This brood disease is caused by the non-spore forming bacterium Melissococcus pluton. It affects open brood and is common during spring when brood rearing is at its height. Colonies may be severely weakened. EFB is considered a less serious disease than AFB but high losses have been recorded. Infected larvae appear coiled/ twisted in their cells with a brownish colour and normally die when they are 4-5 days old. Sometimes one can detect a sour odour.
Ugonjwa huu wa kuzaa husababishwa na bakteria isiyounda spora Melissococcus pluton. Inasababisha kuzaliwa kwa watoto waziwazi na ni ya kawaida wakati wa majira ya kuchipua wakati uzazi wa watoto uko kwenye urefu wake. Huenda makoloni yakawa yameharibika sana. Ugonjwa wa FTB unaonekana kuwa mbaya zaidi kuliko ugonjwa wa FTB, lakini kwa sababu ya hatari ya kuambukizwa, ni hatari zaidi. Larvae walioambukizwa huonekana wakiwa wamejipinda au kugeuka katika seli zao na rangi ya kahawia na kwa kawaida hufa wanapokuwa na umri wa siku nne hadi nne. Nyakati nyingine mtu aweza kugundua harufu mbaya.