The First Case of Cytauxzoon spp. in Russia: The Parasite Conquers Eurasia

Molecular survey of Cytauxzoon spp. and Hepatozoon spp. in felids using a novel real-time PCR approach

Tick-transmitted apicomplexans of the genera Cytauxzoon and Hepatozoon affect a wide range of felids worldwide, but little is known about them. Recently, several studies addressed the species circulating in Europe, their distribution, and their hosts. Molecular assays are the method of choice for their detection. Unfortunately, conventional PCRs already described are time- and cost-consuming and specific for either Hepatozoon or Cytauxzoon detection. This study was developed to evaluate (i) the occurrence of Cytauxzoon and Hepatozoon in felids using a fast and cost-saving real-time PCR capable of detecting both protozoa simultaneously, (ii) the distribution of Cytauxzoon and Hepatozoon species in north-eastern Italy, and (iii) the involvement of other susceptible felid hosts in the same area. An SYBR^® Green-based real-time PCR with primers targeting the 18S-rRNA was validated and applied to 237 felid samples, i.e., whole blood from 206 domestic cats and 12 captive exotic felids, and tissues from 19 wildcats. Positive results were obtained by melting temperature curve analysis due to the specific melting peak (i.e., 81°C Cytauxzoon spp.; 78-78.5°C Hepatozoon spp.). Positive samples were subjected to conventional PCR, followed by sequencing for species identification. Phylogenetic analyses were performed to assess relatedness among European isolates. Data on domestic cats (age class, sex, origin, management, and lifestyle) were recorded, and statistical analyses were performed to identify potential risk factors. A total of 31 (15%) domestic cats were positive for Hepatozoon spp. (i.e., 12 for H. felis, 19 for H. silvestris), while six (2.9%) for C. europaeus. The prevalence of Hepatozoon felis was significantly (p < 0.05) higher in domestic cats, while H. silvestris was higher in strays and animals from the Eastern region (i.e., Friuli-Venezia Giulia). Cytauxzoon europaeus was detected only in stray cats from Friuli-Venezia Giulia (province of Trieste). Among captive felids, one tiger was infected with H. felis and another with H. silvestris; eight out of 19 (42%) wildcats were positive for Hepatozoon spp. (i.e., six with H. felis, two with H. silvestris) and four out of 19 (21%) for Cytauxzoon europaeus. Outdoor lifestyle and origin (i.e., Friuli-Venezia Giulia region) were the most relevant risk factors for H. silvestris and C. europeus infections. Conversely, H. felis was most frequently isolated from domestic cats, suggesting different modes of transmission.

A Novel Vaccine Strategy to Prevent Cytauxzoonosis in Domestic Cats

Cytauxzoonosis is caused by Cytauxzoon felis (C. felis), a tick-borne parasite that causes severe disease in domestic cats in the United States. Currently, there is no vaccine to prevent this fatal disease, as traditional vaccine development strategies have been limited by the inability to culture this parasite in vitro. Here, we used a replication-defective human adenoviral vector (AdHu5) to deliver C. felis-specific immunogenic antigens and induce a cell-mediated and humoral immune response in cats. Cats (n = 6 per group) received either the vaccine or placebo in two doses, 4 weeks apart, followed by experimental challenge with C. felis at 5 weeks post-second dose. While the vaccine induced significant cell-mediated and humoral immune responses in immunized cats, it did not ultimately prevent infection with C. felis. However, immunization significantly delayed the onset of clinical signs and reduced febrility during C. felis infection. This AdHu5 vaccine platform shows promising results as a vaccination strategy against cytauxzoonosis.

Apicomplexan haemoparasites in domestic cats in Romania

BACKGROUND

Apicomplexan haemoparasites are protozoans that infect a variety of domestic and wild animal species, as well as humans. Data regarding haemoprotozoans in domestic cats are limited; therefore, the aim of this study was to assess the occurrence of Babesia spp., Cytauxzoon spp., and Hepatozoon spp. in domestic cats in Romania using molecular tools.

METHODS

Blood samples from 371 domestic cats were screened for the presence of piroplasmids. All samples that yielded a visible band in agarose gels were subsequently tested by specific assays targeting the 18S rDNA of Babesia spp., Cytauxzoon spp., and Hepatozoon spp. Moreover, nested PCR assays targeting mitochondrial genes of Babesia spp. were used for screening of all Babesia spp. 18S rDNA-positive samples.

