Anaplasma ovis in Idaho sheep

Area of Science:

• Veterinary Medicine
• Parasitology
• Microbiology

Background:

• Anaplasmosis is a significant disease affecting livestock.
• Accurate diagnosis of Anaplasma ovis infections, particularly carrier states in sheep, is crucial for disease control.

Purpose of the Study:

• To investigate the transmission and causative agent of anaplasmosis in sheep.
• To evaluate the diagnostic efficacy of the rapid card agglutination test for detecting anaplasmosis carrier status in sheep.

Main Methods:

• Blood from anaplasmosis-positive sheep was inoculated into intact sheep and splenectomized calves.
• Recipient animals were monitored for clinical signs, parasitemia, and complement-fixation (CF) test results.
• Subinoculation studies were performed, and electron microscopy was used to identify the organism.

Main Results:

• Inoculated intact sheep developed positive CF tests and parasitemia.
• Splenectomized calves did not show initial signs but became ill after challenge with Anaplasma marginale.
• Subinoculation into splenectomized sheep resulted in clinical anaplasmosis and positive CF tests.
• The rapid card agglutination test was positive in only one sheep, indicating low diagnostic sensitivity for carrier status.

Conclusions:

• Anaplasma ovis was identified as the causative agent of clinical anaplasmosis in the experimentally infected sheep.
• The rapid card agglutination test is not a reliable diagnostic tool for identifying anaplasmosis carrier sheep.