The members of the genera Babesia and Theileria are protozoan parasites. These organisms are of medical, veterinary, and economic importance. Babesia species cause disease in humans and animals.
Non-falciparum Malaria (P Vivax, P Ovale, P Malariae)
Patients with nonfalciparum malaria invariably develop fever and chills that may become cyclic. Initially, patients experience chills, which are followed by fever (Box 1). Patients with malaria often manifest many nonspecific symptoms such as weakness, malaise, headache, and myalgias. As the disease progresses, signs of anemia, such as pale conjunctiva, may be seen.
Falciparum Malaria
Fevers are often continual, with irregular spikes and associated chills and paroxysms. Patients with severe falciparum malaria may disclose central nervous system changes (prostration, convulsions, and impaired consciousness) and develop respiratory distress, abnormal bleeding, and circulatory collapse. Fatigue and malaise are nonspecific symptoms of malaria. These are in part caused by hypoglycemia and anemia.
Pneumocystis Carinii
In 1983, P carinii pneumonia (PCP) was described as the AIDS-defining illness in = 60% of the first 1000 patients diagnosed with AIDS in the United States. Subsequently, the advent of prophylactic measures has reduced the incidence of PCP presenting as the initial diagnosis for AIDS to < 50% of cases. In addition, the hospitalization rate is also declining for patients with AIDS who also have PCP. This decline has presumably been caused by successful use of prophylaxis against the organism.
Extrapulmonary P Carinii Infections
Extrapulmonary P carinii infections occur in < 3% of patients and must be diagnosed with histopathologic samples. Primary prophylaxis for PCP with pentamidine may confer a higher risk for extrapulmonary infection. Symptoms of extrapulmonary involvement are nonspecific, usually consisting of fevers, chills, and sweats.
Dermatophytes
Dermatophytes are molds that infect keratinized tissues including skin, hair, and nails. Whereas 40 dermatophyte species are known to infect humans, only about 15 of these are common causes of disease. These organisms belong to three genera, Microsporum, Trichophyton, and Epidermophyton. Because these fungi have such similar infectivity, morphology, and pathogenicity, they are often categorized according to the clinical syndrome and the preferred anatomic site with which they are associated, such as tinea capitis, tinea pedis, etc.
Fusarium, Penicillium, Paracoccidioides, & Agents of Chromomycosis
Fusarium spp. is an emerging fungal pathogen. Although long recognized as a cause of local infection involving nails, traumatized skin, or the cornea (eg, in contact lens wearers), deep or disseminated infection was not described until the mid 1970s. Despite its worldwide distribution and its frequent recovery from soil and vegetative material, infection is quite rare. Only ~ 100 cases involving invasive disease in immunosuppressed patients have been described in the medical literature.
Chromomycosis
Chromomycosis, also known as chromoblastomycosis, is a chronic subcutaneous infection caused by several different fungi. Although rarely seen in the United States, it is common worldwide. Chromomycosis occurs worldwide but is most frequently encountered in tropical and subtropical regions. The most common occurrence is in barefoot individuals, particularly among agricultural workers.
Paracoccidioidomycosis
Paracoccidioidomycosis is caused by Paracoccidioides brasiliensis. Also known as South American blastomycosis, it is the most prevalent systemic mycosis found in Central and South America and is the most common endemic mycosis in this area. Paracoccidioidomycosis is acquired only in Central and South America and ranges from Mexico to Argentina.
Penicillium Infections
Penicillium spp. are ubiquitous in nature and may be recovered with ease from a variety of sources within the hospital environment. These molds commonly contaminate clinical specimens and cause contamination in the laboratory. Colonization of nonsterile anatomical sites in humans is common. In most cases where Penicillium spp. are recovered from clinical specimens, they represent colonization.