The role of ixodid ticks in the epizootic process of tick-borne encephalitis in the Maritime Territory

Relative significance of Ixodidae in tick-borne encephalitis epizootic process in the Maritime Territory was determined from many years' data on the carriage of viruses by Ixodidae and results of experimental studies of the selective role of Ixodidae main species. Causes of low rates ow carriage of viruses by Ixodidae in the area under study are revealed.     

Characteristics of the transphase and transovarial transmission of Rickettsia sibirica by ixodid and argasid ticks

Both the specific vector Dermacentor silvarum and the nonspecific one Ornithodoros papillipes are shown to become Rickettsia sibirica infected while sucking blood on the infected guinea pigs. Meanwhile, the specific vector D. silvarum is more sensitive to R. sibirica than the nonspecific. O papillipes. The infectivity of D. silvarum and O. papillipes ticks by R. sibirica was found to be dependent on the intensity of guinea pigs' rickettsemia. Transovarial transmission of Rickettsia has been established for the D. silvarum and O. papillipes ticks, but the Rickettsia titer in the infested D. silvarum larvae exceeded that O. papillipes. Survival of D. silvarum ticks infected by various concentrations of the R. sibirica microbial bodies was found to exceed that of O. papillipes.     

Experimental study of the role of male ixodid ticks in the circulation of the tick-borne encephalitis virus

Regular transmission of the tick-borne encephalitis virus by Ixodidae males feeding on laboratory animals is demonstrated. The virus titres in the male saliva were 0.1-1.5 lgLD50/0.03 ml. It was established that such doses didn't produce tense viremia in white mice or clinical tick-borne encephalitis.     

Vitamin K-dependent carboxylase: possible role of the substrate "propeptide" as an intracellular recognition site

The liver microsomal vitamin K-dependent carboxylase catalyzes the posttranslational conversion of specific glutamate residues to gamma-carboxyglutamate residues in a limited number of proteins. A number of these proteins have been shown to contain a homologous basic amino acid-rich "propeptide" between the leader sequence and the amino terminus of the mature protein. Plasmids encoding protein C, a vitamin K-dependent protein, containing or lacking a propeptide region were constructed and the protein was expressed in Escherichia coli. The protein products were assayed as substrates in an in vitro vitamin K-dependent carboxylase system. Only proteins containing a propeptide region were substrates for the enzyme. These data support the hypothesis that this sequence of the primary gene product is an important recognition site for this processing enzyme.     

The fractions, functions, methods of isolation and the significance for transmission of causative agents of the saliva of ixodid ticks

The authors present a review on the structure and functions of salivary glands of the Ixodidae ticks, attaching to the host's skin by means of a cement fraction: current ideas on the neurohormonal regulation of salivary function are presented. The method of obtaining various saliva fractions--cement-containing and liquid--from unfed infected ticks belonging to 3 genera (Hyalomma, Dermacentor and Ixodes)--by parenteral administration of secretotropic substances is described. The first portions of saliva, both liquid and cement-forming, are shown to contain tick-borne encephalitis viruses in amounts sufficient for the infection of animals. Epidemiological value of the presence of viruses in the cement cork formed in the host's skin and in the first portion of liquid saliva is discussed.     

Anopheles gambiae salivary gland proteins as putative targets for blocking transmission of malaria parasites

Anopheles gambiae is the primary vector of human malaria in sub-Saharan Africa. Invasion of Anopheles salivary glands by Plasmodium sporozoites is a necessary step in the transmission of malaria and is likely to be mediated by specific receptor-ligand interactions. We are interested in identifying putative an A. gambiae salivary gland receptor or receptors for sporozoite invasion as a possible target for blocking malaria transmission. By using monoclonal antibodies against female-specific A. gambiae salivary gland proteins, two molecules, one of 29 kDa and one of 100 kDa, were identified and characterized with respect to the age and blood-feeding process of mosquitoes. In an in vivo bioassay, the monoclonal antibody against the 100-kDa protein inhibited Plasmodium yoelii sporozoite invasion of salivary glands >/=75%. These results show that A. gambiae salivary gland proteins are accessible to monoclonal antibodies that inhibit sporozoite invasion of the salivary glands and suggest alternate targets for blocking the transmission of malaria by this most competent of malaria vectors.     

