Question

Given below are two statements:
Statement I: Theileria equi is more pathogenic than Babesia caballi in equines
Statement II: Besides high rise in temperature and anaemia, gastroenteritis, nervous signs and posterior paresis are commonly seen in T. equi infected horses
In light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

Remember that *Theileria equi* undergoes a tissue phase (schizogony in lymphocytes) while *Babesia caballi* resides strictly inside erythrocytes. This extra tissue phase makes *T. equi* far more destructive and systemic in its clinical manifestations.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Equine piroplasmosis is a significant tick-borne protozoan disease of equids caused by Theileria equi (formerly Babesia equi) and Babesia caballi.
While both parasites target erythrocytes, they differ in their life cycles, pathogenicity, clinical severity, and responsiveness to treatment.

Step 2: Detailed Explanation:
Let us evaluate both statements:
1. Statement I: Theileria equi is more pathogenic than Babesia caballi in equines
This statement is correct.
Theileria equi is significantly more pathogenic than Babesia caballi.
This increased virulence is due to its life cycle: T. equi undergoes an initial pre-erythrocytic schizogony in host lymphocytes before invading red blood cells.
This causes systemic lymphoid destruction in addition to hemolysis.
Furthermore, T. equi infections are harder to clear and often lead to lifelong carrier states, whereas B. caballi infections are typically milder and easier to eliminate using babesicides like imidocarb dipropionate.
Therefore, Statement I is true.
2. Statement II: Besides high rise in temperature and anaemia, gastroenteritis, nervous signs and posterior paresis are commonly seen in T. equi infected horses
This statement is correct.
The clinical presentation of acute T. equi infection is characterized by high fever, hemolytic anemia, icterus, and hemoglobinuria.
In addition to these signs, severe systemic disease can lead to gastrointestinal disturbances (colic, gastroenteritis) and neurological manifestations.
Neurological signs, including ataxia, weakness in the hindquarters, and posterior paresis, occur due to capillary plugging, hypoxia, and inflammatory changes in the central nervous system.
Therefore, Statement II is true.

Step 3: Final Answer:
Both Statement I and Statement II are accurate representations of equine piroplasmosis pathogenesis and clinical science.
Therefore, the correct answer is option (A).