The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Patricia A. Nuttall - One of the best experts on this subject based on the ideXlab platform.
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Tick-Borne Encephalitis Virus Transmission between Ticks Cofeeding on Specific Immune Natural Rodent Hosts☆
Virology, 1997Co-Authors: Milan Labuda, Eva Zuffova, Kozuch O, Elena Eleckova, Rosie S. Hails, Patricia A. NuttallAbstract:To determine whether the portion of a vertebrate host population having specific immunity to tick-borne encephalitis (TBE) Virus can participate in the TBE Virus Transmission cycle, natural hosts immunized against TBE Virus were challenged with infected and uninfected ticks. Yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) were either immunized with TBE Virus by subcutaneous inoculation of the Virus, or they were exposed to Virus-infected Ixodes ricinus ticks. One month later, when serum neutralizing antibody was detectable, the animals were infested with infected (donor) adult female ticks and uninfected (recipient) nymphal ticks; recipients were allowed to feed either in close contact (chamber 1) or physically separated (chamber 2) from the infected donor ticks. Following challenge with infected (and uninfected) ticks, viremia developed in all the control, nonimmune animals, whereas viremia was undetectable in all those animals naturally immunized by previous exposure to infected ticks. Despite the presence of neutralizing antibodies in all the immunized animals, 89% (24/ 27) immune animals supported Virus Transmission between infected and uninfected cofeeding ticks. Most Transmission was localized, occurring within chamber 1; disseminated Transmission from chamber 1 to chamber 2 was reduced. Immunization by tick bite was more effective than immunization by syringe inoculation in blocking cofeeding Virus Transmission. Nevertheless 76% (9/12) animals with "natural" immunity still supported Transmission. The results demonstrate that natural hosts having neutralizing antibodies to TBE Virus (and no detectable viremia) can still support Virus Transmission between infected and uninfected ticks feeding closely together on the same animal. These observations have important epidemiological implications relating to the survival of TBE Virus in Nature.
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Importance of Localized Skin Infection in Tick-Borne Encephalitis Virus Transmission
Virology, 1996Co-Authors: Milan Labuda, Jonathan M. Austyn, Eva Zuffova, Kozuch O, N. Fuchsberger, Jan Lysy, Patricia A. NuttallAbstract:Abstract ArboViruses are transmitted to vertebrates by the ”bite“ of infected arthropods. Events at the site of Virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) Virus Transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice ( Apodemus flavicollis ) and bank voles ( Clethrionomys glareolus ). Virus Transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, Virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; Virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels ≥2.0 log 10 ic mouse LD 50 /0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious Virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE Virus Transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for Transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne Virus Transmission.
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Enhancement of tick-borne encephalitis Virus Transmission by tick salivary gland extracts.
Medical and veterinary entomology, 1993Co-Authors: Milan Labuda, Linda D. Jones, Trevor Williams, Patricia A. NuttallAbstract:To investigate the Tole of ticks in TBE Virus Transmission, salivary gland extract (SGE) was derived from partially red female Ixodes ricinus, Dermacentor reticulatus and Rhipicephalus appendiculatus ticks. Guinea-pigs were infested with uninfected R.appendiculatus nymphs and inoculated with a mixture of TBE Virus and SGE or with Virus alone. The number of ticks which on average acquired Virus from feeding on animals inoculated with TBE Virus and SGE from partially red ticks was 4-fold greater iban the number that became infected by feeding on animals inoculated with Virus alone or Virus plus SGE from unfed I.ricinus. Viraemia was detected in 67% of guinea-pigs inocu- lated with Virus plus SGE compared to 30% of guinea-pigs inoculated with Virus alone. Virus titres in the blood were similar for both groups of animals (range 2,,0- 2.8log10 plaque-forrning units (PFU)/ml of blood); however, the number of ticks that became infected was significantly higher on animals inoculated with Virus plus SGE from partially red ticks. No significant difference was observed with respect to the tick species used to derive SGE. The results indicate that TBE Virus Transmission is enhanced by factor(s) associated with the salivary glands of feeding ticks, and that these factor(s) may facilitate efficient trans- mission of TBE Virus between infected and uninfected ticks even when they feed on hosts that have no detectable viraemia. ,,/
Milan Labuda - One of the best experts on this subject based on the ideXlab platform.
