GI Digest Nzym Parasite Dfens Mech MCQ's

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  • 1/24 Questions

    Which one of the following products of lipid digestion would be LEAST LIKELY expected in an analysis of a mixed micelle?

    • Fatty acids
    • Cholesterol
    • Glycerol
    • Lysophospholipids
    • Monoglycerides
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GI Digest Nzym Parasite Dfens Mech MCQ
About This Quiz

This quiz assesses knowledge on enzyme deficiencies and metabolic pathways, focusing on digestion, mitochondrial dysfunctions, and carbohydrate metabolism. It is designed for medical students preparing for exams like USMLE, testing critical understanding of biochemical processes and clinical implications.

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  • 2. 

    The major digestion of carbohydrates takes place in the small intestine with enzymes produced by the enterocytes in the brush border. Which enzyme is responsible for cleavage of a-limit dextrin?

    • Trehalase complex

    • Lactase P-galactosidase complex

    • Lingual amylase

    • Glucoamylase complex

    • Sucrase-isomaltase complex

    Correct Answer
    A. Sucrase-isomaltase complex
    Explanation
    The sucrase-isomaltase complex is responsible for the cleavage of a-limit dextrin. This complex is produced by the enterocytes in the brush border of the small intestine. Sucrase breaks down sucrose into glucose and fructose, while isomaltase breaks down isomaltose and a-limit dextrin into glucose. Therefore, the sucrase-isomaltase complex plays a crucial role in the digestion of carbohydrates in the small intestine.

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  • 3. 
    A 2 y.o. female patient presents with malaise. A blood test indicates elevated lactic acid (hyperlactatemia). Lymphocyte culture indicates poor utilization of oxygen, but oxygen uptake increases after addition of succinate to the cell culture medium. The child's mother reports that her 4 y.o. son also suffers from the same symptoms. A pedigree of the family's "malaise" incidence is shown below. This patient is likely to suffer from which enzyme deficiency? - ProProfs

    A 2 y.o. female patient presents with malaise. A blood test indicates elevated lactic acid (hyperlactatemia). Lymphocyte culture indicates poor utilization of oxygen, but oxygen uptake increases after addition of succinate to the cell culture medium. The child's mother reports that her 4 y.o. son also suffers from the same symptoms. A pedigree of the family's "malaise" incidence is shown below. This patient is likely to suffer from which enzyme deficiency?

    • Pyruvate Dehydrogenase

    • Pyruvate Carboxylase

    • Cytochrome P450

    • Cytochrome Oxidase

    • NADH Oxidoreductase

    Correct Answer
    A. NADH Oxidoreductase
    Explanation
    NADH dehydrogenase (also referred to as NADH:ubiquinone reductase or Complex I) is an enzyme located in the inner mitochondrial membrane that catalyzes the transfer of electrons from NADH to coenzyme Q (CoQ). It is the "entry enzyme" of oxidative phosphorylation in the mitochondria
    NADH Dehydrogenase is the first enzyme (Complex I) of the mitochondrial electron transport chain. There are three energy-transducing enzymes in the electron transport chain - NADH dehydrogenase (Complex I), Coenzyme Q – cytochrome c reductase (Complex III), and cytochrome c oxidase (Complex IV). NADH dehydrogenase is the largest and most complicated enzyme of the electron transport chain.
    The reaction of NADH dehydrogenase is:
    NADH + (H+) + CoQ + 4(H+)in → NAD+ + CoQH2 + 4(H+)out
    In this process, the complex translocates four protons across the inner membrane per molecule of oxidized NADH, helping to build the electrochemical potential used to produce ATP.
    The reaction can be reversed - referred to as aerobic succinate-supported NAD+ reduction - in the presence of a high membrane potential, but the exact catalytic mechanism remains unknown
    (MOA) All redox reactions take place in the extramembranous portion of NADH dehydrogenase. NADH initially binds to NADH dehydrogenase, and transfers two electrons to the flavin mononucleotide (FMN) prosthetic group of complex I, creating FMNH2. The electron acceptor - the isoalloxazine ring - of FMN is identical to that of FAD. The electrons are then transferred through the second prosthetic group of NADH dehydrogenase via a series of iron-sulfur (Fe-S) clusters, and finally to coenzyme Q (ubiquinone). This electron flow changes the redox state of the protein, inducing conformational changes of the protein which alters the pK values of ionizable side chain, and causes four hydrogen ions to be pumped out of the mitochondrial matrix. Ubiquinone (CoQ) accepts two electrons to be reduced to ubiquionol (CoQH2).
    The best-known inhibitor of Complex I is rotenone (commonly used as an organic pesticide). Rotenone and rotenoids are isoflavonoids occurring in several genera of tropical plants such as Antonia (Loganiaceae), Derris and Lonchocarpus (Faboideae, Fabaceae). There have been reports of Indians using rotenone-containing plants to fish - due to its ichthyotoxic effect - as early as the 17th century. Rotenone binds to the ubiquinone binding site of Complex I as well as piericidin A, another potent inhibitor with a close structural homologue to ubiquinone.
    Mutations in the subunits of Complex I can cause mitochondrial diseases, including Leigh syndrome. Point mutations in various Complex I subunits derived from mitochondrial DNA (mtDNA) can also result in Leber's Hereditary Optic Neuropathy. There is some evidence that Complex I defects may play a role in the etiology of Parkinson's disease, perhaps because of reactive oxygen species (Complex I can, like Complex III, leak electrons to oxygen, forming highly toxic superoxide).

