Gas gangrene

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