Pathogenic Free-Living Amoebae and Recreational Waters
93
The possible presence of pathogenic Naegleria in human carriers or animal reservoirs
should be investigated. The method employed should allow the pathogenic individuals to
be detected. A fluorescent antibody straining method, if developed, would be ideal for
such a survey.
SUMMARY
1. The swimming-associated cases of amoebic meningoencephalitis were caused by a
species of Naegleria which is distinct from the wild strains of TV. gruben. This is based
on the facts that the pathogenic strains exhibited profound CPE on PMK cells and
produced a fatal meningoencephalitis in mice by intranasal and intracerebral
inoculations, while the wild strains of N gruberi exerted no CPE on PMK cells and
produced no disease in mice by both inoculations.
2. Both Acanthamoeba and Naegleria were frequently found in sewage effluents and
fresh surface waters, and in small numbers in outdoor swimming pools. The
Acanthamoeba was predominant in sewage effluents and polluted waters, while the
Naegleria was predominant in small warm lakes.
3. There was no evidence that wild strains of N gruberi could acquire CPE or become
pathogenic after a long period of cultivation in cell cultures.
4. Under simulated natural aquatic environment the pathogenic Naegleria, in coexistence
with a wild strain of N. gruberi reduced its population steadily and reached almost
extinction in 6 weeks of standing at room temperature, while the wild strains
exhibited a growth curve similar to that observed in plate cultures.
5. Of 12 cultures of amoebae isolated from nasal swabs of children made
before and after swimming in lakes, 2 preswimming, 8 postswimming
cultures were identified as Naegleria. Their growth characteristics in cell
cultures and their pathogenicity in mice remain to be ascertained.
6. Of samples taken from 6 Florida lakes, Naegleria was isolated alone in 3
and Naegleria and Schizopyrenus were isolated in 1. The growth characteristics in cell cultures and pathogenicity of these Naegleria strains remain
to be studied.
From these findings it is concluded that much research is needed in the
laboratory as well as in the field to ascertain the origin of the pathogenic
Naegleria in fresh surface waters and in the Czechoslovakian indoor swimming
pool. This requires investigations looking into the presence of pathogenic
Naegleria in waters and pools where cases of amoebic meningoencephalitis have
occurred, into the existence of human carriers and into the possibility of
aquatic and terrestrial animals, and birds serving as hosts of pathogenic
Naegleria. With the methods described in the preceding and this report, it is
hoped that such investigations will be carried out in the "endemic" areas.
93
The possible presence of pathogenic Naegleria in human carriers or animal reservoirs
should be investigated. The method employed should allow the pathogenic individuals to
be detected. A fluorescent antibody straining method, if developed, would be ideal for
such a survey.
SUMMARY
1. The swimming-associated cases of amoebic meningoencephalitis were caused by a
species of Naegleria which is distinct from the wild strains of TV. gruben. This is based
on the facts that the pathogenic strains exhibited profound CPE on PMK cells and
produced a fatal meningoencephalitis in mice by intranasal and intracerebral
inoculations, while the wild strains of N gruberi exerted no CPE on PMK cells and
produced no disease in mice by both inoculations.
2. Both Acanthamoeba and Naegleria were frequently found in sewage effluents and
fresh surface waters, and in small numbers in outdoor swimming pools. The
Acanthamoeba was predominant in sewage effluents and polluted waters, while the
Naegleria was predominant in small warm lakes.
3. There was no evidence that wild strains of N gruberi could acquire CPE or become
pathogenic after a long period of cultivation in cell cultures.
4. Under simulated natural aquatic environment the pathogenic Naegleria, in coexistence
with a wild strain of N. gruberi reduced its population steadily and reached almost
extinction in 6 weeks of standing at room temperature, while the wild strains
exhibited a growth curve similar to that observed in plate cultures.
5. Of 12 cultures of amoebae isolated from nasal swabs of children made
before and after swimming in lakes, 2 preswimming, 8 postswimming
cultures were identified as Naegleria. Their growth characteristics in cell
cultures and their pathogenicity in mice remain to be ascertained.
6. Of samples taken from 6 Florida lakes, Naegleria was isolated alone in 3
and Naegleria and Schizopyrenus were isolated in 1. The growth characteristics in cell cultures and pathogenicity of these Naegleria strains remain
to be studied.
From these findings it is concluded that much research is needed in the
laboratory as well as in the field to ascertain the origin of the pathogenic
Naegleria in fresh surface waters and in the Czechoslovakian indoor swimming
pool. This requires investigations looking into the presence of pathogenic
Naegleria in waters and pools where cases of amoebic meningoencephalitis have
occurred, into the existence of human carriers and into the possibility of
aquatic and terrestrial animals, and birds serving as hosts of pathogenic
Naegleria. With the methods described in the preceding and this report, it is
hoped that such investigations will be carried out in the "endemic" areas.