Babesia is another name for piroplasm, one of the protozoan parasites belonging to the order Haemosporidia. These are generally relatively large parasites within the red blood cells and are pear-shaped, round or oval. Multiplication is by division into 2 or by budding. Infected cells frequently have 2 pyriform parasites joined at their pointed ends. Sexual multiplication takes place in the tick.
Nearly all the domestic mammals suffer from infection with some species of Babesia; sometimes more than 1 species may be present. The general symptoms are the appearance of fever in 8 to 10 days after infection, accompanied by haemoglobinuria, icterus; unless treated, 25 to 100 per cent of the cases are fatal. Red blood cells may be reduced in number by two-thirds. Convalescence is slow and animals may remain ‘salted’ for 3 to 8 years.
Development occurs in certain ticks which transmit the agent to their offspring.
The various species are similar, but are specific to their various hosts. The ticks should probably be regarded as the true or definite hosts, while the mammal is the intermediate host.
Babesia felis is a (rare) cause of lethargy, inappetence and anaemia, and occasionally jaundice and death.
Ovine babesiosis may be due to at least 3 species of Babesia. There is a relatively large form, Babesia motasi, which is comparable to B. bigemina of cattle, and which produces a disease, often severe, with high temperatures, much blood-cell destruction, icterus, and haemoglobinuria. This is the ‘carceag’ of Eastern and Southern Europe. The 2nd parasite, of intermediate size and corresponding to Babesia bovis of cattle, is Babesia ovis. It produces a much milder disease with fever, jaundice, and anaemia, but recoveries generally occur. The small species is Theileria ovis, which appears to be similar to Theileria mutans of cattle and is relatively harmless to its host.
Babesia motasi, Babesia ovis, and Theileria ovis are all transmitted by Rhipicephalus bursa.
Animals recovered from Theileria ovis infection apparently develop a permanent immunity to it. The disease occurs in Europe, Africa, Asia, and North America.
In acute cases the temperature may rise to 41.5°C (107°F), rumination ceases, there is paralysis of the hindquarters, the urine is brown, and death occurs in about a week. In benign cases there may only be a slight fever for a few days with anaemia.
A theileriosis, caused by Theileria birci, has been described from sheep in Africa and Europe. It causes an emaciation and small haemorrhages in the conjunctiva.