19: Eukaryotic Pathogens and Diseases

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19.1: Mycoses of the Skin and Eyes
Mycoses can be cutaneous, subcutaneous, or systemic. Common cutaneous mycoses include tineas caused by dermatophytes of the genera Trichophyton, Epidermophyton, and Microsporum. Tinea corporis is called ringworm. Tineas on other parts of the body have names associated with the affected body part. Aspergillosis is a fungal disease caused by molds of the genus Aspergillus. Primary cutaneous aspergillosis enters through a break in the skin, such as the site of an injury or a surgical wound.
19.2: Protozoan and Helminthic Infections of the Eyes
The protozoan Acanthamoeba and the helminth Loa loa are two parasites that can breach the skin barrier, causing infections of the skin and eyes. Acanthamoeba keratitis is a parasitic infection of the eye that often results from improper disinfection of contact lenses or swimming while wearing contact lenses. Loiasis, or eye worm, is a disease endemic to Africa that is caused by parasitic worms that infect the subcutaneous tissue of the skin and eyes. It is transmitted by deerfly vectors.
19.3: Respiratory Mycoses
19.4: Fungal Infections of the Reproductive System
Candida spp. are typically present in the normal microbiota in the body, including the skin, respiratory tract, gastrointestinal tract, and female urogenital system. Disruptions in the normal vaginal microbiota can lead to an overgrowth of Candida, causing vaginal candidiasis. Vaginal candidiasis can be treated with topical or oral fungicides. Prevention is difficult.
19.5: Protozoan Infections of the Reproductive System
Trichomoniasis a common STI caused by Trichomonas vaginalis. T. vaginalis is common at low levels in the normal microbiota. Trichomoniasis is often asymptomatic. When symptoms develop, trichomoniasis causes urinary discomfort, irritation, itching, burning, discharge from the penis (in men), and vaginal discharge (in women). Trichomoniasis is treated with the antiflagellate drugs tinidazole and metronidazole.
19.6: Protozoan Infections of the Gastrointestinal Tract
Like other microbes, protozoa are abundant in natural microbiota but can also be associated with significant illness. Gastrointestinal diseases caused by protozoa are generally associated with exposure to contaminated food and water, meaning that those without access to good sanitation are at greatest risk. Even in developed countries, infections can occur and these microbes have sometimes caused significant outbreaks from contamination of public water supplies.
19.7: Helminthic Infections of the Gastrointestinal Tract
Helminths are widespread intestinal parasites. These parasites can be divided into three common groups: round-bodied worms also described as nematodes, flat-bodied worms that are segmented (also described as cestodes), and flat-bodied worms that are non-segmented (also described as trematodes). The nematodes include roundworms, pinworms, hookworms, and whipworms. Many of these parasites are so well adapted to the human host that there is little obvious disease.
19.8: Parasitic Infections of the Circulatory and Lymphatic Systems
19.9: Neuromycoses and Parasitic Diseases of the Nervous System
Fungal infections of the nervous system, called neuromycoses, are rare in healthy individuals. However, neuromycoses can be devastating in immunocompromised or elderly patients. Several eukaryotic parasites are also capable of infecting the nervous system of human hosts. Although relatively uncommon, these infections can also be life-threatening in immunocompromised individuals. In this section, we will first discuss neuromycoses, followed by parasitic infections of the nervous system.