Protozoal and Fungal Infections

Question 1

Malaria

Answer 1

-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.

Question 2

malaria: areas primarily infected and incubation

Answer 2

-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

Question 3

malaria testing

Answer 3

-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

Question 4

malaria symptoms

Answer 4

-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

Question 5

malaria treatment

Answer 5

-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

Question 6

malaria prevention

Answer 6

-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

Question 7

toxoplasma infection

Answer 7

-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

Question 8

toxoplasma infection prevention

Answer 8

-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

Question 9

amebiasis

Answer 9

-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

Question 10

amebiasis signs and symptoms

Answer 10

-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

Question 11

amebiasis diagnosis

Answer 11

-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

Question 12

amebiasis treatment

Answer 12

-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

Question 13

giardiasis

Answer 13

-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

Question 14

giardiasis clinical dx and treatment

Answer 14

-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

Question 15

giardiasis signs and symptoms

Answer 15

-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

Question 16

hookworm

Answer 16

-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

Question 17

hookworm

Answer 17

-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

Question 18

hookworm dx

Answer 18

-lab tests reveal eosinophila and microcytic anemia
-serial stool samples are diagnostic
-should be notes that eggs from 2 species are indistinguishable

Question 19

hookworm treatment

Answer 19

-albendazole, mebendazole, pyrantel pamoate
-iron supplements should be prescribed to treat anemia
-avoid walking barefoot in soil

Question 20

pinworms

Answer 20

-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

Question 21

pinworm testing and symptoms

Answer 21

-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

Question 22

pinworm treatment

Answer 22

-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

Question 23

tapeworm

Answer 23

-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

Question 24

tapeworm symptoms

Answer 24

-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

Question 25

tapeworm dx and treatment

Answer 25

-serial stool samples looking for eggs are diagnostic
-taenia eggs cannot be distinguished morphologically but their proglottids have different appearance under microscopy
-india ink staining highlights the ovaries and testicles of proglottids
-treatment- praziquantel and niclosamide
-prevention- sanitation and proper hygiene, proper cooking of beef, and/or deep freezing beef long enough to kill cysticerci

Question 26

trichomoniasis

Answer 26

-causative- trichomonas vaginalis
-incubation- 4-28 days
-worldwide
-commonly sexually transmitted disease
-flagellated protozoan
-tends to cause more symptoms in women than men
-50% of infected women are symptomatic compared to 25% men
-infected women often develop symptoms overtime
-men clear infection spontaneously

Question 27

trichomaniasis

Answer 27

-women- pelvic pain, dysuria, dyspareunia, vaginal burning, itching, scant, frothy green, malodourous discharge
-on exam- cervix may have punctate hemorrhages referred to as “strawberry cervix”
-men- if symptomatic present with dysuria and urethral discharge

Question 28

trichomoniasis diagnosis and treatment

Answer 28

-on saline wet mount- motile trichomonads swimming among sea of increased WBC
-vaginal pH > 4.5
-additional tests- nucleic acid amplification test (NAATS), rapid antigen detection test and culture
-culture ahs essentially been replaced by newer molecular detection test
-treatment- metronidazole or tinidazole as single 2 g oral dose
-alternative- metronidazole 500mg orally 2x day for 7 days

Question 29

cryptococcus

Answer 29

-cryptococcus neoformans is yeast that causes disseminated disease in HIV/AIDS pts with low CD4
-often presents subacute meningoencephalitis or meningitis with symptoms including fever, malaise, headaches, often without photophobia and meningismus
-dx confirmed with LP and CSF analysis
-opening pressure is often elevated
-cryptococcal antigen (CrAg) testing performed on both serum and CSF
-CSF microscopy using india ink stainning often show encapsulated budding yeast
-various treatment regimens exist and utilize amphotericin B, flucytosine, fluconazole, and/or combinations thereof

Question 30

histoplasmosis

Answer 30

-aka spelunkers lung, cave disease
-causative- histoplasma capsulatum
-incubation- 3-17 days
-worldwide, predominately found in river valleys
-positive associated with disease and cave exploration
-primarily pulmonary fungal infection caused by dimorphic fungi histoplasma capsulatum
-dimorphic fungi are human pathogen that grows as mold at 25 C and as yeast at 37 C
-spread via inhalation conidia, small single cell molds, swept up into air of disturbed soil, often contaminated with bat guano or faces from starlings or black birds
-once inhaled mold transforms into yeast and begins reproduction in host -> triggers immune response
-disease not contagious (not spread from person to person)

Question 31

histoplasmosis S&S

Answer 31

-majority of pts (≈90%) are asymptomatic or mild -> don’t seek medical attention.
-Symptomatic pts develop fever, chills, headache, substernal chest pain, and nonproductive cough.
-Malaise, fatigue, myalgia, arthralgia, and erythema nodosum may occur.
-can develop pericarditis, mediastinitis, and/or hepatosplenomegaly

Question 32

histoplasmosis treatment

Answer 32

-Mild infections- often self-limiting and resolve spontaneously
- treatment based on severity of illness
-mild to moderate with symptoms lasting longer than 1 month- Itraconazole
-severe- Amphoteracin B

Question 33

pneumocystis

Answer 33

-Pneumocystispneumonia
-AIDS-defining illness
-caused by yeast-like fungus-> Pneumocystisjirovecii.
-fever, chills, nonproductive cough, chest pain, and dyspnea.
-suspected in susceptible individuals with above symptoms, especially in those with lower CD4 counts.
-Chest x-ray normal early on
-often reveals bilateral, ground-glass, interstitial infiltrates in a butterfly pattern.
-Diagnosis confirmed via sputum sample or broncheoalveolar lavage.
-Prophylaxis with TMP/SMX initiated in pts with CD4 counts ≤200
-TMP/SMX- treatment of active disease-> add prednisone for severe

Question 34

candidiasis

Answer 34

-causative- candida albicans
-incubation- varies
-worldwide
-can affect various mucous membrane-> oropharynx, esophagus, and vagina
-Thrush-> pseudomembranous oropharyngealcandidiasis
-thrush is common in infants, pts using inhaled corticosteroids, and immunocompromised (AIDS, immunosuppressants, chemotherapy, etc.)
-Antibiotic use associated with vulvovaginalcandidiasis
-esophagealcandidiasisis associated with HIV/AIDS.

Question 35

candidiasis signs and symptoms

Answer 35

-decreased taste or mild irritation secondary to the pseudomembrane
-Atrophiccandidiasiscan make it painful to denture wearers.

Question 36

candidiasis dx and treatment

Answer 36

-Usually a visual diagnosis
-pseudomembrane easily scraped off using tongue depressor -> will cause mild bleeding
-Samples can be sent for KOH preparation and microscopic examination
-Treatment:
-Nystatin swish and swallow 4x day
-clotrimazole troches placed in the buccal surface of the mouth and allowed to dissolve 5x day are more effective than nystatin

Question 37

uncomplication malaria treatment

Answer 37

-atovaquone/proguanil
-artemether/lumefantrine, quinine sulfate plus doxycycline, mefloquine (mefloquine can cause neuropsychiatric reactions)
-if chloroquine resistance is NOT an issue -> can be treated with chloroquine phosphate or hydroxychloroquine

Question 38

P. vivax and P. ovale treatment

Answer 38

-require longer duration of treatment to eradicate liver hypnozoites
-primaquine
-primaquine can cause hemolytic anemia in G9PD- deficient pts and cant be used in pregnancy

Question 39

Severe malaria

Answer 39

IV quinidine gluconate plus doxycycline or clindamycin