Tags: Abdominal pain

Trematodes

Essentials of Diagnosis Blood flukes: demonstration of eggs in feces, urine, or rectal biopsy Liver flukes: demonstration of eggs in feces Intestinal flukes: demonstration of adult worms or eggs in feces Lung flukes: demonstration of eggs in sputum or feces All trematode species that are parasitic for humans are digenetic. Sexual reproduction in the adult fluke is followed by asexual multiplication in the larval stage. Most species of adult trematodes have an oral and ventral sucker. The life cycles of trematodes that are important human pathogens are similar among all five major species. Eggs are excreted in the feces of the host, hatch in fresh water, and require a primary host …

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Cestodes

Human infections caused by cestodes, or tapeworms, may occur within the lumen of the bowel, where adult cestodes attach themselves to the host intestine (Box 1). Alternatively, human infection may be the result of dissemination of cestodes from the bowel to involve extraintestinal sites, often by larval forms of the parasite. The life cycle of cestodes is determined by definitive hosts, in whom the mature adult worm lives, and intermediate hosts, which harbor the larval forms of the parasite. Humans are a definitive host for six cestodes: Diphyllobothrium latum, Taenia solium, Taenia saginata, Hymenolepis diminuta, Hymenolepis nana, and Dipylidium caninum. In addition, humans may be intermediate hosts for Echinococcus granulosis and …

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Diphyllobothrium Latum Infection

Essentials of Diagnosis Stool examination reveals ovoid, yellow-brown eggs (60-75 um by 40-50 um). Chains of proglottids (up to 50 cm long) may be passed in stool. Proglottids are wider than long (3 by 11 mm). Scolex has no hooklets and two grooves (bothria). Gravid proglottid contains rosette-shaped central uterus. General Considerations D latum is found worldwide, and infection is acquired by ingestion of contaminated raw or improperly cooked freshwater fish. Because of enthusiasm for raw or undercooked fish, Siberia, Europe, Canada, Alaska, and Japan are endemic regions for D latum infection. Once the D latum cyst has been ingested, the worm matures within the human intestine and begins to produce …

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African Trypanosomiasis

In Africa, a wide variety of trypanosomes infect wild animals but only two cause significant disease in humans: T brucei gambiense and T brucei rhodesiense. Essentials of Diagnosis • Epidemiologic factors: living or traveling in an endemic zone; exposure to tsetse fly. • History and physical exam: 1. General: periodic fevers, wasting, nutritional deficiencies. 2. Skin: chancre at the site of inoculation, fleeting truncal rash, posterior cervical lymphadenopathy. 3. Neurologic: disturbed sleep patterns (diurnal somnolence, nocturnal insomnia), mental status changes, cerebellar signs. • Laboratory: 1. Blood smear with Giemsa stain shows hemoflagellates. 2. Aspiration and stain of chancre (may be positive for visible organisms before parasitemia occurs). 3. Serology: indirect immunofluorescence, …

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American Trypanosomiasis (Chagas’ Disease)

Essentials of Diagnosis • Epidemiologic factors: time spent in an endemic zone; poor housing conditions, eg, mud or thatched housing; exposure to reduviid insect vector • History and physical exam: Romana’s sign (swollen periorbital mucosal tissues after ocular inoculation); chagoma (skin nodule at the site of acute inoculation); in the chronic phase, congestive heart failure, dysphagia or regurgitation, and constipation • Laboratory exam: 1. Acute Chagas’: trypomastigotes revealed by Giemsa smear of blood or buffy coat; culture of affected tissues, ie, the inoculation site; serologic enzyme immunoassay and enzyme-linked immunosorbent assay (ELISA); xenodiagnosis if available 2. Chronic Chagas’: radiological studies show congestive heart failure, megacolon, or megaesophagus; ECG shows right bundle …

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Giardia

Essentials of Diagnosis • Key symptoms include initially profuse and watery diarrhea progressing to foul-smelling and often greasy stools that float. • It is the most common pathogen in waterborne diarrheal illness. • Patients at highest risk include infants, young children, travelers, and immunocompromised patients. • In North America, the Rocky Mountains and mountainous regions of the northwest, northeast, and British Columbia are notorious Giardia reservoirs. • Giardiasis is diagnosed either by identification of cysts or trophozoites on wet mounts of fresh stool or duodenal specimens or by antigen detection using enzyme-linked immunosorbent assay or immunofluorescence techniques. General Considerations Giardia, a genus of primitive eukaryotes, is a flagellated enteric protozoan of …

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Giardia: Clinical Syndromes

After ingestion of G lamblia cysts, 5-15% of patients will have asymptomatic cyst passage, and 25-50% of patients will have diarrhea. From 35% to 70% of these patients will have no evidence of infection. The three manifestations of infection include asymptomatic cyst passage, self-limited diarrhea, and chronic diarrhea with associated malabsorption and weight loss. Factors related to each of these manifestations are unknown but are believed to be related to specific host factors, parasite load, and virulence variation among G lamblia isolates. 1. ACUTE GIARDIASIS Clinical Findings A. Signs and Symptoms. After ingestion of cysts, an incubation period of 3-20 days exists before symptom onset. At the time of presentation, patients …

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Cryptosporidium, Cyclospora, & Isospora Species & Microsporidia

Within the last decade, the AIDS epidemic has heightened awareness of several gastrointestinal spore-forming protozoan pathogens. The genera Cryptosporidium, Isospora, and Cyclospora are members of the subclass Coccidia and phylum Apicomplexa; the microsporidia are a group of organisms belonging to the phylum Microspora. The spectrum of disease caused by these protozoans goes beyond gastrointestinal manifestations, and the significance of these protozoan infections is becoming increasingly appreciated in both immunocompromised and immunocompetent hosts. CRYPTOSPORIDIUM Essentials of Diagnosis • Key signs and symptoms include dehydration with watery diarrhea of variable quantity. • Waterborne transmission is the most common mode of oocyst transmission. • Patients at risk for person-to-person transmission include household contacts, sexual …

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Pathogenic Amebas

ENTAMOEBA HISTOLYTICA & ENTAMOEBA DISPAR Essentials of Diagnosis Patient living in or having traveled to endemic area increases risk. Frequent loose stools with blood and mucus. Demonstration of cyst or trophozoite on stool wet mount or in biopsy specimen. Serology positive within 7-10 days of infection, may remain positive for years after infection resolved. Monoclonal antibodies and polymerase chain reaction emerging; may help differentiate E histolytica and E dispar. General Considerations A. Epidemiology. There are numerous distinct species of ameba within the genus Entamoeba, and the majority of these do not cause disease in humans. E histolytica is a pathogenic species that is capable of causing disease, such as colitis or …

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Intestinal Disease

Clinical Findings A. Signs and Symptoms. Of patients infected with E histolytica, > 90% are asymptomatic carriers who are colonized with the organism and pass cysts in the stool. This carrier state often resolves without treatment, although relapses and reinfection are common. Acute amebic colitis usually presents with several weeks of lower abdominal pain and diarrhea with frequent loose to watery stools containing blood and mucus. Most patients are afebrile. Significant volume depletion is uncommon. Chronic amebic colitis is characterized by low-grade inflammation resulting in intermittent bloody diarrhea and abdominal pain over a period of months to years. It is often difficult to distinguish chronic disease from inflammatory bowel disease, and …

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