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  • 4. 

    Clinical symptoms associated with metabolic dysfunctions in mitochondria are associated with?

    • Insufficient renal clearance

    • Heart murmurs and clammy skin

    • Fatigue and metabolic acidosis

    • Loss of hair and nausea

    • Dry skin and dehydration

    Correct Answer
    A. Fatigue and metabolic acidosis
    Explanation
    Metabolic dysfunctions in mitochondria can lead to a decrease in energy production, resulting in fatigue. Metabolic acidosis occurs when there is an accumulation of acid in the body due to impaired metabolism. This can cause symptoms such as fatigue, weakness, and confusion. Therefore, the clinical symptoms associated with metabolic dysfunctions in mitochondria are fatigue and metabolic acidosis.

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  • 5. 

    A newborn presents with severe acidosis, vomiting, hypotonia and neurologic deficits. Serum analysis reveals elevated levels of lactate and alanine. These observations suggest a deficiency in which of the following enzymes ?

    • Alanine aminotransferase

    • Glutamate dehydrogenase

    • Lactate dehydrogenase

    • Pyruvate dehydrogenase

    • Pyruvate carboxylase

    Correct Answer
    A. Pyruvate dehydrogenase
    Explanation
    The given symptoms of severe acidosis, vomiting, hypotonia, and neurologic deficits, along with elevated levels of lactate and alanine in the serum, suggest a deficiency in Pyruvate dehydrogenase. Pyruvate dehydrogenase is an enzyme involved in the conversion of pyruvate to acetyl-CoA, which is an important step in the production of energy in the form of ATP. A deficiency in this enzyme leads to the accumulation of pyruvate and lactate, causing the symptoms observed in the newborn.

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  • 6. 

    A group of individuals in normal health each fasted overnight and then consumed a carbohydrate beverage the next morning. All individuals were normoglycemic (mean of 85\ mg/dL) before ingestion and all demonstrated a rise and fall in blood glucose over the next several hours. Other things being equal, ingestion of which of the following carbohydrates would result in the slowest absorption across the intestinal epithelia?

    • 75 grams of glucose

    • 75 grams of galactose

    • 75 grams of fructose

    • 150 grams of lactose

    • 150 grams of maltose

    Correct Answer
    A. 75 grams of fructose
    Explanation
    (short answer) Fructose is by facilitated difusion, Gluc/gala use Na co-transport

    Mechanisms of transport:
    Monosaccharides must next be transported across the luminal membrane of the enterocyte. The sodium/glucose transporter 1 (SGLT1) is a symporter that takes up glucose (and galactose) against its concentration gradient by coupling its transport to that of Na+. Once inside the cytosol, glucose and galactose can be retained for the epithelium's metabolic needs or can exit the cell across its basolateral membrane via facilitated diffusion by a transporter known as GLUT2. Movement of sodium and glucose is an important driving force for water absorption, because accumulation of these solutes on the serosal side provides an efficient driving force for osmotic water absorption.

    Fructose, in contrast, is taken up across the apical membrane by via GLUT5. Fructose may exit the cell through GLUT5, but the main pathway is via GLUT2.

