🩺 Differential Diagnosis of Bee Brood Diseases

About this simulation

Several brood diseases look superficially alike — sunken, discoloured, dead larvae in a patchy pattern — but each has distinguishing features that a careful inspection can reveal. This lab renders a section of capped and uncapped comb where each disease produces a visually and diagnostically distinct larval condition, so you can practise telling them apart the way a field inspector would.

How each disease presents

• American foulbrood (AFB) — larvae die after capping; cappings turn dark, sunken and perforated. The dead larva collapses into a brown, glue-like mass that is ropey: a matchstick dipped in and withdrawn slowly pulls a mucus-like thread several centimetres long. This positive "ropiness" test is the classic field diagnostic for AFB.
• European foulbrood (EFB) — larvae usually die before capping, twisted off the cell wall and discoloured yellow-brown to grey. There is no ropiness — the remains are watery, not sticky — which is the key test that separates EFB from AFB.
• Chalkbrood — a fungal disease (Ascosphaera apis). Larvae mummify into hard, chalky white or grey-black plugs that rattle loosely in the cell and are often found on the hive floor or entrance, not stuck to the cell wall.
• Sacbrood — a viral disease. The larva fails to moult its final skin, so fluid accumulates between the skin and the body, producing a fluid-filled "sac." Dead larvae often curl upward at the head end into a characteristic gondola or canoe shape.

Controls

• Suspected disease — choose which disease pattern to render across the comb.
• Infection severity — fraction of cells showing disease signs.
• Show capped cells — toggle wax cappings on/off to see the larvae directly.
• Run stretch test — animates a matchstick probe into the nearest diseased cell; only AFB produces a positive (ropey) result.
• Click any dark, diseased cell to inspect it and read its diagnostic notes.

Did you know?

Because AFB spores can remain viable in comb and equipment for over 40 years, a positive ropiness test combined with the sunken, perforated cappings is often enough for an inspector to recommend destroying the hive by fire rather than attempting treatment.