Humans are susceptible to infection by a number of parasitic species of fungi, protozoa, and helminths (worms). Although some types of parasitic infections are limited or unknown in developed nations such as the United States, parasitic infections generally represent the most common form of disease worldwide. These infections are especially prevalent in tropical and subtropical environments and in impoverished areas of the world where sanitation and hygiene are inadequate. In addition, the incidence of serious fungal and other parasitic infections has been increasing in industrialized nations because of the increased susceptibility of immunocompromised patients to these infections, such as patients with AIDS or those receiving immunosuppressant drugs after organ transplantation.1–3 Hence, the effective pharmacological treatment of these infections remains an important topic in the global management of disease.
The pharmacological treatment of parasitic infections is a complex and extensive topic. In this limited space, it is difficult to describe the many species of each parasite, all the diseases caused by parasites, and the chemical methods currently available to selectively destroy various fungi, protozoa, and helminths in humans. Consequently, this chapter briefly reviews the general aspects of the three types of parasites, followed by the primary drugs used to treat specific fungal, protozoal, and helminthic infections. Certain infections such as superficial fungal infections that cause athlete's foot and similar conditions are quite common, and clinicians may be involved in helping treat and prevent these infections. As indicated above, more serious fungal and parasitic infections can occur in patients who are immunocompromised or in locations where patients are exposed to these infections. The drugs used in these more serious infections can be quite toxic and cause adverse effects that impact rehabilitation procedures. This discussion will therefore acquaint physical therapists and occupational therapists with these infections and will address the positive and negative aspects of the chemotherapeutic techniques and agents administered to treat these problems.
Fungi are plantlike microorganisms that exist ubiquitously throughout the soil and air and in plants and animals. Fungi are abundant in nature (over 200,000 species have been identified), and approximately 200 species can cause infections in humans.4,5 A disease caused by fungal infection is also referred to as a mycosis. Some fungal infections are relatively local or superficial, affecting cutaneous and mucocutaneous tissue. Examples of common superficial fungal infections include the tinea (ringworm) infections that cause problems such as athlete's foot. Common mucocutaneous fungal infections include candidiasis and yeast infections of vaginal tissues. Other fungal infections are deeper or more systemic. For instance, fungal infections may affect the lungs, central nervous system (CNS), or other tissues and organs throughout the body.6–8
Often, fungal infections are relatively innocuous because they can be destroyed by the body's normal immune defense mechanisms. However, some infections require pharmacological treatment, especially if the patient's endogenous defense mechanisms are ...