Parasitology, Zoonoses, and Diagnostics Flashcards
Why is parasitology important ?
global health- malaria (200mil+), US- pinworm, giardia, Immune suppressed- toxoplasmosis, strongyloidiasis, travelers- malaria, schistosomiasis
What are the various types of microbes?
virus, bacteria, fungi, and parasites: protozoan (unicellular), worm or helminth (multicellular), and ectoparasite (on skin or burrowing)
What are the two categories of protozoa?
unicellular, eukaryote, intracellular- often needs a vector, i.e. malaria, extracellular- often fecal-oral transmission, i.e. giardia (2 forms trophozoite- disease in humans and dormant cyst- adapted for passing)
What are the different kinds of helminthes?
round (hookworms causes anemia), flat- cestodes (taenia solium causes seizures), and Flukes- trematodes (schistoma mansoni causes cirrhosis)
What are the differences between protozoa and helminthes?
P: unicellular, vector or fecal oral, no eosinophilia; H- multicellular, also penetrate skin, eosinophilia common
What are the protozoa in the blood?
Plasmodium vivax, Plasmodium falciparum, plasmodium ovale, plasmodium malariae, plasmodium knowlesi, and Babesia microti
What are the key features of the disease Malaria?
Protozoan- plasmodium, intracellular in the blood, human reservoir, vector- female anopheles, red cell lysis, fever, chills
What are all the ways malaria is spread?
female anopheles mosquito (rare in US), rare- needle sharing, transfusion, perinatal
What are the vectors of malaria?
distribution affects disease distribution, strategy: no stagnant water, no mosquito breeding then no malaria, virus replicates inside mosquito increasing viral load with bite
What things affect P. falciparum progression into disease?
less in sickle trait, still need prophylaxis, prophylaxis designed for this strain
What host genetic features affect P vivax?
absent in duffy neg. (W. African trait)
What host genetic features affect P ovale?
fills in Duffy negative niche
What is the incubation period of malaria?
usually 8-30 days after bite, P. vivax and ovale- hypnozoites persist in liver,get attacks months to years later, P. Malariae- older cells, chronic infection
What is the sequence of malaria in humans? Anopheles?
female anopheles bite, drool, saliva in wound, to liver, mature, released as merozoites to RBC, cycles of RBC merozoite release, may form gametes; female ingests gametocytes, combines, invades gut, migrates to salivary gland
How is malaria diagnosed?
thick smear: multiple blood droplets, look for lysed RBC, sensitive for parasitemia; thin smear: see red cell, parasite morphology, can make species diagnosis
What are the features of P. Falciparum disease?
attacks RBC, heaviest parasitemia, deadliest, balanced polymorphism (less severe w/ Hgb AS or SS, “malignant tertian”, cerebral, renal malaria, chloroquine-resistant, gametocyte
What prophylaxis is used with P. Flaciparum that is chloroquine-resistant? Treatment?
mefloquine, atovaquone-proguanil (Malarone), doxycycline; quinine/quinidine or artemisinin, immediate treatment needed
What age RBC and is the cycle length of the species of malaria?
Falciparum- all ages, 48hrs, vivax and ovale- young, 48hrs, Malariae- old, 72 hrs
what is the key histological feature for plasmodium vivax?
schuffner’s dots
what is the key histological feature for plasmodium ovale?
resembles vivax, oval crenated
what is the key histological feature for plasmodium malariae?
“band” form, big dark band
what are the key features of plasmodium knowlesi?
emerging infectious disease, not common in US travelers, known in macaques, SE asia, morphology like P. Malariae, daily fevers, usually not fatal
what is the extra-erythrocyte stage of malaria? Treatment?
persistence with P. vivax/olvale, need drug effective in liver, primaquine usual choice, causes hemolysis with G6PD deficiency
what does the P. falciparum prophylaxis regimen look like?
start 2wk b4 arrival (1-2days for doxycycline or atovaquone-proguanil) drug levels tolerable, Q wk (daily for doxy or atov-pro), continue 4wk after departure (7 days for atov-pro), not 100% effective
what are the drawbacks of doxycycline?
