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PubMed1983

Immunization against a challenge with insect vector, metacyclic forms of Trypanosoma cruzi simulating a natural infection.

The protective effects of immunization with an antigen derived from epimastigote forms of Trypanosoma cruzi against challenges with vector metacyclic or bloodstream forms of the parasite were investigated. A marked degree of protection was observed in the immunized mice after challenged with bloodstream or insect-transmissible metacyclic forms. High rates of survival in the immunized groups were accompanied by relatively low, shortlasting parasitemias in some of the animals and significant percentages of immunized mice never developed a measurable parasitemia during the course of the experiments. In contrast, all of the non-immunized animals showed high levels of parasitemias. Similar results were obtained whether the metacyclic challenge was by the intraperitoneal or by the ocular route for which conditions mimicking a natural infection were selected. These results emphasize the protection that immunization confers against challenge with insect-transmissible forms of T. cruzi, and the feasibility of protecting a highly susceptible host against an otherwise lethal acute infection similar to one occurring naturally.

Animals↗
PubMed1992

Effect of azadirachtin on the development of Trypanosoma cruzi in different species of triatomine insect vectors: long-term and comparative studies.

Studies were carried out on the effects of azadirachtin on the course of Trypanosoma cruzi infection in the gut of different triatomine vector species. In Rhodinus prolixus the development of T. cruzi clone Dm28c decreased in a dose-dependent manner, and the ED50 of this inhibitory effect was 0.25 microgram azadirachtin/ml bloodmeal. Using this insect, we conducted a long-term experiment which showed that azadirachtin (1.0 microgram/ml bloodmeal) completely blocks the development of T. cruzi even 120 days after treatment with the drug, and after four infectant meals. Similarly, the elimination of T. cruzi in feces and urine was also completely blocked over a period of 50 days after infection in insects treated with azadirachtin. Fifth-instar larvae of R. prolixus, Triatoma infestans, and Dipetalogaster maximus, infected with different clone/strains of T. cruzi, displayed drastic inhibition of trypanosome development when treated with azadirachtin. The discussion of these results focuses on the possibility that azadirachtin may act directly on gut physiology and/or indirectly through the neurosecretory system.

Animals↗
PubMed2004

The biology of xylem fluid-feeding insect vectors of Xylella fastidiosa and their relation to disease epidemiology.

Xylophagous leafhopppers are common and abundant insects of tropical and subtropical environments and play important ecological roles in these ecosystems. The feeding biology of these insects is unique in terms of their high feeding rates and a digestive physiology that allows them to assimilate amino acids, organic acids, and sugars at approximately 99% efficiency. For those species well studied, fluctuations in plant xylem chemistry and tension appear to determine the diurnal and seasonal use of their host plants. Relatively few species of xylem fluid-feeding leafhoppers are considered important pests in commercial agriculture, as they transmit the bacterial plant pathogen Xylella fastidiosa. X. fastidiosa induces diseases of grapevines, citrus, coffee, almond, alfalfa, stone fruits, landscape ornamentals, and native hardwoods for which there is no cure. Two Xylella diseases, citrus variegated chlorosis (CVC) and Pierce's disease (PD) of grapevines, have emerged as important issues within the past decade. In Brazil, CVC became important in the early 1990s and has now expanded throughout many citrus-growing areas of South America and threatens to spread to North America. The recent establishment of the exotic glassy-winged sharpshooter (Homalodisca coagulata) in California now threatens much of the United States' wine grape, table grape, and almond production. The spread of H. coagulata throughout southern California and the spread of CVC northward from Argentina through Brazil exemplifies the biological risks from exotic species. The occurrence and epidemiology of leafhopper-vectored Xylella diseases are discussed.

Animals↗
PubMed1998

Borrelia-infection rates in tick and insect vectors accompanying human risk of acquiring Lyme borreliosis in a highly endemic region in Central Europe.

The methods of spatial statistics were applied to assess the geographical pattern of risk of Lyme borreliosis in Central Bohemia, the Czech Republic, based on retrospective data on disease contractions. The statistical risk was then compared at 15 selected localities with the infection challenge presented by ticks and insects carrying borreliae. Over 5,000 Ixodes ricinus (L.) ticks and 390 haematophagous dipterans were screened by direct immunofluorescence method, and the spatial and seasonal variance of infection rates were studied. Infected ticks were found at each locality throughout the warm season; in nymphs, sample infection rates ranged from 4.9% to 23.1% with a mean of 14.5% in spring, from 7.7% to 28.7% with a mean of 16.1% in summer, and from 7% to 20.6% with a mean of 13.6% in autumn. The statistical risk was found to correlate well with an average nymphal infection challenge, i.e. I. ricinus nymphal abundance x infection rate, at a given locality. Statistically significant cumulation of insect-history recalling patients into several, generally wetland, areas was ascertained; borreliae were revealed in 0.5% of the dipterans examined.

