Clinical Parasitology Dr. Mohiedd ī n Abdul-Fattah
Introduction -Definitions • Parasitism )
(: a relationship in which one organism
(parasite) lives at the expense of another (host). • Endoparasite ) (: a parasite which lives within the body of the host, e.g. protozoa and helminthes • Ectoparasite ) e.g. insects
(: lives on the body surface of the host
• Habitat ) (:the organ in which the parasite exists in the body of the host. • Final host) parasite. parasite. •
(:harbors the adult or sexually mature
Intermediate host : ) (harbors the immature stages or asexual stages of a parasite that show significant development.
Definitions • Reservoir host : ) ( the animal that holds the same stage of the same species of a parasite that man holds and contributes to the perpetuation of the parasite life cycle in nature. • Transport host (Paratenic): the intermediate host that carries the larva of the parasite without significant development (with arrested development). development). • Vector :) ) an arthropod or a snail IH that directs a parasite to a certain host within certain conditions. • Exit stage :) (The stage that gets out of the host and aids in diagnosis (diagnostic stage). • Inlet stage or infective stage :) (The stage that enters the host and causes the infection.
• Auto-infection Auto-infection :) (when a host infects himself; this occurs when the infective stage is the exit stage. • Patent infection: infection with an exit stage out of the host in clinical sample and which contributes to perpetuation of the life cycle. • Non patent infection: infection without exit stage out of the host. • Routes of infection or entry of the infective stages : 1. By ingestion of: larva, egg, cyst or oocyst in contaminated foods & drinks. 2. Entry Entry of larva, trophozoi trophozoites, tes, sporozoite sporozoitess or cysts through through conta contact ct with with skin ulcer and abrasion, or by active penetration, or via inoculation by an insect. 3. Through epithelia of mucosal surfaces, surfaces , of the eye eye,, olfactory epithelium , respiratory, or via urogenital tracts. 4. Conge gen nit itaal transmission. 5. Blood transfusion.
Host-Parasite Relationship 1. Infection: means establishment of a parasite existence within the host accompanied or not with its development and reproduction. This means host parasite interaction passes through 4 stages: initial contact (contamination ( contamination), ), establishment within suitable habitat, development and lastly reproduction reproduction.. 2. Imm mmu une re respon ons se: •
A. B. C. D.
When a parasite antigens come into contact with the host immune system (cells), these cells interact with the parasite antigens (structures or excretion and secretions) to induce: Parasite immune-evasion immune-evasion,, Host immune-protection (immunity or resistance) Host immune-pathogenesis or aid in immune-diagnosis immune-diagnosis..
Host-Parasite Relationship 3. Dise Diseas ase e (P (Pat atho hoge gene nesi sis) s):: • The occurrence of infection does not necessarily imply the occurrence of disease. • Disease only occurs if the anatomical and/or the physiological integrity of the host were broken down. • If infection leads to this breakdown it induces disease. Disease is usually presented by signs and symptoms. • Opportunistic infection: infection that does not cause disease in immune competent host, but if the host immunity is impaired it does.
Host-Parasite Relationship • How do Parasites damage their hosts? 1. Comp Compet eting ing for for nutr nutrie ient nts s (e.g. (e.g. latum).
Hookw Hookworm orms s and D.
2. Disrup Disrupting ting tissue tissues s (e.g. (e.g. Hydati Hydatid d disea disease, se, myia myiasis sis and Tungiasis). 3. Dest Destro royi ying ng cell cells s schistosomiasis).
(e.g. (e.g.
mal malar aria, ia,
hoo hookw kwor orm, m,
and and
4. Mecha Mechani nica call blo block ckag age e (e. (e.g. g. Ascar Ascaris) is).. 5. Seve Severe re dis disea ease se oft often en inflammatory response.
is is
indu induce ced d
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imm immun une e
/
Parasites studied in this course • Helminthes:
•
1. Platyh Platyhelminth elminthes es
1. Biolog Biology: y: Brief Brief life life cycl cycle: e:
• Trematoda
•
• Cestoda
Which type of host man acts as? Are there reservoir hosts?
