XIV - Parasitology Flashcards
Process of living together of 2 unlike organisms
Symbiosis
One species benefits the other without harming/benefiting the other
Commensalism
Both species benefit one another
Mutualism
One species benefits while harming the other
Parasitism
Parasite lives inside the body of the host
Endoparasite
Parasite lives outside the body of the host
Ectoparasite
Presence of endoparasite in host connotes
infection
Presence of ectoparasite in host connotes
infestation
Needs a host at some stage of their life cycle to complete development and propagation
Obligate Parasite
May exist in a free-living state but becomes parasitic when the need arises
Facultative Parasite
Establishes itself in a host it does not ordinarily live in
Accidental/Incidental Parasite
Remains on host for life
Permanent Parasite
Lives on host for a short period of time
Temporary Parasite
Free-living organism that passes through digestive tract without infecting the host
Spurious Parasite
Host where parasite attains sexual maturity
Definitive/Final Host
Host that harbors the asexual or larval stage
Intermediate Host
Host wherein the parasite does not develop further to later stages
Paratenic Host
Host that allows the life cycle to continue and become additional sources of human infection
Reservoir Host
Transmits parasite from one host to another
Vector
Transmits parasite only after it has completed its development
Biologic Vector
Vector that only transports the parasite
Mechanical/Phoretic Vector
Process of inoculating an infective agent
Exposure
Establishment of infecting agent inside host
Infection
Between infection and evidence of symptoms
Incubation Period (Clinical)
Between infection and demonstration of infection
Pre-Patent Period (Biological)
Infected individual becomes his own direct source of infection
Autoinfection
Infected individual is further infected with same species leading to massive infection
Hyperinfection or Superinfection
Host Effects: E. histolytica trophozoites secrete cysteine proteases which digest cellular material
Enzymatic Interference
Host Effects: Plasmodium invades RBCs and cause rupture
Invasion & Destruction
Host Effects: D. latum competes with host for available supply of vitamin B12 (pernicious anemia)
Nutrient Deprivation
Immune Invasion: E. histolytica produces suppressor factor that inhibits monocyte movement
Immune Suppression
Immune Invasion: Surface protein variation in T. gambiense
Antigenic Variation
Immune Invasion: E. granulosus carries blood group antigens
Host Mimicry
Immune Invasion: T. gondii multiplies inside macrophages
Intracellular Sequestration
Protozoa: Intestinal Tract
Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum
Protozoa: Urogenital Tract
Trichomonas vaginalis
Protozoa: Blood & Tissue
Plasmodium, Toxoplasma gondii, Trypanosoma
Pseudopod-forming non-flagellated protozoa (Brownian movement), eukaryotic organism that lacks membrane-bound organelles, simple life cycle
Entamoeba histolytica
Most invasive parasite among the Entamoeba
Entamoeba histolytica
Entamoeba histolytica: Transmission
fecal-oral
Entamoeba histolytica: Infective Stage
mature cysts
Entamoeba histolytica: Diagnostic Stage
trophozoites (acute diarrhea), mature cysts & immature cysts (hardened stool)
Entamoeba histolytica Virulence Factors: Mediates adherence
lectin
Entamoeba histolytica Virulence Factors: Penetration
amebapores
Entamoeba histolytica Virulence Factors: Cytopathic effect
cysteine proteases
Entamoeba histolytica: Diseases
