Differential Disease Susceptibilities in Experimentally Reptarenavirus-Infected Boa Constrictors and Ball Pythons

A Multiplex RT-PCR Method for the Detection of Reptarenavirus Infection

Reptarenaviruses cause Boid Inclusion Body Disease (BIBD), a fatal disease of boid snakes with an economic and ecological impact, as it affects both captive and wild constrictor snakes. The clinical picture of BIBD is highly variable but often only limited. Intracytoplasmic inclusion bodies (IB), which develop in most cell types including blood cells, are the pathognomonic hallmark of BIBD; their detection represents the diagnostic gold standard of the disease. However, IBs are not consistently present in clinically healthy reptarenavirus carriers, which can, if undetected, lead to and maintain the spread of the disease within and between snake populations. Sensitive viral detection tools are required for screening and control purposes; however, the genetic diversity of reptarenaviruses hampers the reverse transcription (RT) PCR-based diagnostics. Here, we describe a multiplex RT-PCR approach for the molecular diagnosis of reptarenavirus infection in blood samples. The method allows the detection of a wide range of reptarenaviruses with the detection limit reaching 40 copies per microliter of blood. Using 245 blood samples with a reference RT-PCR result, we show that the technique performs as well as the segment-specific RT-PCRs in our earlier studies. It can identify virus carriers and serve to limit reptarenavirus spreading in captive snake collections.

Molecular characterization of a reptarenavirus detected in a Colombian Red-Tailed Boa (Boa constrictor imperator)

The global decline in biodiversity is a matter of great concern for members of the class Reptilia. Reptarenaviruses infect snakes, and have been linked to various clinical conditions, such as Boid Inclusion Body Disease (BIBD) in snakes belonging to the families Boidae and Pythonidae. However, there is a scarcity of information regarding reptarenaviruses found in snakes in both the United States and globally. This study aimed to contribute to the understanding of reptarenavirus diversity by molecularly characterizing a reptarenavirus detected in a Colombian Red-Tailed Boa (Boa constrictor imperator). Using a metagenomics approach, we successfully identified, and de novo assembled the whole genomic sequences of a reptarenavirus in a Colombian Red-Tailed Boa manifesting clinically relevant symptoms consistent with BIBD. The analysis showed that the Colombian Red-Tailed Boa in this study carried the University of Giessen virus (UGV-1) S or S6 (UGV/S6) segment and L genotype 7. The prevalence of the UGV/S6 genotype, in line with prior research findings, implies that this genotype may possess specific advantageous characteristics or adaptations that give it a competitive edge over other genotypes in the host population. This research underscores the importance of monitoring and characterizing viral pathogens in captive and wild snake populations. Knowledge of such viruses is crucial for the development of effective diagnostic methods, potential intervention strategies, and the conservation of vulnerable reptilian species. Additionally, our study provides valuable insights for future studies focusing on the evolutionary history, molecular epidemiology, and biological properties of reptarenaviruses in boas and other snake species.

Reptarenavirus S Segment RNA Levels Correlate with the Presence of Inclusion Bodies and the Number of L Segments in Snakes with Reptarenavirus Infection-Lessons Learned from a Large Breeding Colony

Reptarenaviruses cause boid inclusion body disease (BIBD), a fatal disease particularly impacting captive boa constrictor collections. The development of cytoplasmic inclusion bodies (IBs) comprising reptarenavirus nucleoprotein (NP) in many cell types of affected snakes is characteristic of BIBD. However, snakes can harbor reptarenaviruses without showing IBs, hence representing carriers and a potential source of transmission. The RNA genome of reptarenaviruses comprises a small (S) and a large (L) segment, and the snakes with BIBD commonly carry a swarm of reptarenavirus segments. To design sensitive and reliable tools for the diagnosis of reptarenavirus infection in snake colonies, we used metatranscriptomics to determine the reptarenavirus segments present in a large boa constrictor breeding colony. The analysis identified one reptarenavirus S segment and three L segments in the colony. The sequence data served to design real-time reverse transcription-PCR (RT-PCR) targeting the found S segment. This allowed us to identify all infected animals and to quantify the S segment RNA levels, which we found to correlate with the presence of IBs. We further found a positive correlation between the number of L segments and the S segment RNA level, which could suggest that L segment excess also contributes to the IB formation. Information on cohousing of the snakes showed a clear association of reptarenavirus infection with cohousing in general and cohousing with infected animals. Information on breeding and offspring confirmed that vertical transmission occurred. Furthermore, our data suggest that some animals might be able to clear the infection or at least exhibit transient or intermittent viremia. IMPORTANCE Boid inclusion body disease (BIBD) is caused by reptarenavirus infection, and while reptarenavirus nucleoprotein is the main component of the inclusion bodies (IBs) characteristic of BIBD, not all reptarenavirus-infected snakes demonstrate IBs in their cells. Identification of infected individuals is critical for controlling the spread of the disease; however, the genetic divergence of reptarenaviruses complicates reverse transcription-PCR (RT-PCR)-based diagnostics. Here, we tested a next-generation-sequencing-based approach to establish a tailored "colony-specific" set of diagnostic tools for the detection of reptarenavirus small (S) and large (L) genome segments. With this approach, we could demonstrate that an S-segment-specific RT-PCR is highly effective in identifying the infected individuals. We further found the S segment RNA level to positively correlate with the presence of IBs and the number of L segments, which could direct future studies to identify the BIBD pathogenetic mechanisms.