•
Habitat in man
2. Nemath Nemathelminth elminthes es
•
Exit stage
• Nematoda
Every endoparasite will be studied through these points
2. Epid Epidem emio iolo logy gy:: •
Geographical Distribution
3.Protozoa
•
Transmission:
• Amebas
Reservoir and intermediate hosts
Infective stages and Modes of infection
• Flagellates
3. Host-p Host-para arasit site e rela relatio tionsh nship ip
• Coccidia
•
4. Art Arthro hropode podes s
The induced disease:
4. Diagnosis 5. Treatment
Trematoda Dr. Mohiedd ī n Abdul-Fattah
Trematodes According to Habitat • Intestinal Trematodes :
1. 2. 3. 4. • 1. 2. 3.
Heterophyes Metagonimu imus Fasciolops opsis Echinostoma Liver trematodes : Fasciola. Clonorchis Opistorchis his
Lung trematodes: 1. Paragonimus. • Blood trematodes: 1. Schistosoma •
Heterophyes heterophyes I. Biology • Final host: Man, dogs and cats • Habitat : between villi in small intestine
• Exit stage: mature egg in stool of FH. • Morphology: 1.5 x 0.5 mm, pear like trematode.
II. II. Epid Epidem emio iolo logy gy • •
1. 2. 3. 4.
Geographical distribution: Egypt around Borollos and Menzella lakes , Palestine Europe and Far East.. Transmission: Inte Interm rmed ediat iate e host host (I.H. (I.H.): ): Pir Piren enel ella la con conic ica a is 1st I.H. and Bolty and Boory fish are 2nd I.H. Reservoir ho hosts: dogs and cats act as final reservoir hosts. Infective st stage: Encysted metacercaia in fish muscles Mode of infec ecttion: Ingestion of insufficiently cooked or under salted fish infected with Encysted metacercaria
Host parasite relationship 1. Mild Mild inf infec ecti tion on is is almo almost st asy asymp mpto toma mati tic c
2. Heav Heavy y infe infect ctio ion n indu induce ces s loca locall inte intest stin inal al inflammation and intermittent diarrhea 3. The The smal smalll egg eggs s may may be be ino inocu culat lated ed into into the blood vesels and migrate to heart and brain resulting in embolic manifestations. 4. Myoc Myocar ardi ditis tis and and neur neurol olog ogic ical al comp complic licati ation ons s are reported
IV. Diagnosis • Detection of eggs in stool. • Egg charcteristics: 1.30 x 15 µm,
2.oval, thick shelled, 3.yello 3. yellowish wish brown, operculated 4.mature 4. mature (contains (contains developed larva [miracidium]).
V.
Treatment
• Praziquantel; 25 mg/kg/8h PO for one day
VI .
Control
• Adequate salting and cooking of fish and and snail control. •
Proper disposal of human waste and eradication of stray dogs.
•
Mass examination and treatment of fishermen and health education
Trematodes (flukes) worm
Heterophyes
Man
Final host
Reservoir
Cats, dogs and birds
Habitat
In between villi of small intestine
Exit stage
Egg: mature, operculate, thick-shelled, thick-shel led, ovoid, golden yellow yellow,, 30X15 µm
Intermediate host
1st : Pirenella snail in brackish water 2nd : fish (Bolty & Boury)
Infective stage
Encysted meatcercaria meatcercaria fish muscles underneath scales
Mode of infection
Ingestion of encysted encysted metacercaria metacercaria in under-salted or under-cooked under-cooked fish
Disease
1. Enetritis 2. Myocarditis Myocarditis due to embolised embolised eggs
diagnosis
1. Detection of eggs in stool.
Treatment
Praziquantel
Control
1. Thorough cooking of fish 2. sanitary disposal of fishermen excreta.
Fasciola hepatica and F. gigantica I. • • A. B.
BIOLOGY Man, sheep and cattle act as final hosts. Diagnostic morphology: 3-6 x1.2 cm, leaf like hermaphrodite with with ante anteri rior or coni conica call part part and and post poster erio ior r elongated part C. havi having ng para parallllel el later lateral al bord border ers s in in F. F. gig gigan anti tica ca or converging in F. hepatica. • Habitat in the final host: The biliary tracts of the liver. • Exit stage: Immature egg.
