DEVELOPMENT OF AN INFECTION MODEL FOR THE WHITE FECES DISEASE ON WHITELEG SHRIMP Penaeus vananmei

Loc Tran1,2*, Grace Chu-Fang Lo2, Vy Van Nguyen1, Phuc Hoang1, Trang Nguyen1
 
(1) ShrimpVet Laboratory, Ho Chi Minh City, Vietnam
 (2) Department of Aquaculture Pathology, College of Fisheries, Nong Lam University, Vietnam
(3) College of Bioscience and Biotechnology
National Cheng Kung University
Tainan, Taiwan
(*) Corresponding Author: thuuloc@email.arizona.edu

White Feces Syndrome has been an idiopathic disease causing significant economic losses for shrimp farmers in Asia. The syndrome is characterized by transformation and sloughing of microvilli of hepatop ancreatic tubule epithelial leading to accumulation of aggregated, transformed microvilli (ATM) in the tubule lumens (Sriurairatana et al., 2014), white fecal materials in the gut, and the floating feces on pond water surface. This study aimed at determining the transmission nature of the potential pathogen(s), isolation, characterization, and development of the infection model for the White Feces Sydrome. Based on the natures of this syndrome: occurs mostly on animals of 45-60 days of culture, thick algal bloom, bad feed management, pollution, etc., we could focus on the bacterial etiology.

Several attempts of doing the transmission via intramuscular injection and feeding of white feces syndrome affected shrimp muscle tissues failed to produce the ATM. When the freshly prepared minced gastrointestinal (GI) tract on affected shrimp was mixed with shrimp feed and fed to the experimental shrimp, the formation of ATM and gross signs of white fecal matter happened within 2 days of challenged. A mixed culture of bacterial from affected shrimp was mixed with shrimp feed and fed to the experimental shrimp. The same pathology of white feces syndrome also occurred within 2 days of challenge. Several single isolates were obtained from white feces syndrome collected from the field could produce the same pathology in a laboratory challenge model using feeding method. Up to 15 different Vibrio isolates obtained and the Koch's postulate was completed.

In short, this study could prove the infection nature of white feces syndrome and propose an infection model for this disease. Further molecular biological analyses of the isolates are under investigation.