Michael R. Lappin, DVM, PhD, DACVIM
The large and small forms of Haemobartonella felis are gram-negative, epicellular parasite of feline erythrocytes. The organisms are classified as mycoplasmas. The new name for the large form (Ohio isolate) is Mycoplasma haemofelis. The proposed name for the small form (California isolate) Candidatus"Mycoplasma haemominutum". In at least two studies of experimentally infected cats, M. haemofelis is apparently more pathogenic than M. haemominutum; all M. haemofelis inoculated cats became clinical ill whereas M. haemominutum inoculated cats were subclinically infected. Cats with chronic M. haemominutum infection had more severe anemia and longer duration of anemia when experimentally infected with M. haemofelis when compared to cats infected with M. haemofelis alone.
It was recently shown that naturally infected cats and fleas can be infected by M. haemofelis and M. haemominutum (Lappin et al, 2003). In addition, cats with experimentally induced M. haemominutum infections transfer the infection mechanically to fleas (Woods et al, 2003). We have just shown fleas to be competent vectors for M. haemofelis(unpublished data). Hemoplasmas have been transmitted experimentally by IV, IP, and oral inoculation of blood. Clinically ill queens can infect kittens; whether transmission occurs in utero, during parturition, or from nursing has not been determined. Transmission by biting has been hypothesized. Red blood cell destruction is due primarily to immune-mediated events; direct injury to red blood cells induced by the organism is minimal.
Clinical signs of disease depend on the degree of anemia, the stage of infection, and the immune status of infected cats. It appears that M. haemominutum infections are potentiated by feline leukemia virus coinfection (George et al, 2003). Clinical signs and physical examination abnormalities associated with anemia are most common and include pale mucous membranes, depression, inappetence, weakness, and occasionally, icterus and splenomegaly. Fever occurs in some acutely infected cats and may be intermittent in chronically infected cats. Evidence of coexisting disease may be present. Weight loss is common in chronically infected cats. Cats in the chronic phase can be subclinically infected only to have recurrence of clinical disease following periods of stress. A greater percentage of cats with fever are infected with M. haemofelis than cats without fever suggesting the organism can be associated with fever of unknown origin (Lappin et al, 2002).
The anemia associated with Mycoplasma spp. infections is generally macrocytic, normochromic but may be macrocytic, hypochromic if coinfections leading to chronic inflammation exist. Chronic non-regenerative anemia is unusual in Mycoplasma spp. infections. Neutrophilia and monocytosis have been reported in some Mycoplasma spp.-infected cats. Diagnosis is based on demonstration of the organism on the surface of erythrocytes on examination of a thin blood film or polymerase chain reaction (PCR). Organism numbers fluctuate and so blood film examination can be falsely negative up to 50% of the time. The organism may be difficult to find cytologically, particularly in the chronic phase. Thus, the PCR is the test of choice due to sensitivity. Primers are available that amplify a segment of the 16S rRNA gene common to both Mycoplasma spp. (Jensen et al, 2001).
Since hemoplasmosis and primary immune hemolytic anemia are difficult to differentiate, cats with severe, regenerative hemolytic anemia should be treated with glucocorticoids and antibiotics. Doxycycline has less side effects than other tetracyclines in cats and so is preferred. Doxycycline should be given at 10 mg/kg, PO, every 24 hours for at least 14 days. If administered for 28 days, more cats appear to stay persistently PCR negative. Generic tablets have been associated with esophageal strictures and should be liquefied or water should be given after pilling. Butter can also be coated on the tablet or rubbed on the nasal planum after pilling. If autoagglutination is evident, prednisolone is usually prescribed at 1 mg/kg, PO, every 12 hours for the first 7 days or until autoagglutination is no longer evident. Tetracyclines utilized to date appear to lessen parasitemia and clinical signs of disease but probably do not clear the organism from the body. In one study, experimentally infected cats treated with doxycycline have apparent clinical response but the organism could still be detected by PCR when the cats were given methylprednisolone acetate.
