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1、Opportunistic parasite,parasite,Opportunistic parasite-some symbiotic protozoa are nonpathogenic or cause only limited clinical symptoms in immunocompetent host,but produce serious symptoms in immunodeficient persons.,Toxoplasma gondii Cryptosporidium parvum Pneumocystis carinii Strongyloides sterco
2、ralis,factors that causing immunity suppression:malignant tumor,long-term radiotherapy,organ transplantation,long-term using immunosuppressive drugs,severe protein-calorie malnutrition,congenital immune deficiency disease,AIDS etc.,Opportunistic pathogen parasite-some symbiotic protozoa are nonpatho
3、genic or cause only limited clinical symptoms in immunocompetent host,but produce serious symptoms in immunodeficient persons.,Toxoplasma gondii Cryptosporidium parvum Pneumocysis carinii Strongyloides stercoralis,Toxoplasma gondii,Morphology,1.Tachyzoites:,2.Bradyzoites:3.Cyst:,4.Oocysts:,Life Cycl
4、e,In cats,Life Cycle,tachyzoites,tachyzoites,In humans,C.Transmission electron micrograph of an intracellular tachyzoite.Note a parasitophorous vacuole(PV)around the tachyzoite.Parasite organelles visible in this picture include a conoid(c),micronemes(m),dense granules(dg)nucleus(n)and rhoptries(r).
5、Bar=0.8 m.(Courtesy of Dr.D.S.Lindsay,Auburn University,AL.),Extracellular(arrow)released from host cells.Compare their size with red blood cells and a lymphocyte.Impression smear,Giemsa stain.Bar=20 m.B.Intracellular in cell culture.Note a group arranged in a rosette(arrow)and vacuole(arrowhead)aro
6、und a tachyzoite.Immunohistochemical stain with a tachyzoite-specific monoclonal antibody.Bar=20 m.,C.Transmission electron micrograph of a small tissue cyst in cell culture.Note thin cyst wall(arrow)enclosing 6 bradyzoites(arrowheads).Bar=1.0 m.(Courtesy of Dr.D.S.Lindsay,Auburn University,Auburn,A
7、L.),Tissue cyst freed from mouse brain.Note a thin(arrow)cyst wall enclosing hundreds of bradyzoites.Unstrained.Bar=20 m.B.Two tissue cysts(arrows)in section of brain.Hematoxylin and eosin stain.Bar=20 m.,A.Schizonts(double arrowheads),female gamonts(arrows),and male gamonts(arrowheads)in section of
8、 superficial epithelial cells of the small intestine of a cats.Hematoxylin and eosin stain.Bar=15 m.B.Three male gametes each with 2 flagella(arrowheads)compared with a merozoite(arrow).Impression of intestinal epithelium of a cat.Giemsa stain.Bar=10 m.C.Unsporulated oocytes(arrow)in feces of a cat.
9、Note 2 oocysts of another feline coccidium,Isospora felis(arrowheads).Isospora felis sporulates faster than T gondii.The oocysts on top of the picture already contains 2 sporocysts while all T gondii oocysts are unsporulated.Unstained.Bar-65 m.D.Transmission electron micrograph of a sporulated oocys
10、t.Note thin oocyst wall(arrow),2 sporocysts(arrowheads)and 4 sporozoites(double arrowheads)in sporocysts.Bar-2.25 m.(Courtesy of Dr.D.S.Lindsay,Auburn University,Auburn,AL.),summary,1.the definitive host：the domestic cat and other felids such as:2.intermediate hosts：such as humans or mice,pig,cat,ca
11、ttle,sheep,horse,rabbit,birds and fish etc.,4.parasitic site：the karyotes.(lymph node,brain,liver,heart,lung,muscles).,3.infect stage：tachyzoites,cysts and oocysts.,5.models of transmission:1)Prenatally acquired infection-to cross the placenta to infect the fetus.2)Postnatally acquired infection by
12、ingesting food contaminated by oocysts from cat feces.through the consumption of uncooked infected meat.,summary,Pathogenesis,necrosis is caused by intracellular multiplication of tachyzoites.,necrosis may develop in many organs,such as intestinal and mesenteric lymph nodes,eye,heart,and adrenals,br
13、ain,liver,1.congenital toxoplasmosis：.If it infects women during pregnancy,tachyzoites may cross the placenta to infect the fetus.This may result in spontaneous abortion,a stillborn or handicapped child.,Clinical Manifestations,2.Postnatal toxoplasmosis（1）immunocompetent individuals:.Disease is loca
14、lly and generalized and is rarely severe.Lymphadenitis is the most common manifestation.,2.Postnatal toxoplasmosis（2）immunosuppressed individuals:acute toxoplasmosis(severe disease):encephalitis,lymphadenitis,myositis,hepatitis,pneumonitis,myocarditis,nephritis,Host defenses,immunocompetent individu