cyst carrier → amebic colitis → ameboma → amebic liver abscess
Entamoeba histolytica Diseases: Dysentery without fever, flask-shaped colon ulcers
amebic colitis
Entamoeba histolytica Diseases: Mass-like lesion in abdomen, associated with dysentery
ameboma
Entamoeba histolytica Diseases: Most common extraintestinal form, anchovy paste-like aspirate
amebic liver abscess
Entamoeba histolytica Treatment: Cyst Carrier State (asymptomatic)
Diloxanide furoate
Entamoeba histolytica Treatment: Amebic Colitis
Metronidazole
Entamoeba histolytica Treatment: Amebic Liver Abscess
Metronidazole, percutaneous drainage for non-responders
Entamoeba histolytica Treatment: Mild to Moderate Infection
Metronidazole + luminal agent
Entamoeba histolytica Treatment: Severe Infection
Metronidazole/Tinidazole + luminal agent
Entamoeba histolytica Treatment: Hepatic Abscess, Extraintestinal Infection
Metronidazole/Tinidazole + luminal agent
Flagellate that lives in the duodenum, jejunum and upper ileum, falling leaf motility, simple asexual life cycles, covered with variant surface proteins
Giardia lamblia
Giardia lamblia: Transmission
fecal-oral
Giardia lamblia: Infective Stage
cysts
Giardia lamblia: Diagnostic Stage
trophozoites (binucleated, “old man”), cysts
Adhesive disc and lectin facilitate attachment to avoid peristalsis, villous flattening, crypt hypertrophy, disruption of cytoskeleton, ultimately leads to enterocyte apoptosis
Giardia lamblia
Abdominal pain, “Backpacker’s Diarrhea”, excessive flatus (rotten eggs)
Acute Giardia lamblia Infection
Giardia lamblia: Chronic Infection
constipation, weight loss, steatorrhea
Giardia lamblia: Treatment
Metronidazole
Opportunistic intestinal protozoa, undergoes schizogony and gametogony, autoinfection in immunocompromised patients, acid-fast organism, simple life cycle
Cryptosporidium parvum
Cryptosporidium parvum: Transmission
fecal-oral
Cryptosporidium parvum: Infective Stage
thick-walled oocysts
Cryptosporidium parvum: Diagnostic Stage
thick-walled oocysts
Self-limited non-bloody diarrhea, severe life-threatening diarrhea if CD4 < 200 due to autoinfection
Cryptosporidium parvum
Cryptosporidium parvum: Treatment
Nitazoxanide
Urogenital protozoan, exists only as a trophozoite, pear-shaped, flagellated trophozoites, simple life cycle
Trichomonas vaginalis
Trichomonas vaginalis: Transmission
sexual intercourse, “Ping-Pong” transmission
Trichomonas vaginalis: Infective Stage
trophozoites
Trichomonas vaginalis: Diagnostic Stage
trophozoites
Watery, foul-smelling, greenish vaginal discharge accompanied by itching and burning, strawberry cervix (punctate hemorrhages on ectocervix)
Trichomonas vaginalis
Trichomonas vaginalis: Treatment
single oral dose of 2g (4 x 500mg tabs) of Metronidazole
Blood and tissue sporozoa, non-motile, asexual life cycle consists of shizogony & gametogony, sexual life cycle involves sporogeny, complex life cycle
Plasmodium
Most important parasitic disease in man
Plasmodium
Plasmodium: Transmission
bite of infected female mosquito (Anopheles filariasis minimus)
Plasmodium Life Cycle: Shizogony, Gemetogony
asexual
Plasmodium Life Cycle: Sporogony
sexual
Plasmodium: Asexual Host
man, intermediate
Plasmodium: Sexual Host
mosquito, definitive
Plasmodium: Infective Stage
sporozoites
Plasmodium: Diagnostic Stage
trophozoites (ring forms)
Pathologic findings from the destruction of RBCs, release of merozoites and splenic sequestration of infected cells, people with RBC defects (G6PD, sickle cell) are immune, partial immunity (premonition) seen in individuals who completely recover initial infection
