Hepatozoon species infection in wild red squirrels (Sciurus vulgaris) on the Isle of Wight

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.

Molecular detection and characterization of vector-borne agents in common opossums (Didelphis marsupialis) from northeastern Brazil

Opossums are synanthropic marsupials able to interchange among wild, peri-urban and urban environments, playing an epidemiologically important role as hosts for emerging pathogens and ectoparasites of relevance in public health. The present study aimed to detect and molecularly characterize vector-borne agents in a population of common opossums (Didelphis marsupialis) from the Island of São Luís do Maranhão, northeastern Brazil. Of the 45 animals analyzed, one (2.22%) was positive in the nested PCR assay based on the 18S rRNA gene of piroplasmids. The obtained sequence was phylogenetically positioned in a clade containing sequences of Babesia sp. previously detected in Didelphis aurita, Didelphis albiventris and associated ticks from Brazil. Eight (17.77%) samples were positive in PCR for Ehrlichia spp. based on the dsb gene; four samples were sequenced and positioned into a new clade, sister to E. minasensis and Ehrlichia sp. clade detected in Superorder Xenarthra mammals. No samples tested positive in the screening PCR assays based on the 16S rRNA gene of Anaplasma spp. Two samples were positive in the qPCR for Bartonella spp. based on the nuoG gene. Seven animals (15.56%) were positive in the nPCR based on the 16S rRNA gene of hemoplasmas. Of these, three were positive in a PCR based on the 23S rRNA gene. The phylogenies based on both 16S rRNA and 23S rRNA genes corroborated to each other and positioned the sequences in the same clade of hemoplasmas previously detected in D. aurita and D. albiventris sampled in Brazil. Finally, three (6.66%) animals were positive in the PCR for Hepatozoon spp.; the obtained 18S rRNA sequence was positioned into the H. felis clade.The present study showed, for the first time, the circulation of piroplasmids, Hepatozoon spp., Ehrlichia spp., hemoplasmas and Bartonella spp. in D. marsupialis sampled in northeastern Brazil, with description of putative novel genotypes of Ehrlichia and Hepatozoon and copositivity by different vector-borne agents. The present work consolidates the "South American Marsupialia" piroplasmid clade, adding one more genotype of Babesia sp. to this clade.

Diversity of Hepatozoon species in wild mammals and ticks in Europe

BACKGROUND

Hepatozoon spp. are tick-borne parasites causing subclinical to clinical disease in wild and domestic animals. Aim of this study was to determine Hepatozoon prevalence and species distribution among wild mammals and ticks in Europe.

METHODS

Samples of wild mammals and ticks, originating from Austria, Bosnia and Herzegovina, Croatia, Belgium and the Netherlands, were tested with PCR to amplify a ~ 670-bp fragment of the small subunit ribosomal RNA gene.

RESULTS

Of the 2801 mammal samples that were used for this study, 370 (13.2%) tested positive. Hepatozoon canis was detected in samples of 178 animals (3 Artiodactyla, 173 Carnivora, 1 Eulipotyphia, 1 Lagomorpha), H. martis in 125 (3 Artiodactyla, 122 Carnivora), H. sciuri in 13 (all Rodentia), Hepatozoon sp. in 47 (among which Hepatozoon sp. Vole isolate, all Rodentia) and H. ayorgbor in 4 (all Rodentia). Regarding origin, 2.9% (6/208) tested positive from Austria, 2.8% (1/36) from Bosnia and Herzegovina, 14.6% (173/1186) from Croatia and 13.9% (190/1371) from Belgium/the Netherlands. Of the 754 ticks collected, 0.0% (0/35) Hyalomma sp., 16.0% (4/25) Dermacentor spp., 0.0% (0/23) Haemaphysalis spp., 5.3% (24/50) Ixodes and 1.4% (3/221) Rhipicephalus spp. tested positive for Hepatozoon (4.2%; 32/754), most often H. canis (n = 22).