    A key point to understand is that because fructose transport is not coupled to that of Na+, its uptake in comparison is relatively inefficient, and the transporters become saturated if large quantities of food containing free fructose are ingested and fructose is not absorbed – this causes osmotic retention of water in the lumen. The symptoms that occur from this malabsorption are similar to those experienced by a lactose-intolerant patient who consumes lactose. (slide 18 small-intst&colon-White)

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  • 7. 

    Once the pH of the intestinal contents becomes optimal (6.8 - 8.0), digestive enzymes can continue the chemical digestion processes which began in the mouth. Which pancreatic enzyme in its active form is secreted into the duodenum and has its primary action in the duodenum?

    • Trypsin

    • Pepsin

    • Isomaltase

    • Carboxypeptidase A

    • Amylase

    Correct Answer
    A. Amylase
    Explanation
    Amylase is the correct answer because it is a pancreatic enzyme that is secreted into the duodenum and has its primary action in the duodenum. Amylase breaks down starches and carbohydrates into smaller molecules such as glucose, which can then be absorbed by the small intestine. This enzyme is active in the optimal pH range of 6.8 - 8.0, which is achieved in the small intestine.

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  • 8. 

    Thiamin deficiency, which is common in alcoholics, slows the TCA cycle by decreasing the activity of a-ketoglutarate dehydrogenase. This deficiency also decreases the activity of another mitochondrial enzyme resulting in the build- up of pyruvate and a resulting lactic acidosis. The enzyme is:

    • Pyruvate carboxylase

    • Pyruvate kinase

    • Citrate synthetase

    • Pyruvate dehydrogenase

    • Pyruvate decarboxylase

    Correct Answer
    A. Pyruvate dehydrogenase
    Explanation
    Thiamin deficiency in alcoholics decreases the activity of a-ketoglutarate dehydrogenase, which is an enzyme involved in the TCA cycle. This leads to a slower TCA cycle. Additionally, this deficiency also decreases the activity of pyruvate dehydrogenase, another mitochondrial enzyme. As a result, pyruvate accumulates and lactic acidosis occurs. Therefore, the correct answer is Pyruvate dehydrogenase.

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  • 9. 

    You are on a group hiking tour in South Tirol (Europe). You had a brilliant, if slightly strenuous day out and a nice dinner in the hotel, consisting of spinach-filled potato dumplings with tossed salad and fried eggs, accompanied by a local red wine. 2h later you are called to one of your companions, who is feeling sick. You find an elderly lady, pale, clammy, in obvious distress. She is complaining about abdominal pain, vomiting, belching, diarrhea and flatulence. After arranging transport to a local polyclinic you find that temperature, vital signs, EKG, serum analysis, chest and abdominal X-ray and ultrasound are normal. What is the most likely diagnosis?

    • Acute myocardial infarct

    • Stroke

    • Fatigue

    • Food poisoning

    • Lactose incompatibility

    Correct Answer
    A. Lactose incompatibility
    Explanation
    according to buxbaum we should know that in this part of France they use Riccotta CHEESE to prepare their spinach. He also says 2hrs is too soon for food poisoning. (has he ever eaten at the shacks?)

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  • 10. 
    A.B., 40 yo, comes to your surgery because of nodules on hands, elbows and Achilles tendons (see fig.). His own medical history is unremarkable, however, both his father and paternal grandfather have died from M.I. in their early 50s. Physical exam: weight 84 kg, size 1.80m, BP125/70mmHg, other findings normal. Lab investigations on an o/n fasting blood sample result in the following (in mg/dL): Cholesterol 370  200), LDL 300 (100- 130), HDL 32 (29-60), triglycerides 189 (35-150), glucose 90 (70-110).  WHAT is the moste likely diagnosis. - ProProfs

    A.B., 40 yo, comes to your surgery because of nodules on hands, elbows and Achilles tendons (see fig.). His own medical history is unremarkable, however, both his father and paternal grandfather have died from M.I. in their early 50s. Physical exam: weight 84 kg, size 1.80m, BP125/70mmHg, other findings normal. Lab investigations on an o/n fasting blood sample result in the following (in mg/dL): Cholesterol 370  200), LDL 300 (100- 130), HDL 32 (29-60), triglycerides 189 (35-150), glucose 90 (70-110).  WHAT is the moste likely diagnosis.

