MCQ Detailed View

The correct answer is McFadyean reaction.

Anthrax is a serious infectious disease caused by Bacillus anthracis, a Gram-positive, spore-forming bacterium. It affects livestock such as cattle, sheep, and goats, and it can also infect humans. Rapid diagnosis is critical to control outbreaks, especially in farm animals.

The McFadyean reaction is the classical diagnostic method for anthrax. It was developed in the early 20th century by Scottish pathologist John McFadyean. In this method, a blood smear from a suspected anthrax-infected animal is stained with polychrome methylene blue. When observed under the microscope, the Bacillus anthracis organisms appear with a distinctive blue bacillus surrounded by a pinkish or purplish capsule. This unique capsule staining reaction is considered a confirmatory test for anthrax.

Let’s look at why the other options are incorrect:

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  Spore staining: While Bacillus anthracis does form spores, spore staining is not the routine diagnostic method in cattle, since spores may not always be present in fresh blood samples.

  
  


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  Quellung reaction: This test detects the capsule of Streptococcus pneumoniae and is unrelated to anthrax.

  
  


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  None of the above: Incorrect, since the McFadyean reaction is a well-established diagnostic method.

  
  

The importance of diagnosing anthrax quickly cannot be overstated. Anthrax outbreaks in cattle can cause sudden death in herds, economic losses, and risk of transmission to humans. Identifying the disease early through the McFadyean reaction allows for immediate control measures such as vaccination of surrounding livestock and safe disposal of infected carcasses.

🔑 Key Facts:

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  Anthrax is caused by Bacillus anthracis.

  
  


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  McFadyean reaction uses polychrome methylene blue to reveal the bacterial capsule.

  
  


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  It remains one of the fastest confirmatory tests for anthrax in veterinary practice.

  
  


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  Preventive measures include vaccination of livestock and proper handling of infected material.

  
  

👉 Final Answer: Anthrax in cattle can be diagnosed using the McFadyean reaction.