Protozoa Flashcards
List the protozoa (11)
Babesia Cryptosporidium Entamoeba histolytica Girardia lamblia Leishmania donovani Naegleria fowleri Plasmodium (Vivax, Ovale, Falciperum) Toxoplasma gondii Trichomonas vaginalis Typanosoma brucei (+ 2 subspecies) Trypanosoma cruzi
Babesia presentation
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
Babesia transmission
Northeastern USA
Ixodes tick - same as borrelia (Lyme) - dual infection can occur
Cryptosporidium transmission
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
Cryptosporidium presentation
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.
Entamoeba transmission
Ingestion of cysts in food/water - cysts can survive outside host in water, soil, foods for months
Entamoeba presentation
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
Entameoba Tx
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
Giardia transmission
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)
Giardia presentation
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
Giardia Tx
Metronidazole
Leishmania transmission
Sandfly - intermediate host, humans are definitive host. Transmission is through bite from sandfly
Leishmania presentation
Causes visceral Leischmaniasis
1) Hepatosplenomegaly
2) Spiking fevers - pyrexias - continuous or remittent - a distinguishing feature*
3) Skin pigmentation - heavy skin discoloration - “black fever”
Leishmania diagnosis
Macrophages with amastigotes - direct visualization of amastigotes inside of macrophages
Leishmania Tx
Amphotericin B - India, South America, Mediterranean causes up to 95%
Oral Miltefosine - can cause birth defects
Naegleria transmission
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
Naegleria presentation
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
Naegleria Dx
Amoebas in CSF - on lumbar puncture
Flagellation test confirms Naegleria ameboid presence
Naegleria Tx
Amphotericin B
What disease is caused by plasmodium?
Malaria
Plasmodium (general) presentation
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
Plasmodium (general) transmission
Always has 2 hosts
Vector is usually mosquito (Anopheles mosquito)
All plasmodium species causing malaria in humans transmitted through this mosquito
General plasmodium Tx
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.
P. malariae
Milder form of malaria
Fever every 3 days
P. Vivax and P. Ovale
Malaria
Cyclic fever every 2 days
Also associated with persistent liver stages that allow relapse up to 5 years after elimination of erythrocytic stage
Duffy antigen binding site
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)
P. Vivax and P. Ovale Tx
Primaquine - treats dormant form in liver
P. Falciparum
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.
Toxoplasma transmission
cysts in meat or cat feces - undercooked meat or fecal-oral
Also, vertical (TORCH)
Toxoplasma presentation
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
What is the #1 cause of ring-enhancing brain lesions in HIV+ patients?
Toxoplasmosis
Toxoplasmosis Tx
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
Trichomonas presentation
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
What does Trichomonas look like?
Demonstrates corkscrew motility on wet mount
Trichomonas Tx
Metronidazole
What disease is caused by Trypanosoma brucei?
African sleeping sickness
African Sleeping Sickness transmission
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
African Sleeping Sickness presentation
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
Trypanosoma brucei subspecies
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
African sleeping sickness Tx
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
What disease is caused by Trypanosoma cruzi?
Chagas Disease
Chagas transmission
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)
Chagas presentation
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)
Chagas Tx
Nifurtimox - not effective for symptoms caused by chronic infection
Side effects = skin discoloration, brain toxicity, GI discomfort
