First Record of Hepatozoon spp. in Alpine Wild Rodents: Implications and Perspectives for Transmission Dynamics across the Food Web

A review of Hepatozoonosis caused by Hepatozoon canis in dogs

Hepatozoon canis is a type of single-celled organism is spread by ticks and commonly affects dogs. It is responsible for causing one of the most significant parasitic diseases in dogs, called Hepatozoonosis. It is considered one of the most common causes of canine vector-borne diseases because it is closely linked to Rhipicephalus sanguineus (the brown dog tick), a species found worldwide. Hepatozoonosis caused by H. canis is prevalent in regions such as South Europe, South America, Asia, and Africa. H. canis often causes emaciation, anemia, and intermittent fever in infected dogs. The drugs used to treat H. canis infection in dogs include the combination of imidocarb dipropionate with doxycycline, toltrazoril, tetracycline hydrochloride, and the combination of trimethoprim-sulfamethoxazole.The primary solution to prevent the spread of infections caused by H. canis is to control the population of R. sanguineus ticks because H. canis is spread through ticks. This review aims to provide a brief overview of various studies conducted on the morphology, life cycle, hosts, epidemiology, clinical symptoms, laboratory diagnosis, autopsy findings, differential diagnosis, treatment, and prevention methods of H. canis.

Do Babesia microti Hosts Share a Blood Group System Gene Ortholog, Which Could Generate an Erythrocyte Antigen That Is Essential for Parasite Invasion?

The United States of America (US) has the highest annual number of human babesiosis cases caused by Babesia microti (Bm). Babesia, like malaria-causing Plasmodium, are protozoan parasites that live within red blood cells (RBCs). Both infectious diseases can be associated with hemolysis and organ damage, which can be fatal. Since babesiosis was made a nationally notifiable condition by the Centers for Disease Control and Prevention (CDC) in January 2011, human cases have increased, and drug-resistant strains have been identified. Both the Bm ligand(s) and RBC receptor(s) needed for invasion are unknown, partly because of the difficulty of developing a continuous in vitro culture system. Invasion pathways are relevant for therapies (e.g., RBC exchange) and vaccines. We hypothesize that there is at least one RBC surface antigen that is essential for Bm invasion and that all Bm hosts express this. Because most RBC surface antigens that impact Plasmodium invasion are in human blood group (hBG) systems, which are generated by 51 genes, they were the focus of this study. More than 600 animals with at least one hBG system gene ortholog were identified using the National Center for Biotechnology Information (NCBI) command-line tools. Google Scholar searches were performed to determine which of these animals are susceptible to Bm infection. The literature review revealed 28 Bm non-human hosts (NHH). For 5/51 (9.8%) hBG system genes (e.g., RhD), no NHH had orthologs. This means that RhD is unlikely to be an essential receptor for invasion. For 24/51 (47.1%) hBG system genes, NHH had 4-27 orthologs. For the ABO gene, 15/28 NHH had an ortholog, meaning that this gene is also unlikely to generate an RBC antigen, which is essential for Bm invasion. Our prior research showed that persons with blood type A, B, AB, O, RhD+, and RhD- can all be infected with Bm, supporting our current study's predictions. For 22/51 (43.1%) hBG system genes, orthologs were found in all 28 NHH. Nineteen (37.3%) of these genes encode RBC surface proteins, meaning they are good candidates for generating a receptor needed for Bm invasion. In vitro cultures of Bm, experimental Bm infection of transgenic mice (e.g., a CD44 KO strain), and analyses of Bm patients can reveal further clues as to which RBC antigens may be essential for invasion.

Phylogenetic analysis of a novel Hepatozoon species (Hepatozoon sp. SK3) and an additional yet unknown Hepatozoon species (Hepatozoon sp. BV2) besides H. erhardovae in small rodents from Central Europe

