Veterinary Medicine - April 2008 - (Page 220)

Canine anaplasmosis PEER-REVIEWED ease or that do not rapidly respond to doxycycline therapy should be tested for other tick-borne diseases. SUMMARY Anaplasmosis causes one of two clinical syndromes: Fever, lethargy, polyarthritis, and, less often, gastrointestinal, respiratory, or neurologic signs, which are associated with A. phagocytophilum infection. Signs due to thrombocytopenia are associated with A. platys infection. rapidly resolve in most cases shortly after doxycycline therapy is initiated. Dogs infected with A. platys experience a cyclic thrombocytopenia. Clinical disease is often mild in naturally infected dogs, but some animals may have clinical evidence of bleeding (epistaxis or petechiation), particularly during the initial bacteremic phase when platelet counts may be reduced to < 20,000 cells/ l. Platelet counts are less dramatically affected in subsequent cycles of bacteremia and Seropositive dogs that appear healthy should be monitored for clinical disease. Since the two organisms share the same tick vector, the diseases have a similar geographic distribution. Anaplasma phagocytophilum infection is an emerging tick-borne infection in dogs, endemic to several areas of the United States and expanding in distribution. The organism typically causes acute clinical disease similar to Lyme disease, resulting in a suppurative polyarthritis. In addition to causing clinical disease, A. phagocytophilum may persistently infect dogs, causing a subclinical carrier state associated with positive serologic test results in a healthy dog. These dogs should be monitored for evidence of clinical disease because there may be potential for future clinical manifestations, particularly if they become coinfected with other tick-borne agents or become immunosuppressed. Since animals can have subclinical infections, it is important to recognize that clinically ill animals may have positive test results for A. phagocytophilum but be experiencing the clinical manifestations of an unrelated disease process. Therefore, seropositivity alone does not indicate a causal relationship to the clinical disease. Clinical signs must be consistent with those found in animals with anaplasmosis and should clinical signs become milder or unapparent. As with A. phagocytophilum infection, animals with clinical disease resulting from A. platys infection respond rapidly to treatment with doxycycline. Finally, A. phagocytophilum is a zoonotic pathogen. However, direct transmission from animals to people or animal to animal is highly unlikely and, to our knowledge, has never been documented. Even so, alert owners of pets with known exposure to A. phagocytophilum to potential human exposure from infected ticks in the environment. Editors’ note: IDEXX Laboratories has sponsored presentations by both Dr. Alleman and Dr. Wamsley at various continuing education symposia. REFERENCES 1. Dumler JS, Barbet AF, Bekker CP, et al. Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales: uni cation of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia and Ehrlichia with Neorickettsia, descriptions of six new species combinations and designation of Ehrlichia equi and ‘HGE agent’ as subjective synonyms of Ehrlichia phagocytophila. Int J Sys Evol Microbiol 2001;51(Pt 6):2145–2165. 2. Greig B, Asanovich KM, Armstrong PJ, et al. Geographic, clinical, serologic, and molecular evidence of granulocytic ehrlichiosis, a likely zoonotic disease, in Minnesota and Wisconsin dogs. J Clin Microbiol 1996;34(1):44-48. 3. Bakken JS, Dumler JS, Chen SM, et al. Human granulocytic ehrlichiosis in the upper Midwest United States. A new species emerging? JAMA 1994;272(3):212-218. 4. des Vignes F, Piesman J, Heffernan R, et al. Effect of tick removal on transmission of Borrelia burgdorferi and Ehrlichia phagocytophila by Ixodes scapularis nymphs. J Infect Dis 2001;183(5):773-778. 5. Egenvall A, Bjöersdorff A, Lilliehöök I, et al. Early manifestations of granulocytic ehrlichiosis in dogs inoculated experimentally with a Swedish Ehrlichia species isolate. Vet Rec 1998;143(15):412-417. 