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Escherichia Coli Of Pet Birds

Escherichia coli was first isolated by Theodor Escherich in 1885 from the faeces of human infants. It was named in honour of the German pediatrician and its major natural habitat i.e. colon. In 1978, E. coli was detected in faecal samples collected from psittacine birds. Raphael and Iverson (1980) described E. coli associated coligranuloma in Amazon parrot along with psittacosis.
E. coli is gram negative, short rods, varying form coccoid shape to long filamentous forms. They occur singly, in pair or in short chain. They are non-spore forming and mostly motile by peritrichous flagella. The genus Escherichia is classified under the family Enterobacteriaceae that belongs to the order Enterobacteriales. There are total 6 species under the genus Escherichia. Among them, Escherichia coli are the important pathogen.
 The gastro-intestinal tract of all vertebrates including birds is the most common natural habitat of E. coli. The studies revealed that healthy parrots (31%), cockatoos (Cacatua spp., 60%) and shore birds carried E. coli in their intestine. In healthy passerine birds, E. coli are not considered as a major intestinal flora. Psittacines imported or illegally traded from other countries and shore birds act as source of E. coli. Majority of these psittacine E. coli isolates possessed antimicrobial resistance due to the exposure of the birds to the prophylactic antibiotics after their capture.
 In pet birds, E. coli is transmitted by contaminated feed, drinking water, aerosols, and fomites. The stress conditions like transport, dietary change and extreme climate also help to establish the infection. In adult canaries and finches, E. coli are most common secondary pathogens associated with epizootic mortality. Non-specific clinical signs and lesions such as lethargy, rhinitis and conjunctivitis are detected. E. coli as a primary pathogen is reported from a hyacinth macaw (Anodorhynchus hyacinthinus), died due to septicaemia and enteritis with hemorrhages in different organs, and a kakapo (Strigops habroptilus) with exudative cloacitis. Recently, attaching-effacing E. coli is detected as a primary pathogen in a captive flock of budgerigars (Melopsittacus undulatus).   Common lesions in budgerigars include hepatitis, enteritis, and attaching and effacing lesions along the intestinal tract.
 In nestlings of canaries and finches, E. coli is considered as most important cause of diarrhoea, dehydration, cachexia and mortality. Appearance of young birds and their mothers became dirty, wet and yellowish (‘sweating disease’).
 Isolation of E. coli from the clinical samples is the major diagnostic technique. Blood agar, MacConkey’s agar are choice of the medium for isolation. After overnight incubation in MacConkey’s agar, characteristic pink coloured colonies are transferred into eosine methylene blue (EMB) agar for detection of 'metallic sheen'. The isolates are further confirmed by different biochemical tests. Pathogenicity of the E. coli isolates from clinical samples should be confirmed as they are present as normal bacterial flora within the body. Virulence of the isolates can be ascertained by ligated loop assay, cell culture cytotoxicity assay, typing and detection of toxin by serological or DNA based methods. E. coli infections can be treated with ampicillin sodium, amoxicillin/clavulanate, cephalexin, oxytetracycline and spectinomycin. In unresponsive cases, antibiotic should be selected after sensitivity test of the etiological E. coli isolates. In nestlings, antibiotics are administered in drinking water and egg food from one day before hatching up to 6 days after hatching. Extra drinking water should be provided to prevent dehydration.