Beyond toxicity: Systems-level virulence of entomopathogenic fungi in termite social immunity

Termites live in dense colonies where frequent social contact can facilitate pathogen transmission, but coordinated social immunity can also limit disease spread. Entomopathogenic fungi (EPF) are particularly relevant to termite pathology because they infect primarily through the cuticle, using adhesion, enzymatic degradation, penetration, and internal proliferation to overcome host barriers. This review synthesizes current knowledge on EPF virulence in termites and argues that fungal pathogenicity should be understood not only as direct toxicity (lethal effects of pathogen-derived compounds) but also as a coordinated disruption of host physiology, microbiota-associated defenses, and social behavior. At the individual level, EPF infection can affect neural signaling, immune pathways, detoxification systems, oxidative balance, and proteostasis. These disruptions may alter locomotion, sensory perception, chemical communication, and hygienic behavior, thereby influencing colony-level responses such as grooming, avoidance, cannibalism, burial, trophallaxis, and contact-network structure. We also discuss the termite holobiont, emphasizing how gut and nest-associated microbiota contribute to pathogen resistance and how disruption of microbial homeostasis may affect social immunity. Comparative examples from other insects and pathogen systems are included only where they help clarify mechanisms or identify knowledge gaps. Finally, we evaluate how mechanistic insights into EPF-termite interactions may inform future biological control strategies, including improved fungal formulations, RNAi-based approaches, and microbiota-oriented interventions, while distinguishing experimentally supported mechanisms from more speculative applications.