Diagnosis of Hepatozoon canis in young dogs by cytology and PCR

Domenico Otranto,Gad Baneth,Gioia Capelli,Donato Decaprariis,Stefania Weigl,Dorothee Stanneck,Maria Stefania Latrofa,Filipe Dantas-Torres

doi:10.1186/1756-3305-4-55

Abstract

BackgroundHepatozoon canis is a widespread tick-borne protozoan affecting dogs. The diagnosis of H. canis infection is usually performed by cytology of blood or buffy coat smears, but this method may not be sensitive. Our study aimed to evaluate the best method to achieve a parasitological diagnosis of H. canis infection in a population of receptive young dogs, previously negative by cytology and exposed to tick infestation for one summer season.ResultsA total of 73 mongrel dogs and ten beagles younger than 18 months of age, living in an animal shelter in southern Italy where dogs are highly infested by Rhipicephalus sanguineus, were included in this study. In March-April 2009 and in October 2009, blood and bone marrow were sampled from each dog. Blood, buffy coat and bone marrow were examined by cytology only (at the first sampling) and also by PCR for H. canis (second sampling). In March-April 2009, only one dog was positive for H. canis by cytological examination, whereas in October 2009 (after the summer season), the overall incidence of H. canis infection by cytological examinations was 43.9%. Molecular tests carried out on samples taken in October 2009 showed a considerably higher number of dogs positive by PCR (from 27.7% up to 51.2% on skin and buffy coat tissues, respectively), with an overall positivity of 57.8%. All animals, but one, which were positive by cytology were also PCR-positive. PCR on blood or buffy coat detected the highest number of H. canis-positive dogs displaying a sensitivity of 85.7% for both tissues that increased up to 98% when used in parallel. Twenty-six (74.8%) out of the 28 H. canis-positive dogs presented hematological abnormalities, eosinophilia being the commonest alteration observed.ConclusionsThe results suggest that PCR on buffy coat and blood is the best diagnostic assay for detecting H. canis infection in dogs, although when PCR is not available, cytology on buffy coat should be preferred to blood smear evaluation. This study has also demonstrated that H. canis infection can spread among young dogs infested by R. sanguineus and be present in the majority of the exposed population within 6 months.

Highlights

Hepatozoon canis is a widespread tick-borne protozoan affecting dogs
Our study aimed to evaluate the best method to achieve a parasitological diagnosis of H. canis infection in a population of receptive young dogs, previously negative by cytology and exposed to tick infestation for one summer season
This led to an overall incidence of H. canis infection inferred exclusively by cytology positivity to Statistical analysis The prevalence recorded by each test was calculated at both follow-ups

Summary

Introduction

Hepatozoon canis is a widespread tick-borne protozoan affecting dogs. The diagnosis of H. canis infection is usually performed by cytology of blood or buffy coat smears, but this method may not be sensitive. H. canis is probably one of the most widespread canine vector-borne disease (CVBD)-causing pathogens due to its close association with R. sanguineus and the cosmopolitan distribution of this tick species [8,9]. Large surveys on canine hepatozoonosis are scant [10], a number of reports suggest that H. canis infects dogs globally and infections have been reported from four continents [7,10,11,12,13]. This protozoan usually causes a chronic infection with relatively mild or no clinical alterations to its host [14,15]. In endemic areas, CVBD-causing pathogens may infect the same dog with two (H. canis and Ehrlichia canis) [17], three (H. canis, Babesia spp., E. canis) [10,20] or even four agents (H. canis, Babesia spp., E. canis, Leishmania infantum) [21]

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