Page 1542 - Small Animal Internal Medicine, 6th Edition

1514 PART XIV Infectious Diseases

CHAPTER 98
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Polysystemic Protozoal

Infections

BABESIOSIS America, Africa), B. canis presentii (Israel), B. canis (Europe),
and B. vogeli (Brazil, Thailand, Qatar, United States). Babesia
Etiology and Epidemiology vogeli DNA was amplified from Ctenocephalides felis col-
Babesiosis in dogs is most commonly associated with lected from cats in Jerusalem (Kamani et al., 2018). Whether
Babesia canis, B. rossi, B. vogeli, B. gibsoni, and B. conradae. this just reflects ingestion of B. vogeli in blood by the flea or
These protozoans parasitize red blood cells (RBCs) and are whether the flea is involved in transmission of B. vogeli has
most frequently associated with development of anemia and not been determined.
associated signs. The worldwide distribution, vectors, and After infection with pathogenic strains of B. canis, B.
virulence of Babesia spp. varies. B. rossi is transmitted by vogeli, or B. gibsoni, the incubation period varies from several
Haemaphysalis elliptica (previously leachi) and is the most days to several weeks. The degree of parasitemia varies by
pathogenic; B. canis is transmitted by Dermacentor spp. and the organism studied but can be detected transiently in some
Rhipicephalus sanguineus and is moderately pathogenic; B. dogs as soon as day 1. The organisms replicate intracellularly
vogeli is the least pathogenic and is transmitted by R. sanguin- in RBCs, resulting in intravascular or extravascular hemo-
eus. Babesia vogeli is the most common B. canis subspecies lytic anemia. Immune-mediated reactions against the para-
infecting dogs in the United States. B. gibsoni is transmit- sites or altered self-antigens worsen the hemolytic anemia
ted by Haemaphysalis longicornis and Haemaphysalis bispi- and commonly result in a positive direct Coombs test. Acti-
nosa in some countries; the vector in the United States is vation of macrophages leads to fever and hepatosplenomeg-
unknown, but R. sanguineus has been proposed. Presence aly. Severe hypoxia occurs because of rapid breakdown of
of B. gibsoni DNA in blood of dogs in the United States has RBCs. Disseminated intravascular coagulation occurs in
been associated with a history of a dog bite, especially by some infected dogs during acute infection.
an American Pit Bull Terrier, suggesting that fighting is a The severity of disease depends on the species and strain
route of transmission (Birkenheuer et al., 2003b). Babesia of Babesia and the host’s immune status; chronic, subclinical
conradae induces hemolytic anemia in dogs in southern infection is common. Administration of glucocorticoids or
California; the vector is unknown but is suspected to be splenectomy may reactivate chronic carriers into an acute
R. sanguineous (Kjemtrup et al., 2006). Theleiria annae and disease state. Splenectomized experimentally infected dogs
B. vulpes are Babesia microti-like organisms that has been develop more severe B. vogeli clinical and laboratory mani-
detected in dogs of Europe and North America that may festations of disease (Wang et al., 2018). Presence of co-
be transmitted by Ixodes spp. (Solano-Gallego and Baneth, infections such as Bartonella spp. may increase the pathogenic
2011; Solano-Gallego et al., 2016). potential.
In one survey in North America, Babesia spp. infec-
tions were detected in 29 states and Ontario (Birkenheuer Clinical Features
et al., 2005). Other novel Babesia spp. that genetically vary The clinical features most commonly associated with Babesia
considerably from other B. canis or B. gibsoni isolates have spp. infecting dogs worldwide have been reviewed (Solano-
been described in the United States; however, the prevalence Gallego and Baneth, 2011). In the United States, subclini-
rate for these infections is unknown (Meinkoth et al., 2000; cal Babesia spp. infections are most common. Peracute or
Birkenheuer et al., 2004a). Babesia spp. can also be transmit- acute Babesia spp. infections result in anemia and fever,
ted by blood transfusions so screening is recommended for leading to pale mucous membranes, tachycardia, tachypnea,
blood donors (Wardrop et al., 2016). depression, anorexia, and weakness. Icterus, petechiae, and
Babesiosis in cats appears to be less common than in dogs. hepatosplenomegaly are present in some dogs depending
Cats have been shown to be infected by B. cati (India), B. felis on the stage of infection and the presence of disseminated
(Africa, southern Asia, Europe; Qatar), B. herpailuri (South intravascular coagulation. Severe anemia, disseminated

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