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Special Populations > Parasitic Infections - SP > Flashcards

Parasitic Infections - SP Flashcards

1
Q

Summary

A

Nematodes

  • Pinworms
  • Ascaris
  • Trichuris (Whipworms)
  • Hookworms
  • Strongyloides

Protozoa

  • Giardia
  • Cryptosporidium

Platyhelmethes

  • Trematodes: Schistosomes, Clonorchiasis, Paragonimiasis
  • Cestodes: Diphyllobothrium latum
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2
Q

Meds: Albendazole/Mebendazole

A
  • Binds nematode Beta-tubulin
  • Blocks microtubule assembly
  • Inhibits glucose uptake in worm
  • Death of worm takes days
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3
Q

Albendazole/Mebendazole

A

Albendazole

  • Better GI absorption and high tissue distribution (vs tissue migrating larvae)
  • Take with food
  • Pregnancy class C
  • If STH (soil transmitted Helminths) exceeds 20%, presumptive tx of pregnant women should occur in third trimester with 400 mg albendazole x 1
  • Use during breastfeeding is acceptable

Mebendazole

  • Poorly absorbed, activity vs adults only
  • Both safe > 1yr, probably safe under
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4
Q

Ivermectin

A

-Works by binding nerve and muscle chloride channels causing hyperpolarization, paralysis, and death

Active vs.

  • Strongyloides
  • Ascaris, Trichuris (not hookworm)
  • Lice, Scabies
  • Pregnancy class C, avoid during breast feeding as well
  • Avoid where Loa Loa (African Eye worm is found.. May cause encephalopathy
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5
Q

Helminths: overview

A

Trematodes (flukes)
A. venous: Schistosoma
B. Biliary tract: Clonorchis, Fasciola
C. Lung: Paragominus

Cestodes (tapeworms)
A. Tanea saginata, T. Solium, Hymenolepsis nana

Nematodes (round worms)
A. Intestinal
B. Blood/lymphatic, subcutaneous

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6
Q

Common Intestinal Parasites

A

Nematodes

  • Pinworm
  • Ascaris
  • Trichuris
  • Hookworm
  • Strongyloides

Protozoa

  • Giardia
  • Cryptosporidium
  • Entamoeba hystolytica
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7
Q

Nematode Facts

A

Nonspecific presentation:

  • Often asymptomatic until worm burden is huge
  • Weight loss, GI discomfort
  • Rare for diarrhea or fever

-Look for polyparasitism
-Tropical and subtropical predominance
-Burden greatest in children
Do not multiply in host (2 exceptions)
1. Strongyloides: autoinfection
2. Pinworm: self-reinfection

-Life span: 2 months—5 years

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8
Q

Nematodes

A
  • Eosinophilia occurs with worms penetrating tissue (>450)
  • Larval migratory stage (O+P neg?)
  • GI mucosal penetration

If persistent eosinophilia…

  • Toxocariasis (T. canis) with kids eating dirt
  • Strongyloides (Africa, SE Asia)
  • Schistosomiasis (sub-Saharan Africa)
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9
Q

Nematode: Pinworms (Enterobius vermicularis)

A
  • World wide…tropical and temperate climate
  • Adult habitat: cecum and appendix
  • Gravid female nocturnally deposits eggs onto perianal skin
  • Eggs stick to skin and hatch with 4-6 hours of oxygen
  • Transmission is fecal oral, reinfection, person to person, and fomite
  • Scratching the anus/butt, use scotch tape at night to capture
  • Prepatent period is 3-4 weeks
  • Diagnosis: Scotch tape test (clear), place clear tape on anus at bedtime and check in the morning
  • No eosinophilia
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10
Q

Pinworm Treatment

A
  • Albendazole or mebendazole 100 mg single dose
  • Repeat in 2 weeks
  • Treat entire family
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11
Q

Nematode: Roundworms (Ascariasis infections)

A
  • 1/8 of world is infected
  • Largest nematodes infecting humans (40cm/15-18 inches)
  • Adult habitat: jejunum
  • Obligatory extra-intestinal migration (eosinophilia)
  • Lifespan 1-2 years
  • Most intense in children ages 5-10
  • Larval phase: migration = eosinophilia, pneumonitis (<3weeks)

Adult worm phase:

  • Heavy infection-malnutrition, impaired growth
  • Mild abdominal pain—can create SBO
  • Wandering hepatobiliary-pancreatic ascarisis: pancreatic and liver abscess

-Treatment: Albendazole 400 mg x 1

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12
Q

Nematode: Ascaris

A
  • More prevalent in wet and warm climates
  • Females can lay 200k eggs per day
  • ONLY worm which may be shed in stool, by cough, and by vomiting
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13
Q

