A similar type of meningitis may occasionally complicate histoplasmosis, blastomycosis, and the anaerobic bacterium actinomycosis. These chronic meningitides possess no specific features except that actinomycosis, like some cases of tuberculosis and nocardiosis, may cause a persistent polymorphonuclear pleocytosis (see “Chronic Persistent and Recurrent Meningitis” in Chap. 32). The CSF yields an organism in a minority of patients, so that diagnosis depends on culture from extraneural sites, biopsy of brain abscesses if present, as well as knowledge of the epidemiology of these fungi. Patients with chronic meningitis in whom no cause can be discovered should also have their CSF tested for antibodies to Sporothrix schenckii, an uncommon fungus that is difficult to culture. Several even rarer fungi that must be considered in the diagnosis of chronic meningitis are discussed in the article by Swartz and Dodge.
Treatment The current preferred treatment is fluconazole and amphotericin B and supplemental antifungal agents are used in the others. Intrathecal amphotericin via a reservoir is administered in patients who relapse.
INFECTIONS CAUSED BY RICKETTSIAS, PROTOZOA, AND WORMS
Rickettsias are obligate intracellular parasites that appear microscopically as pleomorphic coccobacilli. The major ones are maintained in nature by a cycle involving an animal reservoir, an insect vector (lice, fleas, mites, and ticks), and humans. Epidemic typhus is an exception, involving only lice and human beings, and Q fever is probably contracted by inhalation. At the time of World War I, the rickettsial diseases, typhus in particular, were remarkably prevalent and of the utmost gravity. In Eastern Europe, between 1915 and 1922, there were an estimated 30 million cases of typhus with 3 million deaths. Now, the rickettsial diseases are of minor importance, the result of insect control by dichlorodiphenyltrichloroethane (DDT) and other chemicals and the therapeutic effectiveness of broad-spectrum antibiotics. In the United States these diseases are quite rare, but they assume significance because, in some types, up to one-third of patients have neurologic manifestations. About 2000 cases of Rocky Mountain spotted fever (the most common rickettsial disease) occur each year in the United States, with a mortality of 5 percent or less. Neurologic manifestations occur in a small portion, and neurologists may not encounter a single instance in a lifetime of practice. For this reason, the rickettsial diseases are simply tabulated here.
The following are the major rickettsial diseases: 1. Epidemic typhus, small pockets of which are present in many developing parts of the world. It is transmitted from lice to humans and from person to person.
2. Murine (endemic) typhus, which is present in the same areas as Rocky Mountain spotted fever (see in the following text). It is transmitted by fleas from rats to humans.
3. Scrub typhus or tsutsugamushi fever, which is confined to eastern and southeastern Asia. It is transmitted by mites from infected rodents or humans.
4. Rocky Mountain spotted fever, first described in Montana, is most common in Long Island, Tennessee, Virginia, North Carolina, and Maryland and in the Southwest. It is transmitted by special varieties of ticks.
5. Q fever, which has a worldwide distribution (except for the Scandinavian countries, New Zealand, and the tropics). It is transmitted in nature by ticks but also by inhalation of dust and handling of materials infected by the causative organism, Coxiella burnetii.