Infection with Paragonimus westermani of boar-hunting dogs in Western Japan maintained via artificial feeding with wild boar meat by hunters

Paragonimiasis

Paragonimiasis is a zoonotic disease caused by lung flukes of the genus Paragonimus. Humans usually become infected by eating freshwater crabs or crayfish containing encysted metacercariae of these worms. However, an alternative route of infection exists: ingestion of raw meat from a mammalian paratenic host. Adult worms normally occur in pairs in cysts in the lungs from which they void their eggs via air passages. The pulmonary form is typical in cases of human infection due to P. westermani, P. heterotremus, and a few other species. Worms may occupy other sites in the body, notably the brain, but lung flukes have made their presence felt in almost every organ. Ectopic paragonimiasis is particularly common when infection is due to members of the P. skrjabini complex. Human paragonimiasis occurs primarily in the tropics and subtropics of Asia, Africa, and the Americas, with different species being responsible in different areas (Table 6.1).

Pseudorabies Virus Associations in Wild Animals: Review of Potential Reservoirs for Cross-Host Transmission

Pseudorabies virus (PRV) has received widespread attention for its potential health effects on humans, wildlife, domestic animals, and livestock. In this review, we focus on PRV dynamics in wildlife, given the importance of wild-origin PRV transmission to domestic and farm animals. Wild boars, pigs, and raccoons can serve as reservoirs of PRV, with viral transmission to domestic livestock occurring via several routes, such as wild herd exposure, contaminated meat consumption, and insect vector transmission. Many endangered feline and canine species can be infected with PRV, with acute disease and death within 48 h. The first confirmed human case of PRV infection in mainland China was reported in 2017. Thus, PRV exhibits potentially dangerous cross-host transmission, which is likely associated with inappropriate vaccination, poor awareness, and insufficient biosecurity. Currently, no vaccine provides full protection against PRV in all animals. Here, we summarize the epidemiology and pathogenesis of PRV infection in wild, domestic, and farmed animals, which may facilitate the design of novel therapeutics and strategies for controlling PRV infection and improving wildlife protection in China.

Distribution of Pseudorabies Virus Antigen in Hunting Dogs with Concurrent Paragonimus westermani Infection

Following isolation of pseudorabies virus (PRV) from two hunting dogs in Oita prefecture, Japan, we investigated the PRV antigen distribution in the tissues of the infected animals. At necropsy, PRV-associated lesions included facial oedema, tonsillar and meningeal congestion, blotchy haemorrhages on the pericardium and mitral valves, and incomplete splenic contraction in one dog, with less prominent findings in the other dog. Multiple pulmonary nodules were seen in both cases, caused by the diploid form of Paragonimus westermani lung flukes, as confirmed by PCR-restriction fragment length polymorphism and gene sequencing analyses. Histological examination revealed that the PRV infection was associated with lesions of non-suppurative encephalitis in the brainstem. PRV antigen was detected in the cerebrum, cerebellum, brainstem, submucosal and myenteric plexuses, and mononuclear cells, mainly in the bone marrow, lymph nodes, tonsils and spleen tissues. There was evidence of PRV dissemination to the brain via the trigeminal or olfactory routes, in addition to possible spread to lymphoid organs via infected mononuclear cells.

Hunting Dogs

Herding and hunting dogs are intense, high-drive dogs that work, and often live, outdoors and in constant or repeated close contact with domestic and wild animals. These dogs are at increased risk for injury and exposure to infectious diseases, toxic substances, and environmental threats. The common practice of feeding or allowing access to raw meat from farm or game animals enhances disease transmission risk. These dogs can be affected by infectious diseases and injurious agents that are rarely encountered in other groups of dogs. In addition, their extreme work ethic may lead to delays in diagnosis.

Transcriptome Analysis Reveals Possible Virulence Factors of Paragonimus proliferus

Objective:

To identify the possible virulence factors (VFs) of P. proliferus.

