Molecular, clinical, and pathologic comparison of two distinct strains of Haemobartonella felis in domestic cats

Am J Vet Res. 1998 Dec;59(12):1581-8.


Objective: To characterize 2 strains of Haemobartonella felis by use of molecular techniques.

Animals: 35 specific-pathogen-free cats, 6 months to 4 years old.

Procedure: Intraperitoneal or IV inoculation with blood containing H felis small form (Hfsm, 18 cats) or H felis large form (Hflg, 11 cats); 6 cats were uninfected controls. Hfsm was evaluated for capability to cross-protect against the more virulent Hflg. Morphology of both strains was compared by light microscopy of Wright-Giemsa-stained blood smears, and the 16S rRNA genes were sequenced.

Results: Infection with Hflg induced signs of depression, fever, and severe macrocytic normochromic anemia with nucleated erythrocytes. More than 95% of erythrocytes were parasitized. Inoculation with Hfsm and uninfected control blood induced mild or no clinical signs and no hematologic abnormalities. Anti-H felis IgG was first detected on postinoculation day (PID) 21, and increased to maximal titer of 400 by PID 28. Reactivated infection was observed in 8 of 29 cats (4 Hfsm and 4 Hflg), with 5% parasitized erythrocytes during the later attack. On PID 8, Hflg-inoculated cats had positive results of polymerase chain reaction analysis (PCR) that persisted until cats were treated with doxycycline or oxytetracycline; Hfsm-inoculated cats had positive PCR results that persisted for duration of observation (3 months).

Conclusions: Genetically and morphologically distinct strains of H felis infect cats in the field. The level of genetic difference suggested that these strains may be different species or genera.

Clinical relevance: PCR is a critical diagnostic aid to detect occult Haemobartonella spp infection, as well as response to treatment and clearance of the organism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaplasmataceae / classification*
  • Anaplasmataceae / genetics
  • Anaplasmataceae / pathogenicity
  • Anaplasmataceae Infections / diagnosis
  • Anaplasmataceae Infections / physiopathology
  • Anaplasmataceae Infections / veterinary*
  • Animals
  • Cat Diseases / blood
  • Cat Diseases / diagnosis
  • Cat Diseases / physiopathology*
  • Cats
  • DNA Primers
  • Erythrocytes / microbiology
  • Phylogeny
  • Polymerase Chain Reaction
  • RNA, Ribosomal, 16S / genetics


  • DNA Primers
  • RNA, Ribosomal, 16S