# American Foulbrood Recognition and Response


## Key Takeaways

- American Foulbrood (AFB) is caused by the spore-forming bacterium *Paenibacillus larvae*, with only the spore stage being infectious and capable of surviving for over 40 years on equipment and in honey.
- Suspicious clinical signs include sunken, greasy, or perforated brood cappings, a foul, glue-like odour, and ropy larval remains (>1.2 cm) when probed, though laboratory confirmation via culture or PCR is essential.
- Transmission occurs through contaminated beekeeping practices (e.g., moving infected combs, reusing tools), robber bees, and the introduction of infected bees or equipment, necessitating strict movement controls and quarantine of suspected apiaries.
- Regulatory response mandates reporting to authorities, with confirmed cases typically requiring the destruction of infected colonies and equipment by burning, as antibiotics only suppress symptoms and do not eliminate spores.
- Apiary biosecurity is paramount, involving avoiding known AFB outbreaks, not swapping brood combs between apiaries, maintaining separate tools, and feeding only honey from verified AFB-free sources to prevent spore introduction.
- Common mistakes include relying solely on the rope test, attempting to medicate AFB with antibiotics, and reusing contaminated equipment without proper sterilization (e.g., gamma irradiation), all of which prolong disease spread and risk antimicrobial resistance.

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American foulbrood (AFB) is a highly contagious, spore-forming bacterial disease of honey bee larvae caused by *Paenibacillus larvae*. It is notifiable in most jurisdictions and can destroy entire apiaries if not caught early. This guide is for beekeepers, apiary inspectors, and extension personnel who need to recognize suspicious signs, confirm the diagnosis, comply with movement restrictions, and carry out effective containment. It draws on international standards from the [World Organisation for Animal Health (WOAH) Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) and practical guidance from the [USDA Animal and Plant Health Inspection Service (APHIS)](https://www.aphis.usda.gov/animal-health).

## At a Glance

| Observation or Decision | Key Points |
|------------------------|------------|
| **Suspicious signs** | Sunken, greasy, or perforated brood cappings; foul odour; ropy larval remains when probed |
| **Differential diagnosis** | European foulbrood (EFB), chalkbrood, sacbrood, pesticide damage, chilled brood |
| **Field confirmation** | Rope test (positive if larval remains stretch >1 cm) |
| **Laboratory testing** | Culture from comb or honey; PCR and immunoassays available (see [PubMed study on immunoassays](https://pubmed.ncbi.nlm.nih.gov/41559354/)) |
| **Movement control** | Do not move hives, equipment, or bees from suspected apiary; quarantine |
| **Reporting** | Mandatory to state/provincial apiculture authority or USDA APHIS in the U.S. |
| **Equipment disposal** | Burn hive and frames; do not reuse unless sterile (e.g., gamma irradiation) |
| **Spore persistence** | Spores survive decades on equipment, in honey, and on beeswax |

## Understanding the Pathogen and Its Spread

*Paenibacillus larvae* is a Gram-positive, spore-forming bacterium. Only the spore stage is infectious; vegetative cells do not cause disease. Spores are fed to larvae via contaminated brood food, germinate in the larval gut, and multiply, killing the larva after it is sealed in its cell. Spores can remain viable for more than 40 years on equipment and in honey.

Transmission occurs through:
- **[Beekeeping](/knowledge/animal-farming/apiculture/beekeeping-colony-nutrition-seasonal-management-parasite-monitoring-and-honey-harvest) practices**: moving infected combs, reusing contaminated hive tools, feeding spore-laden honey.
- **Robber bees**: infected colonies may be robbed, carrying spores back to healthy hives.
- **Purchased bees or equipment**: secondhand hives, packages, or nucleus colonies brought onto the apiary.

The [FAO animal-production guidance](https://www.fao.org/animal-production/en) emphasises that AFB is a global threat requiring international cooperation, as movement of bees and hive products across borders can spread spores. Routine biosecurity and early detection are the only defences.

## Recognizing Suspicious Signs

Inspecting brood frames carefully , ideally during the [seasonal beehive inspection checklist](/knowledge/animal-farming/apiculture/seasonal-beehive-inspection-checklist) , is the first line of defence. Look for the following signs.

### Visual Signs on Brood Cappings

- **Sunken cappings**: infected sealed brood cells develop concave, greasy-looking cappings that may appear darker than surrounding cells.
- **Perforated cappings**: adult bees chew small irregular holes in cappings to remove dead larvae, leaving a “pepperbox” appearance.
- **Discoloured larvae**: larvae turn from pearly white to brown, then dark coffee-coloured. They lie along the bottom of the cell (not curled like a healthy larva).

