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What are ectoparasitic infections?

Feb 11, 2008, 04:23

Ectoparasitic Infections

Ectoparasitic infections are diseases that are caused by tiny parasitic bugs, such as lice or scabies. They are transmitted by close physical contact, including sexual contact. The parasites affect the skin or hair and cause itching.

What are pubic lice (pediculosis pubis)?

Pubic lice, also called nits, are small bugs that actually are visible to the naked eye. That is, they can be seen without the aid of a magnifying glass or microscope. The scientific term for the responsible organism, the crab louse, is Phthirus pubis. These parasites live within pubic or other hair and are associated with itching.

The treatment for pubic lice is usually with a 1% cream rinse of permethrin that is applied to the affected area and washed off after 10 minutes. Alternative treatments include a 1% shampoo of lindane applied for 4 minutes before washing off or pyrethrins with piperonyl butoxide applied for 10 minutes before washing off. None of these treatments should be used for involvement near the eyes because they can be very irritating. The patient's bedding and clothing should be machine-washed with hot water. All sexual partners within the preceding month should be treated for pubic lice and evaluated for other STD's. For more information, please read the Pubic Lice article.

What is scabies?

Scabies is an ectoparasitic infection caused by a small bug that is not visible with the naked eye, but can be seen with a magnifying glass or microscope. The bug is a mite known as Sarcoptes scabiei. The parasites live on the skin and cause itching over the hands, arms, trunk, legs, and buttocks. The itching usually starts several weeks after exposure and is often associated with small bumps over the area of itching. The itching of scabies is usually worse at night.

The standard treatment for scabies is with a 5% cream of permethrin, which is applied to the entire body from the neck down and then washed off after 8 to 14 hours. An alternative treatment is one ounce of a 1% lotion or 30 grams of cream of lindane, applied from the neck down and washed off after approximately 8 hours. Since lindane can cause seizures, it should not be used after a bath or in patients with extensive skin disease or rash. This is because the lindane might be absorbed into the blood stream through the wet or diseased skin. As an additional precaution, this medication should not be used in pregnant or nursing women or children younger than 2 years old.

Ivermectin is a drug taken by mouth that has also been successfully used to treat scabies. The CDC recommends taking this drug at a dosage of 200 micrograms per kilogram body weight as a single dose, followed by a repeat dose two weeks later. Although taking a drug by mouth is more convenient than applying the cream, ivermectin has a greater risk of toxic side effects than permethrin and has not been shown to be superior to permethrin in eradicating scabies.

Bedding and clothing should be machine washed in hot water (as with the treatment of pubic lice). Finally, all sexual and close personal and household contacts within the month before the infection should be examined and treated.

Sexually Transmitted Infections in Men At A Glance

       Sexually transmitted diseases (STDs) can be spread (transmitted) by intercourse, kissing, oral-genital contact, and sharing sexual devices.

       Aside from abstinence, the use of latex barriers, such as condoms, during intercourse and oral-genital contact (although not 100% effective) is the best means of preventing the spread of STDs.

       Genital or oral ulcers are most often caused by herpes simplex, chancroid, syphilis, and lymphogranuloma venereum.

       Syphilis infection can either produce no symptoms or can cause oral or genital ulcers, rash, fever, or a variety of neurological illnesses ranging from forgetfulness to strokes.

       Chlamydia and gonorrhea can be transmitted alone or together and cause inflammation of the urethra (urethritis), which the patient experiences as burning on urination and a penile discharge (dripping).

       The human immunodeficiency virus (HIV), which causes the acquired immunodeficiency syndrome (AIDS), is spread by infected blood or sexual secretions and is often associated with one or more of the other STDs.

       Human papillomavirus (HPV) causes genital warts and is associated with the development of anogenital carcinomas such as cervical carcinoma in women and anal or penile cancers in men.

       Hepatitis B is transmitted primarily through sexual contact while hepatitis C is transmitted more commonly by contact with infected blood.

       Human herpes virus 8 (HHV-8) is a recently identified virus that may be transmitted sexually and has been associated with Kaposi's sarcoma (an unusual skin tumor), and possibly certain lymphomas (tumors of the lymph tissue).

       Pubic lice and scabies are tiny parasitic bugs that can be spread by skin-to-skin contact.

For more information please read the Sexually Transmitted Diseases (STDs) in Women article.