. Tilapia can tolerate adverse water quality and other stressors, like diverse salinity and fluctuation of pH value, better than most other commercial aquaculture species. Environmental fluctuations are one of the main factors that affect the outbreak of infectious diseases in cultured tilapia. Cultured tilapia in Taiwan appears to be more susceptible to infections caused by Streptococci during the summer season. The present study emphasizes the Streptococcus spp. infection in tilapia in Taiwan and is the first study on the analysis of the potential impact of climate change on streptococcal infection in cultured tilapia in Asia. The data collected from the treatment and diagnosis system (TDS) of the aquatic animal diseases database from 2006 to 2015 were used to analyze the endemic streptococcal infection and the effect of climatic factors. Based on the results, the factor, average atmospheric pressure, is negatively correlated to streptococcal infection, while the other three, including average temperature, ultraviolet (UV) index, and rainfall, are positively correlated to streptococcal infection. A multivariate logistic regression model with these four factors was also built. When the average temperature is above 27.0 °C, the average atmospheric pressure is lower than 1005.1 hPa, or the UV index is above 7.2, the percentage of cumulated positive farms from all submitted tilapia cases was more than 50%. In addition, within 3 days of rain, rainfall is relevant to the occurrence of Streptococcus in tilapia. Using TDS to alert the occurrence of streptococcal infection in tilapia can be a very useful tool for veterinary aquatic animal inspection stations, and reducing economic losses and labour costs in aquatic agriculture.

Highlights

Tilapia (Oreochromis spp.) is one of the important farmed fish species in Taiwan, accounting for approximately 70,000 metric tons from the annual report for fisheries statistics, Fisheries Agency, Appl
A total of 3848 tilapias, Oreochromis spp., clinical cases have been collected in a decade
In Iran, the outbreaks of streptococcosis/lactococcosis in freshwater rainbow trout farms is strongly related with the fluctuation of water temperature and the peak of disease is observed during summer time when temperature is about 16–18 ◦ C. [29,30] Our findings showed that streptococcosis often prevails a few days after raining

Summary

Introduction

Tilapia (Oreochromis spp.) is one of the important farmed fish species in Taiwan, accounting for approximately 70,000 metric tons from the annual report for fisheries statistics, Fisheries Agency, Appl. Council of Agriculture, Taiwan [1]. The demand for tilapia from domestic markets as well as from international markets has increased two-fold since the last decade. Tilapia can tolerate adverse water quality and other stressors better than most other commercial aquaculture species. Tilapia is one of the fastest growing fish, increasing its compatibility for intensive farming. The intensive farming of tilapia with high stocking density in Taiwan has increased immensely, allowing the adaptability effects of climate change and food shortages. High stocking rates make intensive and semi-intensive farms more susceptible to infectious diseases [2]

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