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ThemesMath & Science - Dec 02, 2013

Malaria disappears when families get smaller

Researchers have found a new way to curb the spread of the mosquito-borne parasite. Malaria disappears when family size drops to less than four persons per household. This connection was established in an extensive international study which involved researchers from the University of Helsinki.

Photo: Andy Langager / Flickr.com (Creative Commons).

Malaria has been one of the most geographically widespread illnesses in the world and continues to infect more than 200 million people annually. The disease is particularly lethal to children under five years of age.

“With the exception of the Antarctic, indigenous malaria has been found on all continents,” states Curator Larry Huldén from the Finnish Museum of Natural History.

Even Finland has had its share. While the most intense period was in the 18th century, the last major malaria epidemic in Helsinki took place as late as 1902. Even later, indigenous strains of malaria were found for example on the front during the Continuation War. The disease was only eradicated from the country in 1954, and currently all discovered cases originate from abroad.

Nocturnal prey for the mosquito

Malaria is caused by parasitic protozoa transmitted from person to person via mosquito bites. The malaria-bearing mosquitoes are most active at night, so people who sleep in close proximity to one another are ideal for both the mosquitoes and the malaria parasite. Curator Huldén points out that Finns used to live – and more importantly, sleep – in very close quarters.

In the newly published study, Larry Huldén joined University of Helsinki Docent Lena Huldén from the Department of Forest Sciences and researchers from the Canadian University of Guelph to analyse the malaria status of more than 200 countries, and established nearly 60 factors that may contribute to the spread of the disease.

The most significant factor was found to be the size of families. When families had on average two parents and two children, malaria disappeared.

Malaria status was compared with the gross national product, the average temperature and latitude, the amount of forest, the percentage of Muslims in the population, the use of DDT and population density.

“The only exception to this were certain Islamic countries where malaria has been eradicated even though the average number of children has remained high. In such countries, however, the segregation of the sexes dictated by religious tradition reduced the number of persons sleeping in one room to less than four,” explains Curator Huldén.

Individual mosquito nets to the rescue

The significance of family size to the prevalence of malaria has not previously been understood. The last time complete eradication of malaria was attempted in 2007, the focus was on developing a vaccine. Unfortunately this task has proven more difficult than expected, and many drugs have begun to lose their potency as resistant strains emerge. In 2008, many countries had to readopt DDT due to its efficiency in killing mosquitoes.

Published in the Journal of the Royal Statistical Society, the new study proves that the eradication of malaria can be hastened by distributing individual mosquito nets and focusing on measures which lead to the reduction in family size, such as combatting poverty and educating girls.

This article by Laura Hiisivuori (translated from Finnish into English by University of Helsinki Language Services) was originally published in University of Helsinki News.