Hepatozoon spp. are tick-borne apicomplexan parasites of terrestrial vertebrates that occur worldwide. Tissue samples from small rodents and their parasitizing fleas were sampled for molecular detection and phylogenetic analysis of Hepatozoon-specific 18S rRNA gene region. After alignment and tree inference the Hepatozoon-sequences retrieved from a yellow-necked mouse (Apodemus flavicollis) placed into a strongly supported single clade demonstrating the presence of a novel species, designated Hepatozoon sp. SK3. The mode of transmission of Hepatozoon sp. SK3 is yet unknown. It is important to note that this isolate may be identical with the previously morphologically described Hepatozoon sylvatici infecting Apodemus spp.; however, no sequences are available for comparison. Furthermore, the previously reported variants Hepatozoon sp. BV1/SK1 and BV2/SK2 were detected in bank voles (Clethrionomys glareolus). It has been suggested that these variants should be identified as Hepatozoon erhardovae leading to the assumption that BV1 and BV2 are paralogous 18S rRNA gene loci of this species. Evidence has also been presented that fleas are vectors of H. erhardovae. In this study, we show with high significance that only the Hepatozoon sp. BV1 variant, but not BV2, infects the studied flea species Ctenophthalmus agyrtes, Ctenophthalmus assimilis, and Megabothris turbidus (p < 0.001). This finding suggests that Hepatozoon sp. BV2 represents an additional species besides H. erhardovae (= Hepatozoon sp. BV1), for which alternative arthropod vectors or non-vectorial modes of transmission remain to be identified. Future studies using alternative molecular markers or genome sequencing are required to demonstrate that BV1/SK1 and BV2/SK2 are different Hepatozoon species.

Hepatozoon (Eucoccidiorida: Hepatozoidae) in wild mammals of the Americas: a systematic review

BACKGROUND

The study of parasites provides insight into intricate ecological relationships in ecosystem dynamics, food web structures, and evolution on multiple scales. Hepatozoon Eucoccidiorida: Hepatozoidae) is a genus of protozoan hemoparasites with heteroxenous life cycles that switch infections between vertebrates and blood-feeding invertebrates. The most comprehensive review of the genus was published 26 years ago, and currently there are no harmonized data on the epizootiology, diagnostics, genotyping methods, evolutionary relationships, and genetic diversity of Hepatozoon in the Americas.

METHODS

Here, we provide a comprehensive review based on the PRISMA method regarding Hepatozoon in wild mammals within the American continent, in order to generate a framework for future research.

RESULTS

11 out of the 35 countries of the Americas (31.4%) had data on Hepatozoon, with Carnivora and Rodentia orders having the most characterizations. Bats, ungulates, and shrews were the least affected groups. While Hepatozoon americanum, H. americanum-like, H. canis, H. didelphydis, H. felis, H. milleri, H. griseisciuri, and H. procyonis correspond to the identified species, a plethora of genospecies is pending for a formal description combining morphology and genetics. Most of the vectors of Hepatozoon in the Americas are unknown, but some flea, mite, and tick species have been confirmed. The detection of Hepatozoon has relied mostly on conventional polymerase chain reaction (PCR), and the implementation of specific real time PCR for the genus needs to be employed to improve its diagnosis in wild animals in the future. From a genetic perspective, the V4 region of the 18S rRNA gene has been widely sequenced for the identification of Hepatozoon in wild animals. However, mitochondrial and apicoplast markers should also be targeted to truly determine different species in the genus. A phylogenetic analysis of herein retrieved 18S ribosomal DNA (rDNA) sequences showed two main clades of Hepatozoon: Clade I associated with small mammals, birds, and herpetozoa, and Clade II associated with Carnivora. The topology of the tree is also reflected in the haplotype network.

CONCLUSIONS

Finally, our review emphasizes Hepatozoon as a potential disease agent in threatened wild mammals and the role of wild canids as spreaders of Hepatozoon infections in the Americas.

Should I Stay or Should I Go? Seasonal Fluctuations of Wood Mouse Populations in Fields Surrounded by Woodlands

The wood mouse Apodemus sylvaticus is common in woodlands and open areas of the Western Palearctic. Despite extensive research, little is known about its population ecology in fields in the Mediterranean area, where the climate involves great seasonal changes in environmental features. Here, we investigated wood mice seasonal fluctuations in the number of captures and population structure by sampling long-fallow fields and woodlands, i.e., oak forest and conifer plantation, in a heterogeneous landscape of central Italy. Mice were live-trapped every two months for three years (23.814 trap-days). The number of captures, mice body weight, and proportion of adult, residents and breeding individuals were analyzed. Mice dynamics changed across seasons and habitats. In fields, we recorded more captures, more reproductive individuals, and fewer non-adults and resident individuals in the warmer months compared to the colder months; mice were heavier in warmer months. During the cold season, the captures and adult proportion in fields were lower than in resource-rich woodlands. Breeding and non-resident mice were more abundant in fields than in woodlands in warmer months. Overall, the seasonal demographic variations we recorded provide evidence that fields can represent a suboptimal habitat in Mediterranean heterogeneous landscapes, acting nonetheless as a source of food resources, cover, and mates for mice in spring-summer.