CONCLUSIONS

Hepatozoon canis is most present in mammals (especially in Carnivora such as gray wolves and golden jackals) and ticks, followed by H. martis, which was found merely in stone martens and pine martens. None of the rodent-associated Hepatozoon spp. were detected in the ticks, suggesting the possible implication of other arthropod species or non-vectorial routes in the transmission cycle of the hemoprotozoans in rodents. Our findings of H. canis in ticks other than R. sanguineus add to the observation that other ticks are also involved in the life cycle of Hepatozoon. Now that presence of Hepatozoon has been demonstrated in red foxes, gray wolves, mustelids and rodents from the Netherlands and/or Belgium, veterinary clinicians should be aware of the possibility of spill-over to domestic animals, such as dogs.

Novel Ehrlichia and Hepatozoon genotypes in white-eared opossums (Didelphis albiventris) and associated ticks from Brazil

White-eared opossums (Didelphis albiventris) are well adapted to anthropized areas. The increased contact with domestic animals and humans mediates the transmission of arthropod-borne pathogens. Despite the worldwide occurrence of tick-borne Anaplasmataceae and Hepatozoidae species in a variety of vertebrates, few studies reported serological evidence or molecular detection of theses agentes in marsupials. Up to now, while Ehrlichia/Anaplasma spp. have only been detected in marsupials from Brazil, Hepatozoon spp. have been reported in marsupials from Chile, Australia and Brazil. The present work aimed to investigate, using molecular techniques and blood smear analysis, the presence of Ehrlichia spp., Anaplasma spp., and Hepatozoon sp. in the blood and ticks collected from D. albiventris in urban forest fragments from midwestern Brazil. Between May and December 2017, 43 D. albiventris (27 males and 16 females) were captured for blood and tick collection in the city of Campo Grande, state of Mato Grosso do Sul, midwestern Brazil. Ticks (46 Amblyomma dubitatum nymphs and 24 Amblyomma spp. larvae) were collected from 14 out 43 (32.5%) of the white-eared opossums. Panoptic-stained blood smears were performed using peripheral blood (tail tip) of the captured opossums. DNA extracted from blood and tick samples were subjected to PCR/qPCR assays for Anaplasmataceae agents (rrs, gltA, groEL, sodB, and dsb genes, and 23S-5S intergenic region) and Hepatozoon spp. (18S rRNA gene), followed by Sanger sequencing, BLASTn and phylogenetic analyses. An inclusion resembling Ehrlichia morulae was found in a white-eared opossum's monocyte from a blood smear stained with Panoptic. Five (11.63% [5/43]) white-eared opossums' blood samples and 7 (25% [7/28]) tick samples (2 pools of Amblyomma spp. larvae and 5 pools of A. dubitatum nymphs) were positive for Anaplasmataceae via a PCR assay targeting the conserved rrs gene. Phylogenetic analysis based on the rrs gene positioned three sequences obtained from opossums and ticks together as a subclade within the Ehrlichia canis clade. However, all samples were negative in a qPCR assay specific for E. canis based on the dsb gene. Phylogenetic analyses positioned the gltA and 23S-5S ITS sequences obtained from opossums' blood samples in a separate clade from the other validated Ehrlichia species. One (2.3% [1/43]) opossum blood sample was positive for the 18S rRNA gene of Hepatozoon sp. The phylogenetic analysis positioned the Hepatozoon sp. sequence obtained from a D. albiventris specimen in a clade with a sequence previously detected in a black storm petrel (Oceanodroma melania) from Mexico. All the other sequences of Hepatozoon sp. previously detected in marsupials from Brazil were positioned in a separated clade. The present work showed the occurrence of putative novel genotypes of Ehrlichia sp. and Hepatozoon sp. in white-eared opossums and associated A. dubitatum ticks from midwestern Brazil.

