Pathogenesis

Definition

The sequence of cellular, molecular, and physiological events by which a disease or disorder develops, progresses, and is maintained in a host organism. In entomological contexts, pathogenesis encompasses both the mechanisms by which arthropod-vectored pathogens (such as viruses, bacteria, protozoa, or nematodes) establish infection and cause disease in vertebrate or invertebrate hosts, and the processes by which entomopathogenic organisms infect and kill insects or arachnids. The concept includes pathogen entry, replication, tissue tropism, immune evasion, symptomatic expression, and potential transmission back to vectors or new hosts.

Etymology

From Greek pathos (suffering, disease) + genesis (origin, creation)

Example

In malaria, the pathogenesis involves Plasmodium sporozoites injected by Anopheles mosquitoes, followed by liver-stage replication, erythrocytic invasion, and the inflammatory cascade that produces cyclic fevers; understanding this sequence guides both treatment and vector-targeted control strategies.

Related Terms

• Virulence
• vector competence
• entomopathogen
• host-pathogen interaction
• tropism
• infectious disease ecology
• parasite manipulation

Usage Notes

Distinguished from 'etiology,' which identifies the causative agent or origin of disease rather than the mechanistic process of disease development. In veterinary entomology, pathogenesis specifically describes how tick-borne rickettsiae or filarial nematodes produce pathology, whereas in biological control, it refers to how Beauveria bassiana or baculoviruses kill pest insects. The term implies active, dynamic process rather than static pathology; specialists may specify 'arthropod-borne pathogenesis' or 'invertebrate pathogenesis' to narrow scope.