Which pathogen is responsible for East Coast fever?

• A. Ehrlichia ruminantium
• B. Theileria parva
• C. Babesia bigemina
• D. Anaplasma marginale

Answer: (B)

East Coast fever is caused by a protozoan parasite, Theileria parva, transmitted by the tick Rhipicephalus appendiculatus. The parasite’s life cycle starts when tick bites introduce sporozoites that invade bovine lymphocytes and transform them into schizonts, prompting lymphocyte proliferation. Merozoites released from these cells then infect red blood cells, forming piroplasms. This leads to high fever, swollen lymph nodes, edema, and often death in susceptible cattle, particularly in eastern Africa. The other microbes listed cause different diseases: Ehrlichia ruminantium causes heartwater, Babesia bigemina causes babesiosis, and Anaplasma marginale causes anaplasmosis. They are distinct pathogens with different disease pictures and vectors.