Immunogold localization of tobravirus 2b nematode transmission helper protein associated with virus particles.
(73/1021)
Transmission of the tobraviruses Tobacco rattle virus (TRV) and Pea early-browning virus (PEBV) by trichodorid vector nematodes requires the viral coat protein (CP) and the 2b protein, a nonstructural protein encoded by RNA2, the smaller of the two viral genomic RNAs. It is hypothesized that the 2b protein functions by interacting with a small, flexible domain located at the C-terminus of the CP, forming a bridge between the virus particle and the internal surface of the vector nematode feeding apparatus. Antibodies specific for the 2b protein of PEBV or TRV did not bind to virus particles that were adsorbed to electron microscope grids and were not able to trap virus particles from extracts of infected plants. However, electron microscopy of thin sections of plants infected with PEBV probed with 2b-specific antibodies which were further gold-labeled showed that the 2b protein localizes exclusively to virus particles. Similarly, immunogold localization studies showed that the 2b protein of TRV isolate PaY4 is associated only with TRV PaY4 virus particles. When a recombinant TRV encoding the PaY4 2b protein and the CP from TRV isolate PpK20 was examined, the 2b protein could not be detected by Western blotting and in IGL experiments was not associated with virus particles. These results suggest that in the absence of a specific interaction between compatible CP and 2b proteins, the 2b protein does not accumulate. (+info)
Freshwater snails and Schistosomiasis mansoni in the State of Rio de Janeiro, Brazil: II--Centro Fluminense Mesoregion.
(74/1021)
During the course of a survey carried out from 2000 to 2001 in the Centro Fluminense Mesoregion of the State of Rio de Janeiro 22 molluscan species were found. Many of the records are new due to the dearth of previous studies. Concerning the snail hosts of Schistosoma mansoni, the most frequently encountered species was Biomphalaria tenagophila, as it occurred in all the surveyed municipalities. There are new records of Biomphalaria straminea and Biomphalaria peregrina which is regarded as a potential intermediate host. Drepanotrema lucidum and Antillorbis nordestensis were found to be shedding echinostome cercariae and strigid cercariae respectively. An account about the current schistosomiasis transmission sites in this Mesoregion is presented as well. (+info)
Differential survival of Lyme borreliosis spirochetes in ticks that feed on birds.
(75/1021)
The abilities of the most common European genospecies of Borrelia burgdorferi sensu lato to survive blood meals taken by ticks feeding on birds were analyzed. A pattern of differential survival of the spirochetes in feeding ticks was observed. The result is consistent with the concept of selective transmission of Lyme borreliosis spirochetes. (+info)
Human onchocerciasis in Brazil: an overview.
(76/1021)
Human onchocerciasis was recently discovered in Brazil among Yanomami Indians living along the border region with Venezuela in the States of Amazonas and Roraima. The article reports on the history of the disease's discovery, its distribution, and incrimination of vector simuliid species. The literature that has been generated on the parasite, its vectors, and control of the disease is critically analyzed as well as the organization of epidemiological surveys and the control program developed by the Brazilian government and an international agency. Suggestions for future work are made. (+info)
Natural host relationships and genetic diversity of Whitewater Arroyo virus in southern Texas.
(77/1021)
The purpose of this study was to refine our knowledge of the natural host relationships of Whitewater Arroyo (WWA) virus. Two hundred eight rodents, representing nine species, were captured in July 1999 on the Chaparral Wildlife Management Area in southern Texas and tested for evidence of arenavirus infection. Antibody to an arenavirus was found in seven (21.9%) of 32 southern plains woodrats (Neotoma micropus) and none of 168 other rodents. Infectious WWA virus was isolated from four antibody-positive southern plains woodrats, one of 25 antibody-negative southern plains woodrats, and none of 176 other rodents. Collectively, the results indicate that the southern plains woodrat is a principal host of WWA virus in southern Texas. Analyses of viral gene sequence data revealed substantial genetic diversity among WWA virus strains isolated from the woodrats, suggesting that multiple variants of the virus can coexist in a single woodrat species in a small geographic area. (+info)
Effects of global climate on infectious disease: the cholera model.
(78/1021)
Recently, the role of the environment and climate in disease dynamics has become a subject of increasing interest to microbiologists, clinicians, epidemiologists, and ecologists. Much of the interest has been stimulated by the growing problems of antibiotic resistance among pathogens, emergence and/or reemergence of infectious diseases worldwide, the potential of bioterrorism, and the debate concerning climate change. Cholera, caused by Vibrio cholerae, lends itself to analyses of the role of climate in infectious disease, coupled to population dynamics of pathogenic microorganisms, for several reasons. First, the disease has a historical context linking it to specific seasons and biogeographical zones. In addition, the population dynamics of V. cholerae in the environment are strongly controlled by environmental factors, such as water temperature, salinity, and the presence of copepods, which are, in turn, controlled by larger-scale climate variability. In this review, the association between plankton and V. cholerae that has been documented over the last 20 years is discussed in support of the hypothesis that cholera shares properties of a vector-borne disease. In addition, a model for environmental transmission of cholera to humans in the context of climate variability is presented. The cholera model provides a template for future research on climate-sensitive diseases, allowing definition of critical parameters and offering a means of developing more sophisticated methods for prediction of disease outbreaks. (+info)
A potential snail host of schistosomiasis in Bolivia: Biomphalaria amazonica Paraense, 1966.
(79/1021)
Biomphalaria amazonica Paraense, 1996 was collected from a permanent pond in the outskirts of the Bolivian city of Santa Cruz. Identification of the collected specimens was made by comparison with the original description of the species and with topotypic material in the collection of Instituto Oswaldo Cruz. Phylogenetic analysis confirmed that these Bolivian specimens belong to B. amazonica. (+info)
Fasciola hepatica and Paramphistomum daubneyi: changes in prevalences of natural infections in cattle and in Lymnaea truncatula from central France over the past 12 years.
(80/1021)
A retrospective study was carried out over a 10- to 12-year period to analyse the changes in prevalences of natural fasciolosis and paramphistomosis among cattle and snails in central France, and to determine the causes which had induced these changes. The prevalences of natural fasciolosis in cattle increased from 1990 to 1993 (13.6% to 25.2%) and diminished afterwards up to 1999 (at 12.6%). Those of natural paramphistomosis showed a progressive increase between 1990 and 1999 (from 5.2 to 44.7%). The prevalences of natural infections and the numbers of free rediae counted in the snails (Lymnaea truncatula) infected with F. hepatica did not show any significant variations over time. By contrast, the prevalences of natural paramphistomosis in snails significantly increased from 1989 to 1996 and remained afterwards in the same range of values (3.7-5.3%), while the number of free rediae significantly increased up to 2000 (from a mean of 6.5 to 13.8 rediae per infected snail, respectively). Three hypotheses may explain the increase of paramphistomosis in cattle and snails: a better quality of diagnosis for the detection of P. daubneyi eggs in veterinary analysis laboratories, the use of specific molecules in the treatment of cattle fasciolosis since 1993, and the lack of an effective treatment up to now against cattle paramphistomosis. Since the objective of most farmers in central France is to obtain the highest antiparasitic efficiency with a single treatment of cattle per year, it is reasonable to assume that the prevalence of bovine paramphistomosis will continue to increase in the future. (+info)