[The longevity of the tick Ixodes ricinus (Acari: Ixodidae) in Central Russia].

The longevity of the tick Ixodes ricinus has been studied on 27 samples from a wild population of the Moscow Region. Ticks were kept in small cages and glass tubes under conditions close to natural. About 2/3 of the specimens collected in spring survived till the next spring and later died out gradually during the second season of their activity. Very few specimens reached the beginning of the third winter in their life, but apparently none of them survived the end of the winter. The life span of males was the same as that of females. No mass activation of adult ticks was recorded in the autumn of the year of their molting. It seems that the rise of the autumnal density of adult ticks depends mainly on the increased activity of the females which molted from nymphs last year.

[Chrological and physiological age of the tick Ixodes ricinus females].

Changes of the physiological age in 3 groups of the laboratory reared Ixodes ricinus females were investigated over the period of 6-16 months. The longevity was studied in 27 groups of the tick females from a wild population during 2 seasons of the tick activity. Physiological age of the tick females was determined at the beginning of the study and then monthly till the end of the study. It was established that physiological ageing takes place during the life of the tick, and the ageing of different females is carried out non-uniformly. Physiologically young females (of the second physiological age) in the groups of laboratory reared ticks were occurred right up to 11th month after molting (including 4 months of hibernation in a refrigerator). Ticks of the second physiological age were occurred in the groups from wild populations after one or two periods of hibernation. Hence, in natural conditions some females may be physiologically young both in the first and second seasons of the ticks' activity. On the other hand, physiologically old tick females (of the 4th physiological age) appeared in the groups in a month after molting. The supposition is proposed that the tick population is heterogeneous by the rate of the individual ageing. It means that different specimens differ by the rate of consumption of their storage compounds i.e. by the intensity of metabolism. Such difference may be a cause of the variability in chemical conditions in the gut of the tick being the habitat of Borrelia.

[The affection of the population with Borrelia and the incidence of Lyme disease].

The proportion of Lyme borreliosis seropositive residents in a number of Russia is 1-2 thousand times greater than that of officially notified patients. It is suggested that due to the ability of Lyme borreliosis to manifest in the late periods after infection, the time and chronicity of the infection, the number of officially recorded patients may significantly increase due to the manifestation of the disease in seropositive apparently healthy (at the moment of an examination) dwellers. There is evidence for that it is expedient to follow up seropositive residents and tick-bitten individuals.

[Evaluation of the occurrence of borreliae in the ticks]. / Otsenka porazhennosti kleshchei borreliiami.

The paper shows it necessary to estimate the average number of borreliae in the infected ticks, by using the geometric mean of a sign rather than the arithmetic mean.

[Longevity of forest and taiga ticks (Ixodidae) infected and non-infected with Borrelia burgdorferi groups]. / Prodolzhitel'nost' zhizni lesnogo i taezhnogo kleshchei (Ixodidae), zarazhennykh i ne zarazhennykh borreliiami gruppy Burgdorferi.

A life longevity of Ixodes ricinus and I. persulcatus have been examined in laboratory conditions. It was found that specimens infected with borreliae live slightly longer than non-infected ones (difference is not reliable); females live 1.5 times longer than males; I. ricinus lives 2-4 times longer than I. persulcatus. It is suggested that I. persulcatus has a higher rate of metabolism than I. ricinus and that the latter species obtains an ability to survive after the last moult two winters and keep an activity in two summer seasons not counting the year of moulting.

[Borrelia burgdorferi s.s. length and its variability]. / Dlina Borrelia burgdorferi s.s. i ee izmenchivost'.

The length of 469 Borreliae burgdorferi s.I. from the Ixodes ricinus and I. persulcatus images collected in the Moscow Region, that of 5433 B. burgdorferi s.s from the I. persulcatus nymphs and images cultured at a laboratory, and B. burdorferi s.s. grown on the BSK-II (1 and 10 passages) were measured. There was a wide range of variations in the length of specimens (3-74 microns) and in those of this group average sizes (10.7-24.8 microns). The lengths of Borelliae from natural and laboratory ticks after their molt were 17-18 microns. When the ticks were kept in the refrigerator as long as 1-2 years, the length of Borreliae decreased to 10.7-10.9 microns, upon multiple (10) passages on the BSK-II medium, their lengths increased to 24.8 microns (the differences being significant). When the length of Borreliae reduced due to their keeping in the refrigerator, their pathogenicity for albino mice diminished. This disappeared after multiple BSK-II medium passages. It is suggested that the length of Borreliae may serve as a marker of their pathogenicity.

[A laboratory model of the parasitic system of Lyme disease]. / Laboratornaia model' parazitarnoi sistemy bolezni Laima.

