Soilborne Infectious Diseases PDF

Soilborne Diseases 1 Soilborne Diseases: An Overview pathogen originates in the soil, then pathogen can get in the air and get inhaled pathogen doesnt have to go in the air, it can be transmitted byus touching the soil Transmission: direct:touching the soil Contact transmission indirect contact:pat...

Soilborne Diseases 1 Soilborne Diseases: An Overview pathogen originates in the soil, then pathogen can get in the air and get inhaled pathogen doesnt have to go in the air, it can be transmitted byus touching the soil Transmission: direct:touching the soil Contact transmission indirect contact:pathogen in drysoil, gets airborne and gets inhaled Vehicle transmission soil borne Major portal of entry? skin, rasperatorytract Predisposing factors? contact with contaminated soil Best preventive measure? moisten the soil so it doesnt get airborne, or dont touch soil Best treatments? barterial = antibacteria, anti fungal, antiparasitic 2 Common Soilborne Diseases Bacterial Tetanus, Gas Gangrene Fungal Valleyfever Histoplasmosis, Coccidioidomycosis Parasitic Hookworm Infection, Ascariasis All caused byworms 3 Tetanus all species of Clostridium are obligate anaerobe (air kills them) Causative agent: Clostridium tetani Gram-positive bacteria, bacilli, endospore-forming, obligate anaerobe, mostly found in deep layers of soil Where in the body can these bacteria grow? deep layers of muscle, deep wounds (like stab wounds) What is the mode of transmission? soil borne transmission.Spores in soil, spore gets introduced in deep muscle layer Potent Tetanospasmin neurotoxin virulence factor low LD50 causes muscle spasms C. tetani 4 Tetanus bc there is no air in deep tissue it germinates Toxemia: spores enter anaerobic deep tissue  germination  from spore to active cell bacteria produce neurotoxin  target the CNS Blocks relaxation pathway in muscles  causing muscle spasms constant contraction Head, neck & back muscles stiffness/spams Respiratory muscles spams  death Diagnosis based on symptoms Figure 22.6 5 Tetanus Predisposing factors Direct contact with fomites  Ex - “rusty” nail or sharp objects contaminated with spores of C.tetani contaminated non living obj ects Prevention: DTaP, TDaP, & Td vaccines toxoid vaccine Treatment Antibiotics anti-toxin Tetanus Immune Globulin (TIG)  Is this an antibody to the pathogen or the toxin? TOXIN Sedation drugs to control muscle spasms infected with spores, spores germinate and become active cells, cells produce neurotoxin tetanospasmin 6 Gas Gangrene myo = muscles necrosis = death AKA Clostridial Myonecrosis Causative agent: Clostridium perfringens  Gram-positive bacteria, bacilli, endospore-forming, obligate anaerobe, grow in deep tissue wound REVERSIBLE Ischemia - blood vessel blockage  loss of blood supply to tissue IRREVERSIBLE Necrosis - irreversible process; death of tissue  gangrene: tissue death due to interrupted blood supply is a type of necrosis (there are different types of necrosis) Several types of Gangrene  Ex - Dry Gangrene, Wet Gangrene, Gas Gangrene 7 Gas Gangrene If spores enter ischemic area of the body, spores will germinate and produce toxins Produce alpha toxin that moves along tissue/muscle bundles Low blood flow Misc Soilborne spores enter ischemic area of body    toxins released  vascular & tissue damage Symptoms Severe pain & swelling; pale area  red  blackish green Gas and fluid-filled blisters often form Diagnosis based upon symptoms, imaging tests, or culture What are some predisposing factors? V.F. Ischemia that is not Reversed 8 Gas Gangrene Necrotic tissue Figure 23.8 9 Gas Gangrene Treatment: Immediate high doses of antibiotics Debridement Surgical removal of necrotic tissue, amputation bc pathogen is anaerobe Hyperbaric chamber - delivers oxygen Misc Misc Misc Misc