zoonoses and communicable diseases common to ... - PAHO/WHO

NECROBACILLOSISICD-10 A48.8 other specified bacterial diseasesSynonyms: Schmorl’s disease, calf diphtheria, foot rot.Etiology: Fusobacterium necrophorum, a nonsporulating, obligate anaerobe thatis a pleomorphic, gram-negative bacillus of the family Bacteroidaceae. In broth cultures,F. necrophorum varies from coccoid shapes to filaments with granular inclusions.Rod shapes are more common in agar cultures. This bacteria is a componentof the normal flora of the mouth, gastrointestinal tract, and urogenital tract of manand animals. Strains have varied virulence categories: pathogenic for mice; slightlypathogenic or not at all, but hemolytic, like the first category; and a third category(formerly called Sphaerophorus pseudonecrophorus) that is neither hemolytic norpathogenic. There may be mutation from one category (or phase) to another. Thevalidity of the identification of this bacteria in works prior to 1970 is questioned(Holdeman et al., 1984).Different species of Bacteroides play an important pathogenic role in necrobacillosis.They may appear alone or in conjunction with other species of the same genus,particularly in man, or with F. necrophorus in animals. Bacteroides spp. is also anonsporulating, gram-negative, obligate anaerobe. Bacteroides nodosus is of particularinterest in sheep pathology. These bacteria are nonmotile, and take the shape ofstraight or slightly curved rods sized 1 to 1.7 by 3 to 6 microns. They appear singlyor in pairs and often have thickened ends (Holdeman et al., 1984). They have numerouspili (fimbriae), an important virulence factor. The pili likely play an importantrole in colonization of the epidermal matrix of hooves. These appendices also makeit possible to sub-classify the agent serologically into 9 serogroups containing 16 to20 serovars or serotypes, according to their determination in different countries(Gradin et al., 1991).The polymicrobial nature of most anaerobic infections in man makes it difficultto distinguish the true pathogen or pathogens from those that merely accompany theinfection (Kirby et al., 1980). Singly or acting jointly with other nonsporulating,anaerobic bacteria, F. necrophorum causes different diseases and pathological conditionsin man and animals. Different species of the genus Bacteroides, whichbelong to the same family as F. necrophorum, cause disease either by themselves (inman) or in combination and at times in synergistic action with F. necrophorum (inman and animals).Geographic Distribution: Worldwide.