15、als to acquire immunity in the third week after infection.tachyzoites begin to disappear from visceral tissues and may localize as tissue cysts in neural and muscular tissues.,immunosuppressed patients rupture of a tissue cyst may result in renewed multiplication of bradyzoites into tachyzoites,and
16、the host may die from toxoplasmosis.,Epidemiology,Toxoplasma gondii infection in humans is widespread throughout the world.But the incidence of infection in humans and animals vary in different parts of a country.Approximately half billion of humans have antibodies to T gondii.Only a small proportio
17、n(less than 0.1 percent)of people acquire infection congenitally.,Diagnosis,serologic examination:the Sabin-Feldman dye test.the indirect fluorescent antibody test(IFAT)the indirect hemagglutination test the latex agglutination test the enzyme-linked immunoabsorbent assay(ELISA),serologic or histocy
18、tologic examination.,Diagnosis,histocytologic examination:Biopsy.Necropsy.Inoculation of biopsy materials into laboratory mice and/or cell cultures.,serologic or histocytologic examination.,Diagnosis,other examinations:Immunohistochemical staining.Polymerase chain reaction(PCR).Electron-micrographic
19、 examination.Computed tomography techniques.,.serologic or histocytologic.,Control,Acute toxoplasmosis treatment:.Sulfonamides and pyrimethamine(Daraprim).Spiramycin-pregnant women.2.Sanitary disposal of the domestic cat feces.3.Dont eat raw meat,dont feed to cats with raw meat.4.Hands should be was
20、hed with soap and water after handling meat.5.Pregnant women dont bring up cat.,Treatment,No safe and effective therapy for toxoplasmosis.,immunocompetent individuals:general,supportive care,immunocompromised patients:.Drug treatment:spiramycin,paromomycin.Immunologic therapy:,Prevention,1.Wash your
21、 hands thoroughly with soap and water.2.Avoid drinking untreated water from lakes,streams,and other surface water bodies.3.Because of possible contamination with manure,peel or rinse fruits or vegetables to be eaten raw.4.Take extra care in selecting food and drink when traveling to places with poor
22、 sanitation.5.To treat contaminated water before drinking it,bring it to a rolling boil for at least one minute to kill oocysts or remove them with a filter with an absolute pore size of one micron or smaller.,Cryptosporidium Tyzzer,Morphology,Oocyst:contains 4 porozoites.,Life Cycle,A scanning elec
23、tron micrograph of a broken meront of Cryptosporidium showing the merozoites within.(From:Gardiner et al.,1988,An Atlas of Protozon Parasites in Animal Tissues,USDA Agriculture Handbook No.651.),Life Cycle,Summary:Completing its entire life cycle within a single host.A lot of mammals could act as ho
24、st.Two autoinfective cycles:the first by continuous recycling of Type I meronts and the second through sporozoites rupturing from thin-walled oocysts.Infection occurs by the ingestion of oocysts in contaminated water,food,or by the fecal-oral route.Parasitic site:The ileum,the duodenum and large int
25、estine,the stomach,biliary and pancreatic ducts,and respiratory tract.,Pathogenesis,Arrows point to the Cryptosporidium in the microvillus border,A scanning electron micrograph of Cryptosporidium lining the intestinal tract.(From:Gardiner et al.,1988,An Atlas of Protozoan Parasites in Animal Tissues
26、,USDA Agriculture Handbook No.651.),Pathogenesis,An electron micrograph showing several stages of Cryptosporidium(two are marked with asterisks)on the intestinal epithelium of a sheep.(From:Gardiner et al.,1988,An Atlas of Protozoan Parasites in Animal Tissues,USDA Agriculture Handbook No.651.),Path
27、ogenesis,Pathogenesis,1.Cell death is a direct result of parasite invasion,multiplication,and extrusion or 2.Cell damage could occur through T cell-mediated inflammation,producing villus atrophy and crypt hyperplasia.,Epithelial cells are damaged by one of two models:,Either model produces distortio
28、n of villus architecture and is accompanied by nutrient malabsorption and diarrhea.,Clinical Manifestations,The most common symptom is watery diarrhea.,immunocompetent individuals:watery diarrhea are self-limiting,rarely more than two weeks.,immunosuppressed individuals:watery diarrhea are serious,l
29、ong-lasting,and sometimes fatal.,You could still carry the Crypto parasites after healing.As a carrier of Crypto,you could infect other people.If your CD4+count later drops below 200,your symptoms may reappear.,Detection and Diagnosis,The modified acid-fast stain:traditionally used,When stained usin
