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A highly purified, inactivated tick-borne encephalitis (TBE) virus particle vaccine has been developed. In this study we report on the efficacy of this new vaccine to protect against TBE virus isolates from different geographical areas of Europe and the Asian part of the USSR.
Host preference of ticks is an important, but still controversial, subject. Recent developments in molecular biology provide new opportunities to test some hypotheses about host preference in a given environment if appropriate specimens are available. Since the unique collection gathered by Dr. P.C. Morel could help achieve this goal, we present an overview of the samples available in his collection.
Ixodes ricinus larvae from the laboratory breed were infected on viraemic suckling mice inoculated with the Skalica strain from the tick-borne encephalitis complex. The strain recovered from individual nymphs on days 39 and 54 after metamorphosis had the markers (ic+, sc-, t-, v-) identical with the original Skalica strain.
The paper presents results of virusological and electron microscope studies of the reproduction of viruses of tick-borne encephalitis and Povassan at mono- and mixed persistent infection of explants of imaginal tissues of Hyalomma anatolicum and H. dromedarii with these viruses. The virus reproduction in explants was observed within 208 to 217 days after the infection. Joint reproduction of two model viruses within 1-2 months after the infection can take place and after that the inhibition of the reproduction of one of the viruses. This inhibition can be of cyclic character.
The sensitivity of different lines of inbred mice to strains of the tick-borne encephalitis complex viruses differing in their biological properties and the degree of attenuation was compared. The mice differing in their genetic characteristics and susceptibility to extraneurally inoculated virus were shown to have different immunological responsiveness to inoculation of an inactivated vaccine antigen.
The preoviposition and oviposition periods, the eclosion periods and numbers of eggs laid by adult ticks of five species, namely Amblyomma variegatum, Boophilus decoloratus, B. geigyi, Hyalomma rufipes and H. truncatum, maintained in a natural habitat were compared with those maintained in semi-natural and artificial habitats. Within the natural habitats, "open" and "shady" sites were distinguished. Maximum oviposition occurred during the peak of the rains in engorged A. variegatum and B. decoloratus, and the numbers of eggs laid by those kept in the natural and semi-natural habitats were significantly lower in the dry season than in the rainy season. Maximum oviposition in engorged H. rufipes kept in the natural habitat occurred during the early rains while minimum oviposition took place during the peak of the rains. Oviposition in engorged H. truncatum was poor among those kept in the natural habitat during the peak and end of the rains. Engorged A. variegatum and B. decoloratus kept in shady sites of the natural habitat laid significantly more eggs than in all other habitats at all seasons, while for H. truncatum and H. rufipes, numbers of eggs laid in the open site were significantly higher than those laid in other habitats at all seasons. In all species investigated, success in oviposition was aided by moisture provided by light to moderate rainfall, while excessive moisture in terms of heavy rainfall adversely affected oviposition.
Boophilus microplus has developed resistance against a range of chemical acaricides which has stimulated the development of alternative methods such as vaccination against ticks. In Cuba, the Bm86-based recombinant vaccine Gavac has been successfully used in a number of controlled laboratory and field trials in cattle against B. microplus. In this paper, we have evaluated Gavac in a large scale field trial wherein 588,573 dairy cattle were vaccinated with the aim to reduce the number of acaricidal treatments. It was found that the number of acaricidal treatments could be reduced by 87% over a period of 8 years (1995--2003). Prior to the introduction of the vaccine, 54 clinical cases of babesiosis and six fatal cases were reported per 1000 animals. Six years later, the incidence of babesiosis was reduced to 1.9 cases per 1000 cattle and mortality reduced to 0.18 per 1000. The national consumption of acaricides in Cuba could be reduced by 82% after the implementation of the integrated anti-B. microplus control program.
1. Isocitrate lyase (Ds-isocitrate glyoxylate-lyase, EC 4.1.3.1) was purified approximately 93-fold from developing embryos of the tick Hyalomma dromedarii. 2. The enzyme requires Mg2+ (Km 2.1 mM) and sulfhydryl compounds for maximal activity and has a pH optimum of 7.4 in phosphate buffer. The Km of the enzyme for isocitrate is 2.4 mM. 3. Data obtained from the pH effect on Km implicate the presence of at least three dissociable groups with pK's of 5.8, 6.8 and 7.4 involved in the enzyme catalysis. 4. At the optimal pH the enzyme is competitively inhibited by oxaloacetate (Ki 0.7 mM) and pyruvate (Ki 0.63 M), noncompetitively inhibited by acetyl-CoA (Ki 1.6 mM) and succinate (Ki 1.35). 5. Inhibition by phosphoenolpyruvate in pH-dependent. The enzyme is noncompetitively inhibited by phosphoenolpyruvate at pH 4.4 (Ki 1.33 mM), 5.6 (Ki 1.7 mM) and pH 8 (Ki 1.36 mM), and competitively inhibited at pH 6.5 (Ki 1.58) and 6.8 (Ki 3.0 mM). 6. The results suggest the regulation of H. dromedarii isocitrate lyase activity during embryonic development by variations in the differential rate of enzyme synthesis an in the intracellular levels of certain metabolites.
We describe an in vitro system that will facilitate molecular analysis of the association between Lyme disease spirochetes and vector cells. We cocultured Borrelia burgdorferi continuously with two tick cell lines, RAE25 (from Rhipicephalus appendiculatus) and IDE8 (from Ixodes scapularis). A clone isolated after twenty-two passages with RAE25 cells had lost the largest (49 kb) plasmid, and probes containing information normally encoded on it, including genes for two surface proteins, hybridized to smaller plasmids. Spirochetes maintained with IDE 8 cells showed a new 43 kb plasmid that hybridized to a probe made from the 49 kb plasmid. After reisolation from hamsters, these spirochetes carried a large plasmid (100 kb) that hybridized with the 49 kb plasmid. These changes may illustrate a plasticity that enables B. burgdorferi to adapt to different environments.
Using computer maps of the epidemic process season variations, tick-borne morbidity and lethality in the areas of the Maritime Territory [correction of Primorsky Region] have been analysed. According to season variations of the epidemic process the territory of Sikhote Alin has been divided into two separate parts--northern and southern, with morbidity peak in June and July, respectively.
Information published between 1567 and 1978 on this subject contains at least 223 titles. They cover medical and veterinary as well as biological aspects. Full bibliographical details of the publication are given. A subject index (to tick species, host species, and diseases transmitted) increases the availability of the data included. Some of the more interesting results of the study are discussed in a short introduction.
The dynamic state of hematoencephalic barrier (HEB) was estimated in Russian tick-borne encephalitic (RTBE) and in meningeal syndrome (Lyme's disease, LD). The enzyme immunoassays of neurospecific proteins in blood serum such as alpha 1-BG and enolase (NSE) were performed in the course of disease. The break of HEB at blood-brain direction was proved in patients with RTBE and LD for the proteins mentioned above. The blood serum NSE levels as well as their dynamics confirmed the functional alteration of brain neurons' permeability in LD and pronounced destruction of such neurons in RTBE. The acute increase of blood NSE concentration was observed within some days before the development of clinical signs of paresis. The authors suppose that the enzyme immunoassays of neurospecific proteins which are of rather high value for HEB permeability and neuronal destruction control may be successfully applied in monitoring of both therapy's efficacy and individualization of pharmacotherapy.
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