Page 1543 - Small Animal Internal Medicine, 6th Edition

CHAPTER 98 Polysystemic Protozoal Infections 1515

intravascular coagulation, metabolic acidosis, and renal paraoxonase-1 concentrations were decreased when com-
disease are most common during acute infection and are pared with healthy client-owned cats (Vilhena et al., 2017).
VetBooks.ir generally most severe with B. rossi infections in South Africa. These types of assays may prove to be of clinical benefit in
the future.
Tissue hypoxemia is important in the pathogenesis of disease
in severely affected dogs. The main differential diagnoses
for acute babesiosis is primary immune-mediated hemolytic Treatment
anemia and immune-mediated thrombocytopenia. Chroni- Supportive care, including blood transfusions, sodium bicar-
cally infected dogs commonly have weight loss and anorexia. bonate therapy for acidosis, and fluid therapy, should be
Ascites, gastrointestinal signs, central nervous system (CNS) administered as indicated. A number of drugs, including
disease, edema, and clinical evidence of cardiopulmonary diminazene aceturate, phenamidine, pentamidine isethion-
disease occur in some dogs with atypical infection. Babesia ate, parvaquone, atovaquone, and niridazole, have also been
canis or B. gibsoni DNA has been amplified from the blood or used in an attempt to treat different Babesia spp. infections.
effusion (one dog; B. gibsoni) of some dogs with pericardial In the United States, if clinical disease associated with B.
effusion (Tabar et al., 2018). vogeli is suspected, imidocarb diproprionate may be effective
when administered (5-6.6 mg/kg subcutaneously or intra-
Diagnosis muscularly) twice, 14 days apart or (7.5 mg/kg subcutane-
Spherocytic regenerative anemia, hyperbilirubinemia, bili- ously or intramuscularly) once. Adverse effects include
rubinuria, hemoglobinuria, thrombocytopenia, metabolic transient salivation, diarrhea, dyspnea, lacrimation, necrosis
acidosis, azotemia, polyclonal gammopathy, proteinuria, and at the injection site, and depression.
cylindruria are common in dogs infected with pathogenic Imidocarb as a single agent is not as effective for the
Babesia spp. Presence of the organism in RBCs detected by treatment of B. gibsoni infection. In the United States, if
Wright or Giemsa stains on thin blood smears (see Chapter clinical disease associated with B. gibsoni or B. conradae
91) can be used to support the diagnosis, but parasitemia is suspected, azithromycin (10 mg/kg by mouth [PO] q24h
can be intermittent, giving falsely negative results; capillary for at least 10 days) and atovaquone (13.3 mg/kg PO q8h
blood is the preferred source for blood smear evaluation. for at least 10 days) is currently recommended. However,
In the United States, B. vogeli is typically found as single or this combination does not always result in elimination of
paired, piriform bodies measuring 2.5 × 4.5 µm, B. gibsoni infection, and B. gibsoni resistance to these drugs has been
is typically found as single annular bodies (more than one recognized (Birkenheuer et al., 2004b; Di Cicco et al., 2012;
per cell are common) measuring 1.0 × 3.0 µm, and B. conra- Jefferies et al., 2007). In Asia the combination of clindamy-
dae is typically found as ring or ameboid bodies measuring cin, diminazene, and imidocarb was used successfully for the
0.3 × 3 µm. treatment of B. gibsoni infection in 11 of 13 dogs (Lin et al.,
Serologic and polymerase chain reaction (PCR) assays are 2012) and should be considered for atovaquone resistant
usually used in the diagnosis of babesiosis. Indirect fluores- strains (Baneth, 2018). Oral administration of a doxycycline-
cent antibody tests for B. vogeli and B. gibsoni are available enrofloxacin-metronidazole combination led to clinical
commercially in the United States. However, serologic cross- improvement in 85.7% of dogs infected with Asian strains
reactivity can exist, so antibody test results cannot be used to of B. gibsoni (Lin and Huang, 2010). Although success rates
determine the infective species definitively. Demonstration with this protocol have not been reported with North Ameri-
of increasing titers over 2 to 3 weeks is consistent with recent can strains, it could be considered for use with infected dogs
or active infection. No standardization between laboratories if atovaquone or diminazene are not immediately available
exists, so suggested positive cutoff titers vary. False-negative or is ineffective. Because no drugs are known to eliminate
serologic test results can occur in some dogs, particularly in infection consistently, treatment of healthy, seropositive dogs
those with peracute disease or concurrent immunosuppres- is unlikely to be of benefit.
sion. Many dogs are seropositive but clinically normal, so
serology alone cannot be used to make a definitive diagnosis Zoonotic Aspects and Prevention
of clinical babesiosis. No evidence currently exists to suggest that Babesia spp.
Positive results in PCR assays performed on blood prove infecting dogs and cats can cause human disease. However,
current infection and can be used to differentiate amongst some Babesia spp. that infect people (B. microti) are geneti-
the Babesia spp. However, as subclinical carriers exist, posi- cally similar to those infecting dogs, so ticks should be con-
tive results do not always correlate with clinical illness. In trolled if possible. Minimal cross-protection exists between
addition, not all PCR assays performed in commercial labo- species; a dog that has recovered from babesiosis may still
ratories are equivalent. become ill if infected with another species. Administra-
The acute phase proteins like serum amyloid A, hap- tion of immunosuppressive drugs or splenectomy should
toglobin, and paraoxonase-1 have been studied in small be avoided in previously infected dogs. Dog bites should be
numbers of animals in an attempt to differentiate subclinical avoided. Vaccines against some Babesia spp. are available in
Babesia spp. carriers from those with clinical manifestations some countries but not the United States. For blood donor
of disease. In naturally infected cats with B. vogeli infec- programs, high-risk breeds (American Pit Bull Terrier; Grey-
tions, serum haptoglobin concentrations were increased and hounds) or dogs from endemic areas should be screened for