Lec42 Malaria and Babesia Flashcards
What are helminths?
multicellular worms
What are protozoa?
unicellular parasites
What is main target of plasmodia?
red blood cells
What are symptoms of malaria?
initially symptoms of flu: - fever - shivering - pain in joints - headache - vomiting rapidly progresses: --> anemia, hemoglobinuria [black water fever], organ failure [kidney/liver/brain], death
Where are most of malaria cases?
more than 90% in Africa
What are signs of plasmodium falciparum?
- most pathogenic
- see ring forms on peripheral sphere, may see banana gametocytes
- multiply infected red cells
- rapidly progresses to heavy paraistemia
- infected cells same size as non-infected
- get endorgan damage [esp. cerebral]
How is plasmodium falciparum transmitted?
via anopheles mosquito
What are schizonts?
bag of parasites ready to rupture open
Which two malaria species have a hypnozoite stage? what does that mean?
- hypnozoite stage = a dormant stage where it hangs around in liver
- plasmodium ovale and plasmodium vivax
What additional treatment do you need to give for malaria with hynozoite stage?
need to give primaquine
What is life cycle of plasmodium?
- mosquito injects gametocytes
- mosquito injects sporozoites
- sporozoites go to liver and form tissue schizont = replicating parasite
- schizont ruptures and gives off sporozoites = when it becomes diagnostic
- sporozoites infect RBCs, mature and form more erythrocytic schizonts and rupture to continue cycle
- ## some sporozoites mature into gametocytes and can then be infective
What is major preventitive measure against malaria
- use bed nets
- use repellent especially at night
major time of mosquito activity = night
Where do most malarial agents work?
in blood phase at level of erythrocytic schizont
How much time between mosquito bite and symptoms?
- about 8 days incubation period when it may not be detectable
What is a hypnozoite?
resting stage of malaria wks/months later
What is rapid malaria test?
- strip with test and control bands
- parasite Ag captured by a labeled Ab then the labeled Ab-Ag complex will be captured by bound Ab of test band
- labeled Ab captured by bound Ab of control band
What is the most lethal cause of malaria?
- plasmodium falciparum
What are the four causes of malaria?
- plasmodium falciparum
- plasmodium vivax
- plasmodium ovale
- plasmodium malariae
What drug is plasmodium falciparum resistant to in most parts of the world?
chloroquine
What is cause/effect of cerebral malaria?
- usually due to falciparum infection
- 20% mortality
- cerebral ischemia secondary to sequestration of parasitized RB or cytokines
- get seizure, altered mental status, hypoglycemia/lactic acidosis
- normal CSF but high ICP [intracranial pressure
What cells does falciprum infect vs ovale/vivax?
falciprum can infect RBCs of any age
ovale/vivax primarily infect young reticulocytes
What do you normally see in plasmodium faliparum blood smear?
- only see early trophocytes [rings] and [banana shaped] gametocytes
- common to see multiple infections of single red cell
- infected cells are same size as uninfected
- small trophozoites = 2 chromatin dots in cell
- do not usually see schizonts
- may see parasitized RBC and schizonts in brain capillaries
How do merozoites enter erythrocyte?
via parasitopherous vacuole
What is PfEMP1 protein?
- parasite protein that gets expressed on infected cells
- forms knobs that allow cell to attach capillary endothelium
- undergoes antigenic variation so immunity difficult
What are challenges of malaria vaccine?
spends most of time as intracellular pathogen
What are ring hemorrhages?
accumulation of parasites in brain capillaries leads to ischemia surrounding capillary in ring shape
What is hemozoin?
- malaria pigment that can be seen deposited in infected organs
What are characteristics of plasmodium vivax?
- can relapse months or yrs later via hypnozoites
- duffy blood group antigen needed for attachment to RBC
- only infects reticulocytes [so lower parasitemia]
- synhronous schizogony so get fever every 48 hrs
Can chloroquine treat plasmodium vivax?
- usually but some resistance reported in papua new guinea
What do you see with plasmodium vivax on blood smear?
- infected RBCs are enlarged
- see all stages in peripheral blood [ring form, ameboid trophozoites, schizonts, gametocytes]
- multiple infections in RBC common
What do you see in plasmodium ovale on blood smear
- all stages in peripheral blood [ring form, ameboid trophozoites, schizonts, gametocytes]
- rarely see multiple infections
- infected RBCs are slightly enlarged and oval shape
How do you tell difference between ovale and vivax?
- ovale = oval shaped infected cells
- ovale you never see multiple infections of same cell
What are signs of plasmodium ovale?
- fever every 48 hrs [same as vivax]
- possible relapses
What is primaquine?
- tissue schozontocide –> treats liver phase of malaria
- use to treat p vivax or p ovale
When is primaquine contraindicated?
in G6PD deficiency –> can cause hemolytic anemia
what are evolutionary adaptations related to malaria?
- G6PD deficiency –> more oxygen radicals –> survival advantage, might destroy parasite
- sickle cell –> malaria can’t infect sickle RBCs
- thalassemia –>
- duffy antigen
how long can ovale/vivax persist vs malariae?
ovale/vivax persist for 5 yrs
malariae persist for 20-30 yrs
What are characteristics of plasmodium malariae?
- may persist in blood 20-30 yrs after infection
- no hypnozoite liver stage just delayed onset in humans
- infects only aging RBCs [lower parasitemia]
- 72 hr schizogony so longer duration between fevers than vivax/ovale
What do you see with plasmodium malariae smear?
- all stages in peripheral blood
- multiple infections rare
- infected erythrocytes not enlarged
- can see band form
What is p knowelsii?
- looks identical to p. malariae, originally a primate pathogen recently reported in humans in SE Asia
How is quinine administered? what can it treat?
- good agent against all 4 species
- not available in US as IV –> give quinidine
What is possible side effect of quinidine?
cardiotoxicity
What are breeding sites for malaria vector?
- rice field
- marsh/swamp
- open water storage tank
- urban area construction site with open water storage
What are the antimalarial drugs?
- quinine/quinidine
- chloroquine
- mefloquine
- primaquine
- atovaquone/proguanil
- doxycycline
- sulfadoxine-pyrimethamine
- artemesinin derivatives
what are preventitive malarial meds?
- malarone
- doxycycline
- mefloquine
What do you use to treat severe malaria?
IV quinidine in combo with doxy or clindomycin
What is babesia microti
- intra-erythrocytic parasite very difficult to distinguish from plasmodium
How is babesia microti transmitted? vector? reservoir?
- by ixodes scapularis tick [same as lyme disease]
- reservoir = white footed mice and other small rodents
What do you use to treat babesia microti?
- first choice: atovaquone + azithromycin
- 2nd choice: clindamycin + quinine
Where are most cases of babesia in US?
- nantucket, marthas vineyard, cape cod, block island, eastern long island, shelter island, fire island
What are clinical signs of babesiosis?
can be asymptomatic: incubation for wks to months
mild: viral like disease after 1-6 wks, malaise/fever/fatigue/anemia, less common: ab pain/ nausea/ vomitting/sore throat/depression
severe: in pts who are asplenic or immunosuppressed –> acute resp failure, DIC, CHF, liver/renal failure
how is babesia transmitted?
tick, blood transfusion
