Distribution of the Gulf Coast tick, Amblyomma maculatum Koch was described a century ago as along 160-240 km of coastal South Atlantic regions and the Gulf Coast from South Carolina to Texas. In the 1960’s,inland populations of A. maculatum were discovered in northeastern Oklahoma and southeastern Kansas. These isolated populations exhibit comparatively different seasonal phenologies to coastal populations. Amblyomma maculatum is known to transmit Cowdria ruminantium Cowdry, an African rickettsial pathogen and causal agent of heartwater. This zoonosis is transmitted transstadially, killing 50-90% of infected ruminants. The principal African vector, A. variegatum Fabricius has spread throughout the Caribbean; presently established on 15 islands including St. Croix, a U.S. Territory. Inherently, the risk exists for heartwater to reach the U.S. mainland expatiating this contagion via the life cycle of the A. maculatum, a most competent surrogate vector of this foreign animal disease. Knowledge of allopatric variation among inland and coastal A. maculatum populations and the epidemiology of this disease may hasten establishment of programs to contain a possible epidemic. Nucleotide sequence variation is being examined in the 16S and 12S mitochondrial ribosomal DNA genes to determine genetic relationships among populations of A. maculatum collected from Texas, Oklahoma, and Kansas. Single strand conformation polymorphism analysis (SSCP) of 304 bp of the 16S and12S gene was performed to identify different haplotypes and estimate relative frequencies among 120 ticks. Seven different haplotypes have been identified using the 16S gene. Haplotype diversity was greatest among Kansas populations, where three out of four haplotypes expressed were different. The seven haplotypes are currently being sequenced among 14 individuals. Phylogenetic analysis will be conducted using these sequences.
Species 1: Acari Ixodidae Amblyomma maculatum (Gulf Coast tick)
Keywords: SSCP, heartwater
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA