Cardiovascular & Lymphatic system infections: Part 1

What is the composition of the cardiovascular system?

1.) Blood vessels — carry blood to and from all regions of the body

2.) Heart — pumps the blood

3.) Closed circuit known as the circulatory system

Functions of the cardiovascular system:

• provides tissues with oxygen and nutrients

• carries away carbon dioxide and waste products

What is the composition of the lymphatic system?

1.) Lymph vessels — roughly parallel the blood vessels

2.) Lymph nodes — cluster at body sites such as the groin, neck, armpit, and intestines

3.) Spleen

Functions of the lymphatic system:

• major source of immune cells and fluids

• one-way passage: returns fluid from the tissues to the cardiovascular system

Why must the cardiovascular system be highly protected from microbial infection?

• microbes that successfully invade the system have access to every part of the body

• bloodstream infections are considered systemic infections

What are the cardiovascular/lymphatic system’s multiple defenses against infection?

• 5,000 to 10,000 WBC per microliter of blood

• lymphocytes: adaptive immunity

• phagocytes: critical to innate and adaptive immune responses

Medical conditions involving the blood have the suffix:

-emia

Viremia

presence of viruses in the blood

Fungemia

presence of fungi in the blood

Bacteremia

presence of bacteria in the blood

Septicemia (sepsis)

bacteria growing and flourishing in the blood

Septic shock

cascading immune responses to septicemia, resulting in decreased blood pressure, life-threatening condition

The cardiovascular and lymphatic systems are “closed” systems with no access to the external environment:

• no microorganisms colonize either the lymphatic or cardiovascular systems in healthy individuals

• recent studies (Human Microbiome Project) suggest that the bloodstream is not completely sterile, even in periods of apparent health

• low-level microbial “infections” may contribute to diseases for which no etiology has been found or for conditions thought to be noninfectious

_____ has been one of the greatest afflictions throughout human history

Malaria

• same rank as bubonic plague, influenza, and tuberculosis

• dominant protozoan disease

• threatens 40% of the world’s population every year

What does Malaria mean in Italian?

mal (“bad”) and aria (“air”)

Malaria — causative agent:

• Plasmodium species are protozoans in the sporozoan group

  • contains more than 200 species but only five infect humans: P. malariae, P. vivax, P. knowlesi, P. ovale, and P. falciparum, each showing variations in pattern and severity of disease

Development of the malarial parasite is divided into 2 distinct phases:

1.) Asexual phase: carried out in the human

2.) Sexual phase: carried out in the mosquito

Malaria — transmission and epidemiology:

• primary spread by the female Anopheles mosquito

  • Malaria was once distributed throughout the world

  • mosquito control in temperate areas has restricted it to a belt around the equator

• 200 million new cases are still reported each year, 90% of them in Africa

  • most frequent victims are children and young adults; around 500,000 die annually

• total case rate in the US is 1,000 to 2,000 new cases a year

  • most occur in immigrants or travelers to endemic areas

_______ reported 5-10 locally acquired cases of malaria in 2003 in Palm Beach County, involving the P. vivax species

Florida

Malaria — signs and symptoms:

• 10-16 day incubation period

• first symptoms are:

  • Malaise, fatigue, vague aches, and nausea with or without diarrhea

  • followed by chills, fever, and sweating which occur cyclically at 48-72 hour intervals

• interval, length, and regularity of symptoms reflect the type of malaria:

  • Falciparum malaria: persistent fever, cough, and weakness for weeks without relief

• complications

  • hemolytic anemia from lysed red blood cells

  • organ enlargement and rupture due to cellular debris that accumulates in the spleen, liver, and kidneys

_________ one of the most serious complications of falciparum malaria

Cerebral malaria

• small blood vessels in the brain become obstructed due to RBCs adhering to blood vessel walls

• decrease in oxygen in the brain can cause coma and death

In general, malaria has the highest death rate in the _____ phase, especially in children

acute

Malaria caused by Plasmodium vivax and P. ovale are subject to ______ because some infected liver cells harbor dormant protozoans for up to 5 years

relapses

Malaria — pathogenesis and virulence factors:

• invasion of merozoites into RBCs leads to the release of fever-inducing chemicals into the bloodstream

• Plasmodium also metabolizes glucose at a very high rate, leading to hypoglycemia in the human host

• damage to RBCs results in anemia

• accumulation of malarial products in the liver and the immune stimulation in the spleen can lead to enlargement of these organs

• individual protozoa can express different surface antigens, making it difficult for the host immune system to battle

Malaria — culture and diagnosis:

• definitive diagnosis by the discovery of a typical stage of Plasmodium in stained blood smears

• newer Ag-specific tests have been developed, but the smears are still considered the gold standard

• other indications are knowledge of the patient’s residence or travel in endemic areas and symptoms of recurring chills, fever, and sweating

Malaria — prevention:

• prevention is attempted through long-term mosquito abatement and human chemoprophylaxis

• humans reduce their risk by:

  • using netting, screens, and repellants

  • remaining indoors at night

  • taking weekly doses of antimalarial drugs

• malarial vaccine would be ideal

• in 2019, a major breakthrough in vaccine research occurred with trials of a vaccine called RTS, S:

  • effective against P. falciparum (the most deadly and most common strain in Africa)

  • found to be highly effective in children

  • beginning in 2021, it will be used in pilot vaccination programs in African countries

Malaria — treatment:

• Quinine has long been a mainstay of malaria treatment:

  • Chloroquine, the least toxic type, is used in nonresistant forms of the disease

• malarial protozoan has developed resistance to nearly every drug used for its treatment

• Artemisinin, a plant compound, has been most effective

  • it should be used in combination with other drugs to prevent resistance development!!