Nematode: whipworms (Trichuris trichiuria)

A
  • Adult Habitat: caecum, colorectum
  • No extra-intestinal phase
  • Lifespan 1-3 years
  • 90% are asymptomatic
  • Heavy infections may cause symptoms (peak at 10 y/o)
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14
Q

Whipworm Life Cycle

A
  1. Female produces eggs.
  2. Human feces with eggs deposited in soil, where they lay prepatent for 2-8 weeks
  3. Eggs are ingested and hatch in the small intestine, penetrating villae
  4. Adults migrate to Cecum and cycle repeats
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15
Q

Whipworms: Symptoms & Tx

A
  • 90% asymptomatic
  • Anemia of Chronic Disease
  • Stool frequency 12+/day
  • Chronic abdominal pain

HEAVY INFECTIONS:

  • Tichuris dysentery syndrome
  • Trichuris colitis (mimics IBD)
  • Rectal Prolapse (children)
  • Self limiting w/o reinfection

Mebendazole (100 mg), Albendazole (400 mg)x 3 days

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16
Q

Nematode: Human Hookworms (Necator americanus and Ancyclostoma duodenale)

A
  • 1/10 of world population infected
  • Significant cause of anemia and protein malnutrition
  • Adult habitat: small intestine

Lifespan:

  • 1-3 years for A. duodenale
  • 3-7 years for N. Americanus-
  • Worm burdens do not decline in adult years
  • Pre-Patency: months to a year before symptomatic
  • 600 million cases worldwide
  • Adult worms injure host by causing intestinal blood loss:
  • Anticoagulants, Hemolysins, Hemoglobinases
  • 30-200 microliters bloodloss per day
  • Intestinal bloodloss
  • Iron Deficiency Anemia

Adult size: .5-1 cm
Egg production: 5-20K eggs per day

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17
Q

Hookworms: Clinical Features & tx

A
  • Ground itch in primary infection: enters skin thru foot travels to blood, lungs cough up then ingest and goes into intestine and feces.
  • Abdominal discomfort
  • Progressive iron deficiency
  • Failure to thrive, extreme fatigue
  • Lost work, missed school
  • IQ loss

Albendazole 400 mg qd x 1 dose

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18
Q

Nematode: Strongyloidiasis (Strongyloides stercoralis)

A
  • Causes most mortality in the US
  • 100 million infected world wide
  • Adult habitat: duodenum, jejunem
  • Lifespan: unknown. Ongoing autoinfection
  • Has been documented greater than 60 years
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19
Q

Strongyloides Larvae

A

Rhabditiform

  • Non-infective stage
  • May be in intestine or soil and mature to Filariform

Filariform

  • Infective stage
  • Penetrates skin
  • Penetrates intestine, into blood stream
  • Penetrates alveoli and is then is coughed and swallowed (auto inoculation)
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20
Q

Strongyloidiasis

A
  • Asymptomatic eosinophilia
  • Abdominal pain
  • Dermatitis—larva currens
  • Pulmonary infiltrates with eosinophilia
  • Dissemination with sepsis
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21
Q

Strongyloides Hyperinfection:

A
  • Intestinal perforation
  • Hemorrhagic shock
  • Shock, sepsis, gram negative meningitis
  • Eosinophilia may be limited

Disease Associations

  • Steroid usage (Medrol)
  • Steroid directly effects parasite by upregulating molting hormones
  • Malignancy, solid organ transplants
  • HTLV-1 Infection (Human T-Cell Leukemia Virus): Not HIV
  • PRESENT WITH Malnutrition
22
Q

Strongyloidiasis: dx

A
  • Detection of rhabditiform larvae in stool
  • Larvae output in stool varies
  • Repeat stool samples if suspicious
  • Single stool is 30%, 7 stools = 100%
  • Blood augar plate looking for larval tracks
  • Serologic (IGg) tests (not great)
  • Cannot distinguish current vs prior infection
  • Cross reactions with helminths (ascaris, shisto) filariae
23
Q

Strongyloides Treatment

A

Ivermectin (1st line)

  • Intestinal: 200mcg/kg/d x 2 days…repeat in 14 days
  • Autoinfection and hyperinfection: 200 mcg/kg/day x 7-10 days
  • Taper steroids

Albendazole (2nd line)

  • 400 mg bid x 2 days, repeat if needed
  • Lower cure rate
24
Q

Disseminated Strongyloides:

A
  • Avoid steroid use in refugees and immigrants until knowing results of eosinophil count and stools for O&P, especially methylprednisilone
  • SE Asians have highest risk for Strongyloides
  • Vigorously pursue eosinophilia in refugees and immigrants (Strongyloides in Africa/Asia) and Schistosomiaisis (Africa)
  • Empirically treat eosinophilia with ivermectin if evaluation is negative, particularly those who will receive immunosuppressives
25
Q

