Pathogenicity

Definition

The quantitative capacity of a microorganism, parasite, or infectious agent to cause disease in a susceptible host; distinct from virulence (severity of disease caused) and infectivity (ability to establish infection). In arthropod-borne disease systems, pathogenicity describes the disease-producing potential of a pathogen transmitted by insect or arachnid vectors, such as Plasmodium parasites transmitted by Anopheles mosquitoes or Borrelia burgdorferi by Ixodes ticks.

Etymology

Example

Different strains of the entomopathogenic fungus Beauveria bassiana vary in pathogenicity to Colorado potato beetle larvae, with some isolates causing >90% mortality and others failing to establish lethal infections under identical environmental conditions.

Synonyms

• disease-causing potential

Related Terms

• Virulence
• Infectivity
• toxigenicity
• entomopathogen
• vector competence
• host susceptibility
• dose-response

Usage Notes

Specialists distinguish pathogenicity (qualitative or quantitative ability to cause disease) from virulence (degree of harm, often measured by case-fatality rate or tissue damage). A pathogen may be highly infectious yet weakly pathogenic (e.g., some Wolbachia strains in insects), or poorly infectious but highly pathogenic if infection occurs. The term is sometimes used loosely in place of 'virulence' in older literature; modern usage prefers precision. In medical entomology, pathogenicity assessments guide vector control priorities and predict outbreak severity.