Chapter 23
Cardiovascular, Lymphatic, and Systemic Infectious Diseases
23.1 The Structure of the Cardiovascular and Lymphatic Systems
• The cardiovascular system is composed of the pulmonary and systemic circulation
• The lymphatic system absorbs, transports, and filters lymph and initiates an
immune response
23.2 Circulatory System Diseases Caused by Bacteria and Helminthic Parasites
• Several bacterial species and a few helminthic parasites infect the human
circulatory or lymphatic systems
• Septicemia is a bacterial infection of the bloodstream
• Lymphangitis is an infection of the lymphatic system
• Sepsis and septic shock can trigger a state of physiological collapse
• Infective endocarditis affects the endocardium and heart valves
• It can be an acute or subacute disease
• Streptococcal infections also affect the cardiovascular system
• Puerperal fever
• Neonatal sepsis
• Rheumatic fever
• Helminthic parasites also infect the circulatory system or cause an
inflammation in lymphatic vessels
• Schistosomiasis is caused by several species of blood flukes
(Phylum Schistosoma)
• Eggs can cause damage in the
– liver
– intestines
– Bladder
• Miracidia in snails convert to cercariae, which leave the snail and attach to human
skin
• They infect the blood and mature, causing fever and chills
• Filariasis is caused by Wuchereria bancrofti
• It is transmitted by mosquitoes
• Larvae infect the lymphatic system
– They damage vessels and glands
• After years of infestation, arms, legs, and scrotum swell and distort
– a.k.a. elephantiasis, lymphedema
23.3 Systemic Bacterial Diseases
• Plague is caused by Yersinia pestis
• It is transmitted between hosts by the oriental rat flea
• Bacteria localize in the lymph nodes, in which hemorrhaging can occur
• This is how buboes form
• Bacilli can spread to the bloodstream from the lymph nodes, causing
• septicemic plague
• plague meningitis
• Septicemic cases can progress to the lungs (pneumonic plague)
• This allows human-human transmission through respiratory
droplets to occur
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• When plague is detected early, antibiotics can be used
• A vaccine is available to high-risk groups
Tularemia Has More Than One Disease Presentation
• Francisells tularensis, an extremely virulent bacillus, causes tularemia
• It is common in rabbits, other rodents and animals
• Humans can acquire it via:
• arthropods from animal fur
(particularly ticks)
• inhaling or consuming bacilli
• splashing in the eye
Transmission via arthropod bite leads to
• swollen lymph glands
• flu-like symptoms
• skin ulceration
Inhalation tularemia leads to
• respiratory disease
• swollen lymph nodes
• coughing
• pain under the breastbone
Lyme Disease Can Be Divided into Three Stages
• Lyme disease is one of the major emerging infectious diseases in the
United States
• It is caused by Borrelia burgdorferi
• It is usually transmitted by ticks
• Ticks defecate into the wound they create during feeding
• The early localized stage involves a slowly expanding red rash (erythema
migrans) at the bite site
• The rash resembles a bull’s-eye
• The rash is usually accompanied by flu-like symptoms
• The early disseminated stage of Lyme disease begins weeks to months
later
• Bacteria disseminate to the
– skin
– heart
– nervous system
– joints
• If left untreated, the late stage occurs months to years later
• This involves chronic arthritis
• There is a vaccine available for dogs
• Brucellosis is often a serious systemic disease
• Brucella species cause brucellosis, which affects people who work
with large ruminant animals
– Infection can occur through eyes, abrasions, or
consumption of contaminated dairy products
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The bacteria are transported to the spleen and lymph glands
upon infection, causing flu-like symptoms
– Brucellosis is also called undulant fever because of a
specific fever pattern
– Rickettsial Infections Are Transmitted by Arthropods
– Rocky Mountain spotted fever (RMSF) is caused by Rickettsia rickettsii
– It is transmitted by hard ticks
• Symptoms include
• high fever
• headaches
• skin rash reflectingdamage to small blood vessels
• The rash progresses to a macropapular rash
• It begins on the palms and soles of the feet and spreads to the trunk
• Epidemic typhus (typhus fever) is a deadly disease caused by Rickettsia
prowazekii
• It is transmitted by feces of body lice (not head lice) that flourish
when sanitation and hygiene is poor
• The macropapular rash starts on the trunk and progresses to the
extremities
• High fever, hallucinations, and delirium can occur
• Endemic typhus (Mexican typhus, murine typhus) is caused by Rickettsia
typhi
• R. typhi are carried by oriental rat fleas
• Symptoms are
– mild fever
– headaches
– maculopapular rash spreading from trunk to limbs
• Scrub typhus (tsutsugamushi fever) is caused by Rickettsia tsutsugamushi
• It occurs in Asia and the Southwest Pacific
• It is transmitted by mites that dwell in scrubland
• Symptoms include fever and rash
• Rickettsialpox is caused by Rickettsia akari, transmitted by mites
• Brill-Zinsser disease appears to be a relapse of epidemic typhus
• Trench fever is caused by Bartonella (Rochalimaea) Quintana
• It was common during World War I, infecting ~1 million soldiers
• It is transmitted by body lice
• Symptoms include rash and fever
• Ehrlichial Infections Are Emerging Diseases in the United States
• Symptoms are similar to Lyme disease but come and go more quickly
• They cause a lowering of white blood cell count
• Human monocytic ehrlichiosis (HME) is caused by Ehrlichia chaffeensis
• It is transmitted by the Lone Star tick
• Human granulocytic ehrlichiosis is caused by Ehrlichia phagocytophila
• It is transmitted by the dog tick and deer tick
23.5 Systemic Viral Diseases
• Two herpesviruses cause blood diseases
