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

192 BACTERIOSESstimulates proliferation of F. necrophorum, and the latter protects C. pyogenes fromphagocytosis by producing a leukocidin (Cottral, 1978).CATTLE: Calf diphtheria (necrobacillary stomatitis) is characterized by sialorrhea,anorexia, and necrotic areas in the oral cavity. Infection can spread to the larynx and,by inhalation, to the lungs, where it causes abscesses and pneumonia. The diseaseonly occurs in animals under 2 years of age; mature animals seem immune. The diseaseis caused by F. necrophorum and is seen in dairy operations with deficienthygiene. The same disease also affects young goats.Hepatic necrobacillosis is discovered by veterinary inspection in slaughterhousesand results in confiscation of carcasses. Lesions on the liver are characterized bywell-delineated yellow areas with a firm consistency.Foot rot in bovines is an acute or chronic necrotic infection of the interdigital skinand the coronary region. The chronic form frequently produces arthritis in the distaljoint of the limb. F. necrophorum and Bacteroides meleninogenicus have been isolatedfrom biopsy samples of foot rot lesions. A mixture of both bacteria administeredby interdigital scarification or intradermal inoculation reproduced the typicallesions (Berg and Loan, 1975). Nevertheless, the etiology still has not been completelyclarified, and it is possible that concurrent infection by F. necrophorum andother bacteria (B. nodosus, staphylococci) causes the disease (Timoney et al., 1988).Mastitis caused by Bacteroides fragilis has also been described in cattle.SWINE: Pathologies such as ulcerous stomatitis, necrotic enteritis, necrotic rhinitis,and abscesses have been described in this species.OTHER ANIMAL SPECIES: Similarly to what happens in man, osteomyelitis in animalsmay be caused by anaerobes. Of a total of 39 anaerobic bacteria isolated from19 marrow specimens, the most frequent genus was Bacteroides (18 isolates). B.asaccharolyticus was isolated from 26% of the specimens (Walker et al., 1983).Source of Infection and Mode of Transmission: F. necrophorum andBacteroides spp. are part of the normal flora of several mucous membranes inhumans and animals. The infection is endogenous, particularly in man. The relativeinfrequency of the disease in man indicates that predisposing factors are necessaryfor it to occur. These are usually traumas and debilitating illnesses. In sum, they areopportunistic agents. A lowered oxidation-reduction potential (E h) resulting frominsufficient blood supply, together with tissue necrosis and the presence of other facultativebacteria, creates a favorable environment for this and other anaerobic bacteria.Vascular disease, edema, surgery, and cold are some of the common factorsfavoring implantation and multiplication of anaerobes (Finegold, 1982). Mostpatients with anaerobic pulmonary infection (abscesses, necrotic pneumonia, pneumonitis,empyema) suffer from altered consciousness or dysphagia due to aspirationof the oropharyngeal content, which is rich in anaerobic flora. The underlying conditionsare usually alcoholism, a cerebrovascular accident, general anesthesia, convulsions,and narcotics abuse, among others (Bartlett and Finegold, 1974).An important predisposing factor in sheep and bovine foot rot is softening of theinterdigital epidermis caused by moist ground, enabling F. necrophorum to implantitself and multiply. In addition, this bacteria abounds in humid environments (soiland grass contaminated by animal feces) and has been proved able to survive outsidea host’s body for several months. In contrast, B. nodosus is a parasite that can