scholarly journals Quantifying Leishmania Metacyclic Promastigotes from Individual Sandfly Bites Reveals the Efficiency of Vector Transmission

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Emilie Giraud ◽  
Oihane Martin ◽  
Laith Yakob ◽  
Matthew Rogers
Keyword(s):  
Vector Transmission ◽  
Metacyclic Promastigotes

scholarly journals Large-Scale Seedling Grow-Out Experiments Do Not Support Seed Transmission of Sweet Potato Leaf Curl Virus in Sweet Potato

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 139
Author(s):  
Sharon A. Andreason ◽  
Omotola G. Olaniyi ◽  
Andrea C. Gilliard ◽  
Phillip A. Wadl ◽  
Livy H. Williams ◽  
...  
Keyword(s):  
Sweet Potato ◽  
Large Scale ◽  
Seed Transmission ◽  
Potato Production ◽  
Potato Leaf ◽  
Vector Transmission ◽  
Leaf Curl Virus ◽  
Seed Coats ◽  
Potato Seedlings ◽  
Leaf Curl

Sweet potato leaf curl virus (SPLCV) threatens global sweet potato production. SPLCV is transmitted by Bemisia tabaci or via infected vegetative planting materials; however, SPLCV was suggested to be seed transmissible, which is a characteristic that is disputed for geminiviruses. The objective of this study was to revisit the validity of seed transmission of SPLCV in sweet potato. Using large-scale grow-out of sweet potato seedlings from SPLCV-contaminated seeds over 4 consecutive years, approximately 23,034 sweet potato seedlings of 118 genotype entries were evaluated. All seedlings germinating in a greenhouse under insect-proof conditions or in a growth chamber were free of SPLCV; however, a few seedlings grown in an open bench greenhouse lacking insect exclusion tested positive for SPLCV. Inspection of these seedlings revealed that B. tabaci had infiltrated the greenhouse. Therefore, transmission experiments were conducted using B. tabaci MEAM1, demonstrating successful vector transmission of SPLCV to sweet potato. Additionally, tests on contaminated seed coats and germinating cotyledons demonstrated that SPLCV contaminated a high percentage of seed coats collected from infected maternal plants, but SPLCV was never detected in emerging cotyledons. Based on the results of grow-out experiments, seed coat and cotyledon tests, and vector transmission experiments, we conclude that SPLCV is not seed transmitted in sweet potato.

scholarly journals Mealybug Transmission of Grapevine Leafroll Viruses: An Analysis of Virus–Vector Specificity

2010 ◽  
Vol 100 (8) ◽  
pp. 830-834 ◽  
Author(s):  
Chi-Wei Tsai ◽  
Adib Rowhani ◽  
Deborah A. Golino ◽  
Kent M. Daane ◽  
Rodrigo P. P. Almeida
Keyword(s):  
Plant Pathogens ◽  
Phylogenetic Analyses ◽  
Virus Vector ◽  
Disease Spread ◽  
Virus Species ◽  
Vector Species ◽  
Vector Transmission ◽  
Planococcus Ficus ◽  
Grapevine Leafroll Disease ◽  
Leafroll Disease

To understand ecological factors mediating the spread of insect-borne plant pathogens, vector species for these pathogens need to be identified. Grapevine leafroll disease is caused by a complex of phylogenetically related closteroviruses, some of which are transmitted by insect vectors; however, the specificities of these complex virus–vector interactions are poorly understood thus far. Through biological assays and phylogenetic analyses, we studied the role of vector-pathogen specificity in the transmission of several grapevine leafroll-associated viruses (GLRaVs) by their mealybug vectors. Using plants with multiple virus infections, several virus species were screened for vector transmission by the mealybug species Planococcus ficus and Pseudococcus longispinus. We report that two GLRaVs (-4 and -9), for which no vector transmission evidence was available, are mealybug-borne. The analyses performed indicated no evidence of mealybug–GLRaV specificity; for example, different vector species transmitted GLRaV-3 and one vector species, Planococcus ficus, transmitted five GLRaVs. Based on available data, there is no compelling evidence of vector–virus specificity in the mealybug transmission of GLRaVs. However, more studies aimed at increasing the number of mealybug species tested as vectors of different GLRaVs are necessary. This is especially important given the increasing importance of grapevine leafroll disease spread by mealybugs in vineyards worldwide.

