A potential prokaryotic and microsporidian pathobiome that may cause shrimp white feces syndrome (WFS)

Abstract

White feces syndrome (WFS) in shrimp cultivation ponds is characterized by the occurrence of shrimp with abnormal, white intestines (midguts) combined with large floating mats of white, shrimp fecal strings. The etiology for WFS is complex, similar to diarrhea in humans. EHP-WFS is a type of WFS characterized by massive quantities of spores from the microsporidian parasite Enterocytozoon hepatopenaei (EHP) together with mixed, unidentified bacteria in the shrimp hepatopancreas, midgut and fecal strings. However, WFS does not always develop in shrimp with severe EHP infections in controlled laboratory challenges. Further, in EHP-WFS outbreak ponds, some shrimp show white midguts (WG) while others in the same pond show grossly normal midguts (NG). We hypothesized that comparison of the microbial flora between WG and NG from the same EHP-WFS pond would reveal probable combinations of microbes significantly associated with EHP-WFS. To test this hypothesis, we selected a pond exhibiting a severe EHP-WFS outbreak in cultivated Penaeus vannamei and used a combination of microscopic and microbial profiling analyses to compare WG and NG samples. By histology, EHP plasmodia and spores were confirmed in the hepatopancreas (HP) and midgut of WG and NG shrimp, but pathological severity and spore quantity was higher in the WG shrimp. In addition, intestinal microbiomes in WG shrimp were less diverse and had higher abundance of bacteria from the genera Vibrio and Propionigenium. Propionigenium quantity in the HP of WG shrimp was significantly higher (P = 1.08e-5) than in NG shrimp (4,506 vs. 3 copies /100 ng DNA, respectively). These findings supported our hypothesis by revealing two candidate bacterial genera that should be tested in combination with EHP as a potential eukaryote-prokaryote pathobiome that causes EHP-WFS in P. vannamei.