Protozoal and Fungal Infections Flashcards
(39 cards)
Malaria
-causative- plasmodium spp. - P. vivax, P. falciparum, P. malariae, P. ovale
-contracted by bite of infected female Anopheles mosquito during feeding
-liver stage- sporozoites are injected and migrate through circulatory system and infect hepatocytes in liver
-multinucleated schizonts from P. vivax and P. ovale form hypnozoites which can remain dormant or form schizonts
-hepatic schizonts ultimately rupture -> release merozoites capable of infecting RBCs
-blood stage- merozoites infect blood cells and develop into trophozoites and blood cell schizonts or gametocytes
-infected blood cells rupture -> release merozoites capable of infecting other RBCs or male and female gametocytes capable of being ingested by mosquitoes
-sexual reproduction occurs in mosquitos midgut and mature sporozoites migrate to mosquitos salivary gland, ready to infect another human at next feeding
-vector- anopheles spp.
malaria: areas primarily infected and incubation
-tropical and subtropical regions
-highest rates of transmission are found in sub-saharan africa and new guinea
-malaria transmission does not occur at high altitude, during cold season, in deserts, or in areas with effective mosquito eradication programs
-incubation- 7-30 days
-incubation is shorter for P. falciparum and longer for P. malariae
-partial immunity for ineffective malaria prophylaxis may delay symptoms for weeks or months
malaria testing
-should be suspected in pts with febrile illness and recent travel to region where malaria is endemic
-labs may reveal anemia, thrombocytopenia, elevated AST/ALT, elevated bilirubin, and elevated BUN/creatinine
-thick and thin blood smears should be obtained to detect parasites (thick) and identify species (thin)
-blood smears can be obtained every 8 hours for several days if malaria is suspected
malaria symptoms
-mosquito borne febrile illness
-caused by plasmodium protozoa
-associated with rupture and release of merozoites during blood stage of infection
-classically paroxysms of chills, fevers, and diaphoresis occur, every second day “tertian fever” from P. vivaz, P. falciparum, and P. ovale, and either 3rd day “quarten fever’ from P. malariae
-young children and pregnant women are at greater risk for greater disease
-uncomplicated- paroxysmal fever, chills, malaise, arthralgia, myalgia, headaches, diaphoresis, tachycardia, tachypnea, abdominal pain, splenomegaly, nausea, vomiting
-severe- AMS, seizures, shock, adult respiratory distress syndrome (ARDS), metabolic acidosis, hemoglobinuria, renal failure, hypoglycemia, hepatic failure, coagulopathy, sever anemia
malaria treatment
-tailored to Plasmodium spp., severity of illness, pregnancy status, drug susceptibility, based on geographic region of infection
-uncomplicated -> atovaquone/proguanil, artemether/lumefantrine, quinine sulfate plus doxycycline, mefloquine (mefloquine can cause neuropsychiatric reactions)
-if chloroquine resistance is NOT an issue -> uncomplicated malaria can be treated with chloroquine phosphate or hydroxychloroquine
-P. vivax and P. ovale require longer duration of treatment with primaquine to eradicate liver hypnozoites
-primaquine can cause hemolytic anemia in G9PD- deficient pts and cant be used in pregnancy
-severe malaria should be treated with IV quinidine gluconate plus doxycycline or clindamycin
malaria prevention
-avoid mosquitos
-malarial prophylaxis indicated for travelers to endemic regions and recommendations often vary between WHO and CDC
-species of Plasmodium and presence/absence of chloroquine resistance are factors consider when considering prophylaxis
-medications typically started 1 day to 2 weeks before travel and continued up to 4 weeks after return
-CDC website can be referenced for country specific recommendations
toxoplasma infection
-parasitic protozoan infection
-caused by toxoplasma gondii and causes asymptomatic or mild flulike illness in immunocompetent pts
-parasite can remain in host in inactive state and become reactivated if immune system becomes compromised
-can be passed to fetus if mother contracts infection just before or during pregnancy
-maternal infection with toxoplasmosis can cause spontaneous abortion, stillbirth, congenital infection
