parasitology review 2017
TRANSCRIPT
Parasitology Review2017MARGIE MORGAN
Clinical presentation Travel history or poor sanitation put you at the highest risk for parasitic infection
Infections associated with sporadic symptoms Poor immune status higher risk Dysentery not common (amebiasis) Most usual symptoms:
◦ Abdominal pain, cramping, long term nausea, and malaise, mucous in stool, and +/- fever
Laboratory DiagnosisCurrently based on microscopic exam, and molecular panels for the most common (select) parasites
◦ Stool (PCR applicable)◦ Non-stool
◦ Perianal specimen◦ Sigmoidoscopic specimen◦ Duodenal aspirates◦ Liver abscess◦ Sputum◦ Urine◦ Urogenital
◦ Blood◦ Tissue
Alternative methods:◦ Serology◦ Fluorescent stains
Two-vial collection kit for Stool
10% formalin Concentration with ethyl acetate to eliminate fecal debris
Wet mount, DFA staining and NAAT
Helminth eggs, larvae, microsporidia, and protozoan cysts
PVA with fixative Polyvinyl alcohol Permanent stained smear
◦ Trichrome stain
Protozoan trophozoites and cysts
Mercury based fixatives phased out for safety – Zinc fixatives are now used
Most Common Pathogens Protozoa
◦ Intestinal & urogenital◦ E histolytica, Blastocystis hominis, Giardia lamblia, Dientamoeba fragilis,
Balantidium coli, Cryptosporidium sp., Cyclospora sp, Cyclospora, Cytoisospora(Isospora) belli, and Microsporidia
◦ Blood & tissue◦ Plasmodium, Babesia, Trypanosomes◦ Toxoplasma gondii, Leishmania◦ Naegleria, Acanthamoeba, Balamuthia
Helminths◦ Nematodes
◦ Ascaris, Trichuris, hookworm, pinworm, and Strongyloides◦ Cestodes
◦ Taenia, Hymenolepis, Diphyllobothrium◦ Trematodes
◦ Fasciola, Fasciolopsis, Schistosoma, Paragonimus, Clonorchis
PROTOZOA Amebae (found in stool)
◦ Entamoeba coli ◦ Entamoeba histolytica ◦ Endolimax nana◦ Iodamoeba butschlii◦ Dientamoeba fragilis
Flagellates (found in stool)◦ Giardia lamblia◦ Chilomastix mesnili
Ciliates, Coccidia, Blastocystis◦ Balantidium◦ Cryptosporidium◦ Cystoisospora (Isospora) belli◦ Sarcocystis◦ Cyclospora◦ Microsporidium◦ Blastocystis hominis
Blood-Borne Protozoa◦ Babesia◦ Leishmania◦ Trypanosoma brucei◦ T. cruzi◦ Plasmodium
Other ◦ Toxoplasma◦ Naegleria fowleri◦ Acanthamoeba
Protozoa Found in Stool: Amebae pathogen
Intestinal amoeba Entamoeba coli
Entamoeba histolytica/dispar
Entamoeba hartmanni
Endolimax nana
Iodamoeba butschlii
Entamoeba histolytica/dispar E. histolytica is a pathogen and E. dispar is a nonpathogenic species that can also occur in the large intestine. Morphologically indistinguishable◦ Antigen testing or molecular methods to distinguish the two species
E histolytica◦ Cysts = infectious form ◦ Trophozoites = invasive form◦ Cysts found in contaminated water and poor sanitation◦ Colon biopsy shows “flask-shaped” ulcer with Trophs◦ Non-intestinal disease = extra-intestinal amebiasis (liver
abscess) with Trophs◦ Serology can be useful
Entamoeba histolytica/dispar
Cysts @10-12 umIn diameter Up to 4 nuclei in the cyst
Peripheral chromatin is evenClean chromatin
Bulls-eye nucleoli
Entamoeba histolytica/dispar
Trophozoites & Cysts
Trophozoite with ingested rbcs
Elongated chromatoidbody
Amebic abscess
Flask-shaped ulcer of intestinal amebiasis
Amebic liver abscessEntamoeba histolyticaSerology – high % positive in extra-intestinal cases
Entamoeba coli cyst and trophozoiteConsidered a commensal in the intestine
Cyst @ 20 – 25µmUp to 8 nucleiShed from hostLives in environment
Trophozoite is the invasive form that invades the intestine
Single nucleus with a large karyosome located eccentrically irregular chromatin ring.The cytoplasm appears dirty and vacuolated
Entamoeba coli – important to differentiate from the pathogen E. histolytica
Trophozoites & Cysts
Cysts usually15-25µm, with 5or more nucleivisible.