photosensitivity in some, yeast, risk of esophagitis and perforation, take with full glass of water, remain upright 30 min
What are the drawbacks of mefloquine?
disturbing dreams, under controversy about long-lasting psychologic illness
What besides prophylaxis is recommended to prevent malaria?
mosquito avoidance- sleep screened or netting, indoors evening and nights (aedes dengue/yellow fever day time biting), DEET repellent, also lemon oil or eucalyptus, picaridin, permethrin on clothing (knock down), long clothing
What are the features of babesi microti?
often in cape cod and Martha’s vineyard, tetrad in cell, like malaria- protozoan, intracellular, vector, blood, fever and chills, unlike malaria- tick sread, mild in spleen, clindamycin, quinine if severe
What are the various protozoa in tissue?
toxoplasmosis, pneumocystis jiroveci, leishmaniasis, trypanosoma cruzi, Trypanosoma brucei (rhodensiense and trypomastigote) naegleria-acanthoamoeba
What are the features of toxoplasmosis?
toxoplasma gondii, intracellular protozoan, variety of syndromes- mononucleosis, retinitis, congenital infection, brain (AIDS), other immune gap, oocytes from cat feces and inadequately cooked meat
What are the features of pneumocystis jiroveci?
classic AIDS opportunist, protozoan (fungus now), theory- infects nearly everyone but host defenses control it, defect in cell immunity, prevent & treat- trimethoprim-sulfamethoxazole
What are the features of leishmaniasis?
protozoa in tissue, spread by phlebotomine sandflies, manifests as cutaneous non-healing ulcer or visceral (kala azar- fever, wt. loss, anemia, leukopenia
What are the features of Trypanosoma cruzi?
chagas disease, protozoan in tissue, latin America, Rub reduviid bug feces w/ T. cruzi into wound, esophageal dysmotility, heart disease, kinetoplast in front of cycle shaped nucleus with flagella
What are the features of Trypanosoma brucei?
African sleeping sickness, protozoan, tissue, Tsetse fly salivary glands, bite, ultimately encephalitis, treatment difficult and limited; rhodesiense and trypomasigote
What are the features of naegleria?
other free-living ameba, acanthoameoeba, wear contact lenses, get eye infection, swim in fresh water, get meningoencephalitis, occurs in US
What are the protozoa infections in the intestine?
E histolytica, Zoonoses- giardia, cryptosporidium, cyclospora
What are the protozoa infections in the vagina?
trichomonas vaginalis
What are the features of entamoeba histolytica?
ameba, asymptomatic human carriers pass cysts, diarrhea pt pass labile trophozoites, fecal-oral, bloody diarrhea, liver abscess, hard to distinguish from non-pathogenic amoebae (normal flora), white cells in stool, only decolonize in outbreaks, treatment of invasive disease- metronidazole and luminal agent
What are the features of giardia lamblia?
blocks portion of bowel, preventing absorption of fluids and nutrients, chronic diarrhea, fecal oral: day care, oral-anal sex, streams contaminated by beavers, St Petersburg Russia, stool, duodenal aspirate for tophozoites, treat w/ metronidazole
What are the features of cryptosporidium?
initially- zoonotic diarrhea in calf handlers, AIDS, Milwaukee system users; Acid fast stool, self limited in immune-intact, treat- nitaoxanide
What are the features of cyclospora cayentanensis?
“big crypto”, resembles large version of cryptosporidium, causes diarrhea, raspberries from central America (contaminated food and water), treat with trimethoprim-sufamethoxazole
What are the features of isospora belli?
watery diarrhea in AIDS, responds to trimethoprim-sulfamethoxazole
What are the features of microsporidia?
enterocytozoon-bieneusi, transient diarrhea in normal, chronic in AIDS, treat with albendazole
What are the features of trichomonas vaginalis?
