Question

Arrange the following Eimeria spp. on the basis of their pathogenicity (starting from most pathogenic to least pathogenic)
(A) Eimeria acervulina
(B) Eimeria brunetii
(C) Eimeria mitis
(D) Eimeria tenella
Choose the correct answer from the options given below:

• A. (B), (D), (C), (A).
• B. (D), (B), (A), (C).
• C. (A), (B), (C), (D).
• D. (D), (A), (C), (B).

Hint:

Remember that E. tenella (cecal coccidiosis) is always the most pathogenic and deadly species in chickens (D is first), while E. mitis and E. praecox are the least pathogenic (C is last).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Coccidiosis in poultry is caused by different species of the genus Eimeria.
These species parasitize different portions of the avian intestinal tract and vary significantly in their virulence, lesion severity, and overall pathogenicity.
Detailed Explanation:
Let us compare the relative pathogenicity of the given Eimeria species in chickens:
- (D) Eimeria tenella: This is the most highly pathogenic and deadly species. It parasitizes the ceca, causing severe, hemorrhagic, and often fatal cecal coccidiosis.
- (B) Eimeria brunetii: Highly pathogenic. It infects the lower small intestine, rectum, and cloaca, causing severe mucosal necrosis and coagulative enteritis.
- (A) Eimeria acervulina: Moderately pathogenic. It primarily infects the duodenum and upper small intestine, causing characteristic white ladder-like lesions and weight loss, but has lower mortality compared to E. tenella and E. brunetii.
- (C) Eimeria mitis: Mildly pathogenic. It causes minimal mucosal damage and is generally considered to have the lowest pathogenicity among the listed species.
Arranging these from most pathogenic to least pathogenic yields:
\[ \text{(D) \textit{E. tenella}} \rightarrow \text{(B) \textit{E. brunetii}} \rightarrow \text{(A) \textit{E. acervulina}} \rightarrow \text{(C) \textit{E. mitis}} \]

Step 2: Final Answer:
The correct descending order corresponds to Option (B).