Infections And Infestations - part 3

Antimalarial medicaments

Of all the infectious diseases that afflict mankind, the one that causes more illness and more deaths worldwide is malaria. Malaria is caused by single-cell protozoa whose life cycle is far from simple. A parasite, the malaria plasmodium, as it is called, lives in and depends on the female anopheles mosquito during one part of its life. It lives in and depends on human beings during other parts of its life cycle.

Transferred to man in the saliva of the mosquito as she penetrates ("bites") the skin, the malaria parasite enters the bloodstream and settles in the liver. Although no symptoms appear yet, the malaria parasite multiplies, asexually.

Following its stay in the liver, the parasite enters another phase of its life cycle, circulating in the bloodstream, penetrating and destroying red blood cells and reproducing again, the results this time including male and female forms of the parasite. If the sexual forms then transfer back to a female anopheles mosquito via another "bite," they breed once more (bisexually), and are again ready to start a human infection.

It is after the emergence from the liver, when the plasmodia are entering and rupturing the red blood cells, that malaria appears in its classic, symptomatic form: high fever and profuse sweating, alternating with equally agonizing episodes of shivering and chills. One strain of malaria (there are four) can produce a single severe attack, possibly fatal if untreated. The other forms of malaria cause recurrent attacks, sometimes extending over many years.

A number of medicaments are available for malaria, the choice depending on many factors, such as the region in which the disease may have been contracted.

Most antimalarial medicaments act by rapidly killing plasmodia in the bloodstream. Taken as a suppressive, the medicaments kill the plasmodia before they enter the liver, so stopping them from multiplying. Once the plasmodia have multiplied in the liver, the same medicaments given in higher doses kill the parasites that reenter the bloodstream.

The low doses of antimalarial medicaments taken to suppress the disease rarely cause noticeable effects. Medicaments taken for an attack usually begin to relieve symptoms within a few hours. Most of them can cause nausea, vomiting, and diarrhea. More seriously, quinine can produce giddiness, noises in the ear, and disturbances in vision and hearing.

When medicaments are given to suppress or cure malaria the full course of treatment must be taken. No medicaments give long-term protection: new treatment is needed for each journey. Because no medicament is effective against every type of malaria, a change of antimalarial medicament may be necessary when traveling from one malarial area to another where a different form of malaria may be prevalent.

Though most of these medicaments do not produce severe adverse effects, primaquine can cause the blood disorder hemolytic anemia, particularly in people with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Hence, blood tests are taken before treatment to identify susceptible individuals.

Antifungal medicaments

We are continually exposed to fungi - in the air we breathe, the food we eat, and the water we drink. Fortunately, most of them cannot live in the body, and few are harmful. But some can grow in the mouth, skin, hair, or nails, causing irritating or unsightly changes, and a few can cause serious and possibly fatal disease. The most common fungal infections are caused by the tinea group of infections. These include tinea pedis (athlete's foot), tinea cruris (jock itch), and tinea capitis (scalp ringworm). They are caused by a variety of organisms and may be spread by direct or indirect contact with infected humans or animals. Infection is encouraged by warm, moist conditions.

Problems may also result from the proliferation of a fungus normally present in the body; the most common example is excessive growth of candida, a yeast which causes thrush infection of the mouth, vagina, and bowel. It can also infect other organs if it spreads through the body via the bloodstream.

Overgrowth of candida may be provoked by diabetes, pregnancy, immune system disorders such as AIDS, treatment with antibiotics, or by taking oral contraceptives

Superficial fungal infections - those that attack only the outer layer of the skin and mucous membranes - are relatively common and, although irritating, do not usually present a threat to general health. Internal fungal infections  -for example, of the lungs, heart, or other organs - are rare, but may be serious and prolonged.

Because antibiotics and other anti-bacterial medicaments have no effect on fungi and yeasts, a different type of medicament is needed. Medicaments for fungal infections are either applied topically to treat minor infections of the skin and mucous membranes or given by mouth or injection to eliminate serious fungal infections of the internal organs and nails.

Most of these medicaments alter the permeability of the fungal cell's walls. The chemicals essential for cell life leak out and the cell dies.

The speed with which antifungal medicaments provide benefit varies with the type of infection. Thrush and most other fungal or yeast infections of the skin, mouth, and vagina improve within a week. The condition of nails affected by fungal infections improves only when new nail growth occurs, and this takes many months. Systemic infections of the internal organs can take weeks to cure.

Antifungal medicaments applied topically rarely cause side effects, although they may irritate the skin. However, treatment by mouth or ingestion for systemic and nail infections may produce more serious side effects. Amphotericin B, injected in cases of life-threatening systemic infections, often causes unpleasant and potentially dangerous effects, notably a severe fever that may require other medicaments. Because this medicament may also cause kidney damage, sufferers need regular blood tests. Griseofulvin, given for persistent nail infections, carries a risk of liver damage. For this reason it is prescribed only when topical treatments have failed and nail damage is severe.

Anthelmintic medicaments

Anthelmintics are medicaments that are used to eliminate the many types of worm (helminths) that can enter the body and live there as parasites, producing a general weakness in some cases, and serious harm in others. The body may be host to many different worms. Most species spend part of their life cycle in another animal, and the infestation is often passed on to humans in food contaminated with the eggs or larvae. Some larvae, such as those of hookworm, enter the body through the skin. Larvae or adults may attach themselves to the intestinal wall and feed on the bowel contents; others feed off the intestinal blood supply, causing anemia. Worms can also infest the bloodstream or lodge in the muscles or organs.

Many people have worms at some time during their life, especially during childhood; most can be effectively eliminated with anthelmintic medicaments.

The anthelmintic medicaments act in several ways. Many of them kill or paralyze the worms, and they pass out of the body in the feces. Others, that act systemically, are used to treat infection in the tissues. Many anthelmintics are specific for particular worms, and the physician must identify the worm before selecting the most appropriate treatment. Most common infestations of the intestine are easily treated, often with only one or two doses of the medicament. However, tissue infections may require more prolonged treatment.

Once the medicament has eliminated the worms, symptoms caused by infestation rapidly disappear. Taken as a single dose, or a short course, anthelmintics do not usually produce side effects. However, treatment can disturb the digestive system, causing abdominal pain, nausea, and vomiting.

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