Abstract In this study, 102 water samples containing the pathogen Naegleria fowleri , were compared with control samples matched by sampling site and season. Generally, two controls were available for each sample where N. fowleri was detected. Univariate comparisons revealed a positive association of N. fowleri with: (a) water temperature; (b) maximum and minimum air temperature; (c) bacterial colony counts at 20 and 35°C; (d) the total coliform count; (e) amoebae other than Naegleria and (f) Naegleria sp. other than N. fowleri . By comparison, negative associations were evident with free and total chlorine residuals. A conditional logistic regression analysis indicated that N. fowleri isolation was positively and independently associated with: (a) water temperature; (b) maximum air temperature; (c) bacterial colony counts at 35°C; and (d) low free chlorine residual. Negative associations were found with high temperature tolerant Naegleria and Acanthamoeba , but it is considered that these findings may reflect laboratory technique, not genuine ecological relationships. Evidence is presented that the probability of detecting N. fowleri would vary markedly with the changes in means water temperature and maximum daily air temperature that occur by season. On the basis of temperature variations alone, and assuming a constant free chlorine residual, it is estimated that the probability of N. fowleri occurring (at detectable levels) would be 53 times higher in summer, eleven times higher in autumn, and six times higher in spring, than it would be in the winter. These are very approximate estimations which may not apply to an individual sampling site, nor to periods of extreme temperature. While this is a preliminary study, statistical associations of N. fowleri with a variety of ecological measures have been quantified. More comprehensive and detailed studies are required to further clarify the ecological relationships of this organism.
[1]
J. Corliss,et al.
An illustrated key to freshwater and soil amoebae: With notes on cultivation and ecology
,
1976
.
[2]
M. Fowler,et al.
Acute Pyogenic Meningitis Probably Due to Acanthamoeba sp.: a Preliminary Report
,
1965,
British medical journal.
[3]
Allan Donner,et al.
The Relative Effectiveness of Procedures Commonly Used in Multiple Regression Analysis for Dealing with Missing Values
,
1982
.
[4]
F. M. Wellings,et al.
Isolation and identification of pathogenic Naegleria from Florida lakes
,
1977,
Applied and environmental microbiology.
[5]
J. D. de Jonckheere,et al.
Naegleria lovaniensis new species: isolation and identification of six thermophilic strains of a new species found in association with Naegleria fowleri.
,
1980,
International journal for parasitology.