Abstract
BackgroundHepatozoon canis is a protozoan tick-borne pathogen of dogs and wild canids. Hepatozoon spp. have been reported to infect foxes in different continents and recent studies have mostly used the polymerase chain reaction (PCR) for the detection and characterization of the infecting species. Surveying red foxes (Vulpes vulpes) may contribute to better understanding the epidemiology of canine vector-borne diseases, including hepatozoonosis caused by H. canis in domestic dogs. The present study investigated the prevalence of Hepatozoon spp. by means of histopathology and molecular analysis of different tissues in red foxes from different parts of Portugal.MethodsBlood and tissues including bone marrow, heart, hind leg muscle, jejunum, kidney, liver, lung, popliteal or axillary lymph nodes, spleen and/or tongue were collected from 91 red foxes from eight districts in northern, central and southern Portugal. Tissues were formalin-fixed, paraffin-embedded, cut and stained with hematoxylin and eosin. Polymerase chain reaction (PCR) amplified a ~650 bp fragment of the 18S rRNA gene of Hepatozoon spp. and the DNA products were sequenced.ResultsHepatozoon canis was detected in 68 out of 90 foxes (75.6%) from all the sampled areas by PCR and sequencing. Histopathology revealed H. canis meronts similar in shape to those found in dogs in the bone marrow of 11 (23.4%) and in the spleen of two (4.3%) out of 47 foxes (p = 0.007). All the 11 foxes found positive by histopathology were also positive by PCR of bone marrow and/or blood. Positivity by PCR (83.0%) was significantly higher (p < 0.001) than by histopathological examination (23.4%) in paired bone marrow samples from the same 47 foxes. Sequences of the 18S rRNA gene of H. canis were 98–99% identical to those in GenBank.ConclusionsHepatozoon canis was found to be highly prevalent in red fox populations from northern, central and southern Portugal. Detection of the parasite by histopathology was significantly less sensitive than by PCR. Red foxes are a presumptive reservoir of H. canis infection for domestic dogs.
Highlights
Hepatozoon canis is a protozoan tick-borne pathogen of dogs and wild canids
Positivity by polymerase chain reaction (PCR) (83.0%) was significantly higher (p < 0.001) than by histopathological examination (23.4%) in paired bone marrow samples from the same 47 foxes
All the 11 foxes found positive by histopathology were positive by PCR of bone marrow and/or blood
Summary
Hepatozoon canis is a protozoan tick-borne pathogen of dogs and wild canids. Surveying red foxes (Vulpes vulpes) may contribute to better understanding the epidemiology of canine vector-borne diseases, including hepatozoonosis caused by H. canis in domestic dogs. Hepatozoonosis caused by Hepatozoon canis is a canine vector-borne disease (CVBD) reported from the Old World and more recently from South and North America [1]. The apicomplexan parasite H. canis (suborder Adeleorina: family Hepatozoidae) has a life cycle which involves vertebrates as intermediate hosts, including domestic dogs and wild canids, and ticks as definitive hosts [2]. Transmission of H. canis to the vertebrate hosts typically takes place by ingestion of the arthropod vector containing mature protozoal oocysts with infective sporozoites [5,6]. Merozoites infect leukocytes where the gamont stage of the protozoan, infective for the tick, is found later [8]
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