Cardiovascular, Lymphatic, and Systemic Infectious Diseases

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

•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

–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 smallblood vessels

•The rash progressesto a macropapular rash

•It begins on the palmsand soles of the feetand 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

•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

•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

•It can also occur via domestic cats

•They pick up cysts from soil, birds, or rodents