Post on 11-May-2015
Ch 21Gas Gangrene
• Epidemiology–
– War wounds; dirt contamination of wounds, tissue death, impaired circulation in patients with poor circulation
– Common after:
– Arteriosclerosis, diabetes predispose
– 40% mortality (with therapeutic care)
• Prevention and treatment– Prompt cleaning of wounds is:
–
– Surgical removal of dead and infected tissues
– Treatment with hyperbaric oxygen, antitoxin
– Penicillin to kill vegetative C. perfringens
Ch 21Plague
• Symptoms– Sudden onset of high fever, large lymph nodes (buboes), skin
hemorrhages, severe cough, bloody and frothy sputum
• Pathogen – Yersinia pestis– Capsulated bacterium, multiple virulence factors – Virulence factors:
• • •
• Pathogenesis– Y. pestis contracted from bite of infected flea– Survive phagocytosis and infect lymph nodes →
– May be carried into bloodstream → – Hemorrhages under skin result in dark patches, skin color– Lung infection → contagious, lethal pnuemonic plague →
Ch 21Transmission of Yersinia pestis
Ch 21Yersinia pestis
Ch 21Plague
• Epidemiology– Endemic in wild animals and fleas
– Rare but
– Transmitted person to person via fleas
– Pneumonic plague: coughing –
• Prevention and treatment– Vaccine offers short-term protection
– Avoid contact with wild rodents
– Insecticides and rat control
– to prevent high mortality
Ch 21Lyme Disease – Phases
Phase 1:
• Erythema migrans characteristic rash present – 80% of cases
• Malaise; chills; fever; headache; stiff neck; joint and muscle pain; backache
Phase 2:
• Cardiac dysfunction
• Neurological symptoms (meningitis, encephalitis, peripheral nerve neuropathy
Phase 3:
• Arthritis; joint pain, tenderness, swelling
• Chronic nervous system impairments
Ch 21Lyme Disease – Borrelia burgdorferi
Ch 21Lyme Disease
• Causative Agent– Borrelia burgdorferi – microaerophilic
spirochete
• Pathogenesis– Spirochetes injected into skin:– Multiply → – Tissue damage result of immune response
Ch 21The life cycle of Ixodes
Ch 21Ixodes scapularis – Black-legged tick
Ch 21Lyme Disease
• Epidemiology– – Increased prevalence – encroachment on wooded
areas; increase in deer populations– Spread by infected tick bite – – Ixodes – preferred host: white-footed mouse, white-
tailed deer
• Prevention and Treatment– Prevent by:
– Antibiotics are effective:• Penicillin, doxycycline
– Prolonged antibiotics late in infection may be curative
Ch 21Lyme disease in the U.S.
Ch 21
Viral infections of the cardiovascular system
Ch 21Mononucleosis
• Symptoms– Fatigue, fever, sore throat, lymph node enlargement
– Most people return to school/ work:
• Causative agent – Epstein-Barr virus (EBV)– dsDNA virus, herpesvirus family
– Isolated from Burkitt’s lymphoma
• Pathogenesis– Virus enters throat →
– Infection of B cells →
– Hemorrhage of spleen is rare but serious complication
– May play role in causing malignant tumors –
Ch 21Diseases associated with Epstein-Barr virus
Ch 21Mononucleosis
• Epidemiology
– Spread in:
– Kissing is common mode of transmission
– Lifelong recurrent shedding of virus in saliva
– Very common in college students
–
• Prevention and treatment
– Avoid sharing items contaminated by saliva
–
–
– Acyclovir beneficial in some cases
Ch 21Viral Hemorrhagic Fevers
•
• Signs and symptoms – Fever, fatigue, dizziness, muscle pain, exhaustion– Minor petechiae
– Severe internal hemorrhaging and bleeding from mouth, eyes and ears
– Death from:
• Pathogens – ssRNA viruses – Filoviridae family– Enveloped, filamentous virus
• Pathogenesis– Hemorrhaging due to malfunction of blood clotting system
– Infected macrophages trigger localized blood clotting →
Ch 21Viral Hemorrhagic Fevers
• Epidemiology– Primarily in Africa– No human carriers but natural animal
hosts– Transmission through:
– Airborne?– Ebola – 90% fatal– Marburg – 25% fatal
• Prevention and Treatment– –
– No effective antiviral drugs– Currently no vaccine for humans
Ebola virus
Ch 21Some viral hemorrhagic fevers
Ch 21Sites of Marburg and Ebola virus epidemics