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Infectious mononucleosis is a blood disease
• It particularly affects B lymphocytes in the lymph nodes and
spleen
• It is spread by contact with saliva
• It is caused by the Epstein-Barr virus (EBV)
• Many children are infected and show no symptoms
• Adolescents or young adults who are infected may develop EBV
disease (a precursor of mononucleosis)
• Complications include
• heart defects
• facial paralysis
• rupture of the spleen
• jaundice (hepatitis)
• After recovery, the individual remains a carrier for several months
• They can shed the virus in their saliva
• Diagnosis involves observation of
• elevated lymphocyte levels
• presence of Downey cells (damaged B cells)
• Antibodies can be detected by the Monospot test
• No vaccine or drugs for treatment are available
• EBV is associated with Burkitt lymphoma, a tumor of the jaw prevalent in
Africa
• The malaria parasite might help stimulate tumor development
• EBV is also associated with
• T-cell malignancies, including nasopharyngeal carcinoma
• B-cell lymphomas
• Hodgkin disease
• Multiple sclerosis
• Cytomegalovirus (CMV) disease can produce serious birth defects
• CMV disease is common, producing infectious mononucleosis-like
symptoms
• The virus may pass into the fetus of a pregnant woman, causing
mental impairment
• In immunocompromised people, it can reactivate
– This can accelerate the progression of HIV to AIDS and
infect many bodily tissues
Several Viruses Can Cause a Terrifying and Severe Hemorrhagic Illness
• Flaviviruses
• They are also called arboviruses because they are arthropodborne
• Yellow fever was the first human disease associated with a virus
• It is passed from person to person via blood-sucking mosquitoes,
Stegomyia aegypti
• Primary symptoms of yellow fever are
• abrupt headache
• fever
• muscle pain
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• Most patients recover after symptoms abate in 3–5 days
In some patients, the illness reappears as
• nausea
• uncontrollable hiccups
• black vomit, jaundice
• delirium
• hemorrhaging of the gums, mouth, and nose
• 50% of patients enter a coma and die from internal hemorrhaging
Two vaccines are available, but no therapeutic drugs
Dengue fever occurs in four types
• It is transmitted by two species of mosquito, S. aegypti and S. albopicta
• Early signs of dengue fever include
• high fever and prostration
• then sharp pains and sensations like bones are breaking
• Complications are unusual, unless one of the 3 other types of dengue fever
enters the body later
• In dengue hemorrhagic fever, the immune system allows the new
infection to replicate
– A rash from skin hemorrhages appear, followed by
» severe vomiting and shock
» decreased blood pressure
Members of the Filoviridae Produce Severe Hemorrhagic Lesions of the Tissues
• Ebola hemorrhagic fever (EHF) has occasional outbreaks in Africa,
causing 50–90% mortality
• It appears to be zoonotic, with fruit bats as a possible reservoir
• Transmission can occur with contact with blood or secretions from
an infected person or contaminated objects
• It damages endothelial cells, causing massive internal bleeding and
hemorrhaging
• Marburg hemorrhagic fever (MHF) was first identified in the tissues of
green monkeys
• Mode of transmission is unclear
• Symptoms are similar to EHF, but the fatality rate is lower
Members of the Arenaviridae Are Associated with Chronic Infections in Rodents
• Lassa fever is caused by a zoonotic virus carried by rodents
• It is transmitted through aerosol or direct contact with rodent
excreta or contaminated food
• Infection leads to
– severe fever
– exhaustion
– patchy blood-filled hemorrhagic lesions of the throat
• Congo-Crimea hemorrhagic fever occurs worldwide
• Oropouche fever and Sabia virus affect regions of Brazil
• Junin and Machupo occur in Argentina and Bolivia, respectively
• Guanarito virus is associated with Venezuelan hemorrhagic fever
15.3 Viral Infections of the
Gastrointestinal Tract
• Hepatitis Viruses A and E Are Transmitted by the Gastrointestinal Tract
• Hepatitis A is an acute inflammatory liver disease
• It is commonly transmitted by food or water contaminated by the
feces of an infected individual
– Transmission can also occur by raw shellfish
• Hepatitis A virus (HAV) belongs to the Picornaviridae family
23.6 Systemic Protozoal Diseases
• The Plasmodium Parasite Infects the Blood
• Malaria affects 300–500 million people
• Four species of Plasmodium cause malaria
• P. vivax
• P. ovale
• P. malariae
• P. falciparum
• Death can occur due to
• loss of RBCs
• RBC clustering in small vessels, causing clots
• Quinine is used for treatment
• Babesia Is an Apicomplexan Parasite
• It is a malaria-like disease caused by Babesia microti
• It is transmitted by ticks
• Parasites invade RBCs, causing
– anemia
– headache
– occasionally meningitis
• The Trypanosoma Parasites Can Cause Life-Threatening Systemic Diseases
• Trypanosomiasis is the name for 2 diseases caused by species of
Trypanosoma
• Human African sleeping sickness is caused by T. brucei
• It is transmitted by the tsetse fly
• A chancre forms at the bite site
• Parasites invade the bloodstream and then central nervous system
• American trypanosomiasis (Chagas disease) is found in Mexico and
Central and South America
• It is caused by T. cruzi
• Transmission occurs through triatomid insect bites
• Parasites reproduce in the blood, while the patient may remain
asymptomatic
• A chronic, irreversible disease may appear in 10–30 years
• Toxoplasma Causes a Relatively Common Blood Infection
• Toxoplasmosis is caused by Toxoplasma gondii
• Parasites invade all mammalian cells except RBCs
• Transmission can occur via contaminated beef, pork, and lamb
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It can also occur via domestic cats
• They pick up cysts from soil, birds, or rodents