Zoonotic Diseases Practice Questions

Q: What is the causative agent for Oculoglandular syndrome of Parinaud?

Bartonella henselae. **Explanation:** **Parinaud Oculoglandular Syndrome (POGS)** is a clinical triad characterized by unilateral granulomatous conjunctivitis, a visible conjunctival nodule, and ipsilateral regional lymphadenopathy (typically preauricular or submandibular). 1. **Why Bartonella henselae is correct:** * *Bartonella henselae* is a gram-negative rod and the causative agent of **Cat-Scratch Disease (CSD)**. It is the most common cause of POGS (responsible for ~5-7% of CSD cases). * Transmission occurs via a scratch or bite from an infected cat (usually a kitten) or via flea feces inoculated into the conjunctiva. * The organism triggers a granulomatous immune response in the conjunctival stroma and draining lymph nodes. 2. **Why the other options are incorrect:** * **Arachnia propionica:** Now known as *Propionibacterium propionicum*, it is a common cause of **canaliculitis** (concretions in the lacrimal canaliculi), not POGS. * **Bifidobacterium dentium:** This is a commensal of the oral cavity associated with dental caries; it does not have a recognized role in oculoglandular syndromes. * **Mycobacterium leprae:** While Leprosy causes various ocular issues (madarosis, lagophthalmos, uveitis), it is not the primary agent for Parinaud Oculoglandular Syndrome. (Note: *Mycobacterium tuberculosis* and *Tularemia* are rarer causes of POGS). **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Usually clinical + history of cat contact. Confirmed via **Warthin-Starry silver stain** (shows pleomorphic bacilli) or Serology (IFA/ELISA). * **Treatment:** Often self-limiting, but systemic **Azithromycin** is the drug of choice to reduce lymph node volume. * **Distinction:** Do not confuse *Parinaud Oculoglandular Syndrome* with *Parinaud (Dorsal Midbrain) Syndrome*, which involves vertical gaze palsy and is caused by pineal gland tumors.

Q: A patient presented with fever, headache, rash, and eschar. You suspect a rickettsial disease. Which of the following is the LEAST likely disease in this case?

Endemic typhus. ### Explanation The presence of an **eschar** (a necrotic, black crust at the site of the vector bite) is a crucial clinical diagnostic clue in rickettsial diseases. This question tests your ability to differentiate between rickettsial infections based on this specific cutaneous finding. **1. Why Endemic Typhus is the correct answer:** Endemic typhus (also known as Murine typhus) is caused by *Rickettsia typhi* and transmitted by the rat flea (*Xenopsylla cheopis*). Unlike the spotted fever group or scrub typhus, **Endemic typhus and Epidemic typhus (Louse-borne) typically do not present with an eschar.** Therefore, it is the least likely diagnosis in a patient presenting with an eschar. **2. Analysis of Incorrect Options:** * **Indian Tick Typhus:** Caused by *R. conorii*. As a member of the Spotted Fever Group, it is frequently associated with a characteristic eschar (tache noire) at the tick bite site. * **Rickettsial Pox:** Caused by *R. akari*. It is unique because it presents with a papulovesicular rash and is classically preceded by a **prominent eschar** at the site of the mite bite. * **Scrub Typhus:** Caused by *Orientia tsutsugamushi*. The **eschar** is a hallmark clinical sign of scrub typhus (found in up to 50% of cases), often located in skin folds or axilla. ### Clinical Pearls for NEET-PG: * **Eschar-Positive Diseases:** Scrub typhus, Rickettsial pox, and most Spotted Fever Group diseases (except Rocky Mountain Spotted Fever, where an eschar is rare). * **Eschar-Negative Diseases:** Epidemic typhus, Endemic typhus, and Q fever. * **Weil-Felix Reaction:** * Scrub Typhus: OX-K positive. * Endemic/Epidemic Typhus: OX-19 positive. * Spotted Fever Group: OX-19 and OX-2 positive. * **Q Fever:** Negative for all Weil-Felix antigens.

Q: What is the mode of transmission of Q fever?

