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CHAPTER

Microbial Cardiovascular and

Systemic Diseases

Chapter Outline

Structures of the Cardiovascular System (p. 630)

Structure of the Heart

Movement of Blood and Lymph

Bacterial Cardiovascular and Systemic Diseases (pp. 630–644)

Septicemia, Bacteremia, and Toxemia

Endocarditis

Brucellosis

Tularemia

Viral Cardiovascular and Systemic Diseases (pp. 644–653)

Yellow Fever

Infectious Mononucleosis

Cytomegalovirus Disease

Dengue Fever and Dengue Hemorrhagic Fever

African Viral Hemorrhagic Fevers

Protozoan and Helminthic Cardiovascular and Systemic Diseases

(pp. 654–662)

Malaria

Toxoplasmosis

Chapter Summary

Structures of the Cardiovascular System (p. 630)

The heart, blood, and blood vessels comprise the cardiovascular system, which, along with the

lymphatic system, transports fluids throughout the body. Arteries carry blood away from the

heart to the lungs (via the pulmonary arteries) and to the rest of the body (via the aorta). They

Chapter 21 Microbial Cardiovascular and Systemic Diseases

connect via capillaries to veins, which carry blood back to the heart from the lungs

(via pulmonary veins) and from the rest of the body (via the superior and inferior venae cavae).

Structure of the Heart

The heart is composed of two parallel pumping chambers, each of which contains an upper atri-

um and a lower ventricle. They are separated by valves. The heart tissue is composed

of three layers: an outer fibrous pericardium, a muscular myocardium, and a thin inner

endocardium.

Movement of Blood and Lymph

Blood flows through the cardiovascular system in the following sequence: venae cavae, right

atrium, right atrioventricular (tricuspid) valve, right ventricle, pulmonary semilunar valve, pul-

monary arteries, lungs, pulmonary veins, left atrium, left atrioventricular (mitral) valve, left

ventricle, aortic semilunar valve, aorta, arteries, and capillaries.

Bacterial Cardiovascular and Systemic Diseases (pp. 630–644)

Bacteria can infect the blood as well as the blood vessels and heart.

Septicemia, Bacteremia, and Toxemia

Septicemia refers to the presence of a microbial infection of the blood that causes illness. Bac-

teremia refers specifically to bacterial septicemia; however, some physicians use the terms bac-

teremia and septicemia interchangeably. When bacteria remain fixed at a site of infection but

release toxins into the blood, the condition is called toxemia. When septicemia causes inflam-

mation of the lymphatic vessels, lymphangitis may result.

Septicemia is characterized by fever, chills, nausea, vomiting, diarrhea, shortness of breath,

malaise, and changes in mental status. These signs and symptoms can progress rapidly to septic

The various bacteria capable of causing septicemia or toxemia have one or more virulence

factors permitting them to survive and cause damage. They include the presence of resistance

capsule, the use of siderophores, production of hemolysins, or the presence of endotoxins. Many

of the bacteria responsible are opportunistic members of the microbiota when the

bacteria are directly inoculated into the blood.

Gram-negative bacteria are more likely to cause severe septicemia because their endotoxin

Endocarditis

Bacterial colonization of the endocardium triggers an inflammatory condition called

endocarditis and the formation of vegetations, masses of platelets and clotting proteins that

bury the bacteria, hiding them from defensive cells, antibodies, and antimicrobial drugs.

Signs and symptoms of endocarditis include fever, fatigue, malaise, difficulty breathing,

tachycardia, and murmurs. These signs and symptoms may develop over a period of weeks

or months (subacute endocarditis), or they may develop quickly (acute endocarditis).

About half of all cases of endocarditis are caused by the viridans streptococci, but dozens of

Brucellosis

Infection with Brucella melitensis—a small, nonmotile, aerobic Gram-negative coccobacillus—

causes the zoonosis brucellosis also known as Bang’s disease. The classic symptom is a fluctu-

ating fever that spikes every afternoon, giving the disease one of its common names, undulant

fever. The patient also has chills, sweating, headache, myalgia, and weight loss. Humans be-

come infected either by consuming unpasteurized contaminated dairy products

or through contact with animal blood, urine, or placentas. The bacteria enter the body through

Chapter 21 Microbial Cardiovascular and Systemic Diseases

Tularemia

Another small, nonmotile, aerobic Gram-negative coccobacillus, Francisella tularensis, causes

tularemia, a zoonotic disease transmissible to humans. Signs and symptoms are

typical of many viral infections and include fever, chills, headache, malaise, fatigue, shortness

of breath, joint stiffness, and myalgia. Lymph nodes may be swollen, and lymphangitis usually

is present. The bacterium lives in animals and in blood-sucking ticks and insects and is usually

Plague

Plague (also called bubonic plague or the “black death”) is caused by the bacillus Yersinia pes-

tis. Its classic symptom is the sudden appearance of painfully inflamed lymph nodes called bu-

boes. Other symptoms include fever, chills, malaise, muscular pain, severe headache,

bacteremia, and septicemia. DIC can accompany the condition, leading to blackened skin.

Pneumonic plague occurs when the plague bacilli spread from the bloodstream to the lungs or

are inhaled.

Lyme Disease

The bite of an Ixodes tick carrying the spirochete Borrelia burgdorferi causes the zoonosis

nous treatment depending on its severity. No vaccine is currently available.

