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Oral susceptibility of South African Culicoides species to live‐attenuated serotype‐specific vaccine strains of African horse sickness virus (AHSV)
Author(s) -
Paweska J. T.,
Prinsloo S.,
Venter G. J.
Publication year - 2003
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 - 10.1111/j.1365-2915.2003.00467.x
Subject(s) - african horse sickness , orbivirus , biology , ceratopogonidae , culicoides , serotype , virology , midge , veterinary medicine , virus , reoviridae , zoology , larva , ecology , medicine , rotavirus
. The oral susceptibility of livestock‐associated South African Culicoides midges (Diptera: Ceratopogonidae) to infection with the tissue culture‐attenuated vaccine strains of African horse sickness virus (AHSV) currently in use is reported. Field‐collected Culicoides were fed on horse blood‐virus mixtures each containing one of the seven serotype‐specific vaccine strains of AHSV, namely serotypes 1, 2, 3, 4, 6, 7 and 8. The mean titres of virus in the bloodmeals for the seven vaccine strains were between 6.8 and 7.6 log 10 TCID50/mL. All females ( n = 3262) that survived 10 days extrinsic incubation (10 dEI) at 23.5°C were individually assayed in microplate BHK‐21 cell cultures. In midges tested immediately after feeding, AHSV was detected in 96.1% individuals; mean virus titre was 2.0 log 10 TCID50/midge. After 10 dEI virus recovery rates varied in Culicoides ( Avaritia ) imicola Kieffer from 1% (AHSV‐2) to 11% (AHSV‐7) and in Culicoides ( A .) bolitinos Meiswinkel from 0% (AHSV‐3) to 14.6% (AHSV‐2). Although our results indicate that two major field vectors C. imicola and C. bolitinos are susceptible to oral infection with vaccine strains of AHSV, the level of viral replication for most of the vaccine strains tested was below the postulated threshold (=2.5 log 10 TCID50/midge) for fully disseminated orbivirus infection. In this study, for the first time AHSV has been recovered after 10 dEI from six non‐ Avaritia livestock‐associated Old World species: C. engubandei de Meillon (AHSV‐4), C. magnus Colaço (AHSV‐3, ‐4), C. zuluensis de Meillon (AHSV‐2, ‐4), C. pycnostictus Ingram & Macfie (AHSV‐2), C. bedfordi Ingram & Macfie (AHSV‐7), and C. dutoiti de Meillon (AHSV‐7). As little is known about the virogenesis of AHSV in the southern African species of Culicoides , the epidemiological significance of our findings in relation to the potential for transmission of current AHSV vaccine strains by Culicoides requires further assessment.