Soilborne and Arthropodborne Diseases

2. Soilborne and Arthropodborne Diseases Soilborne Diseases Arthropodborne Diseases Plague Tularemia Lyme disease Relapsing fever Rickettsial Diseases Rocky Mountain Spotted fever Epidemic Typhus Endemic Typhus • Anthrax • Tetanus • Gas gangrene • Leptospirosis

3. Soilborne Bacterial Diseases Anthrax • Is a zoonosis • Bacillus anthracis causes anthrax • Anthrax is primarily endemic to large, domestic herbivores, • They ingest spores during grazing • B. anthracis produce three exotoxins that work together to cause disease

4. Bacillus anthracis is a Gram (+) spore-forming bacillus found in the soil.“Anthrax” means “coal” in Greek

5. Anthrax occurs in three forms, based upon the portal of entry – All are caused by B. anthracis. • Cutaneous Anthrax – 10-20% mortality rate • GI Anthrax – 50% mortality rate • Pulmonary Anthrax – 100% mortality rate

6. Cutaneous Anthrax • Most common • Tissue is destroyed = necrosis • Causes formation of deep, ulcerated lesions = eschars • Bacilli may invade across the skin to circulatory system • Can be acquired from leather products, instrument strings, etc.

8. GI Anthrax • Caused by ingestion of contaminated meat • GI inflammation and bleeding • Note swollen cervical glands

9. Pulmonary Anthrax • 5% of all cases – vy rare • What you will see if used as a weapon of biological warfare • 100% fatal, even with treatment, after the development of symptoms

10. Pulmonary Anthrax – causes bleeding and accumulation of fluid in the lungs

11. Anthrax, cont: Proper burial of carcasses Anthrax as an agent of biological warfare

12. Tetanus • Tetanus Causes Hyperactive Muscle Contractions • Tetanus is caused by Clostridium tetani • Spores can enter the body through a wound, and produce toxins • Tetanospasmin inhibits the release of GABA by an interneuron in the antagonistic muscle’s inhibitory pathway

13. This leads to continuous, uncontrolled muscle contraction

14. Mode of action of tetanospasmin

15. Trismus (lockjaw) involves spasms of the jaw muscle and clenching of the teeth • Opisthotonus involves muscle spasms that cause an arching of the back • Spasmodic inhalation and seizures in the diaphragm and rib cage • This reduces ventilation; patients will eventually suffocate • Sedatives, muscle relaxants, and penicillin are used in treatment • Inactivated tetanus toxoid is used in vaccine

17. Gas Gangrene Causes Massive Tissue Damage • Gangrene occurs when blood flow ceases to a part of the body • Gas gangrene (myonecrosis) is caused by Clostridium perfringens • Spores enter the body through a severe open wound

18. Gas Gangrene Symptoms

19. Vegetative cells ferment muscle carbohydrates and decompose muscle proteins • Large amounts of gas accumulate under the skin, causing a crackling sound • -toxin damages and lyses blood cells • Treatment involves: • Antibiotics • tissue debridement • Amputation • exposure in a hyperbaric oxygen chamber Figure 11.4, page 313

20. Leptospirosis Is a Zoonotic Disease Found Worldwide • Leptospirosis is carried by domestic and wild animals • Leptospira interrogans colonize the kidney of infected animals • The bacteria are passed through the urine • Humans acquire it by swimming in/consuming contaminated water Figure 11.5, page 314

21. The first phase involves flu-like symptoms and conjunctivitis • The second phase involves: • Fever • Meningitis • lung and liver inflammation • kidney damage • vomiting of blood • Mortality rate is low

22. Arthropodborne Bacterial Diseases • Disease that are acquired from insect vectors • Plague • Tularemia • Lyme disease • Relapsing fever • (Rickettsial Diseases) • Rocky Mountain Spotted fever • Epidemic Typhus • Endemic Typhus

23. Arthropod Vectors

24. The Plague • Plague Can Be a Highly Fatal Disease • The bubonic plague has resulted in widespread epidemics throughout history • It is endemic in the Southwestern states of the U.S., where it is carried by wild rodents such as prairie dogs • Two forms:bubonic form and pneumonic form

25. Plague is caused by Yersinia pestis • It is transmitted between hosts by the oriental rat flea Figure 11.6, page 316

26. Bubonic Plague: Symptoms

27. The Plague

28. 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

29. When plague is detected early, antibiotics can be used • A vaccine is available to high-risk groups • Note bipolar staining of cells

30. Tularemia Has More Than One Disease Presentation • Francisella 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 • Note bipolar staining of cells

31. 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 Figure 11.7, page 319

32. Lyme Disease Can Be Divided into Three Stages • Lyme disease is one of the major emerging infectious diseases in the U.S. • It is caused by Borrelia burgdorferi Figure 11.8a, page 319

33. It is usually transmitted by ticks • Ticks defecate into the wound they create during feeding Figure 11.8b, page 319 Figure 11.9, page 320

34. 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 Figure 11.10, page 321

35. The early disseminated stage of Lyme disease begins weeks to months later • Bacteria disseminate to the: • Skin • Heart • nervous system • Joints • Various symptoms • If left untreated, the late stage occurs months to years later • This involves chronic arthritis • Late stage may be caused by an autoimmune response – molecular mimicry?

37. Relapsing Fever is Carried by Ticks and Lice • Infected individuals go through periods of fever and chills interspersed with recovery Figure 11.11, page 321

38. Endemic relapsing fever is caused by Borrelia hermsii and B. turicatae • It is transmitted by tick bites • Epidemic relapsing fever is caused by Borrelia recurrentis • It is carried by the body louse • Infection occurs when the louse is crushed into its bite wound Textbook Case 11, page 323

39. Rickettsial and Ehrlichial Arthropodborne Diseases • Obligate intracellular parasites • Can not be cultured on “typical” media such as NA or TSA • Smaller cells than many bacteria • Rickettsial and Ehrlichial infections are transmitted by arthropods

40. Rocky Mountain Spotted Fever • Rocky Mountain spotted fever (RMSF) is caused by Rickettsia rickettsii • It is transmitted by hard ticks • Mortality rate is ~ 75% Figure 11.12a, page 324

41. Symptoms include: • high fever • Headaches • skin rash reflecting damage to small blood vessels • The rash progresses to a maculopapular rash • It begins on the palms and soles of the feet and spreads to the trunk Figure 11.13, page 324

42. Used to be Called the “Black Measles” • CNS symptoms • Headache/delirium/coma • High fever • Swollen joints • Maculopapular rash

43. Life Cycle of RMSF

44. 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 Figure 11.12b, page 324

45. 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 • Called “Tabardillo” in Mexico • Low mortality Figure 11.12c, page 324

46. 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

47. 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 Figure 11.14, page 326