Boid Inclusion Body Disease Is Also a Disease of Wild Boa Constrictors

Reptarenaviruses cause boid inclusion body disease (BIBD), a potentially fatal disease, occurring in captive constrictor snakes boas and pythons worldwide. Classical BIBD, characterized by the formation of pathognomonic cytoplasmic inclusion bodies (IBs), occurs mainly in boas, whereas in pythons, for example, reptarenavirus infection most often manifests as central nervous system signs with limited IB formation. The natural hosts of reptarenaviruses are unknown, although free-ranging/wild constrictor snakes are among the suspects. Here, we report BIBD with reptarenavirus infection in indigenous captive and wild boid snakes in Costa Rica using histology, immunohistology, transmission electron microscopy, and next-generation sequencing (NGS). The snakes studied represented diagnostic postmortem cases of captive and wild-caught snakes since 1989. The results from NGS on archival paraffin blocks confirm that reptarenaviruses were already present in wild boa constrictors in Costa Rica in the 1980s. Continuous sequences that were de novo assembled from the low-quality RNA obtained from paraffin-embedded tissue allowed the identification of a distinct pair of reptarenavirus S and L segments in all studied animals; in most cases, reference assembly could recover almost complete segments. Sampling of three prospective cases in 2018 allowed an examination of fresh blood or tissues and resulted in the identification of additional reptarenavirus segments and hartmanivirus coinfection. Our results show that BIBD is not only a disease of captive snakes but also occurs in indigenous wild constrictor snakes in Costa Rica, suggesting boa constrictors to play a role in natural reptarenavirus circulation. IMPORTANCE The literature describes cases of boid inclusion body disease (BIBD) in captive snakes since the 1970s, and in the 2010s, others and ourselves identified reptarenaviruses as the causative agent. BIBD affects captive snakes globally, but the origin and the natural host of reptarenaviruses remain unknown. In this report, we show BIBD and reptarenavirus infections in two native Costa Rican constrictor snake species, and by studying archival samples, we show that both the viruses and the disease have been present in free-ranging/wild snakes in Costa Rica at least since the 1980s. The diagnosis of BIBD in wild boa constrictors suggests that this species plays a role in the circulation of reptarenaviruses. Additional sample collection and analysis would help to clarify this role further and the possibility of, e.g., vector transmission from an arthropod host.

Persistent Reptarenavirus and Hartmanivirus Infection in Cultured Boid Cells

Mammarenaviruses establish a persistent infection in their rodent and bat hosts, and the evidence suggests that reptarenaviruses and hartmaniviruses found in captive snakes act similarly. In snakes, reptarenaviruses cause boid inclusion body disease (BIBD), which is often associated with secondary infections. Snakes with BIBD usually carry more than a single pair of reptarenavirus S and L segments and occasionally demonstrate hartmanivirus coinfection. Here, we reported the generation of cell lines persistently infected with a single or two reptarenavirus(es) and a cell line with persistent reptarenavirus-hartmanivirus coinfection. By RT-PCR we demonstrated that the amount of viral RNA within the persistently infected cells remains at levels similar to those observed following initial infection. Using antibodies against the glycoproteins (GPs) and nucleoprotein (NP) of reptarenaviruses, we studied the levels of viral protein in cells passaged 10 times after the original inoculation and observed that the expression of GPs declines dramatically during persistent infection, unlike the expression of NP. Immunofluorescence (IF) staining served to demonstrate differences in the distribution of NP within the persistently infected compared to freshly infected cells. IF staining of cells inoculated with the viruses secreted from the persistently infected cell lines produced similar NP staining compared to cells infected with a traditionally passaged virus, suggesting that the altered NP expression pattern of persistently infected cells does not relate to changes in the virus. The cell cultures described herein can serve as tools for studying the coinfection and superinfection interplay between reptarenaviruses and studying the BIBD pathogenesis mechanisms.