    • Diabetes mellitus type I (DM-I)

    • Maturity onset diabetes mellitus of the young (MODY)

    • Familial hypercholesterolemia (FH)

    • Metabolic syndrome

    • Neurofibromatosis (NF)

    Correct Answer
    A. Familial hypercholesterolemia (FH)
    Explanation
    The most likely diagnosis for this patient is Familial hypercholesterolemia (FH). This is supported by the high levels of cholesterol, LDL, and triglycerides in the lab investigations. Additionally, the presence of nodules on the hands, elbows, and Achilles tendons is consistent with xanthomas, which are commonly seen in patients with FH. The family history of early myocardial infarction also suggests a genetic component, further supporting the diagnosis of FH. Diabetes mellitus type I, MODY, metabolic syndrome, and neurofibromatosis are not consistent with the patient's presentation and lab results.

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  • 11. 

    A patient has a genetic defect that causes intestinal epithelial cells to produce disaccharidases of much lower activity than normal. Compared with a normal person, after eating a bowl of milk and oatmeal sweetened with table sugar, this patient would exhibit higher levels of which of the following?

    • Starch in the stool

    • Insulin in the blood

    • Galactose and fructose in the blood

    • Glycogen in the muscles

    • Maltose, sucrose and lactose in the stool

    Correct Answer
    A. Maltose, sucrose and lactose in the stool
    Explanation
    A patient with a genetic defect causing lower activity of disaccharidases would have difficulty breaking down disaccharides such as maltose, sucrose, and lactose into their monosaccharide components. As a result, these undigested disaccharides would pass through the digestive system and be excreted in the stool. Therefore, the patient would exhibit higher levels of maltose, sucrose, and lactose in the stool compared to a normal person.

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  • 12. 

    What single factor is most responsible for the elimination of microorganisms in the human stomach?

    • Abundant mucus production

    • The presence of hydrochloric acid

    • The production of pepsinogen by chief cells

    • The release of secretory IgA antibody by gastric epithelial cells

    • The action of cytokines produced by lymphocytes in the lamina propria

    Correct Answer
    A. The presence of hydrochloric acid
    Explanation
    The presence of hydrochloric acid is the most responsible factor for the elimination of microorganisms in the human stomach. Hydrochloric acid creates an acidic environment in the stomach, which is inhospitable for many microorganisms. The low pH of the stomach acid helps to kill or inhibit the growth of bacteria, viruses, and other pathogens that may be ingested with food or water. This acidic environment is an important defense mechanism of the body to prevent infections and maintain a healthy digestive system.

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  • 13. 

    The World Health Organization is encouraging efforts to develop a vaccine against malaria. If the objective is to make a vaccine that can prevent disease in a person who has been bitten by an infected mosquito, what stage of the parasite's life cycle must the vaccine protect against?

    • Gametocyte

    • Merozoite

    • Hypnozoite

    • Sporozoite

    • Trophozoite

    Correct Answer
    A. Sporozoite
    Explanation
    Plasmodium spp. (blood & tissue) TISSUE SPOROZOA
    Vertebrates: intermediate hosts
    Mosquito: definitive host
    (slide 30-33-Protozology-Adebiyi)

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  • 14. 

    What peripheral blood leukocytes do Paneth cells most resemble in terms of their biological activity?

    • Neutrophils

    • Monocytes

    • Basophils

    • Lymphocytes

    • Eosinophils

    Correct Answer
    A. Neutrophils
    Explanation
    Paneth cells are specialized epithelial cells found in the small intestine. They are known for their antimicrobial activity and secretion of various proteins, such as defensins and lysozyme, which help in the defense against pathogens. Neutrophils, similarly, are a type of white blood cells that are also involved in the immune response against infections. They are known for their ability to phagocytose and kill pathogens. Therefore, Paneth cells most resemble neutrophils in terms of their biological activity, as both are involved in the defense against pathogens.

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  • 15. 

    The definitive diagnosis of parasitic infections is frequently made by the examination of stool samples for 'ova and parasites'. However, some parasites do not produce ova that may be voided in stool and diagnosis may be made by other means such as tissue biopsy or from a blood smear. Which of the following parasites may be found in tissue sections but not in a stool sample?

