The decline of malaria in Finland – the impact of the vector and social variables

Lena Hulden, Larry Huldén

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Background: Malaria was prevalent in Finland in the 18th century. It declined slowly without
deliberate counter-measures and the last indigenous case was reported in 1954. In the present
analysis of indigenous malaria in Finland, an effort was made to construct a data set on annual
malaria cases of maximum temporal length to be able to evaluate the significance of different factors
assumed to affect malaria trends.
Methods: To analyse the long-term trend malaria statistics were collected from 1750–2008.
During that time, malaria frequency decreased from about 20,000 – 50,000 per 1,000,000 people
to less than 1 per 1,000,000 people. To assess the cause of the decline, a correlation analysis was
performed between malaria frequency per million people and temperature data, animal husbandry,
consolidation of land by redistribution and household size.
Results: Anopheles messeae and Anopheles beklemishevi exist only as larvae in June and most of July.
The females seek an overwintering place in August. Those that overwinter together with humans
may act as vectors. They have to stay in their overwintering place from September to May because
of the cold climate. The temperatures between June and July determine the number of malaria
cases during the following transmission season. This did not, however, have an impact on the longterm
trend of malaria. The change in animal husbandry and reclamation of wetlands may also be
excluded as a possible cause for the decline of malaria. The long-term social changes, such as land
consolidation and decreasing household size, showed a strong correlation with the decline of
Plasmodium.
Conclusion: The indigenous malaria in Finland faded out evenly in the whole country during 200
years with limited or no counter-measures or medication. It appears that malaria in Finland was
basically a social disease and that malaria trends were strongly linked to changes in human
behaviour. Decreasing household size caused fewer interactions between families and accordingly
decreasing recolonization possibilities for Plasmodium. The permanent drop of the household size
was the precondition for a permanent eradication of malaria.
Original languageEnglish
JournalMalaria Journal
Volume8
Issue number94
Pages (from-to)1-9
Number of pages9
ISSN1475-2875
DOIs
Publication statusPublished - 7 May 2009
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 1181 Ecology, evolutionary biology

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