Abstract
BackgroundA Hepatozoon parasite was initially reported from a cat in India in 1908 and named Leucocytozoon felis domestici. Although domestic feline hepatozoonosis has since been recorded from Europe, Africa, Asia and America, its description, classification and pathogenesis have remained vague and the distinction between different species of Hepatozoon infecting domestic and wild carnivores has been unclear. The aim of this study was to carry out a survey on domestic feline hepatozoonosis and characterize it morphologically and genetically.MethodsHepatozoon sp. DNA was amplified by PCR from the blood of 55 of 152 (36%) surveyed cats in Israel and from all blood samples of an additional 19 cats detected as parasitemic by microscopy during routine hematologic examinations. Hepatozoon sp. forms were also characterized from tissues of naturally infected cats.ResultsDNA sequencing determined that all cats were infected with Hepatozoon felis except for two infected by Hepatozoon canis. A significant association (p = 0.00001) was found between outdoor access and H. felis infection. H. felis meronts containing merozoites were characterized morphologically from skeletal muscles, myocardium and lungs of H. felis PCR-positive cat tissues and development from early to mature meront was described. Distinctly-shaped gamonts were observed and measured from the blood of these H. felis infected cats. Two fetuses from H. felis PCR-positive queens were positive by PCR from fetal tissue including the lung and amniotic fluid, suggesting possible transplacental transmission. Genetic analysis indicated that H. felis DNA sequences from Israeli cats clustered together with the H. felis Spain 1 and Spain 2 sequences. These cat H. felis sequences clustered separately from the feline H. canis sequences, which grouped with Israeli and foreign dog H. canis sequences. H. felis clustered distinctly from Hepatozoon spp. of other mammals. Feline hepatozoonosis caused by H. felis is mostly sub-clinical as a high proportion of the population is infected with no apparent overt clinical manifestations.ConclusionsThis study aimed to integrate new histopathologic, hematologic, clinical, epidemiological and genetic findings on feline hepatozoonosis and promote the understanding of this infection. The results indicate that feline infection is primarily caused by a morphologically and genetically distinct species, H. felis, which has predilection to infecting muscular tissues, and is highly prevalent in the cat population studied. The lack of previous comprehensively integrated data merits the redescription of this parasite elucidating its parasitological characteristics.
Highlights
A Hepatozoon parasite was initially reported from a cat in India in 1908 and named Leucocytozoon felis domestici
The feline parasite was later transferred to the genus Hepatozoon and it was suggested that Hepatozoon parasites from the cat, jackal and hyena are indistinguishable from Hepatozoon canis, which infects dogs, due to the similarity in morphology of the gamont stage seen in the blood of these animals [8]
Collection of positive samples detected during routine laboratory evaluation Anticoagulated blood in EDTA tubes from 19 domestic cats in which Hepatozoon sp. gamonts were detected by May Grunwald Giemsa-stained blood smear microscopy at the Hebrew University Veterinary Teaching Hospital (HUVTH) and at the private Pathovet Veterinary Pathology Laboratory in Israel during routine blood tests, were collected from 2002 to 2011 and stored at – 80 C
Summary
A Hepatozoon parasite was initially reported from a cat in India in 1908 and named Leucocytozoon felis domestici. Hepatozoon species are apicomplexan parasites with a hematophagous arthropod final host and a vertebrate intermediate host. Additional transmission pathways have been described in some Hepatozoon spp. including intrauterine transmission and carnivorism of the intermediate host by an intermediate host of a different species [2,3,4,5]. A Hepatozoon parasite was reported for the first time from the blood of a domestic cat in India by Patton in 1908 and named Leucocytozoon felis domestici [7]. The feline parasite was later transferred to the genus Hepatozoon and it was suggested that Hepatozoon parasites from the cat, jackal and hyena are indistinguishable from Hepatozoon canis, which infects dogs, due to the similarity in morphology of the gamont stage seen in the blood of these animals [8]. No parasites were morphologically described in the cat’s blood, the sequences from these cats were designated as H. felis and deposited in GenBank [14,16]
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