Leprosy (麻風) Information PDF

Hansen’s Disease: leprosy (麻風) Leprosy was first described in 600 BC and was recognized in the ancient civilizations of China, Egypt, and India. The global prevalence of leprosy has fallen dramatically with the widespread use of effective therapy. Leprosy is a chronic infection that affe...

Hansen’s Disease: leprosy (麻風) Leprosy was first described in 600 BC and was recognized in the ancient civilizations of China, Egypt, and India. The global prevalence of leprosy has fallen dramatically with the widespread use of effective therapy. Leprosy is a chronic infection that affects the skin and peripheral nerves. Leprosy sanatorium in 1900s’ China http://www.tyxts.com/lishi/2017/0130/87007.html 32  Mycobacterium leprae Weakly gram-positive, strongly acid-fast rods, lipid-rich (mycolic acids) cell wall, obligate intracellular, aerobic bacterium. Unable to be cultured on artificial media; slow progressing disease. Wikipedia https://www.studyblue.com/notes/note/n/med-micro-6/deck/774423 33  Acid-fast (Ziehl–Neelsen) staining *This red dye is retained by the mycolic acid rich cell wall classes.midlandstech.edu 34  Leprosy diseases Two forms: the tuberculoid form - milder and characterized by hypopigmented skin macules; the lepromatous form - disfiguring skin lesions, nodules, plaques, thickened dermis, and involvement of the nasal mucosa. 35  Pathogenesis Patients with tuberculoid leprosy have a strong cellular immune reaction with many lymphocytes and granulomas, present in the tissues and relatively few bacteria. Patients with lepromatous leprosy have a strong antibody response but a specific defect in the cellular response to M. leprae antigens. Thus an abundance of bacteria are typically observed in dermal macrophages and the Schwann cells of the peripheral nerves. 36  Epidemiology Fewer than 300,000 new cases were reported in 2005, with most cases in India, Nepal, and Brazil. Leprosy is spread by person-to-person contact. Although the most important route of infection is unknown, it is believed that M. leprae is spread either through the inhalation of infectious aerosols or through skin contact with respiratory secretions and wound exudates. Numerous M. leprae are found in the nasal secretions of patients with lepromatous leprosy. Lepromatous form of disease, but not the tuberculoid form, is highly infectious. 37  Respiratory tract anatomy The upper respiratory tract includes: mouth, pharynx and larynx. The lower respiratory tract includes: trachea, bronchi and bronchioles. pharynx www.teachpe.com 38 medical-dictionary.thefreedictionary.com  The upper respiratory tract The upper respiratory tract is colonized with numerous organisms, with Potentially pathogenic organisms 10 to 100 anaerobes Streptococcus pyogenes (more) for every aerobic Streptococcus pneumoniae Staphylococcus aureus bacterium (fewer). Neisseria meningitidis Most of the common Haemophilus influenzae Moraxella catarrhalis organisms in the upper Enterobacteriaceae respiratory tract are relatively avirulent and are rarely associated with disease unless they are introduced into normally sterile sites (e.g., sinuses, 39 middle ear, brain).  The lower respiratory tract and lung The air inhaled through the nostrils passes through the trachea and enters into the bronchi. The bronchi: the two tubes that carries air to the lungs. The bronchi further splits into smaller branches called bronchioles. Finally leading to the minute air sacs called alveoli, the unit structure of the lungs. 40 Defense mechanism in respiratory tract Lower airways are generally sterile. Mucociliary clearance  Infectious particles larger than 8-10 μm are efficiently trapped in a mucociliary blanket lining (formed by cilia cells) in the nares, trachea and bronchi.  A large amount of mucus is produced by goblet cells present in ciliated columnar epithelium, forming a viscous layer.  Once an organism is trapped in this viscous layer, directional ciliary action transports it to the back of the throat where it can be swallowed or expelled via coughing. 41 Mucociliary clearance movie https://www.youtube.com/watch?v=HMB6flEaZwI 42  The transport vehicle - Aerosol An aerosol is a colloid (suspension) of fine solid particles or liquid droplets, in air or another gas e.g. very fine dust, fume, mist, smoke and fog. Small droplets in the breath and the cough are also aerosols. Aerosols are suspended in air and can travel in air. Smoke Volcanic Ash Mist and clouds 43  Aerosols produced by human sneezing The diameters of aerosols cough produced by sneezing and coughing range from 1 to 1000 μm (1 mm). Z. Y. Han et al, 2013 http://www.livescience.com/32307-why-do- http://www.virology.ws/2015/02/21/ebo http://www.msd-animal- 44 bright-lights-make-me-sneeze.html lavirus-will-not-become-a-respiratory- health.ie/diseases/cattle/bovine_r pathogen/ esp_disease/Introduction.aspx  Airborne disease Bacteria and other pathogens are small enough to be carried by aerosols. Airborne diseases include any that are caused by pathogens and transmitted through the air carried by aerosols. Examples: Anthrax – inhalation of spores of Bacillus anthracis. Legionnaires’ disease by Legionella pneumophila. SARS - respiratory disease caused by coronavirus SARS in Hong Kong conservativepapers.com http://leiden.dachs- 45 archive.org/archive/leiden/sars/web/photos/20041115/www.ti me.com/time/asia/photoessays/sars/hongkong/index.html  Airborne disease transmission Human expulsion of air and aerosol transmission. Wearing face mask and good hygiene practices (e.g. frequent hand washing) could reduce the rate of airborne disease transmission. 46