Med Para PDF - Introduction to Medical Parasitology

8/7/24 Biology 101 AN INTRODUCTION TO MEDICAL PARASITOLOGY 1 Parasitology the science that deals with the interactions between a host and the population of parasites that are found on or in that host....

8/7/24 Biology 101 AN INTRODUCTION TO MEDICAL PARASITOLOGY 1 Parasitology the science that deals with the interactions between a host and the population of parasites that are found on or in that host. Parasitology covers many aspects of parasites of and their hosts including: l the morphology, biochemistry, physiology and life cycles of parasites, l the immunological, pathological and clinical responses of the host to the presence of parasites, l all aspects of treatment and control of parasitic infections and diseases. 2 1  8/7/24 Terminology PARASITE: “a living organism that acquires some of its basic nutritional requirements through its intimate contact with another living organism”. Parasites may be simple unicellular protozoa or complex multicellular metazoan ENDOPARASITE: “a parasite that lives within another living organism” – e.g. Plasmodium, tapeworm ECTOPARASITE: “a parasite that lives on the external surface of another living organism” – e.g. lice, ticks 3 4 2  8/7/24 Terminology Obligate Parasite - Facultative parasites – not normally parasitic but won’t pass up the opportunity Accidental parasites – attach or enter wrong host, may or may not survive but can be very pathogenic. Permanent parasites - live adult lives in or on host Temporary parasites - eat and run Epiparasite - These feed on other parasites in a relationship known as hyperparasitism. A flea lives on a dog, but the flea may have a protozoan in its digestive tract. The protozoan is the hyperparasite. 5 Obligate vs. Facultative Parasite Taenia solium Naegleria fowleri 6 3  8/7/24 Accidental parasite in humans Echinococcus granulosus infects man accidentally 7 Terminology HOST: “the organism in, or on, which the parasite lives and causes harm” Definitive host: “the organism in which the adult or sexually mature stage of the parasite lives” Intermediate host: “the organism in which the parasite lives during a period of its development only” Zoonosis: “a parasitic disease in which an animal is normally the host - but which also infects man” Vector: “a living carrier (e.g.an arthropod) that transports a pathogenic organism from an infected to a non-infected host”. A typical example is the female Anopheles mosquito that transmits malaria 8 4  8/7/24 The burden of some major parasitic infections Parasite Diseases No. people Deaths/yr infected Plasmodium Malaria 273 m 1.12 m Soil transmitted worms: Pnemonitis, intestinal 2 billion 200,000 Roundworm (Ascaris) obstruction Whipworm (Trichuris) Bloody diarrhoea, rectal Hookworm prolapse (Ancylostoma and Coughing, wheezing, Necator) abdominal pain and anaemia Schistosoma Renal tract and intestinal 200 m 15,000 disease Filariae Lymphatic filariasis and 120 m Not fatal but 40 elephantiasis m disfigured Trypanasoma cruzi Chagas disease 13 m 14,000 African trypanosomes African sleeping sickness 0.3 – 0.5 m 48,000 Leishamania Cutaneous, mucocutaneous 12 million; 2 50,000 and visceral leishmaniasis million new cases/yr 9 Malaria 10 5  8/7/24 Taxonomic classification of parasitic organisms there is no universally accepted system part of the animal kingdom which comprises some l 800,000 identified species categorised into 33 phyla