Molecular, clinical, and pathologic comparison of two distinct strains of Haemobartonella felis in domestic cats.
OBJECTIVE
To characterize 2 strains of Haemobartonella felis by use of molecular techniques.


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


METHODS
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.


CONCLUSIONS
PCR is a critical diagnostic aid to detect occult Haemobartonella spp infection, as well as response to treatment and clearance of the organism.
Foley
J E
JE
Center for Companion Animal Health, School of Veterinary Medicine, University of California, Davis 95616, USA.
Harrus
S
S
Poland
A
A
Chomel
B
B
Pedersen
N C
NC
D000710:Anaplasmataceae / Q000145:classification* / Q000235:genetics / Q000472:pathogenicity; D000711:Anaplasmataceae Infections / Q000175:diagnosis / Q000503:physiopathology / Q000662:veterinary*; D000818:Animals; D002371:Cat Diseases / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology*; D002415:Cats; D017931:DNA Primers; D004912:Erythrocytes / Q000382:microbiology; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics
D017931:DNA Primers; D012336:RNA, Ribosomal, 16S