Protozoa: Giardiasis (Girardia intestinalis)

A
  • Worldwide
  • Most commonly reported enteric Pathogen
  • Commonly found in immigrant screening (approx 20% of reported cases)
  • Often carried by children in daycare
  • Fecal – oral transmission
  • Person to person (young children)
  • Waterborne: Swimming/drinking untreated surface water
26
Q

Symptoms of Giardiasis

A
  • Diarrhea—95% horrible smelling
  • Fatigue—82%
  • Gas or bloating—74%
  • Abdominal Pain—73%
  • Nausea—62%
  • Asymptomatic 50%
  • Vomiting—rare
  • Chills or fever—rare
27
Q

Giardiasis in MN 2003

A
  • Median Duration—23 days
  • Incubation—7-10 days
  • Symptoms may be intermittent and relapses can occur
  • Highest % cases in children less than 5
  • Cases occur all year with a spike in August-October
28
Q

Giardiasis: tx

A

Metronidazole (flagyl) (vomiting with ETOH, so dont drink) 250 TID x 7 days

Tinidazole 50mg/kg x 1 dose (max dose=2 g)

Nitazoxanide bid 3 days

29
Q

Protozoa: Cryptosporidiosis

A
  • parasite
  • Fecal-oral transmission
  • 7 day incubation
  • Waterborne, daycare outbreaks
  • Cattle contact
  • Responsible for an outbreak involving 369 children, who came in contact with a water fountain at the MN Zoo in 1997.
  • Under-recognized by most labs
  • Routine O+P does not look for Cryptosporidium
  • Must specify Cryptosporidium/Giardia ELSIA
30
Q

Cryptosporidiosis: sxs, tx

A
  • Cramping, nonbloody diarrhea
  • Median 7 days (2-28 days)
  • Chronic diarrhea in HIV
  • FEVER, vomiting common

Limited therapies…

  • Nitazoxanide adult dose 500 bid x 3 days
  • AIDS patients 1 g bid x 14 days
31
Q

Entomoeba hystolytica: Amebiasis, amebic dysentery, Amebic hepatitis

A
  • World wide, tropical and temperate
  • Incidence 0.2-50%, based on sanitary conditions
  • Humans are principal host and source
  • Cyst contaminated food and water cause infection
  • Infective cysts pass out in feces and are immediately infective
  • Immature amebas move to large intestine(primary, cecal, sigmoidal)
  • Excystment (secondary)takes place in Ileum (portal v, liver, lung, brain, skin)
  • Reproduction is by binary fission
32
Q

Entomoeba hystolytica: Symptoms

A

Acute:

  • Fever
  • Dysentery, blood, mucous, necrotic mucosa
  • Abdominal pain

Chronic:

  • Recurrent dysentery/relapsing
  • Abdominal pain, RUQ
  • Amebic hepatitis, abscess, hepatomegaly
  • Less frequently: lung, spleen, brain abscess, and cutaneous lesions
33
Q

Entomoeba hystolytica: Diagnosis

A
  • O+P, cysts(solid stool), trophozoites (diarrhea)
  • Aspiration (abscess)
  • Serology (IFA, ELISA(best)) for specific Ab to E. hystolytica
  • PCR
34
Q

Entomoeba hystolytica: tx

A

Metronidazole (flagyl) 500 mg tid x 10 days

Tinidazole: 500 mg tid x 10 days

Ornidazole: 500 mg bid x 10 days

35
Q

Platyhelmenthes:Trematoda = flukes

A
  • Flattened, leaf like body
  • Simple digestive tract
  • ALL parasitic
  • attachment typically involving hooks and suckers, specialize glands for penetration, and encystment
  • Schistosoma spp.
  • Chlonorchis –human liver fluke
  • Paragonium—human lung fluke
36
Q

Trematodes: Schistosomiasis

A
  • Infections occur via contact with contaminated water
  • Infective stage is called cercaria (free swimming)
  • Cercercaria burrow into skin an matures to schistosomula stage, which migrates to lungs and liver and develops into adult
  • Adult migrates to bladder, rectum, portal vein, intestine, spleen, lungs
  • Mostly Tropical (thankfully)
  • Incubation 14-84 days
  • Often asymptomatic

May involve:

  • Intestinal
  • Respiratory
  • Urinary
  • Neurologic
  • Reproductive
37
Q

Schistosomiasis: Symptoms

A
  • Heavy infections: (Katayama syndrome) fever, chills, lymphadenopathy, hepato/splenomegaly
  • Initial invasion may cause itching (swimmer’s itch)
  • Abdominal pain, bloody diarrhea, constipation, ulceration, portal hypertension
  • Polyuria, dysuria, hematuria,
  • Myalgias
  • Eosinophilia
  • Neurogranulomas (space occupying)
38
Q