    • Trichinella spiralis

    • Entamoeba histolytica

    • Giardia lamblia

    • Necator americanus

    • Taenia sag mate

    Correct Answer
    A. Trichinella spiralis
    Explanation
    Trichinella spiralis is a nematode parasite, occurring in rats, pigs, bears and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in undercooked pork products.
    Trichinella species are the smallest nematode parasite of humans, have an unusual life cycle and are one of the most widespread and clinically important parasites in the world.[1] The small adult worms mature in the intestines of an intermediate host such as a pig. Each adult female produces batches of live larvae, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system, and are carried to striated muscle Once in the muscle, they encyst, or become enclosed in a capsule. Humans can be infected by eating infected pork or wild carnivores such as fox, cat or bear.[
    Trichinella spiralis is a parasitic nematode that has a direct life cycle, meaning it completes all stages of development in one host. The larval forms are encapsulated as a small cystic structure within the infected host. Humans typically become infected when they eat improperly cooked pork or Trichinella infected meat. When a human eats the infected meat, the larvae are released from the nurse cell (due to stomach pH) and migrate to the intestine, where they burrow into the intestinal mucosa, mature, and reproduce.[2] It is interesting to note that juveniles within nurse cells have an anaerobic or facultative anaerobic metabolism, but when they become activated, they adopt an aerobic metabolism characteristics of the adult. Female Trichinella worms live for about six weeks, and in that time can produce up to 1,500 larvae; when a spent female dies, she passes out of the host. The larvae can then gain access to the circulation and migrate around the body of the host. The migration and encystment of larvae can cause fever and pain brought upon by the host inflammatory response. In some cases, migration to specific organ tissues can cause myocarditis and encephalitis that can result in death.

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  • 16. 

    Ronald Green, a 39-year-old geologist, returned from a 6-month expedition to Peru with a non-healing lesion on his left shin. A smear taken from the edge of the lesion and stained with Wright's stain revealed numerous amastigote-containing macrophages. He was given pentostam for 4 weeks and he recovered completely. The causative agent was most probably:

    • Mycobacterium leprae

    • Leishmania tropica

    • Corynebacterium diphtheria

    • Trypanosoma cruzi

    • Plasmodium falciparum

    Correct Answer
    A. Leishmania tropica
    Explanation
    Cutaneous leishmaniasis (also known as "Leishmaniasis tropica,") is the most common form of leishmaniasis. It is a skin infection caused by a single-celled parasite that is transmitted by SANDFLY bites. There are about 20 species of Leishmania that may cause cutaneous leishmaniasis.
    Diagnosis
    Diagnosis is based on the characteristic appearance of non-healing raised, scaling lesions that may ulcerate and become secondarily infected with organisms such as Staphylococcus aureus, in someone who has returned from an endemic area. The gold standard for diagnosis is PCR.

    Pathophysiology
    Promastigotes of leishmania are transmitted to human skin by the bite of a sandfly. Leishmania then invades human macrophages and replicates intracellularly.
    A raised, red lesion develops at the site of the bite (often weeks or sometimes years afterwards). The lesion then ulcerates and may become secondarily infected with bacteria. In many species (for example, L. major) the lesion often spontaneously heals with atrophic scarring. In some species (for example, L. viannia braziliensis) the lesion may spontaneously heal with scarring, but then re-appear elsewhere (especially as destructive mucocutaneous lesions). Lesions of other leishmania species may spontaneously heal and then re-appear as satellite lesions around the site of the original lesion, or along the route of lymphatic drainage.
    Some species tend to cause cutaneous leishmaniasis (e.g., L. major and L.tropica), whereas some species tend to cause visceral leishmaniasis (e.g., L. infantum and L donovani), though emerging research (due to high deployment rates of western countries to indigenous areas) is showing these species specific presentation lines are blurring

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  • 17. 

    A 25-year-old man who lives near a rapidly running stream presents with a gradual loss of vision. Skin snips from nodules on his trunk reveal the presence of microfilariae. What is the most probable diagnosis?