-congenital infections range in severity from mild to severe and may not manifest until much later in childs life
-classic triad of congenital toxoplasmosis includes chorioretinitis, hydrocephalus, intracranial calcifications
-congenital infections that manifest later in life include chorioretinitis (potentially leading to blindness), mental retardation, and/or seizures
toxoplasma infection prevention
-during pregnancy- encouraged not to clean litter box, feed cat only dry or canned cat food, keep cat indoors
-refrain from getting any new cats or kittens prior to or during pregnancy
-litter box should be cleaned daily -> takes 1-5 days for toxoplasma parasite in cat feces to become infectious
-proper handwashing with soap and water after exposure to uncooked meats, sand, soil
amebiasis
-causative- entamoeba histolytica
-fecal-oral tranmission of infectious cysts
-cysts can survive outside human body for weeks-months
-transmitted via person to person or ingestion of contaminated food or water
-once ingested -> cysts mature into trophozoites and typically invade colonic mucosa
-incubation -2-4 weeks
-worldwide- more common in tropics and developing nations with poor sanitation
-amebiasis is spectrum diarrheal illness ranging from asymptomatic carrier states to hemorrhagic colitis and dysentery
-hematogenous spread may cause extraintestinal disease
amebiasis signs and symptoms
-onset is gradual
-fever, malaise, abdominal pain, weight loss, bloody diarrhea
-characteristic flask shaped ulcers in colonic mucosa and rarely large granulomatous masses (amebomas) resembling cancerous tumors may form
-toxic megacolon and perforation are potential complications of severe acute disease
-potential for invasive, extraintestinal disease secondary to hematogenous spread to liver, brain, lungs
-amebic liver abscesses are most common extraintestinal manifestation and cause fever, chills, weight loss, right upper quadrant pain
-abscesses may enlarge to point of rupture
amebiasis diagnosis
-microscopy may identify cysts and/or trophozoites of amebas, but cannot differentiate between pathologic and nonpathologic species
-stool antigen and PCR testing confirms dx
-serology helpful in dx of amebic liver abscess and extraintestinal disease
-imaging for liver abscess includes CT, US, and/or MRI
-abscesses may be aspirated by interventional radiology and sent for microscopy, antigen, and/or PRC testing
amebiasis treatment
-asymptomatic pts should be treated to prevent disease progression and transmission to others
-luminal agents, such as paromomyxin, iodoquinol, and diloxanide, poorly absorbed from GI tract and are effective cyst eradication
-mild to moderate disease-> oral metrodazole or tinidazole -> followed by paromomycin or iodoquinol to kill luminal dwelling cysts
-more severe diarrheal disease and extraintestinal disease -> intravenous metronidazole or tinidazole and followed by paromomycin or iodoquinol to kill lumina dwelling cysts
giardiasis
-aka beaver fever
-causative- Giardia lamblia aka Giardia intestinalis
-reservoir- humans, beavers, dogs
-incubation- 1-3 weeks
-worldwide- number 1 intestinal parasites disease in US
-flagellated intestinal protozoan responsible for acute and chronic outbreaks of GI and diarrheal illnesses worldwide
-contracted via ingestion of infectious cysts through fecal oral route often from consuming contaminated food or water
-disease more common in children and middle aged adults
-backpacker, campers, international travelers, people in childcare centers, MSM are at higher risk
giardiasis clinical dx and treatment
-ovum and parasite stool studies x3 can be obtained
-stool antigen and nucleic acid amplification testing (NAAT) available too
-tinidazole 2 g by mouth once, nitazoxanide 500 mg 2x a day x3, or metronidazole 250 mg 3x a day x5
-proper sanitation and handwashing limits spread
-water can be boiled, filtered, halogenated (chlorine or iodine) to eliminate and/or decrease number of cysts
giardiasis signs and symptoms
-may be asymptomatic, acute, self limiting, chronic
-acutely- pts may have abdominal pain and cramping, malaise, upper GI upset, diarrhea
-diarrhea often described as green, frothy, foul smelling, often floats, indicating malabsorption
