The first report on Hepatozoon canis in dogs and wolves in Poland: clinical and epidemiological features

Abstract

Background: Canine hepatozoonosis caused by Hepatozoon canis is a common infection in dogs, with frequent case reports from the Mediterranean region and more recently from several Central European countries, such as Hungary and Germany. Despite the high prevalence of H. canis in red foxes, no infections have been reported to date in dogs in Poland. We describe here the first autochthonous cases of H. canis infection in dogs, including their clinical features, and report the prevalence of H. canis in grey wolves from different regions of Poland.

Methods: Thin smears prepared from blood samples collected from dogs were evaluated by microscopic examination. A total of 60 wolves and 47 dogs were tested. Infections were confirmed by PCR and sequencing.

Results: Gamonts of H. canis were found in > 50% of the neutrophils of two dogs and in < 10% of the neutrophils in another five dogs. Molecular typing by PCR sequencing of the 18S ribosomal RNA gene fragment confirmed infections in 11 dogs from different regions of Poland, in 2.7% of dogs attending veterinary practices in central Poland and in 35% of wolves from various geographical regions of Poland. Clinical features manifested mostly in older dogs, and the most common signs were anaemia and apathy. Young dogs usually remained asymptomatic.

Conclusions: This is the first report of H. canis infection in dogs and wolves in Poland. Although the exact vector of the parasite is not known, veterinary practitioners should be aware of this new parasitosis and should consider appropriate diagnostics to confirm/exclude this infection. Further studies are needed to understand the transmission routes of H. canis in domestic and wild canids in Poland.

Keywords: Canis lupus familiaris; Hepatozoon canis; Hepatozoonosis; PCR; Poland; Ticks; Wolves.

Fig. 1

Map of Poland presenting locations where dogs and wolves were found. Collection sites for dogs and wolves. Yellow dots represent the collection site of the infected dogs, blue dots represent the collection site of noninfected wolves and red dots represent Hepatozoon canis–positive wolf samples. The territorial extent of Poland is highlighted by the green-shaded area, with neighbouring countries depicted by orange-shaded areas. The grey lines represent international borders, and the Baltic Sea is represented by the light blue-shaded area

Fig. 2

Gamonts (red arrows) of Hepatozoon canis in neutrophils in the peripheral blood of the dog (case 1)

Fig. 3

Evolutionary history of Hepatozoon based on the fragment of the 18S ribosomal RNA gene was inferred by using the maximum likelihood method and Tamura 3-parameter model [34]. The tree with the highest log likelihood (− 1031.63) is shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches. Initial tree(s) for the heuristic search were obtained automatically by applying the neighbour-joining and BioNJ algorithms to a matrix of pairwise distances estimated using the Tamura 3 parameter model, and then selecting the topology with the superior log likelihood value. The rate variation model allowed for some sites to be evolutionarily invariable ([+ I], 64.45% sites). The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. This analysis involved 46 nucleotide sequences. The codon positions included were 1st + 2nd + 3rd + Noncoding. All positions containing gaps and missing data were eliminated (complete deletion option). In the final dataset, there were 314 positions. The nucleotide sequence of Cryptosporidium parvum was used as an outgroup. Evolutionary analyses were conducted in MEGA v. 11 [33]