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

Among the Apicomplexa parasites, Hepatozoon spp. have been mainly studied in domestic animals and peri-urban areas. The epidemiology of Hepatozoon spp. is poorly investigated in natural systems and wild hosts because of their scarce veterinary and economic relevance. For most habitats, the occurrence of these parasites is unknown, despite their high ecosystemic role. To fill this gap for alpine small mammals, we applied molecular PCR-based methods and sequencing to determine the Hepatozoon spp. in 830 ear samples from 11 small mammal species (i.e., Apodemus, Myodes, Chionomys, Microtus, Crocidura and Sorex genera) live-trapped during a cross-sectional study along an altitudinal gradient in the North-Eastern Italian Alps. We detected Hepatozoon spp. with an overall prevalence of 35.9%. Two species ranging from 500 m a.s.l. to 2500 m a.s.l. were the most infected: My. glareolus, followed by Apodemus spp. Additionally, we detected the parasite for the first time in another alpine species: C. nivalis at 2000–2500 m a.s.l. Our findings suggest that several rodent species maintain Hepatozoon spp. along the alpine altitudinal gradient of habitats. The transmission pathway of this group of parasites and their role within the alpine mammal community need further investigation, especially in consideration of the rapidly occurring environmental and climatic changes.

Hepatozoon in Eurasian red squirrels Sciurus vulgaris, its taxonomic identity, and phylogenetic placement

Adeleorid apicomplexan parasites of the genus Hepatozoon Miller, 1908 are broadly distributed among the rodents. Broader molecular data on Hepatozoon from Palaearctic squirrels are necessary for evaluation of diversity and origin of Hepatozoon in Eurasian red squirrel Sciurus vulgaris populations, considering ongoing invasion by Gray squirrel S. carolinensis. Our report brings a set of molecular data from a population of S. vulgaris in the Czech Republic, non-invaded by any invasive squirrel species. Cadavers of 41 Eurasian red squirrels were examined using nested PCR targeting 18S rRNA gene; 30 animals tested positive for the presence of Hepatozoon spp. DNA in at least one tissue. Phylogenetic analysis of obtained sequence types revealed relatedness to sequences of Hepatozoon sp. from S. vulgaris from Spain and the Netherlands, forming a sister clade to Hepatozoon isolates from other European rodents. The fact that all available 18S rRNA gene sequences form a monophyletic clade is interpreted as a presence of a single Hepatozoon species in S. vulgaris in continental Europe, most probably Hepatozoon sciuri. The presented molecular data on the Hepatozoon from European squirrels provides a basis for future studies on possible exchange of Hepatozoon species between Eurasian red and gray squirrels.

Molecular detection of Hepatozoon spp. in non-hematophagous bats in Brazil

Even though Hepatozoon spp. has been molecularly detected in several wild animals in Brazil, there is no report on the occurrence of Hepatozoon spp. DNA in bats in Brazil. This study aimed at detecting Hepatozoon, in addition to ectoparasites, in non-hematophagous bats sampled in central-western Brazil using blood smears, hematoxylin-eosin (HE)-staining liver/spleen preparations and molecular and phylogenetic techniques. A total of 135 spleen, 127 liver, and 133 blood samples were collected from 135 non-hematophagous bats from 12 different species in two different sites in Campo Grande, Mato Grosso do Sul state, in the Brazilian Cerrado region. Spleen and blood DNA samples were submitted to two conventional PCR protocols for Hepatozoon spp. based on 18S rRNA. No Hepatozoon spp. gamonts or meronts were observed in blood smears and HE-stained-liver preparations, respectively. While none of the spleen samples was positive for Hepatozoon spp. in the PCR assays, 5 (3 %) blood samples contained 18S rRNA Hepatozoon DNA, including 2/37 (5 %) Artibeus lituratus, 2/32 (6 %) A. planirostris, and 1/23 (4 %) Platyrrhinus lineatus. Out of 5 bats positive for Hepatozoon spp., 3 were parasitized by either Macronyssidae/Spinturnicidae mites or Streblidae flies. BLAST analysis showed that the sequences detected in bats had >99 % identity with Hepatozoon sequences detected in amphibians and reptiles from Brazil, including Hepatozoon caimani detected in Caiman crocodilus. The phylogenetic inferences estimated by the Maximum Likelihood and Bayesian methods clustered the Hepatozoon sequences detected in Brazilian bats with those detected in reptiles and amphibians.

