Tularemia — MCQs
In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?
Zoonotic diseases are -
Which bacterial disease is commonly associated with the three "Rs": rats, rice fields, and rainfall?
Mass chemoprophylaxis in endemic areas is recommended for all of the following, except:
Which of the following is a Category C bioterrorism agent?
A clinically depressed farmer complains of extreme weakness, a daily rise and fall in fever, and night sweats. Small gram-negative rods are isolated from blood cultures after a 2-week incubation period. Which of the following organisms is the most likely etiologic agent?
Erysipeloid is transmitted by which route?
Four weeks after assisting in several calf deliveries, a farmer develops fever, weakness, muscle aches, and sweats. The fever rises in the afternoon and falls during the night. A Brucella species is isolated. Which Brucella species is a possible bioterrorism agent and is best described by one of the following?
Targeted critical agents used in a bioterrorist event are except?
Assertion: Myocarditis is seen as a complication in faucial diphtheria. Reason: It is due to the exotoxin produced by Corynebacterium diphtheriae.
Tularemia Indian Medical PG Practice Questions and MCQs
Question 1: In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?
- A. Bone marrow biopsy
- B. DEC provocation test
- C. Detection of microfilariae in the blood smear (Correct Answer)
- D. Ultrasound of the scrotum
Explanation: ***Detection of microfilariae in the blood smear*** - A positive **filarial antigen test** indicates the presence of adult worms, and the next step is to confirm active infection by identifying **microfilariae**. [1] - **Nocturnal blood samples** are crucial because microfilariae of *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. [1] *Bone marrow biopsy* - This procedure is typically used to diagnose **hematological disorders**, such as leukemia or lymphoma, or investigate causes of unexplained fever, but it is not indicated for filariasis. - While filariasis can rarely lead to **eosinophilia**, a bone marrow biopsy is not a diagnostic tool for filarial infection itself. *DEC provocation test* - The **diethylcarbamazine (DEC) provocation test** is used to bring out microfilariae into the peripheral blood during the daytime for species that exhibit nocturnal periodicity. [1] - However, it carries a risk of severe adverse reactions due to rapid killing of microfilariae, especially in cases of heavy infection, and is generally avoided when antigen tests are positive. [1] *Ultrasound of the scrotum* - Scrotal ultrasound can detect the characteristic "filarial dance sign" (motile adult worms) in the **lymphatic vessels of the scrotum and epididymis**, confirming lymphatic filariasis. [2] - While useful for assessing advanced disease manifestations like **hydrocele**, it does not quantify microfilaremia or replace the need for microscopic confirmation of circulating microfilariae to guide treatment.
Question 2: Zoonotic diseases are -
- A. Anthrax
- B. Plague
- C. Salmonellosis
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Anthrax**, **Plague**, and **Salmonellosis** are all well-established examples of zoonotic diseases, which are infections naturally transmitted between vertebrate animals and humans. - These diseases represent a diverse spectrum of bacterial infections with significant public health implications worldwide. **Anthrax** - Caused by *Bacillus anthracis*, a spore-forming bacterium naturally found in soil that primarily affects livestock and wild herbivores. - Humans acquire infection through contact with infected animals or contaminated animal products (hides, wool, meat). - Clinical forms include cutaneous (most common), inhalational (most severe), and gastrointestinal anthrax. - Remains an important occupational hazard for veterinarians, farmers, and those handling animal products. **Plague** - Caused by *Yersinia pestis*, maintained in nature through rodent-flea cycles. - Transmission to humans occurs primarily via bites from infected fleas or direct contact with infected animals. - Historically responsible for devastating pandemics including the Black Death. - Clinical manifestations include bubonic (most common), pneumonic (person-to-person transmission possible), and septicemic plague. **Salmonellosis** - Caused by non-typhoidal *Salmonella* species, commonly colonizing the intestines of various animals including poultry, cattle, reptiles, and pets. - Humans typically acquire infection through consumption of contaminated food (undercooked meat, eggs, unpasteurized dairy) or direct animal contact. - Presents as acute gastroenteritis with diarrhea, fever, and abdominal cramps. - One of the most common foodborne zoonotic infections globally.
Question 3: Which bacterial disease is commonly associated with the three "Rs": rats, rice fields, and rainfall?