A laboratory model of the parasitic system of Lyme borreliosis (LB) with Ixodes persulcatus and Borrelia burgdorferi s.s. underwent 5 epizootic cycles (Cycle I transition of Borreliae by the scheme a tick-->a mouse-->a tick corresponds to the seasonal cycle). A group of 5-6 mice was inoculated with the suspension of infected nymphs by the intracutaneously route and 35-45 days later intact tick larvae or nymphs were fed on them. In the first three cycles, 40-100% of mice in a group (a total of 33 of 59) were susceptible, but 3 of 11 groups of mice were not inoculated. 20-50% of larvae and 75-92% of nymphs were susceptible on the infected mice. The mean geometric abundance of borreliae was 2.8-6.3 cells per 100 fields of vision in the nymphs infected in the larval phase and 16.1-29.5 cells in the image phase. In cycle IV, 2 of 6 groups of mice were unsusceptible to borreliae and 5 of the 17 mice from 4 groups got infected. One mouse died from Lyme borreliosis when larvae were fed on it. The nymphs remolted from underfed larvae were infected in 62.2% of cases, the mean geometric abundance in these nymphs was 5.7% per 100 fields of vision. A total of 3.2-14.7% of the ticks fed on the remaining 4 mice were infected and the abundance of boreliae was 1-2 per 100 fields of vision. In cycle V, one of 12 mice got infected, the infection rate in nymphs was 9.1%, the abundance of borreliae was 1 per 100 fields of vision. Thus, as the number of epizootic cycles increases, the proportion of infected mice, that of ticks infected on these mice on feeding, and the abundance of borreliae in the infected ticks decrease. Moreover, there was a reduction in the length of borreliae reduced from 17-18 mm to 10-11 mm and in the duration of multiplication and preservation of borreliae in the infected ticks and there was concurrently an increase in the duration of development of an infectious process in mice. It is suggested that the population of borreliae consists of 2 morphophysiological groups or more. During cultivation of the laboratory model of the parasitic system of Lyme borreliosis, a group of borrelia that are short and slightly pathogenic for mice had got many points in its favour. A five-fold procedure of artificial election of precisely defining this group set the model on the verge of disappearance. The capacity of the populations of borreliae to alter their properties rapidly and fundamentally suggests that there might be violent annual fluctuations in human morbidity.

[Mixed infection in ticks: a rule or an exception?]. / Mikstinfektsiia u kleshchei: pravilo ili iskliuchenie?

A hypothesis for the independence of acts of infection in ticks with pathogens from each other in mixed infection has been tested on the basis of the data available in the literature. In most cases the number of ticks with mixed infection is consistent with the independence hypothesis and fails to reinforce the statement that there is antagonism of pathogens. But in some reports the number of mixed-infected ticks is 3-13 times higher than the calculated number according to the accepted hypothesis. These facts suggest that the natural tolerance of ticks to pathogens due to primary infection may be reduced. Other possible reasons for differences in the actual and calculated number of mixed infected ticks are also discussed.

[The results of a study of the acaricidal activity of the preparation Fewry-med]. / Rezul'taty izucheniia akaritsidnoi aktivnosti preparata F'iuri-med.

The acaricidal activity of Fewry-med (10% zeta-zipermethrin) against Ixodes persulcatus was studied in laboratory and field conditions. The drug's doses of 0.01-0.005 g/m2 (as calculated for active ingredient) provided 100% death of ticks when forest areas (Tyumen' Province) were treated. The efficiency of treatment preserved within 31 days (the follow-up period). When Fewry-med was used in a dose of 0.005 and 0.01 g/m2, the soil levels of zeta-zipermethrin was lower than the maximum allowable concentration at days 7 and 14 after treatment. In the treated areas, the size of crawling representatives of the entomofauna restored at day 25. The drug may be recommended for industrial trials.

[The exploratory activity of the Borrelia-infected taiga tick Ixodes persulcatus]. / Poiskovaia aktivnost' zarazhennykh borreliiami taezhnykh kleshchei Ixodes persulcatus.

The infection with Borrelia burgdorferi s. l. increases the questing activity of adults and nymphs of the taiga tick Ixodes persulcatus. High temperature inhibits the moving and questing activities of the infected ticks in a greater extent than that in the non-infected ones. Than more borreliae per a specimen of tick are present, the more tick's activity is affected.

[An experimental study of the capacity of the rat mite Ornithonyssus bacoti (Hirst, 1913) to ingest, maintain and transmit Borrelia]. / Eksperimental'noe izuchenie sposobnosti krysinogo kleshcha Ornithonyssus bacoti (Hirst, 1913) vosprinimat', sokhraniat' i peredavat' borrelii.

For the first time a possibility of the gamasina mites' O. bacoti participation in Lyme disease spirochetes' circulation has been demonstrated. It has been experimentally shown that Borrelia burgdorferi s.l. are received by O. bacoti, survive in them for at least 21 days and are transmitted to white mice through mites' bites. Mice's infestation has occurred in 23% of cases. It is suggested that other bloodsucking gamasina mites inhabiting the Lyme borreliosis reservoir rodents nests may be capable of participating in borrelia circulation in the Lyme disease endemic areas.

