Abstract. Natural cases of keratoconjunctivitis, apparently caused by Mycoplasma gallisepticum (MG), in layer chickens are described. The disease occurred in a commercial flock consisting of 36,000 pullets (Babcock), first appearing around 30 days of age. Clinically, affected chickens showed unilateral or bilateral swelling of the facial skin and the eyelids, increased lacrimation, congestion of conjunctival vessels, and respiratory rales. Some of the severely affected chickens closed their eyes. The morbidity reached 27.8%, and it was estimated that approximately 10% died from reduced feed intake due to impaired vision. Ten 70-day-old chickens with clinical diseases were examined for lesions. There was acute to subacute keratoconjunctivitis in all of the chickens, and some exhibited laryngitis. Adherence of mycoplasma organisms to epithelial cells of the conjunctiva, cornea, and larynx was frequently observed. These organisms had an ultrastructure characteristic of MG and showed a positive reaction with rabbit polyclonal antibodies against the S6 strain of MG by immunohistochemical analysis. MG was isolated from tissue homogenates of the eyelids and tracheas of the affected chickens. Many of the chickens had atrophic bursae, and infectious bursal disease virus antigens were detected in necrotic bursal follicles by immunostaining. Therefore, immunosuppression due to infectious bursal disease was implicated in the pathogenesis of keratoconjunctivitis in the present cases.Key words: Chickens; electron microscopy; immunohistochemistry; infectious bursal disease; keratoconjunctivitis; Mycoplasma gallisepticum.Mycoplasma gallisepticum (MG) is a common pathogen of chickens and turkeys that predominantly causes respiratory diseases, including sinusitis, tracheitis, pneumonia, and airsac~ulitis.~~ Occasionally, MG infection causes tenosynovitis, salpingitis, sternal bursitis, and myocarditis in chickens33 and encephalitis in turkeys.' 1,17 Severe airsacculitis in chickens with MG infection is often complicated by respiratory viruses, i.e., Newcastle disease virus (NDV) and infectious bronchitis virus (IBV), or other microorganisms, usually Escherichia ~o l i .~~ Ocular inoculation of the chickens with MG produced keratitis, iridocyclitis, and enlargement of the eyeba11,28.32~45 but natural mycoplasma1 eye diseases in chickens appear rare.** Similar conditions have been experimentally induced in cats with M. f e l i~~~ and in rats and mice with M. a r t h r i t i d i~,~~,~~ but the relationship between developed lesions and mycoplasmal infection has not yet been fully clarified.We recently observed naturally occurring keratoconjunctivitis in chickens suspected to be caused by MG infection. The purpose of this paper is to describe histopathologic, immunohistologic, and electron microscopic findings in the infected chickens. Materials and MethodsTen clinically diseased chickens were submitted to the Nippon Institute for Biological Science for pathologic evaluation. The chickens were euthanatized, and parts of the eyelids, ...
Antibodies were raised against a synthetic tetradecameric peptide with an amino acid sequence, DLIQEGNIGLMKAV, which corresponds to the most highly conserved region of bacterial RNA polymerase sigma factors. In a Western-blot analysis of total Escherichia coli proteins, the antiserum reacted specifically with at least three proteins with apparent molecular weights of 75 kDa, 27 kDa and 23 kDa, in addition to the known sigma factors (sigma 70 and sigma 32). The majorities of sigma 70 and sigma 32 were recovered as associated forms with the RNA polymerase on glycerol gradient centrifugation, while the other cross-reacting proteins were not. Unambiguous evidence was obtained which indicated that the intracellular level of sigma 32 increased rapidly upon heat-shock, at least in the strain containing high copy numbers of the rpoH gene.
Adhesion of Haemophilus paragallinarum to chicken embryo fibroblasts (CEF) in vitro was investigated in correlation with its virulence. Under the scanning electron microscope, the organisms were seen adhering to CEF exposed to the bacteria. By transmission electron microscopy, the organisms appeared to attach to the plasma membrane of CEF by their fuzzy material. They were enclosed in membrane-limited vesicles and appeared morphologically intact. Specific fluorescence was seen in the cytoplasm of CEF in later stages of infection. There was a good correlation between pathogenicity of the organisms for chickens and their ability to adhere to CEF. This correlation was reinforced by the fact that the ability of a pathogenic strain to adhere to the mucosal surface of the chicken trachea was demonstrated by scanning electron microscopy.
The effect of various routes of immunization on protection against challenge by virulent agents was examined in chickens. Chickens were immunized intratracheally, intranasally, per os, by crop gavage, and intramuscularly. Agents examined were killed Haemophilus paragallinarum, Mycoplasma gallisepticum, and infectious bursal disease virus. Results of immunization by intratracheal administration were equivalent to those produced by parenteral administration. All vaccines effectively induced production of serum antibodies against pathogens, and all immunized chickens were protected against infection by each pathogen.
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