Progresses quickly from initial injury to gas gangrene within 48 hours About 20% of people with gas gangrene in a limb require amputation 20 - 25% mortality rate Common cause of death in wars 10 FUNGAL Histoplasmosis Causative agent: Histoplasma capsulatum V.F. mold spores can exist in Yeast and mold form Dimorphic fungus, fungal spores found in soil Yeast-form grows intracellularly in VF macrophages found in humans Reservoirs  1° = bird & bat droppings; 2° = soil Acquired by inhalation of microscopic fungal spores called airborne conidia similar to tuberculosis symptoms Forms lung lesions Fungemia Is this a local or systemic infection? systemic fungal infection because funGEMIA Figure 24.15 11 Histoplasmosis Mostly asymptomatic 0.1% of cases become a severe disease Mild Flu-like subclinical symptoms resembling Tuberculosis Culturing of lung tissue or sputum sample; chest x-ray If chest x-ray shows lung lesions, how do we know this is not Tuberculosis? need to do tuberculent skin test (needs to be negative for TB)or Acid fast stain Which people are at high risk for Histoplasmosis? People who handle birds, exploring caves (bc bats live in caves) 12 Histoplasmosis Commonly occurs in the Mississippi and Ohio River Valleys No vaccine available Treated with antifungals/antimycotics (Itraconazole) usuallymeans antifungal/antimycotic drugs Figure 24.16 13 Coccidioidomycosis AKA Valley Fever or San Joaquin Fever Causative agent: Coccidioides immitis VF VF Dimorphic fungus, fungal spores Complex lifecycle of C. immitis Acquired by inhalation of fungal spores called airborne arthroconidia  spherules in tissue  release endospores Figure 24.17 14 Coccidioidomycosis 15 Coccidioidomycosis Mostly asymptomatic Mild Flu-like subclinical symptoms resembling Tuberculosis Culturing of lung tissue or sputum sample; chest x-ray Arthroconidia found in desert soils of the American Southwest No vaccine available Treatment? Antimycotics/Antifungal Figure 24.18 16 W ORM INFECTION Hookworm Infection Round worm Caused by parasitic helminths: Necator americanus (New World Hookworm) America Ancyclostoma duodenale (Old World Hookworm) Europe and Asia Kingdom Animalia, Phylum Nematoda round worm Round worm male and female that mate Hooked-shaped body, separate sexes, specialized mouth parts Figure 25.24 Ancyclostoma duodenale 17 Hookworm Infection VF Complex lifecycle of hookworm: Adult attaches to intestinal wall  feeds on blood & tissue Adults, eggs, larvae larvae matures in adults Which structure is the infective penetrating larvae stage? Penetrating larvae What is the mode of transmission? human defecates eggs in to soil Soil Soil larvae in the soil 18 Hookworm Infection Large number of worms: anemia & fatigue Look for eggs in stool sample barefoot Larvae in contaminated soil penetrate bare skin Prevention? wear shoes Treatment with antiparasitic/antihelminthic drugs (Mebendazole) bend means antiparasitic drug 19 Ascariasis LARGEST OF ALL W ORMS Larvae and worms can exist both in humans and soil Caused by parasitic helminth: Ascaris lumbricoides ROUND W ORM Kingdom Animalia, Phylum Nematoda Largest parasitic round worm, separate sexes, specialized mouth parts VF Complex lifecycle of A. lumbricoides: Adult attaches to intestinal wall  feeds on blood & tissue Adults, eggs, larvae larvae develops into adulst human ingests eggs byaccident human defecates eggs in the soil Which structure is the infective stage? accidental INGESTION of eggs What is the mode of transmission? Soil 20 Ascariasis large number of worms Mostly asymptomatic; heavy infections cause intestinal blockage & impair growth in children Look for eggs in stool sample Predisposing factors? poverty, unsanitaryconditions Do not ingest soil, wash hands Treatment? antiparasitic dugs 30% of worldwide population is infected Figure 25.25 21