Animals↗
PubMed2006

The spread of Rice dwarf virus among cells of its insect vector exploits virus-induced tubular structures.

Various cytopathological structures, known as inclusion bodies, are formed upon infection of cultured leafhopper cells by Rice dwarf virus, a member of the family Reoviridae. These structures include tubules of approximately 85 nm in diameter which are composed of the nonstructural viral protein Pns10 and contain viral particles. Such tubular structures were produced in heterologous non-host insect cells that expressed Pns10 of the virus. These tubules, when associated with actin-based filopodia, were able to protrude from the surface of cells and to penetrate neighboring cells. A binding assay in vitro revealed the specific binding of Pns10 to actin. Infection of clusters of cells was readily apparent 5 days after inoculation at a low multiplicity of infection with the virus, even in the presence of neutralizing antibodies. However, treatment of host cells with drugs that inhibited the elongation of actin filaments abolished the extension of Pns10 tubules from the surface of cells, with a significant simultaneous decrease in the extent of infection of neighboring cells. These results together revealed a previously undescribed aspect of the intercellular spread of Rice dwarf virus, wherein the virus exploits tubules composed of a nonstructural viral protein and actin-based filopodia to move into neighboring cells.

Actins↗
PubMed1990

Isolations of African horse sickness virus from vector insects made during the 1988 epizootic in Spain.

This paper describes the first isolations of African horse sickness virus (AHSV) from insects in Spain. Seven isolations of AHSV serotype 4 were made; four from Culicoides imicola a known vector of the virus elsewhere, two from mixed pools of Culicoides species not including C. imicola and one from blood engorged mosquitoes. Three further isolations of AHSV serotype 4 were also made from horses kept adjacent to the insect collecting sites. This work presents the first definitive identification of the vectors of AHSV in Spain during the 1987, 88 and 89 epizootics. Suggestions are also made concerning the significance of these findings with regard to the epidemiology of African horse sickness in Spain.

African Horse Sickness↗
PubMed1993

Multiplication of tomato spotted wilt virus in its insect vector, Frankliniella occidentalis.

The accumulation of two proteins, the nucleocapsid (N) protein and a non-structural (NSs) protein both encoded by the S RNA of tomato spotted wilt virus (TSWV), was followed in larvae during development and in adults of Frankliniella occidentalis after ingesting the virus for short periods on infected plants. The amounts of both proteins increased, as shown by ELISA and Western blot analysis, within 2 days above the levels ingested, indicating multiplication of TSWV in these insects. Accumulation of these proteins and of virus particles was further confirmed by in situ immunolabelling of the salivary glands and other tissues of adult thrips. The accumulation of large amounts of N and NSs protein, the occurrence of several vesicles with virus particles in the salivary glands and the massive numbers of virus particles in the salivary gland ducts demonstrate that the salivary glands are a major site of TSWV replication. The occurrence of virus particles in the salivary vesicles is indicative of the involvement of the Golgi apparatus in the maturation of the virus particles and its transport to the salivary ducts.

Animals↗
PubMed2006

A novel Bacteroidetes symbiont is localized in Scaphoideus titanus, the insect vector of Flavescence dorée in Vitis vinifera.

Flavescence dorée (FD) is a grapevine disease that afflicts several wine production areas in Europe, from Portugal to Serbia. FD is caused by a bacterium, "Candidatus Phytoplasma vitis," which is spread throughout the vineyards by a leafhopper, Scaphoideus titanus (Cicadellidae). After collection of S. titanus specimens from FD-contaminated vineyards in three different areas in the Piedmont region of Italy, we performed a survey to characterize the bacterial microflora associated with this insect. Using length heterogeneity PCR with universal primers for bacteria we identified a major peak associated with almost all of the individuals examined (both males and females). Characterization by denaturing gradient gel electrophoresis confirmed the presence of a major band that, after sequencing, showed a 97 to 99% identity with Bacteroidetes symbionts of the "Candidatus Cardinium hertigii" group. In addition, electron microscopy of tissues of S. titanus fed for 3 months on phytoplasma-infected grapevine plants showed bacterial cells with the typical morphology of "Ca. Cardinium hertigii." This endosymbiont, tentatively designated ST1-C, was found in the cytoplasm of previtellogenic and vitellogenic ovarian cells, in the follicle cells, and in the fat body and salivary glands. In addition, cell morphologies resembling those of "Ca. Phytoplasma vitis" were detected in the midgut, and specific PCR assays indicated the presence of the phytoplasma in the gut, fat body and salivary glands. These results indicate that ST1-C and "Ca. Phytoplasma vitis" have a complex life cycle in the body of S. titanus and are colocalized in different organs and tissues.

Animals↗