Blood and Tissue Parasites

Question 1

cause of malaria

Answer 1

single celled protozoan that cauess malaria derives from the genus plasmodium. human malaria is caused by one of four distinct species of protozoan: P. falciparum, vivax, ovale, and malaria. Falciparum is most lethal, vivax is most common. transmitted to human through bite of infected female mosquito of genus anopheles

Question 2

distribution of plasmodium species

Answer 2

P. vivax: all malarious areas except sub saharan africa
P. malariae: all malarious areas, but spotty
P. ovale: tropical areas of western africa, occasionally western pacific and southeast asia
P. falciparum: sub-saharan africa, but also southeast asia and south america

Question 3

duffy antigen

Answer 3

absence of this in red blood cells prevents P. vivax malaria. Duffy antigen is the erythrocyte receptor for P. vivax merozoite invasion.

Question 4

hereditary elliptocytosis, glyophorin C deficiency, and sickle cell disease heterozygous, certain thalassemias or G6PD deficiency

Answer 4

less susceptible to infection

Question 5

hemoglobin C

Answer 5

one of the most common structural hemoglobin variants in human populations

Question 6

thalassemias

Answer 6

arise from deletion of one or more of the four genes encoding the alpha globin chain or mutations or deletions in one of the two genes encoding the beta globin chain of hemoglobin. mutations associated with thalassemias are protective against malaria.

Question 7

pathogenicity of plasmodium spp

Answer 7

complex and not fully understood. consists of hemolytic anemia and impaired microcirculation. anemia is due to rupture of parasitized erythrocytes, removal or parasitized erythrocytes by the spleen, capillary sequestration, and bone marrow dyserythropoiesis.

Question 8

malaria symptoms

Answer 8

time from infection to symptoms varies, depends on species usually from 9-40 days. can be 7 days to 10 months though. early stages are similar to other infections: fever, chills, headache, sweats, fatigue, nausea, vomiting

Question 9

malarial paroxysm

Answer 9

usually 4-8 hours and begins with sudden onset of chills despite having elevated body temp. immediately is the hot stage, where they feel intense heat and headache. fatigue, dizziness, anorexia, myalgia, and nausea usually too. next they sweat and develop a fever. once they awake, they usually feel fine and dont have symptoms until the next paroxysm. happens in cyclic pattern due to life cycle of the parasites

Question 10

malaria recrudescence

Answer 10

used to describe the situation in which parasitemia falls below detectable levels and then later increased to detectable parasitemia.

Question 11

malaria relapse

Answer 11

where sporozoites invade hepatocytes, in which they develop into schizonts and may not be observed in the circulation and the individual may be asymptomatic

Question 12

plasmodium falciparum

Answer 12

much more acute and severe than malaria caused by other plasmodium species. almost all deaths directly attributable to malaria are caused by severe manifestations of falciparum, including cerebral malaria, severe anemia, respiratory failure, renal failure, and severe malaria of pregnancy. has ability to sequester in the deep venous microvasculature

Question 13

falciparum pathophys

Answer 13

hypoglycemia, anemia, pulmonary edema, repspiratory distress (sequestration of infected erythrocytes in the lungs initiating regional production of inflammatory cytokines that increase pulmonary permeability leading to edema) 
metabolic acidosis (lactic acid)

Question 14

PfEMP-1

Answer 14

P. falciparum erythrocyte membrane protein-1. many variants with unique antigenic and cytoadherent properties. switches in expression between individual members of the var gene family occur at rate of 2-18% per cell per generation. CD36 is major receptor

Question 15

cerebral malaria

Answer 15

sequestration of parasites in the cerebral microvasculature often accompanied by ring hemorrhages, perivascular leukocyte infiltrates, and immunohistochemical evidence for endothelial cell activation. sequestration is thought to stimulate local production of inflamm cytokines and mediators

Question 16

malaria of pregnancy

Answer 16

placental malaria results in maternal morbidity and mortality, intrauterine growth retardation, premature delivery, low birth weight, and increased newborn mortality. accumulation of mature parasites in the placenta appears to involve their interaction with syncytiotrophoblastic chondoitin sulfate A, hyaluronic acid, and immunoglobulins, as opposed to the CD36 receptor used elsewhere

Question 17

US Rapid Diagnostic Test for malaria

Answer 17

Binax NOW only approved brand. high quality malaria microscopy is not always immediately available. detects 2 antigens: P. falciparum and the other is found in all 4 human species of malaria. microscopy is needed to quantify the proportion of red blood cells that are infected, an important prognostic indicator

Question 18

anti-malarial treatments

Answer 18

all the drugs we learned about last unit. regimens are complicated and vary

Question 19

trypanosome infections

Answer 19

american trypanosomiasis is most frequent in the US, mainly southern to middle texas, but recently in SoCal. acute (die within a few weeks) and chronic (symptoms may not present for 5-15 years)

Question 20

romana’s sign

Answer 20

inflamed eye due to trypanosomiasis

Question 21

leishmaniasis

Answer 21

infective stage transmitted by sand fly regurgitation. multiplication occurs in histiocytes (skin/mucous membrane liver). cutaneous (l. tropica complex is new world, l. mexica complex is old world). mucocutaneous (l. braziliensis complex). visceral (l. donovani complex and kala-azar)

Question 22

leishmaniasis clinical manifestations

Answer 22

cutaneous leish has chronic skin ulcers. lesions at site other than bite site. mucocutaneous leish has metastatic spread of primary lesions to the mouth, nose, pharynx. visceral leish has fever, weight loss, splenomegaly, hepatomegaly, and anorexia.

Question 23

toxoplasmosis

Answer 23

considered a leading cause of death attributed to foodborne illness in US. capable of infecting all species of animals and birds. hosts are usually cats. shed oocysts in their poop.

Question 24

toxoplasma gondii transmission

Answer 24

undercooked meat or cat poop with infective cysts, transplantation, or transplacentally

Question 25

healthy people who get toxoplasmosis

Answer 25

usually have mild flu-like symptoms that last for several weeks then goes away. parasite remains in body in inactive state. can become reactivated if person is ever immunosuppressed.

Question 26

congenital toxoplasmosis

Answer 26

presentation: chorioretinitis, hydrocephalus, and intracranial calcifications. results from acute primary infection acquired by mother during pregnancy. higher transmission rate in third trimester

Question 27

toxoplasma in immunosuppressed

Answer 27

persons with compromised immune systems can have severe symptoms. fever, confusion, headaches, seizures nausea. CNS infection leads to brain lesions

Question 28

toxoplasma ocular infection

Answer 28

eye disease from toxoplasma infection. leads to acute inflamm lesion of retina, resolves leaving retinochoroidal scarring. symptoms are eye pain, sensitivity to light, tearing, blurred vision. infection can reactivate months or years later.