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Fungi and Parasites > Protozoa > Flashcards

Protozoa Flashcards

1
Q

List the protozoa (11)

A 
Babesia
Cryptosporidium
Entamoeba histolytica 
Girardia lamblia
Leishmania donovani
Naegleria fowleri
Plasmodium (Vivax, Ovale, Falciperum)
Toxoplasma gondii
Trichomonas vaginalis
Typanosoma brucei (+ 2 subspecies)
Trypanosoma cruzi
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2
Q

Babesia presentation

A

1) Fever - babesiosis often presents like malaria with high fevers and shaking chills
2) Hemolytic anemia - it infects and reproduces in RBCs. Damage leads to lysis
3) Maltese Cross - can be seen inside RBCs as maltese crosses on blood smear - the cross comes from 4 merozoites that are budding asexually

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3
Q

Babesia transmission

A

Northeastern USA

Ixodes tick - same as borrelia (Lyme) - dual infection can occur

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4
Q

Cryptosporidium transmission

A

Ingestion of oocytes in food or water - can complete its life cycle in 1 host resulting in cysts that are excreted in feces. Oocytes from food/water excyst in the SI and cause damage to intestinal epithelial tissue

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5
Q

Cryptosporidium presentation

A

Intestinal epithelial tissue damage due to excystation of oocytes in SI

Outbreaks of diarrhea in water supply

Mild disease in immuno-competent people - only an acute short-term infection.

Immunocompromised show severe diarrhea. AIDS patients show severe diarrhea - it is the most common organism isolated from HIV+ patients presenting with diarrhea

Acid Fast cysts - acid fast stain to confirm.

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6
Q

Entamoeba transmission

A

Ingestion of cysts in food/water - cysts can survive outside host in water, soil, foods for months

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7
Q

Entamoeba presentation

A

Bloody diarrhea and/or liver abscesses

Bloody diarrhea - inside GI tract, trophozoites can invade the intestinal wall and cause severe bloody diarrhea

Flask-shaped ulcers of intestinal wall - can help in diagnosis

RUQ pain - from intestinal invasion and liver abscess

Anchovy paste appearance of abscesses

Cyst with 4 nuclei

Liver abscess - after invading intestinal wall, it can invade blood and go to liver

RBCs inside cytoplasm of trophozoite helps visualization for diagnosis - they ingest RBCs

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8
Q

Entameoba Tx

A

Metronidazole - alters oxidative phosphorylation patterns resulting in death

Iodoquinol - poorly absorbed in GI so it remains in intestinal lumen - acts by chelating ferrous ions essential for protozoan metabolism

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9
Q

Giardia transmission

A

Seen in campers (drink unfiltered water)

Ingestion of cysts - life cycle starts with a noninfective cyst that is excreted in the feces of an infected person. Cyst can survive for weeks-months and can contaminate food or water sources.

Fecal-oral transmission: Daycare centers, mental hospitals (poor hygiene practice)

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10
Q

Giardia presentation

A

Infects SI - results in severe inflammation and villous atrophy. Since the majority of nutrients get absorbed in SI, the infection can cause steatorrhea

Bloating - common symptom. Colonizing the gut results in severe inflammation and villous atrophy

Flatulence - common. Can have foul-tasting belches that are so nauseating that they induce vomit.

Fatty diarrhea - characteristic fatty stool due to lower absorptive capacity in SI

Crescent shaped protozoa adjacent to epithelial brush borders on biopsy***

Patients are predisposed if they have low IgA - IgA is important for mucosal immunity (esp in GI tract) - these people can develop chronic disease and are at higher risk of acute infection

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11
Q

Giardia Tx

A

Metronidazole

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12
Q

Leishmania transmission

A

Sandfly - intermediate host, humans are definitive host. Transmission is through bite from sandfly

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13
Q

Leishmania presentation

A

Causes visceral Leischmaniasis

1) Hepatosplenomegaly
2) Spiking fevers - pyrexias - continuous or remittent - a distinguishing feature*
3) Skin pigmentation - heavy skin discoloration - “black fever”

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14
Q

Leishmania diagnosis

A

Macrophages with amastigotes - direct visualization of amastigotes inside of macrophages

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15
Q

Leishmania Tx

A

Amphotericin B - India, South America, Mediterranean causes up to 95%

Oral Miltefosine - can cause birth defects

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16
Q

Naegleria transmission

A

Swimming in freshwater lakes - usually found in warm bodies of fresh water (ponds, lakes, rivers, hot springs). Can also be in soil or underchlorinated swimming pools

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17
Q

Naegleria presentation

A

causes a rapidly progressing Meningoencephalitis - “Brain-eating Amoeba”

Travels through cribiform plate - once in nasopharynx it attacks brain and CNS.

95% fatality rate in diagnosed patients even if treated

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18
Q

Naegleria Dx

A

Amoebas in CSF - on lumbar puncture

Flagellation test confirms Naegleria ameboid presence

19
Q

Naegleria Tx

A

Amphotericin B

20
Q

What disease is caused by plasmodium?