Methods:

By Illumina HiSeq 4000 RNA-Seq platform, transcriptomes of adult P. proliferus worms were sequenced to predict VFs via screening the homologues of traditional VFs of parasites based on the annotations in the functional databases. Homology analysis was also performed to screen homologous genes between P. proliferus and other four Paragonimus species (i.e., P. kellicotti, P. skrjabini, P. miyazakii and P. westermani) whose transcriptomes were downloaded from the National Center for Biotechnology Information (NCBI) database, and then the differential-expressed homologous genes (DEHGs) were screened via comparisons of P. proliferus and P. kellicotti, P. skrjabini, P. miyazakii and P. westermani, respectively. Finally, an overlap of the predicted VFs and DEHGs was performed to identify possible key VFs that do not only belong to the predicted VFs but also DEHGs.

Results:

A total of 1,509 genes of P. proliferus homologous to traditional VFs, including surface antigens (SAGs), secreted proteins (SPs), ATP-Binding Cassette (ABC) Transporters, actin-related proteins (ARPs), aminopeptidases (APases), glycoproteins (GPs), cysteine proteases (CPs), and heat shock proteins (HSPs), were identified. Meanwhile, homology analysis identified 6279 DEHGs among the five species, of which there were 48 DEHGs being mutually differentialexpressed among the four pairs of comparisons, such as MRP, Tuba 3, PI3K, WASF2, ADK, Nop56, DNAH1, PFK-2/FBPase2, Ppp1r7, SSP7. Furthermore, the overlap between the predicted VFs and DEHGs showed 97 genes of the predicted VFs that simultaneously belonged to DEHGs. Strikingly, of these 97 genes, only 26, including Chymotrypsin, Leucine APases, Cathepsin L, HSP 70, and so on, were higher expressed in P. proliferus while all the remaining were lower expressed than in the four other species.

Conclusions:

This work provides a fundamental context for further studies of the pathogenicity of P. proliferus. Most of the predicted VFs which simultaneously belonged to DEHGs were lower expressed in P. proliferus.

Differentially Expressed Homologous Genes Reveal Interspecies Differences of Paragonimus Proliferus based on Transcriptome Analysis

Paragonimus proliferus (P. proliferus), one of 46 Paragonimus species registered in the National Center for Biotechnology Information database, may be much more widely distributed in Southeast Asia than previously thought, as its reported natural foci have increased in the past decades. However, very little is known about its molecular biology, especially at the transcriptome level. For the first time, the transcriptome of this species was sequenced and compared with four other common Paragonimus species, namely Paragonimus skrjabini, Paragonimus kellicotti, Paragonimus miyazakii, and Paragonimus westermani, to predict homologous genes and differentially expressed homologous genes to explore interspecies differences of Paragonimus proliferus. A total of 7393 genes were found to be significantly differentially expressed. Of these, 49 were considered to be core genes because they were differentially expressed in all four comparison groups. Annotations revealed that these genes were related mainly to "duplication, transcription, or translation", energy or nutrient metabolism, and parasitic growth, proliferation, motility, invasion, adaptation to the host, or virulence. Interestingly, a majority (5601/7393) of the identified genes, and in particular the core genes (48/49), were expressed at lower levels in P. proliferus. The identified genes may play essential roles in the biological differences between Paragonimus species. This work provides fundamental background information for further research into the molecular biology of P. proliferus.