RESULTS

From the total number of sampled cats, 19.4% were positive in the PCR assay targeting piroplasmids. Babesia spp. were identified in 15.1% of cats, while 0.5% were positive for Hepatozoon spp. Molecular analyses confirmed the presence of Babesia canis. No samples were positive for Cytauxzoon spp.

CONCLUSIONS

The high infection rates of domestic cats with Babesia spp. and the need for species differentiation highlight the importance of mitochondrial genes as targets for molecular protocols.

Can Domestic Cats Act as Reservoirs of Cytauxzoon felis?

Cytauxzoonosis is a worldwide tick-borne disease of domestic and wild felids, caused by infection of the haemoparasites belonging to the genus Cytauxzoon (Piroplasmida, Apicomplexa), which are apicomplexan protozoans closely related to those of the genera Babesia and Theileria [...].

Assessment of the current state of ecosystems taking into account the diversity of adventitious species

Aim. When assessing the degree of transformation and openness of the territory for invasive species, a description of the current state of their biological diversity should be made taking into account the diversity index of adventitious species.

Discussion. The problem of intensification of biological invasions has now become one of the world's most acute problems. Biological invasions of alien species have acquired such a scale that by now it is almost impossible to find terrestrial or aquatic ecosystems, wherever adventitious organisms are found. In practice, a number of categories and indices of diversity are used to assess biological diversity, and the methods of their measurement and analysis are also different. But all of them operate with almost two indicators – the number of species and their relative abundance – quantitative parameters, without taking into account modern qualitative changes in species in the composition of ecosystems.

Results. It is proposed to introduce additional estimates of the share of adventitious species (the "adventiousness index") in the assessments of total biodiversity, which are necessary to solve a whole range of practical tasks. They give an idea of the state of ecosystems at the moment in a certain area, serve as the basis for the development of a management system for individual species, are necessary to assess the suitability of potential habitats for reintroduction and etc.

Clinicopathological findings and risk factors associated with Cytauxzoon spp. infection in cats: A case-control study (2008–2021)

In Europe, Cytauxzoon spp. infection was documented in domestic and wild felids. Cats often develop a subclinical infection, while fatal disease is rare. Currently, information on the epidemiology, risk factors and clinicopathological findings of Cytauxzoon spp. infection remains limited and obtained by a single subject or small groups of cats. The objective of this case-control study was to evaluate clinicopathological findings and to describe risk factors associated with Cytauxzoon spp. infection in domestic cats. Infected cats (n = 39) and non-infected (n = 190) cats were selected from the database of the referral San Marco Veterinary Laboratory between 2008 and 2021. Demographic information, a preset questionnaire considering lifestyle, environment, and clinical status, and a CBC performed contextually with the PCR analysis were recorded for all cats. Data on the biochemical profile and serum protein electrophoresis were also evaluated when available. Compared to the control group, infection was more likely to occur in stray cats (24/39, 61.5%, P &lt; 0.001), living totally/partially outdoors (36/39, 92.3%, P &lt; 0.001), in an urban context (37/39, 94.9%, P = 0.002), taken or recently adopted from colonies (34/35, 97.1, P &lt; 0.001), with irregular or absent parasite preventive treatments (39/39, 100%, p = 0.005), without fleas (28/35, 80%, P = 0.047) and without clinical signs (22/39, 56.4%, p = 0.026) at the time of medical evaluation. Anemia was not associated with infection, but in cats without clinical signs, the percentage of anemic-infected cats (7/22, 31.8%, P = 0.009) was higher compared to non-infected cats (5/65, 7.7%). Furthermore, a decrease in total iron serum concentration approximating the lowest reference interval [median values (IQR): 79 μg/dL (52.25) vs. 50.5 μg/dL (34), P = 0.007] was likely in infected cats. No other laboratory findings were associated with infection. Interestingly, a partial/total outdoor lifestyle was a risk factor for infection (OR: 8.58, 95% CI: 2.90–37.0, P &lt; 0.001). In conclusion, the present study revealed that Cytauxzoon spp. infection manifests itself prevalently as a subclinical infection, based on physical examination and laboratory findings, in domestic European cats. However, subclinical infected cats were more likely to be anemic compared to non-infected.