Survey for antibodies against arthropod-borne viruses in the sera of indigenous residents of the caprivi strip and bechuanaland protectorate

Sera collected in 1959 from 602 residents of 19 localities in the Caprivi Strip and Bechuanaland Protectorate were tested for HI antibodies against 15 viruses—4 from Group A, 7 from Group B, 1 from Group C, 2 from the Bunyamwera Group, and Rift Valley fever virus. Results of these tests were largely negative for the 5 localities in the Kalahari Desert, but indicated a great deal of virus activity in the Caprivi Strip and the Okavango Basin. Sera positive in the HI test were further tested with the respective viruses by the mouse neutralization test. Selected sera were also tested for neutralizing antibodies against 4 other ungrouped viruses. Neutralization test results gave further evidence of activity of a wide spectrum of viruses, but showed that immunity levels were highest with Sindbis, West Nile, Wesselsbron, Bunyamwera and Germiston viruses. The results of yellow fever neutralization tests with sera collected in the Okavango Basin during 2 previous surveys are reviewed. The present survey offers no conclusive evidence that this virus has been active among the population sampled.