Expansion of Anopheles maculipennis s.s. (Diptera: Culicidae) to northeastern Europe and northwestern Asia: causes and consequences.

Background: The burden of malaria infection in the modern world remains significant. Specific changes in the relative proportions of malaria vector mosquitoes, Maculipennis Complex species, in the south of Western Siberia over the past 25 years of the 20th century have attracted wide attention as an indicator of their dynamic geographical distribution. In Eurasia, studies of fluctuations in the borders of areas occupied by sibling species of this complex, as well as their relative proportions in the areas where they are sympatric are epidemiologically important.

Methods: Species identity and chromosomal polymorphisms within each population were defined by cytogenetic analysis of polytene chromosomes of third- and fourth-instar larvae and adult females of Anopheles mosquitoes collected over the period from 1973 to 2012. A total of 37 Anopheles samples (3,757 specimens) from the Ukraine, European Russia and the Urals were studied. To identify An. messeae s.l. cryptic species A and B, polymerase chain reaction and restriction fragment length polymorphisms of the second internal transcribed spacer rRNA genes sequences (ITS2 PCR-RFLP) were used.

Results: An. maculipennis s.s. is expanding to the northeast at a speed of approximately 30 km per year. In 2008 or 2009, this species appeared in the Southern Urals. The emergence of An. maculipennis in this region was accompanied by a decrease in the proportions of An. messeae A and An. beklemishevi and by an increase in the proportion of An. messeae B within An. messeae s.l. It is highly likely that the southwestern border of An. beklemishevi distribution area could shift in the same direction as expanding area of An. maculipennis.

Conclusions: The geographical distribution of the Palaearctic mosquito species of the Maculipennis Complex is undergoing a gradual shift. Changes detected in the species distribution can be considered as a component of the biocenotic process triggered by global warming. Both the warming itself and consequent expansion of An. maculipennis s.s. to the northeast, followed by changes in the species composition of Anopheles as well as their relative proportions and fluctuations in the species areas, exacerbate the epidemiology of malaria infection in Eurasia.