Download Rocky Mountain Spotted Fever

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