Lymnaea snail
Simple tailed cercaria
Fasciola egg E. metacercaria on grass
Fasciola hepatica
II. Epidemiology • • 1.
2. 3. 4.
Geographical distribution: Egypt and sheep and cattle raising countries. Transmission: Inte Interm rmed edia iate te host host (I.H. (I.H.): ): Lymn Lymnaea aea is 1st I.H. and vegetable is 2nd I.H. Reservoir ho hosts: Sheep and cattle act as final reservoir hosts Infective st stage: Encysted metacercaia Mode of infec ecti tio on: Ingestion of raw vegetable contaminated with encysted metacercaia
III.
Host-Parasite Re Relationship
• Immune responses : Humoral: Early development of IgM, IgE, IgE, IgG1 IgG1 and IgG2 to to ES Fasciola Ags. These are of limited role in protection. Cellular: Peripheral eosinophilia and lymphocytosis. The response in the invasive phase is due to Th1 cytokines. Th2 type cytokines predominate when the worms reside in the bile canaliculi. • Effector protective mechanisms against JF : The toxic NO produced by IFNγ activated macrophages. ADCC; IgG1, IgE, IgA, IgG2a dependent macrophage, eosinophil, and platelet cytotoxicity This leads to release of the killing granules: ECP, MBP and eosinophil peroxides.
III. • •
•
•
•
Host-Parasite Re Relationship
Pathogenesis: Acute fasciolitic hepatitis during the migratory phase in liver. It is manifestecd by fever, eosinophilia and allergic features. Chronic biliary fascioliasis when the worm resides in the biliary passages causing duct hyperplasia due to excessive proline secretion and biliary obstruction This This→ → jaun jaundi dice ce and and haem haemat atob obililia ia → anae anaemi mia. a. The The wor worm m secreted proline also contributes to anaemia via its inhibitory effect on erythropioesis. Fasciolitic pharyngitis (Halzoun) caused by the presence of adult in the pharynx after eating infected raw sheep liver infectd with adults..
Pathogenesis
Juvenile Fasciola migrating in liver parenchyma during invasive stage
The surface spines of Fasciola damage the biliary epithelium during chronic stage
IV. • • 1. 2. 3. 4. 5.
Diagnosis
Detection of eggs in stool. Direct and conc. Egg charcteristics: thin walled, 140 x 70 µm, ovoid, yellowish br brown, Operculated, imma immatu ture re (do (does es not not con conta tain in developed larva [miracidium]).
Indirect diagnosis Serodiagnosis
(sp. during invasive stage) • IFAT (T.S of adult worm) or ELISA (ES ags). Imaging:
CT sonography
V.
Treatment
• Triclabendazole (10 mg/kg PO for one dose) or Mirazid.
VI.
Control
1. Adeq Adequa uate te wash washin ing g of of veg veget etab able le..
2. Mass Mass trea treatm tmen entt of of Res Reser ervo voir irs. s. 3. Sani Sanita tati tion ons s of of sla slaug ught hter er hous houses es.. 4. Control of snails.
5. Prop Proper er disp dispos osal al of of hum human an wast waste. e.
Trematodes (flukes) worm
Fasciola
Man
Final host
Reservoir
Sheep and cattle
Habitat
Biliary passages
Exit stage
Egg: Immature, operculate, thin-shelled, yellowish brown, 140 X70 µm
Intermediate host
1st : Lymnaea snail in fresh water 2nd : vegetable (watercress)
Infective stage
Encysted meatcercaria on vegetable
Mode of infection
Ingestion of encysted metacercaria in vegetable
Disease
1. Acute stage: fever fever 2. chronic stage: jaundice, jaundice, anemia 3. Halzoon
diagnosis
1. Detection of eggs in stool & in duodenal aspirate (DA), (DA), 2. Detection of specific abs & ags in serum
Treatment
Triclabendazol riclabend azol orally o rally..
