Chapter 25 - Microbial Diseases of the Cardiovascular and Lymphatic Systems

Cardiovascular system functions

Pumps blood around body; transports oxygen, carbon dioxide, nutrients, and waste

Cardiovascular system organs

heart, blood vessels, blood

Lymphatic system functions

defends against infection and disease, returns tissue fluids to the bloodstream

Lymphatic system organs

lymph nodes, lymphatic vessels, thymus, spleen, tonsils

Buboes

swollen lymph nodes

Septicemia

acute illness due to the presence of pathogens or their toxins in the blood

Sepsis

systemic inflammatory response

Lymphangitis

Infection and inflammation of the lymphatic vessels

Severe sepsis

decreased blood pressure and dysfunction of at least one organ

Septic shock

a serious condition that occurs when an overwhelming bacterial infection affects the body; sepsis and uncontrollable decrease in BP

Gram-negative sepsis

Endotoxins caused blood pressure decrease.

Antibiotics can worsen condition by killing bacteria.

Treatment: neutralize LPS and inflammatory-causing cytokines

Gram-negative sepsis bacteria

Klebsiella, E. coli, P. aeruginosa, Elizabethkingia

Gram-positive sepsis

potent exotoxins that cause toxic shock syndrome (fever, low BP, vomiting, rash); hospital acquired infections

Gram-positive sepsis bacteria

E. faecium and E. faecalis: normal colon microbiota that can colonize wounds and urinary tract; resistant to many antibiotics

Group B streptococci (S. agalactiae)

Puerperal sepsis

Caused by Streptococcus pyogenes; sometimes called childbirth fever; transmission from medical provider to mother during childbirth; infection of uterus leading to peritonitis and sepsis; Ignaz Semmelweis reduced incidence with handwashing

Endocarditis

inflammation of the lining of the heart

Subacute bacterial endocarditis

Impairs the function of the heart valves

Alpha-hemolytic streptococci from an oral or tonsil infection

Acute bacterial endocarditis

Caused by S. aureus; fever, weakness, heart murmur, damage to heart valves

Pericarditis

Streptococcal infection resulting in inflammation of the sac surrounding the heart

Rheumatic fever

Autoimmune disease of the heart that can damage heart valves and cause subcutaneous nodules at joints; complication of S. pyogenes infection resulting in an immune reaction to its M protein

Sydenham's chorea

A form of chorea (involuntary muscle twitching) associated with rheumatic fever

Tularemia cause and transmission

Cause: Francisella tularensis

Transmission: Zoonosis, rabbit reservoir; transmitted by rabbits, ticks or deer flies

Tularemia symptoms

Ulcer at entry site; reproduction of bacteria in phagocytes leads to regional lymph node swelling; respiratory infection can lead to pneumonia (mortality of <30%)

Brucellosis (Undulant Fever)

Caused by Brucella spp., aerobic gram-negative coccobacilli

Reservoirs: Elk, bison, cows (B. abortus), pigs (B. suis), goats, sheep, camels (B. melitensis); transmitted via milk or contact with infected animals

Causes undulant fever, malaise, night sweats, muscle aches

Anthrax cause

Bacillus anthracis - gram-positive endospore-forming aerobic rod found in soil; mainly affects grazing animals; spores introduced into body germinate and enter bloodstream

Anthrax treatment and prevention

Treated with ciprofloxacin or doxycycline

Prevented by vaccinating livestock

Anthrax virulence factors

Protective antigen binds toxin to target cells to aid in entry

Edema toxin causes local swelling and interferes with phagocytosis

Lethal toxin kills macrophages

Amino acid capsule avoids immune response

Cutaneous anthrax

Endospores enter through minor cut

20% mortality

Gastrointestinal anthrax

Ingestion of undercooked, contaminated food

50% mortality

Inhalation (pulmonary) anthrax

Inhalation of endospores

Bacteria enter the bloodstream; progresses into septic shock

Near 100% mortality rate

Ischemia

loss of blood supply to tissue

Necrosis

death of tissue

Gangrene

death of tissue associated with loss of blood supply

Gas gangrene

Necrosis in a wound infected by an anaerobic gas forming bacillus, the most common etiologic agent being Clostridium perfringens whose toxins move along muscle bundles

Treated with surgical removal of necrotic tissue and/or hyperbaric chamber

Pasteurella multocida

Organism most commonly associated with infections of animal bites and scratches; gram-negative rod; can cause sepsis

Cat-scratch disease

Caused by Bartonella henselae (aerobic gram-negative rod); inhabits cat RBCs and multiplies in cat flea GI tract; transmission often from cat claws contaminated with flea feces; cluster of small papules at the site of inoculation; lymph nodes swell; self-limiting