A case of group infections with Paraginimus species in Henan, Central China

In July of 2012, mass infections with Paragonimus species were detected in the Henan province sickening 11 of 51 people. In May 2011, these individuals had participated in an excursion during which freshwater crabs were caught and served after being toasted. Before the group infections with Paraginimus species was confirmed, 5 of the 11 patients had been misdiagnosed as tuberculosis (TB) and treated with an anti-TB drug regimen for six months. The most common and typical manifestations were eosinophilia (11/11, 100%) and pulmonary manifestations including, among others, stethalgia and cough (7/11 63.6%). Sero-examination revealed that all 11 patients were seropositive for Paragonimus species. Surprisingly, in our case, one patient presented with hemoptysis and eggs in respiratory secretions, and this is the first time P. skrjabini eggs are detected in the sputum of a patient from the Henan province. Paragonimus metacercariae were collected from 6 of 11 (54.5%) crabs caught at the infection site and were identified as Paraginiumus skrjabini by morphological and molecular examinations. Epidemiological and laboratory evidence confirmed that this is a case of group infection with P. skrjabini. As one of the most neglected tropical diseases (NTD), paragonimiasis should be differentiated diagnosed from TB to avoid the delay of treatment. To our knowledge, this is the second report of a case of group infections with Paraginimus species in Henan, Central China. The first case was reported in 1995. As a kind of food-borne parasitic disease, paragonimiasis should be included in the public health education agenda.

Paragonimus and paragonimiasis in Asia: An update

Paragonimiasis, or lung fluke disease, is a typical food-borne parasitic zoonosis caused by infection with trematodes belonging to the genus Paragonimus. More than 50 species of Paragonimus have been reported throughout the world, of which seven valid species infect humans, an estimated one million people annually worldwide. Among the seven species, P. westermani, P. heterotremus, and P. skrjabini/P. s. miyazakii, distributed in Asia, are the most important species as the cause of paragonimiasis. Humans acquire infection through the ingestion of raw, pickled or undercooked freshwater crustaceans, 2nd intermediate hosts, or consuming raw meat of wild boar or deer, paratenic hosts. Infections often occur clustered in foci where dietary habits allow transmission of the parasites. Paragonimiasis typically causes a subacute to chronic inflammatory disease of the lungs. The symptoms, including chronic cough, chest pain, dyspnea and hemoptysis, mimic those of tuberculosis and lung cancer. Serologic tests are commonly used for the diagnosis of paragonimiasis, and Praziquantel is the treatment of choice. In this review, the current status of Paragonimus and paragonimiasis in Asia is outlined based on the latest information and findings. We also summarize current trends of paragonimiasis in Japan, which is one of the most endemic area of paragonimiasis in the world, for the better understanding and control of paragonimiasis.

First report of Paragonimus skrjabini miyazakii metacercariae in Geothelphusa dehaani (Sawagani) occurring in Iwate Prefecture, Japan

Paragonimiasis is an important food-borne zoonosis caused by Paragonimus flukes and is endemic to western Japan. However, there have been few epidemiological studies in the Tohoku district of northeastern Japan. In this study, Paragonimus metacercariae (mc) was detected in Geothelphusa dehaani (Japanese freshwater crab or Sawagani) in Iwate Prefecture. Out of the 207 Sawagani collected from 35 localities, 12 individuals from six localities were infected with Paragonimus mc. The mc were identified as P. skrjabini miyazakii based on the sequences of nuclear ribosomal internal transcribed spacer 2 and mitochondrial cytochrome c oxidase I. This is the first report of P. s. miyazakii mc infection in Sawagani in Iwate Prefecture.

Paragonimiasis

Paragonimiasis is a zoonotic disease caused by lung flukes of the genus Paragonimus. Humans usually become infected by eating freshwater crabs or crayfish containing encysted metacercariae of these worms. However, an alternative route of infection exists: ingestion of raw meat from a mammalian paratenic host. Adult worms normally occur in pairs in cysts in the lungs from which they void their eggs via air passages. The pulmonary form is typical in cases of human infection due to P. westermani, P. heterotremus, and a few other species (Table 5.1). Worms may occupy other sites in the body, notably the brain, but lung flukes have made their presence felt in almost every organ. Ectopic paragonimiasis is particularly common when infection is due to members of the P. skrjabini complex (Table 5.1). Human paragonimiasis occurs primarily in the tropics and subtropics of Asia, Africa, and the Americas, with different species being responsible in different areas (Table 5.1).