A VISUAL METHOD FOR DETERMINING THE PHYSIOLOGICAL AGE OF IXODID TICKS IN VIVO

About author:

Razumova I.V., E.I. Martsynovsky Institute of Medical Parasitology and Tropical Medicine I.M. Sechenov Moscow Medical Academy, Moscow, Russia

Acknowledgments:

The author expresses his deep gratitude to Prof. R.L.Naumov and V.P.Gutova (E.I.Martsinovskii Research Institute of Medical Parasitology and Tropical Medicine, Moscow, Russia) for providing access to the collections of ticks. Many thanks are due to A.D.Petrova-Nikitina (Department of Entomology, Moscow Lomonosov State University, Russia) for constructive criticism of the manuscript and very helpful suggestions.

Annotation:

A visual method for determining the physio-logical age of unfed ixodid tick adults in vivo is offered based on the data obtained for the natural populations of ticks of the genera Ixodes and Dermacentor. Alive ticks were immersed in water or physiological solution and studied using the bright background. Several earlier described characteris-tics of the anatomical ageing of ixodid ticks can be seen from the outside by the method, which can be additive to studying the external features conven-tionally used for the physiological age determina-tion. The following criteria of the tick age determi-nation are offered: 1) the body volume; 2) a number of wrinkles and the cuticle coloration; and 3) a complex criterion of the tick cuticle transparency degree for observing the internal organs. The last criterion, which was offered by us earlier [Razumo-va, 1986; 1987], is the leading one in the new method discussed. This criterion is found to have the significant generic specificity. The tables for determination of four basic physiological age peri-ods (I to IV) of ticks of the genera Ixodes and Dermacentor are developed. The method was tested using the natural populations of Ixodes persulcatus, Dermacentor reticulatus and D.marginatus in con-junction with a virological survey. The influence of physiological age of ticks on their susceptibility to the tick-borne encephalitis virus (TBE) and the virus transition to the tick saliva was proved experimentally. The presence of the virus in the tick saliva is found to be not dependent on the virus titer in the tick body [Razumova, Alekseev, 1991]. The new method makes possible the large-scale deter-minations of the physiological age of adult ticks in vivo, which can greatly increase the potential of the method's extensive application.

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