European Foul Brood (EFB)

Full article is at: European foulbrood and its control (nsw.gov.au)

EFB can cause extensive losses in both amateur and commercial apiaries. There is also an article for Victoria at Oxytetracycline to control European foulbrood | Compliance | Honey bees | Livestock and animals | Agriculture Victoria

EFB is highly contagious with all stages of larvae development susceptible to infection. There are a number of symptoms that are similar to AFB, and these two brood diseases can be confused.

Incidences of the disease are strongly correlated with climatic and nutritional stress factors. Cooler wet weather, poor nutrition and moving bees can promote the incidence of this disease.

Figure 1. The bright white larvae are healthy. The larvae that have a yellow colouring are infected with EFB. The uneven aged larvae in the comb also suggests that the colony may be diseased as the worker bees regularly remove diseased larvae. Image courtesy DPI NSW.

Signs of the disease

  • Brood affected with EFB may have a mottled, peppered appearance, with healthy brood cells intermingled with dead or dying ones.
  • Larvae are mostly affected in the unsealed, curled up stage, although in severe cases brood of all ages may be affected.
  • Their colour changes from pearly white to yellow and finally, yellowish brown. After two to four weeks, larvae dry up to form a brown scale which can easily be removed from the cell.
  • In some cases sealed brood is affected and the capped brood takes on a mottled appearance with scattered sunken and perforated cappings.
  • Pupae may have a similar appearance to those affected by American foulbrood.
  • The odour of infected brood varies from odourless to sour or foul, depending on the secondary invading bacteria present.
  • Outer combs of the brood nest may show signs of the disease earlier and may have a heavier infection than inner combs in the same colony.
  • Dead brood probed with a matchstick usually has a watery consistency, although the sealed brown pupae may exhibit a slightly ropy consistency.

Worker bees may remove and discard diseased larvae as they die and thus a colony may show few signs of disease.

Diagnosis

The only accurate diagnostic method is laboratory examination, particularly where the stages resemble signs of AFB. These are FREE.

The alternatives

  • While there may be times when antibiotic treatment is the only answer, the practice is becoming increasingly less attractive because of the possibility of honey contamination and the development of resistant strains of EFB.
  • In some commercial operations antibiotics are not used at all. Consider the following forms of prevention – all factors combined will certainly reduce your dependence on antibiotics.
  • Re queen on a regular basis: A young vigorous queen will always do better than an older queen. Select disease-resistant breeding stock.
  • Maintain hive hygiene: Regular replacement of brood nest combs will help to reduce the concentration of disease-causing organisms in the brood nest. This can be done by placing two or more white combs or foundation in the brood nest each year.
  • Shift bees with care: Shifting bees has long been recognised as stressful to bees. Moving bees at night with an open entrance will minimise stress. Moving bees closed up may lead to excessive heat production and associated stress. Bees are more likely to show signs of EFB soon after being moved.