PRACTICE QUESTIONS    EXAM 2

(answers given below)

Complete the following table.  Cells with  XXX do not require an answer.  Scientific names must be written correctly (Genus names capitalized and underlined; species name lower case and underlined)

Short Answer:  Read the paragraph below and then assess the statements below it.  For each statement, indicate if it is True or False and then justify your answer.  You must address each factor mentioned in the statements.  If you think an answer is false, then state what would be necessary to make it true.  It is possible for all statements to be true or false.           

1.  A patient is brought to an emergency room because he is suffering from tuberculosis-like symptoms, severe ascites, and neurological damage  Questioning reveals that he recently immigrated to the U.S. from a rural areas in the Orient.  In his home country, he worked ain rice patties and frequently ate raw fish and crustaceans and  uncooked water chestnuts.  Biopsies reveal psuedotubercules in the lungs, liver and brain.  Which of the following could you correctly diagnose?

            a.  The man ate fish infected with the metacercaria of Myxobolus cerebralis and crustaceans infected with the metacercaria of Paragonium westermani.

            b.  The lung damage is due to either migrating mesocercaria of Alaria americana, the eggs of which can lodge in the lungs, or metacercaria of Prosthogonimus macrochis, which encyst in the lungs, and both parasites can cause tuberculosis-like symptoms.

            c.  The rice patties the man worked in contained the snail, Oncomelania,which released furcocercous cercaria, and thiarid snails, which released microcercous cercaria.

            d.  All of the described symptoms are due to delayed-type hypersensitivity.

2.  After graduating from UNC Charlotte, you go to medical school and then spend time working in a clinic in rural Africa.  A 40 year old patient is brought in who is suffering from near-continuous fever and chills, severe anemia, an increasingly severe headache, and he quickly goes into a coma.  Based on these symptoms you can correctly conclude:

a.  the patient is infected with Plasmodium malariae and the disease involves only old red blood cells, which lodge in the capillaries of the brain and form pseudotubercles.

b.  in the life cycle of the parasite, the oocyst in the gut wall of the Boophilus vector gives rise to triactinomyxons that migrate to the salivary glands.

c.  the patient was homozygous recessive for sickle cell anemia and homozygous for the F_y allele of the of the Duffy blood groups.

d.  if the patient lives, he will develop complete immunity to the parasite (if false, explain why immunity will not develop).

KEY

Complete the following table.  Cells with  XXX do not require an answer.  Scientific names must be written correctly (Genus names capitalized and underlined; species name lower case and underlined)

Short Answer:  Read the paragraph below and then assess the statements below it.  For each statement, indicate if it is True or False and then justify your answer.  You must address each factor mentioned in the statements.  If you think an answer is false, then state what would be necessary to make it true.  It is possible for all statements to be true or false.           

1.  A patient is brought to an emergency room because he is suffering from tuberculosis-like symptoms, severe ascites, and neurological damage  Questioning reveals that he recently immigrated to the U.S. from a rural area in Asia.  In his home country, he worked in rice patties and frequently ate raw fish and crustaceans and  uncooked water chestnuts.  Biopsies reveal psuedotubercules in the lungs, liver and brain.  Which of the following could you correctly diagnose?

            a.  The man ate fish infected with the metacercaria of Myxobolus cerebralis and crustaceans infected with the metacercaria of Paragonium westermani.

False and True:  although M. cerebralis causes neuroloigcal damage in fishes, it does not infect humans and it does not produce metacercaria (fish become infected by triactinomyxons).  The man may have each crustaceans infected with metacercaria of P. westermani, because the pseudotubercules in the lungs and brain could be eggs of the human lung fluke, which uses crustaceans as a 2nd IH and can cause tuberculosis-like symptoms.

            b.  The lung damage is due to either mesocercaria of Alaria americana that migrate through the lungs or metacercaria of Prosthogonimus macrochis, which encyst in the lungs, and both parasites can cause tuberculosis-like symptoms.

