The relationship between feeding on fish meal and aeromonas hydrophila infection in broiler chickens in Assiut Governorate

الملخص EN

A total of 137 samples including fish meals (37samples) and cloacal swabs from diarrheic broiler chickens (50 samples) as well as apparently normal chickens (50 samples) fed on ration supplemented with fish meal, were investigated for the presence of A, hydrophilic.

The overall prevalence level was 24.8 % (34/137).

The highest isolation rate was recorded from fish meal samples with a percentage 48.6 % (18 / 37), followed by 18 % (9 / 50) from diarrheic cloacal samples, whereas the lowest prevalence rate 14 % (7 / 50) has been recorded from cloacal swabs of clinical healthy broiler chickens.

Based on plasmid profiling, the relationship between 26 examined strains of A.

hydrophila revealed 14 strains (53.8 %) having plasmids with a molecular weight ranged from 2.7kb- 56kb.

Two common clones found between strains of fish meal and broiler chickens isolates that provides a suggestive evidence of successful colonization and infection by particular strains of certain A.

hydrophila after transmission from fish meal to broiler chickens, Pathogenicity of A.

hydrophila has been associated with the virulence factors such as hemolysin production, virulence genes (aerA and ascV).

The detection of the presence of such virulence factors is a better indicator of the potential risk for their pathogenicity.

Virulence factors were detected among examined strains but the higher frequency of possession was observed in diseased birds than that mentioned from strains recovered from fish meal and clinically healthy birds.

Pathogenic potential and its relation to virulent factors were investigated in one-day-chicks infected via subcutaneous (5 / 7) route.

Group infected with virulent A.

hydrophila strain that having all examined virulent traits showed 80% mortality, in contrast to 50 % mentioned with avirulent strain within 48 hours post inoculation.

Antibiotic susceptibility testing revealed 100 % of clinical strains were resistant to ampicillin, amoxicillin and erythromycin and high resistance level to tetracycline while the fish meal strains presented 100 % resistance to amoxicillin and erythromycin.

Resistance among the A.

hydrophila isolated from broiler chickens was higher than that observed with fish meal recovered strains.

Eleven out of 26 (42.3 %) examined isolates showing multiple drug resistance to the tested antibiotics, that is may indicate the use of these antimicrobials in commercial farms and this can favor the development of resistant bacterial strains.

The present work highlights an important incidence of A.hydrophila and its possession to virulence genes as well as animicrobial resistance that reinforced their potential pathogenicity to infected chiks and its possibility to causing illness and losses in broiler chickens.

Hence, continuous monitoring of fish meal is important to identify potential pathogenic A.

hydrophila before its addition to food ration to reduce the risk of infection.