Parasite Infections of the Blood

Question 1

what is the most common species of malarial infection? which is the most deadly?

Answer 1

p falciparum (both questions)

Question 2

what genetic predispositions are protective against malaria?

Answer 2

absence of duffy antigen (vivax), hereditary elliptocytosis, heterozygotes for sickle cell disease, thalassaemia and G6PD deficiency

Question 3

what hemoglobin variants are protective against malaria?

Answer 3

thalassemia, hemoglobin S and HbC

Question 4

why are people without a duffy antigen less likely to get malarial infections?

Answer 4

because it is the erythrocyte receptor for p vivax

Question 5

what is the pathogenicity of malarial infections?

Answer 5

produces anemia by hemolysis and impaired microcirculation

Question 6

what is the range of malarial incubation?

Answer 6

generally around 10-40 days but may take as long as 8-10 months with vivax and ovale

Question 7

what is the malarial paroxysm? how long does it last?

Answer 7

begins with an intense feeling of cold followed by the feeling of intense heat. the fever will then break and the patient will be sweaty and tired takes 4-8 hrs

Question 8

what are the causes of the malaria paroxysm stages?

Answer 8

cold stage- lysis of RBC by schizonts
hot stage- cytokine response to parasite in plasma
sweating stage- parasites infect new RBC and are cleared from circulation

Question 9

when does the malaria cyclic pattern not occur?

Answer 9

it may take time for the schizonts to sync their replication cycle. (beginning of infection).
p falciparum does not exhibit this cycle

Question 10

what is malaria recrudescence?

Answer 10

parasitemia is undetectable for a period of time and later recurs

Question 11

why do relapses of malaria occur?

Answer 11

the sporozoites invade hepatocytes and remain latent there until after a period of time when the hepatocyte ruptures

Question 12

what are the severe manifestations of p falciparum?

Answer 12

cerebral malaria, severe anemia, respiratory failure, renal failure and severe malaria of pregnancy

Question 13

what is an abnormal feature of the pathogenesis of p falciparum?

Answer 13

ability to sequester in the deep venous microvasculature

Question 14

what are the metabolic manifestations of p falciparum infection?

Answer 14

lactic acidosis from impaired O2 delivery and hypoglycemia

Question 15

what causes pulmonary edema and respiratory distress in p falciparum infection?

Answer 15

sequestration of infected erythrocytes in the lungs initiates production of cytokines that increase capillary permeability

Question 16

what is the significance of PfEMP-1?

Answer 16

a ligand for the receptor CD36 that allows RBC to attach to cells in the vasculature

Question 17

what is the classic finding in cerebral malaria?

Answer 17

sequestration of parasites in cerebral microvasculature accompanied by ring hemorrhages, perivascular leukocytes and endothelial cell damage

Question 18

what is the harm of placental malaria?

Answer 18

maternal morbility and mortality, growth retardation, premature delivery, low birth weight and newborn mortality

Question 19

why do mature parasites accumulate in the placenta?

Answer 19

they interact with syncytiotrophoblastic antigens, hyaluronic acid and immunoglobulins

Question 20

what are the benefits for rapid diagnostic testing for malaria? what does it test for?

Answer 20

microscopy is not always available and it detects antigens of p falciparum and p vivax

Question 21

what has been the result of phase three trials for the mosquirix vaccine for malaria?

Answer 21

effectiveness was 35% but stops working after about 6 months in 50% of patients

Question 22

what clinical features are shared by p vivax and p ovale?

Answer 22

they have low mortality because they do not inhibit sequestration and they favor reticulocytes. they also may recur

Question 23

what cells does p malariae often infect? what is the incubation period and what is the usual presentation?

Answer 23

infects older RBC with an incubation period of 40 days. patients present with proteinuria or nephrotic syndrome

Question 24

why has a new species of malaria just recently been found? what does it usually infect?

Answer 24

because p knowlesii is similar to p malariae and is often misdiagnosed. it is primarily a primate parasite

Question 25

what transmits babesia? what does the presentation resemble?

Answer 25

different types of ticks
in the northeast it resembles p vivax infection. in the rest of the country it presents as a fulminate, febrile hemolytic disease

Question 26

what does the distribution of babesia resemble?

Answer 26

lyme disease and anaplasmosis (there is a lot of coinfections)

Question 27

what is a major reservoir for anaplasmosis?

Answer 27

white footed mouse and squirrels

Question 28

what are the first symptoms of anaplasmosis?

Answer 28

constitutional symptoms, nausea, cough and confusion

Question 29

what are some serious clinical presentations of anaplasmosis?

Answer 29

difficulty breathing, hemorrhage, renal failure or neurological problems

Question 30

what disease does trypanosomiasis cause? what is the causative agent?

Answer 30

chagas’ disease

trypanosoma cruzi causes it in america

Question 31

what are the two vectors for trypanosomiasis?

Answer 31

the tsetse fly in Africa and the reduvid bug in the americas

Question 32

where is chagas’ disease spread and what are the forms of the disease?

Answer 32

in southern california and texas.
acute form- death in weeks
chronic form- symptoms may not present for years

Question 33

how does american trypanosomiasis infect humans?

Answer 33

the reduvid bug excretes the parasite in its feces. when the bug bites a human it leaves the feces behind. the feces cause itching and when the person scratches, it produces breaks in the skin

Question 34

what parasite is a leading cause of foodborne illness death in the US? what is the usual host?

Answer 34

toxoplasmosis

the usual host are cats

Question 35

how is toxoplasmosis transmitted from cats to humans?

Answer 35

oocysts are shed in the cat’s feces (especially in kittens) and they infect people by accidental consumption through food or water contamination

Question 36

what nonfeline modes may transmit toxoplasmosis?

Answer 36

may be transmitted via the consumption of undercooked meat that contain infective cysts or may transmit transplacentally

Question 37

what is the progression of toxoplasma infection in healthy people?

Answer 37

most people are asymptomatic or have mild flu like symptoms. the parasite remains in muscle tissue and may reactivate with immunosupression

Question 38

how is congenital toxoplasmosis acquired? what determines severity?

Answer 38

with an acute primary infection of the mother during pregnancy. severity dictated with the trimester of infection (early has more severe symptoms but is less likely to be transmitted)

Question 39

what is the most common presentation of congenital toxoplasmosis infection? what are more severe manifestations?

Answer 39

most are aymptomatic but may develop learning, visual and hearing disabilities later.
may cause miscarriage, still born or abnormal head size

Question 40

what is the manifestation of toxoplasmosis with immunosuppression?

Answer 40

infection will cause severe symptoms with neuro involvement (lesions in brain)

Question 41

what transmits leishmania?

Answer 41

certain species of blood feeding sand flies

Question 42

what are the clinical manifestations of leishmaniasis?

Answer 42

cutaneous-chronic skin ulcers
mucocutaneous- spread of lesion to mouth, nose and pharynx with mucosal destruction
visceral- fever, weight loss, anorexia and hepatosplenomegaly

Question 43

what are the clinical features of lymphatic filariasis?

Answer 43

lymphatic dysfunction causing lymphedema and elephantitis of the lower extremities. Hydrocele and scrotal elephantitis also may occur.