Twelve-week-old indigenous chickens, either immune-suppressed using dexamethasone (IS) or non-immune-suppressed (NIS), were challenged with a low virulent strain, Pasteurella multocida strain NCTC 10322T, and developed clinical signs and pathological lesions typical
of chronic fowl cholera. NIS birds demonstrated much more severe signs of fowl cholera than IS birds. With few exceptions, signs recorded in IS and NIS birds were of the same types, but significantly milder in the IS birds, indicating that immune suppression does not change the course of infection
but rather the severity of signs in fowl cholera. P. multocida signals by fluorescent in situ hybridization (FISH) were observed between 1 h and 14 days in the lungs, trachea, air sacs, liver, spleen, bursa of Fabricius and caecal tonsils, while signals from other organs mostly
were observed after 24 h. More organs had FISH signals in NIS birds than in IS birds and at higher frequency per organ. Many organs were positive by FISH even 14 days post infection, and it is suggested that these organs may be likely places for long-term carriage of P. multocida following
infection. The present study has demonstrated the spread of P. multocida in different tissues in chickens and distribution of lesions associated with chronic fowl cholera, and pointed to a decrease of pathology in IS birds. Since dexamethasone mostly affects heterophils, the study suggests
that these cells play a role in the development of lesions associated with chronic fowl cholera in chickens.
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Document Type: Research Article
Department of Veterinary Pathology, Microbiology and Parasitology, Faculty of Veterinary Medicine,University of Nairobi, P.O. Box 29053Nairobi, Kenya
Faculty of Science,Open University of Tanzania, P.O. Box 23409Dar Es Salaam, Tanzania
Department of Veterinary Disease Biology, Faculty of Life Sciences,University of Copenhagen Stigbøjlen 4, 1870Frederiksberg C, Denmark
Publication date: December 1, 2011
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