Bartonellosis and a possible role of Ixodes ticks (family Ixodidae, order Parasitiformes) in the transmission of pathogenic Bartonella bacteria

The papers reviews the literature on bartonellosis and a role of Ixodes ticks, including the representatives of the genus Ixodes, in the circulation and transmission of Bartonella bacteria. It shows that man can be infected with pathogenic Bartonella bacteria by the bite of ticks. The paper also presents data on tick-transmitted human and animal mixed infections, including bartonellosis.     

Argasid ticks as possible vectors of West Nile virus in Israel

Mites and soft ticks collected directly from wild and domestic birds and their nests were tested for the presence of West Nile virus (WNV). The cattle egret argas, Argas arboreus, was collected from the nests of seven cattle egret colonies. Out of 1,000 A. arboreus pools examined, 16 were positive for WNV based on RT-PCR technique. The positive pools were from four nesting colonies of birds. Out of 37 cattle egret squabs examined, 37.8% had serum-neutralizing antibodies to WNV. WNV RNA was also detected in one out of 15 pools of R. turanicus, in one out of 21 pools of O. sylviarum, and in one out of 18 pools of D. gallinae, while 63 pools of A. reflexus, 11 of R. sanguineus, and 30 of Hyalomma spec. were negative. The role of mites and ticks in maintaining the endemic state of WNV in Israel is discussed.     

Evasin‐3‐like anti‐chemokine activity in salivary gland extracts of ixodid ticks during blood‐feeding: a new target for tick control

Ticks exploit many evasion mechanisms to circumvent the immune control of their hosts including subversion of the communication language between cells of the immune system provided by chemokines and other cytokines. One subversive molecule secreted in the saliva of Rhipicephalus sanguineus is Evasin‐3, a structurally unique 7 kDa protein that selectively binds the neutrophil chemoattractants, CXCL8 and (with lower affinity) CXCL1. We compared anti‐human CXCL8 and anti‐mouse CXCL1/KC activities in salivary gland extracts prepared from adult Amblyomma variegatum, Rhipicephalus appendiculatus and Dermacentor reticulatus ticks during blood‐feeding. Both anti‐CXCL8 activity and anti‐CXCL1 activity were detected in all species and in both adult females and males, with consistently higher activity levels against CXCL8. These results suggest that Evasin‐3‐like activity is common amongst metastriate ixodid tick species, and provide further evidence of the importance to ticks in controlling neutrophils during blood‐feeding. As such, Evasin‐3 offers a new target for anti‐tick vaccine development.     

Detection of Anaplasma phagocytophilum in ixodid ticks from equine-inhabited sites in the Southeastern United States

Anaplasma phagocytophilum is a vector-borne, obligate intracellular bacterium that invades the neutrophils and eosinophils of infected individuals, causing granulocytic anaplasmosis. Equine cases have previously been reported in the United States from California, Florida, and Connecticut, but limited surveillance studies in the Southeast have been conducted. The objective of this study was to determine A. phagocytophilum prevalence in Ixodes scapularis ticks at southeastern U.S. horse-inhabited sites to evaluate the potential risk for equine exposure to A. phagocytophilum-infected ticks in these areas. Samples of I. scapularis were collected from selected barrier islands and Georgia mainland sites where feral and domestic equine populations are present, respectively. Ticks were individually tested for infection by amplification of the A. phagocytophilum ankA gene. The collective prevalence of A. phagocytophilum in I. scapularis ticks was 20% (n=808).     

Chemotactic migration of the Lyme disease spirochete (Borrelia burgdorferi) to salivary gland extracts of vector ticks

The migration of Lyme disease spirochetes (Borrelia burgdorferi) toward salivary gland extracts (SGEs) of vector ticks was determined by a modified U-tube chemotaxis assay. Responses of cultured spirochetes to the SGEs were measured by dark-field microscopy at intervals after the initial inoculation. The average numbers of spirochetes that migrated were compared between U-tubes containing either SGEs or phosphate-buffered saline (PBS). Spirochetes showed increased migration in tubes containing SGE, and migration was approximately 10-20-fold higher than that for spirochetes observed in tubes containing PBS. In addition, the span of migration showed no significant difference relative to the origin of spirochete isolation. These results demonstrate that spirochete migration can be enhanced by SGEs from fed vector ticks. This mechanism may contribute to the novel transmission of Lyme disease spirochetes between cofeeding infected and uninfected ticks in nature.