Endolimax nana trophozoite
Cysts – 8-10 µm in size, one nucleusMostly thought to be a non-pathogen, seen in stool specimens from HIV/AIDS patients, some literature suggesting it can cause intermittent or chronic diarrhea
Iodamoeba butschlii cysts, 10 – 12 µm insize with starch inclusion (glycogen mass)
Iodine preparation – glycogen inclusion stains with iodine
Flagellates Giardia lamblia Dientamoeba fragilis Trichomonas vaginalis
Protozoa Found in Stool: Flagellates
Pathogen
Giardia lamblia Contaminated water, undercooked foods
Mild diarrhea to severe malabsorption
Foul, watery diarrhea Day-care center outbreaks reported, traveler’s diarrhea
Cysts/trophozoites may be seen in stool, but can be hard to find; Fluorescent stains and NAAT for more sensitive detection
Duodenal aspirations can be used if stool specimens are negative
TROPHOZOITE“falling leaf” motility
CYSTS
Giardia lamblia trophozoiteWaxing and waning symptomsCan be irregularly shed in stool materialmaking antigen and molecular methods necessary for detection
Russia & Mexico-Hot beds of infection
Confined to intestine
Flagyl (Metronidazole) is drug of choice
Giardia lamblia cysts
Clearing between the cell wall and the cell membrane
Giardia lamblia cysts
Giardia lambliaonly invades intestinal tissue
Chilomastix mesnili cyst Nonpathogen Mimics Giardia lamblia cyst – except for clear space at end of cyst
Internal structure looks like “shepherd’s crook” or safety pin
C. mesnili trophozoite
Dientamoeba fragilis Diarrhea, anal pruritus Only a trophozoite stage 5 – 15 µm (No cyst) Usually two nuclei visible in the trophozlite Can occur in Co-infection with Enterobius (pinworm)
Trichomonas vaginalis Urogenital protozoan Scant, watery vaginal discharge
Four flagella, short undulating membrane
Protozoa Found in Stool: Ciliates, Coccidia, Blastocystis
Ciliates Balantidium coli
◦ Mainly in swine◦ Contact with swine & poor hygiene◦ Only ciliate that’s pathogenic to humans◦ Similar disease as amebiasis, but extraintestinal invasion
rare◦ Largest (50-200 um) trophozoite; surface covered with
cilia; macronucleus◦ Cyst 40-60 um◦ Readily identified in fresh, wet mounts◦ Can cause flask shaped ulcer in intestine
Intestinal Sporozoa (coccidia)
Isospora (Cystoisospora) Cryptosporidium Cyclospora Sarcocystis
Isospora(Cystoisospora) belli
Contaminated food/water, oral-anal Found most commonly in HIV/AIDS Infects intestinal epithelium Malabsorption syndrome mimicking giardiasis
PositiveModified acid fast stain
Cryptosporidium sppC. parvum and C. hominis
Contaminated water Resistant to usual water-purification procedures (chlorination, ozone)
Daycare center outbreaks (fecal-oral), swimming pools
Watery diarrhea; more severe in AIDS
Cryptosporidiosis: DiagnosisPartial Acid Fast Stain Positive
Not detected in routine O & P exams (left)Requires modified acid-fast stains for detection, oocysts measure4-6 µm , Antigen, DFA and Molecular assays aid detection.
