Tritrophic interactions between a fungal pathogen, a spider predator, and the blacklegged tick

Abstract

The blacklegged tick Ixodes scapularis is the primary vector for the bacterium causing Lyme disease in eastern North America and for other medically important pathogens. This species is vulnerable to attack by fungal pathogens and arthropod predators, but the impacts of interactions between biocontrol agents have not been examined. The biocontrol agent Met52®, containing the entomopathogenic fungus Metarhizium brunneum (=M. anisopliae), controls blacklegged ticks with efficacy comparable to chemical acaricides. The brush‐legged wolf spider Schizocosa ocreata is a predator of I. scapularis that reduces their survival under field conditions. We conducted a field microcosm experiment to assess the compatibility of Met52 and S. ocreata as tick biocontrol agents. We compared the fits of alternative models in predicting survival of unfed (flat) and blood‐fed (engorged) nymphs. We found the strongest support for a model that included negative effects of Met52 and S. ocreata on flat nymph survival. We found evidence for interference between biocontrol agents, with Met52 reducing spider survival, but we did not find a significant interaction effect between the two agents on nymph survival. For engorged nymphs, low recovery rates resulted in low statistical power to detect possible effects of biocontrol agents. We found that nymph questing activity was lower when the spider was active above the leaf litter than when the spider was unobserved. This provides the first evidence that predation cues might affect behavior important for tick fitness and pathogen transmission. This study presents field microcosm evidence that the biopesticide Met52 and spider Schizocosa ocreata each reduced survival of blacklegged ticks Ixodes scapularis. Met52 reduced spider survival. Potential interference between Met52 and the spider should be examined at larger scales, where overlap patterns may differ. Ticks were more likely to quest when the spider was inactive, suggesting the ticks changed their behavior to reduce danger.

La ecología de los parásitos zoonóticos en Carnivora

“…Cuando las especies presa también se convierten en reservorios de enfermedades zoonóticas, dicho "control remoto" de las presas por parte de los depredadores, podría influir en la dinámica de la enfermedad (por ejemplo, [50]) y en la transmisión zoonótica de las presas reservorio. Las interacciones no consuntivas similares, podrían influir en el comportamiento de búsqueda de hospederos de los vectores (control remoto de garrapatas vectores por depredadores de arañas, [51]), lo que puede influir en su abundancia o distribución local. En general, estos fenómenos aún no se han investigado ampliamente.…”

The ecology of zoonotic parasites in the Carnivora

“…When prey species are also reservoirs of zoonotic disease, such 'remote control' of prey by predators could influence disease dynamics (e.g., [50]) and zoonotic transmission from reservoir prey. Similar nonconsumptive interactions could influence the host-seeking behavior of vectors (remote control of tick vectors by spider predators, [51]), which may influence their local abundance or distributions. In general, these phenomena have yet to be widely investigated.…”

Parasites of spiders: Their impacts on host behavior and ecology

“…If sublethal infection alters spider activity level, then parasites could alter the magnitude of trophic cascades via non-consumptive effects. In a system where predatory wolf spiders and their prey (black-legged ticks) were housed with a shared araneopathogenic fungus, both spider and tick behavior changed under parasite presence, altering predatorprey dynamics (Fischhoff et al 2018). Spiders may also avoid or alter their foraging behavior in high infection-risk habitats (i.e., landscape of disgust; Weinstein et al 2018).…”