Page 1500 - Small Animal Internal Medicine, 6th Edition

1472 PART XIV Infectious Diseases

Anaplasma phagocytophilum
PCR and serology results
VetBooks.ir 4
Number of positive cats 2
3

1

0
0 1 2 3 4 5 6 7 8 9 1013
Week of study

Ap PCR Ap AB

FIG 95.3
Serologic and polymerase chain reaction assay test results FIG 95.4
over time in cats infected with Anaplasma phagocytophilum Bilateral anterior uveitis in a dog consistent with E. canis–
by exposure to wild-caught Ixodes scapularis ticks. The four associated inflammation. (Courtesy Dr. Cynthia Powell,
cats were exposed to wild-caught Ixodes scapularis ticks on Colorado State University.)
Day 0 of the study. AB, Antibodies detected by the SNAP
4DX; Ap, A. phagocytophilum; PCR, polymerase chain
reaction.
infection in cats, acaricidal products approved for use on cats
should be used. As for dogs, cats used for blood donors that
seronegative when first assessed serologically, but all proven reside in endemic areas should be screened for A. phagocy-
cases to date have ultimately seroconverted. Anaplasma tophilum infections by serology and PCR assay; the ACVIM
phagocytophilum DNA can be amplified from blood before optimally recommends using only cats that are negative in
development of detectable serum antibodies, so a single both tests (Wardrop et al., 2016). However, if PCR assay
negative antibody result in an acutely infected cat does not cannot be performed, the minimal standard recommended
exclude infection. Therefore cats with suspected anaplasmo- was to use only seronegative cats as donors.
sis may need convalescent serum samples to prove infection.
Alternately, antibody testing could be combined with PCR
testing of whole blood in acute cases (Lappin et al., 2015). In CANINE THROMBOCYTOTROPIC
a recent study of cats (n = 4) exposed to wild-caught Ixodes ANAPLASMOSIS
scapularis ticks from Rhode Island, all cats developed anti-
bodies that were detectable in a commercially available kit Etiology and Epidemiology
labeled for use with canine serum (SNAP 4DX, IDEXX) and Anaplasma platys forms morulae in circulating platelets, and
became PCR-positive (Lappin et al., 2015). However, none this syndrome has been referred to as canine infectious cyclic
of the cats developed measurable clinical signs of disease or thrombocytopenia. Infected dogs have been detected primar-
complete blood cell abnormalities (Fig. 95.3). ily in the south and southeastern United States, Australia,
Africa, Caribbean Islands, the Middle East, South America,
Treatment and parts of Europe. Inclusions morphologically similar to
Supportive care should be administered as needed. Several A. platys have been detected in one cat in Brazil, and other
antibiotics have been administered to naturally infected cats, cats have been positive for A. platys DNA in blood (Hegarty
but most cats became clinically normal within 24 to 48 hours et al., 2015; Lima et al., 2010; Qurollo et al., 2014; Zobba
after initiation of tetracycline or doxycycline administration et al., 2015). However, whether this agent is associated with
and recurrence was not reported (Adaszek et al., 2013; Bjo- significant disease in cats is unknown. Anaplasma platys
ersdorff et al., 1999; Lappin et al., 2004; Savidge et al., 2016). DNA has been amplified from ticks, particularly Rhipicepha-
Although clinically normal, two cats were still PCR-positive lus spp. (Foongladda et al., 2011; Geurden et al., 2018), and
17 days and 90 days after treatment (of 21-30 days’ duration), trans-stadial transmission has been documented in this tick
respectively, which suggests that treatment with tetracyclines (Aktas and Ozubek, 2018). High co-infection rates with E.
for 21 to 30 days may be inadequate for eliminating the canis also support the hypothesis that Rhipicephalus spp.
organism from the body (Lappin et al., 2004). ticks are the vectors of A. platys (Yabsley et al., 2008).
After intravenous inoculation, the incubation period is 8
Zoonotic Aspects and Prevention to 15 days. Although cyclic thrombocytopenia and parasit-
See the section on canine granulocytic anaplasmosis for a dis- emia can occur at 10- to 14-day intervals, organism numbers
cussion of zoonotic aspects. To prevent A. phagocytophilum and severity of thrombocytopenia may lessen over time.