PAF stain Positive
Direct Fluorescence Antibody stain – Cryptosporidium spp
Molecular assays (PCR) and Enzyme immunoassay for antigen available.
Giardia
Cryptosporidium
Combo stain for Cryptosporidiumand Giardia lamblia
Cryptosporidia in intestine
Cryptosporidia in the intestine - locatedjust below the plasma membrane
Cyclospora cayetanensis Contaminated fruits and vegetables – particularly ones with plant hairs
Watery diarrhea; fatigue, anorexia, weight loss, flu like symptoms. More severe in immune suppressed, can last for months
Infects upper small bowel Treatment Oral Trimethoprim/sulfamethoxazole Found in vacuoles in cytoplasm of jejunal epithelium, villous atrophy, crypt hyperplasia
Cyclospora cayetanensis
Modified acid fast positive8-10 microns
UV autofluorescence
Also positive on Calcofluorwhite stain
Microsporidia Obligate intracellular fungal parasite Enterocytozoon and Encephalitozoon species most common genera
Primitive eukaryotic organism (fungi) Infection by ingestion of spores Chronic diarrhea in AIDS patients Myositis, hepatitis, peritonitis, keratitis, gastrointestinal and biliary tract
Microsporidia-Diagram of detailed internal sporestructures
Positive on modified Trichrome and Calcofluor white stains
-Longer staining times will eventually allow for it to work its way into the spore
Blastocystis hominis (algae)
Small #s: can be commensal Large #s: may be pathogenic Contaminated food and H20 Traveler’s diarrhea
Iodine wet mount
Nuclear blobs Around the periphery Trichrome
stain
None; None; self resolving. self resolving.
Maltese cross in rbcMaltese cross in rbcHemolytic anemia, Hemolytic anemia, Jaundice, fever, Jaundice, fever, hepatomegalyhepatomegaly
Ixodes tickIxodes tickBabesia microtiBabesia microti
Pentosam; Pentosam; Pentamidine Pentamidine isethionate. isethionate.
Intracellular Intracellular (macrophages) (macrophages) leishmanial bodies leishmanial bodies with kinetoplastwith kinetoplast
Visceral leishmaniasis Visceral leishmaniasis (Kala-azar), (Kala-azar), granulomatous skin granulomatous skin lesions lesions Iraq/Iran/AfghanistanIraq/Iran/Afghanistan
Phlebotomine sandfly Phlebotomine sandfly Leishmania donovani Leishmania donovani
CNS: CNS: melarsoperolmelarsoperolNifurtimox and Nifurtimox and Benzonidazole. Benzonidazole.
Hemoflagellate in Hemoflagellate in blood or tissue. blood or tissue. C- or comma-shapedC- or comma-shaped
American American trypanosomiasis;trypanosomiasis;Chagas disease: Chagas disease: megacolon, cardiac megacolon, cardiac failure.failure.
Reduvid (kissing) bugReduvid (kissing) bugT. cruzi T. cruzi
Blood stage: Blood stage: Suramin or Suramin or petamidine petamidine isethionateisethionate
Hemoflagellate in Hemoflagellate in blood or lymph nodeblood or lymph node
African African trypanosomiasis; trypanosomiasis; Sleeping sicknessSleeping sicknessEncephalitis; cardiac Encephalitis; cardiac failurefailure
Tsetse flyTsetse flyTrypanosoma bruceiTrypanosoma brucei
TreatmentTreatmentDiagnosisDiagnosisDisease/SymptomsDisease/SymptomsTransmissionTransmissionOrganismOrganism
BLOOD BORNE PROTOZOA
Trypanosomes 2 Diseases
◦ Chagas disease (American trypanosomiasis)◦ Trypanosoma cruzi◦ Vector: Reduviid / Triatome (kissing) bug
◦ African sleeping sickness (African trypanosomiasis)◦ T. brucei (gambiense and rhodesiense)◦ Vector: Tsetse fly
Trypanosoma cruzi Chagas (American trypanosomiasis)
Vector: Reduvid/Triatoma (kissing) bug Trypomastigotes are the only stage found in the blood of an infected person; may be seen in CSF in CNS infections
Motile circulating trypomastigotes are readily seen on slides of fresh anticoagulated blood in acute infection but are rarely detectable by microscopy in chronic T. cruzi infection.
