Transcript Chapter 19b
Chickenpox • Causative agent – Varicella-Zoster virus – Herpes virus • One of the most common rashes among children – More serious in adults • Signs& Symptoms – Skin rash appears on body trunk then spreads to face, neck and limbs • Rash is diagnostic • Itchy rash progresses from red spots to pus filled blisters that break and crust over – Viral incubation period approximately 2 weeks • Infective 1 to 2 days before rash until all blisters crust • Epidemiology – Disease transmitted by respiratory secretions and skin lesions – Virus typically enters through respiratory route, replicates and moves to the skin via blood stream – Infected cells swell and lyse • Release viruses which enter sensory nerves – Usually self limiting • Sequella – Shingles or herpes zoster – Reactivation of latent virus – Virus in nerve cell replicates and moves back to skin – Linked with decline in immunity • Age, stress – Diagnosed by antibody test • Prevention and treatment – Prevention directed at vaccination • Attenuated vaccine licensed in 1995 • Recommended for healthy individuals 12 months and older – Treatment is directed at alleviating symptoms • Acyclovir given in high risk cases – Reye’s Syndrome – Associated with a number of viral infections – Linked to aspirin usage in children – Characterized by vomiting and coma » Liver and brain damage – Mortality around 30% [INSERT DISEASE AT A GLANCE 19.7] Measles • Causative agent – Rubeola virus – paramyxovirus • Signs & Symptoms – Fever, runny nose, dry cough, conjunctivitis – Fine rash (maculopapular) • first on forehead – Koplik spots – Symptoms generally disappear within 1 week – May cause miscarriage and low birth weight • Epidemiology – Humans are only natural host – Virus spread by respiratory droplets – Replicates in epithelium of upper respiratory tract • 8-10 day incubation – Spreads to lymph becoming systemic – Typically self-limiting – Many cases complicated by secondary infections • Pneumonia and earaches – Rare complications • encephalitis and subacute sclerosing panencephalitis (SSPE) • persistent viral infection • Prevention and treatment – Prevention directed to vaccination • Vaccine is usually given in conjunction with mumps and rubella vaccine – MMR • Before routine immunization, over 99% of population infected • Measles are no longer endemic in US – No antiviral drug exists for rubeola infection • May treat with passive immunotherapy German Measles • Causative agent – Rubella virus – togavirus • Typically mild • Difficult to diagnose • Symptoms – – – – Slight fever with mild cold symptoms Enlarged lymph nodes behind ears and back of neck Faint rash (macules) Symptoms last only a few days • Significant infection in pregnant women – Congenital rubella syndrome – May result in blindness, deafness, heart defects, mental retardation and low birth weight – Fetal injury varies based on the time of infection • Epidemiology – Humans are only natural host – Virus spread by respiratory droplets – Multiplies in nasopharynx then enters blood – Disease is highly contagious • Infectious 7 days before appearance of rash and up to 7 days after it disappears • Prevention and treatment – Vaccination with attenuated rubella virus vaccine • Administered at 12 months and boostered at 4 to 6 years of age • Produces long-lasting immunity [INSERT TABLE 19.4] Warts • Causative agent: – Papillomavirus – Causes small tumors called papillomas (warts) – Typically benign • 50 different papillomaviruses known to infect humans – infect skin through minor abrasions – Direct, indirect or auto- inoculation – Viruses can survive on a number of fomites • Towels • Shower floors • Treatment involves killing abnormal cells – Freezing – Cauterization – Corrosive chemicals – Surgical removal – Laser Mycoses of the Integument • Most fungi are opportunistic pathogens • Mycoses classified by location – Superficial – hair, nails, and outer skin layers • most common – Cutaneous – in the skin – Subcutaneous – in the hypodermis and muscles – Systemic – affect numerous systems • Superficial Mycoses – Pityriasis versicolor • Caused by Malassezia furfur • Endogenous Pityriasis versicolor – Pathogenesis • Superficial fungi produce keratinase, which dissolves keratin – Diagnosis, treatment, and prevention • Identified by green color under ultraviolet light and treated with topical or oral drugs – Tolnaftate; Griseofulvin; Azoles • Cutaneous Mycoses – May manifest as cutaneous lesions – Dermatophytoses • Immune responses damage deeper tissues • Causative Agent – Genera responsible for most dermatophytoses • Epidermophyton • Microsporum • Trichophyton – Collectively termed dermatophytes Tinea capitis - scalp Tinea corporis – body (Ringworm) Tinea pedis foot (Athlete’s foot) [INSERT TABLE 19.5] – Excessive moisture allows invasion of keratinized tissue • Most dermatophytes produce keratinase – Scalp is invaded through hair follicle – Fungal products defuse to dermal layer and evoke an immune response • Treatment, and prevention – Attention to cleanliness – Maintenance of dryness – Treat limited infections with topical agents • Tolnaftate – Treat widespread infections with oral drugs • Griseofulvin; terbinafine