Water temperature influences viral load and detection of White Spot Syndrome Virus (WSSV) in Litopenaeus vannamei and wild crustaceans Juliana R. Moser a , Diego A. Galván Álvarez b , Fernando Mendoza Cano b , Trinidad Encinas Garcia b , Daniel E. Coronado Molina b , Guillermo Portillo Clark c , Maria Risoleta F. Marques a , Francisco J. Magallón Barajas d , Jorge Hernández López b, ⁎ a Laboratório de Biomarcadores de Contaminação Aquática e Imunoquímica, Departamento de Bioquímica, CCB, UFSC, Florianópolis, SC 88034-257, Brazil b Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Unidad Sonora Calle Hermosa 101, Col. Los Ángeles, Hermosillo, Sonora 83000, México c Comité de Sanidad Acuícola de Estado de Sonora (COSAES), Cd. Obregón, Sonora 85000, México d Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Mar Bermejo 195, Col. Playa Palo de Sta. Rita, La Paz, B.C.S. 23096, México abstract article info Article history: Received 2 August 2011 Received in revised form 27 October 2011 Accepted 27 October 2011 Available online 7 November 2011 Keywords: Litopenaeus vannamei Host crustaceans WSSV Temperature Infectivity assay The Pacific white shrimp Litopenaeus vannamei is particularly affected by White Spot Syndrome Virus (WSSV) as this virus can cause high mortality in infected populations. Presently, there are no known treatments for shrimp affected by WSSV and management tools for preventing this disease are limited to the exclusion of the virus from cultured shrimp populations. Previous studies have shown that warm-water culture condi- tions inhibit the replication rate of WSSV, as well as two other important shrimp viruses in L. vannamei. The purpose of this study was to evaluate the effect of thermal stress on the replication rate of WSSV in shrimp held in warm water (29 ± 0.5 °C), compared to the replication rate of WSSV in shrimp held in cool water (18±0.5 °C), looking for improve virus detection in epidemiological programs. Furthermore, post larvae and captured wild crustaceans were screened for the WSSV after being held in warm water for 2 days (48 h). The results indicate that water temperature had a profound effect on the repli- cation rate of WSSV in L. vannamei and a protocol for WSSV screening after thermal stress is proposed. Our results support the findings of previous studies and further point out to the potential application of environ- mental temperature as a management strategy to selecting WSSV-free spawning shrimp within the shrimp farming industry in Mexico and possibly in other producing countries. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Shrimp diseases have caused significant losses of production and jobs, reduced earning, export restrictions, failure and closing of business and decreased confidence of consumers (Bondad-Reantaso et al., 2005). White Spot Syndrome Virus (WSSV) is now one of the most devastating and virulent viral agents threatening the penaeid shrimp culture industry. This virus has been causing high mortality and huge economic losses in shrimp aquaculture worldwide. Shrimp cumulative mortality can reach 100% within 3 to 10 days under farming conditions (Chou et al., 1995; Lightner, 1996). WSSV has been detected in a wide range of wild crustaceans including penaeid and non-penaeid shrimp, as well as crabs and lobsters (Escobedo-Bonilla et al., 2008; Small and Pagenkopp, 2011). The first WSSV epidemic was reported in shrimp farms of South East Asia in 1992 (Chou et al., 1995). The virus then spread to shrimp farms in countries in Asia, North, Central and South America and Middle East (Flegel, 2006; Lightner, 1996; Rosenberry, 2002). The most recent outbreak in a WSSV-free area was in Brazil (Seiffert, 2005). Until now there are neither treatments, nor vaccines, for WSSV eradication, and prevention or control through reliable diagnostic procedures is the first defense barrier against this pathogen (Bachère, 2000; Roch, 1999). Continuous and strict monitoring of the various components of shrimp farming is required to reduce the spread of WSSV within a region and to avoid the introduction of the pathogen into a new area. Moreover, such monitoring measure can also contribute to improve the design of sanitary and management strategies to minimize the negative impact of the disease on shrimp production. However, either persistent, very low level infections or virus latency in shrimp and other crustaceans can occur, sometimes at levels that are not detectable, even by the most sensible PCR procedure (Walker and Winton, 2010). The amplification of viral loads and onset of disease can be induced by environmental or physiological stress or ambient temperatures (Lotz et al., 2005; Sánchez-Martínez et al., 2007). Optimum temperature for growth and survival of shrimp varies according to the life stage and the species. For Litopenaeus vannamei, for example, optimum temperature ranges from 27 °C to 30 °C (Wyban et al, 1995). Highest Aquaculture 326-329 (2012) 9–14 ⁎ Corresponding author. Tel.: + 52 6622131593; fax: + 52 6622121201. E-mail address: jhlopez04@cibnor.mx (J.H. López). 0044-8486/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2011.10.033 Contents lists available at SciVerse ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online