IMPORTANCE Mammarenaviruses cause a persistent infection in their natural rodent and bat hosts. Reptarenaviruses cause boid inclusion body disease (BIBD) in constrictor snakes, but it is unclear whether snakes are the natural host of these viruses. In this study, we showed that reptarenaviruses established a persistent infection in cultured Boa constrictor cells and that the persistently infected cells continued to produce infectious virus. Our results showed that persistent infection results from subsequent passaging of cells inoculated with a single reptarenavirus, two reptarenaviruses, or even when inoculating the cells with reptarenavirus and hartmanivirus (another arenavirus genus). The results further suggested that coinfection would not result in overt competition between the different reptarenaviruses, thus helping to explain the frequent reptarenavirus coinfections in snakes with BIBD. The established cell culture models of persistent infection could help to elucidate the role of coinfection and superinfection and potential immunosuppression as the pathogenic mechanisms behind BIBD.

Genome-Wide Knockout Screen Identifies Human Sialomucin CD164 as an Essential Entry Factor for Lymphocytic Choriomeningitis Virus

Lymphocytic choriomeningitis virus (LCMV) is a well-studied mammarenavirus that can be fatal in congenital infections. However, our understanding of LCMV and its interactions with human host factors remains incomplete. Here, host determinants affecting LCMV infection were investigated through a genome-wide CRISPR knockout screen in A549 cells, a human lung adenocarcinoma line. We identified and validated a variety of novel host factors that play a functional role in LCMV infection. Among these, knockout of the sialomucin CD164, a heavily glycosylated transmembrane protein, was found to ablate infection with multiple LCMV strains but not other hemorrhagic mammarenaviruses in several cell types. Further characterization revealed a dependency of LCMV entry on the cysteine-rich domain of CD164, including an N-linked glycosylation site at residue 104 in that region. Given the documented role of LCMV with respect to transplacental human infections, CD164 expression was investigated in human placental tissue and placental cell lines. CD164 was found to be highly expressed in the cytotrophoblast cells, an initial contact site for pathogens within the placenta, and LCMV infection in placental cells was effectively blocked using a monoclonal antibody specific to the cysteine-rich domain of CD164. Together, this study identifies novel factors associated with LCMV infection of human tissues and highlights the importance of CD164, a sialomucin that previously had not been associated with viral infection. IMPORTANCE Lymphocytic choriomeningitis virus (LCMV) is a human-pathogenic mammarenavirus that can be fatal in congenital infections. Although frequently used in the study of persistent infections in the field of immunology, aspects of this virus's life cycle remain incomplete. For example, while viral entry has been shown to depend on a cell adhesion molecule, DAG1, genetic knockout of this gene allows for residual viral infection, implying that additional receptors can mediate cell entry. The significance of our study is the identification of host factors important for successful infection, including the sialomucin CD164, which had not been previously associated with viral infection. We demonstrated that CD164 is essential for LCMV entry into human cells and can serve as a possible therapeutic target for treatment of congenital infection.

A subpopulation of arenavirus nucleoprotein localizes to mitochondria

Viruses need cells for their replication and, therefore, ways to hijack cellular functions. Mitochondria play fundamental roles within the cell in metabolism, immunity and regulation of homeostasis due to which some viruses aim to alter mitochondrial functions. Herein we show that the nucleoprotein (NP) of arenaviruses enters the mitochondria of infected cells, affecting the mitochondrial morphology. Reptarenaviruses cause boid inclusion body disease (BIBD) that is characterized, especially in boas, by the formation of cytoplasmic inclusion bodies (IBs) comprising reptarenavirus NP within the infected cells. We initiated this study after observing electron-dense material reminiscent of IBs within the mitochondria of reptarenavirus infected boid cell cultures in an ultrastructural study. We employed immuno-electron microscopy to confirm that the mitochondrial inclusions indeed contain reptarenavirus NP. Mutations to a putative N-terminal mitochondrial targeting signal (MTS), identified via software predictions in both mamm- and reptarenavirus NPs, did not affect the mitochondrial localization of NP, suggesting that it occurs independently of MTS. In support of MTS-independent translocation, we did not detect cleavage of the putative MTSs of arenavirus NPs in reptilian or mammalian cells. Furthermore, in vitro translated NPs could not enter isolated mitochondria, suggesting that the translocation requires cellular factors or conditions. Our findings suggest that MTS-independent mitochondrial translocation of NP is a shared feature among arenaviruses. We speculate that by targeting the mitochondria arenaviruses aim to alter mitochondrial metabolism and homeostasis or affect the cellular defense.