30、g an acid-fast method,oocysts of Cryptosporidium parvum stain bright red or purple,as seen in this preparation.,Cryptosporidium oocysts.(Original image from a Japanese language site tentatively titled Internet Atlas of Human Parasitology.),Detection and Diagnosis,The modified acid-fast stain:traditi
31、onally used,Immunologic methods:.The enzyme-linked immunoabsorbent assay(ELISA).The antibody immunofluorescence assay(IFA).,New genetic methods:.PCR(Polymerase Chain Reaction).DNA-based detection methods.,Epidemiology,Source infection:infected human or animal.Infection occurs by the ingestion of ooc
32、ysts in contaminated water,food,or by the fecal-oral route.Breakout by drinking contaminated water.,Incident rate of Cryptosporidium parvum is 0.6%-4.3%in all diarrhea patiens.,Pneumocystis carinii,Pneumocystis carinii Pneumonia(PCP),Morphology,1.Trophozoite,滋养体,2.Cyst intracystic bodies,包 囊,Pneumoc
33、ystis carinii stained with polychrome methylene blue.Intracystic bodies are visualized,but the cyst wall is not stained.Bodies measure 1 to 2 m in diameter.(From Hughes WT;Pneumocystis carinii pneumonia.In Kelley VC(ed):Practice of Pediatrics.Vol.2.JB Lippincott,Philadelphia,1977,with permission.),L
34、ife cycle,Summary:,1.Parasitic site:the lung2.Infected stage:cyst 3.Model of transmission:by inhalation(via airborne transmission),Life cycle,Pathogenesis,.the organism occurs in massive numbers,filling the alveolar spaces and eliciting an active response of the alveolar macrophages and phagocytosis
35、.the infection results in impaired ventilation and severe hypoxia.,Low power magnification of lung section showing alveoli filled with foamy vacuolated material and infiltration of the alveolar septa.,CLinical Manifestations,immunocompetent individuals:general,no discernible disease.,immunocompromis
36、ed patients:bilateral diffuse pneumonitis/PCP:tachypnea,respiratory distress,arterial oxygen tension is low,arterial pH usually increased,and carbon dioxide retention usually does not occur.In premature and debilitated infants:.In the immunodeficient child or adult:,Host Defenses,.Pneumonitis tends
37、to occur in patients with impaired cell-mediated(eg.,CD4+T-lymphocyte counts 200/mm3),.and it is a major infection in patients with the acquired immune deficiency syndrome(AIDS).,In the immunocompetent host,immune mechanisms are able to control growth or spread of the organism by a probable combinat
38、ion of cell-mediated and humoral immunity.In the immunocompromised host,these mechanisms fail.,Diagnosis,Method Efficiency lung biopsy.90%inducement of sputum.30-90%bronchoalveolar lavage.50-95%needle aspiration of the lung.,to find cyst/trophozoite.,Gomoris methenamine silver stain of lung biopsy s
39、howing distinctive cyst walls.,Giemsa stain of lung impression smear showing intracystic bodies and presumptive trophozoites.,Diagnosis,Epidemiology,Pneumocystis carinii infection is nonseasonal and worldwide.70 percent of healthy individuals may have humoral antibody to P carinii.,Control,the disea
40、se can be prevented by prophylactic administration of trimethoprim-sulfamethoxazole,aerosolized pentamidine or dapsone.,Four drugs currently available for therapy of P carinii pneumonitis are pentamidine isethionate trimethoprim-sulfamethoxazole-preferred drug atovaquone trimetrevate,Strongyloides s
41、tercoralis,Morphology,Free-living adult worm:2.Parthenogenetic adult female worm:,3.Rhabditiform larva:4.Filariform larva:,5.Egg:,Life Cycle,1.free-living(in the soil):,2.Parasitic-living(in human intestine):,Free-living adult worm(,),Eggs,Rhabditiform larva,Parthenogenetic adult female worm,Eggs,Rh
42、abditiform larva,Filariform larva,Life Cycle,Life Cycle,Summary:,It has free-living(in the soil)and Parasitic-living.Infective stage:filariform larva.Model of infection:direct penetration of the skin.Parasitic site:adult females-the intestine mucosa,filariform larva-all tissue.It has autoinfection i
43、n immunodeficient host.,Clinical Disease,In immunocompetent host:asymptomatic or chronic infection.In immunodeficient host:disseminated strongyloidiasis.,Diagnosis,To find larvae in stool,sputum or duodenal aspirates.,Control and Treatment,Resemble hookworm.Thiabendazole and ivermectin.,Opportunistic parasite-some symbiotic protozoa are nonpathogenic or cause only limited clinical symptoms in immunocompetent host,but produce serious symptoms in immunodeficient persons.,
