title: Responses of giant freshwater prawn (Macrobrachium rosenbergii) to challenge by two strains of Aeromonas spp.
abstract: The virulence of two Aeromonas strains (A. veronii and A. caviae) isolated from the hepatopancreas of apparently healthy giant freshwater prawns (Macrobrachium rosenbergii) was compared using a challenge by injections. For the A. veronii strain, challenge with 3.7 x 10(5) cells/g of body weight led to 100% mortality; for the A. caviae strain, 3.8 x 10(6) cells/g produced 100% mortality. The 50% lethal doses (LD50) were 2.0 x 10(3) cells/g for A. veronii and 51.2 x 10(3) cells/g for A. caviae. Use of different culture media (trypticase soy broth vs prawn muscle extract) did not significantly affect the virulence of A. veronii. Injection of a sublethal dose (1 x 10(3) cells/g) of A. veronii led to a significant decrease in the total hemocyte count (THC) between 4 and 24 h after injection. Saline injections also caused a similar though less decrease in THC. In the first 24 h after injection of A. veronii (1 x 10(3) cells/g), the change in the percentages of granulocytes (both granular cells and semigranular cells) in the hemolymph was significantly different. After a significant initial increase, the percentage of hyaline cells fell by a factor of 4, from 9 to 2%. Phenoloxidase activity increased fourfold immediately after injection and returned to preinjection levels at 24 h.
authors: Department of Microbiology, Soochow University, Taipei, Taiwan, 111, Republic of China. hhsung@mail.scu.edu.tw
authors: H H
authors: HH
authors: Sung
authors: S F
authors: SF
authors: Hwang
authors: F M
authors: FM
authors: Tasi
mesh_terms: D000333:Aeromonas / Q000472:pathogenicity*; D000818:Animals; D004064:Digestive System / Q000382:microbiology; D006434:Hemocytes / Q000276:immunology; D033541:Palaemonidae / Q000276:immunology / Q000382:microbiology*