A typical trypomastigote has:◦ A large, subterminal or terminal kinetoplast, ◦ A centrally located nucleus, ◦ An undulating membrane, and◦ A flagellum running along the undulating membrane, leaving the body
at the anterior end. ◦ 12 to 30 µm in length.
Amastigote stage parasite may be seen in histopathology specimens from affected organs.
C-shape
Trypanosoma cruzi – TrypomastigotePeripheral blood – Giemsa stain
Reduvid bug
Amastigote of T. cruzi in cardiactissue
Trypanosoma brucei Sleeping sickness (African trypanosomiasis)
The two T. brucei species that cause African trypanosomiasis are indistinguishable morphologically
◦ T. brucei gambiense◦ T. brucei rhodesiense
A typical trypomastigote has:◦ A small kinetoplast located at the posterior end◦ A centrally located nucleus◦ An undulating membrane, and◦ A flagellum running along the undulating membrane, leaving
the body at the anterior end◦ 14 to 33 µm in length
Trypomastigotes are the only stage found in patients. kinetoplast
nucleus
TRYPANOSOMA BRUCEI GAMBIENSE
Leishmania Obligate intracellular parasite Vector: female sand fly bite Two forms of disease
◦ Visceral leishmaniasis (kala azar)◦ L. donovani
◦ Cutaneous leishmaniasis◦ L. tropica ◦ L. braziliensis
Leishmania
Leishmania – Clinical Disease
Cutaneous◦ Single or few chronic, ulcerating lesions;
many species◦ Latin America, southern Europe, Middle east,
southern Asia, Africa◦ Mucocutaneous in Latin America
Visceral◦ primarily L. donovani complex (Asia), L.
infantum/chagasi (Africa and Latin America), others
◦ Hepatosplenomegaly, anemia, cytopenias, systemic symptoms
◦ India, Bangladesh, Nepal, Sudan, and Brazil ◦ Important OI in HIV infection
Leishmania Diagnosis
◦ Biopsy of infected tissue (skin, bone marrow)◦ Multiple, tiny 2-5 um amastigotes within histiocytes◦ Distinct kinetoplast (bar-like structure adjacent to nucleus)
◦ PCR methods◦ Urinary antigens (visceral)
DDx of multiple tiny intracellular organisms◦ Leishmania – kinetoplast◦ Histoplasma – budding◦ Toxoplasma – somewhat curved, mostly extracellular
Leishmania amastigotes ◦ Macrophages filled with amastigotes (arrows),
several of which have a clearly visible nucleus and kinetoplast
Nucleus
Kinetoplast
Babesia Protozoan: B. microti, B. divergens Zoonosis (deer, cattle, rodents; humans accidental host) Transmission vector: Ixodes tick bite Infects red blood cells Found world-wide B. microti along the Northeast US
◦ Nantucket Island, Martha’s vineyard, Shelter Island
Malaria-like syndrome ◦ Fever but without periodicity, “B-symptoms”, hemolytic anemia,
hemoglobinuria, renal failure
Dx:◦ Blood smear examination
◦ Ring form only (mimics P. falciparum)◦ Tetrads (unlike P. falciparum)
Maltese cross(tetrads)
Ixodes tick
Babesia
Maltese cross forms
MALARIA Protozoan parasite Transmitted by the anopheles mosquito Endemic in tropical areas
Malaria Symptoms Fever pattern
ParasiteParasite DiseaseDiseasePlasmodium Plasmodium falciparumfalciparum
MalignantMalignant tertiantertian malariamalaria
P. vivaxP. vivax Benign Benign tertiantertian malaria malariaP. ovaleP. ovale Benign Benign tertiantertian malaria malariaP. malariaeP. malariae QuartanQuartan malaria malaria
Tertian = q 48 hours (every other day)Quartan = q 72 hours
Malaria Physical exam findings
◦ Fever◦ Splenomegaly◦ P. falciparum - most pathogenic species
◦ Jaundice◦ Hepatomegaly◦ Increase in respiratory rate◦ CNS involvement◦ Blackwater fever – hemolysis, renal failure