Diagnostics of Infectious Respiratory Pathogens in Reptiles

Methods for the detection of pathogens associated with respiratory disease in reptiles, including viruses, bacteria, fungi, and parasites, are constantly evolving as is the understanding of the specific roles played by various pathogens in disease processes. Some are known to be primary pathogens with high prevalence in captive reptiles, for example, serpentoviruses in pythons or mycoplasma in tortoises. Others are very commonly found in reptiles with respiratory disease but are most often considered secondary, for example, gram-negative bacteria. Detection methods as well as specific pathogens associated with upper- and lower-respiratory disease are discussed.

Experimental Reptarenavirus Infection of Boa constrictor and Python regius

Boid inclusion body disease (BIBD) causes losses in captive snake populations globally. BIBD is associated with the formation of cytoplasmic inclusion bodies (IBs), which mainly comprise reptarenavirus nucleoprotein (NP). In 2017, BIBD was reproduced by cardiac injection of boas and pythons with reptarenaviruses, thus demonstrating a causative link between reptarenavirus infection and the disease. Here, we report experimental infections of Python regius (n = 16) and Boa constrictor (n = 16) with three reptarenavirus isolates. First, we used pythons (n = 8) to test two virus delivery routes: intraperitoneal injection and tracheal instillation. Viral RNAs but no IBs were detected in brains and lungs at 2 weeks postinoculation. Next, we inoculated pythons (n = 8) via the trachea. During the 4 months following infection, snakes showed transient central nervous system (CNS) signs but lacked detectable IBs at the time of euthanasia. One of the snakes developed severe CNS signs; we succeeded in reisolating the virus from the brain of this individual and could demonstrate viral antigen in neurons. In a third attempt, we tested cohousing, vaccination, and sequential infection with multiple reptarenavirus isolates on boas (n = 16). At 10 months postinoculation, all but one snake tested positive for viral RNA in lung, brain, and/or blood, but none exhibited the characteristic IBs. Three of the four vaccinated snakes seemed to sustain challenge with the same reptarenavirus; however, neither of the two snakes rechallenged with different reptarenaviruses remained uninfected. Comparison of the antibody responses in experimentally versus naturally reptarenavirus-infected animals indicated differences in the responses.IMPORTANCE In the present study, we experimentally infected pythons and boas with reptarenavirus via either intraperitoneal injection or tracheal instillation. The aims were to experimentally induce boid inclusion body disease (BIBD) and to develop an animal model for studying disease transmission and pathogenesis. Both virus delivery routes resulted in infection, and infection via the trachea could reflect the natural route of infection. In the experimentally infected snakes, we did not find evidence of inclusion body (IB) formation, characteristic of BIBD, in pythons or boas. Most of the boas (11/12) remained reptarenavirus infected after 10 months, which suggests that they developed a persistent infection that could eventually have led to BIBD. We demonstrated that vaccination using recombinant protein or an inactivated virus preparation prevented infection by a homologous virus in three of four snakes. Comparison of the antibody responses of experimentally and naturally reptarenavirus-infected snakes revealed differences that merit further studies.

Virtopsy of a gravid Boa constrictor using computed tomography and magnetic resonance imaging

This article presents radiologic examinations of a deeply sedated Boa constrictor with boid inclusion body disease (BIBD) as an adjunction to the subsequent necropsy. This method is known as virtopsy. The Boa constrictor in the present case was gravid. Computed tomography (CT) allowed for the detailed depiction of a fetal skeleton at the rear end of the adult snake. Furthermore, tiny gas formation was detected inside the cranium of the fetus, which was deemed a radiologic sign for decomposition. Magnetic resonance imaging (MRI) delineated the soft tissue at high resolution. This article illustrates the use of CT and MRI for the examination of a gravid Boa constrictor before necropsy and demonstrates the detection of "normal" postmortem findings leading to the confirmation of fetal death in situ.

Selected Emerging Infectious Diseases of Squamata: An Update

This article details emerging infectious diseases that have devastating impacts on captive and wild squamates. Treatment advances have been attempted for Cryptosporidium infections in squamates. Gram-positive bacteria, Devriesea agamarum and Austwickia chelonae, are contributing to severe disease in captive and now in wild reptiles, some critically endangered. Nannizziposis, Paranannizziopsis, and Ophidiomyces continue to cause fatal disease as primary pathogens in wild and captive populations of squamates and sphenodontids. Nidovirus, bornavirus, paramyxovirus, sunshine virus, and arenavirus have emerged to be significant causes of neurorespiratory disease in snakes. Controlled studies evaluating environmental stability, disinfection, transmission control, and treatment are lacking.

