Epizootiology

Man is the natural reservoir of b-hemolytic group A streptococci. Transmission is mainly via close contact or contaminated food and usually involves an asymptomatic carrier colonized in the nasopharynx, skin, vagina, or rectum (Facklam and Carey, 1985).

Hook et al. (1960) found that up to 52% of mice from a commercial breeding facility harbored the organism in their throats. One-third of infected mice developed cervical lymphadenitis, and approximately 50% of those observed for 3 months died of the streptococcal infection. The source of infection for the mice studied by Nelson (1954) and Hook et al. (1960) was not determined. The fact that the mice of all epizootics reported by Nelson (1954) and Hook et al. (1960) were in the vicinity of New York City suggests that there could have been a common source of infection. Hook et al. (1960) were unsuccessful in culturing group A streptococci from 40 throat cultures obtained from 15 people who worked with their mice. At least four stocks of mice, S (Swiss), Princeton (the noninbred forerunner of strain PL), C57 (strain designation incompletely given), and A (an unspecified stock designated A by Jacob Furth), have been involved in four spontaneous epizootics (Hook et al., 1960).

Clinical

Some mice carried the organism in their throats for more than 90 days without developing clinical signs of infection. Affected mice showed ruffled hair coats and inactivity for a few days before death. In the more advanced cases the cervical lymph nodes were enlarged and often had purulent exudate draining through fistulous tracts to the skin (Nelson, 1954; Hook et al., 1960).

Pathology

Only gross descriptions of the pathology in this disease have been published. The lesions reported included suppurative cervical lymphadenitis (with or without drainage to the skin), otitis media, rhinitis, and pneumonia. Myriads of organisms were demonstrated in exudates from cervical nodes. Septicemia caused by S. pyogenes was considered an important cause of death because the organism was often cultured from heart blood of animals that died (Nelson, 1954; Hook et al., 1960).

Wildfeuer et al. (1978) carried out experimental studies in which mice were infected intranasally with the organism. Suppurative cervical lymphadenitis was produced regularly, and the infection in mice was proposed as an experimental model of human streptococcal pharyngitis.



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