Hepatozoon canis in three imported dogs: a new tickborne disease reaching the United Kingdom

An increasing number of non-endemic vectorborne pathogens have been described in dogs imported to the UK in the past two decades. Recently, an outbreak of canine babesiosis in south-east England has raised veterinary awareness with regard to the impact of such diseases on the UK canine population. Canine hepatozoonosis, caused by Hepatozoon canis and transmitted by the ingestion of Rhipicephalus sanguineus ticks, is widespread in the Mediterranean basin. Herein we describe the first three molecularly confirmed clinical cases of canine hepatozoonosis in dogs imported into the UK. Veterinarians in the UK should be aware of H canis as a potential infection in imported dogs, especially in the face of the expanding distribution of R sanguineus ticks in Europe.

Causes of mortality and pathological lesions observed post-mortem in red squirrels (Sciurus vulgaris) in Great Britain

BACKGROUND

The red squirrel population in Great Britain has declined dramatically in recent decades, principally due to squirrelpox. Concern exists that red squirrels may become extinct nationally and, as there has been limited research in to diseases other than squirrelpox, this study aimed to identify additional causes of mortality.

RESULTS

Post-mortem examinations on 163 red squirrels found dead on Isle of Wight (IoW) England, in Scotland and at other locations in Great Britain showed that 41.7% (n = 68) were killed by road traffic and 9.2% (n = 15) by predators, principally domestic cats and dogs. The overall male/female ratio was 1.08/1. Fleas were recorded on 34.9% of IoW squirrels and on 43.8% of Scottish squirrels but sucking lice and ixodid ticks were only seen on Scottish squirrels. Bacterial infections were significant, particularly in association with respiratory disease (n = 16); two squirrels died of Bordetella bronchiseptica bronchopneumonia. Cases of fatal exudative dermatitis (n = 5) associated with a lukM-positive clone of Staphylococcus aureus occurred only on the IoW. Toxoplasmosis (n = 12) was also confined to IoW where it was responsible for almost one tenth (9.5%) of all deaths. Hepatozoonosis was common, especially in IoW squirrels, but was not considered a primary cause of mortality. Hepatic capillariasis affected four IoW squirrels and one from Scotland. Fungal infections included oral candidiasis, adiaspiromycosis and pulmonary phaeohyphomycosis. Neoplastic conditions diagnosed were: pulmonary carcinoma, gastric spindle cell tumour, renal papillary adenoma and trichoepithelioma. Epidermal hyperplasia of unknown aetiology was seen in squirrels showing crusty lesions of the ear pinnae on IoW (n = 3) and Brownsea Island (n = 1), associated in two cases with cutaneous wart-like growths. Miscellaneous diagnoses included chylothorax, electrocution, intussusception, suspected cholecalciferol rodenticide poisoning and foetal death and mummification. No cases of squirrelpox were diagnosed.

CONCLUSIONS

Red squirrels in Britain suffer premature or unnatural mortality due to a number of conditions in addition to squirrelpox, many of which result, directly or indirectly, from human activities: road traffic trauma, pet predation, toxoplasmosis, trap injuries, rodenticide poisoning and electrocution accounted for 61% of all recorded mortality in this study. Red squirrels are also affected by several diseases of unknown aetiology which merit further research.

Epidemiological and postmortem findings in 262 red squirrels (Sciurus vulgaris) in Scotland, 2005 to 2009

Postmortem and virological examinations for squirrelpox virus (SQPV) were carried out on 262 red squirrels (Sciurus vulgaris) found dead or moribund in Scotland between September 2005 and July 2009, to determine the likely causes of death and highlight factors that might be threats to the red squirrel population. Most of the squirrels were submitted from Dumfries and Galloway, and 71 per cent of them were adults. Road traffic accidents, squirrelpox, trauma or starvation were responsible for death in a large proportion (73 per cent) of the squirrels. Thin or emaciated body condition was associated with deaths resulting from pneumonia SQPV infection and starvation, and with the presence of external parasites. There were differences between age groups with regard to the cause of death; a large proportion of juveniles died of starvation, whereas a large proportion of subadults and adults died in road traffic accidents. SQPV infection was associated with the presence of external parasites, but was not associated with the sex of the animals.