A

Malaria

21
Q

Plasmodium (general) presentation

A

Fever, HA, anemia

Cyclic Fever - cycles of fevers and chills caused by simultaneous waves of plasmodium merozoites escaping and infecting RBCs

HA

Anemia - it infects RBCs during erythrocytic stage and multiples within them causing lysis and anemia

Splenomegaly - circulating infected RBCs are identified and destroyed in the spleen and can lead to enlargement

Diagnose with blood smear - direct visualization of parasites within RBCs

22
Q

Plasmodium (general) transmission

A

Always has 2 hosts

Vector is usually mosquito (Anopheles mosquito)

All plasmodium species causing malaria in humans transmitted through this mosquito

23
Q

General plasmodium Tx

A

Chloroquine - Prevents development of plasmodium parasites in RBCs - used for prevention and Tx

This form does NOT kill Plasmodium Vivax or Ovale parasites that remain dormant in liver

Also, resistance to this drug is growing

Mefloquine - if traveling to area where resistance is high, use this.

24
Q

P. malariae

A

Milder form of malaria

Fever every 3 days

25
Q

P. Vivax and P. Ovale

A

Malaria

Cyclic fever every 2 days

Also associated with persistent liver stages that allow relapse up to 5 years after elimination of erythrocytic stage

26
Q

Duffy antigen binding site

A

Duffy antigen is a protein on surface of RBCs and is a nonspecific receptor for many chemokines

The receptor is also the receptor for P Vivax. Individuals who do not express this receptor may be resistant to P Vivax form of malaria (black people)

27
Q

P. Vivax and P. Ovale Tx

A

Primaquine - treats dormant form in liver

28
Q

P. Falciparum

A

Most severe form of malaria

Vast majority of malaria deaths are from this dude (the others are rarely fatal)

Daily cycles of fever that are almost continuous

Can cause surface properties of infected RBCs to change leading them to adhere to vessels. This causes obstruction of the microcirculation and can occlude capillaries in brain, kidney, lungs.

29
Q

Toxoplasma transmission

A

cysts in meat or cat feces - undercooked meat or fecal-oral

Also, vertical (TORCH)

30
Q

Toxoplasma presentation

A

1) Brain abscess in HIV patients - immunocompromised can develop severe toxoplasmosis including encephalitis and brain abscesses due to cyst formation in the tissue

Brain lesions are ring-enhancing

2) Crosses placenta in pregnant women (TORCH) - infants present with classic triad: chorioretinitis, hydrocephalus, intracranial calcifications

31
Q

What is the #1 cause of ring-enhancing brain lesions in HIV+ patients?

A

Toxoplasmosis

32
Q

Toxoplasmosis Tx

A

Pyrimethamine - interferes with THF acid synthesis by inhibiting DHF reductase which is needed for DNA and RNA synthesis

+

Sulfadiazine - sulfonamide antibiotic - used in combo with pyrimethamine to treat toxoplasmosis

33
Q

Trichomonas presentation

A

Vaginitis - inflammation resulting in discharge, itching and pain.

Foul-smelling greenish discharge

Vaginal pruritis

Strawberry cervix - some women will have an erythematous cervix with punctate areas of exudation caused by capillary dilation from inflammation

34
Q

What does Trichomonas look like?

A

Demonstrates corkscrew motility on wet mount

35
Q

Trichomonas Tx

A

Metronidazole

36
Q

What disease is caused by Trypanosoma brucei?

A

African sleeping sickness

37
Q

African Sleeping Sickness transmission

A

Tsetse fly - Large brown biting fly that is host and vector. Infected fly injects trypomastigotes into skin tissue during bite.

Very painful bite

Endemic to Africa

38
Q

African Sleeping Sickness presentation

A

Recurring fever - during first stage. Due to antigenic variation and evasion of immune system

Enlarged lymph nodes - often to very large sizes. extensive swelling of nodes along back of neck are called Winterbottom’s Sign - characteristic***

Encephalitis - inflammation of brain when it invades BBB and attacks CNS

Confusion, disruption of sleep/wake cycle with episodes of fatigue interrupted by mania

39
Q

Trypanosoma brucei subspecies

A

1) Gambiense - found in west/central africa

> 95% of African Sleeping Sickness cases

This form often causes chronic infection where person is infected for months to years without any major sign of disease. When symptoms come up, the person usually already had advanced disease.

2) Rhodesiense - eastern/southern africa

40
Q

African sleeping sickness Tx

A

Suramin - for blood-borne disease - can be used alone when there is only evidence of the blood borne disease

Melarsoprol - for CNS penetration. This drug can penetrate BBB

41
Q

What disease is caused by Trypanosoma cruzi?

A

Chagas Disease

42
Q

Chagas transmission

A

Reduviid bug - the Kissing Bug

It deposits feces on surface of skin and then bites the area. The bite is painless. Human scratches area which facilitates penetration.

Predominately South America/Central America - very common there (11 million maybe)

43
Q

Chagas presentation

A

Acute phase - patients present with local swelling at site of entry. Symptoms usually resolve spontaneously, but infection can persist and enter a chronic phase

Chronic phase - can cause damage to heart, esophagus, colon

Romana’s Sign - classic marker of Chagas (acute) - swelling of eyelids near the bite or where bug feces was accidentally rubbed into eye

Dilated cardiomyopathy

Megacolon - Chagas causes this by damaging Auerbach’s plexus in walls of intestinal tract. Destruction of Auerbach’s plexus leads to loss of smooth muscle tone and gradual dilation.

Megaesophagus - same. Damage Auerbach’s in esophageal wall.

Diagnose with blood smear for direct visualization (It has a flagella)

44
Q

Chagas Tx

A

Nifurtimox - not effective for symptoms caused by chronic infection

Side effects = skin discoloration, brain toxicity, GI discomfort

Fungi and Parasites (5 decks)

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