Structure of the Cardiovascular System

1. Structure of the Cardiovascular System • Composed of three parts • Heart • Blood • Blood vessels • Heart pumps blood into arteries that are connected to veins via capillaries • Arteries carry blood away from the heart • Veins carry blood to the heart • Blood Composition • Serum-liquid part of blood • Formed elements-erythrocytes, leukocytes, platelets

2. Structure of the Cardiovascular System Figure 21.1

3. Structure of the Cardiovascular System • Blood is usually axenic • Movement of blood and lymph • The right ventricle pumps blood to the lungs • Oxygen enters blood and carbon dioxide diffuses out • Oxygenated blood returns to the heart through the left ventricle and then to the arteries and capillaries • Capillaries carry blood to the surrounding tissues and also leak fluid that is picked up by the lymphatic vessels

4. Bacterial Cardiovascular and Systemic Diseases • Bacteria can infect the blood, blood vessels, and heart • Septicemia • Presence of any microbial infection of the blood that produces illness • Bacteremia • Bacterial septicemia that is often harmless • Toxemia • Release of bacterial toxins into the blood • Lymphangitis • Infection and inflammation of the lymphatic vessels

5. Septicemia, Bacteremia, and Toxemia • Signs and Symptoms • Fever, chills, nausea, vomiting, diarrhea, malaise • Septic shock can develop rapidly • Very low blood pressure due to dilation of the blood vessels • Small hemorrhagic lesions called petechiae can develop • Osteomyelitis can occur when bacteria invade the bones • Toxemia symptoms vary depending on the toxin • Exotoxins-released from living microorganisms • Endotoxin-released from Gram-negative bacteria

6. Septicemia, Bacteremia, and Toxemia • Pathogens • Septicemia and toxemia are caused by various bacteria • Pathogens are often opportunistic or nosocomial infections • Gram-negative bacteria cause septicemia more often than Gram-positive bacteria • Virulence Factors • Presence of capsule that resists phagocytosis • Capacity to capture iron needed for bacterial growth • Endotoxin produced by Gram-negative bacteria

7. Septicemia, Bacteremia, and Toxemia • Pathogenesis and Epidemiology • Septicemia is acquired by direct inoculation of bacteria into the blood • Examples-medical procedures, drug users • Immunocompetent individuals rarely have septicemia • Bacterial infections in these people are self-limited • Gram-negative bacteria more likely to produce severe septicemia due to release of endotoxin as the bacteria die • Endotoxin activates various defensive reactions by the body

8. Potential Effects of Endotoxin Figure 21.4

9. Septicemia, Bacteremia, and Toxemia • Diagnosis, Treatment, and Prevention • Signs and symptoms are usually diagnostic • Bacteria are cultured from the blood in less than half the individuals with indications of sepsis • Treatment requires prompt identification and administration of antimicrobial drugs • Prevention includes immediate treatment of infections especially in individuals with compromised immune systems

10. Endocarditis • Cause: Viridans streptococci causes almost half the cases • Portal of entry: Inoculation of bacteria into the blood via open wounds • Signs/Symptoms: Fever, fatigue, malaise, tachycardia • Incubation period: Weeks to months • Susceptibility: Immunocompromised people or prolonged invasive medical procedures • Treatment: Intravenous antibiotic therapy • Prevention: High risk patients can be given prophylactic antibiotics when needed

11. Gas Gangrene • Cause: Clostridium species • Portal of entry: Introduction into dead tissue via traumatic event • Signs/Symptoms: Pain and swelling at injury site, fever, foul-smelling drainage, tachycardia • Incubation period: One to three days • Susceptibility: Presence of deep, lacerating wounds • Treatment: Surgical removal of dead tissue and antibiotic treatment • Prevention: Properly cleanse wounds

12. Systemic Disease • Systemic diseases are those that are carried throughout the body • Pathogens carried by the blood and lymph

13. Brucellosis • Cause: Brucella melitensis strains • Portal of entry: Consumption of contaminated dairy products or contact with animal blood, urine, or placentas • Signs/Symptoms: Fluctuating fever that spikes every afternoon • Susceptibility: Ranchers, dairy workers, and veterinarians • Diagnosis: Daily undulating fever is suggestive of brucellosis • Treatment: Usually requires no treatment • Prevention: Attenuated vaccine exists for animals

14. Tularemia • Cause: Francisella tularensis • Portal of entry: Bite of infected tick, consumption of contaminated meat or water, or inhalation • Signs/Symptoms: Skin lesion at site of infection and ascending lymphangitis • Incubation period: Typically three to five days • Susceptibility: Animal handlers and rabbit hunters • Treatment: Intramuscular administration of streptomycin and tetracycline • Prevention: Use insect repellant, wash hands after handling animal carcasses, cook game thoroughly

15. Plague • Signs and Symptoms • Bubonic plague • Characterized by enlarged, inflamed lymph nodes called buboes • Pneumonic plague • Occurs when the bacterium spreads to the lungs • Pathogen and Virulence Factors • Yersinia pestis, normally a pathogen of animals,is the causative agent • Virulence factors include adhesins, type III secretion systems, capsules, and antiphagocytic proteins

