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At least 1,549 records · Page 86Linked to original sources
PubMed1989

Enhancement of virus transmission by tick salivary glands.

Previous studies have demonstrated that Thogoto (THO) virus is transmitted from infected to uninfected ticks cofeeding on an uninfected guinea-pig, although the guinea-pig does not develop a detectable viraemia. To investigate this mode of transmission, guinea-pigs were infected with uninfected Rhipicephalus appendiculatus nymphs prior to inoculation with either a mixture of THO virus and tick salivary gland extract, or with THO virus alone. The number of ticks that acquired the virus from feeding on animals inoculated with a mixture of virus and salivary gland extract was 10-fold greater than the number that became infected by feeding on animals inoculated with virus alone. The increase in the number of ticks that became infected was greatest when the salivary glands used in the inoculum were derived from uninfected ticks, which had partially fed for a period of 6 days. Viraemia was not detected in any of the guinea-pigs tested during the experiments. These results indicate that THO virus transmission is enhanced by factor(s) associated with the salivary glands of ticks, and that these factor(s) may facilitate 'non-viraemic' transmission between infected and uninfected ticks.

Animals↗
PubMed1995

Expression and characterization of the reverse transcriptase enzyme from type 1 human immunodeficiency virus using different baculoviral vector systems.

To produce the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) in amounts required to study its structure and function, the p66 enzyme subunit was expressed using two different baculovirus vectors in Sf158 insect host cells. Both vectors permitted an efficient HIV-1 RT expression. The resulting products were purified up to 90% homogeneity, characterized, and investigated for their susceptibility to digestion with various proteases. The recombinant baculoviral RT obtained with the pAc373 expression vector was purified as a p66/p60 heterodimer. The recombinant His-RT was expressed with the pBlueBacHis vector. Thereby, the protein was tagged with an N-terminal hexahistidine peptide and it was purified as a p70/p70 homodimer. The two enzymes differed in their specific activity, kinetic properties, and in vitro activation by viral and non-viral proteases. The recombinant His-RT exhibited a lower specific activity than the recombinant RT. The latter yielded enzyme activities as high as an Escherichia coli-expressed RT. Removal of the hexahistidine tag from the recombinant His-RT by digestion with enterokinase resulted in a complete loss of enzyme activity. Thus, the hexahistidine tag might be an intrinsic part of the active recombinant His-RT.

Animals↗
PubMedDate not supplied

Density of sand flies (Diptera: psychodidae) in domestic and wild animal shelters in an area of visceral Leishmaniasis in the state of Rio Grande do Norte, Brazil.

The objective of the present study was to determine the association of sand flies with the presence of domestic and wild animals in the peridomiciliary area. The sand flies were collected using direct aspiration and CDC light traps placed in animal shelters. The results suggest that different sand flies species have different behavioral characteristics in an apparent preference for animal baits and that Lutzomyia longipalpis and Lu. evandroi were the most eclectic species regarding their biotope choice. Lu. longipalpis showed a distinct preference for horses and Lu. evandroi for armadillos.

Animals↗
PubMed2006

Detection of a malaria parasite (Plasmodium mexicanum) in ectoparasites (mites and ticks), and possible significance for transmission.

Two species of sandflies (Lutzomyia) are competent vectors of Plasmodium mexicanum, a malaria parasite of lizards. The very patchy distribution of sites with high P. mexicanum prevalence in the lizards, and often low or even nil sandfly density at such sites, provoked an evaluation of 2 common lizard ectoparasites, the tick Ixodes pacificus and the mite Geckobiella occidentalis, as potential passive vectors. Plasmodium sp.-specific polymerase chain primers were used to amplify a long segment of the mitochondrial cytochrome b gene that is unlikely to survive intact if the parasite cells are killed within a blood-feeding arthropod. The segment was strongly amplified from sandflies (the positive control for the method) from 1 to 96 hr postfeeding on an infected lizard. For ticks, the gene fragment was poorly amplified at 0 hr postfeed, and not amplified after 2 hr. In contrast, strong amplification of the parasite DNA was observed from mites from 0 to 20 hr postfeed, and weak amplification even at 96 hr.