Diagnosis: peripheral blood smear Antigen screen (EIA) and NAAT
Malaria Primary distinction is P. falciparum and non-falciparum disease◦ P. falciparum = rapidly progressive and LETHAL (malignant
tertian fever), often chloroquine-resistant ◦ Non-falciparum = rarely cause severe manifestations, often
chloroquine sensitive
Relapsing malaria◦ Dormant hepatic phase can recur from liver
◦ Occurs only with P. vivax and P. ovale
MALARIA
Life Cycle of Plasmodium Species
Progression of the RBC formsof Malaria
Ring form Trophozoite Schizont
Gametocyte
Merozoites(ruptured schizont)
Plasmodium species Plasmodium falciparum Plasmodium vivax Plasmodium ovale Plasmodium malariae Plasmodium knowlesi – primates only
P. falciparumP. falciparum P. vivax, P. P. vivax, P. ovaleovale
P. malariaeP. malariae BabesiaBabesia
VectorVector MosquitoMosquito MosquitoMosquito MosquitoMosquito Ixodes tickIxodes tickRBC RBC Any RBCAny RBC Young RBC; Young RBC;
enlargedenlargedMature RBC;Mature RBC;Not enlargedNot enlarged
RingRing Multiple can Multiple can be seen; be seen; delicate; delicate;
“appliqu锓appliqué”
Rarely >1;Rarely >1;thickenedthickened
1-121-12Tetrads Tetrads
((Maltese Maltese crosscross))
DelicateDelicateRings onlyRings only
SchizontSchizont Rarely seenRarely seen Commonly seenCommonly seen ““rosette”rosette” nonenoneGametocyteGametocyte Banana-Banana-
shapedshapedRoundRound nonenone
Extra-RBC Extra-RBC formform
NoneNone NoneNone PresentPresent
Schüffner dotsSchüffner dots NoNo YesYes NoNoPigmentationPigmentation BrownBrown NoNoInfection rateInfection rate >2%>2% <2%<2% 5-10%5-10%Protective Protective polymorphismpolymorphismss
Hemoglobin S, Hemoglobin S, C,E, alpha and C,E, alpha and
beta thal, G6PDbeta thal, G6PD
Duffy negative Duffy negative (P. vivax)(P. vivax)
Dormant Dormant hepatic phase hepatic phase (relapse)(relapse)
NoNo YesYes NoNo
Malarial PreparationsThick smear Drop of blood on slide Water rinse to eliminate rbc’s Stain with Giemsa stain (not Wright-Giemsa) proper pH
Need the proper pH to stain the Schuffner’s granules
Concentrated to spot malaria parasites
Thin smear Feather edge smear For optimal morphology, stain with Giemsa (not Wright-Giemsa) stain with proper pH
Speciation of malaria Parasitemia (%)
Schuffner’s granules
P. ovale
Fimbriated edge
“Rosette” schizont
P. malariae
P. vivax
Amoeboid ring form
P.vivax – benign tertian malaria (fever every 48 hours), Duffy negative Red blood cell protects from Plasmodium invasion-African natives lack Duffy rbc antigen and this prevents them from P. vivax.Untreated infections last several years remaining dormant in the liver. Patients can survive years without treatment, but recurrent and chronic infection can lead to brain, kidney and liver damage
• P. falciparum-multiple ring forms per cell-accolade forms(ring forms on the edge of cell.-Banana gametocyte
Malignant tertian malariaBlack water fever
P. falciparum
High % parasitism
Accolade form
Banana gametocyte
P. falcipriumP. falciprium Non-Non-FalciparumFalciparum
BabesiaBabesia
VectorVector MosquitoMosquito MosquitoMosquito Ixodes tickIxodes tickRBC RBC All RBCAll RBC Young RBCYoung RBCRingRing 1-31-3
delicatedelicateRarely >1Rarely >1thickenedthickened
1-121-12TetradsTetradsDelicateDelicateRings onlyRings only
GametocyteGametocyte Banana Banana shapedshaped
roundround nonenone
Extra-RBC Extra-RBC formform
NoneNone NoneNone PresentPresent
