Transovarial transmission

Definition

Vertical transmission of a pathogen from an infected female arthropod to her offspring via the egg, enabling the pathogen to persist across host generations without requiring reinfection from vertebrate or environmental reservoirs. Distinguished from transstadial transmission (passage between life stages of the same individual) and horizontal transmission (between individuals of the same generation).

Etymology

Latin trans- (across, through) + ovum (egg) + -al, referring to passage through the egg

Example

Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, is maintained in tick populations partly through transovarial transmission in Dermacentor and Amblyomma species, allowing the bacterium to survive when vertebrate hosts are scarce.

Synonyms

• transovarian transmission
• Vertical transmission

Related Terms

• Transstadial transmission
• Horizontal transmission
• vector competence
• pathogen reservoir
• venereal transmission
• mechanical transmission

Usage Notes

The term is restricted to arthropod vectors; in broader medical parasitology, 'vertical transmission' is preferred for placental or congenital passage in vertebrates. Not all pathogens capable of infecting vectors undergo transovarial transmission—some, like Rickettsia prowazekii, are lethal to the vector and thus cannot be maintained vertically. Efficiency varies widely: some tick-borne viruses transmit transovarially at rates below 1%, while certain Rickettsia species achieve near 100% transmission.