Erlichiosis and Anaplasmosis

The Gram-negative rickettsial bacteria Erlichia chaffeensis and Anaplasma phagocytophilum

(formerly known as Ehrlichia equi) can be transmitted to humans by various hard-shelled ticks,

Instructor’s Manual for Microbiology with Diseases by Body System, 5e

causing erlichiosis (human monocytic erlichiosis, HME) and anaplasmosis (human granulo-

Viral Cardiovascular and Systemic Diseases (pp. 644–653)

Many viral diseases spread throughout the body via the lymphatic and cardiovascular

systems. Virus infection of the blood is called viremia.

Yellow Fever

Yellow fever is carried by Aedes aegypti mosquitoes, which feed on humans. After a bite from

an infected mosquito, the virus travels to the liver. Signs and symptoms develop within three to

six days and may follow three stages: The earliest stage is a few days of mild fever, headache,

Infectious Mononucleosis

Infectious mononucleosis (kissing disease, mono) results from infection with human

herpesvirus 4 (HHV-4), which is also known as Epstein-Barr virus (EBV). The characteristics

are severe sore throat and fever with enlarged lymph nodes, splenomegaly (enlarged spleen), ex-

treme fatigue, nausea, loss of appetite, headache, and a skin rash anywhere on the body. This

Cytomegalovirus Disease

Another herpesvirus that affects humans is Cytomegalovirus (CMV), an enveloped, dsDNA vi-

rus that causes infected cells to become enlarged. CMV typically remains latent unless the im-

mune system is compromised; however, in fetuses, newborns, and immunocompromised

patients, infection can cause an enlarged liver and spleen, jaundice, anemia, deafness,

blindness, pneumonia, and even death. CMV may also be teratogenic. Transmission is

typically via sexual intercourse, in utero exposure, vaginal birth, blood transfusions, or organ

transplants. Abnormally enlarged cells with nuclear inclusions are diagnostic; ELISA and DNA

probes can verify the presence of virus. Treatment of fetuses and newborns is difficult because

Chapter 21 Microbial Cardiovascular and Systemic Diseases

Dengue Fever and Dengue Hemorrhagic Fever

Dengue fever is caused by four antigenically distinct dengue viruses, enveloped +ssRNA

viruses in the genus Flavivirus. They are carried by Aedes mosquitoes and infect millions

of people worldwide each year. The bite of an infected mosquito causes dengue fever

African Viral Hemorrhagic Fevers

Ebola hemorrhagic fever, which is caused by Ebolavirus, and Marburg hemorrhagic

fever, which is caused by Marburgvirus, are endemic to Africa and are emerging global health

concerns. Both begin with fever, fatigue, dizziness, muscle pain, and exhaustion,

followed by minor petechiae. This progresses to severe bleeding internally and from body

Protozoan and Helminthic Cardiovascular and Systemic

Diseases (pp. 660–667)

Of the many protozoan and helminthic cardiovascular and systemic diseases, the most

prevalent and serious is malaria.

Malaria

Malaria is caused by four species of the genus Plasmodium, which is transmitted by

Anopheles mosquitoes to millions of people each year.

The life cycle of Plasmodium has three stages. (1) In the exoerythrocytic cycle, Plasmodium

sporozoites injected by a female Anopheles mosquito infect the host’s liver. (2) In the erythro-

Instructor’s Manual for Microbiology with Diseases by Body System, 5e

The protozoa infect the liver and erythrocytes, causing jaundice, severe recurrent fever and

chills, headache, vomiting, and diarrhea. Worldwide, two to three million people die each year

from malaria. If a victim survives the acute stages, immunity gradually develops, and periodic

episodes become less severe.

Observation of parasites in blood smears is diagnostic. Malaria is treated with standard anti-

Toxoplasmosis

The apicomplexan protozoan Toxoplasma gondii causes toxoplasmosis (toxo), a major

disease of AIDS patients and unborn children.

Over 80% of infected people have no symptoms; however, infection in immunocompromised

patients can result in fever, malaise, and inflammation of the lungs, liver, and heart. Headache,

confusion, spastic paralysis, blindness, myocarditis, encephalitis, and death are also common.

Transplacental transfer from mother to fetus can cause a variety of birth defects (epilepsy, men-

American Trypanosomiasis (Chagas’ Disease)

Chagas’ disease is endemic throughout Central and South America. Initial symptoms, which

are experienced by only 1% of infected people, are swelling at the site of infection, followed by

fatigue, fever, malaise, and swollen lymph nodes for four to eight weeks. The disease then enters

asymptomatic stage for 10–20 years. In some patients, this is followed by a symptomatic stage

characterized by fatal congestive heart failure following the formation of pseudocysts, which are

clusters of the parasite in heart muscle tissue.

The flagellated protozoan Trypanosoma cruzi causes Chagas’ disease. Most mammals

can be host to the parasite though opossums and armadillos are the primary reservoirs. Trans-

Chapter 21 Microbial Cardiovascular and Systemic Diseases

Schistosomiasis

Parasitic blood flukes of the genus Schistosoma are among the most common parasitic

helminths in the world. They cause schistosomiasis, a potentially fatal disease that manifests in-

itially as a transient dermatitis called swimmer’s itch where infective larvae burrow into