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Tick-Borne Encephalitis Virus Transmission between Ticks Cofeeding on Specific Immune Natural Rodent Hosts☆
Virology, 1997Co-Authors: Milan Labuda, Eva Zuffova, Kozuch O, Elena Eleckova, Rosie S. Hails, Patricia A. NuttallAbstract:To determine whether the portion of a vertebrate host population having specific immunity to tick-borne encephalitis (TBE) Virus can participate in the TBE Virus Transmission cycle, natural hosts immunized against TBE Virus were challenged with infected and uninfected ticks. Yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) were either immunized with TBE Virus by subcutaneous inoculation of the Virus, or they were exposed to Virus-infected Ixodes ricinus ticks. One month later, when serum neutralizing antibody was detectable, the animals were infested with infected (donor) adult female ticks and uninfected (recipient) nymphal ticks; recipients were allowed to feed either in close contact (chamber 1) or physically separated (chamber 2) from the infected donor ticks. Following challenge with infected (and uninfected) ticks, viremia developed in all the control, nonimmune animals, whereas viremia was undetectable in all those animals naturally immunized by previous exposure to infected ticks. Despite the presence of neutralizing antibodies in all the immunized animals, 89% (24/ 27) immune animals supported Virus Transmission between infected and uninfected cofeeding ticks. Most Transmission was localized, occurring within chamber 1; disseminated Transmission from chamber 1 to chamber 2 was reduced. Immunization by tick bite was more effective than immunization by syringe inoculation in blocking cofeeding Virus Transmission. Nevertheless 76% (9/12) animals with "natural" immunity still supported Transmission. The results demonstrate that natural hosts having neutralizing antibodies to TBE Virus (and no detectable viremia) can still support Virus Transmission between infected and uninfected ticks feeding closely together on the same animal. These observations have important epidemiological implications relating to the survival of TBE Virus in Nature.
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Importance of Localized Skin Infection in Tick-Borne Encephalitis Virus Transmission
Virology, 1996Co-Authors: Milan Labuda, Jonathan M. Austyn, Eva Zuffova, Kozuch O, N. Fuchsberger, Jan Lysy, Patricia A. NuttallAbstract:Abstract ArboViruses are transmitted to vertebrates by the ”bite“ of infected arthropods. Events at the site of Virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) Virus Transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice ( Apodemus flavicollis ) and bank voles ( Clethrionomys glareolus ). Virus Transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, Virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; Virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels ≥2.0 log 10 ic mouse LD 50 /0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious Virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE Virus Transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for Transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne Virus Transmission.
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Enhancement of tick-borne encephalitis Virus Transmission by tick salivary gland extracts.
Medical and veterinary entomology, 1993Co-Authors: Milan Labuda, Linda D. Jones, Trevor Williams, Patricia A. NuttallAbstract:To investigate the Tole of ticks in TBE Virus Transmission, salivary gland extract (SGE) was derived from partially red female Ixodes ricinus, Dermacentor reticulatus and Rhipicephalus appendiculatus ticks. Guinea-pigs were infested with uninfected R.appendiculatus nymphs and inoculated with a mixture of TBE Virus and SGE or with Virus alone. The number of ticks which on average acquired Virus from feeding on animals inoculated with TBE Virus and SGE from partially red ticks was 4-fold greater iban the number that became infected by feeding on animals inoculated with Virus alone or Virus plus SGE from unfed I.ricinus. Viraemia was detected in 67% of guinea-pigs inocu- lated with Virus plus SGE compared to 30% of guinea-pigs inoculated with Virus alone. Virus titres in the blood were similar for both groups of animals (range 2,,0- 2.8log10 plaque-forrning units (PFU)/ml of blood); however, the number of ticks that became infected was significantly higher on animals inoculated with Virus plus SGE from partially red ticks. No significant difference was observed with respect to the tick species used to derive SGE. The results indicate that TBE Virus Transmission is enhanced by factor(s) associated with the salivary glands of feeding ticks, and that these factor(s) may facilitate efficient trans- mission of TBE Virus between infected and uninfected ticks even when they feed on hosts that have no detectable viraemia. ,,/
Eva Zuffova - One of the best experts on this subject based on the ideXlab platform.
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Tick-Borne Encephalitis Virus Transmission between Ticks Cofeeding on Specific Immune Natural Rodent Hosts☆
Virology, 1997Co-Authors: Milan Labuda, Eva Zuffova, Kozuch O, Elena Eleckova, Rosie S. Hails, Patricia A. NuttallAbstract:To determine whether the portion of a vertebrate host population having specific immunity to tick-borne encephalitis (TBE) Virus can participate in the TBE Virus Transmission cycle, natural hosts immunized against TBE Virus were challenged with infected and uninfected ticks. Yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) were either immunized with TBE Virus by subcutaneous inoculation of the Virus, or they were exposed to Virus-infected Ixodes ricinus ticks. One month later, when serum neutralizing antibody was detectable, the animals were infested with infected (donor) adult female ticks and uninfected (recipient) nymphal ticks; recipients were allowed to feed either in close contact (chamber 1) or physically separated (chamber 2) from the infected donor ticks. Following challenge with infected (and uninfected) ticks, viremia developed in all the control, nonimmune animals, whereas viremia was undetectable in all those animals naturally immunized by previous exposure to infected ticks. Despite the presence of neutralizing antibodies in all the immunized animals, 89% (24/ 27) immune animals supported Virus Transmission between infected and uninfected cofeeding ticks. Most Transmission was localized, occurring within chamber 1; disseminated Transmission from chamber 1 to chamber 2 was reduced. Immunization by tick bite was more effective than immunization by syringe inoculation in blocking cofeeding Virus Transmission. Nevertheless 76% (9/12) animals with "natural" immunity still supported Transmission. The results demonstrate that natural hosts having neutralizing antibodies to TBE Virus (and no detectable viremia) can still support Virus Transmission between infected and uninfected ticks feeding closely together on the same animal. These observations have important epidemiological implications relating to the survival of TBE Virus in Nature.
