Dermatophytes that causes Cutaneous mycoses in humans and How to deal with it.

Keywords:

Mycoses. "Skin Plants" Tinea. Ringworm. Anthropophilic. Zoophilic. Geophilic. Spore. Fungi. Erythema.Alopecia.

introduction

Formerly under the Plant kingdom, Dermatophytes are now a distinct group of living organisms. To accommodate the vast diversity of living organism into a taxonomic relationship, Whittaker(1969), proposed the five-kingdom system, namely, plantae, animal, fungi, protista, and monera. Dermatophytes (literally: "skin plants"), is now under the Kingdom Fungi, Most widely cited estimate 1,5 million is 6 times more diverse than plants, yet only about 100,000 species have so far been described.Their mode of nutrition separates them from plants, they're none- chlorophyllous, they can't manufacture their own food, therefore, they have to rely on other organisms for food, they are heterotrophic while plants are autotrophic that is plants are capable of manufacturing their own food. Dermatophytes and the rest of the taxon are scavengers, saprophytes, and decomposers, a very important attributes in the recycling of energy, moreover, dermatophytes are harmful to man.

Dermatophytes- What are they?

• Dermatophytes fall under Kingdom Fungi. All dermatophytes, except for few, produce proteolytic and keratolytic enzymes that enable them to utilize keratin as the sole source of nutrition after colonization of the dead, keratinized portion of epidermal tissue, hairs, and nails.
• By segmentation and fragmentation, dermatophytes. produces arthrospores which are highly resistant, surviving in the dry environment. High temperatures(100^o C)destroy them while arthrospores adhere strongly to keratin.
• Depending on the source of infection and reservoirs, dermatophytes species are classified into three groups:

1. Zoophilic- animal dwelling
2. Geophilic- soil dwelling
3. Anthropophilic- human dwelling

• Causative agents of Dermatophytosis belong to three genera, Epidermophyton, Microsporum, and Trichophyton

Classification, Occurrence and Distribution

• Dermatophytes are are one of the most common sources of human fungal infection.
• Annually affects millions of individuals and are estimated in United States healthcare system to the tune of 400 million dollars each year for prevention alone.
• Dermatophytes thrive best in warm and humid climate and are therefore common in tropical and sub-tropical regions. Their distribution varies with the organism, hosts, social and cultural activities of man.
• Some species were reported in Asia, Africa, and Europe(Trichophyton simii), this suggests the widespread distribution of the fungus.
• Zoophilic species associated with certain animals or pets are specific to their environment where they are found(T. erinacci) with hedgehogs.Reported in Europe, Newzealand, and Africa.
• Trichophyton bullasum has been detected in Tunisia, Sudan, Syria, and France along with zoophilic species.
• Anthropophilic dermatophytes may either cosmopolitan or limited, but may be imported to other countries by infected individuals

Taxonomic Classification

Dermatophytes are divided into three main groups based on their location and modes of transmission, namely;

1. zoophilic- animal reservoirs
2. geophilic- soil dwelling
3. anthropophilic- human specific

There are 34 known Dermatophyte species, 19 are known to be pathogenic to humans and 13 are caused of common infections. furthermore, these fungi are classified into three genera:

1. Trichophyton- 20 species
2. Microsporum- 13 species
3. Epidermophyton- 1 species

These Dermatophytes causes Tinea (latin for "worm" or "ringworm" is a misnomer, no worm is involved) infections that involve the superficial areas of the body including the hair, skin, and the nails. The table shows that the skin is the best substrate for infection and among the Dermatophytes, Trichophyton species is widely infective.

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classification based on the Location of infections

Dermatophytosis can be classified on the basis where the site of the infection occurs, they are classified as:

• Tinea capitis -ringworm infection of the Head, Scalp, Eyebrows, Eyelashes
• Tinea favosa -ringworm infection of the Scalp(scaly hair)
• Tinea corporis -ringworm infection of the Body(smooth skin-glabrous)
• Tinea cruris -ringworm infection of the Groin(jock itch)
• Tinea uguium -ringworm -ringworm infection of the Nails
• Tinea barbae -ringworm infection of the Beard
• Tinea manuum -ringworm infection of the Hand
• Tinea pedis -ringworm infection of the Foot(athlete's foot)

Dermatophytes are keratinophilic-"keratin loving". Keratin is a major protein found in hooves, horns, nails, hair, and skin. The infection caused by this fungus is called ringworm.Ringworm is a disease called "herpes" by the Greeks and by the Romans "tinea"( which means small insect larvae)The fungal species that cause different clinical manifestations of ringworm are:

• Microsporum -infection of the skin and hair
• Epidermophyton - infection of the skin and nails
• Trichophyton - infection of the skin, hair, and nails

Symptoms and Manifestation of Infections

• In unhaired (glabrous) skin, the lesion is usually characterized by inflammation that is severe in the edges with erythema (redness of the skin), scaling, and occasional blister formation.
• The central area may clear resulting in classic ringworm lesion
• In haired areas, the hair becomes brittle and areas of alopecia (hair loss) may appear.
• Dermatophytes acquired from soil or animals generally produce more inflammatory lesions than anthropophilic dermatophytes.

