Physical Address

304 North Cardinal St.
Dorchester Center, MA 02124

Laboratory Diagnosis of Infection Due to Viruses, Chlamydia, and Mycoplasma

Viruses The availability of rapid and reliable viral diagnostic tests, particularly nucleic acid amplification tests (NAATs), facilitates decision making in the prevention, treatment, public health, and infection control measures related to viral infections. With specific antiviral therapy available for many clinically relevant viruses, a specific viral diagnosis may limit the need for further diagnostic testing and unnecessary antibiotic therapy. Two major approaches to diagnosis of viral…

Laboratory Diagnosis of Infection Due to Bacteria, Fungi, Parasites, and Rickettsiae

Bacteria Collection and Processing of Clinical Specimens Proper collection and handling of clinical specimens is a crucial first step in the microbiologic diagnosis of an infectious disease. No degree of laboratory expertise can correct the errors of inappropriately collected and transported specimens. Common problems include submission of insufficient quantities of specimens; contamination of specimens with microbial flora present in and on the patient; use of inappropriate…

Blood Trematodes: Schistosomiasis

Schistosomiasis (i.e., bilharzia or snail fever) is a parasitic infection caused by trematodes that reside in the circulatory system. More than 230 million people worldwide suffer from schistosomiasis, which causes a range of disease from overt clinical manifestations to subtle hindrance of day-to-day activities. Infected children can have impaired growth and development. Infection occurs from exposure to freshwater into which snails, the intermediate host of the…

Clonorchis, Opisthorchis, Fasciola, and Paragonimus Species

Liver and lung trematodes are hermaphroditic, zoonotic flukes that use snails as intermediate hosts ( Table 284.1 ). Snails are infected by eggs in feces passed into the environment by humans and other mammals. The snails release cercariae that encyst in second intermediate hosts (i.e., fish, crustaceans, and amphibians) or on water plants. When encysted cercariae are ingested, humans and other definitive hosts become infected. TABLE…

Intestinal Trematodes

More than 70 species of zoonotic, hermaphroditic intestinal flukes can parasitize the human intestine. Most human infections are asymptomatic, but heavy infections are more likely to result in clinical disease. Adult flukes are flat and leaf-shaped, ranging in length from a few millimeters to several centimeters. They attach to the intestinal mucosa by means of oral and ventral suckers and release eggs having a characteristic operculum…

Taenia (Multiceps) multiceps and Taenia serialis : Coenurosis

Coenurosis is human infection with larval forms of the animal tapeworms Taenia (Multiceps) multiceps and Taenia serialis. The coenurus is a fluid-filled cyst that is a few millimeters to 2 cm or more in diameter. The wall is a thin, delicate membrane to which multiple invaginated scolices (i.e., protoscolices) are attached in rows or clusters. These zoonotic infections occur primarily in tropical and subtropical regions. Epidemiology…

Echinococcus Species: Agents of Echinococcosis

Echinococcus Granulosus Description of the Pathogen Echinococcus granulosus , which causes cystic echinococcosis, is a cestode whose life cycle involves dogs and other canids as definitive hosts for the intestinal tapeworm. Domestic and wild ungulates are intermediate hosts for the tissue-invading metacestode, which is the larval stage of the tapeworm ( Fig. 281.1 ). The metacestode (i.e., echinococcal cyst) is a fluid-filled, spherical, unilocular cyst that…

Taenia solium, Taenia asiatica, and Taenia saginata : Taeniasis and Cysticercosis

Clinical syndromes associated with infection with Taenia species tapeworms include intestinal disease caused by adult parasites (i.e., taeniasis) and single or multiorgan inflammatory conditions associated with larval stages within tissue (i.e., cysticercosis and coenurosis). Distinguishing morphologic features of adult tapeworms include an anterior scolex and a series of segments (i.e., proglottids) that develop at the base of the scolex and extend distally as the worm grows…

Diphyllobothriidae, Dipylidium and Hymenolepis Species

Diphyllobothriidae Description of the Pathogens Pseudophyllidean cestodes in the family Diphyllobothriidae can cause intestinal tapeworm infections in humans. Around 16 species have been reported to cause human infections, though only six species have been confirmed with modern molecular techniques. In addition to humans, natural definitive hosts for the adult tapeworms generally include wild and domestic fish-eating terrestrial carnivores (e.g., dogs, cats, bears), marine mammals including pinnipeds,…

