Introduction:
Infections are vast in humans and animals. Although there is a wide range of microorganisms, the majority of infections are commonly caused by either of the three groups of organisms - bacteria, viruses, or fungi. One of the fungal organisms that cause adverse effects not just in animals and humans but also in plants is Alternaria. 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 plus different species under the Alternaria genus. It includes a vast range of pathogenic microorganisms that affect plants, animals, and humans and are widely distributed throughout the living environment. They are majorly responsible for causing adverse effects in plants 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.
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?
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They affect the quality and quantity of the foods produced and tend to decrease the nutritional content of the food.
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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.
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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.
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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 trauma in the cornea from the crops contaminated by this fungi) in humans.
What Are the Common Crops That Are Affected by Alternaria?
Alternaria has shown around 20% of crop destruction. It is commonly found in fruits, vegetables, seeds, and grains.
Fruits: Citrus fruits, apples, cranberries, raspberries, melons, prune nectar, Japanese pears, and so on.
Vegetables: Mainly tomatoes, carrots, peppers, broccoli, and cauliflower.
Seeds: Sunflower seeds, flax seeds, Linseeds, etc.
Grains: Alternaria almost affects all types of grains, the most common among the grains affected by Alternaria 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;
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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.
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High moisture-containing foods favor Alternaria and hence are seen in preharvest and post-harvest crops that have higher amounts of moisture.
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The optimum temperature required for the growth of the Alternaria genus ranges from 22℃ to 30℃.
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They can grow, multiply and cause adverse effects even in unfavorable temperatures. Hence, they are responsible for food spoilage even if they are refrigerated for transport and commercial purposes.
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The common toxins that are produced by the Alternaria genus are phytotoxins (toxins that affect plants and crops and cause destruction) and mycotoxins (present in food items). But, they have the ability to produce a wide range of toxins, almost 70 types of toxins.
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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), and teratogenicity (ability to cause damage to the developing baby), 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. Also, the incubation period is affected by how wet the incubation site is. If the wetness is stable and increased, the incubation period decreases.
How Are Infections Caused by 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?
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Usage of fungicides preharvest has shown no effects on killing the Alternaria species. At the same time, their use post-harvest has shown half the adverse effect reduction.
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Eliminate the source of infection; if a particular crop is a source, deeply burying it or burning it eliminates the chance of further infection.
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Avoid long-time exposure of the crops to water.
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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.
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Follow sanitation protocols indoors, in the garden, and in fields.
Conclusion:
Though Alternaria's effects are not as common in humans as in plants, a few cases have still been reported. The impact of Alternaria in humans is mostly not so profound, but 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.