[Propagation of the pathogen of Lyme disease Borrelia burgdorferi in the ticks Ixodes persulcatus]. / Razmnozhenie vozbuditelei bolezni Laima Borrelia burgdorferi v kleshchakh Ixodes persulcatus.

An increase of the number of Borrelia burgdorferi s. l. in nymphs was observed 3-4 months later the moulting and during the following 4-5 months. The percent of infected ticks remained unchanged. The reproduction of spirochete was going not only at a room temperature, but also at a lower temperature, 3-5 degrees (imitation of hibernation conditions). An increase of the spirochete density was especially well marked, when the ticks were maintained under fluctuated daily conditions. We have found out the difference in the transphase transmission. Almost all larvae and nymphs infected by a bloodsucking retained spirochetes after moulting (the first transphase transmission). When the nymphs infected at larval stage were fed on an uninfected mouse, only 30% of imago ticks retained the spirochetes (the second transphase transmission).

[A new generation of acaricide--attractant acaricidal granules]. / Akaritsid novogo pokoleniia--attraktivno-akaritsidnye granuly.

The paper gives a brief account of the earlier results of papers with the development of attractive acaricidal granules (AAGs) and the results of their field tests in Tyumen Province and Krasnoyarsk Territory. AAGs in combination with sumithion yielded the best results than those with permethrin: their efficacy was over 90% and their action lasted 1.5 months.

[The reaction of taiga ticks to an attractant. II. The rates of removing ticks from a population]. / Reaktsiia taezhnykh kleshchei na attraktant. Soobshchenie II. Tempy iz''iatiia kleshchei iz populiatsii.

Catching ticks on the attractant-moistened napkins and on the flag (control) under field conditions during 5 days has demonstrated that a population of taiga ticks on the treated areas can be killed within 1-2 weeks when attractive-acaricidal granules are applied.

[The reaction of taiga ticks to an attractant. III. The use of attractant-acaricidal granules in a field experiment]. / Reaktsiia taezhnykh kleshchei. III. Primenenie attraktivno-akaritsidnykh granul v polevom éksperimente.

On June 15, a total of 300 granules were placed at 1-m intervals on the sides of a concrete-covered road located along the steep slope of a valley. The number of ticks on 300-m plots decreased from 557 (before the experiment) to 55 on June 24 and to 11 on June 27. On the 200-m control plot there were 256, 280 and 168 ticks, respectively, in the same periods of time. Thus, the efficiency of tick eradication was 91 and 97% on days 9 and 12, respectively.

[The reaction of taiga ticks to an attractant. 1. The experimental contact of nymphs with attractant-acaricidal granules]. / Reaktsiia taezhnykh kleshchei na attraktant. Soobshchenie 1. Kontakt nimf s attraktivno-akaritsidnymi granulami v éksperimente.

Four experimental variants used the following: 1) granules only from a filler (control); 2) those from a filler and an attractant; 3) and 4) those from a filler, an attractant, and a toxicant (permethrin or lambda cigalothrin, respectively). Each experiment used 20 nymphs of the first laboratory generation. 90 and 25% were in contact with attractive and control granules, respectively. Out of the nymphs in experiments 3 and 4 granules, 94 and 100% died. The contacts of 4 sec or more duration led to death. The experimental findings suggest that the designing and application of attractive acaricidal granules in the foci of tick-borne encephalitis and Lyme's disease are promising.

[The rate of infection of the taiga tick with Borrelia in the western Sayan]. / Zarazhennost' taezhnogo kleshcha borreliiami v Zapadnom Saiane.

The paper provides microscopic findings of taiga ticks collected for the causative agent of Lyme's disease in May to July 1993 in the West Sayan . A total of 1,016 specimens were examined, among them 124 (12.2%) were found to have Borreliae. The areas were demonstrated to vary greatly with their epidemiological risk. The number of ticks and hence the epidemiological risk were the most in the low-mountain and chern taiga areas.

[The acaricidal activity of pyrethroids against Ixodes persulcatus P. Sch. nymphs]. / Akaritsidnaia aktivnost' nekotorykh piretroidov po otnosheniiu k nimfam Ixodes persulcatus P. Sch.

The efficiency of 9 drugs based on cipermethrin, deltamethrin, permethrin, lambdacigalothrin, ciphenothrin, phenothrin against hungry I. persulcatus nymphs was studied in the laboratory setting. The values LD50 and LD99 (in g of an active ingredient per m2) were found when the nymphs got into contacts with the treated filter paper for 10 sec and 1 min. The paper discusses whether the pyrethroids as part of attractant-acaricidal granules can be used to suppress the size of ticks in the tick-borne encephalitis foci.