Blood and Tissue Nematodes: Filarial Worms

Human filariasis encompasses parasitic infections caused by several species of tiny, thread-like nematode worms that affect the skin, lymphatic vessels, and connective and subcutaneous tissues. Although rarely a direct cause of death, some filarial worms, especially the three species causing lymphatic filariasis and the one causing onchocerciasis, cause substantial disability globally. Filarial worms are transmitted by various blood-feeding vectors, including several species of mosquitoes, blackflies, and…

Tissue Nematodes

Tissue nematodes are parasitic roundworms that invade human tissues. Many of these nematodes are present in outdoor environments and are transmitted to children through the ingestion of nonfood substances. Most of these tissue parasites are zoonoses, with the infectious stage occurring in another animal host. However, infections in a child may result in permanent changes in cognitive ability, development, or vision. This chapter focuses on some…

Intestinal Nematodes

Intestinal nematode infections are caused by a group of helminths, sometimes referred to as soil-transmitted nematodes, soil-transmitted helminths, or geohelminths. They are among the most common parasitic infections in humans and affect more than one-seventh of the world’s population. In most endemic populations, children are affected disproportionately by intestinal nematodes and often acquire infections of high intensity (i.e., large numbers of worms in the gastrointestinal tract)…

Trypanosoma Species (Trypanosomiasis)

Organisms of the genus Trypanosoma are flagellated protozoan parasites that inhabit the blood and tissue of a wide variety of vertebrate hosts, including birds, reptiles, and mammals. The name is derived from the Greek, trypano (meaning auger, a helical shaped tool) and soma (meaning body). The trypanosomes that infect humans in Africa (T. brucei) are transmitted by the bite of Glossina flies, whereas human trypanosomiasis in…

Trichomonas vaginalis

Trichomonas vaginalis can infect both men and women and is recognized as the most common nonviral sexually transmitted infection in the world. Description of The Pathogen T. vaginalis , a flagellated protozoan parasite, was first described in 1836 by French physician Alfred François Donné, who observed these “animalculi” in vaginal fluid under a light microscope. T. vaginalis eukaryotic parasites are typically oval or fusiform, 7–32 μm…

Toxoplasma gondii (Toxoplasmosis)

Toxoplasma gondii , a parasite with worldwide distribution, is responsible for a significant disease burden in humans. Primary infection can be asymptomatic, mildly symptomatic with a mononucleosis like illness and/or lymphadenopathy, or it can cause severe ocular disease, even in immunocompetent people. , It also can result in substantial neurologic and ocular sequelae in congenitally infected children. Atypical and more virulent T. gondii strains can be…

Sarcocystis Species

Sarcocystis species are zoonotic protozoan parasites of the phylum Apicomplexa. Since its first description in 1843, >150 species have been reported from a range of wild and domestic mammals, birds, and reptiles. The organism requires a definitive host and an intermediate host to complete its life cycle. , Definitive-host infection is limited to the gastrointestinal tract (intestinal sarcocystosis), whereas intermediate-host infection leads to the formation of…

Plasmodium Species (Malaria)

Acknowledgment Paul M. Arguin is acknowledged for substantial contributions to this chapter in previous editions. Although malaria is a major cause of morbidity and mortality in the world, most cases in the United States and Europe occur in people who have traveled to or emigrated from endemic areas. Obtaining a travel history from all patients who present with fever and having a high index of suspicion…

Acanthamoeba Species

Description of Pathogen Acanthamoeba are a genera of free-living amebae that can cause localized infection of the central nervous system (CNS), respiratory tract, skin, eyes, and disseminated disease. Nearly 25 named species and at least 20 genotypes of Acanthamoeba have been identified worldwide. Previously, Acanthamoeba were distinguished based on morphologic features into 3 groups (I, II, III); however, molecular techniques have led to distinguishing isolates based…

Naegleria fowleri

Description of the Pathogen Naegleria fowleri is a free-living ameba that causes primary amebic meningoencephalitis (PAM). , It is the only known species of the genus Naegleria pathogenic to humans amongst over 40 other identified species. Two other species, N. australiensis and N. italica, are known to cause disease in experimental animals. , The organism is a facultative pathogen that occurs worldwide in soil and warm…

Microsporidia

Before 1985, few human microsporidial infections had been reported. Since then, the number of cases has increased dramatically because of recognition of this pathogen in patients infected with HIV. Although most reported infections have occurred in HIV-infected people, the organism is recognized increasingly as pathogenic in other immunocompromised populations (e.g., organ transplant recipients), as well as in immunocompetent hosts. Pathogen Microsporidia are obligate, intracellular, spore-forming parasites…