Tags: Bites

Tissue Nematode Infections

LYMPHATIC FILARIASIS Lymphatic filariasis is a bloodstream and lymphatic infection caused by the filarial nematodes Wuchereria bancrofti, Brugia malayi, and Brugia timori. The disease is endemic in the tropics and subtropics of both hemispheres. A mosquito serves as an intermediate host and vector; the peak blood parasitemia and optimum time of the day or night for obtaining blood smears differ in various parts of the world, corresponding to the feeding pattern of the local mosquito vectors. After deposition by mosquitoes of infectious microfilariae into humans during a blood meal, 6-12 mo are required before adult worms mature and begin producing numerous circulating microfilariae to continue the life cycle. Symptoms of acute …

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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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Blastomyces Dermatitidis (Blastomycosis)

Essentials of Diagnosis Round thick-walled yeast with broad-based budding. Dimorphic: mycelial in nature, yeast in tissue. Associated with activities in proximity to waterways. Associated with exposure to dust, eg excavation. Endemic in states surrounding the Mississippi and Ohio Rivers. Pyogranulomas on histopathological examination. Acute or chronic infection of lung, skin, bone, or genitourinary tract. Recovery of microorganism from culture of tissue. General Considerations A. Epidemiology. Blastomyces dermatitidis is an endemic fungus that causes acute and chronic infections in humans and other animals. It is found primarily in the south central, southeastern, and midwestern United States, especially in the states surrounding the Mississippi and Ohio Rivers. Outside the United States, cases have …

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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 …

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Lyme Disease

Essentials of Diagnosis Most common in the northeastern, upper midwestern, and western parts of the United States. Borrelia burgdorferi is the longest (20-30 um) and narrowest (0.2-0.3 um) spirochete member of the Borrelia genus and has the fewest flagella (7-11). Erythema migrans (EM) is a red expanding lesion with central clearing that is commonly seen during the early stage of Lyme disease. The most common systems affected are the skin (EM), the joints (arthritis), the CNS (facial palsy), and the heart (conduction defects). Serology is not standardized; it is insensitive in early infection and does not distinguish active from inactive infection. Grows in Barbour-Stoenner-Kelly medium from skin biopsy and other specimens. …

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Nocardia

Essentials of Diagnosis Gram-positive, variably acid-fast, branching filaments with aerial hyphae. Colonies have characteristic chalky-white or cotton ball appearance. Suspect when chronic pulmonary disease is accompanied by CNS or skin lesions. No specific antibody or antigen detection tests. General Considerations A. Epidemiology. Nocardia spp. are strictly aerobic, ubiquitous soil-dwelling organisms that are largely responsible for the decomposition of organic plant material. Infection usually occurs via inhalation of these organisms in airborne dust particles, leading to pulmonary disease. However, infection can also be acquired via direct percutaneous inoculation by thorns, animal scratches, bites, surgical wounds, and intravenous catheters. Dissemination commonly occurs to the central nervous system (CNS), skin, and subcutaneous tissues. Nocardiosis …

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Pasteurella

Essentials of Diagnosis • History of a cat or dog bite or other exposure. • Pain, erythema, swelling, and drainage at the bite site. • Gram-negative bipolar bacilli on Gram stain of the drainage. • Culture of the organism confirms the diagnosis. General Considerations Pasteurella multocida infection, a disease that primarily affects animals, may occasionally affect humans, causing a wide variety of infections ranging from soft tissue infection to bacteremia and endocarditis. A. Epidemiology. Pasteurella multocida has been recovered from cultures of specimens from the nasopharynx and the gastrointestinal tract of a large number of asymptomatic wild and domestic animals. The highest carriage rates occur in cats (50%-90%), dogs or swine …

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Important Anaerobes: Clinical Syndromes

Box 1 summarizes different clinical syndromes associated with anaerobic bacteria. The sections that follow describe the various syndromes, including clinical findings. For some syndromes, specific diagnosis and treatment information is included as well. For other syndromes, see summary diagnosis and treatment sections at the end of the chapter. HEAD & NECK 1. EAR & PARANASAL SINUSES The flora in as many as two-thirds of chronic sinusitis and otitis cases includes B fragilis, Prevotella spp., Peptostreptococcus spp., and Porphyromonas spp. It is not surprising that ~50% of patients with chronic otitis media are infected with anaerobic bacteria, B fragilis being the most common. Mastoiditis may arise as a complication in some of …

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Diphtheria

Essentials of Diagnosis • Mildly painful tonsillitis/pharyngitis with associated membrane, cervical adenopathy, and signs of systemic toxicity; “bull neck” appearance. • Hoarseness and stridor. • Palatal paralysis. General Considerations A. Epidemiology. Humans are the only known natural hosts for C diphtheriae, the organism that causes diphtheria. This organism is usually spread via upper respiratory tract droplets, but it can also be spread by direct contact with skin lesions. Transmission appears to be more common when people are living indoors in crowded conditions. Disease is transmitted by those incubating the disease, those convalescing from infection, and also healthy carriers. The organism itself can survive for = 6 months in dust, which may …

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Streptococcus Pyogenes

Essentials of Diagnosis • Pharyngitis: presence of sore throat, submandibular adenopathy, fever, pharyngeal erythema, exudates. • Rheumatic fever: migratory arthritis, carditis, Syndenham’s chorea, pharyngitis. • Cellulitis: pink skin, fever, tenderness, swelling. • Scarlet fever: sandpaper-like erythema, strawberry tongue, streptococcal pharyngitis or skin infection, high fever. • Post-streptococcal glomerulonephritis: acute glomerulonephritis (hematuria, proteinuria) following pharyngitis or impetigo. • Impetigo: dry, crusted lesions of the skin, weeping golden-colored fluid. • Erysipelas: salmon red rash of face or extremity, well-demarcated border, fever, occasionally bullous lesions. • Streptococcal toxic shock syndrome: isolation of Group A streptococcus from a normally sterile site, sudden onset of shock and organ failure. • Necrotizing fasciitis, myonecrosis: deep, severe pain, …

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