6. Egenvall A, Lilliehöök I, Bjöersdorff A, et al. Detection of granulocytic Ehrlichia species DNA by PCR in persistently infected dogs. Vet Rec 2000;146(7):186-190. 7. Alleman AR, Chandrashekar R, Beall M, et al. Experimental inoculation of dogs with a human isolate (Ny18) of Anaplasma phagocytophilum and demonstration of persistent infection following doxycycline therapy (abst). J Vet Intern Med 2006;20:763. 8. Egenvall AE, Hedhammar AA, Bjöersdorff AI. Clinical features and serology of 14 dogs affected by granulocytic ehrlichiosis in Sweden. Vet Rec 1997;140(9):222-226. 9. Beall MJ, Chandrashekar R, Eberts MD, et al. Serological and molecular prevalence of Borrelia burgdorferi, Anaplasma phagocytophilum, and Ehrlichia species in dogs from Minnesota. Vector Borne Zoonotic Dis 2008 Feb 27 [Epub ahead of print]. 10. Bakken JS, Goellner P, Van Etten M, et al. Seroprevalence of human granulocytic ehrlichiosis among permanent residents of northwestern Wisconsin. Clin Infect Dis 1998;27(6):1491-1496. 11. Lilliehöök I, Egenvall A, Twedten HW. Hematopathology in dogs experimentally infected with a Swedish granulocytic Ehrlichia species. Vet Clin Pathol 1998;27(4):116-122. 12. Greig B, Armstrong PJ. Canine granulocytotropic anaplasmosis (A. phagocytophilum infection). In: Greene CE, ed. Infectious diseases of the dog and cat. 3rd ed. St. Louis, Mo: Saunders, 2006;219-224. 13. Dumler JS, Asanovich KM, Bakken JS, et al. Serologic crossreactions among Ehrlichia equi, Ehrlichia phagocytophila, and human granulocytic Ehrlichia. J Clin Microbiol 1995;33(5):1098-1103. 14. Chandrashekar R, Mainville C, Daniluk D, et al. Performance of an in-clinic test SNAP 4Dx, for the detection of antibodies to canine granulocytic infection, Anaplasma phagocytophilum (abst). J Vet Intern Med 2007;21:626. 15. Alleman AR, Wamsley HL, Abbott J, et al. Experimental Anaplasma phagocytophilum infection of dogs by intravenous inoculation of human and canine isolates and treatment with doxycycline (abst). Vet Pathol 2007;44:19. 16. Breitschwerdt EB, Hegarty BC, Hancock SI. Sequential evaluation of dogs naturally infected with Ehrlichia canis, Ehrlichia chaffeensis, Ehrlichia equi, Ehrlichia ewingii, or Bartonella vinsonii. J Clin Microbiol 1998;36(9):2645-2651. 17. Maurin M, Bakken JS, Dumler JS. Antibiotic susceptibilities of Anaplasma (Ehrlichia) phagocytophilum strains from various geographic areas in the United States. Antimicrob Agents Chemother 2003;47(1):413-415. 18. Harvey JW, Simpson CF, Gaskin JM. Cyclic thrombocytopenia induced by a Rickettsia-like agent in dogs. J Infect Dis 1978;137(2):182-188. 19. Inokuma H, Raoult D, Brouqui P. Detection of Ehrlichia platys DNA in brown dog ticks (Rhipicephalus sanguineous) in Okinawa Island, Japan. J Clin Microbiol 2000;38(11):4219-4221. 20. Parola P, Cornet JP, Sanogo YO, et al. Detection of Ehrlichia spp., Anaplasma spp., Rickettsia spp., and other eubacteria in ticks from the Thai-Myanmar border and Vietnam. J Clin Microbiol 2003;41(4):1600-1608. 21. Santarém VA, Laposy CB, Farias MR. Ehrlichia platys-like inclusions and morulae in platelets of a cat (abst). Brazilian J Vet Sci 2000;7:130. 22. Du Plessis L, Reyers F, Stevens K. Morphological evidence for infection of impala, Aepyceros melampus, platelets by a rickettsialike organism. Onderstepoort J Vet Res 1997;64(4):317-318. 23. Hoskins JD, Breitschwerdt EB, Gaunt SD, et al. Antibodies to Ehrlichia canis, Ehrlichia platys, and spotted fever group rickettsiae in Louisiana dogs. J Vet Intern Med 1988;2(2):55-59. EXTRAS See for client handouts on removing ticks in cats and dogs. 220 April 2008 VETERINARY MEDICINE http://www.vetstreamfelis.com/ACI/April08/VMD1/ENGLISHFactSheet038.asp http://www.vetstreamcanis.com/ACI/April08/VMD1/FactSheet075.asp

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Veterinary Medicine - April 2008 Contents Letters Leading Off The Veterinary Medicine Interview: Dr. Barrak Pressler Idea Exchange Help! My Dog Licks Everything An Update on Anaplasmosis in Dogs CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - April 2008

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