Tags: Encephalitis

Nematodes

Essentials of Diagnosis Intestinal nematodes: demonstration of characteristic eggs or parasites in stool. Bloodstream nematodes (filariasis): clinical diagnosis can be made; fresh blood smear may be confirmatory. Tissue nematodes: clinical diagnosis can be made; skin snip or other tissue examination may show organism. General Considerations Nematodes (roundworms) are nonsegmented, tapered, bilaterally symmetrical, cylindrical organisms that have complete digestive tracts and reproduce sexually. Although > 500,000 species of nematodes have been described, only a small number are commonly encountered as human parasites. Most nematodes have complex life cycles, sometimes involving several larval forms and intermediate hosts or free-living stages. The pathogenic nematodes may be categorized as primarily intestinal or extraintestinal tissue parasites …

Continue Reading...

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, …

Continue Reading...

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 …

Continue Reading...

Toxoplasma Gondii

General Considerations A. Epidemiology. Toxoplasma gondii infection, or toxoplasmosis, is a zoonosis (the definitive hosts are members of the cat family). The two most common routes of infection in humans are by oral ingestion of the parasite and by transplacental (congenital) transmission to the fetus. Ingestion of undercooked or raw meat that contains cysts or of water or food contaminated with oocysts results in acute infection. In humans, the prevalence of toxoplasmosis increases with age. There are also considerable geographic differences in prevalence rates (eg, 10% in Palo Alto, CA; 15% in Boston, MA; 30% in Birmingham, AL; 70% in France; = 90% in El Salvador). Differences in the epidemiology of …

Continue Reading...

Toxoplasma Gondii: Clinical Findings

Primary infection in any host often goes unrecognized. In ~ 10% of immunocompetent individuals, it causes a self-limited and nonspecific illness that rarely requires treatment. The most frequently observed clinical manifestation in this setting is lymphadenopathy and fatigue without fever; other manifestations include chorioretinitis, myocarditis, and polymyositis (Box 1). Reinfection occurs but does not appear to result in clinically apparent disease. In contrast to the usually benign course of the initial infection in immunologically intact hosts, the congenitally infected fetus and newborn and immunocompromised patients are at high risk for severe or life-threatening disease caused by this parasite. Congenital toxoplasmosis is the result of maternal infection acquired during gestation. Among immunologically …

Continue Reading...

Cryptococcus Neoformans

Essentials of Diagnosis Routine laboratory tests often normal. One-third of patients are afebrile. Definitive diagnosis made by fungal culture maintained at 37°C for 6 weeks. Cryptococcal antigen 95% sensitive in CNS infection in centrifuged CSF. India ink examination positive in only 50% of meningoencephalitis cases. CSF lymphocytes often low in CNS infection, especially in AIDS patients. Cryptococcal antigen most sensitive detection method in serum. Chest radiograph variable — multiple areas of infiltration in lower lobes most common in pulmonary disease. Molecular detection by PCR might soon become laboratory standard. General Considerations A. Epidemiology and Ecology. Cryptococcus neoformans exists as two distinct varieties known as variety neoformans and variety gattii (Table 1). …

Continue Reading...

Histoplasma Capsulatum

Essentials of Diagnosis Thin-walled oval yeast measuring 2-4 mm in diameter. Dimorphic: mycelial in nature, yeast in tissue. Endemic within Ohio and Mississippi River Valleys. Associated with activities that disturb dust or soil enriched with bird, chicken, and bat excrement. Complement fixation antibody titer 1:32 or greater. Simultaneous appearance of anti-H and anti-M antibodies. Infection most often is asymptomatic or may cause chronic pulmonary infection; less commonly, disseminated infection involving the adrenals, ulcerative gastroenteritis lesions, or central nervous system. Recovery of organism from culture of tissue, blood, sputum, or other source. General Considerations A. Epidemiology. Histoplasma capsulatum, the etiologic agent of histoplasmosis, is an endemic, dimorphic fungus that causes a wide …

Continue Reading...

Rocky Mountain Spotted Fever (RMSF)

Essentials of Diagnosis Key symptoms and signs: abrupt onset of high fevers, headaches, myalgias, malaise, and a flu-like illness 3-12 days after tick bite; rash (80-90% of patients, initially maculopapular, then petechial, classically involving the palms and soles). Predisposing factors: tick exposure (April through September), pet owners, animal handlers, and outdoor activities. Commonest geographic location of infection: rural. Confirmatory serology via IFA. PCR with blood or skin biopsy: sensitive and specific but not widely available. General Considerations RMSF is caused by Rickettsia rickettsii and is an acute tick-borne illness occurring during seasonal tick activity. The disease is characterized by acute onset of fever, headache, and a rash of the extremities spreading …

Continue Reading...

Coxiella, Ehrlichia, & Rickettsia

Coxiella, Ehrlichia, and Rickettsia spp. are small, obligate intracellular bacteria that usually cause disease when they accidentally encounter a human host. Once inside a host cell, Coxiella and Ehrlichia spp. remain within a vacuole where they progress through distinct developmental stages; in contrast, the Rickettsia spp. escape the endocytic vacuole and replicate within the host cell cytoplasm. Ehrlichia and Rickettsia spp. are transmitted by arthropod vectors. COXIELLA BURNETII INFECTION (Q FEVER) Essentials of Diagnosis Acute Infection Key symptoms and signs: fever, severe headache, myalgias, arthralgias, retrobulbar pain, cough; possible pneumonitis and hepatitis on examination. Predisposing factors: occupation as a dairy farmer, abattoir worker, or veterinarian; exposure to parturient or newborn animals, …

Continue Reading...

Chlamydia

General Considerations Chlamydia trachomatis, Chlamydia psittaci, and Chlamydia pneumoniae are among the most prevalent microbial pathogens in humans worldwide. C trachomatis is responsible for a variety of sexually transmitted disease (STD) syndromes in both sexes. In addition, certain serotypes of C trachomatis are responsible for trachoma, the most common infectious cause of blindness in humans. C psittaci is a zoonotic pathogen associated with atypical pneumonia. C pneumoniae infects approximately one-half of the world’s human population and is a cause of upper and lower respiratory tract disease. It has also been associated with atherosclerotic cardiovascular disease. A. Epidemiology. In the United States, genital infections by C trachomatis serovars D through K occur …

Continue Reading...
CLOSE
CLOSE