Lecture 4 - Protazoan Infections Flashcards
A 28yo female present with fever of 39C and confusion. She returned 16 days ago from a 2 week trip to Kenya. Which of the following should be ordered immediately?
blood smear
looking for malaria parasite in the RBC
What are the most important intestinal protozoa?
giardia intestinalis (chronic diarrhea) entamoeba histolytica (dysentery, liver abscess) cryptoporidium parvum (diarrhea in AIDS)
What are the most important tissue protozoa?
Trypanosomiasis -African: T.b. rhodesiense, T.b. gambiense -South American: T. cruzi Leishmaniasis (visceral vs cutaneous) Toxoplasmosis
What are the the most common blood protozoa?
Plasmoidum (malaria)
Babesia (transmitted by ticks)
What parasite most commonly causes malaria?
Plasmodium falciparum (the most common one to cause sxs d/t cytoadherence)
How is malaria transmitted?
Mosquito genus anapheles
females only
incubation is 1 week
Which two plasmodia can lay dormant in the liver for months to years?
P. ovale and P. vivax
Cytoadherence
seen in plasmoidum falciparum malaria parasite that causes the RBC to be sticky
this gums up the vasculature (ischemia –cerebral malaria)
What is the most common sx seen with malaria?
fever
episodic with very hight spikes (very high, like over 40)
the spikes in temp are d/t rupture of the RBCs
this leads to splenomegaly
What are common things you see on labs for pts with malaria?
anemia
thrombocytopenia (only 50% of pts with malaria have low platelets)
Plasmoidum falciparum results in what clinical manifestation?
cerebral malaria
severe anemia
What is the peak age for malaria infections?
young children (<5)
you have to have constant exposure to maintain immunity
Duffy antigen
is an antigen needed on the host RBC in order for P vivax parasite to enter the RBCs
evolution - no one in west Africa has duffy antigen so they do not get vivax
Sickle cell trait is protective against…
P. falciparum
Is malaria transmitted in the US?
No
We have about 1500 cases a year but they are from immigrants or travelers
How do you dx malaria?
Microscopy — thin and thick blood smears
RDTs (rapid diagnostic tests) using a drop of blood
Serology has NO place in dx of acute infection - since antibodies can be present for ~ 10 years after an infection
When using RDTs for malaria, where is it best to take blood from the pt?
Fingertips (using a lancet similar to glucose tests) because this is where the infected RBCs get stuck d/t cytoadherence
Which malaria parasite can result in coma due to ischemia induced cytoadherent infected erythrocytes obstructing circulation in the cerebral vasculature?
Plasmodium flaciparum
What is the management for malaria?
This is why it is so important to know which species is infecting the pt —done by the lab via blood smear
P.ovale/vivax —must treat liver hypnozoites to prevent relapse
There is now chloroquine drug resistance with p. Falciparum
Other: ACTs - artemesinin-based combination therapy
Can always call the CDC hotline for help
Typically these pts are admitted to the hospital and given IV meds
- ICU
- IV fluids +/- blood transfusion
IV quinidine IV artesunate (From CDC)
How do you treat P. Vivax/ovale?
Must treat the liver hypnozoite stage with PRIMAQUINE x 14 days and then given chloroquine
MUST screen for G6PD deficiency first
Contraindicated in pregnancy —-the only option you have is to wait until the pt delivers and then treat the malaria
What prophylaxis is used for malaria prevention in travelers?
Reduce exposure:
DEET
Insecticide treated bednets
Cover skin
Chemoprophylaxis:
“Yellow book” from CDC to help guide drug based on location of travel
A 24 yo male with functional asplenia due to sickle cell disease goes to Cape Cod and develops a fever. The lab calls you to say there are funny looking things in his erythrocytes. The infection was likely transmitted by a …?
Tick
Babesiosis
Entraerythrocytic parasite transmitted in the US
Which species of babesiosis infects humans most commonly in the US?
B. Microti
How does babesiois microti infect humans?
Tick Ixodes scapularis (this is the same kind of tick that can transmit lyme disease)
The tick must be attached for >24 hours in order to transmit babesiosis microti
Where is babesiosis most commonly transmitted?
New england, wisconsin and minnesota
What is the clinical presentation of babesiosis?