PigmentationPigmentation BlackBlack brownbrown nonenoneInfection rateInfection rate >2%>2% <2%<2% 5-10%5-10%Protective Protective polymorphispolymorphismsms
Hemoglobin S, Hemoglobin S, C,E, alpha and C,E, alpha and beta thal, G-6-beta thal, G-6-PDPD
Duffy negativeDuffy negative
OrganismOrganism TransmissionTransmission Disease/Disease/SymptomsSymptoms
DiagnosisDiagnosis TreatmentTreatment
Toxoplasma Toxoplasma gondiigondii
Oral from cat fecal Oral from cat fecal materialmaterialor meator meat
Adult: flu like;Adult: flu like;congenital: congenital: abortion, neonatal abortion, neonatal blindness and blindness and neuropathiesneuropathies
Intracellular (in Intracellular (in macrophages) macrophages) tachyzoites tachyzoites
SulphonamidesSulphonamides, , pyemethaminepyemethamine, possibly , possibly spiramycin spiramycin (non-FDA)(non-FDA)
Other Protozoa - Toxoplasma
Toxoplasma gondii Coccidian protozoan House cat (kittens) = definitive host Infection from:
◦ Ingestion of infective oocysts from contaminated cat feces◦ Ingestion of improperly cooked meat from animals that serve as
intermediate hosts Symptoms
◦ Predilection for lung, heart, lymphoid organs, CNS/eye◦ Infectious mono-like; lymphadenitis, hepatitis, rash, encephalomyelitis,
myocarditis, chorioretinitis◦ Transplacental infection
◦ 1st trimester spontaneous abortion, stillbirth or severe disease◦ 2nd/3rd trimester CNS infections (epilepsy, encephalitis, intracranial
calcifications, MR, chorioretinitis, blindness, hearing loss), jaundice, rash◦ AIDS - Encephalitis; mass lesions in brain
Toxoplasma gondii Diagnosis
◦ Serology EIA◦ Anti-toxo IgM – congenital and acute infection; may persist
for months◦ Anti-toxo IgG – common; if positive, gestations safe from
intrauterine toxoplasmosis infection◦ PCR
Toxoplasma gondii
Toxoplasma gondii cyst Toxoplasma
in brain tissue stained tachyzoites
with hematoxylin and eosin
Free-living Amoeba Naegleria fowleri Acanthamoeba Balamuthia
Amoebic meningoencephalitis
Most common cause: Naegleria fowleri Granulomatous amoebic encephalitis or brain abscess: Acanthamoeba and Balamuthia
Clinical scenario: swimming or diving into fresh-water pools
Contact-lens keratitis Caused by Acanthamoeba Can be cultured on a “lawn of E. coli”
◦ Take corneal scrapings◦ Visible trail of ameba moving across plate ingesting
E. coli
Wright’s stain
HELMINTHS Nematodes (roundworms) Trematodes (flukes) Cestodes (tapeworms)
Nematodes Enterobius Ascaris Trichuris Necator and Ancylostoma (Hookworm) Microfilaria – Wucheria, Brugia, Loa loa, Mansonella, and Onchocerca
Enterobius vermicularis (pinworm)
Humans considered only host Females 8-13mm, males 2-5 mm Dwell in the cecum ¼-1/2 inch in thickness, white, lloks like string in stool
Lay up to 15,000 eggs◦ Oval with a flattened side: 50-60um by 20-30um
Diagnosis- Scotch tape test or anal swab Most common helminth in US
Enterobius vermicularis (pinworm) eggs
Asymmetrical eggs
Pinworm larvae -may be seen in stoolspecimens examined for pinworm
Eggs
Ascaris lumbricoides (roundworm)
1-1.2 billion people infected◦ More common in children
20,000 death Largest helminth to affect humans Females 20-35cm long, males 15-30cm with a curved tale◦ Can cause intestinal obstruction
Ascaris lumbricoides
Trichuris Trichiura (whipworm)
Soil transmitted Disease can can be similar to amebiasis PVA preserved samples inferior to formalin Adults attach to large intestine and are rarely recovered – diagnosis by detecting egg in stool specimens
