Which of the following members of the microbial world is responsible for causing coughing, dull hair coats, and dyspnea in livestock?

• A. Aspergillus fumigatus
• B. Bacillus anthracis
• C. Streptococcus pneumoniae
• D. Nematodes (roundworms)

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the symptoms described—coughing, dull hair coats, and dyspnea (difficulty breathing)—and recognize that these are clinical signs often associated with respiratory or systemic infections in livestock.
2. Step 2: Review the characteristics of the listed microbial agents: Aspergillus fumigatus (a fungus), Bacillus anthracis (a bacterium causing anthrax), and Streptococcus pneumoniae (a bacterium causing pneumonia), and consider whether these typically cause the described symptoms in livestock.
3. Step 3: Recognize that nematodes (roundworms) are parasitic worms, not microbes like bacteria or fungi, and that certain nematodes infect the respiratory tract of livestock, causing symptoms such as coughing and dyspnea due to lung damage.
4. Step 4: Connect the clinical signs to the life cycle and pathology of nematodes, which can cause respiratory distress and systemic effects like dull hair coats due to chronic infection and poor health.
5. Step 5: Conclude that among the options, nematodes (roundworms) are the causative agents responsible for the symptoms described, highlighting the importance of considering parasitic infections alongside microbial pathogens in veterinary diagnosis.