Acarina (2001) 9, 277-298

A.N. Alekseev and H.V. Dubinina (2001)
Heterogeneity of the Ixodes persulcatus Schulze (Acari: Ixodidae) population determines the qualities of infected ticks as hosts and vectors of parasites
Acarina 9 (2), 277-298
Abstract: The heterogeneity of the population of Ixodes persulcatus Schulze ticks inhabiting the relatively small St. Petersburg (Russia) suburban forested territory was studied. The studied area is known as a focus of tick-borne encephalitis and borreliosis. The persistent subdivision of the studied population into two phenetically different groups was discovered. The first subgroup includes ticks with exoskeleton anomalies whilst the second one embraces individuals without such anomalies. This phenomenon is associated by the authors with the heavy metal ion pollution. The part of the population with anomalies was as great as 45% in the beginning of the survey (1992) and equaled 31 % at the end (2000), but never was smaller than 25%.
The use of enzyme malatdehydrogenase as a marker permitted to subdivide the whole studied group of ticks into 6 genotypes. Three of them, possessing the heaviest protein (1 homozygote and 2 heterozygote), were most abundant. They were combined in one so-called 1st genogroup. According to our hypothesis the ticks of this genogroup were the richest energetically. All ticks were analysed for the presence of the tick-borne encephalitis virus as well as different species of Borrelia and Ehrlichia. When collecting ticks their reaction to abiotic factors was determined, first of all to the temperature gradients and humidity. The locomotor activity of the collected specimens was estimated in the laboratory. It was stated that most infected ticks with anomalies were met in the 1st genogroup, which was most abundant (more than 80% of the collected specimens). The variances of reactions of ticks to temperature gradients were discovered i.g. to a difference between the soil surface and the litter temperatures. Such variances were connected with the tick pheno- and genotypes and with the types of tick infection by pathogens: by one or another or by several pathogens in different combinations. These variant reactions determined the distinctions in infected or uninfected, normal or anomalous tick appearance from the litter within a day and during the whole season. The highest abundance of infected individuals was recorded among the anomalous ticks. The high intensity of infection and the greater locomotor activity of the heavier infected specimens were also observed among the anomalous ticks. These qualities made them the most dangerous part of the population irrespective to their low, comparatively to normal ticks, abundance. In the surveyed focus, where men checked ticks attached to them (1992-2000), the correlation between morbidity and Borrelia-infected anomalous females' prevalence was stated.
Our research stresses the importance of studying the tick-borne disease vector population heterogeneity in various regions of the world. It is also important to study the complexes of tick parasites and host-pathogen, pathogen 1-pathogen 2, 3 (n) interfaces.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Andrey N. Alekseev

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ixodes persulcatus		Russia (Eur.)