- A. Leptospirosis (Correct Answer)
- B. Bubonic plague
- C. Haverhill fever
- D. Melioidosis
Explanation: ***Leptospirosis*** - This disease is directly associated with exposure to environments contaminated by **animal urine**, often linked to **rats** in environments like **rice fields** where **rainfall** creates favorable conditions for bacterial survival and transmission. - The classic **"3 Rs" mnemonic** (Rats, Rice fields, Rainfall) specifically describes leptospirosis epidemiology. - **Leptospira** bacteria typically enter the body through cuts or abrasions in the skin or through mucous membranes, especially when prolonged exposure to contaminated water occurs. - Common in **occupational groups**: farmers, sewer workers, veterinarians, and military personnel. *Bubonic plague* - Characterized by acute onset of fever, chills, weakness, and painful, swollen lymph nodes called **buboes**, caused by **Yersinia pestis**. - Primarily transmitted to humans through bites of **infected fleas** that have fed on rodents, not directly through contaminated water or rice fields. - While associated with rats, lacks the rice field and rainfall environmental components. *Haverhill fever* - Caused by **Streptobacillus moniliformis**, a form of **rat-bite fever** contracted through rodent contact or ingestion of contaminated food/water. - While associated with rats, it doesn't have the specific environmental triad of **rice fields** and **rainfall** as central to its epidemiology like leptospirosis. - Transmission is primarily through rat bites or contaminated milk products. *Melioidosis* - Caused by **Burkholderia pseudomallei**, found in soil and water in tropical and subtropical regions. - While found in water and soil with potential agricultural exposure, it is **not specifically linked** to the "rats, rice fields, and rainfall" triad that defines leptospirosis. - More commonly associated with direct soil contact rather than rat-contaminated environments.
Question 4: Mass chemoprophylaxis in endemic areas is recommended for all of the following, except:
- A. Leprosy (Correct Answer)
- B. Trachoma
- C. Yaws
- D. Filaria
Explanation: ***Leprosy*** - **Mass chemoprophylaxis** for leprosy is generally *not recommended* due to concerns about drug resistance and the long incubation period. - Instead, the focus is on **early detection** and *multi-drug therapy (MDT)* for diagnosed cases, and contact tracing with single-dose rifampicin (SDR) as post-exposure prophylaxis for close contacts in some settings. *Trachoma* - **Mass drug administration (MDA)** of *azithromycin* is a cornerstone of the **SAFE strategy** (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) for eliminating trachoma, recommended in endemic areas. - This aims to reduce the community reservoir of *Chlamydia trachomatis* infection, thus preventing new infections and progression of the disease. *Yaws* - **Mass treatment programs** with a *single oral dose of azithromycin* have been highly effective and are recommended by the WHO for the eradication of yaws in endemic communities. - This strategy aims to interrupt transmission and eliminate the *Treponema pallidum subspecies pertenue* bacterium. *Filaria* - **Mass drug administration (MDA)** with anti-filarial drugs (e.g., *diethylcarbamazine and albendazole*) is a key strategy for the elimination of lymphatic filariasis in endemic areas. - MDA aims to reduce the microfilaria burden in infected individuals, thereby interrupting transmission of the parasite by mosquitoes.
Question 5: Which of the following is a Category C bioterrorism agent?
- A. Botulism
- B. Nipah virus (Correct Answer)
- C. Clostridium Perfringens
- D. Plague
Explanation: ***Nipah virus*** - **Nipah virus** is classified as a **Category C bioterrorism agent** due to its potential for high mortality, emerging threat, and ease of genetic engineering. - These agents are emerging pathogens that could be engineered for **mass dissemination** in the future and require ongoing surveillance. *Botulism* - **Botulism**, caused by *Clostridium botulinum* toxin, is a **Category A bioterrorism agent** due to its high mortality and ease of dissemination. - Category A agents pose the greatest threat to public health and national security. *Clostridium Perfringens* - *Clostridium perfringens* is classified as a **Category B bioterrorism agent** because it can be used to contaminate food and water supplies. - Category B agents are moderately easy to disseminate and cause moderate morbidity but lower mortality than Category A agents. *Plague* - **Plague**, caused by *Yersinia pestis*, is a **Category A bioterrorism agent** because of its high mortality, potential for aerosol dissemination, and risk of causing public panic. - The CDC categorizes agents based on the risk they pose to national security.
Question 6: A clinically depressed farmer complains of extreme weakness, a daily rise and fall in fever, and night sweats. Small gram-negative rods are isolated from blood cultures after a 2-week incubation period. Which of the following organisms is the most likely etiologic agent?
