Lethal dose and clinical signs of Aeromonas hydrophila in Arapaima gigas (Arapaimidae), the giant fish from Amazon

Abstract

Aeromonas hydrophila is causing substantial economic losses in world aquaculture. This study determined the tolerance limit (LD50-96h) of A. hydrophila in Arapaima gigas, and also investigated the clinical signs after intradermal inoculation. Arapaima gigas fingerlings were inoculated intraperitoneally with 0 (control), 1.0×10(5), 1.0×10(6), 1.0×10(7), 1.0×10(9) and 1.0×10(10)CFU/mL of A. hydrophila for the determination of LD50-96h, which was 1.8×10(8)CFU/mL. In another trial with intradermal inoculation of 1.8×10(8)CFU/mL A. hydrophila, there was a 91.6% of mortality between 8 and 23h, and several clinical signs were found. As follows: depigmentation in the tegument, lesions in the tail and fins, loss of balance, reduction of respiratory movements, hemorrhagic foci, necrotic hemorrhages in the kidney, liver and swim bladder, splenomegaly, ascites in the abdominal cavity and hyperemia, enlargement of the gall bladder, among other clinical signs observed. The results showed that A. gigas has a relative tolerance to A. hydrophila when compared to other Neotropical fish species.

Diagnostic methods for identifying different Aeromonas species and examining their pathogenicity factors, their correlation to cytotoxicity and adherence to fish mucus

“…Both opportunities will probably improve the identification possibilities by MALDI‐TOF MS within the next years. In fact, there are already reports that an identification of Aeromonads is possible even below the species level and even for specific strains (Benagli et al., ; Donohue, Smallwood, Pfaller, Rodgers, & Shoemaker, ). However, the basis for good identification results is the testing of well‐characterized strains of different origins to produce a high‐quality database (Benagli et al., ).…”

Growth, physiological and immune responses of Arapaima gigas (Arapaimidae) to Aeromonas hydrophila challenge and handling stress following feeding with immunostimulant supplemented diets

“…After 30 days of feeding trial, other four fish from each replicate (8 fish/treatment) were challenged with Aeromonas hydrophilla (ATCC:7966). The fish were inoculated intraperitoneally with 1.8 × 10 8 UFC mL −1 , the lethal concentration (LC 50-96h ) for A. gigas [1]. Mortality and clinical signs of bacteriosis were observed for 7 days, after which the surviving fish were subjected to handling stress.…”

“…The Amazon region has an important contribution to the cultivation of native and non-native fish species. Arapaima gigas Schinz, 1822 (pirarucu), a piscivorous air-breather fish, is among the main native species cultivated due to its high valued zootechnical characteristics such as fast growth, tolerance to the high density of storage and rusticity to the handling, high meat yield, besides having an excellent acceptance in the national and international market [1][2][3][4]. However, its production is still limited by the low availability, high cost of fingerlings [4] and economic losses, due to the large mortalities in the initial phase of production.…”

“…However, its production is still limited by the low availability, high cost of fingerlings [4] and economic losses, due to the large mortalities in the initial phase of production. The handling of A. gigas during routine practices in aquaculture production can cause stress to the fingerlings, reducing the resistance to diseases outbreaks, leading to mass mortalities [1,3], caused mainly by aeromoniosis [1,5].…”

“…Similar to other industries, aquaculture constantly requires new techniques to increase production and productivity, while maintaining fish health [3,6,7]. However, with the development of global aquaculture, several problems have arisen, including the deterioration of water quality, parasitic and bacterial diseases [1,3,4,7]. Diets supplemented with immunostimulants based on Saccharomyces cerevisiae, which contain beta-glucan polysaccharide, mannanoligosaccharides and chitin have been recommended for improvement in fish production [7][8][9][10].…”