### Odour

The classic sign is a putrid, glue-like smell. Not all AFB cases produce a strong odour, but a foul, sour, or “rotten” scent from the hive should trigger suspicion.

### Rope Test (Field Diagnostic)

Insert a small twig or toothpick into a suspect cell, stir the larval remains, and slowly pull upward. In a positive test, the brown, watery mass stretches into a sticky rope at least 1,2 cm long. This test is **highly suggestive** but not definitive , European foulbrood can also produce a weak rope. Always confirm with laboratory testing.

If you observe any of these signs, do **not** move the hive. Quarantine the apiary immediately.

## Differential Diagnosis

Several brood disorders mimic AFB. A correct field differentiation reduces unnecessary destruction and guides proper treatment.

| Condition | Key Features | How to Distinguish from AFB |
|-----------|--------------|-----------------------------|
| **European foulbrood (EFB)** | Larvae die before sealing; twisted position; sour but not putrid odour; no ropy remains | EFB larvae are not sealed; no sunken cappings; rope test usually negative or very short |
| **Chalkbrood** | Hard, white or grey “mummies” in cells or on bottom board | No foul odour; mummies are dry and granular; no ropy test |
| **Sacbrood** | Fluid-filled sac-like larvae; no odour; cappings may be punctured but not sunken | Sacbrood remains are watery but do not rope; colour is pale yellow |
| **Pesticide poisoning** | Dead larvae and adults; often sudden die-off; no odour; no rope | History of pesticide exposure; brood may be at all stages; no bacterial growth on culture |
| **Chilled brood** | Clumped dead larvae in a corner of the frame; no odour | Not contagious; occurs after cold snap; unaffected brood is healthy |

A point-of-care molecular assay that simultaneously detects *P. larvae* (AFB) and *Melissococcus plutonius* (EFB) is now available, as described in a [2025 study in the Journal of Veterinary Diagnostic Investigation](https://pubmed.ncbi.nlm.nih.gov/40905163/). Such tools can aid field diagnoses when confirmatory lab results are delayed.

## Diagnostic Testing and Laboratory Confirmation

Because the rope test is not 100% specific, confirmation should always involve laboratory testing. The following methods are recognised:

- **Microscopic examination**: Not reliable for AFB; spore morphology alone is insufficient.
- **Culture**: Standard method , streak suspect comb or honey onto brain-heart infusion agar. Colonies of *P. larvae* are small, cream-coloured, and catalase-negative. Culture from bulk honey is a sensitive method for detecting low-level contamination in an apiary (see Journal of Apicultural Research, 1991).
- **PCR ([polymerase chain reaction](/knowledge/molecular-biology/polymerase-chain-reaction))**: Highly specific and faster than culture. It can distinguish *P. larvae* from related species. A [2002 study in Applied and Environmental Microbiology](https://doi.org/10.1128/AEM.68.7.3655-3660.2002) demonstrated PCR with restriction fragment analysis for subspecies differentiation.
- **Immunoassays**: Recent work has produced antibody-based tests that can detect and differentiate *P. larvae* directly from field samples ([Science Reports, 2026](https://pubmed.ncbi.nlm.nih.gov/41559354/)). These tests are being validated for point-of-care use.

**Sample collection**: Cut a 5,10 cm section of brood comb containing suspect cells, wrap securely in newspaper, and ship chilled (not frozen) to a diagnostic lab. Alternatively, collect at least 10,15 g of honey from the hive , honey culture is effective for detecting spores even without visible clinical signs (Journal of Apicultural Research, 1991).

## Regulatory Response and Movement Control

AFB is a notifiable disease under the [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/). In the United States, reporting is mandatory to the state apiculturist or USDA APHIS ([USDA APHIS Animal Health](https://www.aphis.usda.gov/animal-health)). In many jurisdictions, any beekeeper who suspects AFB must quarantine the affected apiary and not move hives, bees, or equipment until cleared.

**Movement control**:
- Do **not** move any hive components, live bees, or honey from a suspect apiary.
- Mark the apiary location clearly and limit human access.
- If AFB is confirmed, the regulatory authority will impose movement restrictions and prescribe destruction or treatment.

**Regulatory response** typically includes:
- Destruction of infected colonies by burning (hives, frames, bees) or gamma irradiation of equipment.
- A period of quarantine (often 30,60 days) for the remaining apiary.
- Mandatory follow-up inspections for a set period, often one full beekeeping season.

Beekeepers should register with their state or provincial bee inspection program, as authorities need to trace disease spread. For new beekeepers, the guide on [starting a beekeeping operation](/knowledge/animal-farming/apiculture/starting-a-beekeeping-operation) includes advice on registration and biosecurity planning.