Inhalation of aerosol. **Explanation:** **Q Fever** is caused by the obligate intracellular bacterium ***Coxiella burnetii***. Unlike other Rickettsial diseases, the primary mode of transmission to humans is the **inhalation of contaminated aerosols** or dust. 1. **Why Option C is Correct:** *C. burnetii* is highly resistant to environmental stressors (heat, drying) due to its spore-like stage. It is found in high concentrations in the birth products (placenta), urine, and feces of infected livestock (sheep, goats, cattle). When these materials dry, the bacteria become airborne, and humans are infected by inhaling as few as 1 to 10 organisms. 2. **Why Other Options are Incorrect:** * **Option A (Louse):** This is the vector for Epidemic Typhus (*Rickettsia prowazekii*). * **Option B (Tick):** While ticks maintain the cycle among wild animals and can transmit the bacteria to livestock, they are **not** the primary source of infection for humans. * **Option D (Mice):** Rodents are not the typical reservoir for Q fever; it is primarily a zoonosis of farm animals. **High-Yield Clinical Pearls for NEET-PG:** * **Occupational Hazard:** Most common in farmers, veterinarians, and abattoir workers. * **Clinical Presentation:** Presents as an atypical pneumonia or hepatitis (Acute Q fever). Chronic Q fever most commonly manifests as **culture-negative endocarditis**. * **Diagnosis:** Serology is the gold standard (Indirect Immunofluorescence Assay). * **Weil-Felix Test:** Q fever is **Weil-Felix negative** (unlike most other Rickettsial diseases). * **Treatment:** Doxycycline is the drug of choice.

Q: Q. Which organism is a cause of fever?

Coxiella burnetii. **Explanation:** The correct answer is **Coxiella burnetii**, which is the causative agent of **Q fever**. **1. Why Coxiella burnetii is correct:** Q fever (Query fever) is a zoonotic disease typically transmitted via inhalation of contaminated aerosols from livestock (cattle, sheep, goats). Unlike other Rickettsial diseases, Q fever is characterized by a high-grade fever, interstitial pneumonia, and hepatitis, but it **characteristically lacks a skin rash**. This makes it a unique "fever of unknown origin" in clinical presentations. **2. Why the other options are incorrect:** * **Ehrlichia sennetsu:** This organism causes **Sennetsu fever** (human monocytotropic ehrlichiosis), primarily seen in Southeast Asia and Japan. While it causes fever, the question specifically points toward the classic "Q fever" association with *Coxiella*. * **Rickettsia prowazekii:** This is the agent of **Epidemic Typhus**, transmitted by the human body louse. It presents with high fever and a characteristic centrifugal rash (spreading from trunk to extremities). * **Bartonella bacilliformis:** This causes **Carrion’s disease**, which has two phases: Oroya fever (acute febrile hemolytic anemia) and Verruga peruana (chronic skin lesions). It is geographically restricted to the Andes mountains. **High-Yield Clinical Pearls for NEET-PG:** * **Coxiella burnetii** is highly resistant to environmental stressors because it forms **spore-like structures**. * It is an **obligate intracellular** organism that multiplies within the acidic environment of phagolysosomes. * **Diagnosis:** Serology is the gold standard (Weil-Felix test is **negative** for Q fever). * **Chronic Q fever:** Most commonly presents as culture-negative endocarditis. * **Treatment:** Doxycycline is the drug of choice.

Q: Undulant fever is caused by which organism?

Brucella melitensis. **Explanation:** **Brucella melitensis (Correct Answer):** Undulant fever is the classic clinical presentation of **Brucellosis**, a zoonotic infection. The term "undulant" refers to the characteristic wave-like pattern of the fever, which rises during the day and falls (subsides) during the night. *Brucella melitensis* (transmitted via goats/sheep) is the most common and virulent species causing human disease. The bacteria are intracellular, surviving within macrophages of the reticuloendothelial system, leading to chronic symptoms like hepatosplenomegaly, lymphadenopathy, and sacroiliitis. **Analysis of Incorrect Options:** * **Salmonella typhi:** Causes **Enteric (Typhoid) fever**, characterized by a "step-ladder" pattern of fever, bradycardia (Faget’s sign), and rose spots. * **Staphylococcus aureus:** Typically causes acute pyogenic infections, abscesses, or toxic shock syndrome. It is associated with a high-grade continuous or remittent fever, but not undulant fever. * **Coxiella burnetti:** The causative agent of **Q fever**. While it is also a zoonosis, it typically presents as an acute flu-like illness, pneumonia, or culture-negative endocarditis. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Consumption of unpasteurized milk/dairy products or direct contact with infected livestock (occupational hazard for vets/farmers). * **Diagnosis:** **Standard Agglutination Test (SAT)** is the screening test (significant titer >1:160). **Rose Bengal Test** is used for rapid screening. * **Culture:** Requires enriched media (e.g., Castaneda’s biphasic medium). * **Treatment:** WHO recommends **Doxycycline + Rifampicin** for 6 weeks.

