EXAM 3- MCQUAID - PARASITIC INFECTIONS

im so sorry she's insane.

A parasite is an organism that lives on or in another organism and harms it.

The extent of host harm depends on what 3 things?

1. parasitic load

2. host’s nutritional status

3. host’s immune function

DEFINE the following host-parasite relationships:

• definitive host

• intermediate host

• reservoir host

• vectors

• definitive host: parasite replicates within the host

• intermediate host: larva and other asexual stages of parasite life cycle occur within the host

• reservoir host: carry or harbor parasites that may cause disease to a secondary host

• vectors: can be definitive or intermediate host, aid in transmission of parasite to secondary host

What are the 3 main types of parasitic infections?

• protozoa

• helminths

• ectoparasites

What is the most common cause of parasitic diarrhea?

giardia

Risk factors for giardia?

(idk how imp)

high-risk:

• infants, young kids

• travelers

• international adoptees

• immunocompromised

• pts. with CF

other RFs: MSM, swimming/drinking from natural bodies of water, contact with kids in diapers

How is giardia transmitted?

3 ROUTES

1. waterborne transmission- MAJOR SOURCE

2. foodborne transmission

3. person-person transmission

Describe the etiology of each of the following protozoa:

Parasite	Etiology (aka what kind of parasite)
Giardia species
Entamoeba hystolytica other names: amebiasis, amebic dysentary
Babesia species
Trypanosoma cruzi
Plasmodium species

(idk how important)

Parasite	Etiology
Giardia lamblia other names: Giardia duodenalis or intestinalis	flagellated protozoan causes infection when cysts ingested incubation 1-2w
Entamoeba hystolytica other names: amebiasis, amebic dysentary	anaerobic protozoan causes infection when cysts ingested incubation 2-4w
Babesia species (includes B. microti, divergins, venatorum, crassa)	protozoan parasite that feeds on red blood cells
Trypanosoma cruzi	protozoan parasite that feeds on blood and lymph
Plasmodium	unicellular, obligate parasite

What is the presentation of Giardia?

• acute, chronic or asymptomatic?

• common s/sx?

• chronic s/sx?

• can be acute, chronic, or asymptomatic

• common s/sx:

  • diarrhea

  • others: malaiase, fever, n/v, weight loss,

• chronic s/sx:

  • STUNTED GROWTH IN CHILDREN

  • weight loss, depression, loos stools, steatorrhea

May suspect giardiasis when a pt. has been experiencing what?

experiencing foul-smelling, fatty diarrhea, especially >1 week or possesses symptoms of chronic giardiasis and has known risk factors

What are the tx options for giardia (no pregnancy)? PREFERRED DRUG?

• TINIDAZOLE —> PREFERRED

• metronidazole

• nitazoxanide

• albenazole

What are the tx options for giardia IN PREGNANCY? PREFERRED DRUGS FOR EACH TRIMESTER?

• paraMOMycin—> 1st trimester

• Metronidazole—> 2nd or 3rd trimester

  • alternative: tinidazole (only if metro c/i)

  • reminder cannot use metro or tini in 1st trimester!!!!

NOTE: lowkey since she asked about paramomycin in a practice question, i feel like she might ask about metronida

What are some counseling points for Giardia?

• do we tx asap? or wait till diagnosis?

• what should be avoided during tx?

• do we administer drugs w/ or w/out food?

• wait to treat until confirmed diagnosis

• avoid areas of natural water and swimming pools

• administer regimens with food

Risk factors for Entamoeba hystolytica:

• tropical/subtropical countries

• migrants/travelers

• host factors—> genetic susceptibility, age, immune status

How is Entamoeba hystolytica transmitted?

3 ROUTES

1. waterbourne

2. foodbourne

3. person-person

Note: same as giardia

90% of entamoeba hystolytica infections are _______________.

asymptomatic

common s/sx of entamoeba hystolytica?

• BLOODY DIARRHEA!!!!!!!!!!!!!!!!!!!!!!

• others: cramps, flatulence, stomach ulcers, weight loss

What is the preferred method to diagnose entamoeba hystolytica?

antigen testing (quick, easy, sensitive, specific)

Tx for entamoeba hystolytica is based on severity of symptoms:

• asymptomatic or mild may be treated with ____________________.

• severe GI requires treatment with _______________________.

• asymptomatic or mild may be treated with luminal amebicides.

• severe GI requires treatment with tissue amebicides.

List the drugs that are luminal amebicides:

• preferred drug for entamoeba?

• PARAMOMYCIN—> PREFERRED, only drug in pregnancy

• Iodoquinol

• Diloxanide furoate

List the drugs that are tissue amebicides:

• preferred drug for entamoeba?

• metronidazole—> PREFERRED

• tinidazole

What species of Babesia is most common in the US?

Babesia microti

How are Babesia species transmitted?

black-legged or deer TICK

What is the tx of Babesia microti?

