Fusarium

Fusarium is a group of fungal species (Fusarium spp.) that can infect both plants and human beings. Two species of fusarium known as Fusarium graminearum (F. graminearum) and F. oxysporum were listed in the top ten for a list of molecular plant pathogens based on both scientific and economic importance. Their effects are almost worldwide as Fusarium infections of plants occur in almost all climates. They can infect a wide range of plants, as the American Phytological Society reports that 83/108 plant species have their production affected by Fusarium.

The genus Fusarium

Fusarium spp. used to have two different names based on what reproductive stage they were in. However, this naming system was removed, so now most species only have their Fusarium name. There are more than 70 defined species of Fusarium. Fusarium spp. can be identified in their spore form under the microscope by how they group up to form banana-shaped clusters.

Fusarium disease in plants

The disease caused by fusarium in the plant are dependent on where the infection is. For example, there are head, grain, and seed blights in cereal crops. Different types of cereal crops are susceptible to specific species. For example, F. graminearum targets wheat crops. Infection of the roots can cause vascular wilt, which is where movement of water to parts of the plant is blocked, causing wilting. For trees, canker disease causes lesions on branches. One of the most devastating diseases is fusarium head blight (FHB). FHB is also known as scab

The effect of Fusarium in agriculture

Fusarium has many negative impacts on crop production. It decreases global crop yield every year by up to 50%. This can be due to Fusarium killing the plant through something like stem rot causing the plant to collapse. Or, through stunting the growth of the plant. This is because Fusarium produce mycotoxins. One group of mycotoxin is called fumonisin. Fumonisin has the ability to inhibit seedling growth and cause cell death. Another problem is the contamination of the crop with mycotoxin.

Fusarium infections in plants have no cure, making them devastating for crops. In fact, using fungicides could actually cause Fusarium to produce more mycotoxin. Mycotoxins are problematic because they can get into our food and damage our health.

Mycotoxin

The level of mycotoxin allowed in our food is kept below one part per million (ppm) in United States of America, or below 0.75 ppm in the European Union. However, there is still a health concern of long-term exposure to small amounts of the mycotoxin.

The mycotoxin is essential for spread of Fusarium because inhibiting mycotoxin production makes Fusarium unable to spread. However, mycotoxin is not essential for the growth of Fusarium. Mycotoxins can be grouped based on their structure. The type of mycotoxin produced is dependent on the species, but a single species can produce several types of mycotoxin. Some well-known groups include trichothecenes, fumonisin, giberellic acid, and zearalenone.

Mycotoxin group and their effects

Mycotoxin group	Effect in humans	Effect in plants
Tricothecenes	Stops production of protein Cell death Interferes with development of nervous system in foetus leading to a condition known as spina bifida	Stops production of protein Cell death Impairment of seed germination Impairment of seedling growth Impairment of root growth
Fumonisins	Stops production of fat known as ceramide Cell death	Stops production of fat known as ceramide Cell death Impairment of seedling growth
Zearalenone	Acts like oestrogen, causing hormonal issues	None
Gibberrelic acid	None	Promotes stem growth Impairment of plant defence response

Fusarium disease in humans

Fusarium spp. can live on human skin, mucosa and gut. In a healthy person, the Fusarium that lives on us is harmless. However, there is a rare chance of infection, but this usually happens to people with weakened immune systems. Infections can be local, only affecting a certain body part. For example, Fusarium can grow in contact lens solution, and if it enters the eye, it can cause inflammation of the cornea or even ulceration. However, if the fusarium fungus gets into the bloodstream, it becomes a systemic infection known as system fusariosis. Only a few strains of Fusarium can grow at body temperature (37°C). Systemic fusariosis has a 50-80% mortality rate. This is because there is no treatment or cure currently available. If infection spreads to the lungs, it can cause pneumonia.

Diagnosis of Fusarium infection

An infection of the skin can be diagnosed by a visual inspection. To test for an eye infection, a sample must be taken and cultured. Similarly, for a systemic infection, a culture is taken from the blood.

Treatment of systemic fusariosis

Some antifungals have been successfully used to treat systemic fusariosis such as amphotericin B and voriconazole. However, the lack of large-scale clinical studies means there is currently no approved treatment for Fusarium infections. Since immunocompromised patients are most at risk, they can be put into isolation to reduce the chance of being exposed to Fusarium. However, since Fusarium spp. live naturally in our gut, these fungi can start an infection from within. Therefore, there is no way to reliably prevent or cure Fusarium infections.