Beekeeping Diseases
Correct diagnosis

Peter Warhurst, Apiary Section, Warwick

Since European foulbrood disease was positively identified in Queensland apiaries in 1981 and chalkbrood in January 1993, it has become increasingly important for beekeepers, both commercial and hobbyist, to correctly diagnose diseases which affect their bees.

A table of comparative information is presented in this DPI&F note to help identify American foulbrood (Paenibacillus larvae), European foulbrood (Melissococcus pluton), sacbrood and chalkbrood (Ascosphaera apis). All may be encountered in Queensland apiaries. Final diagnosis can be carried out by Biosecurity Sciences Laboratory, Yeerongpilly. This service is free. There is a fee for diagnosis of AFB in honey samples. 

Diagnostic service

By legislation under the Apiaries Act 1982 (Qld), if an infection is suspected in an apiary, the beekeeper must notify the nearest Inspector of Apiaries within 48 hours of becoming aware of the problem. At the same time a 10 cm square piece of comb, or suspect material collected on the end of a matchstick from a cell, containing the suspected diseased larvae should be wrapped in brown paper, placed in a padded postal bag or small cardboard box, or in the case of a matchstick sample placed in a vial or small vessel and posted to:

Specimen Receival Office, Biosecurity Sciences Laboratory DPI&F
Locked Bag 4
MOOROOKA Q 4105

A sample submission form giving the beekeeper's name, address, telephone number and registered brand number should accompany the sample.

European foulbrood

European foulbrood can be controlled with the antibiotic oxytetracycline hydrochloride, (also called oxytetracycline or oxytet). If measured dosages are fed to bee colonies in the prescribed manner, the drug will prove an invaluable tool in apiary management. For more information, refer to DPI&F notes on Beekeeping - Disease: European foulbrood I 

Misuse of antibiotic

If misused, however, particularly in regard to treatment of colonies infected with American foulbrood disease, oxytetracycline may prove disastrous. When hives infected with American foulbrood disease are treated with oxytetracycline, all hives in an apiary may become infected. Field diagnosis is much more difficult under such conditions as the symptoms are masked by the antibiotic's action.

For this reason, it is of the utmost importance that beekeepers learn to distinguish between diseases so that each can be treated correctly and as early as possible.

Information notes describing methods for treatment of European foulbrood, American foulbrood, Sacbrood and Chalkbrood diseases are available from beekeeping officers at Warwick, Gatton, Nambour or via the DPI&F Business Information Centre, phone number 13 25 23.

Oxytetracycline hydrochloride

The following notes on oxytetracycline are particularly important:

• it is available only on prescription and only for the treatment of European foulbrood disease
  
  
• DPI&F veterinarians issue free prescriptions once European foulbrood has been positively identified
  
  
• oxytetracycline is ineffective for the treatment of sacbrood and Kashmir bee virus.

Treating these with antibiotics wastes time and money, and is dangerous to the economic well-being of the beekeeper when applied against American foulbrood.

	Healthy brood	Brood infected with:
		American foulbrood	European foulbrood	Sacbrood	Chalkbrood
Causal organism		Paenibacillus larvae - (a bacterium)	Melissococcus pluton - (a bacterium)	A virus	Ascosphaera apis - (a fungus)
Appearance of brood comb	Brood of similar age in compact areas. Less than 15% of empty cells among the brood.	'Pepper-box' appearance. Sealed brood with dark, moist, sunken or punctured cappings. May be fully or partially uncapped.	'Pepper-box' appearance. Unsealed brood affected. Sealed brood affected in advanced cases with sunken, punctured cappings.	Sealed brood affected. Scattered cells with punctured cappings. May be partially or fully uncapped.	Unsealed and sealed brood affected. Caps may or may not be perforated.
Age of brood	.	Usually older sealed larvae or young pupae.	Usually unsealed larvae 3 to 5 days of age, in 'C' shape.	Usually older, sealed larvae	Sealed or unsealed larvae.
Colour of brood	Larvae pearly white, glistening. Brood has cappings raised, dry, no punctures.	Dull white, becoming light brown, coffee brown, dark brown or black	Dull white, becoming yellow, brown, almost black.	Greyish, becoming brown, black. Head end darker.	White with a tip changing to grey-black.
Consistency of dead brood	.	Soft, becoming sticky. Ropes out to 20 mm before breaking.	Watery to pasty. Recently dead larvae rarely rope. Old infections rope to 10 mm, occasionally to 20 mm, before breaking.	Watery and granular. Tough skin forms a sac. Very old infections rope to about 5 mm before breaking.	Pasty in very early stage otherwise hard.
Appearance of brood	Larvae placed centrally on base of cell.	Larval or pupal remains break down.	Larvae move to abnormal positions on cell base or wall.	Head of larvae curled in a 'canoe' or 'Chinese slipper' shape.	Along the wall to the base of the cell.
Odour of dead brood	.	Slight to pronounced glue-pot	Slight sour to putrid.	Odourless to slightly sour.	Odourless.
Scale characteristics	.	Lies flat on lower side of cell. Fine tongue of pupae adheres to cell roof. Head lies flat.	Usually twisted in cell. Does not adhere tightly to cell wall.	Does not adhere tightly to cell base. Head curled in canoe shape.	Does not adhere to cell base. May rattle when shaken.
Other confusing diseases	.	Sacbrood	.	American foulbrood.	None.

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Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.

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File No: IL0012. March 1998. Replaces: IL98012 . Last Updated: April 2007