Importancia de la viruela, gastroenteritis aguda y paludismo ... - Oulu

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4.3 Malaria
Malaria is an infectious disease produced by any of the four human malaria parasites:
Plasmodium falciparum, P. vivax, P. malariae and P. ovale. It is transmitted from one
person to another through the infectious bite of a female Anopheles mosquito. The
parasites invade first the liver and then the blood cells of the infected person, producing a
cycle of fever and anaemia. The outcome of the disease depends strongly on the species
of parasite involved. Falciparum malaria tends to be more severe and has more often a
fatal outcome than the other malarias.
Both mosquitoes and parasites have some temperature and humidity requirements
which limit their areas of distribution. Plasmodium falciparum is mainly tropical while P.
malariae and P. vivax are not uncommon in subtropical or temperate areas.
Specifically the strain hibernans of P. vivax was typical in northern Europe (Gilles
1993).
The seasonality pattern of malaria depends on the parasite. It is autumnal for P.
falciparum and malariae and subtropical strains of P. vivax and vernal for P. vivax
hibernans.
Malaria parasites do not stimulate a durable immunity but a certain degree of
resistance can be developed with time in endemic areas. In this situation children are the
most affected by the disease and so are other sections of the population weakened for
different reasons: age, pregnancy, etc. Malaria was not rare in Europe some centuries ago.
It was probably endemic in Finland, especially in the southern part of the country
(Vuorinen 2002, Núñez et al. 2003, Forsius 2004a). P. vivax was the commonest parasite
at the beginning of the 20th century (Sivén 1904, 1907 and 1912 quoted in Vuorinen
2002). It had a low case-fatality rate compared to falciparum malaria. The disease
disappeared from the country after the Second World War (Vuorinen 2002).
5 Results and Discussion
In the thesis, there is one chapter devoted to the analysis of each disease and one for the
compared study of the three. The shortage of space does not make possible to talk here
about all the analysis performed, so only those comparatives will be briefly discussed.
5.1 General results
In total, more than 1.2 million records were analyzed. The number of deaths attributed to
acute gastroenteritis, smallpox or malaria is summarized in Table 3.
The ensemble of causes studied was responsible for about one sixth of all the deaths of
the period. Gastroenteric diseases were the most important, followed by smallpox.
Malaria was comparatively less significant, but considering the relative low case-fatality
rate of vivax malaria, the variety prevalent in Finland, it can be supposed that it was
heavily regulating the health state of those areas in which it was endemic.