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Parasites of red blood cells: Babesia and Mycoplasma (Proceedings)

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Nov 01, 2010

BABESIA

Overview

     • Protozoal disease (genus: Babesia) of dogs and cats where merozoites (piroplasms) infect RBCs

     • Degree of illness is usually dependent on the severity and rate of anemia development.

     • Anemia mainly as a result of immune mediated hemolysis but also due to direct piroplasm damage to RBCs.

Etiology/Pathophysiology

     • Infection (by tick transmission, transplacental, blood transfusion, or, in the case of B. gibsoni, by bite wounds presumably by blood from infected dog entering a bite wound.) followed by 2 week incubation period during which piroplasms infect and multiply in RBCs, resulting in RBC damage mainly from immune mediated processes but also direct RBC lysis.

     • In the case of Rhipicephalus sanguineus tick, larvae, adults and nymphs can all transmit infection; ticks need to be attached for several days; in ticks, the parasite reproduces by sexual reproduction; ticks can be infected by eating a blood meal or by transovarial means.

Dogs

     • Large (4 – 7 µm): B. canis distributed worldwide; 3 sub-species based on biologic, genetic and geographic distribution:

           o B. canis vogeli – USA, Africa, Asia, Australia. Transmitted by R. sanguineus ticks, so disease found in southeastern, southern states, and California.

           o B. canis rossi - Africa (most virulent sub-species)

           o B. canis canis – Europe, areas of Asia

           o Small (2 – 5 µm): several genetically distinct sub-species:

           o B. gibsoni – world-wide distribution (especially Asia) including the USA.

           o B. conradae – (California – genetically distinct from B. gibsoni) – infects only dogs and only reported in California.

           o B. microti-like – Spain, but recently reported in a Pit Bull terrier dog from Mississippi (unknown if this is a local case or imported).

           o Theileria annae – (Spanish dog piroplasm). Reported in Spain and Europe.

Cats

     • Small (2 – 5 µm) – B. felis reported in Africa.

Signalment/History

     • History of tick attachment.

     • History of recent dog bite wound may be a risk for B. gibsoni infection.

     • Any age or breed of dog can be infected.

     • Severity of disease – depends on the strain of the organism, and the age and breed of the animal.

     • B. canis infections - more prevalent in Greyhounds (USA).

     • B. gibsoni infections - more prevalent in American Pit Bull, Staffordshire, and Tosa Inu breeds.