Abstract
Histophilus somni, a member of the family Pasteurellaceae, causes a variety of diseases, including thromboembolic meningoencephalitis (TEME) and respiratory diseases, which result in considerable economic losses to the cattle and sheep industries. In this study, 132 chronologically diverse isolates from cattle in Japan and 68 isolates from other countries comprising 49 from cattle and 19 from sheep were characterized using major outer membrane protein (MOMP) gene sequence and pulsed-field gel electrophoresis (PFGE) analyses. The H. somni isolates formed nine MOMP genetic clades (clade Ia, Ib, and II–VIII) and 10 PFGE clusters (HS1–HS10). Except for two (1.0%), all isolates fell into one of the nine MOMP genetic clades, while 62 (31.0%) isolates belonged to no PFGE cluster. MOMP genetic clade Ia and PFGE cluster HS1 were the major groups, and all HS1 isolates possessed the clade Ia MOMP gene. Isolates from TEME cases were significantly associated with these major groups (chi-square test, p < 0.0001), as 88.2% of the TEME isolates belonged to MOMP genetic clade Ia and PFGE cluster HS1, which formed the most predominant clonal group. After an inactivated vaccine using an HS1 strain with the clade Ia MOMP gene was introduced in Japan in late 1989, the number of TEME cases and isolates assigned into the clonal group decreased simultaneously. However, the proportions of clade Ia and cluster HS1 isolates from TEME cases remained high after 1990. These results suggest a close association of TEME with PFGE cluster HS1 and MOMP genetic clade Ia, and imply the presence of factors or characteristics commonly possessed by those strains that contribute to the development of TEME.
Highlights
Histophilus somni causes a variety of diseases, collectively called histophilosis, which include thromboembolic meningoencephalitis (TEME), respiratory diseases, such as pneumonia, myocarditis, and reproductive disorders, resulting in significant economic losses to the cattle and sheep industries [1,2,3]
H. somni strains show genetic diversity, our results indicates that a predominant group of strains with a specific genetic background (MOMP genetic clade Ia and Pulsed-field gel electrophoresis (PFGE) cluster HS1) can cause TEME in cattle
Since the results imply the presence of virulence factors or characteristics commonly possessed by specific strains that contribute to the development of TEME, further investigations of strains of major outer membrane protein (MOMP) genetic clade Ia and PFGE cluster HS1 will provide novel insights into the pathogenic mechanisms of TEME associated with histophilosis
Summary
Histophilus somni causes a variety of diseases, collectively called histophilosis, which include thromboembolic meningoencephalitis (TEME), respiratory diseases, such as pneumonia, myocarditis, and reproductive disorders, resulting in significant economic losses to the cattle and sheep industries [1,2,3]. This organism is globally distributed and has been isolated from diseased tissues, and the nasopharyngeal tracts and reproductive organs of healthy animals [1, 3]. These studies have failed to clarify any association between PFGE patterns and the virulence of H. somni isolates, probably due to the limitations of isolate numbers, isolation areas, and/or isolation sources
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