Malaria (Plasmodium)
Plasmodium: 48 hour asexual cycle, malignant tertian, all aged RBCs, highest parasitemia, 0 merozoites, banana-shapes gametocytes, cerebral malaria, recrudescence, drug resistance
P. falciparum
Plasmodium: 48 hour asexual cycle, benign tertian, young RBCs, low parasitemia, 12-24 merozoites, large round gametocytes, relapse
P. vivax
Plasmodium: 72 hour asexual cycle, benign quartan, old RBCs, lowest parasitemia, 6-12 merozoites, compact gametocytes, recrudescence
P. malariae
Plasmodium: 48 hour asexual cycle, benign tertian, young RBCs, low parasitemia, 8 merozoites, small round gametocytes, relapse
P. ovale
Plasmodium: Recurrence of symptoms after a temporary abatement (2-4 weeks), seen in P. falciparum and P. malariae
Recrudescence
Plasmodium: Return of disease after its apparent cessation (1-6 months) due to reactivation of hypnozoites, seen in P. ovale and P. vivax
Relapse
Plasmodium: Diagnosis
thin & thick smears on Giemsa (thick - presence of organism, thin - species), higest yield when blood samples are taken during fever or 2-3 hours after peak
Malarial Dots: Punctate granulations present in RBCs invaded by P. ovale and P. vivax
Schuffner Dots
Malarial Dots: Coarse granulations present in RBCs invaded by P. falciparum, comma-shaped
Maurer Dots
Malarial Dots: Fine dots present in RBCs invaded by P. malariae
Ziemann Dots
Paroxysmal fever with malaise and bone pains, hemolytic anemia, jaundice, splenomegaly, parasitic pneumonitis, acute renal failure (blackwater fever), septic shock
Malaria (Plasmodium)
Plasmodium Findings: Malarial or Dürck’s granulomas
Cerebral Malaria
Plasmodium Findings: Acute renal failure, severe complication of P. falciparum, intravascular hemolysis, massive hemoglobinuria, acute renal failure, rare and sometimes fatal complication of quinine-sensitized persons
Blackwater Fever
Plasmodium Findings: Septic Shock
Algid Malaria
Plasmodium: High Endemicity
Palawan, Kalinga-Apayao, Ifugao, Agusan del Sur
Plasmodium: Chloroquine Resistance
Palawan, Davao del Norte, Compostela Valley
Plasmodium Treatment: Tissue Schizonticides
Primaquine - kill schizonts in the liver
Plasmodium Treatment: Blood Schizonticides
Chloroquine, Quinine - kill parasitic forms only in the erythrocyte
Plasmodium Treatment: Gametocides
Primaquine - kills gametocytes in blood
Plasmodium Treatment: Sporontocides
Proguanil, Pyrimethamine - prevent sporogony and multiplication in the mosquito
Plasmodium Treatment: Chloroquine-sensitive P. falciparum, P. malaria
Chloroquine
Plasmodium Treatment: P. vivax, P. ovale
Chloroquine + Primaquine
Plasmodium Treatment: Uncomplicated infections with Chloroquine-resistant P. falciparum
Quinine + Doxycycline/Clindamycin
Plasmodium Treatment: Severe or complicated infections with P. falciparum
Artesunate + Doxycycline/Clindamycin or Mefloquine/Malarone OR Quinidine gluconate
Plasmodium Treatment: Chloroquine-resistance
Mefloquine + Doxycycline
Plasmodium Treatment: Eradication of Hypnozoites
Primaquine
Plasmodium Treatment: Severe Cases/Pregnant
Quinidine, Quinine
Plasmodium Prophylaxis: Without resistant P. falciparum
Chloroquine
Plasmodium Prophylaxis: Chloroquine-resistant P. falciparum
Malarone, Mefloquine
Plasmodium Prophylaxis: Multidrug-resistant P. falciparum
Doxycycline
Plasmodium Prophylaxis: Terminal prophylaxis of P. vivax and P. ovale infection, alternative for primary prevention
Primaquine
Plasmodium Prophylaxis: Chloroquine-Sensitive Areas
