Babesia Divergens

Synonym: Piroplasma divergens.

Hosts: Cattle, rarely man.

Location: Erythrocytes.

Geographic Distribution: Western and central Europe.

Prevalence: This is probably the commonest if not the only species of Babesia in western and central Europe, but further investigation is needed to confirm this statement. B. divergens is now definitely known to occur in Yugoslavia, Austria and England (Simitch, Petrovitch and Rakovec, 1955; Davies, Joyner and Kendall, 1958).

Morphology: This species is smaller than B. bovis. The trophozoites usually occur as paired, club-shaped organisms about 1.5 by 0.4 u; the angle between the members of the pair is relatively large, so that they diverge more from each other than the trophozoites of B. bovis; in addition, they tend to lie along the circumference of the host erythrocyte (the so-called accole position). Other trophozoites are stouter and piriform (about 2 by 1 u), circular (about 1.5 u in diameter), or vacuolated and circular (up to 2 u in diameter) (Davies, Joyner and Kendall, 1958).

Life Cycle: Same as that of B. bovis. The vector tick is Ixodes ricinus.

Pathogenesis: Same as for B. bovis.

Immunity: Same as for B. bovis.

Diagnosis: Same as for B. bovis.

Treatment: Same as for B. bovis. Amicarbalide was found by Beveridge, Thwaite and Shepherd (1960) and Lucas (1960) to be effective against B. divergens. The dosage is about 5 to 20 mg per kg subcutaneously or intramuscularly.

Remarks: Skrabalo and Deanovic (1957) described a fatal human case of babesiosis accompanied by blackwater due to B. divergens in Yugoslavia. The patient had had a splenectomy 11 years before and lived on a tick-infested farm where the cattle had babesiosis.

Garnham and Bray (1959) infected 2 splenectomized chimpanzees and a splenectomized rhesus monkey with the British strain of B. divergens described by Davies, Joyner and Kendall (1958), but were unable to infect 2 splenectomized rabbits. The parasites in the rhesus monkey had the typical accole form, but those in the chimpanzees did not. Garnham and Bray suggested that latent babesiosis might exist in man on a large scale in rural populations in infected regions.