Control
1. Thorough wash of vegetable 2. snail control 3. cooking of liver
Paragonimus westermani I. Biology Final
host: Humans, dogs, cats, rodents and pigs.
Habitat:
Encapsulated in the bronchioles of the lung
Exit
stage: immature eggs passed in feces and sputum.
Basic
morphology and life cycle: adult thick bodied 4 mm x 8 mm.
Adult
II. Epidemiology Distribution:
worldwide but more confined in oriental countries such as Japan. Reservoir hosts: Dogs, cats, rodents and pigs. Intermediate hosts: 1 st IH snail; Semisulcospira or Thiara and 2 nd fresh water cructaceans. Infective stage: Encysted metacercaria in gills and muscles of crustaceans (crabs). Mode of infection: ingestion of encysted metacercaria in undercooked crustacean.
III. Host Parasite Relationship
Early symptoms cough with blood tinged sputum. Low grade fever Difficult to distinguish from pneumonia and tuberculosis. sites may Ectopic include: abdominal wall, heart, lymph nodes and nervous system.
T.S. of lung containing cont aining encapsulated adult
Eggs in m. LN with granulomas
IV. Diagnosis Clinical
picture with eosinophila in endemic areas.
Detection
of eggs in sputum or feces.
Serology
for ectopic sites DIG or ELISA.
Imaging:
plain x-ray.
V.Treatment •
Praziquantel; 25mg/kg/8h PO for 2 days
•
Bithionol ; 20 mg/kg/12h Po daily for 14 ds.
VI.Control •
Health education.
•
proper cooking of crabs and crayfish .
Schistosoma mansoni & S. hematobium • BIOLOGY Man only acts as final hosts. Diagnostic morphology: sex separate flukes. Male is ~ 20 mm covered with tubercle, flattened dorso-ventrally and folded on it self to form gynecophoric canal. Female is ~ 26 mm cylindrical and smooth carried by the male. Habitat in the final host: Inf. mesenteric veins draininnig large intestines in S. mansoni. vesical plexus draining urinary bladder in S. hematobium. Exit stage: mature egg in stool ( S.mansoni ) and in urine ( S. hematobium).
II. Epidemiology
Geographical distribution: Africa, south America, Middle East and Portugal.
Transmission:
1. Intermediate Intermediate host host (I.H.): (I.H.): The snails snails;; Biomphalari Biomphalaria a is I.H. of S.mansoni and Bulinus is I.H. of S hematobium. 2. Reservoir Reservoir hosts: hosts: No No animal animal reservo reservoir ir hosts. hosts. 3. Infective Infective stage: stage: Free Free swimming swimming cecaria cecaria in fresh fresh water
4. Mode of infection: infection: free cercaria penetrates penetrates skin
III. HostHost-Par Parasi asite te Rela Relatio tionsh nship ip • Immune responses:
A. Early cell mediated mediated immunity before egg laying.
B. Late Late humo humora rall anti antib body ody dependent cell mediated cytotoxicity (ADCC).
• Pathogenesis 1. Cercar Cercaria iall derm dermati atitis tis (swim (swimmer mer's 's itch): itch): maculopapilar rash in areas of skin exposed to cercaria S. haematobium, S.mansoni and to avian schistosome infection. – It is due to immediate or late hypersensitivity reaction that begins 1-2 days after exposure. It more common among the newcomers to endemic areas. 2. Acute Acute schist schistosom osomias iasis is (Takay (Takayama ama fever) fever):: fever occurs weeks after the primary infection. – It is due to massive IFN-γ IFN-γ and TNFTNF-α cytokines of TH1 response priming for granuloma formation around the eggs.
•
Pathogenesis
1. Chronic Chronic schisto schistosomia somiasis: sis: occurs occurs due to TH2 cytokine response that strongly expands the granuloma size. 2. The cellula cellularr componen components ts of this granul granuloma oma are are plenty of eosinophils plus macropages, fibroblasts and lymphocytes. Eosinophil mediated chronic inflammatory reactions predispose to fibrosis around the eggs in tissues of the affected organs. 3. Downregulti Downregultion on of of fibrosis fibrosis is associa associated ted with with diminshed TH2 cytokines and increased TH1 cytokines.
