Parasitology Flashcards
1
Q
Plasmodium falciparum
A
- Ring
- Maurer’s clefts
- 1 to 2 small chromatin dots
- occasional appliqué (accolé) forms
- Trophozoite
- normal; rarely, Maurer’s clefts
- dark pigment
- Schizont
- normal; rarely, Maurer’s clefts
- mature = 8 to 24 small merozoites; dark pigment, clumped in one mass
- Gametocyte
- RBC distorted by parasite
- crescent or sausage shape
- chromatin in a single mass (macrogametocyte)
- diffuse (microgametocyte)
- dark pigment mass
2
Q
Plasmodium Vivax
A
- Ring Trophozoite
- RBC normal to 1.25x, round;
- occasionally fine Schüffner’s dots
- multiple infections of RBC not uncommon large cytoplasm with occasional pseudopods
- large chromatin dot
- RBC enlarged 1.5 to 2x;
- may be distorted;
- fine Schüffner’s dots large amoeboid cytoplasm
- large chromatin
- fine, yellowish-brown pigment
- Schizont
- enlarged 1.5 to 2x; may be distorted;
- fine Schüffner’s dots large, may almost fill RBC;
- mature = 12 to 24 merozoites
- yellowish-brown coalesced pigment
- Gametocyte
- RBC enlarged 1.5 to 2x; may be distorted;
- fine Schüffner’s dots round to oval;
- compact; may almost fill RBC;
- chromatin compact, eccentric (macrogametocyte) or diffuse (microgametocyte);
- scattered brown pigment
3
Q
Plasmodium Ovale
A
- Ring
- RBC normal to 1.25x, round to oval; occasionally Schüffner’s dots;
- Trophozoite
- Schizont
- mature = 6 to 14 merozoites with large nuclei, clustered around a mass of dark-brown pigment
- Gametocyte
4
Q
Plasmodium malariae
A
- Ring
- RBC normal to 0.75x
- Trophozoite
- Ziemann’s stippling
- Schizont
- mature = 6 to 12 merozoites with large nuclei,
- clustered around mass of coarse
- dark-brown pigment
- occasional rosettes
- Gametocyte
- round to oval;
- compact; may almost fill RBC;
- chromatin compact, eccentric (macrogametocyte) or more diffuse (microgametocyte)
- scattered brown pigment
5
Q
Malaria Clinical Significance
A
- Uncomplicated malaria
- – Fever
- – Chills
- – Sweats
- – Headache
- – Nausea
- – Vomiting
- – Body aches
- – General malaise
- – Diarrhea
- Severe malaria
- P. falciparum
- – cerebral malaria, severe anemia, hemoglobinuria, pulmonary edema, cardiovascular collapse
- – acute kidney failure, hyperparasitemia, metabolic acidosis, hypoglycemia
- – “Blackwater fever”
- Complications of P. vivax malaria include splenomegaly (with, rarely, splenic rupture)
- P. malariae
- nephrotic syndrome
- Severe malaria is a medical emergency and should be treated urgently and aggressively!
- P. falciparum
6
Q
Onchocerciasis
A
- Filarial nematode: Onchocerca volvulus
- Also harbors Wolbachia
- Eye disease: “River blindness”
- Transmitted by Simulium blackfly
- After deposition in skin by fly bite,
- O. volvulus matures over 6-12 months
- • Live in subcutaneous tissues (up to 80cm long)
- – Produce microfilariae
- • Lifespan up to 15 years
- Intense dermatitis, pruritis
- – Can be disfiguring
- – Subcutaneous nodules
- Keratitis
- –Inflammatory reaction to microfilariae in anterior chamber
- –Sclerosing keratitis, blindness with repeated insults
- Chorioretinitis too
- Diagnosis
- Slit lamp
- • Skin snips
- – Allows quantitation
- • Blood examination
- PCR, detect onchocercal DNA in skin snips
- • Serology
- – ELISA
- • Mazzotti reaction
- – Give DEC: pruritis, eye reactions few hrs later
7
Q
Loa loa
A
- Cause: Loaiasis
- Similar life cycle to other filaria
- Can cause high-grade
- microfilaremia
- –Diurnal
- Transmitted by Tabanid (Chrysops) flies
- – Day-biting, life in canopy of rain forest
- “Eye worm”
- Majority are asymptomatic
- •May be recognized only after subconjunctival migration of an adult worm
- “Allergic” symptoms more common
- Eosinophilia
- Renal involvement 30%
- Migratory swelling in limbs (Calabar swellings); encephalitis
- Diagnosis
- Blood smear
- • Isolation from subcutaneous (or subconjunctival) tissues
- • PCR for the detection of L. loa DNA in blood
- • Serology, incorporation of SXP-1 (loa-specific recombinant protein) into a luciferase immunoprecipitation system assay
8
Q
Mansonella ozzardi
A
9
Q
Mansonella streptocerca
A
10
Q
Mansonella perstans
A
11
Q
Dirofilaria spp.
