Bacillus larvae

Definition

The former name of a Gram-positive, spore-forming bacterium now classified as Paenibacillus larvae, the causative agent of American foulbrood, a highly contagious and fatal disease of honey bee (Apis mellifera) larvae. Originally described by White in 1906 as Bacillus larvae, the species was reclassified to the genus Paenibacillus in 1994 based on 16S rRNA phylogenetic analysis. The bacterium produces durable endospores capable of persisting in hive materials and the environment for decades, making eradication difficult and rendering American foulbrood a notifiable disease in many jurisdictions.

Etymology

From Latin Bacillus (small rod) + larvae (of larvae), referring to the rod-shaped cells and their pathogenic effect on insect larvae.

Example

Beekeepers detecting Bacillus larvae (now Paenibacillus larvae) in brood samples must destroy infected colonies by burning to prevent spore dispersal, as antibiotic treatment only suppresses visible disease without eliminating the long-lived spores.

Synonyms

• Paenibacillus larvae

Related Terms

• American foulbrood
• Paenibacillus
• honey bee disease
• endospore
• melissopalynology
• apiary sanitation

Usage Notes

The name Bacillus larvae persists in older literature and regulatory documents but is taxonomically obsolete; current scientific and veterinary usage employs Paenibacillus larvae. The synonymy is unambiguous—no other bacterial species shares this former designation. Contrast with Melissococcus plutonius, the causative agent of European foulbrood. Spore viability of 35+ years distinguishes this pathogen from most other honey bee diseases and necessitates stringent biosecurity protocols.