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Vector competence of selected South African Culicoides species for the Bryanston serotype of equine encephalosis virus
Author(s) -
Venter G. J.,
Groenewald D. M.,
Paweska J. T.,
Venter E. H.,
Howell P. G.
Publication year - 1999
Publication title -
medical and veterinary entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 82
eISSN - 1365-2915
pISSN - 0269-283X
DOI - 10.1046/j.1365-2915.1999.00188.x
Subject(s) - biology , virus , serotype , virology , infectivity , ceratopogonidae , orbivirus , incubation , reoviridae , veterinary medicine , microbiology and biotechnology , zoology , rotavirus , medicine , biochemistry
Summary Equine encephalosis virus (EEV) was recognized and described in the Republic of South Africa in 1967 and subsequent serological studies have shown this orbivirus to be both widespread and prevalent in southern Africa. In the present study it was shown that wild‐caught Culicoides (Avaritia) imicola Kieffer (Diptera: Ceratopogonidae) can become infected with and permit the replication of the Bryanston serotype of EEV following membrane‐feeding on infective blood containing 5.0 log 10 plaque‐forming‐units (PFU)/ml. The mean prevalence of Bryanston virus infection in C. imicola after 10 days extrinsic incubation at 23.5°C was 22.3% (23/103). The mean infectivity of Bryanston virus in the infected C. imicola increased from 1.3 log 10 PFU/midge, in insects assayed immediately after feeding on the blood‐virus mixture, to 2.6 log 10 PFU/midge in insects assayed after incubation. The virus concentration in individual C. imicola infected with the Bryanston serotype of EEV ranged from 0.7 to 3.6 log 10 PFU/midge. Bryanston virus titres higher than 2.5 log 10 TCID 50 , found in individual C. imicola , suggest that this species may be able to transmit this virus to susceptible hosts. Prevalence of virus infection in C. imicola was determined by PFU and microtitration assays on both BHK and Vero cells and confirmation of the Bryanston serotype of EEV was determined by plaque inhibition. No virus replication could be demonstrated in 102 C. nivosus tested after the incubation period, suggesting that not all Culicoides species are equally susceptible to Bryanston virus infection. Other Culicoides species that survived the incubation period and that were negative for the presence of Bryanston virus were C. pycnostictus (42), C. leucostictus (7), C. magnus (2), C. bolitinos (1) and C. bedfordi (1).