A
- Consists of species that infect carnivores, rodents and primates
- Humans are incidental hosts for D. immitis (dog heartworm), D. tenuis (raccoons) and D. repens (dogs)
- Humans acquire Dirofilaria when bitten by mosquitoes, the arthropod vector and intermediate host
- The worms die before completing their development in the human host
12
Q
Angiostrongylus cantonensis
A
- Cause angiostrongiliasis
- CNS involvement, meningitis, neurologic disturbances, eosinophilia
- From eating undercooked crustaceans infected with larvae or by accidental
- ingestion of small infected mollusks or fruit and vegetables
- Spreading worldwide; endemic in Southeast Asia and the Asian Pacific Islands
13
Q
Trichinellosis
A
- (trichinosis) is caused by nematodes (roundworms) of the genus Trichinella
- Trichinellosis (trichinosis) acquired via undercooked meat containing Trichinella larvae
- – T. spiralis
- – Historically pork
- • In U.S., now more commonly wild game (esp. bears)
- Trichinella: Clinical
- Incubation 7-30 days
- • GI complaints (diarrhea, abdominal pain, vomiting) first
- • Edema (esp. periorbital)
- • Eosinophilia
- • Subungual splinter or subconjunctival hemorrhages
- • Fever
- • Myositis
- Illness severity:
- – Usually mild (or asymptomatic)
- – Can last weeks-months
- – 1% of cases fatal (myocarditis, encephalitis,
- pneumonia)
- Diagnosis
- Eosinophilia: high levels
- • Antibodies detectable 3 weeks after infection
- • Muscle biopsy
- Prevention
- • veterinary control of meat
- • hygiene
14
Q
Dracunculiasis (guinea worm disease)
A
- nematode (roundworm) Dracunculus medinensis.
- Humans become infected by drinking unfiltered water containing copepods (small crustaceans) which are infected with larvae of D. medinensis
- People with Guinea worm disease (GWD) have no symptoms for about 1 year. Then, the person begins to feel ill. Symptoms can include the following:
- Slight fever
- Itchy rash
- Nausea
- Vomiting
- Diarrhea
- Dizziness
- Adult in foot blister, larvae released into water
- maturity as early as 10 weeks subcutaneous tissues and attains sexual Adult inhabits the cutaneous and
- female is 500 to 1200 mm by 0,9 to 1,7 mm
- the male, 12 to 29 mm by 0,4 mm
- Larvae, long slender, 750μm in length with a long slender, whip like tail
-
2-3 foot-long white worm emerges from skin
- – About 1 year after ingestion
- Painful blister first
- Usually lower extremities
- Weeks to emerge
15
Q
Toxocara spp
A
- Toxocara canis or dog roundworm
- Toxocara canis measures 9 - 18 cm and occur in the intestine of the dog
- Humans acquire infection by ingestion of embryonated T. canis eggs in contaminated soil or infected paratenic hosts
- Puppies are a major source of environmental egg contamination
- Larvae of both species can cause toxocariasis in humans
- Most infections are with T. canis
16
Q
Sarcocystis
A
- Intestinal Coccidia of the Phylum Apicomplexa
- 150 valid species of Sarcocystis
- Taxonomically related to Isospora and Cyclospora
- Humans as the Definitive Host
- Sacrocystis hominis – cattle, bison, and water buffalo are the intermediate host
- Sacrocystis suihominis – pigs are the intermediate host
- Intestinal (Definitive Host)
- Mostly asymptomatic
- Incubation period of 3 to 6 hours
- Nausea, abdominal pain, and diarrhea
- Segmental enterocolitis - surgical resection
- Shedding up to 18 months possible
- Muscular (Intermediate Host)
- Rare condition; associated with sarcocysts from nonhuman primates, snakes
- Fever, myalgia, arthralgia, headache, fatigue, rash
- Intestinal Sarcocystis
- Specimen
- Three stool specimens collected on subsequent days
- Formalin-fixed stool
-
Microscopy
- Unstained Wet Mount
