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Studies on Anophelism without Malaria in the Vicinity of Amsterdam

Published online by Cambridge University Press:  10 July 2009

A. de Buck ,
N. H. Swellengrebel  and
E. Schoute
A. de Buck
Affiliation:
Institute of Tropical Hygiene, Amsterdam.
N. H. Swellengrebel
Affiliation:
Institute of Tropical Hygiene, Amsterdam.
E. Schoute
Affiliation:
Institute of Tropical Hygiene, Amsterdam.
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Extract

The question to which we have tried to find an answer is why malaria is almost absent in the southern region (II) within our field of observation, whereas it is endemic in the northern (I). We found Anopheles slightly less frequent in the former, but the difference is irrelevant, and the density of the Anopheline population in Region II is considerable, compared with almost all the European malarious countries we visited and where A. maculipennis is the local vector.

If this difference in the incidence of malaria is at all caused by a difference of the Anopheline faunas of the two regions (which need not be the case), then the biological distinctions are the only important ones. Morphological differences cannot interest us unless they are correlated with the former. Still we began by studying the latter, because they are easier to observe and to measure.

Type
Original Articles
Information
Bulletin of Entomological Research , Volume 17 , Issue 4 , June 1927 , pp. 351 - 371
Copyright
Copyright © Cambridge University Press 1927

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References

* Van Thiel has already drawn attention to the fact that Anopheles from the stations marked here as 15 are larger than those from station 12, and these larger than the mosquitos from station 27. He also noted the insignificant positive correlation between W and MT (Arch. Sch. Trop. Hyg. xxx, Beih. i, 1926, p. 70).

§ There was no difference between house and stable mosquitos, at least not around Amsterdam :—

Of 546 house Anopheles : Th 45 ; Ab 82 ; W 117 ; MT 17·3

Of 571 stable Anopheles : Th 45 ; Ab 83 ; W 117 ; MT 17·3

* The males in the summer generation were smaller than the females : W III, as against 125 in the females.

* This seems to be van der Hoeven's opinion as cited by van Thiel (loc. cit.). Grassi's theory (Re. Ac. Lincei, xxxi, 1922, p. 535) is quite the opposite, but leads to the same conclusion, as the Anopheles bred in brackish water are likewise good carriers—not, however, because of their debility, but in consequence of their particular strength. Alessandrini (in “ La Risicolture, etc. d' Italia,” 1925), on the other hand, declares the big and strong Anopheles bred in the fresh and clear water of rice-fields to be harmless.

† This confirms Swellengrebel's previous observation (Ned. Tijdschr. v. Geneesk. 1922, pp. 350–359).

* Arch. f. Sch. u. Trop. Hyg. xxvi, 1922, and xxviii, 1924.Google Scholar

§ One might be tempted to cite in support of Martini's view the small Anopheles we found in early September in Stations 4 and 29 (Table V), which were bred in August, the hottest month of the year. Their appearance calls to mind some of Martini's breeding experiments (Centralbl. f. Bakt. lte Abt. xciv, 1925, p. 452). Apart from the fact that this year's hottest period was in early July, there are other reasons, especially the decay of certain kinds of vegetation in the breeding-places occurring in the second half of August with a consequent disturbance of food conditions, which can be made to account for this phenomenon in a much more satisfactory way.

* Ann. Inst. Past., xxxvii, 1923, p. 627.Google Scholar

* This is no confirmation of the view that Chara foetida acts as a larvicide. The mortality is due to scarcity of food. The larvae developed just as well among Chara as elsewhere if algae were abundant, and the mortality was just as high among Elodea if they were absent.

* The racial difference between the Anopheline population of Regions I and II explains the absence of correlation between size and number of maxillary teeth. This correlation can be demonstrated (by the method detailed on p. 357), but only within the limits of Region I, i.e., with regard to one race (or population) only ; whereas it fails to show if no care is taken to consider each race (or population) separately.

* Grassi, Ann. d'Igiene, xxxii, 1923, p. 438.Google Scholar

† Consequently we cannot give, for the present, any particulars concerning the comparative incidence of A. maculipennis in houses and stables of Region II. As Swellengrebel (Ned. Tijdschr. v. Geneesk. 1924, 2de Helft, pp. 1112–1125) has shown for the immediate vicinity of Amsterdam, the proportion of the number of Anopheles caught in houses and stables ranges from 1 to 85 in 1920, to 1 to 178 in 1922.

§ When using this method the difference of individual attractiveness for mosquitos of various human donors disappears likewise.

* Swellengrebel, Ned. Tijd. v. Geneesk. 1924, 2nd half, pp. 750–763.Google Scholar

† Korteweg, Geneesk. Bladen, 22e, Reeks No. 1, 1920.

‡ Honig, , Thesis of the Medical Faculty, Univ. of Amsterdam, 1921.Google Scholar