Protozoan (unicellular) parasites are classified according to morphology and means of locomotion. l 45,000 protozoa species. l Most species that cause human disease belong to the phylums sarcomastigophora and apicomplexa Metazoa (multicellular) include the worms (helminths) and arthropoda (posses an external skeleton) e.g. ticks, lice 11 Parasitic Infection and Immunity 12 6  8/7/24 Factors influencing pathologic potential of a parasite: The migratory pathway in a host The anatomical site where a parasite stays in the host’s body Feeding habits The predilection site The propensity to stimulate hyperactive immunological responses in the host 13 Trichenella spiralis 14 7  8/7/24 Pathogenic effects of parasites: !" #$%&'%()*+,-./0-123)24)52,-)-1,,/+,)2.))))) ))))))))2.673,)89):+0573107;)2.)05+:107;):+73," ))))))))+"6")%,07.1,)73*)522" ?&#$@#@A?)$ABB@?C ))))))+"6")D1E59;;282-5.1/:);7-/:F) )))))))))))%,07.1,);/:8.1021*+,() ))G")@?#H$%I#@A?)AJ)KAL#)@''&?H))) ))))))$HLMA?LH ))))))+"6")N")8730.24-1 )))))))))))))A")O2;O/;/, 15 16 8  8/7/24 17 18 9  8/7/24 $+70-123,)24)K2,-,)-2)M7.7,1-+,( !" L-1:/;7-123)24)-5+)52,-)-1,,/+).+70-123 M.2;14+.7-123)73*)1341;-.7-123)24)0+;;,))) )))),/..2/3*136)-5+)2.6731,: >" K9E+.E;7,17)24)-5+)+E1-5+;17;);133136 P)))@30.+7,+)13)-5+)3/:8+.)24)0+;;,)13).+,E23,+)) )))))-2)73)73-182*9 G" J18.2,1,)Q,E+014107;;9)=1-5);236),-73*136 ))))E7.7,1-+,R 19 HOST DEFENSE MECHANISM AND IMMUNITY L/,0+E-18;+)K2,-()7)52,-)-57-)07332-)+;1:137-+) -5+)E7.7,1-+)8+42.+)-5+)E7.7,1-+)073)8+02:+) +,-78;1,5+* $+,1,-73-)K2,-()14)52,-S,)E59,12;26107;),-7-/,) E.+O+3-,)-5+)+,-78;1,5:+3-)73*),/.O1O7;)24) -5+)E7.7,1-+" @::/31-9()Q),93")-2).+,1,-730+R T),-7-+)24)E.2,,+,,136)-1,,/+,)0787;+)24).+02631U136)73*)E.2-+0-136)-5+)731:7;)76713,-) 323,+;4)13O7*+.," 20 10  8/7/24 Immunity and body defenses Nonspecific defenses – defenses that protect us against any pathogen, regardless of species. Specific defenses- a third line of defense the body provides against particular pathogens; based on cells of the immune system called LYMPHOCYTES and the production of ANTIBODIES. 21 An Overview of the Body’s Defenses 22 11  8/7/24 INNATE IMMUNITY 23 Nonspecific Defenses: Physical Barriers Chemical Mechanical Sebum w/ unsaturated fatty acids Skin Structure Perspiration Saliva washes Lysozyme Mucus traps and ciliary Acid conditions: skin (3-5pH) escalator Normal microbiota Urine, vaginal flows out Transferrins, and NO Figure 22.10 24 12  8/7/24 Nonspecific Defenses: Physical Barriers Ciliary Escalator 25 Nonspecific Defenses- Phagocytes Remove cellular debris and respond to invasion by foreign pathogens l Monocyte-macrophage system - Fixed and free l Microphages – Neutrophils and eosinophils l Move by diapedesis l Exhibit chemotaxis 26 13  8/7/24 Phagocytosis – a process of engulfment of the invading particle within an evagination of the phagocyte’s cell membrane V9,2,2:+,)+:E-9)*16+,-1O+)+3U9:+,) Q;9,2U9:+,R)13-2)-5+)O70/2;+)-2)*+,-.2.9)-+) E7.7,1-+" %**1-1237;)+3U9:+,),+0.+-+*() )))T).+70-1O+)2W96+3)13-+.:+*17-+,) )))))QA!TX)K!A!X)YA!X)AKZRX ))))T).+70-1O+)31-.26+3)13-+.:+*17-+," 27 Phagocytes Figure 22.10 28 14  8/7/24 §[/E44+.)0+;;,)13);1O+.) ,13/,21*, §M576209-10).+-10/;7.) 