    • Loiasis

    • Dracunculiasis

    • Onchocerciasis

    • Elephantiasis

    • Fasciolaisis

    Correct Answer
    A. Onchocerciasis
    Explanation
    Onchocerciasis also known as river blindness and Robles' disease, is a parasitic disease caused by infection by Onchocerca volvulus, a nematode (roundworm).
    Onchocerciasis is the world's second-leading infectious cause of blindness. It is not the nematode, but its endosymbiont, Wolbachia pipientis, that causes the severe inflammatory response that leaves many blind. The parasite is transmitted to humans through the bite of a black fly of the genus Simulium. The larval nematodes spread throughout the body. When the worms die, their Wolbachia symbionts are released, triggering a host immune system response that can cause severe itching, and can destroy optical tissue in the eye.
    The vast majority of infections occur in sub-Saharan Africa, although cases have also been reported in Yemen and isolated areas of Central and South America. An estimated 18 million people suffer from onchocerciasis, with approximately 270,000 cases of blindness related to the infection.
    Signs and symptoms
    Adult worms remain in subcutaneous nodules, limiting access to the host's immune system.[ Microfilariae, in contrast, are able to induce intense inflammatory responses, especially upon their death. Dying microfilariae have been recently discovered to release Wolbachia surface protein that activates TLR2 and TLR4, triggering innate immune responses and producing the inflammation and its associated morbidity.[9] Wolbachia species have been found to be endosymbionts of O. volvulus adults and microfilariae, and are thought to be the driving force behind most of O. volvulus morbidity. The severity of illness is directly proportional to the number of infected microfilariae and the power of the resultant inflammatory response
    Skin involvement typically consists of intense itching, swelling, and inflammation. A grading system has been developed to categorize the degree of skin involvement
    • Acute papular onchodermatitis - scattered pruritic papules,
    • Chronic papular onchodermatitis - larger papules, resulting in hyperpigmentation,
    • Lichenified onchodermatitis - hyperpigmented papules and plaques, with edema, Lymphadenopathy, pruritus and common secondary bacterial infections,
    • Skin atrophy - loss of elasticity, the skin resembles tissue paper, 'lizard skin' appearance, and
    • Depigmentation - 'leopard skin' appearance, usually on anterior lower leg.
    Ocular involvement provides the common name associated with onchocerciasis, river blindness, and may involve any part of the eye from conjunctiva and cornea to uvea and posterior segment, including the retina and optic nerve.[ The microfilariae migrate to the surface of the cornea. Punctate keratitis occurs in the infected area. This clears up as the inflammation subsides. However, if the infection is chronic, sclerosing keratitis can occur, making the affected area become opaque. Over time, the entire cornea may become opaque, thus leading to blindness. Some evidence suggests the effect on the cornea is caused by an immune response to bacteria present in the worms..As the skin is itchy, it can lead to severe rashes and you can permanently kill off patches of skin.

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  • 18. 

    At one time, certain people who produced silk had the highest incidence of parasitic infection in the world. In these families, the men spun the silk, while the women and children tended the mulberry bushes for the silk worms to feed on. In order to obtain maximum growth for the mulberry bushes, the women and children would use human feces for manure, which they would place around the bushes and then stamp down the feces with their bare feet. Which parasitic infection would the women and children be most at risk for?

    • Ascariasis

    • Trichinosis

    • Trichuris infection

    • Hookworm

    Correct Answer
    A. Hookworm
    Explanation
    The women and children who tend the mulberry bushes and use human feces for manure are at the highest risk for hookworm infection. Hookworms are parasites that commonly infect humans through contaminated soil. The practice of stomping down the feces with bare feet increases the likelihood of coming into contact with the hookworm larvae, which can penetrate the skin and cause infection. Ascariasis, trichinosis, and trichuris infection are not directly related to the use of human feces as manure and are therefore less likely to be the correct answer in this context.

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  • 19. 

    An individual resides in an area located near a fast flowing river which serves as the breeding site for a type of black fly. This individual is very likely to become exposed to a disease caused by which of the following parasites?

