The Effects of Soil Texture Characteristics on the Distribution of Metarhizium anisopliae and its Impact on Lyme Disease Transmission

Lyme disease, the result of infection with the bacterium Borrelia burgdorferi, is the most common vector-borne illness in the United States. Lyme disease transmission in humans is not fully understood, but the distribution of the black-legged tick, Ixodes scapularis, is a central factor. I. scapularis is the primary vector for B. burgdorferi in the northeastern United States, and the arthropod is susceptible to entomopathogenic fungi, including Metarhizium anisopliae. Entomopathogenic fungi are found in soil and are parasitic to arthropods, often resulting in fatality. Little is known about the natural distribution and habitat preference of entomopathogenic fungi, but their abundance could be affecting populations of I. scapularis in the wild. I studied the natural distribution of the entomopathogenic fungi Metarhizium anisopliae and its relationship to Lyme disease transmission in Dutchess and Columbia counties, NY, by collecting soil samples from 16 distinct locations. I chose locations based on the relative percent composition of sand and clay, two variables that affect the moisture holding capacity of soils. Clay soils in general retain more moisture, and since M. anisopliae abundance has been associated with high moisture content I predicted that the fungi would be more abundant in clay versus sandy soils. I used larval waxworms of the species Galleria mellonella as a bioassay to determine mortality rates in different soils. Results show that high percentages of sand, rather than clay, significantly increased waxworm mortality