Five most common Dermatophytes that causes infections in humans:

1. Trichophyton rubrum - is the quantitatively the most common dermatophyte species causing infection in humans. Anthrophile (human specific) and is not capable of mating.The fungus is the most frequent cause of fungal infections in humans and is found throughout the world.
2. Microsporum canis - is the most common encountered zoophile (animal source) in human infection. A common cause of Tinea capitis (fungal head infection) in Europe. Also a problem in pets including dogs, cats, where it causes ringworm
3. Microsporum gypseum - is a geophile (soil source), In humans, it causes skin infection of the head and torso.
4. Trichophyton fonsurans - is an anthropophile without mating ability. Endemic to NorthAmerica and most common scalp infection in children in US, Canada and the Latin American countries.
5. Trichophyton equium - is a zoophilic human pathogen and a significant cause of ringworm in horses with impact in horse breeding.

Take a QUIZ?

Matching Type. Match Column A with B. LETTERS ONLY.

COLUMN A COLUMN B

1. Spore a) soil dwelling
2. Anthropophilic b) hair loss
3. Dermatophyte c) ringworm of the nails
4. Erythema d) redness of skin
5. Geophilic e) skin plants
6. Alopecia f) human specific
7. Tinea pedis g) ringworm of the head
8. Tinea capitis h) animal reservoir
9. Tinea cruris i) asexual form
10. Zoophilic j) athlete's foot

SCORE: Excellent -10, Very Good -8-9, Good -6-7, Average -5

Mode of transmission and how to avoid infections

Ringworm is a scalp, nails, and skin disease caused by fungi.It gets its name from the chronic ring-like rash in the skin.The disease is spread by touching an infected person or animals. It can also be spread by touching surfaces that had contact with the infection.The infected person often begins itching four or fourteen days after contact (CDC, 2014).

Major source of Ringworm infection

• Infected persons
• Schools. Military Camps, Prison
• Warm and damp areas of the tropics, moisture accumulation in clothing and shoes, boots, etc.
• Animals, pets dogs, cats, cattle, horses, poultry, etc.
• Public places, baths, swimming pool, theater, etc.
• Home furnishing, rugs, carpet, upholstery, etc.
• Borrowed items- combs, brush, pants, shoes, socks, etc.

Who are at Risks?

1. Children - first 2 years of life very susceptible to infection, young adults, and elderly
2. Persons with immune system deficiency
3. Suffering from disease or metabolic disorders (eg.Diabetes)
4. Persons with nutritional deficiency especially proteins and Vit, A
5. Working in conditions with high temperature and humidity
6. Persons having skin trauma resulting from;

• increased moisture that soften skin linings (tight shoes, boots, etc.)
• injury by ectoparasites
• scratches due to pruritus (severe itching)
• playing aggressively that lead to skin injury
• Clippings, etc

7. People with domestic animals at home

8.Athletes

9. Spores (conidia) that survive more than 2 years under favorable condition

Prevention and treatment

• There is no better way of avoiding Dermatophyte infection except Hygiene especially personal one
• Remember that fungal infection due to Dermatophytes is transmitted based on three sources, that is Anthropophilic ( human specific}, Zoophilic (animal reservoir), and Geophilic (soil dwelling). In theory, it is believed that infection begin from the soil, but it may start from any of these agents.
• Prevention should center from these three causative agents and relates to who are at risks most.
• The possible sources of infection should be considered in disease prevention, that "an ounce of prevention is better than a pound of cure"
• Drugs to treat this malady is now available in drugstores both as a topical application or oral medicine. Some can be bought over the counter on drugstores, but others need a prescription from physicians.
• Above all, if in doubt consult knowledgeable persons, physicians, or health care specialist for proper medication.

Conclusion

A fungal infection caused by Dermatophytes should not be taken for granted Everyone should be cognizant of its effect on animal and human health. Risks factors for those who are susceptible to tinea's infection should take precautionary measures. Take care of your skin since this is the first line of defense against Dermatophyte infection. Hygiene should be practiced in any form to prevent infection. Preventive measures should consider the three possible sources of infection that is an animal (zoophilic), soil (geophilic) and humans (anthropophilic). If in doubt consult a physician or healthcare specialist. Above all, "an ounce of prevention is better than a pound of cure."

References

Scholarly Articles

David Moore's World of Fungi: Where Mycology Start- www. davidmoore. org. uk

Dermatophytosis: Ringworm, Tinea 2013. The Center for Food and Security and Public Health, Iowa State University - www.cfsph.ietstat.edu

Dermatophytes.Wikipedia, the Free Encyclopedia

The Fungi Kingdom. Kew-Royal Botanical Garden - www.Kew.org/ science

Henn, Matthew.Genomic Determinants of Infection Competence in DermatophyteFungi (white Paper) - www.genome.gov/ National Human Genome Research Institute

Perez Aguar de, N, et al. 2010. Dermatophyte: host-Parasite Interaction and Fungal Resistance. An Bras Dermatol 8 (5):657-667.

Ringworm. Center for Disease Control and Prevention (CDC)April, 30, 2014 - www.cdc.gov/ health

Smith, John. 2012. Does your Dog have Ringworm? - www. howtocureringworm . com