- A. Campylobacter jejuni
- B. Francisella tularensis
- C. Brucella melitensis (Correct Answer)
- D. Salmonella enteritidis
Explanation: ***Brucella melitensis*** - This organism is known to cause **brucellosis**, which presents with **undulant fever** (daily rise and fall), night sweats, and fatigue, consistent with the patient's symptoms. The profession of a **farmer** puts him at higher risk due to exposure to infected livestock. - **Neuropsychiatric manifestations** including depression, fatigue, and malaise are well-recognized features of chronic brucellosis, explaining the patient's clinical depression. - **_Brucella_ species** are characteristic for their slow growth, often requiring **extended incubation periods** (up to 2 weeks) in blood cultures, and appear as small gram-negative rods. *Campylobacter jejuni* - This bacterium is a common cause of **gastroenteritis**, leading to **diarrhea**, abdominal cramps, and fever. While it can cause bacteremia, it typically presents with more prominent gastrointestinal symptoms. - _C. jejuni_ is a **curved or spiral-shaped** gram-negative rod, distinct from the small rods described, and does not typically cause an undulant fever pattern. *Francisella tularensis* - This agent causes **tularemia**, which can manifest with fever, chills, and fatigue, but often includes a characteristic **skin lesion (ulceroglandular)** and prominent lymphadenopathy. - Although it is a small gram-negative rod, the specific **undulant fever pattern** and the farmer's exposure history are more indicative of brucellosis. *Salmonella enteritidis* - This bacterium commonly causes **food poisoning** with symptoms like diarrhea, fever, and vomiting. While it can lead to bacteremia, it is less likely to present with the prolonged, **undulant fever** seen in brucellosis. - **_Salmonella_ species** are typically readily isolated from blood cultures within a few days, unlike the prolonged incubation needed for _Brucella_.
Question 7: Erysipeloid is transmitted by which route?
- A. Droplet
- B. Mosquito bite
- C. Fecal-oral
- D. Direct contact (Correct Answer)
Explanation: ***Direct contact*** - Erysipeloid, caused by *Erysipelothrix rhusiopathiae*, is transmitted through direct contact with **infected animal products**, especially fish, shellfish, and raw meat. - The bacteria typically enter through a **break in the skin**, such as a cut or abrasion, making occupational exposure common among butchers and fishmongers. *Droplet* - **Droplet transmission** involves the spread of respiratory droplets through coughing or sneezing, which is characteristic of airborne diseases like influenza. - Erysipeloid is primarily a **skin infection** and is not transmitted via the respiratory route. *Mosquito bite* - **Mosquito bites** are vectors for diseases like malaria, dengue, and West Nile virus, where the pathogen is injected directly into the bloodstream. - Erysipeloid is a bacterial infection acquired through **skin contact with contaminated materials**, not insect vectors. *Fecal-oral* - The **fecal-oral route** involves ingesting pathogens from contaminated food or water, often associated with gastrointestinal infections like cholera or giardiasis. - Erysipeloid is a **cutaneous infection** and does not involve the gastrointestinal tract as its primary mode of transmission.
Question 8: Four weeks after assisting in several calf deliveries, a farmer develops fever, weakness, muscle aches, and sweats. The fever rises in the afternoon and falls during the night. A Brucella species is isolated. Which Brucella species is a possible bioterrorism agent and is best described by one of the following?
- A. Typically infects goats and sheep, grows well in CO2, and is not inhibited by thionine or basic fuchsin dyes (Correct Answer)
- B. Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive
- C. Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis
- D. Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora
Explanation: ***Typically infects goats and sheep, grows well in CO2, and is not inhibited by thionine or basic fuchsin dyes*** - This description is characteristic of ***Brucella melitensis***, which is recognized as the most pathogenic **Brucella** species and a potential **bioterrorism agent** (CDC Category B) due to its high infectivity and severe disease course. - Its specific growth requirements (CO2 preference) and dye resistance patterns (not inhibited by **thionine** or **basic fuchsin**) are key laboratory identifiers that differentiate it from other **Brucella** species (*B. abortus* is inhibited by thionine; *B. suis* is inhibited by basic fuchsin). - Low infective dose (10-100 organisms) and aerosol transmission capability make it a significant bioterrorism threat. *Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive* - This describes ***Bordetella bronchiseptica***, not a **Brucella** species. It is a pathogen primarily associated with animals, especially dogs (kennel cough), and only rarely causes disease in immunocompromised humans. - While it can be urease-positive, it belongs to a different genus and does not fit the clinical or epidemiological context of brucellosis. *Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis* - This description points to ***Yersinia enterocolitica***, not a **Brucella** species. It is a **Gram-negative bacterium** known for causing gastrointestinal infections with symptoms that can mimic **appendicitis** (pseudoappendicitis syndrome). - Its characteristic **bipolar staining** ("safety pin" appearance) and production of **heat-stable enterotoxin** are distinct from **Brucella** species. *Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora* - This description is typical of ***Eikenella corrodens***, not a **Brucella** species. It is a **Gram-negative bacillus** found in the **normal oral flora** that can cause infections related to human bites or dental procedures. - Its ability to "pit" agar and specific atmospheric growth requirements (CO2 and anaerobic) are unique characteristics that differentiate it from **Brucella** species.