15% of women, only occasionally causes vaginitis, sexual transmission, men asymptomatic usually, frothy cream discharge, pH> 4.5, treat- metronidazole
What are the features of intestinal helminths?
nematodes (roundworms)- ingested: acaris, enterobius, Trichuris, penetrate skin- hookworms, strongyloides; cestodes (tapeworms)- pork, beef, fish
What are the intestinal roundworm helminths?
ascaris lumbricoides, enterobius (pinworm), trichuris trichiuria (whipworm), strongyloides, hookworms (necator americanus, ancyclostoma duodenale)
What are the features of ascaris lumbricoides (human roundworm)?
ingest eggs, hatch in small bowel, larvae to lymphatics and lungs, up to trachea, swallowed, mature to worms in intestine, females release eggs in stool, symptoms- depend on worm burden, pneumonia, worm ball bowel obstruction, treat-albendazole or mebendazole, visceral larva migrans (dead end animal round worm infection)
What are the features of enterobius (pinworm)?
fecal-oral, ingest eggs, hatch duodenum, jejunum, larvae to ileum, gravid female migrate to perianal skin to lay eggs at night (scotch tape on paddle between butt cheeks) albendazole or mebendazole, treat family, bed and clothes
What are the features of trichuris trichiura (whipworm)?
fecal-oral, ingest eggs, hatch in small bowel, larvae migrate to colon (adults mature), eggs pass out in feces, mature in soil, diarrhea, rectal prolapse due to tenesmus (defecation sensation), treat- mebendazole or albendazole
What are the features of strongyloides?
filariform larvae in stool, larvae penetrate skin, to lymphatics, lung, coughed, swallowed to duodenum and jejunum
What are the features of the strongyloides illness?
cough, wheezing, fever, pain, vomiting, diarrhea (large worm burden), sepsis (larvae cross abdominal wall), immunosuppressed self-hyper-infection (reinfect themselves) chronic symptoms WWII POWs
How is strongyloides diagnose and treated?
eosinophilia, hard to see larvae in stool, consider duodenal exam, ivermectin
What are the features of hookworms (necator americanus, ancyclostoma duodenale)?
life cycle like strongyloides but eggs in stool and need to mature, no hyperinfection syndrome, no bowel wall invasion
What are the features of hookworm illness?
chronic anemia, depends on burden, penetrate skin initially “ground itch”, dog/cat hookworm- cutaneous larva migrans
How are hookworms diagnosed and treated?
eggs in stool, albendazole or mebendazole, diet supplements to correct anemia
Which nematodes are acquired by ingestion?
ascaris (round): bowel, eggs, animal-visceral larva migrans; enterobius (pin)- night itch, tape; trichura (whip)- prolapse, eggs
Which nematodes are acquired from skin penetration?
strongyloides (thread)- hyperinfection, larvae (diagnosis); necator (hook)- anemia, eggs (diagnosis), (animal- cutaneous larva migrans)
What are the features of intestinal tapeworms (cestodes)?
infected human w/ eggs in feces, animal eats feces, cysticerci develop in animal and migrates to tissues, humans eat undercooked tissue, parasite hatches in intestine, usually nausea, vague discomfort in infected human
What intestinal worm is found in beef? pork? fish?
taenia saginata; taenia solium; diphyllobothrium latum
what are the blood and tissue helminths that are ingested?
Trichinella, T. solium, E. granulosus, Visceral larva migrans, guinea worm, lung fluke and liver fluke
What are the blood and tissue helminths that come in through skin?
schistosomes, cutaneous larva migrans, lymphatic filariasis, and river blindness
What are the features of trichinella spiralis?
ingest undercooked pork or bear meat, cysts hatch inhuman bowel, migrate skeletal and cardiac muscle, asymptomatic to fatal, depends on burden
What are the features of cysticrecosis?
tissue invasion of T. solium (pork tape worm) after cysticerci ingestion, cysts in brain (seizures, hydrocephalus, scolex head)treat with albendazole
what are the features of echinococcosis (hydatid disease)?
