Ergotism, also known as ergot poisoning, is a disease caused by ingestion of ergot alkaloids produced by a group of fungi of the genus
Claviceps and are one of the six major classes of mycotoxins (other classes include aflatoxins, trichothecenes, ochratoxins, fumonsins, and zearalenone) that commonly contaminate cereal grains grown for agricultural use worldwide.
Claviceps fungi are found within ergots, which are hard purplish bodies (sclerotia) which replace sporadic grain kernels within the flowering portions of common crops (wheat, rye, triticale, barley, oats, cultivated and wild oats). Sometimes ergots can be visible to the naked eye, as they are able to grow to almost 10 times the size of the average grain kernel, however they can also be very small and be undetectable to the naked eye. Ergot alkaloids are also produced by endophyte-contaminated grasses (tall fescue, ryegrass, sleepy grass, drunken horse grass, and fine fescues). There are more than 50 different species of ergot alkaloids, with the most dominant being ergotamine, ergocristine, ergosine, ergocornine, and ergocryptine. Concentration and types of ergot alkaloids are extremely variable and greatly differ depending on the geographic region, environmental conditions, and soil type. Rye (
Secale cereal) is the most susceptible to ergot infection, followed by wheat (
Triticum spp.), triticale (
Triticosecale), barley (
Hordeum vulgare), and oats (
Avena sativa).
Ergotism was first documented in the middle ages as a gangrenous outbreak in humans known as “St. Anthony’s fire,” responsible for disfigurement of people and death. Today, its negative impact on humans is no longer a big problem, however it is a concern for livestock. This is because even low concentrations of ergots in livestock feed can adversely affect their health.
Ergot Life Cycle
The ergot life cycle has two stages, the germination and the honeydew stage.
- Germination stage: In the spring, the sclerotia germinate, and produce mushroom-like fruiting bodies that release wind-dispersed ascospores. Ascospores infect host crops (grasses/cereals) during the flowering stage. Contaminated grain heads can contain multiple ergot sclerotia that often require different time periods and temperature ranges to grow. Cool, wet weather condition during the flowering period increase the risk of ergot body formation by prolonging the flowering stage.
- Honeydew stage: This stage involves the florets oozing a sticky exudate that is spread by insects and moist environments. It is after this stage, that the infected ovary hardens and is replaced by an ergot body that either falls before or during harvest, contaminating the field or harvested grain.
Risk factors
- Climate related. Extended periods of increased moisture and cold during flowering promote the development of ergot. The unpredictability and increasing warmth related to climate change has already shown to have detrimental impacts which favor increased ergot production. Incidents of both field and storage mycotoxins have increased over the past 5 years in several areas in Canada, as a result of the environmental conditions related to the climate change.
- Testing methods. Testing for ergots in grains currently is reliant on visual inspection. Counting more than 5 sclerotia/L grain, or having sclerotia weighing 0.1-0.3% of grain DM is considered sufficient contamination of grain that is not to be used for feed intended to feed pregnant or lactating livestock. However, it can still be fed to other livestock, especially chickens and other poultry.
Clinical signs of ergotism can occur in as little as a couple hours to several months after ingestion of ergots. It depends on the concentration and type of ergot alkaloids present, and the amount eaten by the bird. Ergotism can manifest as three general forms---convulsive, gangrenous, or other.