Animals↗
PubMed2006

Highly efficient yeast-based in vivo DNA cloning of multiple DNA fragments and the simultaneous construction of yeast/ Escherichia coli shuttle vectors.

In vivo recombinational cloning in yeast is a very efficient method. Until now, this method has been limited to experiments with yeast vectors because most animal, insect, and bacterial vectors lack yeast replication origins. We developed a new system to apply yeast-based in vivo cloning to vectors lacking yeast replication origins. Many cloning vectors are derived from the plasmid pBR322 and have a similar backbone that contains the ampicillin resistance gene and pBR322-derived replication origin for Escherichia coli. We constructed a helper plasmid pSUO that allows the in vivo conversion of a pBR322-derived vector to a yeast/E. coli shuttle vector through the use of this backbone sequence. The DNA fragment to be cloned is PCR-amplified with the addition of 40 bp of homology to a pBR322-derived vector. Cotransformation of linearized pSU0, the pBR322-derived vector, and a PCR-amplified DNA fragment, results in the conversion of the pBR322-derived vector into a yeast/E. coli shuttle vector carrying the DNA fragment of interest. Furthermore, this method is applicable to multifragment cloning, which is useful for the creation of fusion genes. Our method provides an alternative to traditional cloning methods.

Cloning, Molecular↗
PubMed1979

Onchocerciasis transmission potentials of four species of Guatemalan simuliidae.

Two complete days of collections and dissections of all black fly species landing on two persons infected with Onchocerca volvulus were made at monthly intervals for 13 months within a single endemic area of Guatemala. A comparison of the infective biting densities and transmission potentials showed that Simulium ochraceum was the only significant vector.

Adult↗
PubMed1995

Transient expression of a promoter-reporter construct in differentiated adult salivary glands and embryos of the mosquito Aedes aegypti.

Vector-borne pathogens develop in close association with specific tissues in their insect hosts. Efforts are being made to characterize insect genes that are expressed in tissues that have important roles in pathogen propagation. Successful transfection and expression of exogenous genes in terminally differentiated tissues of insects has previously proven difficult. Here we report a method that should allow the analysis of genes that are expressed in adult tissues and organs. Transient expression assays have been developed using the salivary glands of the mosquito, Aedes aegypti, which can now be used to analyze salivary gland-specific promoter sequences. A liposome-based transfection reagent was used to transfect cultured adult salivary glands with a DNA construct carrying the luciferase reporter gene under the control of the Drosophila melanogaster heat shock 70 promoter. Luciferase activity was detected in glands 18-20 hr post-transfection. This assay can now be used to determine the regulatory activity of other putative promoter sequences from salivary gland-specific genes. Alternatively, the assay may be used to study the effect of recombinant gene expression on parasite invasion and development. In addition, transient expression of gene constructs in embryos is shown to be a powerful tool for analyzing genes that are expressed at this stage of the mosquito life cycle.

Aedes↗
PubMed2005

Field-user acceptability of new camouflage face paint formulations in the Republic of Korea.

New formulations of camouflage face paint (CFP), one with 30% N,N-diethyl-3-methylbenzamide (DEET) and the other without DEET, were evaluated for soldier-user acceptability during a military field-training exercise in the Republic of Korea. Soldiers testing the CFP formulations were members of one of four U.S. Army infantry companies (A, B, C, or D). The formulations were evaluated while soldiers participated in simulated combat exercises for 5 days during hot, humid summer weather in Korea. Results showed that soldiers found both of the new formulations easier to apply (91.3% of respondents who used CFP without DEET and 87.9% of respondents who used CFP with DEET) and remove (82.6% without DEET and 81.2% with DEET) than the previous standard military-issue CFP. Soldier acceptability was higher for the new CFP formulation with 30% DEET (70.5%) than for the formulation without 30% DEET (52.9%). Soldiers recommended it more frequently (70.5%) than the formulation without 30% DEET (50.0%). The new CFP formulation with 30% DEET was rated more often (79.5%) as either good or excellent than the new formulation without 30% DEET (67.4%). Soldiers reported that the CFP formulation with 30% DEET more successfully camouflaged the face (92.7%) than the formulation without 30% DEET (80.0%).