## Equipment and [Apiary Biosecurity](/knowledge/animal-farming/apiculture/beekeeping-facility-biosecurity-design-protocols)

AFB spores adhere to wax, wood, and tools. A single spore can initiate infection. Spores are resistant to most disinfectants and to heat up to 100°C.

### Contaminated Equipment

- **Hive bodies and frames**: Burning is the most reliable method. Do not reuse wood or wax from an AFB-positive hive unless it has been gamma-irradiated (a process that destroys spores at a commercial facility). Chemical fumigants (e.g., ethylene oxide) are sometimes used but require professional application.
- **Hive tools, gloves, smokers**: Dip tools in hot bleach solution (1 part bleach, 9 parts water) for 10 minutes, or flame-sterilize. Do not use plastic gloves , spores adhere to them.
- **Extraction equipment**: If honey from an AFB hive was extracted, the equipment must be dismantled and sterilised. Do not return extracted frames to the apiary.

### Apiary Biosecurity Measures

- Place apiaries away from known AFB outbreaks. The guide on [choosing an apiary site](/knowledge/animal-farming/apiculture/choosing-an-apiary-site) recommends avoiding proximity to commercial beekeepers with uncertain health status.
- Do not swap brood combs between apiaries.
- Maintain separate hive tools for each outyard.
- Restrict visits to other beekeepers’ apiaries; if unavoidable, change clothes and boots.
- Feed only honey from known AFB-free sources. Do not feed honey from unknown origins , it may contain spores.
- Strong colonies with good nutrition are better able to resist infection, but nutrition alone does not prevent AFB. A colony with adequate pollen and nectar stores, as described in [honey bee colony nutrition and supplemental feeding](/knowledge/animal-farming/apiculture/honey-bee-colony-nutrition-and-supplemental-feeding), may express less severe symptoms, but spores will still be present.

## Practical Response Sequence

If you find suspicious signs, follow this sequence:

1. **Stop work**. Close the hive. Do not touch any other hives.
2. **Quarantine** the apiary. Move no bees, hives, or equipment. Notify the property owner if the apiary is on leased land.
3. **Take samples**: a comb section from the suspect frame, and a honey sample (at least 15 g). Label with date, hive ID, apiary location, and your name.
4. **Report** to the appropriate authority (state apiarist, USDA APHIS area office, or local animal health office). In many countries, this is a legal requirement.
5. **Await lab results**. Do not destroy hives until directed by the authority , you may need to preserve evidence for epidemiological tracing.
6. **Act on confirmation**: If positive, follow the regulatory destruction protocol. This usually involves killing the colony (soap solution or petrol (gasoline) poured into the entrance) and burning all hive parts. Verify that bees cannot rob dead colonies , remove to a burn pit immediately.
7. **Record the event** in your apiary diary. Include date, number of hives affected, location, lab report number, and actions taken.
8. **Monitor sentinel hives** in the same apiary for at least 12 months after destruction. Use the [seasonal beehive inspection checklist](/knowledge/animal-farming/apiculture/seasonal-beehive-inspection-checklist) to schedule regular checks.

## Records to Keep

Maintain a simple log for each apiary. Include:
- Hive identification (number, colour code, GPS coordinates)
- Date and findings of each inspection
- Results of any laboratory tests (lab name, date, test method, result)
- History of any treatments, feeding, or new introductions
- Movement records: when bees or equipment entered or left the apiary
- Reporting dates and regulatory contacts

These records help trace the source of infection and demonstrate compliance during regulatory audits.

## Common Mistakes and Welfare Implications

**Common mistakes**:
- Relying only on the rope test without laboratory confirmation.
- Attempting to “medicate” AFB with antibiotics. Antibiotics (oxytetracycline, tylosin) can suppress clinical signs but do not kill spores. This may mask disease and allow spores to spread, leading to antibiotic resistance. Many countries now restrict antibiotic use in honey bees to veterinary prescription only, if allowed at all.
- Reusing equipment from an AFB-positive hive after only scraping or washing. Spores remain viable.
- Ignoring a suspicious sign because the colony appears strong. AFB can kill a colony only after the spore load is high, but early detection saves adjacent hives.
- Feeding honey from an unknown source , this is a common way AFB enters an apiary.

**Animal-welfare implications**: Affected larvae die slowly, and the colony gradually weakens, increasing vulnerability to robbing, starvation, and other diseases. A colony with active AFB is not salvageable; delaying destruction prolongs suffering and risks spread. Prompt, humane destruction (using approved methods that kill bees quickly) is the most ethical course.

