Ringworms (cutaneous mycoses), Biology

Ringworms (cutaneous mycoses)


Cutaneous mycoses – also called dermatomycoses, occur worldwide and represent the most common fungal diseases in humans. The dermatophytes are the fungi that infect only the epidermis and its appendages (hair and nails), i.e., structures in which keratin are abundant. The skin lesions are usually circular, tend to expand equally in all directions, and have raised borders. They are, therefore, thought in ancient times to be due to worms or lice, and they are still called ringworms or tinea (worms or insect larvae). The names are usually qualified by the area of skin involved, e.g., ringworm of scalp (tinea capitis), of the body (tinea corporis), of the groin (tinea cruris) and of the feet (athete’s foot, tinea pedis).


Epidemiology:

Three genera of dermatophytes are involved in ringworm:
Epidermophyton, Microsporum and Trichophyton.

Several species of dermatophytes are primarily found in human skin (anthrophilic), some are indigenous in domesticated and wild animals (zoophilic), and a few are free living and are isolable from soil (geophilic).


Infection is transmitted from man-to-man or animal-to-man or vice versa by direct contact or by contact with infected hairs and epidermal scales. The reservoir of animal infection is large. Dogs and cats are commonly infected with Microsporum canis, which is a frequent cause of ringworm in children also.


The incidence of different dermatomycoses varies with age. For example, athlete’s foot is common in adults but rare in children, whereas the opposite is true for ringworm of the scalp. Resistance of adults to scalp infection has been linked to the increases secretory activity of the sebaceous glands at puberty and the antifungal activity of unsaturated fatty acids in sebum. Most dermatophytes have a worldwild distribution.


Clinical features:
The dermatophytes infect skin, hair, nail and scalp, and the clinical features vary with the site of infection. When skin is infected, there is irritation, erythema, oedema and some vesiculation, especially at the spreading edge, and this

 

164_Ringworms (cutaneous mycoses).jpg

irregular pink periphery gives rise to the name ringworm. Secondly infection or vigorous treatment may give rise to formation of vesicle, pustules and ulceration.Infection of the nails renders them irregular, discoloured and friable. The fungal grows deep into the substance of the nail. When the scalp is infected, the fungus grows in the horny layer of the epidermis and down into the hair follicles. The hyphae surround and invade the hair shaft. Some species of dermatophytes grow only within the shaft (endothrix infections) but others more commonly on the outside (ectothrix infections). After 2 to 3 weeks’ growth the weakened hair breaks off, leaving a black dot at the follicle mouth as in endothrix infections or a grey spore-covered stump in the ectothrix infections.


Diagnosis: Diagnosis of ringworm is based on direct demonstration of fungal hyphae and arthrospores in the infected tissue by microscopy and by culturing the fungus in the laboratory.


Control and prevention: Dermatophyte infections are not easy to prevent. They produce arthrospores which are very resistant to environmental conditions and are transmitted by direct or indirect contact or through the hair. The infections due to dermatophytes, however, can be reduced by raised standards of hygiene in the home, at the school and hair dressing establishments by keeping feet dry and clean, and by avoiding the sharing or exchanging of caps, socks and underclothes.

Posted Date: 9/20/2012 3:10:47 AM | Location : United States







Related Discussions:- Ringworms (cutaneous mycoses), Assignment Help, Ask Question on Ringworms (cutaneous mycoses), Get Answer, Expert's Help, Ringworms (cutaneous mycoses) Discussions

Write discussion on Ringworms (cutaneous mycoses)
Your posts are moderated
Related Questions
Properties of Sols Sol, is  a solid liquid dispersion with solid or semi-solid particles dispersed in a continuous liquid phase. For e.g. starch in cold water. Sols exhibit ch

Prevention and Community Action: A number of  preventive action are necessary. Alcohol prevention programmes can have major effects on alcohol problem rates, and can influence

CELLULOSE It is a linear polymer of b -D-glucose. It is the structural polysaccharide of plant cell walls, walls of some primitive fungi, some protists, and tunic of asci

What is leaf cuticle? Leaf cuticle is a thin waxy layer made of waxes and cutin on the outer surface of the leaf epidermis. Its function is near control the cellular transpirat

Q. What are some diseases caused by abnormal GH secretion by the hypophysis? In childhood deficient GH secretion may lead to delayed growth and in severe cases to nanism that i


Mrs. Jackson is a 76 year old woman living in a skilled nursing facility. She has Hx: CVA with left-sided weakness, incontinent of bowel and bladder, PEG tube, GERD, HTN, Dementia,

Explain about Atrial Septal Defect (ASD) ? ASD occurs as an isolated anomaly in 5- 10 per cent of all CHDs. These communications occur in four sites i.e. in the central portion


Name of the ductless glands that secrete their product into the circulatory system are: a) Exocrine (pron: ek-seh-kren) b) Apocrine (pron: ap-eh-kren) c) Holocrine (pron: