Haemogregarines and Criteria for Identification

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.

Description of an intramonocytic haemoparasite, Hepatozoon lainsoni sp. nov. (Apicomplexa: Adeleorina: Hepatozoidae), infecting Ameiva ameiva lizard (Reptilia: Squamata: Teiidae) in northern Brazil

Haemogregarine (Apicomplexa: Adeleorina) parasites are considered to be the most common and widespread haemoparasites in reptiles. The genus Hepatozoon (Apicomplexa: Adeleorina: Hepatozoidae) can be found parasitizing a broad range of species and, in reptiles, they infect mainly peripheral blood erythrocytes. The present study detected and characterized a haemogregarine isolated from the lizard species, Ameiva ameiva, collected from the municipality of Capanema, Pará state, north Brazil. Blood smears and imprints from lungs, brain, heart, kidney, liver, bone marrow and spleen were observed using light microscopy and the parasite was genetically identified by molecular analysis. Morphological, morphometric and molecular data were obtained. Parasite gamonts were found in 49.5% (55/111) of the blood smears from A. ameiva, and were characterized as oval, averaging 12.0 ± 0.8 × 5.9 ± 0.6 μm2 in size, which displaced the nuclei of parasitized monocytes laterally. Parasite forms resembling immature gamonts were observed in the spleen and bone marrow of the lizards. Furthermore, phylogenetic analyses of 18S rRNA sequences did not reveal gene similarity with other Hepatozoon spp. sequences from reptiles. Thus, morphological and molecular analyses have identified a new species of Hepatozoon parasite, Hepatozoon lainsoni sp. nov., which infects monocytes of the A. ameiva lizard.

Molecular Survey of Hepatozoon canis Infection in Domestic Dogs from Sardinia, Italy

Tick-borne protozoans of the genus Hepatozoon have been associated with infections of domestic and wild animals over the world. The occurrence of these apicomplexan agents in Sardinia has been poorly explored so far. In this study, the occurrence of Hepatozoon spp. has been investigated in domestic dogs from nine cities of Sardinia, Italy. Blood samples from each dog were collected and tested molecularly for the presence of Hepatozoon and Babesia/Theileria DNAs. Out of fifty-one dogs, nine were positive for Hepatozoon species based on the molecular detection of the parasite in blood samples. The phylogenetic relationships of strains detected here were also established. The PCR for amplification of the 18S rRNA fragment gene of Babesia/Theileria spp. did not give amplicons in any of the analyzed samples. Our results report the first molecular confirmation of Hepatozoon canis in Sardinian pet dogs and contribute to better understand the presence of these protozoans on the island. This study highlights the importance of recognizing and predicting the risk levels for the canine population, thus increasing the development of specific control measures. Also, since the distribution of hepatozoonosis is closely related to that of the definitive tick host, Rhipicephalus sanguineus, more accurate studies on Rhipicephalus ticks will be needed due to increasing the epidemiological knowledge of Hepatozoon species on the island.

Discovery of a new Hepatozoon species namely Hepatozoon viperoi sp. nov. in nose-horned vipers in Türkiye

Although Hepatozoon spp. remains the most prevalent intracellular protozoa infecting snakes, it was reported only in a few snake species of the Colubridae family in Türkiye. Moreover, studies on these hemoparasites are not available in venomous nose-horned vipers from Türkiye. In this study, we investigated Hepatozoon spp. in three individual Vipera ammodytes using morphological and molecular methods. Our results were positive for intraerythrocytic Hepatozoon spp. gamonts in all three snakes, exhibiting low parasitemia. The microscopic findings were further confirmed through molecular data. A genus-specific PCR assay targeting the 18S rRNA gene region of Hepatozoon spp., was performed using HemoF/HemoR and Hep300/Hep900 primers. The obtained sequences were concatenated and used in phylogenetic analyses in comparison with different Hepatozoon species. Although our (OP377741) isolate was separated into a different branch, it was clustered with the isolates of H. massardi (KC342526), H. cevapii (KC342525), and H. annulatum (ON262426) from Brazilian snakes. Moreover, gene similarity and pair-wise distance between our isolate and other Hepatozoon species infecting snakes were found to be 89.30-98.63% and 0.009-0.077, respectively. Hence, we reported a new species of Hepatozoon, namely Hepatozoon viperoi sp. nov. infecting V. ammodytes. Since the literature does not indicate the existence of such a Hepatozoon species in V. ammodytes in different countries, our data may contribute to the expanding knowledge of Hepatozoon species in snakes, providing new insights into the biodiversity of the haemogregarine protozoan parasite.

Molecular Screening of Haemogregarine Hemoparasites (Apicomplexa: Adeleorina: Haemogregarinidae) in Populations of Native and Introduced Pond Turtles in Eastern Europe

Haemogregarines (Apicomplexa: Adeleorina) are the most common and widespread reptilian blood parasites. Haemogregarina stepanowi was the first haemogregarine described from a reptile, the European pond turtle Emys orbicularis, and initial assessments indicated it was widespread across different pond turtle host species across much of Europe, the Middle East and North Africa. However, recent molecular assessments have indicated the presence of multiple genetically distinct forms in North Africa and the Iberian Peninsula, and extensive mixed infections which may be associated with a negative impact on the hosts. Here, we screened two native species, E. orbicularis and Mauremys rivulata, and the introduced Trachemys scripta from Serbia and North Macedonia for haemogregarines by amplifying and sequencing part of the 18S rRNA gene of these parasites, and used a standard DNA barcoding approach to identify leeches, the final host, attached to pond turtles. Our results again demonstrate the occurrence of considerable diversity of parasites in the analysed pond turtle species, and that T. scripta are likely infected by local haemogregarine parasites, and not those that are found in its native range. Leeches were identified as Placobdella costata, part of a lineage from Northern Europe. Mixed infections within pond turtles were again common. Current haemogregarine taxonomy does not reflect the genetic diversity identified, and a full taxonomic reassessment is needed.

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.

Sexual Development in Non-Human Parasitic Apicomplexa: Just Biology or Targets for Control?

Simple Summary

Cellular reproduction is a key part of the apicomplexan life cycle, and both mitotic (asexual) and meiotic (sexual) cell divisions produce new individual cells. Sexual reproduction in most eukaryotic taxa indicates that it has had considerable success during evolution, and it must confer profound benefits, considering its significant costs. The phylum Apicomplexa consists of almost exclusively parasitic single-celled eukaryotic organisms that can affect a wide host range of animals from invertebrates to mammals. Their development is characterized by complex steps in which asexual and sexual replication alternate and the fertilization of a macrogamete by a microgamete results in the formation of a zygote that undergoes meiosis, thus forming a new generation of asexual stages. In apicomplexans, sex is assumed to be induced by the (stressful) condition of having to leave the host, and either gametes or zygotes (or stages arising from it) are transmitted to a new host. Therefore, sex and meiosis are linked to parasite transmission, and consequently dissemination, which are key to the parasitic lifestyle. We hypothesize that improved knowledge of the sexual biology of the Apicomplexa will be essential to design and implement effective transmission-blocking strategies for the control of the major parasites of this group.

Abstract

The phylum Apicomplexa is a major group of protozoan parasites including gregarines, coccidia, haemogregarines, haemosporidia and piroplasms, with more than 6000 named species. Three of these subgroups, the coccidia, hemosporidia, and piroplasms, contain parasites that cause important diseases of humans and animals worldwide. All of them have complex life cycles involving a switch between asexual and sexual reproduction, which is key to their development. Fertilization (i.e., fusion of female and male cells) results in the formation of a zygote that undergoes meiosis, forming a new generation of asexual stages. In eukaryotes, sexual reproduction is the predominant mode of recombination and segregation of DNA. Sex is well documented in many protist groups, and together with meiosis, is frequently linked with transmission to new hosts. Apicomplexan sexual stages constitute a bottleneck in the life cycle of these parasites, as they are obligatory for the development of new transmissible stages. Consequently, the sexual stages represent attractive targets for vaccination. Detailed understanding of apicomplexan sexual biology will pave the way for the design and implementation of effective transmission-blocking strategies for parasite control. This article reviews the current knowledge on the sexual development of Apicomplexa and the progress in transmission-blocking vaccines for their control, their advantages and limitations and outstanding questions for the future.

Emerging and Re-Emerging Diseases: Novel Challenges in Today's World or More of the Same?

More than 61% of all human pathogens are zoonotic, representing 75% of all emerging pathogens during the past decade. Albeit significant technological leaps in diagnostics development and disease surveillance, zoonotic emerging infectious diseases are evermore a matter of concern, particularly in modern days where global warming keeps providing ideal climatic conditions to the introduction of exotic infectious agents or disease vectors in new territories. Worryingly, the 2019 novel coronavirus epidemic acts as an extreme reminder of the role animal reservoirs play in public health, accounting for over 4,200,000 deaths worldwide until today. In this Special Issue, we approach a myriad of zoonotic infectious diseases and their complex mechanisms. This Special Issue is composed of three reviews on zoonotic diseases of African Lions, hemogregarine classification, and hepatitis E virus in Brazil, followed by one letter and one opinion piece that broadens the spectrum of disease emergence to mechanistic aspects of emerging non-communicable diseases. The Special Issue is completed by six research papers covering a wide array of emerging and re-emerging diseases of poultry, bovine, poultry and tortoises, of various nature such as parasitic, bacterial, and viral. This is a brief but assertive collection that showcases the need to address health at the animal-human-environment interface, in a One Health perspective.