Spatially limited pathogen pollution in an invasive tick and host system

TL;DR

This study shows that invasive cane toads in Florida brought ticks and pathogens, but the ticks didn't spread far from the original release sites.

Contribution

The study provides new evidence of spatially limited pathogen dispersal in an invasive tick-host system.

Findings

Tick infestations were found only in the earliest introduced cane toad populations.

Rickettsia bellii was detected in ticks but not in toad tissues.

The pathogen is likely exotic to Florida, but its origin remains unclear.

Abstract

Expansion of global commerce has facilitated pathogen pollution via the transportation and translocation of invasive species and their associated parasites and pathogens. In Florida, imported cane toads (Rhinella horribilis) were accidentally and intentionally released on multiple occasions. Early populations were found to be infested with the invasive tick, Amblyomma rotundatum, yet it is unknown if these ticks dispersed with their hosts as cane toads spread throughout much of the state. The objectives of our investigation were to (1) determine if there are fewer tick infestations on toads at the periphery than at the core of their distribution as predicted by founder effect events, and (2) identify if ticks were infected with exotic pathogens. We captured toads from 10 populations across Florida. We collected ticks, vent tissue, and tick attachment site tissue from each toad, then tested samples for bacteria in the genus, Rickettsia. We found that 3/10 populations had toads that were infested with A. rotundatum, and infested individuals were in the earliest introduced populations at the core of their distribution. Pathogen testing confirmed Rickettisa bellii in ticks, but not in toad tissues. Haplotype networks could not clearly distinguish if R. bellii in Florida was more closely related to North or South American strains, but host-tick associations suggest that the pathogen was exotic to Florida. Our investigation demonstrated that an invasive species facilitated the introduction of parasites and pathogens into Florida, yet the invasive tick species encountered limitations to dispersal on this host species.

The online version contains supplementary material available at 10.1007/s10530-024-03291-9.

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