Average Household Size and the Eradication of Malaria

Efforts to eradicate malaria during the 20th century succeeded in some parts of the world but failed in others. Malaria also disappeared spontaneously in several countries for reasons that remain an enigma. The connection between malaria and poverty has long been noted. Here we focus on a specific aspect: household size, which has hitherto received little attention. We find strong evidence that when average household size drops below four persons, the probability of malaria eradication jumps dramatically and its incidence in the population drops significantly. This effect is independent of all commonly-studied explanatory variables and was globally valid across all climate zones irrespective of counter measures, vector species, or Plasmodium species. We propose an explanation based on the dispersal mechanism of the parasite. Malaria is transmitted at night by mosquito bite. The mosquito typically spreads the Plasmodium only locally over short distances to new human victims. To survive, the Plasmodium depends on infected humans making social contacts over longer distances. When household size decreases sufficiently, these contacts cross a threshold value that changes the balance between extinctions and replacements and the Plasmodium disappears on its own. We test this interpretation by contrasting our malaria model with dengue fever, which is also poverty-related and mosquito-borne but transmitted differently, namely through daytime exposure. Household size is uncorrelated with dengue incidence, whereas an indicator of outdoor work that is insignificant in the malaria model is highly significant for dengue. We conclude that poverty-induced malaria infection risks are likely to persist, but a focus on reducing effective household size can be a feasible and promising means of its eradication.Malaria;dengue fever, household size, DDT

Dynamics of positional warfare malaria : Finland and Korea compared

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Natural relapses in vivax malaria induced by Anopheles mosquitoes

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

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.Peer reviewe

Activation of the hypnozoite: a part of Plasmodium vivax life cycle and survival

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Checklist of the family Culicidae (Diptera) in Finland

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Checklist of the family Ceratopogonidae (Diptera) of Finland

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Uusien vektorivälitteisten tautien mahdollinen saapuminen Suomeen ilmastonmuutoksen ja ihmisten liikkuvuuden kylkiäisinä

Tässä selvityksessä on käsitelty 50 patogeenia vektoreineen. Se perustuu lähes seitsemänsataan tieteelliseen julkaisuun. Ihmisen kasvava liikkuvuus tuovat patogeeneja nopeasti pitkiä matkoja. Lemmikkien pito ja niiden kuljetukset voivat myös olla uhka ihmisten terveydelle. Vaatetäi on palannut Suomeen ja sen mukana myös vaatetäiden välittämien tautien uhka. Ilmaston muuttuminen luo uusia olosuhteita myös vektorivälitteisille taudeille. Aasian tiikerihyttynen on tärkein Euroopan uusista hyttyslajeista. Tiikerihyttynen voi selvitä talvesta sopivassa mikroilmastossa. Uusia puutiaislajeja voi myös saapua, joko ihmisen toimesta tai muuttolintujen mukana. Suomessa tärkeät arbovirukset ovat hyttysten tai puutiaisten levittämiä. Suomessa esiintyy pogostan tautia sekä puutiaisenenkefaliittia. Useat bakteerit ovat myös hyönteisten tai puutiaisten levittämiä. Suomessa esiintyy kotoperäisenä hyttysten välittämä jänisrutto ja puutiaisten välittämä borrelioosi. Kotoperäinen malaria on hävinnyt Suomesta. Välittäjänä toimiva horkkahyttynen on yleinen koko maassa. Hyönteisiä vektoreina käyttävät ja ihmisissä loisivat sukkulamadot ovat harvinaisia Suomessa. Ne voivat yleistyä tulevaisuudessa. Hyönteisten syömisen kautta tarttuvat patogeenit ovat mahdollinen uhka Suomessa

The first Finnish malariologist, Johan Haartman, and the discussion about malaria in 18th century Turku, Finland

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