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Part XII: Pearls for the USMLE: Introduction

PEARLS FOR THE USMLE: INTRODUCTION

Many questions on the USMLE can be answered by knowing the meaning of the epidemiologic information provided in the case description. In order to do this, the student should know the reservoir of the organism, its mode of transmission, and the meaning of factors such as travel, occupation, and exposure to pets, farm animals, or wild animals. Knowledge of the microbes that typically cause disease in individuals with specific immunodeficiencies will also be helpful.

In addition to being useful for the USMLE, this information will prove valuable to make the diagnosis of infectious diseases on the wards and in your clinical practice.

The “Pearls” are presented in tables entitled:

Table XII–1. Farm Animals and Household Pets as Reservoirs of Medically Important Organisms

TABLE XII–1Farm Animals and Household Pets as Reservoirs of Medically Important Organisms
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TABLE XII–1 Farm Animals and Household Pets as Reservoirs of Medically Important Organisms
Animal Mode of Transmission Important Organisms Disease
Cattle/cows

1. Ingestion of meat1

 

 

 

 

2. Ingestion of milk products2

 

 

3. Contact with animal hides

1. Escherichia coli O157

2. Salmonella enterica

3. Prions

4. Taenia saginata

5. Toxoplasma gondii

1. Listeria monocytogenes

2. Brucella species

3. Mycobacterium bovis

Bacillus anthracis

Enterocolitis and hemolytic-uremic syndrome

Enterocolitis

Variant Creutzfeldt-Jakob disease

Taeniasis (intestinal tapeworm)

Toxoplasmosis

Neonatal sepsis

Brucellosis

Intestinal tuberculosis

Anthrax
Sheep Inhalation of amniotic fluid Coxiella burnetii Q fever
Goats Ingestion of milk products2 Brucella species Brucellosis
Pigs Ingestion of meat1

1. Taenia solium

2. Trichinella spiralis

Taeniasis (intestinal tapeworm)3

Trichinosis
Poultry (chickens; turkeys) Ingestion of meat or eggs1

1. S. enterica

2. Campylobacter jejuni

Enterocolitis

Enterocolitis
Dogs

1. Ingestion of dog feces

 

2. Ingestion of dog urine

3. Dog bite

 

4. Direct contact

1. Echinococcus granulosus

2. Toxocara canis

Leptospira interrogans

1. Rabies virus

2. Capnocytophaga canimorsus

Microsporum canis

Echinococcosis

Visceral larva migrans

Leptospirosis

Rabies

Sepsis

Tinea corporis
Cats

1. Ingestion of cat feces

2. Cat bite/scratch

T. gondii

1. Pasteurella multocida

2. Bartonella henselae

3. Rabies virus

Toxoplasmosis

Cellulitis

Cat-scratch disease; bacillary angiomatosis

Rabies

1Raw or undercooked.

2Unpasteurized.

3Ingestion of eggs in human feces, not ingestion of pork, results in cysticercosis.

Table XII–2. Wild Animals as Reservoirs of Medically Important Organisms

TABLE XII–2Wild Animals as Reservoirs of Medically Important Organisms
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TABLE XII–2 Wild Animals as Reservoirs of Medically Important Organisms
Animal Mode of Transmission Important Organisms Disease
Rats

1. Flea bite

2. Ingestion of urine

Yersinia pestis

Leptospira interrogans

Plague

Leptospirosis
Mice

1. Tick bite

2. Inhale aerosol of droppings

Borrelia burgdorferi

Hantavirus

Lyme disease

Hantavirus

Pulmonary syndrome
Bats, skunks, raccoons, and foxes Bite Rabies virus Rabies
Rabbits Contact Francisella tularensis Tularemia
Bats Inhale aerosol Coronavirus—SARS-1&2 Pneumonia
Camels Inhale aerosol Coronavirus—MERS Pneumonia
Monkeys Mosquito bite Yellow fever virus Yellow fever

Birds ...

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