Evaluation of mechanical transmission of HIV by the African soft tick, Ornithodoros moubata.

ABSTRACT

PIP: In an in vitro feeding chamber, African Hut Tampan ticks (Ornithodoros moubata) fed on CEM lymphoblast-rich human blood containing a copious amount of HIV-1 BRU so that the ability of the tick to transmit HIV-1 at 28 and 35 degrees Celsius--ambient temperatures in some parts of Africa--could be examined. The authors also used Aedes albopictus mosquito cells and HIV-1 BRU and HIV-1 NDK to reexamine HIV-1 infectivity in an arthropod cell line at 28 and 35 degrees Celsius. Some adult female ticks ingested as much as 240 mcl of blood, about 70 times the amount ingested by mosquitoes (mean, 106.3 mcl). On the other hand, the fourth and fifth stage nymphs which are the most likely mechanical vectors of HIV consumed a mean of 39 mcl (maximum, 73 mcl). The shortest interval between feeds for nymphs which had not yet molted was 14 days. But other studies suggested that ticks often refeed sooner than 14 days. The ticks regurgitated part of their previous blood meal into the feeding lesion when they later fed on a suckling mouse. Adult ticks harbored viable HIV-1 BRU for as long as 10 days, the longest recorded survival of HIV in an arthropod. Yet, other evidence indicated that HIV survival in O. moubata under natural conditions could actually be 14 days. 4.5% and 1.3% of human CEM lymphoblasts remained viable up to 7 days in the ticks' digestive tract at 28 and 35 degrees Celsius, respectively. Neither HIV-1 BRU nor HIV-1 NDK could replicate in CD4-A. albopictus C6/36 mosquito cells, but the authors did find some evidence of retrotranscription of HIV-1 is probably not possible in vitro, but it could contribute somewhat to HIV-1 transmission in areas of Central Africa where HIV prevalence is high.