(Author: Simonato, G., Franco, V., Salvatore, G. et al. First autochthonous clinical case of Hepatozoon silvestris in a domestic cat in Italy with unusual presentation. Parasites Vectors 15, 440 (2022).


Hepatozoon spp. is the causative agent of a vector-borne parasitic disease in many animal species. In felids, Hepatozoon felis, Hepatozoon canis and Hepatozoon silvestris have been molecularly isolated. Hepatozoonosis usually causes asymptomatic infections in domestic cats, but clinical cases have recently been reported in Europe. We describe the first Italian case of hepatozoonosis in a cat with an unusual presentation. An 11-year-old neutered European shorthair cat was urgently hospitalized for intestinal intussusception. Hematology, biochemistry, FIV-FeLV tests, blood smears and molecular investigation targeting the 18S rRNA gene of Hepatozoon spp. were performed on blood samples; in addition, histological and molecular investigations were performed to analyze surgical samples to identify Hepatozoon infection. Hepatozoon gamonts were detected in granulocytes in the blood smear, and Hepatozoon spp. DNA was confirmed by PCR on blood. The intussusception was caused by a sessile endoluminal nodule that was surgically removed. Histologically, many elements referring to parasitic tissue forms were identified in the intestinal cells, and then the specimens were molecularly confirmed to harbor H. silvestris. This is the first description of symptomatic hepatozoonosis in a domestic cat in Italy. Hepatozoon silvestris has been described in wild felids, which are usually resilient to the infection, whereas the domestic cat seems to be more susceptible. Indeed, H. silvestris in cats usually presents tropism for skeletal muscle and myocardium with subsequent clinical manifestations. This is the first description of a domestic cat with H. silvestris localized in the intestinal epithelium and associated with intussusception.

Hepatozoonosis is a vector-borne disease affecting many of animals, including reptiles, birds and mammals; it is caused by an apicomplexan parasite, of which almost 340 species are currently described [1,2,3]. Almost 50 species are recognized in mammals [1], but comprehensive information regarding their life cycle is known for only a few of them. Usually, the Hepatozoon life cycle involves an intermediate and a definitive host represented by a vertebrate animal and an arthropod vector, respectively [4]. In contrast to other vector-borne protozoa (e.g. Babesia spp., Leishmania infantum) transmitted to humans and animals bitten by infected arthropods, in hepatozoonosis, the vertebrate host becomes infected through the ingestion of infected arthropods [12]. In the vertebrate host, the asexual replication of Hepatozoon takes place, generating intracellular gamonts that circulate in the bloodstream. The vectors, mostly represented by ticks, ingest Hepatozoon gamonts through blood-feeding from infected animals, and sexual replication takes place within the ticks, ending in the production of mature oocysts that are ready to infect a new vertebrate host and complete the life cycle when the arthropod will be ingested [2]. Interestingly, other transmission routes have been reported, e.g. in the Hepatozoon canis and Hepatozoon felis life cycles, vertical intrauterine transmission is described, and in the Hepatozoon americanum life cycle, predation (i.e. the ingestion of infected prey) has been proven to be an additional transmission route [256].


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