PROTEIN ELECTROPHORESIS OF PLASMA SAMPLES FROM BOA CONSTRICTORS WITH AND WITHOUT REPTARENAVIRUS INFECTION

Reptarenaviruses infect a variety of boid and pythonid snake species worldwide and have been shown to be the cause of inclusion body disease (IBD). Little is known about the correlations between virus infection and clinical disease, as well as the effects of viral infection on the immune system and the blood protein fractions. The goal of this study was to examine the differences in the plasma protein fractions in reptarenavirus reverse transcription polymerase chain reaction (RT-PCR)-negative and -positive tested snakes with and without clinical signs of disease. Blood from a total of 111 boa constrictors (Boa constrictor) was evaluated. Reverse transcription PCRs and H&E staining for inclusion bodies were carried out on each sample for the detection of reptarenavirus, and the plasma protein fractions were evaluated by capillary zone electrophoresis (CZE). Thirty four of the 111 evaluated snakes were positive by RT-PCR and 19 of the 34 showed clinical signs of disease. In comparison with IBD-negative healthy boa constrictors, the positive snakes with clinical signs had significantly lower albumin levels (P = 0.0052), lower A: G ratios (P = 0.0037), and lower α-globulin levels (P = 0.0073), while their γ-globulin levels were significantly higher (P = 0.0004). In the same comparison, clinically healthy arenavirus-positive boas showed only significantly lower α-globulin (P = 0.0124) and higher γ-globulin levels (P = 0.0394). The results of the present study indicate that reptarenavirus infection may influence plasma protein fractions in boa constrictors.

DETECTION OF AN ARENAVIRUS IN A GROUP OF CAPTIVE WAGLER'S PIT VIPERS (TROPIDOLAEMUS WAGLERI)

A group of eight Wagler's pit vipers (Tropidolaemus wagleri) from a private collection died with respiratory signs within 6 mo of one another. The group consisted of an adult breeding pair that was wild caught and six offspring from this pair. Four of the dead snakes were submitted for gross and histopathology. Signs of bacterial pneumonia were detected in all four examined snakes. No inclusion bodies suggestive of viral infection were found in any of the examined tissues. Polymerase chain reactions for the detection of ferla-, adeno-, reo-, and nidoviruses were all negative, but reptarenaviruses closely related to viruses previously described in boa constrictors (Boa constrictor) with inclusion body disease were detected in two of the four snakes. This is the first description of reptarenaviruses in viperid snakes. The pathogenic role of the virus in illness is unknown.

Identification of Reptarenaviruses, Hartmaniviruses, and a Novel Chuvirus in Captive Native Brazilian Boa Constrictors with Boid Inclusion Body Disease

Boid inclusion body disease (BIBD) is a transmissible viral disease of captive snakes that causes severe losses in snake collections worldwide. It is caused by reptarenavirus infection, which can persist over several years without overt signs but is generally associated with the eventual death of the affected snakes. Thus far, reports have confirmed the existence of reptarenaviruses in captive snakes in North America, Europe, Asia, and Australia, but there is no evidence that it also occurs in wild snakes. BIBD affects boa species within the subfamily Boinae and pythons in the family Pythonidae, the habitats of which do not naturally overlap. Here, we studied Brazilian captive snakes with BIBD using a metatranscriptomic approach, and we report the identification of novel reptarenaviruses, hartmaniviruses, and a new species in the family Chuviridae The reptarenavirus L segments identified are divergent enough to represent six novel species, while we found only a single novel reptarenavirus S segment. Until now, hartmaniviruses had been identified only in European captive boas with BIBD, and the present results increase the number of known hartmaniviruses from four to six. The newly identified chuvirus showed 38.4%, 40.9%, and 48.1% amino acid identity to the nucleoprotein, glycoprotein, and RNA-dependent RNA polymerase, respectively, of its closest relative, Guangdong red-banded snake chuvirus-like virus. Although we cannot rule out the possibility that the found viruses originated from imported snakes, the results suggest that the viruses could circulate in indigenous snake populations.IMPORTANCE Boid inclusion body disease (BIBD), caused by reptarenavirus infection, affects captive snake populations worldwide, but the reservoir hosts of reptarenaviruses remain unknown. Here, we report the identification of novel reptarenaviruses, hartmaniviruses, and a chuvirus in captive Brazilian boas with BIBD. Three of the four snakes studied showed coinfection with all three viruses, and one of the snakes harbored three novel reptarenavirus L segments and one novel S segment. The samples originated from collections with Brazilian indigenous snakes only, which could indicate that these viruses circulate in wild snakes. The findings could further indicate that boid snakes are the natural reservoir of reptarena- and hartmaniviruses commonly found in captive snakes. The snakes infected with the novel chuvirus all suffered from BIBD; it is therefore not possible to comment on its potential pathogenicity and contribution to the observed changes in the present case material.

