Small free‐living amebas belonging to the genera Acanthamoeba and Naegleria occur world‐wide. They have been isolated from a variety of habitats including fresh water, thermal discharges of power plants, soil, sewage and also from the nose and throats of patients with respiratory illness as well as healthy persons. Although the true incidence of human infections with these amebas is not known, it is believed that as many as 200 cases of central nervous system infections due to these amebas have occurred world‐wide. A majority (144) of these cases have been due to Naegleria fowleri which causes an acute, fulminating disease, primary amebic meningoencephalitis. The remaining 56 cases have been reported as due either to Acanthamoeba or some other free‐living ameba which causes a subacute and/or chronic infection called granulomatous amebic encephalitis (GAE). Acanthamoeba, in addition to causing GAE, also causes nonfatal, but nevertheless painful, vision‐threatening infections of the human cornea, Acanthamoeba keratitis. Infections due to Acanthamoeba have also been reported in a variety of animals. These observations, together with the fact that Acanthamoeba spp., Naegleria fowleri, and Hartmannella sp. can harbor pathogenic microorganisms such as Legionella and or mycobacteria indicate the public health importance of these amebas.
To investigate the epidemiology of human immunodeficiency virus (HIV) encephalopathy, we analyzed cases of acquired immunodeficiency syndrome (AIDS) reported to the Centers for Disease Control (CDC) from September 1, 1987, through August 31, 1991. Of 144,184 persons with AIDS (PWAs), 10,553 (7.3%) were reported to have HIV encephalopathy. The proportion of PWAs with HIV encephalopathy was highest at the extremes of age: in PWAs less than 15 years old the proportion was 13%, and in PWAs greater than or equal to 15 years old the proportion progressively increased with age, from 6% in PWAs 15 to 34 years old to 19% in PWAs greater than or equal to 75 years old (p = 0.00001, chi 2 test for linear trend in proportions). The reported annual incidence of HIV encephalopathy per 100,000 population aged 20 to 59 years was 1.4 in 1988, 1.5 in 1989, and 1.9 in 1990. This analysis best provides estimates for HIV encephalopathy as the initial manifestation of AIDS because the CDC AIDS reporting system often does not ascertain diagnoses after the initial AIDS report. These data suggest that age (very young or old) is associated with the development of HIV encephalopathy and that HIV encephalopathy is a common cause of dementia in adults less than 60 years old in the United States.
We studied 19 Eskimo patients with alveolar hydatid disease from the north-western coast of Alaska for risk factors for infection with Echinococcus multilocularis. Each case-patient was matched by age and sex with 2 unrelated controls who had no clinical or serologic evidence of infection with E. multilocularis and who resided in three villages endemic for alveolar hydatid disease. Behaviors thought to increase exposure to E. multilocularis and the chronologic occurrence of these behaviors in the participant's life were assessed by a standardized questionnaire. Case-patients were more likely than controls to have owned dogs for their entire lives (odds ratio 6.00, P less than 0.05), tethered their dogs near the house (odds ratio 8.50, P less than 0.05), and lived in houses built directly on the tundra rather than on gravel or a permanent foundation (odds ratio 11.00, P less than 0.01). Case-patients were not more likely to have owned sled dogs, trapped or skinned foxes, or engaged in other outdoor activities away from home. These findings suggest that controlling the parasite in the domestic dog population, as well as controlling the dog population itself, are important aspects of preventing alveolar hydatid disease in the northwestern Native Alaskan population.
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