- Autofluorescence
- Oocysts – consists of two sporocysts
- Sporocysts – contains four sporozoites
- Specimen
- Muscular Sarcocystis
- Specimen: Muscle biopsy
- Microscopy: sacrocysts and bradyzoites
17
Q
Baylisascaris procyonis
A
- Cause Baylisascariasis, a zoonotic infection
- Nematode found ubiquitously in raccons, its larvae migrating in the intermediate hosts causing visceral larva migrans (VLM)
- Eggs are eliminated in raccoon feces. Humans become accidentally infected when they ingest
- infective eggs from the environment; typically this occurs in young children playing in the dirt
- Migration of the larvae through a wide variety of tissues (liver, heart, lungs, brain, eyes) results in VLM and OLM syndromes, similar to toxocariasis
- In contrast to Toxocara larvae, Baylisascaris larvae continue to grow during their time in the human host
-
Symptoms of infection may take a week to develop and include:
- Nausea
- Tiredness
- Liver enlargement
- Loss of coordination
- Lack of attention to people and surroundings
- Loss of muscle control
- Blindness
- Coma
19
Q
Babesia
A
- Protozoan parasite of the phylum Apicomplexa
- >100 species
- No exoerythrocytic phase
- Grouped by Trophozoite Size
- Small – 1.0 to 2.5 um
- B. microti, B. gibsoni, B. duncani
- Large – 2.5 to 5.0 um
- B. bovis, B. canis, B. divergens
- Human Infections – B. microti, B. duncani (USA);
- B. bovis, B. divergens (Europe)
- Human infections transmitted by Ixodes ticks
- Reportable condition in 27 States in 2013
(including California) - Seasonality – June through August
- Clinical Presentation
- Clinically similar to malaria
- Incubation period of 1 to 4 weeks
- High fever, myalgias, fatigue,
- hepatosplenomegaly, thrombocytopenia, and anemia
- Mild illness in nonsplenectomized individuals
- 42% mortality rate in splenectomized individuals (Europe)
- Coinfection with B. burgdorferi (10% of Lyme disease patients); more severe disease
- Laboratory Detection
- • Context of clinical symptoms, travel to
- endemic areas, tick exposure, blood
- transfusion
- • Blood Smear
- • PCR
- • Serology
- Identification of intraerythrocytic Babesi organisms by light microscopy in Giemsa, Wright, or Wright-Giemsa-stained blood smear;
- Babesia Blood Smear – Distinguishing Features
- Variable trophozoite sizes; rings smaller than P. falciparum
- Extracellular trophozoites
- Multiply infected RBCs more common
- Cytoplasmic vacuoles
- No pigment
- Diagnostic tetrads or Maltese cross
- Travel history
23
Q
Trypanosoma cruzi
A
- CHAGAS disease
- found only in the Americas: southern US (Texas) to southern Argentina
- poor rural areas of
- –Mexico - Central America - South America
- •50,000 deaths per year
- •endemic areas 10 % of all adult deaths
- The Vector: reduviid bugs, kissing bugs Triatoma megista, Rhodnius prolixus
- Symptoms
- •Incubation period of at least several (2-3) weeks
- •Localized inflammatory reaction at the infection site, chagoma (erythematous subcutaneous nodule) or Romana’s sign (if the portal of entry is the upper face or eye, the unilateral conjunctivitis and orbital edema)
- •Acute
- –Fever, hepatosplenomegaly, myalgia, rash and generalized lymphadenopathy
- –In immunosupressed patients: acute myocarditis or acute encephalitis with high mortality rate
- –In 2-3 months most of acute cases resolve into an asymptomatic chronic stage; still capable of transmitting the infection
- •Chronic
- –cardiac and gastrointestinal sequelae occur many years after initial infection
- •Myocarditis
- •Cardiomyopathy with cardiomegaly (cardiac enlargement)
- •Ventricular arrhythmias and heart failure
