The skin crawls, the stomach turns: ectoparasites and pathogens elicit distinct defensive responses in humans

Disgust has long been viewed as a primary motivator of defensive responses to threats posed by both microscopic pathogens and macroscopic ectoparasites. Although disgust can defend effectively against pathogens encountered through ingestion or incidental contact, it offers limited protection against ectoparasites, which actively pursue a host and attach to its surface. Humans might, therefore, possess a distinct ectoparasite defence system—including cutaneous sensory mechanisms and grooming behaviours—functionally suited to guard the body's surface. In two US studies and one in China, participants (N = 1079) viewed a range of ectoparasite- and pathogen-relevant video stimuli and reported their feelings, physiological sensations, and behavioural motivations. Participants reported more surface-guarding responses towards ectoparasite stimuli than towards pathogen stimuli, and more ingestion/contamination-reduction responses towards pathogen stimuli than towards ectoparasite stimuli. Like other species, humans appear to possess evolved psychobehavioural ectoparasite defence mechanisms that are distinct from pathogen defence mechanisms.

The skin crawls, the stomach turns: ectoparasites and pathogens elicit distinct defensive responses in humans

Disgust has long been viewed as a primary motivator of defensive responses to threats posed by both microscopic pathogens and macroscopic ectoparasites. Although disgust can defend effectively against pathogens encountered through ingestion or incidental contact, it offers limited protection against ectoparasites, which actively pursue a host and attach to its surface. Humans might, therefore, possess a distinct ectoparasite defence system—including cutaneous sensory mechanisms and grooming behaviours—functionally suited to guard the body's surface. In two US studies and one in China, participants ( N = 1079) viewed a range of ectoparasite- and pathogen-relevant video stimuli and reported their feelings, physiological sensations, and behavioural motivations. Participants reported more surface-guarding responses towards ectoparasite stimuli than towards pathogen stimuli, and more ingestion/contamination-reduction responses towards pathogen stimuli than towards ectoparasite stimuli. Like other species, humans appear to possess evolved psychobehavioural ectoparasite defence mechanisms that are distinct from pathogen defence mechanisms.

Two sides of the same story in grapevine–pathogen interactions

Proteases are an integral part of plant defence systems, and their role in plant–pathogen interactions is unequivocal. Emerging evidence suggests that different protease families contribute to the establishment not only of hypersensitive response, priming, and signalling, but also of recognition events through complex proteolytic cascades. Moreover, they play a crucial role in pathogen/microbe-associated molecular pattern (PAMP/MAMP)-triggered immunity as well as in effector-triggered immunity. However, despite important advances in our understanding of the role of proteases in plant defence, the contribution of proteases to pathogen defence in grapevine remains poorly understood. In this review, we summarize current knowledge of the main grapevine pathosystems and explore the role of serine, cysteine, and aspartic proteases from both the host and pathogen point of views.

Pathogen defence is a potential driver of social evolution in ambrosia beetles

Social immunity—the collective behavioural defences against pathogens—is considered a crucial evolutionary force for the maintenance of insect societies. It has been described and investigated primarily in eusocial insects, but its role in the evolutionary trajectory from parental care to eusociality is little understood. Here, we report on the existence, plasticity, effectiveness and consequences of social pathogen defence in experimental nests of cooperatively breeding ambrosia beetles. After an Aspergillus spore buffer solution or a control buffer solution had been injected in laboratory nests, totipotent adult female workers increased their activity and hygienic behaviours like allogrooming and cannibalism. Such social immune responses had not been described for a non-eusocial, cooperatively breeding insect before. Removal of beetles from Aspergillus -treated nests in a paired experimental design revealed that the hygienic behaviours of beetles significantly reduced pathogen prevalence in the nest. Furthermore, in response to pathogen injections, female helpers delayed dispersal and thus prolonged their cooperative phase within their mother's nest. Our findings of appropriate social responses to an experimental immune challenge in a cooperatively breeding beetle corroborate the view that social immunity is not an exclusive attribute of eusocial insects, but rather a concomitant and presumably important feature in the evolutionary transitions towards complex social organization.