Adolescent↗
PubMedDate not supplied

[The possible consequences of the probable global warming of the climate for the spread of blood-sucking ectoparasites and the pathogens they transmit].

The paper reviews the causes and possible consequences of the warming-up of global climate. Probable changes in the areas of vectors and blood-suckers, which are most important for Russia, are analyzed. The vectors of malaria and tick-borne pathogens were used as special subjects of prognostic survey. The paper shows it necessary to computer-aided simulate possible consequences of climatic warming-up for changes in the parasitological situation in the Russian Federation.

Animals↗
PubMed2003

[Plasmodium falciparum: epidemiology and man-mosquito transmission and infection in the vector].

The level of malaria transmission is usually estimated by some entomological parameters (entomological inoculation rate or reproductive rate and its seasonal variations). However, only one aspect of the malaria transmission is explored by this way, i.e. the transmission of Plasmodium from mosquito to man. The transmission from man to mosquito, the development of parasite in the mosquito midgut, and the role of transmission blocking immunity remain poorly documented. Recent studies on vaccination with gamete antigens showed that transmission blocking immunity, and the natural infectiousness of gametocytes after treatment underlined the need for taking into account a new aspect of malaria epidemiology concerning the transmission of Plasmodium from man to mosquito. In this paper, authors propose and discuss different new indicators and methods to improve our knowledge on malaria epidemiology.

Animals↗
PubMed2003

[Plague control in Madagascar: evaluation of the efficacy of Kartman baitboxes in urban areas].

A method associating an anticoagulant rodenticide and an insecticide called Kartman bait-box aimed both at fighting reservoir and vectors of plague. It was evaluated in two neighbourhoods of Antananarivo (Madagascar) from October 2002 to May 2003. It involved the local community in the control. The study was carried out in Ambodirano-Ampefiloha refered as treated neighbourhood in which the Kartman bait box were laid out with an anticoagulant rodenticide and an insecticide with a rapid action versus a "pilot neighbourhood", Ankorondrano-Andranomahery in which the boxes were provided with non poisoning bait and non insecticidal white powder. The rodenticide used was Baraki (difethialone 25 ppm) and the insecticide was a powder of Propoxur 3%. The evaluation of effectiveness of this method was based on the four following parameters: (1) the number of dead rats collected daily inside and in the vicinity of the houses, (2) the daily number of baits non consumed in the Kartman bait box, (3) the cheopis index of the rats trapped using the BTS trap, and (4) the flea carrier index of the rats captured monthly with BTS trap. The cheopis index and the flea carrier index of the rats were calculated monthly. The number of rats that died in the treated neighbourhood was of 968 versus 3 in the pilot neighbourhood. The other parameters reached a stable level after 3 months. Between days 120 and 180, the mean number of unconsumed baits was 2.79 in the treated neighbourhood versus 0.14 in the pilot neighbourhood, the flea carriage (percentage of parasitized hosts) was 0% versus 61% in the pilot neighbourhood, and the cheopis index was 0.0 versus 5.0 in the pilot neighbourhood. This study demonstrates that Kartman bait-boxes reached the rat borne and the vectors of plague found in urban area. We propose to use this method extensively both during epidemic and inter-epidemic contexts.

4-Hydroxycoumarins↗
PubMed1985

Experimental study of the reproduction of Karshi virus (Togaviridae, flavivirus) in some species of mosquitoes and ticks.

The strain Kaz-816 of Karshi virus was isolated in 1976 from H. asiaticum ticks collected in the North of Central Asia (Alma-Ata region of the Kazakh Soviet Socialist Republic). Both ticks and mosquitoes can be vectors of Karshi virus as proved experimentally by reproduction of the virus in Hyalomma asiaticum and Dermacentor daghestanicus ticks and Culex pipiens molestus, Anopheles atroparvus an Aedes aegypti mosquitoes as well as by transmission to newborn mice by the bite of infected mosquitoes.

Aedes↗