scholarly journals Multi-criteria decision analysis and spatial statistic: an approach to determining human vulnerability to vector transmission of Trypanosoma cruzi

2017 ◽  
Vol 112 (10) ◽  
pp. 709-718 ◽  
Author(s):  
Diego Montenegro ◽  
Ana Paula da Cunha ◽  
Simone Ladeia-Andrade ◽  
Mauricio Vera ◽  
Marcel Pedroso ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
Decision Analysis ◽  
Vector Transmission ◽  
Human Vulnerability ◽  
Multi Criteria Decision Analysis ◽  
Spatial Statistic

scholarly journals Identifying Current and Missing Knowledge in the Control of Pyrethroid-Resistant Triatoma infestans, Vector of Chagas Disease

2017 ◽  
Vol 9 (7) ◽  
pp. 47
Author(s):  
Gonzalo Roca Acevedo ◽  
María Inés Picollo
Keyword(s):  
Chagas Disease ◽  
Chemical Control ◽  
Rational Design ◽  
Pyrethroid Resistance ◽  
Triatoma Infestans ◽  
Vector Transmission ◽  
Pyrethroid Insecticides ◽  
Blood Sucking ◽  
Deltamethrin Resistance ◽  
Metabolic Detoxification

Triatomines are blood-sucking bugs that occur mainly in Latin America. They are vectors of Trypanosoma cruzi, the parasite that causes Chagas disease. Chemical control of Chagas disease´s vectors by using pyrethroid insecticides has been highly successful for the elimination of domestic infestation and consequently the reduction of the vector transmission. However, at the beginning of the 2000s a decrease in the effectiveness of the chemical control of triatomines was detected in several areas from Argentina and Bolivia, particularly in the Gran Chaco eco-region.During the last 15 years, several studies demonstrated the evolution of insecticide resistance in Triatoma infestans and established the presence of different toxicological profiles, the autosomal inherence of resistance, the biological costs of deltamethrin resistance, the expression of deltamethrin resistance thorough the embryonic development, and the main mechanisms of resistance (target-site insensitivity and metabolic detoxification of insecticides).The emergence of pyrethroid resistance coupled with the usual difficulties in sustaining adequate rates of insecticide applications emphasize the need of incorporating other tools for integrated vector and disease control, such as the proposal of the organo-phosphorus insecticide fenitrothion as an alternative chemical strategy for the management of the resistance because it was effective against pyrethroid-resistant populations in laboratory and semi-field trials.New studies on the current situation of presence and spread of resistant populations of triatomines and the acceptance of the use of alternative insecticides are critical requirements in the implementation of strategies for the management of resistance and for the rational design of campaigns oriented to reducing the vector transmission of Chagas’ disease.

Changes in lipophosphoglycan and gene expression associated with the development ofLeishmania majorinPhlebotomus papatasi

Parasitology ◽  
1995 ◽  
Vol 111 (3) ◽  
pp. 275-287 ◽  
Author(s):  
E. M. B. Saraiva ◽  
P. F. P. Pimenta ◽  
T. N. Brodin ◽  
E. Rowton ◽  
G. B. Modi ◽  
...  
Keyword(s):  
Differential Expression ◽  
Fold Increase ◽  
Surface Expression ◽  
Side Chain ◽  
Surface Coat ◽  
Natural Vector ◽  
Metacyclic Promastigotes ◽  
Kinetics Of

SUMMARYStage-specific molecular and morphogenic markers were used to follow the kinetics of appearance, number, and position of metacyclic promastigotes developing during the course ofL. majorinfection in a natural vector,Phlebotomus papatasi. Expression of surface lipophosphoglycan (LPG) on transformed promastigotes was delayed until the appearance of nectomonad forms on day 3, and continued to be abundantly expressed by all promastigotes thereafter. An epitope associate with arabinose substitution of LPG side-chain oligosaccharides, identified by its differential expression by metacyclics invitro, was detected on the surface of a low proportion of midgut promastigotes beginning on day 5, and on up to 60% of promatigotes on days 10 and 15. In contrast 100% of the parasites egested from the mouthparts during forced feeding of 15 day infected flies stained strongly for this epitope. At each time-point, the surface expression of the modified LPG was restricted to morphologically distinguished metacyclic forms. Ultrastructural study of the metacyclic surface revealed an approximate 2-fold increase in the thickness of the surface coat compared to nectomonad forms, suggesting elongation of LPG as occurs during metacyclogenesisin vitro. A metacyclic-associated transcript (MAT-1), another marker identified by its differential expression invitro, also showed selective expression by promastigotes in the fly, and was used inin situhybridization studies to demonstrate the positioning of metacyclics in the anterior gut.