    • Ascaris lumbricoides

    • Enterobius vermicularis

    • Strongyloides stercoralis

    • Necator americanus

    • Wuchereria bancrofti

    • Trichinella spiralis

    • Onchocerca volvulus

    • Diphyllobothrium latum

    Correct Answer
    A. Onchocerca volvulus
    Explanation
    Onchocerciasis also known as river blindness and Robles' disease, is a parasitic disease caused by infection by Onchocerca volvulus, a nematode (roundworm).
    Onchocerciasis is the world's second-leading infectious cause of blindness. It is not the nematode, but its endosymbiont, Wolbachia pipientis, that causes the severe inflammatory response that leaves many blind. The parasite is transmitted to humans through the bite of a black fly of the genus Simulium. The larval nematodes spread throughout the body. When the worms die, their Wolbachia symbionts are released, triggering a host immune system response that can cause severe itching, and can destroy optical tissue in the eye.
    The vast majority of infections occur in sub-Saharan Africa, although cases have also been reported in Yemen and isolated areas of Central and South America. An estimated 18 million people suffer from onchocerciasis, with approximately 270,000 cases of blindness related to the infection.
    Signs and symptoms
    Adult worms remain in subcutaneous nodules, limiting access to the host's immune system.[ Microfilariae, in contrast, are able to induce intense inflammatory responses, especially upon their death. Dying microfilariae have been recently discovered to release Wolbachia surface protein that activates TLR2 and TLR4, triggering innate immune responses and producing the inflammation and its associated morbidity.[9] Wolbachia species have been found to be endosymbionts of O. volvulus adults and microfilariae, and are thought to be the driving force behind most of O. volvulus morbidity. The severity of illness is directly proportional to the number of infected microfilariae and the power of the resultant inflammatory response
    Skin involvement typically consists of intense itching, swelling, and inflammation. A grading system has been developed to categorize the degree of skin involvement
    • Acute papular onchodermatitis - scattered pruritic papules,
    • Chronic papular onchodermatitis - larger papules, resulting in hyperpigmentation,
    • Lichenified onchodermatitis - hyperpigmented papules and plaques, with edema, Lymphadenopathy, pruritus and common secondary bacterial infections,
    • Skin atrophy - loss of elasticity, the skin resembles tissue paper, 'lizard skin' appearance, and
    • Depigmentation - 'leopard skin' appearance, usually on anterior lower leg.
    Ocular involvement provides the common name associated with onchocerciasis, river blindness, and may involve any part of the eye from conjunctiva and cornea to uvea and posterior segment, including the retina and optic nerve.[ The microfilariae migrate to the surface of the cornea. Punctate keratitis occurs in the infected area. This clears up as the inflammation subsides. However, if the infection is chronic, sclerosing keratitis can occur, making the affected area become opaque. Over time, the entire cornea may become opaque, thus leading to blindness. Some evidence suggests the effect on the cornea is caused by an immune response to bacteria present in the worms..As the skin is itchy, it can lead to severe rashes and you can permanently kill off patches of skin.

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  • 20. 

    Many parasitic infections are associated with the presence of insect pests. Which of the following organisms is usually acquired from the bite of a tse tse fly?

    • Ascaris lumbricoides

    • Enterobius vermicularis

    • Cryptosporidium parvum/hominis

    • Necator americanus

    • Wuchereria bancrofti

    • Trypanosoma gambiense

    • Onchocerca volvulus

    • Diphyllobothrium latum

    Correct Answer
    A. Trypanosoma gambiense
    Explanation
    (tsetste rhymes w/ gambiese)

    The insect vector for T. brucei is the TSETSE fly. The parasite lives in the midgut of the fly (procyclic form), whereupon it migrates to the salivary glands for injection to the mammalian host on biting. The parasite lives within the bloodstream (bloodstream form) where it can reinfect the fly vector after biting. Later during a T. brucei infection the parasite may migrate to other areas of the host. A T. brucei infection may be transferred human to human via bodily fluid exchange, primarily blood transfer.

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  • 21. 

    A protozoan with characteristic jerky motility is most commonly observed in

    • Vaginal secretions

    • Duodenal contents

    • Blood

    • Biopsied muscle

    • Sputum

    Correct Answer
    A. Vaginal secretions
    Explanation
    (think, vaginal=sperm=flagella)
    Diagnosis Trichomonas vaginalis (UROGENITAL FLAGELLATE) : flagella appears “jerky”
    Classically, with a cervical smear, infected women have a transparent "halo" around their superficial cell nucleus. It is unreliably detected by studying a genital discharge or with a cervical smear because of their low sensitivity. T. vaginalis was traditionally diagnosed via a wet mount, in which "corkscrew" motility was observed. Currently, the most common method of diagnosis is via overnight culture, with a sensitivity range of 75-95%

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  • 22. 

    A helminth that is naturally transmitted by ingestion of pork, bear, or walrus meat could be detected in

