Protozoa

Question 1

List the protozoa (11)

Answer 1

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

Question 2

Babesia presentation

Answer 2

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

Question 3

Babesia transmission

Answer 3

Northeastern USA

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

Question 4

Cryptosporidium transmission

Answer 4

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

Question 5

Cryptosporidium presentation

Answer 5

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.

Question 6

Entamoeba transmission

Answer 6

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

Question 7

Entamoeba presentation

Answer 7

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

Question 8

Entameoba Tx

Answer 8

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

Question 9

Giardia transmission

Answer 9

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)

Question 10

Giardia presentation

Answer 10

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

Question 11

Giardia Tx

Answer 11

Metronidazole

Question 12

Leishmania transmission

Answer 12

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

Question 13

Leishmania presentation

Answer 13

Causes visceral Leischmaniasis

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

Question 14

Leishmania diagnosis

Answer 14

Macrophages with amastigotes - direct visualization of amastigotes inside of macrophages

Question 15

Leishmania Tx

Answer 15

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

Oral Miltefosine - can cause birth defects

Question 16

Naegleria transmission

Answer 16

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

Question 17

Naegleria presentation

Answer 17

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

Question 18

Naegleria Dx

Answer 18

Amoebas in CSF - on lumbar puncture

Flagellation test confirms Naegleria ameboid presence

Question 19

Naegleria Tx

Answer 19

Amphotericin B

Question 20

What disease is caused by plasmodium?

Answer 20

Malaria

Question 21

Plasmodium (general) presentation

Answer 21

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

Question 22

Plasmodium (general) transmission

Answer 22

Always has 2 hosts

Vector is usually mosquito (Anopheles mosquito)

All plasmodium species causing malaria in humans transmitted through this mosquito

Question 23

General plasmodium Tx

Answer 23

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.

Question 24

P. malariae

Answer 24

Milder form of malaria

Fever every 3 days

Question 25

P. Vivax and P. Ovale

Answer 25

Malaria Cyclic fever every 2 days Also associated with persistent liver stages that allow relapse up to 5 years after elimination of erythrocytic stage

Question 26

Duffy antigen binding site

Answer 26

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)

Question 27

P. Vivax and P. Ovale Tx

Answer 27

Primaquine - treats dormant form in liver

Question 28

P. Falciparum

Answer 28

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.

Question 29

Toxoplasma transmission

Answer 29

cysts in meat or cat feces - undercooked meat or fecal-oral Also, vertical (TORCH)

Question 30

Toxoplasma presentation

Answer 30

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

Question 31

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

Answer 31

Toxoplasmosis

Question 32

Toxoplasmosis Tx

Answer 32

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

Question 33

Trichomonas presentation

Answer 33

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

Question 34

What does Trichomonas look like?

Answer 34

Demonstrates corkscrew motility on wet mount

Question 35

Trichomonas Tx

Answer 35

Metronidazole

Question 36

What disease is caused by Trypanosoma brucei?

Answer 36

African sleeping sickness

Question 37

African Sleeping Sickness transmission

Answer 37

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

Question 38

African Sleeping Sickness presentation

Answer 38

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

Question 39

Trypanosoma brucei subspecies

Answer 39

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

Question 40

African sleeping sickness Tx

Answer 40

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

Question 41

What disease is caused by Trypanosoma cruzi?

Answer 41

Chagas Disease

Question 42

Chagas transmission

Answer 42

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)

Question 43

Chagas presentation

Answer 43

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)

Question 44

Chagas Tx

Answer 44

Nifurtimox - not effective for symptoms caused by chronic infection Side effects = skin discoloration, brain toxicity, GI discomfort