An isolation protocol is reported that allows for the recovery of parasitic (entomopathogenic) fungi from ticks. This method, modified from plant pathology, involves surface sterilizing, dissection, imbedding body sections into agar, and removing hyphal tips for subculturing. Using this technique, Scopulariopsis brevicaulis Bainier, an imperfect fungus (Deuteromycota), was isolated from internal contents of the American dog tick, Dermacentor variabilis (Say), vector of Rocky Mountain spotted fever, making this the first record of a tick harboring fungi internally. Upon topical application of S. brevicaulis conidia, tick mortality was marked, confirming this fungus' pathogenic nature. Water balance studies suggest that fungal parasitism promotes tick death through dehydration by greatly accelerating water loss rates and inhibiting water vapor uptake. As such, varying levels of S. brevicaulis infection may restrict tick distribution to specific habitats to maintain water balance, and, thus, has epidemiological significance. Deriving growth curves and rates of S. brevicaulis, in vitro, showed preference for mesophilic conditions (24-26oC), and peaked on media (potato dextrose agar, nutrient agar, and blood agar) containing 0.1-1.0M NaCl. Thus, the host's saline-rich bloodmeal likely plays a role in enticing the fungus to enter and persist within the tick. We anticipate that this novel technique will prove to be useful with other arthropod pests for isolating internal (i.e., parasitic) fungi as potential biological control agents.
Species 1: Acari Ixodidae
Keywords: entomopathogenic fungi, ticks
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