scholarly journals Ascorbate-Dependent Peroxidase (APX) from Leishmania amazonensis Is a Reactive Oxygen Species-Induced Essential Enzyme That Regulates Virulence

2019 ◽  
Vol 87 (12) ◽  
Author(s):  
Lucia Xiang ◽  
Maria Fernanda Laranjeira-Silva ◽  
Fernando Y. Maeda ◽  
Jason Hauzel ◽  
Norma W. Andrews ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Molecular Mechanisms ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Macrophage Infection ◽  
Cutaneous Lesions ◽  
Signaling Mechanism ◽  
Content Type ◽  
Temporal Regulation ◽  
Metacyclic Promastigotes

ABSTRACT The molecular mechanisms underlying biological differences between two Leishmania species that cause cutaneous disease, L. major and L. amazonensis, are poorly understood. In L. amazonensis, reactive oxygen species (ROS) signaling drives differentiation of nonvirulent promastigotes into forms capable of infecting host macrophages. Tight spatial and temporal regulation of H2O2 is key to this signaling mechanism, suggesting a role for ascorbate-dependent peroxidase (APX), which degrades mitochondrial H2O2. Earlier studies showed that APX-null L. major parasites are viable, accumulate higher levels of H2O2, generate a greater yield of infective metacyclic promastigotes, and have increased virulence. In contrast, we found that in L. amazonensis, the ROS-inducible APX is essential for survival of all life cycle stages. APX-null promastigotes could not be generated, and parasites carrying a single APX allele were impaired in their ability to infect macrophages and induce cutaneous lesions in mice. Similar to what was reported for L. major, APX depletion in L. amazonensis enhanced differentiation of metacyclic promastigotes and amastigotes, but the parasites failed to replicate after infecting macrophages. APX expression restored APX single-knockout infectivity, while expression of catalytically inactive APX drastically reduced virulence. APX overexpression in wild-type promastigotes reduced metacyclogenesis, but enhanced intracellular survival following macrophage infection or inoculation into mice. Collectively, our data support a role for APX-regulated mitochondrial H2O2 in promoting differentiation of virulent forms in both L. major and L. amazonensis. Our results also uncover a unique requirement for APX-mediated control of ROS levels for survival and successful intracellular replication of L. amazonensis.

scholarly journals Field Transmission of Grapevine Leafroll Associated Virus 3 (GLRaV-3) by the Mealybug Planococcus citri

Plant Disease ◽  
1997 ◽  
Vol 81 (3) ◽  
pp. 283-287 ◽  
Author(s):  
C. Cabaleiro ◽  
A. Segura
Keyword(s):  
Immunosorbent Assay ◽  
Indirect Evidence ◽  
Enzyme Linked Immunosorbent Assay ◽  
Planococcus Citri ◽  
Spatial Distributions ◽  
Vector Transmission ◽  
Controlled Conditions ◽  
Northwestern Spain ◽  
Rías Baixas ◽  
Growing Region

The spatial distributions of grape plants with symptoms of grapevine leafroll in nine vineyards in the Galician wine-growing region Rías Baixas (northwestern Spain) were analyzed. In five, significant aggregations of diseased plants and/or disease gradients toward one of the borders of the plots constituted indirect evidence of vector transmission by a nonflying vector. From 1991 to 1995, vines from two vineyards were tested for grapevine leafroll associated virus 3 (GLRaV-3) by enzyme-linked immunosorbent assay. In one of these vineyards, which had been virus-free when planted, GLRaV-3 was detected 3 years after planting. In the second, the incidence of GLRaV-3 increased from 33 to 83% between 1991 and 1995. The mealybug Planococcus citri was associated with the infected plants in this vineyard. GLRaV-3 was present in P. citri, and under controlled conditions this mealybug transmitted GLRaV-3 to five of five previously healthy grape plants.

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