Differences in Tissue and Species Tropism of Reptarenavirus Species Studied by Vesicular Stomatitis Virus Pseudotypes

Reptarenaviruses cause Boid Inclusion Body Disease (BIBD), and co-infections by several reptarenaviruses are common in affected snakes. Reptarenaviruses have only been found in captive snakes, and their reservoir hosts remain unknown. In affected animals, reptarenaviruses appear to replicate in most cell types, but their complete host range, as well as tissue and cell tropism are unknown. As with other enveloped viruses, the glycoproteins (GPs) present on the virion's surface mediate reptarenavirus cell entry, and therefore, the GPs play a critical role in the virus cell and tissue tropism. Herein, we employed single cycle replication, GP deficient, recombinant vesicular stomatitis virus (VSV) expressing the enhanced green fluorescent protein (scrVSV∆G-eGFP) pseudotyped with different reptarenavirus GPs to study the virus cell tropism. We found that scrVSV∆G-eGFPs pseudotyped with reptarenavirus GPs readily entered mammalian cell lines, and some mammalian cell lines exhibited higher, compared to snake cell lines, susceptibility to reptarenavirus GP-mediated infection. Mammarenavirus GPs used as controls also mediated efficient entry into several snake cell lines. Our results confirm an important role of the virus surface GP in reptarenavirus cell tropism and that mamma-and reptarenaviruses exhibit high cross-species transmission potential.

Prevalence of inclusion body disease and associated comorbidity in captive collections of boid and pythonid snakes in Belgium

Inclusion body disease (IBD) is caused by reptarenaviruses and constitutes one of the most notorious viral diseases in snakes. Although central nervous system disease and various other clinical signs have been attributed to IBD in boid and pythonid snakes, studies that unambiguously reveal the clinical course of natural IBD and reptarenavirus infection are scarce. In the present study, the prevalence of IBD and reptarenaviruses in captive snake collections and the correlation of IBD and reptarenavirus infection with the clinical status of the sampled snakes were investigated. In three IBD positive collections, long-term follow-up during a three- to seven-year period was performed. A total of 292 snakes (178 boas and 114 pythons) from 40 collections in Belgium were sampled. In each snake, blood and buffy coat smears were evaluated for the presence of IBD inclusion bodies (IB) and whole blood was tested for reptarenavirus RNA by RT-PCR. Of all tested snakes, 16.5% (48/292) were positive for IBD of which all were boa constrictors (34.0%; 48/141) and 17.1% (50/292) were reptarenavirus RT-PCR positive. The presence of IB could not be demonstrated in any of the tested pythons, while 5.3% (6/114) were reptarenavirus positive. In contrast to pythons, the presence of IB in peripheral blood cells in boa constrictors is strongly correlated with reptarenavirus detection by RT-PCR (P<0.0001). Although boa constrictors often show persistent subclinical infection, long-term follow-up indicated that a considerable number (22.2%; 6/27) of IBD/reptarenavirus positive boas eventually develop IBD associated comorbidities.

Blind Trading: A Literature Review of Research Addressing the Welfare of Ball Pythons in the Exotic Pet Trade

Simple Summary

The Ball python is a small species that is commonly kept as an exotic pet across the world. Despite huge numbers of these snakes being kept and traded in the pet industry, there is very little information available about how catching, breeding, transporting and housing them in captivity could impact their welfare. Our study reviewed the published literature for this species and found 88 relevant peer-reviewed scientific papers. Physical health was the predominant focus of research, with numerous studies reporting on disease, injury or clinical treatments. Far fewer papers focused on other aspects of Ball python wellbeing, including behaviour, nutrition, environment or mental condition. We also found that very few studies focused on wellbeing prior to pet ownership, i.e., during the early stages of the trade chain when they are caught from the wild, transported, or bred in captivity. We recommend that more research is needed to assess the impact of the exotic pet trade on this species’ welfare. In particular, research on welfare conditions during capture and transportation of wild Ball pythons, and the potential effects of captive breeding, could help reduce suffering throughout the trade.

Abstract

Extensive numbers of Ball pythons are caught, bred, traded and subsequently kept in captivity across the world as part of the exotic pet industry. Despite their widespread availability as pets, relatively little is known about the potential welfare challenges affecting them. We reviewed the literature for research focused on the health and welfare of Ball pythons in the international pet trade. From a total of 88 articles returned from the search criteria, our analysis showed that very few actually focused on trade (10%) or animal welfare (17%). Instead, the majority (64%) of articles focused on veterinary science. There was a considerable bias towards physical health, with most studies neglecting the four other domains of animal welfare (behaviour, nutrition, environment and mental health). Furthermore, very few studies considered Ball pythons prior to resulting pet ownership, during wild capture and transportation or captive breeding operations. Our review demonstrates that our current understanding of welfare for Ball pythons traded as exotic pets is limited. We recommend that future research should focus on aspects of the industry that are currently overlooked, including the potential consequences of genetic selection during captive-breeding and the conditions provided for snakes prior to and during international transportation.

