Auto-dissemination of commercially available fungal pathogens for management of the brown dog tick, Rhipicephalus sanguineus

Authors: WEEKS, EMMA - University Of Florida; Allan, Sandra - Sandy; GEZAN, S - University Of Florida; KAUFMAN, P - University Of Florida

Submitted to: Medical and Veterinary Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2019
Publication Date: 12/26/2019
Citation: Weeks, E.N., Allan, S.A., Gezan, S.A., Kaufman, P.E. 2019. Auto-dissemination of commercially available fungal pathogens for management of the brown dog tick, Rhipicephalus sanguineus. Medical and Veterinary Entomology. 34(2):184-191. https://doi.org/10.1111/mve.12426.
DOI: https://doi.org/10.1111/mve.12426

Interpretive Summary: The brown dog tick is a pest of canines throughout the world and generally found in the vicinity of humans in homes and dog kennels. Pathogens vectored by these ticks can threaten human as well as canine health. With increased levels of insecticide resistance discovered in the ticks, higher levels of pesticides and use of harsher active ingredients are required to reduce tick populations in homes. However these pesticides are a concern for human health. A researcher at USDA, ARS Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, and researchers at the University of Florida examined the potential for use of fungi that naturally kill ticks as an environmentally safe control approach for these ticks. Of the two pathogenic fungi tested, one produced a faster and higher mortality rate. Results from this study provide the basis for further development of this non-pesticide approach to control of these ticks.

Technical Abstract: Rhipicephalus sanguineus is a pest of canines throughout its worldwide range and is frequently found in indoor settings in homes and dog kennels. It transmits multiple canine pathogens as well as those causing Mediterranean and Rocky Mountain spotted fevers in humans. Management of this tick species is complicated by the presence of high levels of resistance to commonly utilized acaricides. The use of fungal formulations could provide a valuable alternative tool for an integrated pest management program and is especially relevant in an indoor setting where detrimental environmental effects on fungal spores are less of a concern. Efficacy of two commercially available fungal formulations, one containing Metarhizium anisopliae and the other Beauveria bassiana were compared for time to death and sporulation in nymphal ticks exposed for 60 minutes in treated filter paper packets. Ticks treated with B. bassiana died faster and sporulated more than those treated with M. anisopliae. To determine if those sporulating ticks could disseminate fungus to their conspecifics, ticks were marked with paint and treated with fungus in packets before being placed with unmarked, untreated ticks in microcentrifuge tubes. Fungus was successfully transmitted from treated to untreated ticks. Mortality of ticks exposed to B. bassiana-exposed conspecifics occurred sooner than those exposed to M. anisopliae-exposed conspecifics, indicating faster dissemination in the former. Therefore, although both formulations resulted in decreased longevity of ticks compared to the controls, the B. bassiana formulation holds the most promise for direct application or indirect application through auto-dissemination for improved brown dog tick management.