Ectoparasites and vector-borne diseases — MCQs

A 34-year-old man comes to the physician because of progressive swelling of the left lower leg for 4 months. One year ago, he had an episode of intermittent fever and tender lymphadenopathy that occurred shortly after he returned from a trip to India and resolved spontaneously. Physical examination shows 4+ nonpitting edema of the left lower leg. His leukocyte count is 8,000/mm3 with 25% eosinophils. A blood smear obtained at night confirms the diagnosis. Treatment with diethylcarbamazine is initiated. Which of the following is the most likely route of transmission of the causal pathogen?

A 45-year-old man presents to the physician with complaints of fever with rigors, headache, malaise, muscle pains, nausea, vomiting, and decreased appetite for the past 3 days. He informs the physician that he had been backpacking on the Appalachian Trail in the woods of Georgia in the month of June, 2 weeks ago, and had been bitten by a tick there. His temperature is 39.0°C (102.3°F), pulse is 94/min, respirations are 18/min, and blood pressure is 126/82 mm Hg. His physical exam does not reveal any significant abnormality except for mild splenomegaly. Laboratory studies show: Total white blood cell count 3,700/mm3 (3.7 x 109/L) Differential count Neutrophils 85% Lymphocytes 12% Monocytes 2% Eosinophils 1% Basophils 0% Platelet count 88,000/mm3 (95 x 109/L) Serum alanine aminotransferase 140 IU/L Serum aspartate aminotransferase 80 IU/L Microscopic examination of a peripheral blood smear stained with Wright-Giemsa stain shows the presence of morulae in the cytoplasm of leukocytes. In addition to drugs for symptomatic relief, what is the most appropriate initial step in the treatment of this patient?

A 33-year-old man presents to the emergency department with a fever and fatigue. He states that he has not felt well since he returned from a hiking trip in Alabama. He is generally healthy and has no other medical conditions. His temperature is 101°F (38.3°C), blood pressure is 127/85 mmHg, pulse is 108/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam including a full dermatologic inspection is unremarkable. Laboratory studies are ordered as seen below. Hemoglobin: 13 g/dL Hematocrit: 39% Leukocyte count: 2,200/mm^3 with normal differential Platelet count: 77,000/mm^3 Serum: Na+: 139 mEq/L Cl-: 100 mEq/L K+: 4.3 mEq/L HCO3-: 24 mEq/L BUN: 19 mg/dL Glucose: 98 mg/dL Creatinine: 1.3 mg/dL Ca2+: 10.2 mg/dL AST: 92 U/L ALT: 100 U/L Which of the following is the most likely diagnosis?

A 32-year-old woman presents to your office with abdominal pain and bloating over the last month. She also complains of intermittent, copious, non-bloody diarrhea over the same time. Last month, she had a cough that has since improved but has not completely resolved. She has no sick contacts and has not left the country recently. She denies any myalgias, itching, or rashes. Physical and laboratory evaluations are unremarkable. Examination of her stool reveals the causative organism. This organism is most likely transmitted to the human host through which of the following routes?

A 42-year-old man presents to a free dermatology clinic, complaining of itchy skin over the past several days. He has no insurance and lives in a homeless shelter. The patient has no significant medical history. Physical evaluation reveals 2 mm erythematous papules and vesicles on his back and groin, with linear excoriation marks. Careful observation of his hands reveals serpiginous, grayish, threadlike elevations in the superficial epidermis, ranging from 3–9 mm in length in the webbing between several digits. What should be the suggested treatment in this case?

A 20-year-old man comes to the physician because of a 3-day history of fever, myalgia, and swelling in his left groin after a recent camping trip in northern California. He appears acutely ill. Physical examination shows tender, left-sided inguinal lymphadenopathy and an enlarged, tender lymph node in the right axilla that is draining bloody necrotic material. Microscopic examination of a lymph node aspirate shows gram-negative coccobacilli with bipolar staining and a safety-pin appearance. This patient's condition is most likely caused by an organism with which of the following reservoirs?

A 24-year-old female comes to the physician because of flu-like symptoms and a new rash for 2 days. She denies contacts with sick individuals or recent travel abroad, but recently went camping in Vermont. Vital signs are within normal limits. Examination of the lateral right thigh shows a circular red ring with central clearing. Which of the following is the natural reservoir of the pathogen responsible for this patient's symptoms?

A 29-year-old man comes to the physician because of a 3-day history of a swollen right knee. Over the past several weeks, he has had similar episodes affecting the right knee and sometimes also the left elbow, in which the swelling lasted an average of 5 days. He has a history of a rash that subsided 2 months ago. He lives in Connecticut with his wife and works as a landscaper. His temperature is 37.8°C (100°F), pulse is 90/min, respirations are 12/min, and blood pressure is 110/75 mm Hg. Physical examination shows a tender and warm right knee; range of motion is limited by pain. The remainder of the examination shows no abnormalities. His hematocrit is 44%, leukocyte count is 10,300/mm3, and platelet count is 145,000/mm3. Serum electrolyte concentrations are within normal limits. Arthrocentesis is performed and the synovial fluid is cloudy. Gram stain is negative. Analysis of the synovial fluid shows a leukocyte count of 70,000/mm3 and 80% neutrophils. Serologic testing confirms the diagnosis. Which of the following is the most likely cause?

A 32-year-old man is brought to the physician by his wife for a 3-day history of fever, headaches, and myalgias. He returned from a camping trip in Oklahoma 10 days ago. He works as a computer salesman. His temperature is 38.1°C (100.6°F). Neurologic examination shows a sustained clonus of the right ankle following sudden passive dorsiflexion. He is disoriented to place and time but recognizes his wife. Laboratory studies show a leukocyte count of 1,700/mm3 and a platelet count of 46,000/mm3. A peripheral blood smear shows monocytes with intracytoplasmic morulae. Which of the following is the most likely causal organism?

A 45-year-old male presents to his primary care physician complaining of drainage from his left great toe. He has had an ulcer on his left great toe for over eight months. He noticed increasing drainage from the ulcer over the past week. His past medical history is notable for diabetes mellitus on insulin complicated by peripheral neuropathy and retinopathy. His most recent hemoglobin A1c was 9.4%. He has a 25 pack-year smoking history. He has multiple sexual partners and does not use condoms. His temperature is 100.8°F (38.2°C), blood pressure is 150/70 mmHg, pulse is 100/min, and respirations are 18/min. Physical examination reveals a 1 cm ulcer on the plantar aspect of the left great toe surrounded by an edematous and erythematous ring. Exposed bone can be palpated with a probe. There are multiple small cuts and bruises on both feet. A bone biopsy reveals abundant gram-negative rods that do not ferment lactose. The pathogen most likely responsible for this patient’s current condition is also strongly associated with which of the following conditions?