Schistosomiasis: Testing

A
  • CBC (wbc, Eos)
  • O+P x 2
  • Tissue biopsy
  • Antischistosomal antibody(can’t differentiate between new and old)
  • UA
39
Q

Schistosomiasis: Treatment

A

-Should occur 6-8 weeks after exposure as Praziquantel is most effective against adult worms

Praziquantel:

  • Adults: 75 mg/kg tid x 1 day
  • Children: 60mg/kg tid x 1 day
  • Repeat in 2-4 weeks

Severe infections: corticosteroids

40
Q

Nematode -> Chlonorchiasis: Chinese Liver Fluke Disease

A
  • Infection in dogs, and other fish eating carnivores in Korea, China, Viet Nam
  • Humans are substitute host
  • Occurs after eating raw or poorly cooked, salted, pickled, smoked, marinated, dried, or poorly processed fish
41
Q

Clonorchiasis: symptoms

A

Asymptomatic in light infections

Heavy:

  • Fever
  • RUQ pain
  • Hepatobiliary fibrosis
  • Cholangiohepatitis
  • Pyogenic cholangitis
  • Cholangiocarcinoma
42
Q

Clonorchiasis: Diagnosis

A
  • Anamnestic recall of eating raw fish
  • Eosinophilia
  • U/S findings
  • CT
  • MRI
  • O+P
  • Ig, not very effective
  • PCR, experimental
43
Q

Clonorchiasis: Treatment

A

Praziquantel: 40 mg/kg x 1 dose or 25mg/kg tid x 3 days

44
Q

Trematodes -> Paragonium: Lung Fluke

A
  • P. westermani, P. heterotremus and P. philippinensis
  • China, Korea, Laos, Phillipines,Thailand, Viet Nam
  • Others found in West Africa, North/Central/South America
  • Common parasite of crustacean-eating animals (cats, dogs, mongooses, opossums, monkeys)
  • Adult flukes live in lungs and lay eggs that are coughed up or swallowed and defecated
  • Eggs reach fresh water and penetrate snails
  • Cercariea (larvae) penetrate crustaceans
  • When crustaceans are eaten (Raw), young worms hatch and penetrate intestinal wall and migrate to lungs
45
Q

Paragonimiasis: Symptoms

A
  • Cough
  • Hemoptysis
  • Chest pain
  • Dyspnea
  • Fever
  • Pleural effusion
  • Pneumothorax
  • Abnormal migration can include, -Abdomen, Sub Q, and frequently the brain (abd pain, headaches, visual impairment, seizures)
46
Q

Paragonimiasis: testing

A
  • Anamnestic recall of eating raw crustaceans
  • Eosinophilia
  • U/S,XR,CT,MRI
  • Consider Tb
  • O+P
  • Ig, not confirmatory
  • PCR, developing
47
Q

Paragonium: Treatment

A

Triclabendazole 20 mg/kg bid x 1 day

Praziquantel 25mg/kg tid x 3 days

48
Q

Cestodes

A

Diphyllobothrium Latum (Fish Tapeworm): mc and largest

Hymenolepsis Nana (Dwarf)

Taenia Saginata (Beef)

Taenia Solium (Pork)

49
Q

Cestodes: Diphyllobothrium latum

A
  • Largest and most common tapeworm in humans
  • Acquired by eating raw or undercooked fish
  • Found in rivers and lakes of Northern Europe, North America and Southern South America
  • Eggs are passed in humans, mature in fresh water within 3 weeks
  • Larva (coracidia) develop and are eaten by copepods , which are eaten by fish
  • Procercoid larvae migrate into gut and muscle and develop into plerocercoid larvae which infect humans
  • Segments of the tapeworm absorb nutrients and have their own digestive system
  • Adults may produce up to a MILLION eggs per day
  • May live 20-25 years
  • Length can exceed 10 meters
50
Q

Diphyllobothrium latum: symptoms

A
  • Usually asymptomatic
  • B 12 deficiency, Pernicious Anemia
  • Constipation, Obstruction
  • Diarrhea
  • Fatigue
  • Subacute combined degeneration of spinal cord (B12 deficiency)
  • Abdominal pain
  • Vomiting
  • Weight loss
  • Cholecystitis, Choledochocystitis
51
Q

Diphyllobothrium latum: Treatment

A

Praziquantel: 10-25 mg/kg qd x 1 day plus
Albendazole 400 mg bid x 14 days

Niclosamide: 2 g (crushed) qd x 1 day, then1g bid x 6 days

Diatrizoic Acid injection into intestinal wall edoscopically

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