TRANSMISSION OF CRIMEAN-CONGO HEMORRHAGIC-FEVER VIRUS IN 2 SPECIES OFHYALOMMA TICKS FROM INFECTED ADULTS TO COFEEDING IMMATURE FORMS

Crimean-Congo hemorrhagic fever (CCHF) virus was transmitted from infe cted adult Hyalomma ticks to uninfected larval and nymphal Hyalomma ti cks while cofeeding on a guinea pig host that did not have a detectabl e viremia. When tested after feeding with infected adults, three (0.8% ) of 370 H. truncatum larvae contained detectable CCHF virus (mean vir us titer 10(1.6) plaque-forming units [PFU]/tick). The virus was trans mitted transstadially from infected larvae and was detected in 15 (1.2 %) of 1,253 nymphs and 12 (0.1%) of 2,049 adults. Virus was recovered from 18 (1.9%) of 931 H. impeltatum nymphs, which originated from larv ae that cofed with infected adults. After H. impeltatum nymphs cofed w ith infected adults, CCHF virus was detected in 21 (4.3%) of 449 (mean virus titer 10(1.7) PFU/tick) fed nymphs, but none of 886 adults test ed after molt. Results of this study indicate that a small proportion of either larvae or nymphs may acquire CCHF infection while cofeeding on a host without a detectable viremia.