0+;;,)24);9:E57-10) -1,,/+X):9+;21*)-1,,/+X) 73*),E;++3 §D/,-)0+;;,)24))-5+) ;/36, §'70.2E576+,)13) ;9:E5)32*+, 29 30 15  8/7/24 Nonspecific Defenses Immunological Surveillance Figure 22.10 31 Nonspecific Defenses- Interferons (cytokines) Small proteins released by virally infected cells Trigger the production of antiviral proteins Three major types of interferons are: l Alpha– produced by leukocytes and attract/stimulate NK cells l Beta– secreted by fibroblasts causing slow inflammation l Gamma – secreted by T cells and NK cells stimulate macrophage activity 32 16  8/7/24 Nonspecific Defenses Complement System Figure 22.10 33 Nonspecific Defenses - Fever also known as pyrexia and febrile response having a temperature above the normal range due to an increase in the body's temperature set-point. between 37.5 and 38.3 °C (99.5 and 100.9 °F).[ pyrogen is a substance that induces fever Figure 22.10 34 17  8/7/24 Inflammation function of inflammation is to eliminate the initial cause of cell injury, clear out necrotic cells and tissues damaged from the original insult and the inflammatory process, and to initiate tissue repair. calor, dolor, rubor, tumor (heat, pain, redness and swelling) and loss of function 35 Inflammation Figure 22.13 36 18  8/7/24 Figure 22.14 37 ACQUIRED IMMUNE RESPONSE (in vertebrates) v T)7),9,-+:)24)323T,+;4).+02631-123)-57-).+,/;-,)13)130.+7,+*).+,1,-730+)-2),E+01410) 42.+163),/8,-730+,)2.)13O7*+.,)23).+E+7-+*) +WE2,/.+" stimulated by specific foreign substances: ANTIGENS – any substance with MW> 3000, most commonly CHONs and usually foreign to host and stimulate an immune response. 38 19  8/7/24 Properties of Specific/ Adaptive Immunity Specificity – activated by and responds to a specific antigen Memory – “remembers” any antigen it has encountered Tolerance – responds to foreign substances but ignores normal tissues 39 The immune system response Antigen triggers an immune response Activates T cells and B cells vT cells are activated after phagocytes exposed to antigen T cells attack the antigen and stimulate B cells Activated B cells mature and produce antibody Antibody attacks antigen 40 20  8/7/24 Overview of the immune response: 41 Cell Mediated Immunity communication done by CYTOKINS – protein hormones Cytotoxic or killer T cells (CD8+) do their work by releasing lymphotoxins, which cause cell lysis. Helper T cells (CD4+) – l secrete chemicals called lymphokines that stimulate cytotoxic T cells and B cells to grow and divide, l attract neutrophils, and enhance the ability of macrophages to engulf and destroy microbes. Suppressor T cells inhibit the production of cytotoxic T cells once they are unneeded, lest they cause more damage than necessary. Memory T cells are programmed to recognize and respond to a pathogen once it has invaded and been repelled. 42 21  8/7/24 Antigen Recognition and the Activation of Cytotoxic T Cells Figure 22.17 43 Antigen Recognition and Activation of Cytotoxic T Cells 44 22  8/7/24 A Summary of the Pathways of T Cell Activation Figure 22.19 45 Humoral Immune Response Based on antibodies %?#@BAD@HL() E.2-+13)07;;+*) 1::/326;28/;13,) Q@6'X)@6CX)@6%X)@6DX) @6HRX) produced by lymphocytes. 46 23  8/7/24 47 B cells become plasma cells, which produce antibodies when a foreign antigen triggers the immune response. 48 24  8/7/24 Antibody binds to antigenic determinants (epitopes) and this: Inactivates the antigen as in neutralizing toxins or blocking receptors; Crosslinks antigens which leads to: v PRECIPITATION of proteins and v AGGLUTINATION of cells; Activates Compliment and destroys invading cells; Opsonizes bacterial cells and viral particles and helps in phagocytosis 49 50 25  8/7/24 51 26