echinococcus granulosus egg ingestion from feces of dogs/carnivores, eggs hatch in intestine, penetrate wall, “hydatid cysts” in various organs, concern- spillage in surgery, aspirate fluid- inject drug, systemic albendazlole
How do you treat guinea worm?
pull out of wound with a stick
What are the features of lung fluke? liver fluke?
paragonimus westermani (cysts in lung); clonorchis sinensis
What are the features of schistosomal trematodes?
snail intermediate hosts, distinct from but related to other trematodes; paragonimiasis (lung), clonorchiasis (liver)
What are the features of the schistosomiasis mansoni? S. haematobium? S. japonicum?
large lateral spine, Americas, stool, colon and rectum; egg in urine and bladder with large terminal spine, Africa, mideast; very small spine, east asia, stool, small bowel, colon
What is the lifecycle of schistosoma?
invades snail, develops, cercariae released into water, penetrates human skin, matures, lays eggs, human defecates in water, eggs hatch and invade snail
What is the life cycle of bird schistosome?
birds and snails, penetrates human skin, can’t mature, dies in skin, swimmer’s itch, resolves spontaneously; mate in portal vein, to site, egg release, miarcidia hatch (water) to snails, to fork tailed cercariae, to skin, to rt heart, to lungs to gut to portal vein
What is the presentation of schistosomal speicies?
early: skin, itch, fever, headache, abdominal pain, serum sickness like; Katayama syndrome (paraplegia in some cases), retained eggs, eosinophilic granulomas (chronic granulomatous inflammation), S. haematobium (bladder and urinary tract), other species liver and intestine
How is Schistosomiasis diagnosed? treated? control?
microscopic egg id (size, spines), serology developing; dermatitis, katayama (antiinflamatory), worm killing- praziquantel; feces out of fresh water, no vaccine, treat bathing water, towel or rubbing alcohol
What are the kinds of filariasis?
onchocerciasis and elephantiasis, subcutaneous larvae mature to adult worms, release microfilariae
What are the features of onchocerciasis?
black fly bites, onchocerca volvulus, subcutaneous spread, reach anterior chamber, river blindness, skin snips, treat- ivermectin
What are the features of elephantiasis?
mosquito bites, wuchereria bancrofti, lymphatic spread, inflame lymphatics, obstruction, grotesque lymphedema, microfililariae in giemsa-stained blood smear at 2 am (most sensitive time)
How do we classify parasites?
protozoa or helminth, site- blood and tissue, intestinal or vaginal, route- ingestion, vector, skin and ectoparasites (skin)
What are the general principles of zoonoses?
vector specificity, limited distribution, often intracellular, not from inanimate and not person-person
What are some general features of ticks?
arachnid, hard or soft, larva-nymph-adult, humans often dead end, midsummer to midspring, microbe persists throughout life cycle and multiple blood meals
What can tick toxins cause?
granuloma from embedded tick part, paralysis- toxin effect cured by tick removal
What are the features of Colorado tick fever?
high altitude in west, biphasic fever, low WBC, platelets, flaviviruses (tickborne encephalitis)
What are the features of rickettsiae?
many obligate intracellular, penicillin ineffective, humans often dead end, serologic diagnosis limited, spotted fever and typhus groups
What are the features of Rocky Mt. spotted fever?
from rickettsiae rickettsia, fever, headache, rash (in this order, spots start distal, pinpoint leaks from petechiae), immunofluorescent biopsy (confirmation), doxycycline, chloramphenicol, more common in the east
What are the features of ehrlichiosis and anaplasmosis?
vet disease, rocky mt spotless fever, gram (-) intracellular, tick, vectors, men post tick bite early summer,
What are the subclnical diseases of ehrlichiosis and anaplasmosis?
human monocytic ehrlichiosis (E. Chaffeenis, SE and S central US), Human granulocytotrophic erlichiosis (E.Wingii, E.Cani, S central US), and Human granulocytotropic anaplasmosis (Anaplasma phagocytophilum, NE US, upper Midwest, N.Cali)
What are the symptoms with Ehrlichiosis and anaplasmosis?
