Isolation, characterisation and pathogenicity testing of escherichia coli occurring in poultry in some parts of Kenya
Karanja, M W
MetadataShow full item record
Poultry is a good source of protein (eggs and meat) because they are fast growmg. Their productivity however is affected by, among other things, bacterial infections among which is Escherichia coli. Escherichia coli is one of the bacteria that cause much loss due to infection and death of chicken, especially from day old to two weeks old. Unpublished reports from Veterinary Research Laboratories, Kabete, have shown that E coli infections cause the highest number of deaths among day old to two week old chicken. E coli, being a normal inhabitant of the gastrointestinal tract, is constantly being shed into the environment through the faeces. It could be possible that even pathogenic types are shed, in which case, they would contaminate the environment thus propagating the infections. The present study was meant to isolate, characterise and test for pathogenicity of E coli that occur as normal flora of the intestinal tract of chicken. This was to reveal whether the pathogenic types are part of these normal flora or not. The study also aimed at determining whether management of the poultry farms has an effect on the occurrence of Ecoli. To do this, one slaughterhouse, five well managed and five poorly managed farms were visited. A number of cloacal swabs, upper respiratory tract swabs and blood samples were collected. The cloacal and upper respiratory tract swabs were investigated bacteriologically by culturing on MacConkey and blood agar. Any isolate of Ecoli recovered from a specimen was stored; other bacteria species were noted. The results showed E coli to be the most abundant of all species recovered during the study. Other investigators have also found E coli to be the most abundant from faeces. The specimens from the slaughter house were shown to have the highest percentage of Ecoli where it constituted 58%. The well managed farms had a higher percentage of Ecoli (50.6%) than poorly managed ones (47.3%). A random sample of the isolates of Ecoli recovered was picked and tested for pathogenicity, by experimentally infecting day old chicks via aerosol route; 0.5 ml suspension of the specific bacterial isolate was used. The results revealed that 60% of the isolates were pathogenic, while 40% did not show any signs associated with E coli infections. Plasmid analysis was done for one hundred and seventeen isolates. This was with the aim of relating presence of plasmid with pathogenicity. Eighty percent (80 %) of the isolates had plasmids. It was found that pathogenicity of E coli is not directly related to the presence of plasmids. Serology done on the blood samples collected showed presence of immunological activity against E.coli antibodies in all the samples. This immunological response is probably due to the constant exposure of the birds to E coli through dust. Statistical analysis showed that management does not affect the occurrence of Ecoli. This, however, does not discredit good management practices because the study, by it's design, was limited to only ten farms; half of these well managed and half poorly managed. The well managed farms cannot be said to have completely the same practices, so it is possible that other factors may have affected these results, such as source of feed and water. In conclusion, this study was able to confirm that pathogenic E. coli do occur as part of normal intestinal flora of chicken and need to be controlled. Chicken are highly exposed to it as revealed by serological tests. Apart from management, other factors such as source of birds, feed and water, are important in it's control. It is recommended that further work be done to see how these factors work together with management for control of E. coli infections.