• asymptomatic

• mild-mod

• severe

• pregnant

• asymptomatic: no tx

• mild-mod: PO azithromycin or atovaquone

• severe: IV azithromycin + atovaquone

• pregnant: IV clarithromycin + quinine

  • preferred bc this therapy crosses placenta

Trypanosoma cruzi can cause what disease? manifestations of this disease?

• Chagas disease

• manifestations: cardiomyopathy and GI disease

ONE of the ways Trypanosoma cruzi can be transmitted is through what vector?

triatomine bug

What is the tx for Trypanosoma cruzi?

• Benznidazole

• Nifurtimox

Plasmodium causes WHAT DISEASE? WHAT IS THE VECTOR?

• causes malaria

• vector: mosquito

What is the most common species of Plasmodium?

Which species has the highest mortality rates?

• most common—> P. vivax

• highest mortality—> P. falciparum

What are the phases of symptoms with malaria?

• prodromal phase (HA, anorexia, malaise, fatigue, myalgia, fever, chills, rigor)

• cold phase (cyanosis, pallor)

• hot phase (severe fever)

• sweating phase

What is the GOLD standard for diagnosis of malaria?

microscopy

For prophylaxis of malaria, what is the preferred first-line agent?

trick question—> there is none (choice of drug based on pt. characteristics)

Regimens for prophylaxis of malaria are either _________ or __________ dosing.

Regimens for prophylaxis of malaria are either once daily or once weekly dosing.

What type of regimen is safe for prophylaxis of malaria in PREGNANCY?

a. once weekly

b. once daily

a. —> ALL once daily meds for prophylaxis are C/I IN PREG

What are the daily regimen options for prophylaxis of malaria?

• duration????

• atovaquone/proguanil: start 1-2 days before travel, d/c after 7 days

• doxycycline: start 1-2 days before travel, d/c after 28 days

• primaquine: start 1-2 days before travel, d/c after 7 days

Atovaquone/proguanil is C/I if CrCl <___ml/min.

30

What malaria drug used for prophylaxis has a risk of photosensitivity?

doxycyline

Primaquine is most effective against what Plasmodium species?

When is Primaquine C/I?

• most effective against P. vivax

• C/I in G6PD-deficiency

What are the weekly regimen options for prophylaxis of malaria?

• duration????

• mefloquine: begin >2w before travel, d/c after 4 weeks

• chloroquine: begin 1-2w before travel, d/c after 4 weeks

Mefloquine and Chloroquine have what administration considerations?

must be taken with FOOD (mefloquine also 240ml of water)

When is mefloquine C/I?

psychiatric disorders or seizure disorders

Treatment of malarial infection _______ produce immunity.

a. does

b. doesn’t

b. reinfection may occur

What is the TREATMENT for malaria?

• mild-mod

• severe

• mild-mod

  • atovaquone/proguanil

  • quinine sulfate + doxy or tetra or clindamycin

  • mefloquine

  • chloroquine

  • hydroxychloroquine

• severe

  • ARTESUNATE IV preferred tx

  • if outside the US and can’t get artesunate IV—> may use artemether IM or quinine IV

If there is known prevalence of P. falciparum artemisinin resistance, severe malaria treatments include:

artesunate IV + quinine IV

PRACTICE:
A patient is traveling and is concerned about contracting malaria. They tell you that their travel date is in 3 days. There is no concern for drug- resistance in the area that they plan to travel to. Please select the most appropriate initial regimen for malaria prophylaxis in this patient:

A. Mefloquine 228 mg PO, 1-2 days before departure

B. Hydroxychloroquine 620 mg as a loading dose

C. Doxycycline 100 mg PO, 1-2 days before departure

D. Chloroquine 300 mg PO, 1-2 days before departure

C. (since leaving in 3 days you want to chose a daily regimen—> only daily regimen listed is doxy)

What are the major helminths that cause parasitic infections?

(more of an FYI)

• Hookworms- Ancylostoma duodenale, Necatar americanus

• Round worm- Ascaris lumbricoides

• Pinworms/threadworms- Enterobius vermicularis

• Tapeworm- Taenia solium

How are each of the following transmitted:

Helminth	Transmission
Hookworms- Ancylostoma duodenale, Necatar americanus
Round worm- Ascaris lumbricoides
Pinworms/threadworms- Enterobius vermicularis
Tapeworm- Taenia solium

(idk how imp)

Helminth	Transmission
Hookworms- Ancylostoma duodenale, Necatar americanus	soil transmitted 3 factors contribute to transmission: fecal contaminated soil, soil conditions favorable to larvae, contact of human skin with soil
Round worm- Ascaris lumbricoides	waterborne, foodborne, less common airborne
Pinworms/threadworms- Enterobius vermicularis	soil transmitted eggs can be ingested from soil, foods, bed sheets autoinfection
Tapeworm- Taenia solium	consumption of undercooked beef or pork that is contaminated