Q: Which of the following is true about Q fever?

Inhaled aerosols spread the infection.. **Explanation:** **Q Fever** is a zoonotic disease caused by the obligate intracellular bacterium ***Coxiella burnetii***. Unlike other rickettsial diseases, it has unique epidemiological and clinical characteristics. **1. Why Option C is Correct:** The primary mode of transmission for Q fever is the **inhalation of contaminated aerosols** or dust. The bacteria are shed in high concentrations in the birth products (placenta), feces, urine, and milk of infected livestock (sheep, goats, and cattle). *C. burnetii* is highly resistant to environmental stressors and can travel long distances via wind, making inhalation the most common route of human infection. **2. Why the Other Options are Incorrect:** * **Option A:** Unlike most rickettsial infections (like Rocky Mountain Spotted Fever), **Q fever typically does not present with a rash.** The classic triad includes fever, pneumonia, and hepatitis. * **Option B:** Transmission via the human body louse is characteristic of **Epidemic Typhus** (*Rickettsia prowazekii*), not Q fever. * **Option D:** While ticks maintain the cycle in wildlife, **arthropod vectors (like mosquitoes or ticks) play a negligible role** in human transmission. Prevention focuses on pasteurization of milk and dust control in livestock areas rather than mosquito bite prevention. **High-Yield Clinical Pearls for NEET-PG:** * **Organism:** *Coxiella burnetii* (formerly Rickettsial, now classified as Gammaproteobacteria). * **Diagnosis:** Serology (Indirect Immunofluorescence Assay) is the gold standard. * **Chronic Q Fever:** Most commonly manifests as **culture-negative endocarditis**. * **Occupational Hazard:** High risk in veterinarians, farmers, and abattoir workers. * **Treatment:** **Doxycycline** is the drug of choice. * **Biological Warfare:** It is classified as a Category B bioterrorism agent due to its low infectious dose and stability in aerosol form.

Q: Tick is involved in the transmission of all the following diseases except?

Q fever. **Explanation:** The correct answer is **Q fever**. While *Coxiella burnetii* (the causative agent of Q fever) can be found in ticks, human transmission occurs primarily through the **inhalation of contaminated aerosols** or dust from infected livestock (cattle, sheep, goats) [1], [2]. It is considered an occupational hazard for farmers and veterinarians. Unlike the other options, a tick bite is not the primary or common mode of transmission for Q fever [3]. **Analysis of other options:** * **Tick typhus:** Caused by *Rickettsia conorii* (Indian Tick Typhus), it is transmitted via the bite of hard ticks (*Rhipicephalus sanguineus*) [3]. * **Tularaemia:** Caused by *Francisella tularensis*, it is transmitted through various routes, including the bite of infected ticks (*Dermacentor* species), handling infected animal carcasses, or contaminated water. * **Lyme disease:** Caused by *Borrelia burgdorferi*, it is classically transmitted by the bite of *Ixodes* (hard) ticks. **High-Yield Clinical Pearls for NEET-PG:** 1. **Q Fever Unique Features:** It is the only Rickettsial disease that **does not present with a rash** and gives a **negative Weil-Felix reaction** [1]. 2. **Diagnosis:** The most common clinical presentation is an undifferentiated febrile illness, pneumonia, or hepatitis [1]. Chronic Q fever often manifests as culture-negative endocarditis [2]. 3. **Vector Mnemonic:** Remember "Ticks" for **L**yme, **E**hrlichiosis, **B**abesiosis, and **R**ickettsial diseases (except Epidemic/Endemic typhus) [3]. 4. **Infectivity:** *Coxiella burnetii* is highly infectious; a single organism can cause disease, making it a potential bioterrorism agent.