Antibody response in snakes with boid inclusion body disease

Boid Inclusion Body Disease (BIBD) is a potentially fatal disease reported in captive boid snakes worldwide that is caused by reptarenavirus infection. Although the detection of intracytoplasmic inclusion bodies (IB) in blood cells serves as the gold standard for the ante mortem diagnosis of BIBD, the mechanisms underlying IB formation and the pathogenesis of BIBD are unknown. Knowledge on the reptile immune system is sparse compared to the mammalian counterpart, and in particular the response towards reptarenavirus infection is practically unknown. Herein, we investigated a breeding collection of 70 Boa constrictor snakes for BIBD, reptarenavirus viraemia, anti-reptarenavirus IgM and IgY antibodies, and population parameters. Using NGS and RT-PCR on pooled blood samples of snakes with and without BIBD, we could identify three different reptarenavirus S segments in the collection. The examination of individual samples by RT-PCR indicated that the presence of University of Giessen virus (UGV)-like S segment strongly correlates with IB formation. We could also demonstrate a negative correlation between BIBD and the presence of anti-UGV NP IgY antibodies. Further evidence of an association between antibody response and BIBD is the finding that the level of anti-reptarenavirus antibodies measured by ELISA was lower in snakes with BIBD. Furthermore, female snakes had a significantly lower body weight when they had BIBD. Taken together our findings suggest that the detection of the UGV-/S6-like S segment and the presence of anti-reptarenavirus IgY antibodies might serve as a prognostic tool for predicting the development of BIBD.

Proteomics Computational Analyses Suggest that the Antennavirus Glycoprotein Complex Includes a Class I Viral Fusion Protein (α-Penetrene) with an Internal Zinc-Binding Domain and a Stable Signal Peptide

A metatranscriptomic study of RNA viruses in cold-blooded vertebrates identified two related viruses from frogfish (Antennarius striatus) that represent a new genus Antennavirus in the family Arenaviridae (Order: Bunyavirales). Computational analyses were used to identify features common to class I viral fusion proteins (VFPs) in antennavirus glycoproteins, including an N-terminal fusion peptide, two extended alpha-helices, an intrahelical loop, and a carboxyl terminal transmembrane domain. Like mammarenavirus and hartmanivirus glycoproteins, the antennavirus glycoproteins have an intracellular zinc-binding domain and a long virion-associated stable signal peptide (SSP). The glycoproteins of reptarenaviruses are also class I VFPs, but do not contain zinc-binding domains nor do they encode SSPs. Divergent evolution from a common progenitor potentially explains similarities of antennavirus, mammarenavirus, and hartmanivirus glycoproteins, with an ancient recombination event resulting in a divergent reptarenavirus glycoprotein.

Reptarenaviruses in apparently healthy snakes in an Australian zoological collection

BACKGROUND

Inclusion body disease (IBD) is a disease of snakes with a global distribution and has recently been shown to be caused by reptarenaviruses. Testing for this group of viruses in asymptomatic snakes allows the association between infection and disease to be further elucidated.

METHODS

A reptarenavirus was detected by RT-PCR in a reticulated python (Malayopython reticulatus) from an Australian zoological collection that was open-mouth breathing and had erythematous oral mucosa. Another 27 pythons, 4 elapids, 2 colubrids and 2 boas from this collection were then screened. From these animals, swabs, whole blood and/or tissue were tested for reptarenaviruses by RT-PCR. Additionally, blood films from 10 snakes were examined by light microscopy for the presence of inclusion bodies. The majority of samples were collected over a 484-day period.

RESULTS

A total of 8 animals were RT-PCR-positive (8/36 = 22.2%): 6 were pythons, 1 was a corn snake (Pantherophis guttatus) and 1 was a Madagascar tree boa (Sanzinia madagascariensis). From them, 57 samples were collected, but only one from each animal was RT-PCR-positive (8/57 = 14.0%). From all 36 animals in this study, 8/182 samples were RT-PCR-positive (4.4%). Inclusion bodies were not recognised in any of the blood films. Only the reticulated python showed signs of illness, which improved without any further intervention. All other RT-PCR-positive snakes were apparently healthy throughout the duration of the study.

CONCLUSION

This study showed a weak association between the presence of reptarenaviruses and disease. Testing serially collected swab and whole-blood samples increased the number of animals in which reptarenaviruses were detected.