Chloroquine 500mg/tab, 1 tab weekly
Plasmodium Prophylaxis: Chloroquine-Resistant Areas
Mefloquine 250mg/tab, 1 tab weekly, Malarone (Atovaquone 250mg/Proguanil 100mg)/ tab, 1 tab daily
Plasmodium Prophylaxis: Multidrug-Resistant Areas
Doxycycline 100mg/tab, 1 tab daily
Plasmodium: Prevention
chemoprophylaxis, insecticide-treated nets, insect repellant with DEET, biologic modification (cultivation of snails that eat mosquito larvae)
Tissue protozoan, definitive host - domestic cat, intermediate hosts - humans & other mammals, complex life cycle
Toxoplasma gondii
Toxoplasma gondii: Transmission
ingestion of cysts in raw meat and contaminated food, transplacentally
Toxoplasma gondii: Infective Stage
fecal oocysts
Toxoplasma gondii: Diagnostic Stage
trophozoites (bradyzoites)
Toxoplasma gondii Trophozoites: Rapidly multiplying, CMI limits spread
tachyzoites
Toxoplasma gondii Trophozoites: Slowly multiplying, important in tissue diagnosis
bradyzoites
Toxoplasma gondii: Diagnostic Test
IgM antibody
Toxoplasma gondii Disease: Heterophil-negative mononucleosis
immunocompetent
Toxoplasma gondii Disease: Encephalitis, ring-enhancing lesions
immunocompromised
Abortion, stillbirth, neonatal disease with hydrocephalus, encephalitis, chorioretinitis, hepatosplenomegaly, intracranial calcifications
Congenital Toxoplasma gondii Disease
Toxoplasma gondii: Treatment
Sulfadiazine + Pyrimethamine
Blood and tissue protozoan, 4 forms (amastigote, promastigote, epimastigote, trypomastigote), complex life cycle
Trypanosoma cruzi
Trypanosoma cruzi: Transmission
reduviid bug (Triatoma)
Trypanosoma cruzi: Infective Stage
metacyclic trypomastigotes
Trypanosoma cruzi: Diagnostic Stage
trypomastigotes in blood
Myocardial, glial, reticuloendothelial cells are frequent sites, cardiac muscle is the most frequently and severely affected tissue
Trypanosoma cruzi
Trypanosoma cruzi: Diagnosis
stained BMA or muscle biopsy, culture in special medium, xenodiagnosis - allowing an uninfected, laboratory-raised reduviid bug to feed on patient
Trypanosoma cruzi: Unilateral periorbital edema (Romaña’s sign), nodule near bite (chagoma), fever, LAD, hepatosplenomegaly
Acute Chagas’ Disease
Trypanosoma cruzi: Myocarditis, megacolon, megaesophagus (achalasia)
Chronic Chagas’ Disease
Trypanosoma cruzi: Treatment
Nifurtimox
Blood and tissue protozoan, 2 forms (epimastigote, trypomastigote), complex life cycle, remarkable antigenic variation
Trypanosoma brucei
Trypanosoma brucei: Types
gambiense, rhodesiense
Trypanosoma brucei: Transmission
tsetse fly (Glossina)
Trypanosoma brucei: Infective Stage
metacyclic trypomastigotes
Trypanosoma brucei: Diagnostic Stage
trypomastigotes in blood
Spread from the skin through the blood to the lymph nodes and the brain, somnolence (sleeping sickness) progresses to coma due to demyelinating encephalitis (ARAS, brainstem), cyclical fever spike (every 2 weeks) due to antigenic variation
Trypanosoma brucei
Trypanosoma brucei rhodesiense is _____ rapid and fatal than Trypanosoma brucei gambiense.
rhodesian is more rapid and fatal
Trypanosoma brucei: West
gambiense
Trypanosoma brucei: East
rhodesiense
Indurated skin ulcer (trypanosomal chancre), intermittent weekly fever and LAD, enlargement of the posterior cervical LN (Winterbottom’s sign), excessive somnolence, hyperesthesia (Kerandel’s sign), encephalitis, plasma cells with cytoplasmic Ig globules (Mott cells)
Trypanosoma brucei
Trypanosoma brucei Treatment: Blood-Borne
Suramin
Trypanosoma brucei Treatment: CNS Penetration
Melarsoprol