Q: Erythema chronicum migrans is a feature of which disease?

Lyme disease. **Explanation:** **Erythema Chronicum Migrans (ECM)** is the pathognomonic clinical sign of **Lyme disease**, caused by the spirochete *Borrelia burgdorferi*. It represents Stage 1 (Early Localized Disease). The lesion typically appears as a red papule that expands peripherally to form a "bull’s-eye" or target appearance, with central clearing and a distinct red border. **Analysis of Options:** * **Lyme Disease (Correct):** Transmitted by the *Ixodes* tick. ECM appears 3–30 days post-bite. If untreated, the disease progresses to Stage 2 (early disseminated: Bell’s palsy, AV block) and Stage 3 (late: chronic arthritis). * **Leptospirosis:** Caused by *Leptospira interrogans*. It typically presents with high fever, conjunctival suffusion (redness without exudate), and jaundice (Weil’s disease), but not ECM. * **Acute Rheumatic Fever:** Associated with **Erythema Marginatum**, which presents as evanescent, pink, ring-like lesions on the trunk. While the names are similar, the morphology and etiology (Group A Streptococcus) are distinct. * **Pancreatic Adenocarcinoma:** Associated with **Trousseau sign** (migratory thrombophlebitis) or **Erythema Nodosum** (rarely), but has no association with ECM. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Ixodes scapularis* (Deer tick). * **Drug of Choice:** Doxycycline is the first-line treatment for ECM/Early Lyme. In children <8 years or pregnant women, Amoxicillin is preferred. * **Diagnosis:** Primarily clinical when ECM is present. Serology (ELISA followed by Western Blot) is used for later stages. * **Other "Erythemas":** * *Erythema Multiforme:* Target lesions (Stevens-Johnson precursor/HSV). * *Erythema Infectiosum:* Slapped-cheek appearance (Parvovirus B19).

Q: Malignant pustule is a characteristic clinical finding in which of the following conditions?

Anthrax. **Explanation:** **Anthrax (Option D)** is the correct answer. The term **"Malignant Pustule"** is a clinical misnomer used to describe the characteristic skin lesion of **Cutaneous Anthrax**, caused by *Bacillus anthracis*. Despite the name, it is neither malignant nor a true pustule (as it contains no pus). It begins as a painless, pruritic papule that develops into a vesicle and eventually evolves into a **painless, necrotic black eschar** surrounded by significant non-pitting edema. The lesion is typically painless, which is a key diagnostic feature. **Analysis of Incorrect Options:** * **Erysipeloid (Option A):** Caused by *Erysipelothrix rhusiopathiae*, this is an occupational disease of fishermen and butchers. It presents as a painful, reddish-purple swelling (usually on the hands) but does not form a black eschar. * **Glanders (Option B):** Caused by *Burkholderia mallei*, it primarily affects horses. In humans, it causes localized nodules and ulcers with lymphangitis or pneumonia, but not a "malignant pustule." * **Bacillary angiomatosis (Option C):** Caused by *Bartonella henselae* or *B. quintana* in immunocompromised patients (HIV), it presents as vascular, cherry-red papules or nodules that resemble Kaposi sarcoma. **High-Yield Clinical Pearls for NEET-PG:** * **B. anthracis Morphology:** Large, Gram-positive, non-motile, spore-forming bacilli with "Bamboo stick" appearance. * **McFadyean’s Reaction:** Used to visualize the capsule (Methylene blue staining). * **Medusa Head Appearance:** Characteristic colony morphology on blood agar. * **Virulence Factors:** Encoded on plasmids **pXO1** (Toxins: Edema factor, Lethal factor, Protective antigen) and **pXO2** (Polypeptide capsule made of D-glutamic acid). * **Occupational Link:** Known as "Hide porter’s disease" or "Wool sorter’s disease."

Q: All are true about Rickettsia except?