In cats intolerant of doxycycline, enrofloxacin should be considered. Enrofloxacin given at 5 mg/kg, PO, every 24 hours or at 10 mg/kg, PO, every 24 hours for 14 days is tolerated by cats and is equally effective or more effective than doxycycline. However, the 5 mg/kg dose should be used since blindness occasionally occurs in cats treated with higher doses. It is currently unknown whether other quinolones are effective. Azithromycin was not effective for the treatment of hemoplasmosis in one study (Westfall et al, 2001). Imidocarb dipropriate administered at 5 mg/kg, IM, every 2 weeks for at least 2 injections was used successfully in the management of five naturally-infected cats that had failed treatment with other drugs (Lappin et al, 2002). Blood transfusion should be given if clinically indicated. Potential arthropod vectors should be controlled. Cats should be housed indoors to avoid vectors and fighting. Clinic blood donor cats should be screened for Mycoplasma spp. infections by polymerase chain reaction. In a recent national prevalence study, it was shown that 9.8% of the cats used as blood donors were PCR positive for hemoplasmas (Hackett et al, 2003).
1. Berent LM, Messick JB, Cooper SK. Detection of Haemobartonella felis in cats with experimentally induced acute and chronic infections, using a polymerase chain reaction. Am J Vet Res 1998;59:1215-1220.
2. Bobabe PA, Nash AS, Rogerson P. Feline hemobartonellosis: clinical, haematological and pathological studies in natural infections and the relationship to infection with feline leukaemia virus. Vet Rec 1988;122:32-26
3. Dowers KL, Olver C, Radecki SV, Lappin MR. Enrofloxacin for treatment of cats experimentally infected with large form Haemobartonella felis. J Am Vet Med Assoc 2002:221;250-253
4. Cretillat S. Feline haemobartonellosis. Feline Pract 1984;14:22-27
5. Edwards F. A new blood parasite in British cats. Vet Rec 1960;72:439
6. Fisher E. Anemia in a litter of Siamese kittens. J Small Anim Pract 1983;34:315-219
7. Flint JC, Moss J. Infectious anemia in cats. J Am Vet Med Assoc 1953;122:45-48
8. Flint J, Roepke M, Jensen R. Feline infectious anemia Clinical aspects. Am J Vet Res 1958;19:164-168.
9. Flint J, Roepke M, Jensen R. Feline infectious anemia Experimental cases. Am J Vet Res 1959;20:33-40
10. Foley JE, Pedersen NC. 'Candidatus Mycoplasma haemominutum', a low-virulence epierythrocytic parasite of cats. Int J Sys Evol Microbiol 2001; 51: 815-817
11. Foley JE, Harrus S, Poland A, et al. Molecular, clinical, and pathologic comparison of two distinct strains of Haemobartonella felis in domestic cats. Am J Vet Res 1998;59;1581-1588
12. George JW, Rideout BA, Griffey SM, et al. Effect of preexisting FeLV or FeLV and feline immunodeficiency virus coinfection on pathogenicity of the small variant of Haemobartonella felis in cats. Am J Vet Res 2002;63:1172-1178
13. Grindem CB, Corbett WT, Tomkins MT. Risk factors for Haemobartonella felis infection in cats. J Am Vet Med Assoc 1990;196:96-99
14. Hackett TB, Lappin MR, Jensen WA, et al. Prevalence of Mycoplasma haemofelis and M. haemominutum in blood donor cats. Proceedings of the ACVIM meeting, June, 2003
15. Harbutt P. A clinical appraisal of feline infectious anemia and its transmission under natural conditions. Aust Vet J 1963;30:402-404
16. Harvey J, Gaskin J. Experimental feline hemobartonellosis. J Am Animal Hosp Assoc 1977;13:28-38
17. Hayes H, Priester W. Feline infectious anemia. Risk by age, sex, and breed; prior disease; seasonal occurrence; mortality. J Small Anim Pract 1973;14"797-804