fever, headache, chills, rash infrequent, transaminases up, WBC and platelets down, rare leukocyte inclusions, IFA, tetracycline preferred, quinolone resistance
What are the pathological, diagnostic and therapeutic features of ehrlichiosis and anaplasmosis?
not vasculitis, specialized lab- indirect fluorescent Ab, PCR, doxycycline, prevention- tick avoidance, ulcerating papule @ bite site
What are the features of Francisella tularensis?
tick and rabit borne, causing ulcers and swollen lymph nodes, bioterrorism candidate
What are the features of borrelia recurrentis?
relapsing fever, antigenic disguise, relapse from reticuloendothelial system, tick borne
What are the features of lyme disease?
rash, joint, neuro, heart, joint, fatigue, tick borne, erythema chronicum migrans, serology may be false positive, big in north central and north east
What diseases are transmitted by aedes aegypti mosquito?
yellow fever and dengue (domestic day biting, prefer humans)
What are the features of yellow fever?
flavivirus (lipid enveloped RNA), vaccine for travelers, avoid mosquitos- pyrethrum spray for screens and bed netting, clothes: long permethrin, person: DEET (picardin, lemon oil of eucalyptus), daytime caution
What are the features of dengue?
flavivirus- 4 serotypes, tropical distribution approximates, usually self-limiting fever and malaise, musculoskeletal pain “breakbone fever” might reflect marrow involvement
What are the features of hemorrhagic fever/shock syndrome?
occurs if immune to one serotype but infected with second, vascular permeability, cytokine activation
What intervention is used for dengue?
supportive care, no vaccine as yet, mosquito control, esp. breeding sites- artificial water container
What are the clinical features of West nile virus?
63% symptomatic at 30 days, neuroinvasive disease, some with anterior horn cell damage (polio picture), 37% full recovery 1 yr, still weak, confusion, and lightheaded
What are the features of West Nile Virus?
flavivirus, culex mosquitos, most infections mild, 1/150 encephalitis, myelitis and meningitis, serum or CSF IgM, no specific treatment
What are the features of bartonellosis?
B. baciliformis, sandflies, oroya fever, RBC, verruga (solitary angiomatous nodule)
What are the features of Yersinia pestis?
black plague, fleas abandoning dying rats go for humans, painful lymphadenopathy, also pneumonic, few US cases, streptomycin or doxycycline
What are the features of mycobacterium skin lesion after salt water?
exposure salt water, cellulitis, routine cultures negative, routine therapy ineffective, need diagnostics and therapy suited for mycobacterium
What are the features of hantavirus pulmonary syndrome?
1993 four corners area, Sin Nombre virus, deer mice feces, adult respiratory distress, lassa fever (W. Africa), lymphocytic chroiomeningitis (hamster aseptic, no B growth in culture), Leptospirosis (red eye, kidney, liver disease, rat urine exposure)
What are the features of cat scratch disease?
caseating granulomas of rt groin node, kitten < 1yo, few bacilli consistent, caused by Bartonella henselae, use Warthin-Starry Silver stain
What are the features of anthrax?
cutaneous- black ulcerating lesion, superior mediastinum prominent with inhaled anthrax, CSF- gram + rods
What are the features of Orf virus disease?
rancher or veterinarian, solitary maculopapule often finger, brucellosis- variable clinical picture- arthritis, chronic fatigue, hard to diagnose treat
What are the features of rat-bite fever?
streptobacillus moniliformis, spirillum minus, fever and arthritis
What are the features of pasteurella multocida?
dog and cat bites (normal flora), drug- penicillin, usually give omoxycilin w/ clauvulonic acid
What are the features of Eikenella corrodens?
human oral flora, spread with human bites, clenched fist injury, penicillin (ampicillin ok)
What are the groups of helminths? How are they diagnosed?
trematodes (flukes), cestodes (tapeworms), and nematodes (round worms); commonly by ova recognition in stool and rarely as adult worm
What type of host are humans in the helminth life cycle?
intermediate or definitive
What are the intestinal flukes? genitourinary flukes? liver fluke? lung fluke?