What is the BIGGEST risk factor for hookworm infection?

walking barefoot in soil

Describe the presentation of each of the following helminths:

Helminth	Presentation
Hookworms- Ancylostoma duodenale, Necatar americanus
Round worm- Ascaris lumbricoides
Pinworms/threadworms- Enterobius vermicularis
Tapeworm- Taenia solium

(idk how imp)

Helminth	Presentation
Hookworms- Ancylostoma duodenale, Necatar americanus	asymptomatic itching, irritation if severe—> pain, d, anemia, protein def
Round worm- Ascaris lumbricoides	USUALLY ASYMPTOMATIC intestinal blockage, impaired growth, can migrate to lungs
Pinworms/threadworms- Enterobius vermicularis	often asymptomatic perianal itching if heavy worm burden: pain, n/v, anorexia, restlessness, insomnia, behavior changes
Tapeworm- Taenia solium	pain, anorexia, weight loss, n

Describe how each of the following helminths are DIAGNOSED:

Helminth	DIAGNOSIS
Hookworms- Ancylostoma duodenale, Necatar americanus
Round worm- Ascaris lumbricoides
Pinworms/threadworms- Enterobius vermicularis
Tapeworm- Taenia solium

Helminth	DIAGNOSIS
Hookworms- Ancylostoma duodenale, Necatar americanus	microscopy
Round worm- Ascaris lumbricoides	microscopy
Pinworms/threadworms- Enterobius vermicularis	TAPE TEST aka apply to perianal region for 3 consecutive nights visual under microscope
Tapeworm- Taenia solium	microscopy (3 stool samples from 3 different days)

What is the treatment for Hookworms and Ascaris lumbricoides?

• dosing?

• pregnancy?

• counseling points?

• MEBENDAZOLE

  • hookworms: 500mg PO x 1 dose

  • ascaris: 100mg PO BID x 3d

  • in preg—> delay tx until 3rd trimester

• counseling pts.

  • take without regard to food

  • tablets can be swallowed, chewed, crushed, etc.

  • may cause GI upset

Which helminth is HIGHLY contagious, especially within households?

enterobius vermicularis aka pinworms aka threadworms

What is the tx for Enterbius vermicularis or pinworms?

• which is available OTC

• can you use these drugs in pregnancy?

• pyrantel pamoate- OTC available

• mebendazole

• albendazole

• all these drugs may be used in 2nd or 3rd trimester if benefits>risks

In patients with enterobius vermicularis, who else should be treated?

ALL MEMBERS OF HOUSEHOLD

For self-treatment of enterobius vermicularis with pyrantel pamoate, what are some counseling points?

• hand hygeine

• fingernail care

• clean bedding in hottest water possible

What is the treatment for Taenia solium aka tapeworms?

• preferred?

• praziquantel—> preferred

• albendazole

What are the administration considerations with Praziquantel?

• cannot be chewed

• administer with water, 30 min before or 2hr after meal

Name the 2 main ectoparasites:

• pediculus humanus capitis- lice

• sarcoptes scabei- scabies

Describe the transmission of ectoparasites:

Ectoparasite	Transmission
pediculus humanus capitis- lice
sarcoptes scabei- scabies

Ectoparasite	Transmission
pediculus humanus capitis- lice	DIRECT CONTACT WITH THE HEAD OF INFECTED PERSONS (lice do not jump, fly, or use pets as vectors)
sarcoptes scabei- scabies	person-person thru skin

Describe the symptoms of ectoparasites:

Ectoparasite	Symptoms
pediculus humanus capitis- lice
sarcoptes scabei- scabies

Ectoparasite	Symptoms
pediculus humanus capitis- lice	feeling of tickling or movement in hair pruritis due to rxn to lice saliva lesions
sarcoptes scabei- scabies	pruritis (worse at night) lesions or scratches

Describe the diagnosis of ectoparasites:

Ectoparasite	Diagnosis
pediculus humanus capitis- lice
sarcoptes scabei- scabies

Ectoparasite	Diagnosis
pediculus humanus capitis- lice	WET or DRY combing wet combing more sensitive visual inspection
sarcoptes scabei- scabies	microscopy

What is the tx for LICE?

• how long is it left on the hair?

• Rx: Permethrin

• Malathion

• Spinosad

• Rx: Ivermectin

  • OTC: Sklice

• LEAVE ON HAIR 10 MIN

What is the tx for SCABIES?

• preferred?

• when do you wash them off?

• avoid what when applying?

• PERMETHRIN—> PREFERRED

• Crotamiton

  • adults wash off after 24 hrs

  • children apply once daily for 3 days, do not rinse off between applications but 48h after final application

    • AKA DON’T rinse off between doses

• avoid contact with eyes