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Yersiniosis Of Pet Birds

Yersiniosis is also zoonotic Of Pet Birds

Yersinia spp. was first isolated by Alexandre Yersin in 1894 in HongKong. He was sent by Louis Pasteur to investigate about plague outbreak there. In Japan, S. Kitasato also independently isolated the bacteria a few days later. Previously, it was known as Pasteurella pestis in honour of Pasteur. Later, in memory of Yersin, the bacterium was renamed as Yersinia pestis. In 1976, Yersinia pseudotuberculosis was isolated from a sick palm dove (Streptopelia senegalensis) in Israel. Yersinia enterocolitica was first detected in budgerigars in 1980.
Yersinia is gram negative, short rods or coccobacilli shaped bacteria. They show bipolar staining characteristics (‘safety pin appearance’) when stained with Leishman’s or Wright or Giemsa stain. The genus Yersinia is classified under the family Enterobacteriaceae that belongs to the order Enterobacteriales. Yersinia consists of 11 numbers of species. Among them, Y. pseudotuberculosis and Y. enterocolitica are commonly associated with psittacine and passerine bird infection. Mynahs are most susceptible to Yersinia spp. infection. Yersiniosis is also reported from canaries (Serinus canaria), zebra finch (Poephila guttata), kaka (Nestor meriondalis), rainbow lorikeet (Trichoglossus mollucanus), budgerigar (Melopsittacus undulatus), New Zealand wood pigeons (Hemiphaga novaeseelandiae), blue-fronted Amazon (Amazona aestiva), yellow-headed Amazon (Amazona oratrix), Eurasian collared dove (Streptopelia decaocto) and cockatoo (Cacatua alba). Rodents and wild birds are major reservoir of infection and the feed and water are often contaminated with rodent urine or faeces. Ingestion of contaminated feed and water is the key route of transmission.
 High mortality and non-specific clinical signs such as ruffling of feathers, depression, diarrhoea, and biliverdin in the urine are observed in the birds. The infection is acute and mostly enteric in passerine birds. Chronic infection takes place in psittacines and pigeons, and it produces hepatitis, splenitis, pneumonia, nephritis and enteritis. The liver becomes dark, swollen and congested. Yellow coloured foci (bacterial granulomata) are found in the liver, spleen, lungs, kidneys, intestines and heart (Fig. 2.9). Microscopically, these foci are composed of necrosed hepatocytes and splenic pulp with fibrin and Yersinia colonies. Accumulation of iron in the liver (hepatic haemosiderosis) may act as a predisposing factor for systemic Yersinia spp. infection.
 A smear can be prepared from the collected tissues of liver, spleen, kidney, intestine and stained by Leishman’s, Wright, and Giemsa stain. Yersinia shows typical ‘bipolar characteristics’ (safety-pin appearance). Yersinia can be isolated in blood agar, nutrient agar, MacConkey’s agar, brilliant green agar (Y. enterocolitica).
 The selective medium is CIN agar which contains antibiotics such as cefsulodin (15 mg/l), irgasin (4 mg/l) and novobiocin (2.5 mg/l). ‘Cold enrichment’ method can be followed for primary isolation of Y. pseudotuberculosis and Y. enterocolitica from clinical samples. The samples are kept in sterile phosphate buffered saline (PBS) or nutrient broth at 4 °C for 3 weeks. Subculture in MacConkey’s or CIN agar is done at weekly interval. Amoxicillin in drinking water or soft food is the choice of treatment. In unresponsive cases, treatment should be carried out on the basis of antibiotic sensitivity
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