Thinnest part- head Males are smaller than females
Trichuris trichiura
tail
Head
Necator americanus, Ancylostoma duodenale (Hookworms)
Soil transmitted 2nd most common helminth infection Enter via exposed skin
Necator or Ancylostoma – Hookworm egg
Strongyloides stercoralis
Soil transmitted Larval form only Presence of internal structures can separate from artifact In immune suppressed - massive intestinal infection and migration to the respiratory tract (eosinophilic pneumoniae) possible
Strongyloides larvae
Strongyloides stercoralis
Can be found in intestines or stoolsIn real sick can go to lung and cause pneumonia
Trichinella spiralis
-Tissue nematode-All stages occur in single host-usually an incidental findingin muscle
Microfilariae Sheathed
◦ Wucheria bancrofti and Brugia malayi◦ Elephantiasis (lymphangitis/lymphedema)
◦ Loa loa◦ Calabar swellings & migrating worms in the conjunctiva
Not sheathed◦ Onchocerca volvulus◦ Mansonella species
◦ Allergic skin reactions, edema, Calabar swellings
Identification of microfilariae is based on the presence of a sheath covering the larvae, as well as the distribution of nuclei in the tail region
A, W. bancrofti. B, B. malayi. C, L. loa. D, O. volvulus. E, Mansonella perstans. F, Mansonella streptocerca. G, Mansonella ozzardi.
FilariaIdentification
a. W. bancrofti◦ Sheathed, nuclei stop short
of end of tail
b. B. malayi◦ Sheathed, two small nuclei
in tail
c. O. volvulus◦ Unsheathed, from skin, not
blood
d. Loa loa◦ Sheathed, nuclei to continue
to end of tail
Wucheria bancrofti
Brugia malayi
Loa loa
Mansonella perstans
Onchocerciasis
Black fly
Onchocerciasis
Trematodes (Flatworms) Intestinal and Liver flukes
◦ Fasciolopsis buski◦ Fasciola hepatica
Liver flukes◦ Clonorchis sinensis (Chinese liver fluke)
Paragonimus westermani – oriental lung fluke Schistosomes
◦ S mansoni – intestinal bilharziasis◦ S haematobium - urinary◦ S japonicum – blood fluke, found in intestines
Intestinal and liver flukes
Fasciolopsis buski Fasciola hepatica
The two most common intestinal flukes
Fasciola hepatica
Distinct nose
Fascioliasis is a parasitic infection typically caused by Fasciola hepatica, also known as "the common liver fluke" or "the sheep liver fluke. Fascioliasis is found in all 5 continents, especially where sheep or cattle are reared. Infected by eating raw watercress or other water plants contaminated with immature parasite larvae. The immature larval flukes migrate through the intestinal wall, the abdominal cavity, and the liver tissue, into the bile ducts, where they develop into mature adult flukes, which produce eggs. The pathology typically is most pronounced in the bile ducts and liver. Fasciola infection is both treatable and preventable
Intestinal fluke Fasciolopsis buski, causes fasciolopsiasis, is the largest intestinal fluke of humans. Prevented by cooking aquatic plants well before eating them. Found in south and southeastern Asia. Fasciolopsiasis is treatable. Many people do not have symptoms from Fasciolopsis infection. However, abdominal pain and diarrhea can occur 1 or 2 months after infection. With heavy infections Fasciolopsis flukes can cause intestinal obstruction, abdominal pain, nausea, vomiting, and fever.
Clonorchis sinensis
knobbin
Shouldersoperculates
Clonorchis is a liver fluke that can infect the liver, gallbladder and bile duct. Found across parts of Asia, it is also known as the Chinese or oriental liver fluke.