Streptobacillary rat-bite fever

Streptobacillary rat-bite fever

Found in North America

Caused by Streptobacillus moniliformis

Filamentous, gram-negative, pleomorphic, fastidious

Fever, chills, muscle pain; mortality rate of 10%

Spirillar fever

Caused by Spirillum minus

Similar to streptobacillary rat-bite fever

Plague cause

Yersinia pestis - gram-negative rod transmitted by rat flea (Xenopsylla cheopis) and endemic to rats, ground squirrels, and prairie dogs; blocks flea digestive tract, causing it to regurgitate ingested blood and bacteria into host; bacteria enter bloodstream of host and proliferate in lymph tissue resulting in buboes

Bubonic plague

Bacterial growth in the blood and lymph

Most common form; 50-75% mortality rate

Septicemic plague

septic shock due to bacteria in the blood

Pneumonic plague

Bacteria in the lungs

Easily spread by airborne droplets

Near 100% mortality rate

Relapsing fever

Caused by Borrelia spp. (spirochete)

Transmitted by soft ticks that feed on rodents

High fever, jaundice, rose-colored skin spots

Successive relapses are less severe

Treated with tetracycline

Lyme Disease cause and transmission

Cause: Borrelia burgdorferi

Transmitted by Ixodes tick

Field mice reservoir (nymph stage of tick feeds on mice and then infects humans)

Ticks feed on deer to complete reproductive cycle

Ticks must attach 2-3 days to transfer bacteria

Lyme Disease stages

First phase: Bull's-eye rash; flulike symptoms

Second phase: Irregular heartbeat; encephalitis; facial paralysis; memory loss

Third phase: Arthritis due to an immune response

Lyme Disease diagnosis and treatment

Diagnosis via ELISA, indirect fluorescent-antibody (FA) test, or Western blot

Treated with antibiotics; more difficult to treat in later stages

Human Monocytic Ehrlichiosis (HME)

Causative agent: Ehrlichia chaffeensis (gram-negative, rickettsia-like, obligately intracellular parasite); forms aggregates (morulae) in monocytes

Vector: lone Star tick

Reservoir: white-tailed deer

Symptoms: flu-like disease

Human granulocytic anaplasmosis (HGA)

Causative agent: Anaplasma phagocytophilum

Reservoir: deer

Vector: Ixodes ticks

Symptoms: flu-like disease

Typhus

Caused by Rickettsia spp. (obligate intracellular parasites); infect the endothelial cells of the vascular system and block and rupture the small blood vessels

Spread by arthropod vectors

Typhus fever (epidemic louseborne typhus)

Caused by Rickettsia prowazekii

Carried by the body louse: Pediculus humanus corporis

Transmitted when louse feces are rubbed into the bite wound from the louse

Prolonged fever and a rash of red spots due to subcutaneous hemorrhaging

Treated with tetracycline and chloramphenicol

Endemic murine typhus

Caused by Rickettsia typhi

Transmitted by the rat flea: X. cheopis

Rodents are common hosts

Mortality less than 5%

Clinically indistinguishable from typhus fever

Treated with tetracycline and chloramphenicol

Rocky Mountain Spotted Fever

Caused by Rickettsia rickettsii

Spread by wood ticks (Dermacentor andersoni) and dog ticks (Dermacentor variabilis)

Measles-like rash, except that the rash also appears on the palms and soles

Without early diagnosis, mortality rate is approximately 20%

Treatment with tetracycline and chloramphenicol

Burkitt's lymphoma

Tumor the of jaw; most common childhood cancer in Africa

Due to Epstein-Barr virus (human herpesvirus 4)

Malaria suppresses the immune system response to the virus

Infectious mononucleosis

Caused by Epstein-Barr virus

Transmitted via saliva; incubation of 4 to 7 weeks

Symptoms: fever, sore throat, swollen lymph nodes, enlarged spleen; childhood infections are often asymptomatic

Replicates in resting memory B cells; form unusual lobed nuclei; produce heterophile antibodies that are weak and multispecific

Epstein-Barr virus diseases

Burkitt's lymphoma, infectious mononucleosis, multiple sclerosis (autoimmune disease of nervous system), Hodgkin's lymphoma (tumors of spleen, lymph nodes, liver), nasopharyngeal cancer

Cytomegalovirus (CMV)

Human herpesvirus 5; latent infection in WBCs causes cells to swell (owl's eyes inclusions); Mild symptoms or asymptomatic in adults

Cytomegalic inclusion disease (CID): transmitted via placenta to fetus causing mental retardation or hearing loss

Transmitted sexually, via blood, saliva, or tissue transplant

Chikungunya fever

Caused by the Chikungunya virus (related to viruses causing western and eastern equine

encephalitis

Transmitted by Aedes mosquitoes

Symptoms: high fever, severe joint pain, rash, blisters – Low death rate

Introduced to the Western Hemisphere in 2013

– More than 1.7 million cases in the Caribbean

– Could soon become established in the United States due to the presence of the vector; locally-acquired cases have occurred in Florida and Texas