## When to Consult a Qualified Adviser

- **Veterinarian**: If you plan to use any antibiotic, you must do so under veterinary prescription and only if legal in your jurisdiction. A veterinarian can also advise on legal withdrawal times for honey and wax. However, for AFB, destruction , not treatment , is the standard of care in most countries.
- **State apiarist or regulatory inspector**: Consult immediately upon suspicion. They will direct testing and destruction protocols.
- **Extension specialist**: For help with biosecurity planning, site selection, and training.
- **Beekeeping association**: To alert local beekeepers and coordinate regional surveillance.

Because AFB spores are extremely persistent, any beekeeper who finds a positive hive should assume the entire apiary is exposed. Always follow the guidance of your local regulatory authority.

## Frequently Asked Questions

**Q: Can I treat AFB with oxytetracycline and keep the colony alive?**  
A: Antibiotics suppress clinical signs but do not eliminate spores. Spores remain in the hive and can cause recurrence later. Many regulatory authorities require destruction of AFB-positive colonies rather than treatment, because antibiotic use can mask disease and contribute to antimicrobial resistance.

**Q: How long do AFB spores survive in the environment?**  
A: Spores can remain viable for 40 years or more on wooden hive parts, tools, and wax. In honey, they survive indefinitely. This is why burning is the recommended disposal method for AFB-contaminated equipment.

**Q: Can my bees pick up AFB from flowers?**  
A: Yes. Spores can be carried on the bodies of foraging bees visiting contaminated flowers. However, the primary source is usually an infected colony nearby. Robber bees also transport spores. The risk from flower contamination is lower than from direct hive contact but cannot be ruled out.

**Q: Do I have to report every case of AFB?**  
A: In most countries, AFB is a notifiable disease. Reporting is a legal requirement. Even if you are not legally compelled, reporting helps authorities track outbreaks and protect other beekeepers. An unreported case can lead to widespread infection.

## Related Clinical & Scientific Guides

* [Waste Management in the Apiary: Culling, Dead Hives, and Debris Disposal](/knowledge/animal-farming/apiculture/waste-management-apiary-culling-dead-hives-debris-disposal)
* [Package Bee Production: Business Planning and Colony Establishment](/knowledge/animal-farming/apiculture/package-bee-production-business-planning-and-colony-establishment)
* [Siting an Apiary: Legal Setbacks, Neighbor Relations, and Flight Paths](/knowledge/animal-farming/apiculture/siting-apiary-legal-setbacks-neighbor-relations-flight-paths)


## References and Further Reading

- [WOAH Terrestrial Animal Health Code , Section on Honey Bee Diseases](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/)
- [USDA APHIS Animal Health , Honey Bee Health](https://www.aphis.usda.gov/animal-health)
- [USDA ARS Honey Bee Health Resources](https://www.ars.usda.gov/oc/br/ccd/index/)
- [FAO Animal Production and Health , Honey Bee Disease Management](https://www.fao.org/animal-production/en)
- [Immunoassays for detection and differentiation of *P. larvae* , Sci Rep 2026](https://pubmed.ncbi.nlm.nih.gov/41559354/)
- [Point-of-care molecular assay for AFB and EFB , J Vet Diagn Invest 2025](https://pubmed.ncbi.nlm.nih.gov/40905163/)
- Culture of *Bacillus larvae* from bulk honey , J Apic Res 1991
- [PCR and restriction analysis of 16S rRNA for *P. larvae* differentiation , Appl Environ Microbiol 2002](https://doi.org/10.1128/AEM.68.7.3655-3660.2002)
- [Tylosin, erythromycin, oxytetracycline for AFB control , J Apic Res 1999](https://doi.org/10.1080/00218839.1999.11101005)

## Related Farming Guides

- [Starting a Beekeeping Operation](/knowledge/animal-farming/apiculture/starting-a-beekeeping-operation)
- [Choosing an Apiary Site](/knowledge/animal-farming/apiculture/choosing-an-apiary-site)
- [Seasonal Beehive Inspection Checklist](/knowledge/animal-farming/apiculture/seasonal-beehive-inspection-checklist)
- [Honey Bee Colony Nutrition and Supplemental Feeding](/knowledge/animal-farming/apiculture/honey-bee-colony-nutrition-and-supplemental-feeding)
- [Varroa Mite Monitoring and Integrated Management](/knowledge/animal-farming/apiculture/varroa-mite-monitoring-and-integrated-management)

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**Educational notice:** This guide supports farm planning and informed discussion. It does not replace veterinary diagnosis or treatment, a species-qualified nutritionist, an agricultural engineer, product-label directions, or local regulatory requirements.