Question 9: Targeted critical agents used in a bioterrorist event are except?
- A. Ricinus communis
- B. Small pox
- C. Coxiella burnetii (Correct Answer)
- D. Viral hemorrhagic fevers -Junin virus
Explanation: ***Coxiella burnetii*** - This is the **correct answer** as it is classified as a **Category B biological agent**, not a Category A critical agent. - While *C. burnetii* causes **Q fever** and has high infectivity with potential for widespread illness, it typically has **lower mortality rates** compared to Category A agents. - Category B agents are second-priority because they are moderately easy to disseminate but cause lower mortality than Category A agents. *Ricinus communis* - This refers to **ricin toxin** derived from castor beans, classified as a **Category B agent**. - However, ricin is considered more dangerous than Q fever due to its potent toxicity and lack of antidote. - Can cause severe multi-organ damage upon inhalation or ingestion, though less lethal than Category A agents. *Smallpox* - Caused by **variola virus**, classified as a **Category A critical agent**. - High infectivity, severe illness, high mortality rate, and lack of natural immunity in most populations. - Historical use as a bioweapon and potential for rapid global spread make it a top-tier threat. *Viral hemorrhagic fevers - Junin virus* - **Category A critical agent** due to high infectivity, severe disease presentation, and high mortality rates. - Includes agents like Ebola, Marburg, Lassa, and Junin viruses that cause severe multi-system disease. - Person-to-person transmission potential and lack of effective treatments make these priority threats.
Question 10: Assertion: Myocarditis is seen as a complication in faucial diphtheria. Reason: It is due to the exotoxin produced by Corynebacterium diphtheriae.
- A. Assertion is false, reason is true.
- B. Assertion is true, reason is true but reason is not the correct explanation of the assertion.
- C. Assertion is true, reason is true.
- D. Assertion is true, reason is true and reason is the correct explanation of the assertion. (Correct Answer)
Explanation: ***Assertion is true, reason is true and reason is the correct explanation of the assertion*** **Analysis of Assertion:** - Myocarditis is indeed a **well-documented complication** of faucial (pharyngeal) diphtheria, occurring in 10-25% of cases - It typically appears in the **second to third week** of illness and is a major cause of mortality in diphtheria - Cardiac involvement can range from asymptomatic ECG changes to severe heart failure and cardiogenic shock **Analysis of Reason:** - The **diphtheria exotoxin** produced by *Corynebacterium diphtheriae* is directly responsible for myocardial damage - The toxin inhibits protein synthesis by **ADP-ribosylation of elongation factor-2 (EF-2)**, leading to cell death - Cardiac myocytes are particularly vulnerable to this toxin, resulting in **toxic myocarditis** **Why the reason is the correct explanation:** - The mechanism of myocarditis in diphtheria is specifically through the **cardiotoxic effect of the exotoxin**, not through immune mechanisms or bacterial invasion - This establishes a direct **cause-and-effect relationship** between the exotoxin (reason) and myocarditis (assertion) *Incorrect Options:* *Assertion is false, reason is true* - This is incorrect because the assertion is definitely true - myocarditis is a classic complication of diphtheria documented in all standard microbiology and infectious disease texts *Assertion is true, reason is true but reason is not the correct explanation of the assertion* - This is incorrect because the exotoxin IS the direct cause of myocarditis in diphtheria - the reason perfectly explains the assertion through a clear pathophysiological mechanism *Assertion is true, reason is true* - While this correctly identifies both statements as true, it fails to acknowledge the **causal relationship** - the exotoxin doesn't just happen to be produced; it is the specific mechanism causing the myocarditis
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