    • Vaginal secretions

    • Duodenal contents

    • Blood

    • Biopsied muscle

    • Sputum

    Correct Answer
    A. Biopsied muscle
    Explanation
    Trichinella spiralis is a nematode parasite, occurring in rats, pigs, bears and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in undercooked pork products.
    Trichinella species are the smallest nematode parasite of humans, have an unusual life cycle and are one of the most widespread and clinically important parasites in the world.[1] The small adult worms mature in the intestines of an intermediate host such as a pig. Each adult female produces batches of live larvae, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system, and are carried to striated muscle Once in the muscle, they encyst, or become enclosed in a capsule. Humans can be infected by eating infected pork or wild carnivores such as fox, cat or bear.[
    Trichinella spiralis is a parasitic nematode that has a direct life cycle, meaning it completes all stages of development in one host. The larval forms are encapsulated as a small cystic structure within the infected host. Humans typically become infected when they eat improperly cooked pork or Trichinella infected meat. When a human eats the infected meat, the larvae are released from the nurse cell (due to stomach pH) and migrate to the intestine, where they burrow into the intestinal mucosa, mature, and reproduce.[2] It is interesting to note that juveniles within nurse cells have an anaerobic or facultative anaerobic metabolism, but when they become activated, they adopt an aerobic metabolism characteristics of the adult.[1] Female Trichinella worms live for about six weeks, and in that time can produce up to 1,500 larvae; when a spent female dies, she passes out of the host. The larvae can then gain access to the circulation and migrate around the body of the host.[2] The migration and encystment of larvae can cause fever and pain brought upon by the host inflammatory response. In some cases, migration to specific organ tissues can cause myocarditis and encephalitis that can result in death.

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  • 23. 

    A 35-year-old attorney has a preference for a special dish made of highly seasoned raw beef served at a local Thai restaurant. He presents with complaints of abdominal cramping and diarrhea and laboratory testing revealed parasite segments (proglottids) in his stool. What organism is the most likely cause of his illness?

    • Taenia saginata

    • Entamoeba histolytica

    • Balantidum coli

    • Taenia solium

    • Echinococcus granulosus

    • He's a lawyer, therefore he is the parasite & can't get one.

    Correct Answer
    A. Taenia saginata
    Explanation
    Taenia saginata, also known as Taeniarhynchus saginata or the beef tapeworm, is a parasite of both cattle and humans, causing taeniasis in humans. Taenia saginata occurs where cattle are raised by infected humans maintaining poor hygiene, human feces are improperly disposed of, meat inspection programs are poor, and where meat is eaten without proper cooking. The disease is relatively common in Africa, some parts of Eastern Europe, Southeast Asia, and Latin America.
    Symptoms
    Tapeworms are usually asymptomatic. However heavy infection often results in weight loss, dizziness, abdominal pain, diarrhea, headaches, nausea, constipation, or chronic indigestion, and loss of appetite. There can be intestinal obstruction in humans and this can be alleviated by surgery

    The basic **DIAGNOSIS** is done from a stool sample. Feces are examined to find parasite eggs.
    (ironically, even parasites can be infected with parasites)

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  • 24. 

    Students who live in the Portsmouth area often complain about getting bitten by sand flies while dining in the open air. What potentially pathogenic organism may be transmitted by the sand flies?

    • Wuchereria bancrofti

    • Loa loa

    • Trypanosoma cruzi

    • Balantidum coli

    • Leishmania major

    Correct Answer
    A. Leishmania major
    Explanation
    Cutaneous leishmaniasis (also known as "Leishmaniasis tropica,") is the most common form of leishmaniasis. It is a skin infection caused by a single-celled parasite that is transmitted by SANDFLY bites. There are about 20 species of Leishmania that may cause cutaneous leishmaniasis.
    Diagnosis
    Diagnosis is based on the characteristic appearance of non-healing raised, scaling lesions that may ulcerate and become secondarily infected with organisms such as Staphylococcus aureus, in someone who has returned from an endemic area. The gold standard for diagnosis is PCR.

    Pathophysiology
    Promastigotes of leishmania are transmitted to human skin by the bite of a sandfly. Leishmania then invades human macrophages and replicates intracellularly.
    A raised, red lesion develops at the site of the bite (often weeks or sometimes years afterwards). The lesion then ulcerates and may become secondarily infected with bacteria. In many species (for example, L. major) the lesion often spontaneously heals with atrophic scarring. In some species (for example, L. viannia braziliensis) the lesion may spontaneously heal with scarring, but then re-appear elsewhere (especially as destructive mucocutaneous lesions). Lesions of other leishmania species may spontaneously heal and then re-appear as satellite lesions around the site of the original lesion, or along the route of lymphatic drainage.
    Some species tend to cause cutaneous leishmaniasis (e.g., L. major and L.tropica), whereas some species tend to cause visceral leishmaniasis (e.g., L. infantum and L donovani), though emerging research (due to high deployment rates of western countries to indigenous areas) is showing these species specific presentation lines are blurring

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  • Mar 20, 2023
    Quiz Edited by
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  • Feb 26, 2012
    Quiz Created by
    Chachelly

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