Alternaria - Everything You Should Now About It!

Introduction:

Infections are vast in humans and animals. Although there is a wide range of microorganisms, most infections are commonly caused by either of the three groups of organisms - bacteria, viruses, or fungi. Alternaria is one of the fungal organisms that cause adverse effects in animals, humans, and plants. Though Alternaria is not a frequently mentioned group of fungi, it has been shown to cause a wide range of harmful effects on the sources of the essential part of human life - food. Further is a piece of gathered information on this group of fungi.

What Is Alternaria?

Alternaria is a genus of fungal organisms that heads a group of species. There are almost 300 different species under the Alternaria genus. It includes many pathogenic microorganisms that affect plants, animals, and humans and are widely distributed throughout the living environment. They are responsible for causing adverse plant effects but also act as a common allergen in humans.

Where Are the Alternaria Species Present?

They are widely scattered in the environment. They are present in the soil, water, objects, and daily necessities present indoors, rotten wood, compost (as they act as one of the significant decomposers), plant crops, grains that are widely grown for human consumption, bird nests, and almost in everything that is seen around. They even grow on the skin and mucous membranes, like in the respiratory tract of humans. Also, they grow mainly on food items stored for commercializing and transporting.

Where Is Alternaria Found?

It includes species that are widespread and can be found in:

• Soil: The sources of infection include contaminated soil since the fungi belong to the group of decomposers of organic matter.

• Plants: They are plant pathogens that infect many plants, including vegetables, fruits, flowers, and other plants. This genus is attributed to many plant diseases, including leaf spots, blights, and rots.

• Outdoor Air: Alternaria is a fungus that is present in the outdoor air throughout the year, but its occurrence is highest during late summer and early autumn. They are part of the total fungal spore load in the air that humans can easily inhale.

• Indoor Environments: Alternaria can also live inside structures, especially in humid or water-damaged structures. It can exist in building materials such as wood, dry walls, insulation, dust, textiles, and foods found in homes.

• Human and Animal Environments: Although Alternaria is common outside the home, it can be found where people and animals frequently tread, and it has been known to cause allergies and respiratory problems in vulnerable populations.

How Are the Alternaria Species Transmitted?

Alternaria is an organism transmitted through the air (airborne), water, and by contact with objects infected with fungi.

What Are the Adverse Effects Caused by Alternaria?

• They affect the quality and quantity of the foods produced and tend to decrease the nutritional content of the food.

• They interrupt the growth of the crops and hamper their production; hence, those cultivating them, mainly the farmers and the food manufacturers, face a huge downfall due to these fungi, which decreases the quality of their life.

• Though the adverse effects of Alternaria have not been widely studied, they are said to cause serious adverse effects in immunocompromised patients, such as those affected by AIDS (acquired immunodeficiency syndrome) and other diseases that weaken the immune system.

• Studies also show that they are responsible for skin infections, allergic reactions, upper respiratory infections, sinusitis, and keratomycosis (infection of the eye's cornea, mostly in farmers who experienced cornea trauma from crops contaminated by this fungus) in humans.

What Are the Common Crops That Are Affected by Alternaria?

Alternaria has shown around 20 percent of crop destruction. It is commonly found in fruits, vegetables, seeds, and grains.

• Fruits: Citrus fruits, apples, cranberries, raspberries, melons, prune nectar, Japanese pears, etc.

• Vegetables: Mainly tomatoes, carrots, peppers, broccoli, and cauliflower.

• Seeds: Sunflower seeds, flax seeds, Linseeds, etc.

• Grains: Alternaria affects almost all grains; the most common are wheat, barley, oats, and lentils.

What Are the Properties of Alternaria Species?

Although not many studies have been performed to rule out the properties of Alternaria species, the following are a few properties that have been observed through the few studies performed;

• The isolated Alternaria species have shown a different variety of colors. Most common are the green hues such as light green, light gray, black green, olive brown-green, and various others.

• High moisture-containing foods favor Alternaria and hence are seen in preharvest and post-harvest crops with higher amounts of moisture.

• The optimum temperature required for the growth of the Alternaria genus ranges from 22℃ to 30℃.

• They can grow, multiply, and cause adverse effects even in unfavorable temperatures. Hence, they are responsible for food spoilage even if refrigerated for transport and commercial purposes.

• The common toxins the Alternaria genus produces are phytotoxins (toxins that affect plants and crops and cause destruction) and mycotoxins (present in food items). But, they can produce a wide range of toxins, almost 70 types of toxins.

• Although many studies are not reported, the Alternaria genus has shown adverse effects, including cytotoxicity (ability to cause cell death), phytotoxicity (in plants, they prevent seed germination and delay plant growth), teratogenicity (ability to damage the developing baby), and carcinogenicity (ability to cause cancer or increase the cancer risk).

What Is the Incubation Period for Alternaria Species?

The incubation period of Alternaria species ranges from one to 11 days maximum. The incubation period is also affected by how wet the incubation site is. If the wetness is stable and increases, the incubation period decreases.

How Are Infections Caused Due to Alternaria Treated?

The treatment for infections caused by Alternaria species varies depending upon the type of infection caused. The treatment is customized to the condition experienced by the individual. Unless immunocompromised, the disease does not usually get serious.

How to Prevent an Alternaria Infection?

• Using fungicides preharvest has shown no effects on killing the Alternaria species. At the same time, their use post-harvest has shown half the reduction in adverse effects.

• Eliminate the source of infection; if a particular crop is a source, deeply burying it or burning it eliminates the chance of further infection.

• Avoid long-time exposure of the crops to water.

• Delay the harvest of the particular plant if it has one or more infected fruits or vegetables. Wait until the specific fruit or vegetable falls off and start harvesting, preventing the risk of infection to those consuming.

• Follow sanitation protocols indoors, in the garden, and in the fields.

Conclusion:

Though Alternaria's effects are not as common in humans as in plants, a few cases have been reported. The impact of Alternaria in humans is mostly mild. Still, caution should be taken in immunocompromised individuals as they are more prone to infections caused by Alternaria and, if infected, can become more severe than others who are normal. Maintaining proper field and garden sanitation can help prevent disease by the fungus - Alternaria.