Screening of Domestic Cats from North-Eastern Hungary for Hepatozoon felis and Cytauxzoon europaeus That Cause Infections in Local Wildcat Populations

Among vector-borne protozoa Hepatozoon felis and Cytauxzoon europaeus are considered emerging species in felids in Europe. To investigate the presence of these two protozoa 127 domestic cats and 4 wildcats were screened by PCRs targeting the 18S rRNA gene of Hepatozoon spp. and piroplasms, as well as the cytb gene of Cytauxzoon spp. The samples were collected inside and outside a region of Hungary, where both protozoan groups are endemic in wildcats. Among domestic cats, one proved to be infected with H. felis. Furthermore, spleen samples of four wildcats were also examined, among which three tested positive for H. felis, and one had co-infection with C. europaeus. Importantly, H. felis from the co-infected wildcat belonged to genogroup II, similarly to H. felis from the positive domestic cat. Based on phylogenetic evidence, this genogroup probably represents a separate species from genogroup I of H. felis, which was hitherto reported from Mediterranean countries in Europe. The two other wildcats also harbored H. felis from genogroup I. Neither Hepatozoon nor Cytauxzoon infections were detected outside the recently discovered endemic region. In conclusion, this study demonstrates for the first time in Europe that H. felis from genogroup II may emerge in free-roaming domestic cats in regions where this protozoan parasite is endemic in wildcats.

Candidatus Neoehrlichia mikurensis and Hepatozoon sp. in voles (Microtus spp.): occurrence and evidence for vertical transmission

Candidatus Neoehrlichia mikurensis (CNM) and Hepatozoon spp. are important vector-borne parasites of humans and animals. CNM is a relatively recently discovered pathogen of humans. Hepatozoon are parasites of reptiles, amphibians and mammals, commonly found in rodents and carnivores worldwide. The present study aimed to determine the prevalence of CNM and Hepatozoon spp. in three species of Microtus and to assess the occurrence of vertical transmission in naturally-infected voles. Molecular techniques were used to detect pathogen DNA in blood and tissue samples of captured voles and their offspring. The prevalence of CNM in the vole community ranged 24-47% depending on Microtus species. The DNA of CNM was detected in 21% of pups from three litters of six infected Microtus dams (two Microtus arvalis and one M. oeconomus) and in 3/45 embryos (6.6%) from two litters of eight CNM-infected pregnant females. We detected Hepatozoon infection in 14% of M. arvalis and 9% of M. oeconomus voles. Hepatozoon sp. DNA was detected in 48.7% of pups from seven litters (6 M. arvalis and 1 M. oeconomus) and in two embryos (14.3%) obtained from one M. arvalis litter. The high prevalence of CNM infections in the Microtus spp. community may be a result of a relatively high rate of vertical transmission among naturally infected voles. Vertical transmission was also demonstrated for Hepatozoon sp. in M. arvalis and M. oeconomus. Our study underlines the significance of alternative routes of transmission of important vector-borne pathogens.

High Prevalence and Genetic Variability of Hepatozoon canis in Grey Wolf (Canis lupus L. 1758) Population in Serbia

Wild canids are globally recognised as hosts and reservoirs of a large number of ecto- and endoparasites. Data that reveal the importance of the grey wolf (Canis lupus L.1758) in the spread of hepatozoonosis are very scarce. There are a large number of different potential host species that can be infected by Hepatozoon canis, but the most common are domestic and wild carnivores, such as dogs, jackals, foxes, and wolves. In this study, the epidemiological significance of the grey wolf as a host for the pathogen was analysed for the first time in Serbia, as well as the genetic variability of H. canis. The presence of H. canis in wolf spleens has been demonstrated using molecular methods. A total of 107 wolf spleen samples from 30 localities in Serbia were analysed. The presence of H. canis was confirmed in 62 (57.94%) individuals from 26 out of 30 localities. According to the analysis, the sampled H. canis sequences were found to be characterised by a certain heterogeneity. Based on five mutated nucleotide sites in the sequences, H. canis could be divided into five sequence types, S1 to S5. The five sequence types can potentially circulate in grey wolf populations as well as among other domestic and wild canids. This study is the first confirmation of the presence of H. canis in grey wolf populations in Serbia. Considering that the role of this vector-borne disease is poorly researched in wild carnivores, it is very important to indicate the role of this species in the circulation of this pathogen in natural ecosystems.