Hemorrhagic Fever-Causing Arenaviruses: Lethal Pathogens and Potent Immune Suppressors

Hemorrhagic fevers (HF) resulting from pathogenic arenaviral infections have traditionally been neglected as tropical diseases primarily affecting African and South American regions. There are currently no FDA-approved vaccines for arenaviruses, and treatments have been limited to supportive therapy and use of non-specific nucleoside analogs, such as Ribavirin. Outbreaks of arenaviral infections have been limited to certain geographic areas that are endemic but known cases of exportation of arenaviruses from endemic regions and socioeconomic challenges for local control of rodent reservoirs raise serious concerns about the potential for larger outbreaks in the future. This review synthesizes current knowledge about arenaviral evolution, ecology, transmission patterns, life cycle, modulation of host immunity, disease pathogenesis, as well as discusses recent development of preventative and therapeutic pursuits against this group of deadly viral pathogens.

Characterization of Haartman Institute snake virus-1 (HISV-1) and HISV-like viruses-The representatives of genus Hartmanivirus, family Arenaviridae

The family Arenaviridae comprises three genera, Mammarenavirus, Reptarenavirus and the most recently added Hartmanivirus. Arenaviruses have a bisegmented genome with ambisense coding strategy. For mammarenaviruses and reptarenaviruses the L segment encodes the Z protein (ZP) and the RNA-dependent RNA polymerase, and the S segment encodes the glycoprotein precursor and the nucleoprotein. Herein we report the full length genome and characterization of Haartman Institute snake virus-1 (HISV-1), the putative type species of hartmaniviruses. The L segment of HISV-1 lacks an open-reading frame for ZP, and our analysis of purified HISV-1 particles by SDS-PAGE and electron microscopy further support the lack of ZP. Since we originally identified HISV-1 in co-infection with a reptarenavirus, one could hypothesize that co-infecting reptarenavirus provides the ZP to complement HISV-1. However, we observed that co-infection does not markedly affect the amount of hartmanivirus or reptarenavirus RNA released from infected cells in vitro, indicating that HISV-1 does not benefit from reptarenavirus ZP. Furthermore, we succeeded in generating a pure HISV-1 isolate showing the virus to replicate without ZP. Immunofluorescence and ultrastructural studies demonstrate that, unlike reptarenaviruses, HISV-1 does not produce the intracellular inclusion bodies typical for the reptarenavirus-induced boid inclusion body disease (BIBD). While we observed HISV-1 to be slightly cytopathic for cultured boid cells, the histological and immunohistological investigation of HISV-positive snakes showed no evidence of a pathological effect. The histological analyses also revealed that hartmaniviruses, unlike reptarenaviruses, have a limited tissue tropism. By nucleic acid sequencing, de novo genome assembly, and phylogenetic analyses we identified additional four hartmanivirus species. Finally, we screened 71 individuals from a collection of snakes with BIBD by RT-PCR and found 44 to carry hartmaniviruses. These findings suggest that harmaniviruses are common in captive snake populations, but their relevance and pathogenic potential needs yet to be revealed.

A fixed moderate-dose combination of tiletamine+zolazepam outperforms midazolam in induction of short-term immobilization of ball pythons (Python regius)

Laboratory animals are commonly anesthetized to prevent pain and distress and to provide safe handling. Anesthesia procedures are well-developed for common laboratory mammals, but not as well established in reptiles. We assessed the performance of intramuscularly injected tiletamine (dissociative anesthetic) and zolazepam (benzodiazepine sedative) in fixed combination (2 mg/kg and 3 mg/kg) in comparison to 2 mg/kg of midazolam (benzodiazepine sedative) in ball pythons (Python regius). We measured heart and respiratory rates and quantified induction parameters (i.e., time to loss of righting reflex, time to loss of withdrawal reflex) and recovery parameters (i.e., time to regain righting reflex, withdrawal reflex, normal behavior). Mild decreases in heart and respiratory rates (median decrease of <10 beats per minute and <5 breaths per minute) were observed for most time points among all three anesthetic dose groups. No statistically significant difference between the median time to loss of righting reflex was observed among animals of any group (p = 0.783). However, the withdrawal reflex was lost in all snakes receiving 3mg/kg of tiletamine+zolazepam but not in all animals of the other two groups (p = 0.0004). In addition, the time for animals to regain the righting reflex and resume normal behavior was longer in the drug combination dose groups compared to the midazolam group (p = 0.0055). Our results indicate that midazolam is an adequate sedative for ball pythons but does not suffice to achieve reliable immobilization or anesthesia, whereas tiletamine+zolazepam achieves short-term anesthesia in a dose-dependent manner.