-chronically- pts may develop anorexia, weight loss, malabsorption, B12 deficiency, postinfectious IBS, lactose intolerance
hookworm
-causative- Necator americanus, ancylostoma duodenale
-contracted from exposure to fecal contaminated soil
-filariform larvae mature and enter through exposed skin (usually feet)
-migrate hematogenously to lungs where they are coughed up and swallowed
-larvae penetrate mucosa of small intestine -> mature -> reproduce
-adult N/ americanus worms can live up to 5 years while A, duodenale lives for 6 months
-eggs (rhabditiform larvae) are produced and they are excreted with feces
-worldwide, uncommon in US
-N, americanus- North and South american, sub-saharan africa, southeast asia, china
-A. duodenale- middle east, north africa, india
-annual rainfall of 5-60 inch required for regions to support hookworm
hookworm
-nematode infection of human GI
-causes intestinal inflammation leading to iron deficient anemia and protein deficiency
-mild infections - often asymptomatic
-acute infections may present with ground itch and GI symptoms -> nausea, vomiting, diarrhea
-chronic infections cause iron and protein deficiency secondary to blood loss from feeding worms
hookworm dx
-lab tests reveal eosinophila and microcytic anemia
-serial stool samples are diagnostic
-should be notes that eggs from 2 species are indistinguishable
hookworm treatment
-albendazole, mebendazole, pyrantel pamoate
-iron supplements should be prescribed to treat anemia
-avoid walking barefoot in soil
pinworms
-causative- enterobius vernicularis
-eggs deposited in perianal area by female worms (usually at night)
-perianal itching cause autoinfection and/or eggs passed on to others via contaminated fingernails, close contact, aerosolization, bed linens
-once ingested -> eggs hatch in duodenum and begin to mature in bowel
-adult male and female worms mate in terminal ileum, cecum, appendix
-male worm typically dies in cecum and passed out with stooling
-female worm migrates to perianal area to lay eggs and die
-circle of life is completed
-each female produced an average of 10,000 eggs
-worldwide- most common helminth infection in US and western europe
-human nematode infection caused by ingestion of eggs from perianal area of infect individuals
-anal itching (pruritus ani) and scratching aids transmission
-disease most common in children 5-10 years
pinworm testing and symptoms
-scotch tape test or paddle test revealing presence of eggs is diagnostic
-adhesive tape or paddle placed on several spots around perianal area -> remove eggs that are identified on microscopy
-samples taken over several days preferably first thing in morning
-eggs are translucent, bean shaped, measure 50-60 x 20-30 um
-most infections are asymptomatic
-pruritus ani most common symptoms and is worse at night
pinworm treatment
-albenbazole, mebendazole, pyrantel pamoate
-at least 2 rounds, 2 weeks apart, required
-medication only kills the adult worm not the eggs!
-humans are only animals that get infected but household pets may carry eggs on fur
tapeworm
-causative- taenia saginata
-beef tapeworm
-contracted from ingestion of infected measly beef containing cysticerci
-once inside human intestines -> cysts hatch -> release protoscolices -> attach to intestinal wall -> become heads (scolex) of adult tapeworms
-degraded proglottids release eggs into passed stools
-contaminated human feces are consumed by cattle -> eggs hatch in GI and then larvae seek out striated muscle, liver, and/or lungs to form cysticerci
-worldwide, common in central and south america, europe, africa, asia
-beef tapeworm is cestode infection of human GI tract which is often asymptomatic
tapeworm symptoms
-often asymptomatic
-significant worm may burden may cause nausea, abdominal discomfort, malaise
-acute fever, chills, rigors, malaise, myalgia, headache, rhinorrhea, nonproductive cough
-nausea, vomiting and diarrhea may occur in some pts -> more so in children
-immunocompromised, extremes of age, pregnant, long term care pts, preexisting conditions -> more likely to have severe disease complications
-pneumonia from influenza virus directly or secondarily from bacteria is one potential complication
-worms can live for several years
-produce eggs that survive about 2 months in environment
