Experimentally pathogenesis of Aeromonas hydrophila in freshwater Crayfish (Astacus leptodactylus) in iran



 In this research the affect of A. hydrophila on pathogenesis of Crayfish
A. leptodactylus was carried out.
This study was designed in three groups as treatments and one group as
control in triplicate with 20 Crayfish in each glass aquarium. The treatments have exposed to A. hydrophila.
The concentrations of the bacteria in treatments were


 , and
  CFUmL-1 respectively.
The untreated control group was disinfected by oxytetracyclin at concentration of
100 ppm for 24 hours. The haemolymph samples were withdrawn for measuring of
THC and TPC within interval hours (2, 6, 12, 24, 48, 96, 144, 240 and 336). The
Crayfish samples were then fixed in Davidson fixative. The results showed that
the differences of THC value between treatment 4 (95.33±23.16) and control
(1.13±.45) were significant (P < 0.05) as well as control and
treatments 3 (35.33±16.16) and 4 (95.33±23.16) during 2 initial hours. In case
of THC the significant difference (P < 0.05) was observed between
control group (72.33±15.04) and treatment 3 (13.13±5.85) after 48 hours. During
240 hours, also the difference of THC value between control group (80.33±24.94)
with treatment 2 (14.67±3.51) was significant (P < 0.05). The finding
of TPP value showed that there was no significant difference between control
group and treatments in during mentioned times (P < 0.05). The result
of histopathology in heaptopancreas and gill sections showed that hemocyte
aggregation and necrosis within pyknosis of nucleus. In lower concentrations of
bacteria no pathological changes of heart were observed. In digestive tract no
changes were appeared in treatments, but in concentration of 3×108 CFU ml-1 a low aggregation of hemocytes was