S. japinicum and S. mansoni; S. haematobium; Fasciola hepatica; Paragonimus westermani
Where do the adult trematodes reside in portal vein system?
large intestine- S. mansoni, small intestine- S. japonicum, urinary bladder- S. haematobium
What is the tapeworm for the mouse? dog?
hymenolepis nana; echinococcus granulomas
What are the features of adult cestodes of taenia species?
proglottids common (stool of infected patient), scolex rarely seen, passed only during treatment
what are the features of cestodes ova of taenia species?
ova look identical between pork and beef, thick striated shell, six-hooked embryo
What are the features of trichnella spiralis tissue larvae? diagnosed?
life cycle tissue phase diagnostic- worm/ova not in stool, transmitted to humans in infected meats (stored in larval stage, encysted in muscle), once ingested larvae migrate; muscle biopsy, tongue common source
What are the features of adult enterobius vermicularis?
females larger than males, long, thin sharp pointed tail, egg easily transmitted in air and ingested
What are the features of ova enterobius vermicularis?
recover characteristic ova in rectum, females oviposit in rectum, collect with scotch tape in perianal region, larger than most ova, conspicuously flattened on one side, thick outer shell
What are the features of adult ascaris lumbricoides?
large intestinal roundworm, common in stool, egg- infectious form, released in environment, infected by digestion
What are the features of ova of ascaris lumbricoides?
large number in stool, large size, covered by thick shell
What are the features of strongyloides stercoralis rhabditiform larvae?
larval forms in stool- diagnostic, ova not commonly seen in stool, larvae look identical to hookworm rhabditiform larvae
What are the general features of protozoan?
small microscope, amebae, flagellates, sporozoa, ciliates- rare cause of disease, diagnosed by cysts in stool
What are the features of entamoeba histolytica trophozoites?
adult feeding stage, unique characteristic- typical entamoeba nucleus, erythrocytes observed in cytoplasm, major pathogen in this group, causes amebic dysentery
What are the features of entamoeba histolytica cysts?
diagnostic and infectious form, spherical and small in size, entamoeba nucleus- peripheral margination of nuclear chromatin on inner surface of distinct nuclear membrane, up to 4 nuclei, coli cysts up to 8
How is giardia lamblia clinically diagnosed?
trophozoite and/or cyst in stool, EIA to detect for giardia Ag direct from stool (also detect for cryptosporidium)
What are the characteristics of giardia lamblia trophozorite?
bilateral symmetrical- can be divided in half and have identical features, 2 nuclei present each side of central axostyle, leaf shape structure (trichrome stain)
What are the characteristics of giardia lamblia cysts?
small, oval shaoed, contain up to 4 nuclei, show “halo” appearance- clear space between cyst wall and cytoplasm
What are the features of trichomonas vaginalis- trophozoite?
sexually transmitted, vaginitis in females (rare prostatitis or epididymitis), diagnosed- wet prep of vaginal secretions, no cyst produced, or giemsa stain
What are the features of cryptosporidium parvum oocytes?
cause cryptosporidiosis (gastroenteritis in immune compromised, considered AIDS indicator), diagnose- oocytes in stool, small, ovoid, easily mistaken for artifacts or yeast, acid-fast positive, modified by Ziehl-Neelsen stain, EIA direct in stool
What are the features of plasmodium species and diagnosis?
causes malaria, detect plasmodia in blood of infected individual, giemsa or wright stain, speciation difficult-requires individual knowledge in various blood types, differences in susceptibility to antimalarial therapy
What are the features of sarcoptes scabiei? diagnosis?
causes scabies, adult mites enter skin by digging and burrowing in upper layer of epidermis, find adult parasites or eggs in skin scraping of infected area
What are the features of adult phthirus pubis?
pubic or crab louse infestation, adult or broader than pediculus- head lice, diagnose- eggs (nit) found on the hairs of genital region, adults may be observed
