Virulence of Serovar C-1 Strains ofAvibacterium paragallinarum

Abstract

The bacterium Avibacterium paragallinarum is the etiologic agent of infectious coryza of chickens. There are nine serovars of A. paragallinarum , and serovar C-1 has emerged in outbreaks of infectious coryza in layer hens in the Americas, with all isolates having been obtained from infectious coryza-vaccinated chickens. In the current study, the clinical and histopathologic outcomes of experimental infections in chickens with A. paragallinarum of serovar C-1 were investigated. The Japanese serovar reference strain, H-18, and a Mexican isolate, ESV-135, were included in the study. No differences in clinical sign scores or morbidity were observed between the two strains. The two bacterial strains caused microscopic lesions of lymphoplasmacytic inflammation in the mucosa of the nasal cavity, infraorbital sinus, and trachea. Similar severe lesions were observed in birds inoculated with both H-18 and ESV-135 strains. The lesions were present 48 hr after inoculation and persisted until day 10 after inoculation. Slight to severe, extensive hemorrhages were observed in the lumen, mucous membranes, and lamina propria of the nasal cavity and infraorbital sinus in most of the chickens inoculated with either the reference strain H-18 or the ESV-135 isolate. Hemorrhages in the upper respiratory tract of chickens experimentally infected with A. paragallinarum are reported here for the first time. The results have confirmed the high virulence of the reference strain H-18 as previously reported and have shown that the Mexican isolate was as virulent as the reference strain. The virulence of A. paragallinarum isolates may play a role in explaining why severe infectious coryza outbreaks are being seen in both vaccinated and nonvaccinated chicken flocks.

First report on the molecular detection, phylogeny, virological and pathological investigations of Avibacterium paragallinarum in chickens in Turkey

“…The clinical signs observed in affected chickens, such as ruffled feathers, respiratory distress, a swollen head, submandibular edema, sticky eyes, and purulent nasal discharge, were similar to those reported previously (10,21). In addition, macroscopic findings (fibrinous mass in infraorbital sinuses, facial tissue edema, gelatinous and cheese-like material under the facial skin) and microscopic findings (facial cellulitis and dermatitis with fibrin filaments and infiltration of inflammatory cells) obtained in the current study were similar to those of previous observational and experimental studies (1,2,10,12,14,17,19,21).…”

“…Likewise, major histopathological lesions include inflammation of the respiratory mucosa with severe damage to the epithelium and infiltration of heterophils (10). Furthermore, severe hemorrhages in tissues of the nasal cavity as well as in sinus infraorbitalis have been reported (21). A. paragallinarum is of paramount importance in the poultry industry because of its worldwide distribution and may contribute to the formation of "respiratory disease complex" under field conditions, thus leading to more severe clinical signs.…”

A transient increase in MHC-IIlow monocytes after experimental infection with Avibacterium paragallinarum (serovar B-1) in SPF chickens

“…paragallinarum occurs, as bacteria are eliminated days after initial infection [ 6 , 8 ]. Confirming the role of immune cells in the in situ inflammatory response, infiltration of lymphocytes and heterophils (the avian counterpart of mammalian neutrophils) into the mucous membranes and lamina propria of the infraorbital sinus was demonstrated in infected animals [ 47 ]. Heterophils have the ability to clear bacteria by phagocytosing bacteria, degranulating, and generating an oxidative burst [ 48 ], and as demonstrated by Bojesen and collaborators, these cells also mediate local inflammation and tissue necrosis [ 49 ].…”

The Genome Sequence of Avibacterium paragallinarum Strain CL Has a Large Repertoire of Insertion Sequence Elements

“…Classical serotyping of A. paragallinarum includes A, B, and C serovars (1). A recent emergence of atypical strains of A. paragallinarum in outbreaks of infectious coryza has been reported (5). Among the promising strategies for the control of this disease, determination of DNA sequences of the A. paragallinarum genome is the most outstanding strategy to study its pathogenesis at a molecular level.…”