- •Megaesophagus,with substernal disconfort, painful swallowing, progressive dilatation and hypertrophy of the esophagus with regurgitation of food
- •Megacolon wih severe constipation
- Diagnosis
- •Travel history
- •Trypomastigotes
- –Buffy coat for motile parasites
- –Thin and thick smears with Giemsa
- •Histologic examination of biopsy specimens
- •Serology: CF, IFA, IHA, ELISA
- •PCR
- •Culture (NNN), for epimastigotes
- •Animal inoculation (rat, mice)
- •Xenodiagnosis
24
Q
Trypanosoma brucei
A
- cause the African Trypanosomiasis also known as “sleeping sickness”
- T.b. rhodesiense
- T.b. gambiense
- VECTOR
-
Tsetse fly
- Glossina palpalis
- Glossina morsitans
- Clinical Disease
- •The incubation period is usually between 2 weeks and 2-3 months
- •At the site of the bite there may be a local inflammatory nodule, or chancre
- •In humans, the disease varies in severity from a mild type, with few trypanosomes in the blood to a severe fulminating type
- Chancre
- Symptoms
- •The acute disease is characterized by irregular fever, headache, hepatosplenomegaly, joint and muscle pains and a rash
- •The trypanosomes are present in the blood, lymph nodes and bone marrow
- •Winterbottom’s sign consists of the enlargement of the laterocervical and occipital lymph node group (proeminent in T. brucei gambiense infection)
- The chronic phase of the disease gradually ensues, with the development of characteristic CNS changes (trypomastigotes invade CNS)
- A diffuse meningoencephalitis and meningomyelitis develops. Fever and headache pronounced
- •The terminal sleeping stage patient becomes more and more difficult to arouse
- •Emaciated, profound coma
- •Death ensues either from the disease or from intercurrent infections, such as pneumonia, malaria, disentery and aided by starvation
- •Untreated infections may progress to a fatal termination (rapid in T. brucei rhodesisense) or develop into a chronic or latent disease (T. brucei gambiense)
- Diagnosis
- •African Trypanosomiasis may be suspected when a patient from an endemic area has an acute infection with irregular fever and palpable lymph nodes, particularly in the postcervical triangle, or has developed a chronic disease with somnolence, personality changes and neurologic symptoms
- •The laboratory diagnosis is made by finding the trypomastigotes in the blood, lymph nodes, bone marrow and in the CSF
- •Trypanosomes may be few or irregularly present
- •Antibody
- •Antigen
- •ELISA
- •Indirect agglutination
- •Molecular
- •Animal inoculation
- •Suramin for T. rhodesiense infection
- •Pentamidine isethionate (Lomidine) for T. gambiense infection
25
Q
Wuchereria bancrofti
A
- Adults
- In lymph nodes and lymphatic channels
- Microfilaria
- In blood, hydrocele fluid, chylous urine
Size: microfilariae measure 244 to 296 μm by 7.5 to 10 μm
- In blood, hydrocele fluid, chylous urine
- Disease
- Lymphangitis, elephantiasis, hydrocele
- Geographic distribution
- Tropical and subtropics worldwide
- Vector
- Mosquito: Anopheles, Culex, Aedes, Mansonia and
Coquillettidia
- Mosquito: Anopheles, Culex, Aedes, Mansonia and
- Reservoir
- Humans
- Periodicity
- Nocturnal periodicity, except the South Pacific microfilariae
which have the absence of marked periodicity
- Nocturnal periodicity, except the South Pacific microfilariae
- Special features
- The microfilaria are sheathed, have a gently curved body,
and a tail that is tapered to a point. The nuclear column (the
cells that constitute the body of the microfilaria) is loosely
packed; the cells can be visualized individually and do not
extend to the tip of the tail
- The microfilaria are sheathed, have a gently curved body,
26
Q
Brugia malayi
A
27
Q
Brugia timori microfilaria
A
