D I S C U S S I O N
L. Coin, France.
Dr. Coin's summary of Dr. Chang's paper, given in the author's absence.
Dr. Coin dealt specifically with the question: How could an indoor swimming pool be implicated in
cases of infection? He drew attention to the work of Professor Jadin of the Institute Zootropical,
Anvers, which emphasized that most of the cases have occurred in heated pools, that certain waters
distributed are not free from amoebae, that sand filters and ion exchange resins used for water
softening may actually harbour amoebae and that waters satisfying bacteriological criteria may also
contain amoebae. This work had been reported to the Conseil Superior d'Hygiene Publique de France
and the study was continuing. It was supported by the Institut Pasteur, Paris, in collaboration with the
Laboratoire d'Hygiene de la Ville de Paris, which supervised more than 150 swimming baths in the
region of Paris. The results are as yet not available but it is already clear that non-pathogenic amoebae
have been isolated from a number of samples.
Author's response to Dr. Coin's comments:
The author is very impressed by Dr. Coin's interest in the involvement of an indoor swimming pool
in the occurrence of Naegleria meningoencephalitis. This point was emphasized in my earlier paper
(Chang, 1971) and again the present communication. Dr. L. Cerva mentioned in his recent paper
(1971) that during the summer months, the large glass panels along one side of the pool hall are
thrown open and visitors can pass from the pool into the garden, where small pools and showers are
located and a number of species of small free-living amoebae were isolated from both the soils and
small pools. The interesting point is that Dr. Cerva had isolated a variety of amoebae, but no pathogenic Naegleria from the pool water, walls, floors, and filter, and in larger numbers from the garden
soils and pools. He believed that the poolbound amoebae were introduced from the garden by bathers
or swimmers.
As indicated in the earlier (1971) and this report, the pathogenic Naegleria is genetically different
from the wild nonpathogenic N gruben commonly encountered in natural waters, soils, and sewage
effluent. The presence of the latter amoebae may, in fact, have no relation to the presence of
pathogenic Naegleria.
The present findings seem to point to the possibility that the pathogenic Naegleria may lead a
parasitic life in warm-blood animals (terrestial animals living near water, waterfowl, and human beings
themselves). Of particular interest is the fact that very recently the author has found that out of a total
of nine strains of Naegleria isolated from human nasal swabs of children in the summer of 1969 in a
survey of amoebae conducted by the National Center for Disease control in the Richmond, Virginia
area, one exhibited growth and cytopathic effect (CPE) characteristics in primary monkey kidney cell
cultures typical of pathogenic Naegleria. Tests of this strain for pathogenicity in mice will be conducted as soon as possible. Even without the pathogenicity results, there is strong indication that this
strain is most likely that of a pathogenic Naegleria. The findings will be reported in detail in a paper in
preparation by the author, Dr. George Healy, and Dr. Jay Shomaker of the National Center for Disease
Control, Atlanta, Georgia.
97
L. Coin, France.
Dr. Coin's summary of Dr. Chang's paper, given in the author's absence.
Dr. Coin dealt specifically with the question: How could an indoor swimming pool be implicated in
cases of infection? He drew attention to the work of Professor Jadin of the Institute Zootropical,
Anvers, which emphasized that most of the cases have occurred in heated pools, that certain waters
distributed are not free from amoebae, that sand filters and ion exchange resins used for water
softening may actually harbour amoebae and that waters satisfying bacteriological criteria may also
contain amoebae. This work had been reported to the Conseil Superior d'Hygiene Publique de France
and the study was continuing. It was supported by the Institut Pasteur, Paris, in collaboration with the
Laboratoire d'Hygiene de la Ville de Paris, which supervised more than 150 swimming baths in the
region of Paris. The results are as yet not available but it is already clear that non-pathogenic amoebae
have been isolated from a number of samples.
Author's response to Dr. Coin's comments:
The author is very impressed by Dr. Coin's interest in the involvement of an indoor swimming pool
in the occurrence of Naegleria meningoencephalitis. This point was emphasized in my earlier paper
(Chang, 1971) and again the present communication. Dr. L. Cerva mentioned in his recent paper
(1971) that during the summer months, the large glass panels along one side of the pool hall are
thrown open and visitors can pass from the pool into the garden, where small pools and showers are
located and a number of species of small free-living amoebae were isolated from both the soils and
small pools. The interesting point is that Dr. Cerva had isolated a variety of amoebae, but no pathogenic Naegleria from the pool water, walls, floors, and filter, and in larger numbers from the garden
soils and pools. He believed that the poolbound amoebae were introduced from the garden by bathers
or swimmers.
As indicated in the earlier (1971) and this report, the pathogenic Naegleria is genetically different
from the wild nonpathogenic N gruben commonly encountered in natural waters, soils, and sewage
effluent. The presence of the latter amoebae may, in fact, have no relation to the presence of
pathogenic Naegleria.
The present findings seem to point to the possibility that the pathogenic Naegleria may lead a
parasitic life in warm-blood animals (terrestial animals living near water, waterfowl, and human beings
themselves). Of particular interest is the fact that very recently the author has found that out of a total
of nine strains of Naegleria isolated from human nasal swabs of children in the summer of 1969 in a
survey of amoebae conducted by the National Center for Disease control in the Richmond, Virginia
area, one exhibited growth and cytopathic effect (CPE) characteristics in primary monkey kidney cell
cultures typical of pathogenic Naegleria. Tests of this strain for pathogenicity in mice will be conducted as soon as possible. Even without the pathogenicity results, there is strong indication that this
strain is most likely that of a pathogenic Naegleria. The findings will be reported in detail in a paper in
preparation by the author, Dr. George Healy, and Dr. Jay Shomaker of the National Center for Disease
Control, Atlanta, Georgia.
97