First evidence of vertical Hepatozoon canis transmission in dogs in Europe.

Background: Hepatozoon canis is a protozoal agent that is known to be transmitted by oral uptake of H. canis-infected Rhipicephalus sanguineus sensu lato ticks in dogs. Vertical transmission of H. canis has only been described once in a study evaluating dogs from Japan. The aim of this study was to investigate the parasitological status of puppies from a bitch that had tested positive for Hepatozoon spp. prior to giving birth.

Findings: A 4-year-old, female, pregnant dog imported from Italy (Sardinia) to Germany showed clinical signs of lethargy and tachypnoea and tested positive for H. canis by PCR. The dog gave birth to eight puppies, one of which was stillborn and another that had to be reanimated. Haematology, buffy coat analysis and a biochemistry profile were performed for each dog. EDTA-blood of the surviving seven puppies and bone marrow, liver, spleen, amniotic fluid, and umbilical cord of the stillborn puppy was tested for the presence of Hepatozoon spp. by PCR. The mother and the seven surviving puppies tested positive for H. canis by PCR at day 62 post-partum. Gamonts were detected in all dogs by buffy coat evaluation. Haematological and biochemistry results revealed mild abnormalities. In the stillborn puppy, spleen, umbilical cord, and amniotic fluid were positive for H. canis.

Conclusion: The results confirm that vertical transmission is a possible route of H. canis infection in dogs, demonstrated by molecular detection of the pathogen in the stillborn puppy. In the seven surviving puppies, vertical transmission was the most likely transmission route. A potential impact of the level of parasitaemia on the health of puppies, as well as its pathogenesis, should be investigated further.