Gram-positive bacillus. **Explanation:** The correct answer is **B (Gram-positive bacillus)** because *Rickettsia* species are actually **Gram-negative coccobacilli**. Although they possess a typical Gram-negative cell wall structure (containing peptidoglycan and lipopolysaccharide), they stain poorly with standard Gram stain and are better visualized using **Giemsa** or **Gimenez** stains. **Analysis of Options:** * **A. Obligate intracellular:** This is true. *Rickettsia* lack certain metabolic pathways (like NAD+ synthesis) and must live inside host eukaryotic cells (specifically endothelial cells) to replicate. * **C. Arthropods are vectors:** This is true. Most rickettsial diseases are transmitted by arthropod vectors such as **ticks** (Rocky Mountain Spotted Fever), **lice** (Epidemic typhus), and **fleas** (Endemic typhus). *Note: Q fever (Coxiella) is a notable exception that does not require a vector.* * **D. Weil-Felix test is diagnostic:** This is true. This heterophile agglutination test uses *Proteus vulgaris* antigens (OX-19, OX-2, OX-K) to detect cross-reacting rickettsial antibodies. While being replaced by IFA (Immunofluorescence assay), it remains a classic diagnostic association for exams. **High-Yield Clinical Pearls for NEET-PG:** * **Target Cell:** *Rickettsia* have a predilection for **vascular endothelial cells**, leading to vasculitis and the characteristic skin rash. * **Weil-Felix Patterns:** * **OX-19 & OX-2 positive:** Spotted fever group. * **OX-19 positive:** Typhus group. * **OX-K positive:** Scrub typhus (*Orientia tsutsugamushi*). * **Negative:** Q fever (*Coxiella burnetii*). * **Drug of Choice:** **Doxycycline** is the gold standard treatment for almost all rickettsial infections.

Question 1

What is the causative agent for Oculoglandular syndrome of Parinaud?

Accepted Answer

Bartonella henselae

Answer

Arachnia propionica

Answer

Bifidobacterium dentium

Answer

Mycobacterium leprae

Question 2

A patient presented with fever, headache, rash, and eschar. You suspect a rickettsial disease. Which of the following is the LEAST likely disease in this case?

Accepted Answer

Endemic typhus

Answer

Indian tick typhus

Answer

Rickettsial pox

Answer

Scrub typhus

Question 3

What is the mode of transmission of Q fever?

Accepted Answer

Inhalation of aerosol

Answer

Bite of infected louse

Answer

Bite of infected tick

Answer

Bite of infected mice

Question 4

Q. Which organism is a cause of fever?

Accepted Answer

Coxiella burnetii

Answer

Ehrlichia sennetsu

Answer

Rickettsia prowazekii

Answer

Bartonella bacilliformis

Question 5

Undulant fever is caused by which organism?

Accepted Answer

Brucella melitensis

Answer

Salmonella typhi

Answer

Staphylococcus aureus

Answer

Coxiella burnetti

Question 6

Which of the following is true about Q fever?

Accepted Answer

Inhaled aerosols spread the infection.

Answer

Rash on palms and soles, headache, and fever are common symptoms.

Answer

Transmitted by the human body louse.

Answer

Mosquito bite prevention is important in its prevention.

Question 7

Tick is involved in the transmission of all the following diseases except?

Accepted Answer

Q fever

Answer

Tick typhus

Answer

Tularaemia

Answer

Lyme disease

Question 8

Erythema chronicum migrans is a feature of which disease?

Accepted Answer

Lyme disease

Answer

Leptospirosis

Answer

Acute rheumatic fever

Answer

Pancreatic Adenocarcinoma

Question 9

Malignant pustule is a characteristic clinical finding in which of the following conditions?

Accepted Answer

Anthrax

Answer

Erysipeloid

Answer

Glanders

Answer

Bacillary angiomatosis

Question 10

All are true about Rickettsia except?

Accepted Answer

Gram-positive bacillus

Answer

Obligate intracellular

Answer

Arthropods are vectors

Answer

Weil-Felix test is diagnostic

Zoonotic Diseases — MCQs

Zoonotic Diseases — MCQs

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