Egg is operculate, not embryonated, thick shell, asymmetrical and large
Paragonimus westermani
Paragonimus is a parasitic lung fluke (flat worm). Infections occur after a person eats raw or undercooked infected crab or crayfish. The illness is known as paragonimiasis. Paragonimus infection also can be very serious if the fluke travels to the central nervous system, where it can cause symptoms of meningitis.
Schistosoma mansonii
Schistosomiasis, also known as bilharzia, more than 200 million people are infected worldwide. In terms of impact this disease is second only to malaria as the most devastating parasitic disease.
The parasites that cause schistosomiasis live in certain types of freshwater snails. The infectious form of the parasite, known as cercariae, emerge from the snail, hence contaminating water. You can become infected when your skin comes in contact with contaminated freshwater. Most human infections are caused by Schistosoma mansoni, S. haematobium, or S. japonicum.
Stool or urine samples can be examined microscopically for parasite eggs (stool for S. mansoni or S. japonicum eggs and urine for S. haematobium eggs).
Cestodes (Tapeworms) Examples
Diphyllobothrium latum
Taenia saginata
Taenia solium
Hymenolepis nana
Hymenolepis diminuta
Echinococcus granulosis
Flattened dorsoventrally, segmentedHead with armed or unarmed scolexProglottids immature, mature (sex organs)Gravid (with eggs)
Internal structure of proglottidsHermaphroditic-ovary, testes, vitellaria, uterus, genital pore and ducts
Lateral excretory and nervous system
No gut-tegument absorbs nutrients
Muscles-longitidinal and horizontal
Diphyllobothrium latum
Diphyllobothrium latum
Poorly-cooked fresh-water fish (salmon) Scandinavian, Russia, Canada, N. USA, Alaska Broad fish tapeworm Longitudinal sucker Eggs have non-shouldered operculum and knob
◦ They are not embryonated
Infection causes VitaminB12 deficiency
Diphyllobothrium latum
Sucking plate
Diphyllobothrium latum
Taenia saginata
Beef tapeworm 4 suckers on scolex >13 uterine branches in proglottidsIngestion of cysticerci in beef
Intestinal infestationIngestion of eggs ->
Non-human pathogen
Taenia Solium
Pig tapewormRing of thorns/crown on scolex<13 uterine branches in proglottidsIngestion of cysticerci in pork
Intestinal infestationIngestion of eggs ->
Cysticercosis
Taenia Species – two speciesOutstanding characteristics
Taenia species
Taenia eggsIdentical eggs for the two species
Taenia saginata
Proglottid > 12 uterine branches
Taenia solium
Proglottis – fewer uterine branches(<=12 uterine branches)
Scolex - Ring of thorns
Cysticercosis
Caused by the ingestion of T. solium eggsNot by eating infected pork
Hymenolepis nana
Hymenolepis nanaMost common cestode recovered in USAWorm is 2-4 cmEgg has inner & outer shell separated
spaceWater /food contaminated by rodent droppings
Hooklets inside
Larger outer shellNo radial striations
Hymenolepis diminutaUncommon tapewormBig egg @ 80 microns in diameter
Echinococcus – hydatid cyst diseasefound in Africa, Europe, Asia, the Middle East, and Central and South America. Highest prevalence is found in populations that raise sheep. Infection ingestion of egg found in animal feces.
Echinococcus – hydatid cyst
Short tapewormSand like materialcontained in the Cyst, due to inverted folded tapeworms
Relative size of Helminth eggs
http://www2.bc.cc.ca.us/bio16/pal/Parasitology.htm
Additional Insects of interest
MaggotsHouse fly larvae
Bot fly larvae
Bot fly bites human,Larvae develops andextrudes from the skin
Ticks of importance
Soft tick -Expands with bloodengorgement
Hard Ticks
Black Widow spider
Hour glassOn tummy
FleaBody louse
Crab louse
Hair nit
Scabies
Tiny
egg
s un
der s
kin
Mite