# An Enquiry into the Status of American Foulbrood Therapeutics

## TL;DR

This paper reviews alternative treatments for American foulbrood, a deadly bee disease, to reduce antibiotic use and protect pollination services.

## Contribution

The paper provides a comprehensive review of non-antibiotic therapeutic strategies for American foulbrood and evaluates their practical limitations.

## Key findings

- Bacteriophages and immune-priming approaches show the most promise in reducing larval mortality and pathogen load.
- Probiotics and essential oils have inconsistent effectiveness under field conditions.
- Current alternatives are promising but require further research for large-scale application.

## Abstract

Honey bees are vital for pollinating crops that sustain global food production. Yet their populations are declining worldwide due to multiple stressors such as pesticide exposure, climate change, habitat loss, and increasing disease outbreaks. One of the most destructive diseases globally is American foulbrood, caused by a bacterial pathogen that devastates bee colonies and threatens agricultural productivity. This review explores alternative strategies to antibiotics for managing this disease, including bacteriophages, vaccines, probiotics, and plant-derived compounds like essential oils. We summarise how these approaches work, their practical applications, and the challenges that remain. By identifying effective and sustainable solutions, this research aims to support healthier bee populations, reduce reliance on antibiotics, increase the safety of bee products and safeguard pollination services essential for global food security.

Managed colonies of the Western honey bee, Apis mellifera, are essential to global food security by ensuring the pollination of a wide array of crops that are crucial for human consumption. However, substantial declines in managed honey bee populations have been reported worldwide, including in Australia, the United States and Europe. These losses have been attributed to the multifaceted interplay of stressors encompassing agrochemical impact, climate fluctuations, pathogens, suboptimal forage conditions, and habitat reduction. In particular, Paenibacillus larvae, the causative agent of American foulbrood (AFB), is one of the most destructive bacterial pathogens for honey bees due to its high transmissibility, environmental persistence, and capacity to cause complete colony collapse. Recurrent and widespread AFB outbreaks impose significant economic and biosecurity burdens on apiarists, exacerbating declines in pollination services and agricultural productivity. This review synthesises the current landscape of therapeutic strategies targeting AFB, including bacteriophage-based approaches, vaccine development, probiotics, and essential oils, and evaluate their reported field applications, efficacy, and practical limitations. Bacteriophages and immune-priming approaches show the greatest potential to reduce larval mortality and pathogen load, although their application is constrained by formulation stability, delivery challenges, and limited large-scale field validation. Probiotics and essential oils produce highly variable and inconsistent effectiveness under field conditions. Overall, these alternatives currently represent promising complementary tools rather than standalone treatments, underscoring the need for further investigation.