Checklist of the family Culicidae (Diptera) in Finland.

A checklist of the Culicidae (Diptera) recorded from Finland is provided.

Checklist of the family Ceratopogonidae (Diptera) of Finland.

A checklist of the family Ceratopogonidae (Diptera) recorded from Finland is provided.

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

BACKGROUND: Plasmodium vivax is the most widespread malaria parasite. It has a dormant stage in the human liver, which makes it difficult to eradicate. It is proposed that a relapse of vivax malaria, besides being genetically determined by the specific strain, is induced by the bites of uninfected vectors. PRESENTATION OF THE HYPOTHESIS: The dormant stage maximizes the possibility for the parasite to reach the vector for sexual reproduction. The advantage would increase if the parasite was able to detect the presence of a new generation of vectors. The sporozoites function both in the vector and in the human hosts. They invade the cells of the salivary gland in the vector and the hepatocytes in the human. Some of the sporozoites develop into hypnozoites in the human liver. It is suggested that the hypnozoite activates when it recognizes the same Anopheles specific protein, which it had previously recognized as a sporozoite to invade the salivary gland in the vector. Another possibility is that the hypnozoite activates upon the bodily reaction by the human on a bite by an Anopheles female. TESTING THE HYPOTHESIS: The connection between the relapse and a new generation of vectors can be documented by simultaneous monitoring of both parasitaemia in humans and the presence of uninfective/infective vectors in the same area with seasonal malaria transmission. Experimental studies are needed to find the saliva components, which trigger the relapse. Although P. cynomolgi in monkeys also has hypnozoites and relapses, testing with monkeys might be problematical. These live in a reasonably stable tropical environment where relapses cannot easily be linked to vectors. The importance of the trigger increases in unpredictable variations in the vector season. IMPLICATIONS OF THE HYPOTHESIS: Artificial triggering of hypnozoites would make the medication more effective and resistance against a protein that the parasite itself uses during its life cycle would not develop. In areas with seasonal vivax malaria it could be used locally for eradication.

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

After the Great Northern War in 1721, Sweden ceased to be an important military power. Instead, the kingdom concentrated on developing science. Swedish research got international fame with names as Carolus Linnaeus, Pehr Wargentin and Anders Celsius. Medical research remained limited and malaria was common especially in the coastal area and along the shores of the big lakes.Already in the beginning of the 18th century Swedish physicians recommended Peruvian bark as medication and they also emphasized that bleeding or blood-letting a malaria patient was harmful. Although malaria was a common disease in the kingdom, the situation was worst in the SW-part of Finland which consisted of the town of Turku and a large archipelago in the Baltic. The farmers had no opportunity to get modern healthcare until Johan Haartman was appointed district physician in 1754. To improve the situation he wrote a medical handbook intended for both the farmers and for persons of rank. Haartman's work was first published 1759 and he discussed all the different cures and medications. His aim was to recommend the best ones and warn against the harmful. His first choice was Peruvian bark, but he knew that the farmers could not afford it. Haartman was appointed professor in medicine at the Royal Academy of Turku in 1765. The malaria situation in Finland grew worse in the 1770's and Haartman analysed the situation. He found the connection between the warm summers and the spring epidemics next year.In a later thesis, Haartman analysed the late summer/early autumn malaria epidemics in the archipelago. Althouh Haartman did not know the connection between malaria and the vector, he gave astute advice and encouraged the farmers to build their cottages in windy places away from the shallow bays in which the Anopheles females hatched. Haartman died in 1788. After his death malaria research in Turku declined. His medical handbook would not be replaced until 1844.

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 long-term 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.

Dynamics of positional warfare malaria: Finland and Korea compared.