> 25% are asymptomatic (especially in children)
Flu like illness: fever/chills, fatigue, HA (lasts weeks to months)
Complications:
ARDS, massive hemolysis, congestive heart failure, renal failure, death
-elderly, HIV+, and asplenic at higher risk
*absence of spleen means no way of controlling the growth of the parasite
How is babesiosis dx?
Microscopic exam of blood (giemsa stain)
PCR is most commonly used now d/t being more sensitive
Maltese cross
Classic finding (not always seen but when it is it is patognmonic for) babesia on blood smear
Which parasite can establish latency in the liver?
Plasmoidum vivax
Who is at greatest risk of malaria infections?
Children
Pregnancy
Beaver fever
Giardia intestinalis
Pear shaped flagellated protozoan
How do pts with giardia intestinalis present?
> 50% are asymptomatic (esp. in children)
Acute:
- 1 to 4 week incubation
- loose, foul-smelling, pale stool
- steatorrhea: fat malabsorption
- cramping, bloating, nausea
- anorexia, malaise, weight loss
- NO blood in stool
Chronic:
- steatorrhea
- growth impairment
Even though it is called beaver fever you actually dont get a fever
How do you dx giardia intestinalis?
PCR (mutiplex - GI FilmArray/BioFIre
What is the treatment for giardia intestinalis?
Oral meds:
- Metronidazole
- tinidazole (single dose)
- nitazoxanide
Amoebiasis
From a burden of disease point of view, this is one of the most important parasites to know
Entamoeba histolytica
Entamoeba dispar (non-pathogenic species)
-cannot differentiate eachother microscopically
Where is amoebiasis most common?
Tropical areas with crowded living: Africa Latin america Southeast asia India
US (immigrants —highest incidence in hispanic males 20-40 yo)
How is entameobea histolytica transmitted?
Fecal-oral transmission as cysts
Where in the body does entamoeba histolytic centralize to?
Colon and liver
Trphozolites invade the tissues of the colon (unlike giardia which just stays in the gut) and this can in turn get to the liver via portal flow and lead to liver abscess
What are the clinical syndromes of ameobiasis?
Asymptomatic colonization
Ameobic dysentery (bloody diarrhea with fever)
Amoebic colitis
Liver abscess
What is the onset of amoebic colitis?
Gradual (weeks)
What is the clinical manifestation of ameobic colitis?
Diarrhea Dysentery Abdominal pain Weight loss (if it goes on long enough) Fever Heme-positive stool (GI bleeding)
What is the clinical presentation for amoebic liver abscess?
This can be present without hx of intestinal sxs —dont let that fool you
Sxs >4 weeks Immigrant/traveler from endemic area Fever Abdominal pain Hepatomegaly Jaundice Diarrhea Weight loss Cough (diaphragm irritation)
“Anchovy paste”
The aspirate from the ameobic liver abscess
How do you dx amoebiasis?
Stool PCR
Stool microscopy
Stool antigen detection
Serology (more sensitive for liver abscess than colitis)
What is the treatment for amoebiasis?
Always treat active disease with metronidazole (kills trophoziotes) and give second drug to kill the cysts (luminal agent)
Asymptomatic colonization:
Treat with luminal agent
Cryptosporidium parvum
Seasonal peaks in late summer and early fall
Person to person:
-outbreaks in day care centers
Zoonotic:
-farmers and animal handlers
Waterborne:
- swimming pools
- public drinking water
What is the clinical picture for someone infected with crypotoporidiosis?
Watery diarrhea
Immunocompetent pts recover after 1-2 weeks
HIV (CD4<200): chronic diarrhea
How is cryptosporidium parvum dx and treated?
Microscopy with modified acid fast stain
PCR
Treatment: Reduce immunosuppresion (antivirals to get there CD4 count up)
A 19 yo male presents with a 1 month hx of diarrhea and a 15 lb weight loss. He has mild, episodic and diffuse abdominal pain; no fevers or chills. On exam he has mild diffuse abdominal tenderness and is afebrile. He went camping 2 months ago but has not left north america. What is the most likely etiologic agent?
Giardia intestinalis
Not e. Histolytic d/t no outside country travel
Not cryptosporidum d/t not immunosupressed
A pt with HIV and a CD4 count of 75 presents with weight loss and 3 months hx of watery diarrhea. A modified acid fast stain of a fecal sample is positive. What is the likely dx?