Pathogenesis
Adult in lung lung Planorbis
Cercarial dermatitis
•
a) b)
a) b)
• Pathogenesis
The manifestations in the chronic stage include: In S. mansoni: Colo Coloni nic c pol polyp yps s with with bloo bloody dy diar diarrh rhea ea Periportal fibrosis → portal hypertension with hematemesis and splenomegaly. In S. hematobium: Cyst Cystit itis is (sq (sq cell cell carc carcin inoma oma), ), uret ureter erit itis is wit with h hemat hematur uria. ia. Uret Ureter eric ic stri strict ctur ure e induc induces es hydr hydron onep ephr hros osis is
c) CNS CNS dis disor orde ders rs and and cor core e pul pulmo monal nale e occ occur ur earl earlie ierr in in S.hematobium due to direct passages of eggs from bladder and ureteral veins into systemic veins than in S. japonicum and mansoni. d) In the the lat latte ters rs they they occur occur later later afte afterr the the onset onset of portosystemic shunts.
1. esopha esophagea geall varices; 2. paraesopha paraesophageal geal varices; 3. gastrorena gastrorenall shunt; 4. splenorena splenorenall shunt; 5. inferio inferior r mesenteric, hemorrhoidal, & internal iliac veins 6. mesocaval mesocaval shunt; shunt; 7. intrahepati intrahepatic c portosystemic shunt; 8. Sappey's Sappey's veins
Portosystemic shunts
Pathogenesis
Colonic polyps endoscopy
Periportal fibrosis Periportal fibrosis
B splenomegaly Polyposis post mortem
Esophageal varices
Pathogenesis (hematobium)
Rt unilateral
hydronephrosis
Ureteral dilatation due to calcified stenosis of orifices
Fetal head appearnce due to intense calcification of bladder→
Squamous cell carcinoma of bladder. Ova of hematobium are often found in such tumour
IV. Diagnosis Detection
of eggs in stool (S.mansoni) or in urine (S.hematobium).
Egg o
o
o
characteristics :
S. mansoni: Ovoid non-operculated, 140 x 70 µm, yellowish brown with lateral spine and mature (contains miracidium). S. hematobium: spindle shaped, non-operculated, 140 x 70 µm, yellowish brown with terminal spine and mature (contains miracidium). Serology in prepatent and chronic infection to detect specific schistosome antigens and antibodies
V. Treatment • Praziquantel; 40 mg/kg PO with food divided into 2 doses separated by 4-6 hours for S. mansoni and hematobium .
VI.
Control
1. Avoid voidin ing g swi swimm mmin ing g in in fre fresh sh wate waterr. 2. Prop Proper er disp dispos osal al of huma human n was waste te.. 3. Cont Contro roll of snai snails ls and and heal health th educ educat atio ion. n. 4. Mass tr treatment
Trematodes (flukes) worm
Schistosoma mansoni
Schistosoma hematobium
Man
Final host
Reservoir
none
Habitat
Veins draining large intestines
Veins draining urinary tracts
Exit stage
mature, ovoid egg with lateral spine 150X70µm
Mature, ovoid, egg with terminal terminal spine,150X70µm
Intermediate host
Biomphalaria snail
Bulinus snail
Infective stage
Free swimming cercaria
Mode of infection
Free cercaria penetrate skin immediately after bathing in water
Disease
1.Cercarial dermatitis, 2.Katayama fever 3.Bloody diarrhea, 4.Anemia 5.Periportal fibrosis: a)Portal a)Portal hypertension, hypertension, b)Splenomegaly c)Esophageal varices., d)Ascites
1.Cystitis, ureteritis 2.Dysuria and hematuria. 3.Anemia 4.Carcinoma 4.Carcinoma of U. bladder
diagnosis
Detection of egg in stool, detection of specific abs & ags in serum
Detection of egg in urine, detection of specific abs & ags in serum
Treatment Control
Oral Praziquantel 1.Mass treatment of human cases. 2.Snail control3.Sanitary control3.Sanitary disposal of sewage