False:  humans can get A. americana through the accidental ingestion of infected tadpoles, and the mesocercaria migrate to the lungs, up the trachea and are then swallowed, which can cause lung damage.  However, no information is given that the man ate tadpoles.  P. macrochis occurs in the oviduct of chickens and its metacercaria encyst in the anal lung of dragonfly nymphs (not human lungs); this is never a human parasite.

            c.  The rice patties the man worked in contained the snail, Oncomelania,which released furcocercous cercaria, and thiarid snails, which released microcercous cercaria.

True:  Oncomelania is the snail IH for Schistosoma japonicum, and releases furcocercous cercaria when penetrate the skin of humans.  The adult blood fluke  inhabits the venules of small intestines of humans and its eggs form psuedotubercles in the liver and brain and cause ascites and neurological damage.  Thiarid snails are the first IH for P. westermani, and release microcercous cercaria which then encyst in a crustacean 2nd IH.  P. westermani adults inhabit the human lung and both the eggs that get trapped in the lung (and form pseudotubercles) and the adults can cause tuberculosis-like conditions.  Also, can get ectopic adults that migrate to brain and spinal cord where both eggs and adults can cause severe neurological problems.

            d.  All of the described symptoms can be due to delayed-type hypersensitivity.

True:  eggs of both S. japonicum and P. westermani become lodged in human tissues (liver, lungs, brain).  The continued presence of antigens then sitmulates DTH resulting in the formation of fibrous tissue, granulomas and eventually psuedotubercules.  As these accumulate, the tissues can begin to thicken and/or lose function.  In the liver, this causes ascities, in the lungs tuberculosis-like symptoms, and neurological damage.

2.  After graduating from UNC Charlotte, you go to medical school and then spend time working in a clinic in rural Africa.  A 40 year old patient is brought in who is suffering from near-continuous fever and chills, severe anemia, an increasingly severe headache, and he quickly goes into a coma.  Based on these symptoms you can correctly conclude:

a.  the patient is infected with Plasmodium malariae and the disease involves only old red blood cells, which lodge in the capillaries of the brain and form pseudotubercles.

False:  Although P. malariae does infect only old red blood cells, it does not cause continuous fever and chills or cerebral malaria.  Patient has Plasmodium falciparum which infects red blood cells of all ages.  In RBC, trophozoite causes knobs to form on cell surface and these knobs bind with glycoproteins in capillaries in the brain, lodge, and cause DTH resulting in cerebral malaria.  The lodged infected RBCs do not form pseudotubercles (caused by lodged eggs of flukes).

b.  in the life cycle of the parasite, the oocyst in the gut wall of the Boophilus vector gives rise to triactinomyxons that migrate to the salivary glands.

False:  oocyst of P. falciparum form in stomach wall of mosquito, gives rise to sporozoites that migrate to salivary glands.  Boophilus is vector for Babesia bigemina, which produces vermicules that migrate to salivary gland of the tick.  Triactinomyxons are the spore produced in the earthworm host of Myxobolus cerebralis, which causes whirling disease in salmonids; these do not migrate to salivary glands but pass out with feces of earthworm or fish eats infected earthworm and triactinomyxons discharge polar filaments

c.  the patient was homozygous recessive for sickle cell anemia and homozygous for the F_y allele of the of the Duffy blood groups.

False:  if the patient has been homozygous for sickle cell, he would have died before age 40.  Also, he would have had partial immunity to P. falciparum and would not have developed such severe symptoms.  Patient also was not homozygous Fy for Duffy, because these humans lack the receptors on RBCs for merozoite penetration and have complete immunity to P. vivax and partial immunity to P. falciparum, and thus his symptoms would not have been as severe.

d.  if the patient lives, he will develop complete immunity to the parasite (if false, explain why immunity will not develop).

False:  at best, can develop premunition to malaria and then only after repeated exposures.  Patient will not develop immunity because of shifting surface antigens of Plasmodium (coded for by the var gene complex), which vary among geographic races, strains within a race and lifecycle stages within a strain.  Plasmodium also shed its antigens (which can bind with host RBC and cause lysis).  Hemozoin is taken up by marcophages and impairs phagocytic  ability.  Plasmodium causes polyclonal B cell activation and may also suppress IL-2 production