Cryptosporidium parvum
Sleeping sickness
Human Afriocan Trypanosmiasis (HAT)
Two morphologically identical subspecies of trypanosmoes:
Gambian HAT: trypanosoma brucei gambiense
Rhodesian HAT: trypansosoma b. Rhodesiense
Transmitted by tsetse flies
These flies are attracted to blue and their bites hurt
Tsetse flies
Transmit human african trypanosmoiasis (HAT)
What are the clinical manifestations of human african trypanosmiasis?
Early: asymptomatic: tryps in blood and lymph nodes
Late: CNS involvement and tryps in CNS —BAD - leads to coma and death “sleeping sickness”
Where are the two african trypanosmes commonly seen?
Tryposoma brucei gambiense (west african)
Trypanosma brucei rhodesiense (east african)
These are NOT intracellular
They’re swimming amongst the RBCs
Primary chancre is seen with what?
Trypanosma brucei gambiense and rhodesience
Develops at bite wound
What are the main differences between gambian and rhodesian HAT?
Time of incubation
Gambian is months to years
Rhodesian is weeks
Winterbottom’s sign
Posterior cervical adenopathy seen with gambian HAT
Not many things cause posterior cervical lymphadenopathy
What are the clinical manifestations of HAT/
Gambian: WInterbottom’s sign: posterior cervical adenopathy Asymptomatic for months or years Intermittent fever: due to antigenic variation CNS involvement: Diurnal somnolence, nocturnal insomnia Constant HAs Behavioral changes DEATh
Rhodesian:
Develops over weeks
How do you dx HAT?
Microscopy with giemsa staining
- lymph node aspirate
- blood
- late stage disease: CSF
Chagas Disease
tripanisoms transmitted by kissing bug
How do people get Chagas Disease?
the parasite is in the feces of the kissing bug
when the kissing bug is feeding on your blood it poops
when you scratch the bug bite you get the feces into the bite
Which organs are affected by the parasite transmitted from the kissing bug?
parasite: trypanosma cruzi
affects cardiac and GI
What is the clinical manifestation of Chagas disease?
t.cruzi parasite
acute chagas disease:
- Chagoma: indurated lesion at site of parasite entry
- Romana’s sign: when conjunctiva is port of entry
- fever, facial edema
- severe myocarditis with ECG changes
Chronic chagas disease:
- dilated cardiomyopathy
- GI: megacolon and megaesophagus
this infection lasts YEARS
Chagomas sign
seen with chagas disease (t. cruzi)
indurated lesion at site of parasite entry
Romanas Sign
seen with chagas disease when conjunctiva is port of entry of feces from t. cruzi
How is chagas disease dx?
acute:
parasite seen microscopically in blood or other specimen (CSF, bone marrow, lymph node biopsy)
PCR
Chronic:
T. cruzi specific IgG (serology)
PCR
What is the treatment for chagas disease?
antiparasitic drugs not very effective
pacemaker (cardiomyopathy)
cardiac transplantation (reactivation of acute disease may occur so follow these pts with PCR)
Leishmaniasis
Visceral Leishmaniasis (VL) -Kala-azar
Cutaneous Leishmaniasis (CL)
Mucocutaneous Leishmaniasis
Sandfly
vector of the leishmania parasite
Kala-azar
visceral leishmaniasis
seen in NE India and South Sudan
opportunistic infection in AIDS infections
Leishmania parasite is intracellular or extracellular?
intracellular
it preferentially likes phagocyte cells –bone marrow, liver, and spleen
What are the clinical features seen with Kala-azar?
visceral leishmaniasis
majority of infections self-resolving
full blown Kala-azar:
-fever
-weight loss
-hepatosplenomegaly
-pancytopenia
-hypergammaglobulinemia
-hyperpigmentation ("black fever")
children <5 years old are most susceptible age group
How is Kala-azar dx?
PCR of blood or biopsy material
Cutaneous Leishmaniasis
chronic ulcerating lesion that heals after weeks to months but leaves scar
How is CL dx?
cutaneous leishmaniasis
biopsy and PCR
the ulcer develops at site where parasite are inoculated
Mucocutaneous Leishmaniasis
Leishmaniasis braziliensis (central/south america)
destructive mucosal lesions
A 56 yo immigrant from Bolivia presents with worsening dyspnea x 6 months, fatigue and exercise intolerance. Cardiac echo shows a dilated heart with EF of 10%. What other organ system is likely to be affected by the causative infection?
GI system
chagas - kissing bug