16. Yersinia pestis Life Cycle Figure 21.6

17. Plague • Diagnosis, Treatment, and Prevention • Due to the rapid progression of the disease it must be diagnosed and treated immediately • Diagnosed based on characteristic symptoms • Various antimicrobial drugs are effective for treatment • Prevention occurs through rodent and flea control and good personal hygiene

18. Lyme Disease • Lyme disease is a tick-borne zoonosis • Signs and Symptoms • Three phases • Expanding red rash that often resembles a bull’s eye • Neurological symptoms • Severe arthritis • Pathogen and Virulence Factors • Borrelia burgdorferi is the causative agent • The deer tick of the genus Ixodes is the vector • The bacterium uses manganese for metabolic processes

19. Life Cycle of Ixodes Figure 21.9

20. Lyme Disease • Epidemiology • Most reported vector-borne disease in the U.S. • Two events bring humans into closer contact with ticks and contribute to the increase in Lyme disease • Human populations have moved into woodland areas • Protection of the deer population

21. Lyme Disease • Diagnosis • Diagnosis is made based on the signs and symptoms of the disease • The bacterium is rarely detected in the blood • Treatment • Treatment of early phases is with antimicrobial drugs • Treatment of later phases is difficult since symptoms are often caused by the immune system • Prevention • Prevention includes use of repellants containing DEET, and use of protective clothing

22. Viral Cardiovascular and Systemic Diseases • Various viral diseases can spread through the cardiovascular and lymphatic systems • Mononucleosis • Cytomegalovirus disease • Yellow fever • Hemorrhagic fever

23. Infectious Mononucleosis • Often called the “kissing disease” • Signs and Symptoms • Severe sore throat and fever followed by enlarged lymph nodes • Pathogen and Virulence Factors • Epstein-Barr virus (EBV) is the causative agent • Life-long infection results since EBV becomes latent within cells • EBV can cause other conditions depending on the strength of the immune response of an individual

24. Diseases Associated with Epstein-Barr Figure 21.11

25. Infectious Mononucleosis • Pathogenesis • Transmission occurs via saliva • EBV infects B lymphocytes • Diagnosis, Treatment, and Prevention • Diagnosis made based on the presence of large, lobed B lymphocytes and neutropenia • Treatment focuses on relieving symptoms • Most cases resolve without treatment • Prevention is difficult due to the widespread occurrence of EBV

26. African Viral Hemorrhagic Fevers • Include Ebola and Marburg hemorrhagic fevers • Cause: Ebolavirus or Marburgvirus • Portal of entry: Contact with bodily secretions of infected individual or possibly via contact with the unknown host • Signs/Symptoms: Fever, fatigue, minor petechiae that progresses to severe internal hemorrhaging • Diagnosis: Characteristic symptoms and presence of virus in the blood • Treatment: Supportive care including fluid and electrolyte replacement

27. Characteristics of Some Viral Hemorrhagic Fevers Table 21.1

28. Protozoan Cardiovascular and Systemic Diseases • Cardiovascular and systemic diseases can be caused by various protozoa • Protozoa of the phylum Apicomplexa can cause disease in humans • Life cycles of these parasites are complex and involve at least two types of hosts • Diseases caused by apicomplexans • Malaria • Toxoplasmosis

29. Malaria • Signs and Symptoms • Cyclic symptoms that correlate with the parasite’s life cycle • Fever and chills recur every two to three days as erythrocytes lyse • Other symptoms include anemia, fatigue, and jaundice • Pathogens and Virulence Factors • Four Plasmodium species cause malaria • P. falciparum, P. vivax, P. ovale, P. malariae • Disease severity depends on the species • Life cycle occurs in three main stages

30. Malaria New Frontiers 21.1 photo

31. Malaria • Pathogenesis • P. falciparum causes the most severe malaria • Certain genetic traits can increase resistance to malaria • Sickle-cell trait • Hemoglobin C • Genetic deficiency of glucose-6-phosphate dehydrogenase • Lack of Duffy antigens • Epidemiology • Endemic in over 100 countries though not in the U.S.

32. Life Cycle of Toxoplasma gondii Figure 21.18

33. Malaria • Diagnosis • Presence of trophozoites or other Plasmodium stages in the blood • Treatment • Varies by species and severity of disease • Standard drug is chloroquine except with drug resistant cases • Usually effective except in severe falciparum cases • Prevention • Limiting contact with mosquitoes • Use of insecticides, repellants, and protective clothing

34. Toxoplasmosis • Signs and Symptoms • Majority of cases have no symptoms • Symptoms in those with poor immunity • Include fever, malaise, and inflammation of the lungs, liver, and heart • Symptoms in the fetus • Stillbirth, epilepsy, mental retardation • Pathogen and Virulence Factors • Toxoplasma gondii is the causative agent • Cats are the definitive host

35. Toxoplasmosis • Pathogenesis and Epidemiology • Infections usually arise from consuming undercooked meat containing the parasite • Transmission across the placenta can also occur • Specific mechanism of disease is not yet known • Diagnosis, Treatment, and Prevention • Diagnosed mainly by detecting organisms in tissues • Treatment is usually unnecessary except in AIDS patients and newborns • Prevention is difficult due to the numerous hosts of T.gondii