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Importance of Localized Skin Infection in Tick-Borne Encephalitis Virus Transmission
Virology, 1996Co-Authors: Milan Labuda, Jonathan M. Austyn, Eva Zuffova, Kozuch O, N. Fuchsberger, Jan Lysy, Patricia A. NuttallAbstract:Abstract ArboViruses are transmitted to vertebrates by the ”bite“ of infected arthropods. Events at the site of Virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) Virus Transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice ( Apodemus flavicollis ) and bank voles ( Clethrionomys glareolus ). Virus Transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, Virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; Virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels ≥2.0 log 10 ic mouse LD 50 /0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious Virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE Virus Transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for Transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne Virus Transmission.
Kozuch O - One of the best experts on this subject based on the ideXlab platform.
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Tick-Borne Encephalitis Virus Transmission between Ticks Cofeeding on Specific Immune Natural Rodent Hosts☆
Virology, 1997Co-Authors: Milan Labuda, Eva Zuffova, Kozuch O, Elena Eleckova, Rosie S. Hails, Patricia A. NuttallAbstract:To determine whether the portion of a vertebrate host population having specific immunity to tick-borne encephalitis (TBE) Virus can participate in the TBE Virus Transmission cycle, natural hosts immunized against TBE Virus were challenged with infected and uninfected ticks. Yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) were either immunized with TBE Virus by subcutaneous inoculation of the Virus, or they were exposed to Virus-infected Ixodes ricinus ticks. One month later, when serum neutralizing antibody was detectable, the animals were infested with infected (donor) adult female ticks and uninfected (recipient) nymphal ticks; recipients were allowed to feed either in close contact (chamber 1) or physically separated (chamber 2) from the infected donor ticks. Following challenge with infected (and uninfected) ticks, viremia developed in all the control, nonimmune animals, whereas viremia was undetectable in all those animals naturally immunized by previous exposure to infected ticks. Despite the presence of neutralizing antibodies in all the immunized animals, 89% (24/ 27) immune animals supported Virus Transmission between infected and uninfected cofeeding ticks. Most Transmission was localized, occurring within chamber 1; disseminated Transmission from chamber 1 to chamber 2 was reduced. Immunization by tick bite was more effective than immunization by syringe inoculation in blocking cofeeding Virus Transmission. Nevertheless 76% (9/12) animals with "natural" immunity still supported Transmission. The results demonstrate that natural hosts having neutralizing antibodies to TBE Virus (and no detectable viremia) can still support Virus Transmission between infected and uninfected ticks feeding closely together on the same animal. These observations have important epidemiological implications relating to the survival of TBE Virus in Nature.
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Importance of Localized Skin Infection in Tick-Borne Encephalitis Virus Transmission
Virology, 1996Co-Authors: Milan Labuda, Jonathan M. Austyn, Eva Zuffova, Kozuch O, N. Fuchsberger, Jan Lysy, Patricia A. NuttallAbstract:Abstract ArboViruses are transmitted to vertebrates by the ”bite“ of infected arthropods. Events at the site of Virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) Virus Transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice ( Apodemus flavicollis ) and bank voles ( Clethrionomys glareolus ). Virus Transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, Virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; Virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels ≥2.0 log 10 ic mouse LD 50 /0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious Virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE Virus Transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for Transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne Virus Transmission.
Wenlin Liu - One of the best experts on this subject based on the ideXlab platform.
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Threshold Dynamics in a Periodic Three-Patch Rift Valley Fever Virus Transmission Model
Complexity, 2019Co-Authors: Buyu Wen, Zhidong Teng, Wenlin LiuAbstract:This paper investigates a three-patch Rift Valley fever Virus Transmission model with periodic coefficients. The basic reproduction number is calculated for the model by using the next infection operator method. The threshold conditions on the extinction and permanence in the mean of the disease with probability one. The Rift Valley fever disease will be permanent in the - th patch if and dies out in the - th patch if . The numerical simulations are given to confirm the theoretical results.
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Threshold Dynamics in a Periodic Three-Patch Rift Valley Fever Virus Transmission Model
Hindawi Limited, 2019Co-Authors: Buyu Wen, Zhidong Teng, Wenlin LiuAbstract:This paper investigates a three-patch Rift Valley fever Virus Transmission model with periodic coefficients. The basic reproduction number Ri0i=1,2,3 is calculated for the model by using the next infection operator method. The threshold conditions on the extinction and permanence in the mean of the disease with probability one. The Rift Valley fever disease will be permanent in the j-th j=1,2,3 patch if j≥i,Ri0>1 and dies out in the j-th patch if j