18. Jensen WA, Lappin MR, Reagan W, et al. Use of a polymerase chain reaction assay to detect and differentiate two strains of Haemobartonella felis in naturally infected cats. Am J Vet Res 2001;62:604-608
19. Lappin MR. Infectious causes of fever in cats. J Vet Int Med 2002;16:366
20. Lappin MR, Brunt J, Riley A, et al. Bartonella spp. and Mycoplasma haemominutum DNA in the blood of cats and their fleas. Proceedings of the ACVIM meeting, June, 2003
21. Lappin MR, Foster A, Geitner K, et al. Imidocarb diproprionate for the treatment of recurrent haemobartonellosis in cats. J Vet Int Med 2002;16:364
22. Maede Y, Hata R. Studies on feline haemobartonellosis II. The mechanism of anemia produced by infection Haemobartoella felis. Jpn J Vet Sci 1975;37:49-54
23. Maede Y. Sequestration and phagocytosis of Hemobartonella felis in the spleen. Am J Vet Res 1979;40:691-695
24. Messick JB, Berent LM, Cooper SK. Development and evaluation of a PCR-based assay for detection of Haemobartonella felis in cats and differentiation of H. felis from related bacteria by restriction fragment length polymorphism analysis. J Clin Microbiol 1998;36:462-466
25. Nash A, Bobade P. Haemobartonella felis infection in cats from the Glasgow area. Vet Rec 1986;119;373-375
26. Neimark H, Johansson KE, Rikihisa Y, et al. Proposal to transfer some members of the genera Haemobartonella and Eperythrozoon to the genus Mycoplasma with descriptions of 'Candidatus Mycoplasma haemofelis', 'Candidatus Mycoplasma haemomuris', 'Candidatus Mycoplasma haemosuis' and 'Candidatus Mycoplasma wenyonii'. Int J Sys Evol Microbiol 2001; 51: 891-899
27. Rikihisa Y, Kawahara M, Wen B. et al. Western immunoblot analysis of Haemobartonella muris and comparison of 16S mRNA gene sequences of H. muris, H. felis, and Eperythrozoon suis. J Clin Microbiol 1997;35:823-829
28. Schalm O. Feline infectious anemia. Feline Pract 1972;1:26-30
29. Small E, Ristic M. Haemobartonellosis. Vet Clin North Am 1971;1:225-230
30. Splitter E, Castro E, Kanawyer W. Feline infectious anemia. Vet Med 1956;51:17-22
31. Tasker S, Helps CR, Belford CJ, et al. 16S rDNA comparison demonstrates near identity between an United Kingdom Haemobartonella felis strain and the American California strain. Vet Microbiol 2001;81:73-78
32. Tasker S, Binns SH, Day MJ, et al. Use of a PCR assay to assess prevalence and risk factors for Mycoplasma haemofelis and 'Candidatus Mycoplasma haemominutum' in cats in the United Kingdom. Veterinary Record 2003;152:193-198
33. Tasker S, Helps CR, Day MJ, et al. Use of a Taqman PCR to determine the response of Mycoplasma haemofelis to antibiotic treatment. J Microbiol Methods 2004;56:63-71
34. Tasker S, Lappin MR. Haemobartonella felis: recent developments in diagnosis and treatment. J Fel Med Surg 2002;4:3-11
35. VanSteenhouse JL, Taboada J, Millard J. Feline hemobartonellosis. Compend Contin Educ Pract Vet 1993;15:535-545
36. VanSteenhouse JL, Taboada J, Dorfman MI. Hemobartonella felis infection with atypical hematological abnormalities. J Am Anim Hosp Assoc 1995;31:165
37. Westfall DS, Jensen WA, Reagan W, Radecki S, Lappin MR. Inoculation of two genotypes of Haemobartonella felis (California and Ohio variants) to induce infection in cats and response to treatment with azithromycin. Am J Vet Res 2001;62:687-691
38. Woods JE, Hawley JR, Lappin MR, et al. Attempted transmission of Haemobartonella felis by Ctenocephalides felis. Proceedings of the ACVIM meeting, June, 2003