Tuesday, 1 April 2008

Toxic Honey

Last week there was a bit of a kerfuffle about the fact that people were getting very seriously ill after eating honeycomb honey. Seventeen cases of tutin poisoning have already been confirmed after the victims ate comb honey bought on the Coromandel from a small boutique beekeeper.

Until this outbreak the official record says that a number of people have been killed, incapacitated and hospitalised over the years from eating toxic honey. The last recorded case from commercial honey was in 1974 involving 13 patients. There have been 9 cases since 1974 with the last known poisoning occurring in 1991 in the Eastern Bay of Plenty area. Two poisonings have been caused by comb honey produced by hobby beekeepers in the Marlborough Sounds in 1982 and 1983 and the highest levels of tutin ever measured in honey were produced in this area.

Toxic honey is produced as a result of bees feeding on tutu (Coriaria arborea) bushes. Tutu is a widely distributed native species found throughout New Zealand, particularly along stream banks and in regenerating native bush. The poison comes from the native tutu bush but Toxic honey is not produced by bees visiting the flowers of tutu to gather nectar or pollen, but rather when bees gather honeydew produced by the sap sucking vine hopper insect (Scolypopa sp) feeding on tutu plants.

The honeydew (a sweet exudate) produced from the tutu plant contains tutin, a member of the picrotoxin group. The toxin has no effect on bees and honeydew honey is chemically very similar to floral honey and cannot be distinguished by taste, sight or smell from other non-toxic honeys. The toxin cannot be degraded by any heating or processing of honey. The toxins are believed to be very stable, and poisoning cases have resulted from people eating honey that was several years old.

Both comb honey and extracted honey can be poisonous. Comb honey poses a greater risk because it is eaten directly off the comb, increasing the chance of consuming honey with a high concentration of tutin. Extracted honey is often bulked or blended with other honey thereby reducing the concentration of toxin.

While tutin, and its derivative, hyenanchin are extremely toxic to humans, only a few areas in New Zealand regularly produce toxic honey. These areas include the Coromandel Peninsula and Eastern Bay of Plenty and the Marlborough Sounds. To produce toxic honey, all of the following conditions are required:

• concentrations of numerous tutu bushes

• high numbers of vine hoppers

• hot dry weather to allow the honeydew to build up on the tutu (rain can wash it off)

• an absence of more attractive food sources for bees, usually caused by drought

• presence of honey bees (Apis mellifera) being managed for honey production.

1 comment:

  1. That is tutu silly a story for anyone to swallow. It is 1 April after all. I suppose if I poisoned someone using that honey, I would have a good pliƩ in mitigation.