Question
The mode followed in transmission of plague bacillus in the mouth of a rat flea is :
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CUET PG 2026 Agri-Business Management Question Paper (25-Mar-2026) (Shift 2)
The correct answer is
Propagative
Plague Transmission Mode in Rat Fleas
The transmission of the plague bacillus (Yersinia pestis) within the mouth apparatus of a rat flea is best described as propagative. This mode involves the multiplication of the pathogen within the vector.
Understanding Propagative Transmission
Propagative transmission occurs when a pathogen, like the plague bacillus, enters a vector (in this case, a flea) and actively multiplies inside it. The pathogen population increases within the vector, enhancing its ability to be transmitted to a new host.
Application to Plague Bacilli and Fleas
- When a flea ingests blood containing Yersinia pestis, the bacteria multiply within the flea's gut.
- This multiplication leads to the formation of a biofilm that can block the flea's proventriculus (part of the feeding apparatus/mouth).
- When the blocked flea attempts to feed, it regurgitates these multiplying bacteria into the bite wound, transmitting the plague.
- The key aspect here is the significant multiplication of the bacillus within the flea's body, fitting the definition of propagative transmission.
Evaluating Other Transmission Modes
- Cyclopropagative and Cyclodevelopmental: These terms imply both multiplication (propagation) and significant developmental changes or cyclical development of the pathogen within the vector. While Y. pestis multiplies, the primary mode described focuses on this multiplication and subsequent blockage, not complex developmental shifts within the flea relevant to the transmission mechanism itself.
- Vehicle borne: This describes transmission via an inanimate object or intermediate source (like contaminated water or food), which is not applicable to the biological transmission cycle within the flea.
Therefore, the multiplication and colonization of the plague bacillus within the flea vector leading to transmission is termed propagative transmission.
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