BACKGROUND: A sudden outbreak of vivax malaria among Finnish troops in SE-Finland and along the front line in Hanko peninsula in the southwest occurred in 1941 during World War II. The common explanation has been an invasion of infective Anopheles mosquitoes from the Russian troops crossing the front line between Finland and Soviet Union. A revised explanation is presented based on recent studies of Finnish malaria. METHODS: The exact start of the epidemic and the phenology of malaria cases among the Finnish soldiers were reanalyzed. The results were compared with the declining malaria in Finland. A comparison with a corresponding situation starting in the 1990's in Korea was performed. RESULTS AND DISCUSSION: The malaria cases occurred in July in 1941 when it was by far too early for infective mosquitoes to be present. The first Anopheles mosquitoes hatched at about the same time as the first malaria cases were observed among the Finnish soldiers. It takes about 3-6 weeks for the completion of the sporogony in Finland. The new explanation is that soldiers in war conditions were suddenly exposed to uninfected mosquitoes and those who still were carriers of hypnozoites developed relapses triggered by these mosquitoes. It is estimated that about 0.5% of the Finnish population still were carriers of hypnozoites in the 1940's. A corresponding outbreak of vivax malaria in Korea in the 1990's is similarly interpreted as relapses from activated hypnozoites among Korean soldiers. The significance of the mosquito induced relapses is emphasized by two benefits for the Plasmodium. There is a synchronous increase of gametocytes when new mosquitoes emerge. It also enables meiotic recombination between different strains of the Plasmodium. CONCLUSION: The malaria peak during the positional warfare in the 1940's was a short outbreak during the last phase of declining indigenous malaria in Finland. The activation of hypnozoites among a large number of soldiers and subsequent medication contributed to diminishing the reservoir of malaria and speeded up the eradication of the Finnish malaria. A corresponding evolution of Korean malaria is anticipated with relaxed tensions and decreasing troop concentrations along the border between South and North Korea.

Natural relapses in vivax malaria induced by Anopheles mosquitoes.

BACKGROUND: Monthly malaria cases in Finland during 1750-1850 revealed regionally different peaks. The main peak was in late spring in the whole country, but additional peaks occurred in August and December in some regions of Finland. Both primary infections and relapses caused deaths from malaria. The cause and timing of relapses are analysed. METHODS: Monthly data of deaths from malaria in 1750-1850 were successively correlated with mean temperatures of June and July of five years in succession forwards from the current year and through 10 years in succession backwards to identify timing of relapses in Plasmodium vivax. RESULTS: Malaria cases show an increasing correlation with June-July temperatures, with peaks in late summer, midwinter and late spring and then dropped gradually during 2-9 years from the first summer depending on the region. The longest incubation time identified was 8 years and 7 months. CONCLUSION: High correlations of June-July temperatures with deaths from malaria in August to September in the same year indicate a close connection to the new generation of hatching Anopheles mosquitoes. Because rapid sporogony before October is impossible in Finland, the most plausible explanation is an early induction of relapses of vivax malaria by uninfected anophelines. Malaria cases during the winter and the following spring are caused by both primary infections and induced relapses. All subsequent cases represent relapses. It is proposed that the basic relapse patterns in vivax malaria are regulated by anophelines. It is also proposed that the Plasmodium is enhancing blood sucking of Anopheles messeae, which so far has been considered a bad vector.

Endemic malaria: an 'indoor' disease in northern Europe. Historical data analysed.

BACKGROUND: Endemic northern malaria reached 68 degrees N latitude in Europe during the 19th century, where the summer mean temperature only irregularly exceeded 16 degrees C, the lower limit needed for sporogony of Plasmodium vivax. Because of the available historical material and little use of quinine, Finland was suitable for an analysis of endemic malaria and temperature. METHODS: Annual malaria death frequencies during 1800-1870 extracted from parish records were analysed against long-term temperature records in Finland, Russia and Sweden. Supporting data from 1750-1799 were used in the interpretation of the results. The life cycle and behaviour of the anopheline mosquitoes were interpreted according to the literature. RESULTS: Malaria frequencies correlated strongly with the mean temperature of June and July of the preceding summer, corresponding to larval development of the vector. Hatching of imagoes peaks in the middle of August, when the temperature most years is too low for the sporogony of Plasmodium. After mating some of the females hibernate in human dwellings. If the female gets gametocytes from infective humans, the development of Plasmodium can only continue indoors, in heated buildings. CONCLUSION: Northern malaria existed in a cold climate by means of summer dormancy of hypnozoites in humans and indoor transmission of sporozoites throughout the winter by semiactive hibernating mosquitoes. Variable climatic conditions did not affect this relationship. The epidemics, however, were regulated by the population size of the mosquitoes which, in turn, ultimately was controlled by the temperatures of the preceding summer.