American Foulbrood

American foulbrood (AFB) is a common and serious bacterial disease of honeybee brood, caused by Paenibacillus larvae. P. larvae is a spore-forming bacterium which is found worldwide. Spores are extremely hardly and can survive in dormancy for thirty-five years or more.

At first, AFB is slow to establish and only a few larvae will be affected. In advanced cases the brood pattern will be irregular. However, just because there is no irregular brood pattern doesn't mean that the hive isn't infected with AFB. Infected larvae and pupae, die after their cells have been capped. Adult bees may later partly or totally remove the caps, and as a result the caps may be perforated.

Transmission

AFB is transmitted to larvae from nurse bees or from spores remaining in the bottom of the brood cell. Exchanging combs containing remains of diseased larvae or honey, or both, laden with spores of B. larvae is the quickest way the disease spreads from colony to colony. A colony that is weakened by American foulbrood may be robbed, and the robber bees inadvertently carry honey containing spores of B. larvae to healthy colonies.
AFB is extremely contagious and spreads easily through interchange of infected beekeeping equipment or beekeeper clothes, feeding colonies infected honey or pollen, by honey bees robbing honey from infected hives or from extraction sites, and from drifting honey bees visiting from infected colonies.

Symptoms

  • Dead bees on bottom board
  • Colony appears weak
  • Capped brood is unevenly distributed
  • Irritable behavior
  • Distinct 'foul' odor present
  • Brood die after the cells are capped
  • Discolored brood (turn dark brown)
  • Dark-brown to black colored scales
  • Irregular brood pattern
  • Protruding tongues present
  • Sunken, dark and greasy-looking cappings
  • Perforated cappings

Cause

  • Paenibacillus larvae

Diagnosis

  • Ropiness test
  • Holst milk test
  • Nitrate reduction
  • Catalase production
  • Fluorescent antibody
  • Terramycin

Treatment


  • Lincomycin Hydrochloride : 100 mg per hive weekly for 3 weeks.
  • Tylosin Tartrate : 200 mg/colony in 20 g confectioners/powdered sugar x administered once weekly for 3 weeks. Note- the 200 mg dose is dusted over the top bars of the brood chamber. The drug should be fed early in the spring or fall and consumed by the bees before the main honey flow begins, to avoid contamination of production honey. Complete treatments at least 4 weeks prior to main honey flow. Use medicated sugar mixture immediately.
  • Oxytetracycline : 200 milligrams per colony in feed. Note- Remove at least 6 weeks prior to main honey flow.
  • Sulfa and Ethylene Oxide Gas (ETO)

Prevention

  • Oxytetracycline HCL - In order to try to prevent antibiotic resistance, it is recommended that beekeepers remove all uneaten portions of the medicated extender patties after they have been in the hive for one month.
  • Replace 20% of all brood frames each year so that after a few years, no brood frame is older than five years.
  • Don’t barrel feed or leave used hive equipment exposed to foraging bees.
  • Apply hygienic management practices, including clean clothing, hive tools, and gloves.
  • Work all hives suspected of disease last.
  • Use antibiotics only as recommended. Never use the product after its expiry date, and follow preparation instructions carefully.
  • Become thoroughly familiar with visual detection of brood diseases.
  • Purchase AFB-resistant bees
  • Early detection of the disease is helpful in preventing further spread.
  • Check brood combs at least twice a year for early signs of AFB.
  • Brood combs should be replaced every 3-4 years as old brood combs can act as a reservoir for the bacteria.

Article Reference

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