Aedes albopictus

Asian tiger mosquito; feeds all day; vector for chikungunya; moving north into US as climate changes

Yellow fever

Aedes aegypti vector

Symptoms: fever, chills, headache, nausea, vomiting, liver damage and jaundice

Endemic in tropical areas

No treatment

Attenuated vaccine

Dengue fever

Aedes aegypti mosquito vector

Endemic to Caribbean and tropical areas

Symptoms: asymptomatic to mild symptoms; severe form causes severe bleeding and organ impairment; antibody enhancement may occur

No animal reservoir, no vaccine, no effective treatment

Antibody enhancement

Antibodies from previous infections help new infection gain access to host cells; seen in dengue fever

Marburg virus (green monkey virus)

-Transmitted from African monkeys

-Headache, high fever, vomiting blood, profuse bleeding internally and externally

Lassa fever

-Arenavirus; found in rodent urine

-Found in West Africa

-Similar to Argentine and Bolivian hemorrhagic fevers (South America) and Whitewater Arroyo virus (California)

Ebola virus disease (EVD)

Caused by Ebolavirus (filovirus similar to Marburg)

Reservoir: cave-dwelling fruit bat

Transmission: contact with body fluids

Symptoms: hemorrhaging due to damage to blood vessel wall and decreased coagulation

Mortality rate of 90%

Recombinant vaccine available

Hantavirus Pulmonary Syndrome

- Caused by the Sin Nombre virus

- Fatal pulmonary infection; lungs fill with fluids

- Found in the western United States

Hemorrhagic fever with renal syndrome

Hantavirus infection

Found in Asia and Europe

Affects kidney function

Chagas' Disease (American Trypanosomiasis)

Caused by Trypanosoma cruzi (Flagellated protozoan

Reservoir in rodents, opossums, and armadillos

Vector: reduviid bug (kissing bug); defecates trypanosomes into the bite wound of humans

Chronic form of the disease causes megaesophagus and megacolon

(Death due to heart damage)

Therapy is difficult due to parasite multiplying intracellularly

Toxoplasmosis

Caused by Toxoplasma gondii

Sexual phase in cat intestines, oocysts shed in cat feces

Oocysts transmitted to humans by contact with cat feces or undercooked meat; trophozoites invade cells and may cause chronic infection

Congenital infection: stillbirth and neurological damage

Malaria cause and transmission

Causative agent: Plasmodium spp.

Vector: Anopheles mosquitoes

Plasmodium vivax

mildest and most prevalent form; dormant in the liver

Plasmodium ovale and Plasmodium malariae

benign; restricted geographically

Plasmodium falciparum

most deadly; severe anemia; blocks capillaries; affects the kidneys, liver, and brain

Malaria life cycle

-Mosquito bites human and has sporozoite in salivary glands

-Sporozoites spread via blood to the liver and undergo schizogony and mature to become merozoites, which spread into RBC

-Merozoites undergo schizogony in RBC (ring form), once RBC is too full, it lyses and the plasmodium spreads to other RBCs

-Some of the merozoites can also develop into gametocytes which will be picked up by the mosquito when it bites an infected individual to spread to others

-Sexual reproduction occurs in mosquito

Malaria Diagnosis, treatment, and prevention

Diagnosis made by identifying merozoites/ring stage in blood

No vaccine: rapid mutation and immune evasion

Prophylaxis: chloroquine; malarone for resistant strains

Treatment: artemisinin

Prevention: vector control, bed nets

Leishmaniasis

Transmitted via female sandflies

Promastigote transmitted in saliva from bites Amastigote proliferates in phagocytic cells

Visceral Leishmaniasis

Leishmania donovani infection of internal organs

Cutaneous Leishmaniasis

Leishmania tropica infection resulting in papule that ulcerates and leaves a scar

Mucocutaneous Leishmaniasis

Leishmania braziliensis infection that affects mucous membranes

Babesiosis

-Caused by Babesia microti

-Carried by Ixodes ticks

-Resembles malaria (Parasites replicate in RBCs and cause fever, chills, and night sweats)

-Treated with atovaquone and azithromycin

Schistosomiasis

Caused by Schistosoma flukes; feces contaminated with eggs enter water supply and infect snails as intermediate host; cercariae released form snails penetrate skin of human host; adult schistosomes in host release eggs that lodge in tissues and form granulomas

Schistosoma haematobium

urinary schistosomiasis

Schistosoma japonicum

intestinal inflammation; found in Asia

Schistosoma mansoni

intestinal inflammation; found in South America

Kawasaki syndrome

Acute febrile illness of unknown etiology

Most often affects younger children

High fever, widespread rash, hand and feet swelling, swollen lymph glands

Treated with aspirin

Possible immunological cause