Monday, November 15, 2004

Determining whether ticks promote Scopulariopsis brevicaulis-induced skin mycoses by fungal transmission

Joshua B. Benoit, s05.jbenoit@wittenberg.edu1, Jay A. Yoder, jyoder@wittenberg.edu1, Eric J. Rellinger1, Kevin M. Gribbins1, and Sam R. Telford III2. (1) Wittenberg University, Department of Biology, Ward St. at N. Wittenberg Ave, Springfield, OH, (2) Harvard School of Public Health, Department of Immunology and Infectious Diseases, 651 Huntington Ave, Boston, MA

Isolation of the filamentous fungus Scopulariopsis brevicaulis (Sacc.) Bainier (Deuteromycota) from salivary glands, midguts and hemolymph of the American dog tick, Dermacentor variabilis (Say) and the lone star tick, Amblyomma americanum (L.) warranted examining these ticks as possible vectors of fungus via conidia transmitted during feeding. Glass capillaries were placed over the mouthparts and ticks treated with pilocarpine to induce collection of saliva, which was then analyzed by fungal culture and by light microscopy. Despite a heavy S. brevicaulis burden (greater than 95% ticks were infected) only 0-4% saliva collected from larvae, nymphs and adults tested positive for fungus in D. variabilis and only 0-2% tested positive in A. americanum, thus ruling out stage-specific possibilities for transmission by these species. There was no pronounced observation of conidia in tissue biopsies of feeding sites from an immunologically naive rabbit Oryctolagus cuniculus (L.) where S. brevicaulis-positive adult ticks had attached, averaging a low 0-3% occurrence that compared favorably to skin where ticks had not fed, but not to skin where pure S. brevicaulis had been injected subcutaneously (100% prevalence). Lack of conidia transfer to hosts is further evidenced by ticks remaining highly (over 90%) infective after drop-off at the completion of feeding, and no detectable trace of S. brevicaulis in fungal cultures of the host rabbit blood. Transmission of S. brevicaulis to hosts apparently does not take place, arguing against ticks serving as a source of inoculum for infections by this fungus.

Species 1: Acari Ixodidae Dermacenter variabilis (American dog tick)
Species 2: Acari Ixodidae Amblyomma americanum (lone star tick)
Species 3: Deuteromycota Scopulariopsis brevicaulis
Keywords: Fungus