The role of canine distemper virus and persistent organic pollutants in mortality patterns of Caspian seals (Pusa caspica)

A recent distemper virus outbreak in the growing canine populations of Galapagos Islands: a persistent threat for the endangered Galapagos Sea Lion

Canine Distemper Virus (CDV) is a highly contagious virus that can cross mammalian species barriers and has widespread impacts on both domestic animals and wildlife populations. This study describes a recent outbreak of CDV in the Galapagos Islands in 2019. A total number of 125 dogs with clinical signs compatible with CDV were included in this study. Nasal swabs were taken and analyzed by RT-qPCR for the detection of CDV, resulting in a positivity rate of 74.4% (IC95%, 66-81%). Among the CDV positive dogs, 82.2% presented with respiratory signs, 48.8% neurological signs, and 28.9% gastrointestinal signs. CDV has been previously reported in the domestic canine population of the Galapagos Islands in 2001 and 2004. The current study shows how CDV is still a threat for the endemic and endangered Galapagos sea lion, despite recent policies for dog population control and CDV vaccination.

A Coupled Human and Natural Systems Framework to Characterize Emerging Infectious Diseases-The Case of Fibropapillomatosis in Marine Turtles

Emerging infectious diseases of wildlife have markedly increased in the last few decades. Unsustainable, continuous, and rapid alterations within and between coupled human and natural systems have significantly disrupted wildlife disease dynamics. Direct and indirect anthropogenic effects, such as climate change, pollution, encroachment, urbanization, travel, and trade, can promote outbreaks of infectious diseases in wildlife. We constructed a coupled human and natural systems framework identifying three main wildlife disease risk factors behind these anthropogenic effects: (i) immune suppression, (ii) viral spillover, and (iii) disease propagation. Through complex and convoluted dynamics, each of the anthropogenic effects and activities listed in our framework can lead, to some extent, to one or more of the identified risk factors accelerating disease outbreaks in wildlife. In this review, we present a novel framework to study anthropogenic effects within coupled human and natural systems that facilitate the emergence of infectious disease involving wildlife. We demonstrate the utility of the framework by applying it to Fibropapillomatosis disease of marine turtles. We aim to articulate the intricate and complex nature of anthropogenically exacerbated wildlife infectious diseases as multifactorial. This paper supports the adoption of a One Health approach and invites the integration of multiple disciplines for the achievement of effective and long-lasting conservation and the mitigation of wildlife emerging diseases.

Trace Elements and Contaminants Concentrations in Tissues of Caspian Seals (Pusa caspica) along the Iranian Coast

The Caspian seal (Pusa caspica) is an endangered species that only lives in the Caspian Sea. Little information is available on its exposure to contaminants, and no data exists for Southern sub-populations. From 2011 to 2016, tissues samples were collected from 20 Caspian seals to (i) Define the concentration of trace elements in five different matrices and the concentration of 30 pesticides in their blubber; (ii) Determine whether differences in contaminant concentrations are age- or sex-related; (iii) Evaluate if detected concentrations can represent a risk to the species. Age- and sex-related variations were detected for Zn and Hg in the blubber and Fe in the kidney by age only. Exceptionally high Hg concentrations and low levels of hepatic Zn were detected, raising some concern about the reproductive health of seals. Similarly, the DDTs levels detected were in the range of adverse reproductive effects in marine mammals. Based on these results, potentially adverse effects on the immune and endocrine systems of the Caspian seal cannot be ruled out. Therefore, it is of the utmost importance that pollutant monitoring becomes an integral component of conservation strategies for the Caspian seal.

Pathologic findings and causes of death in bottlenose dolphins Tursiops truncatus stranded along the Georgia coast, USA (2007-2013)

Between 2007 and 2013, before the 2013 cetacean morbillivirus outbreak, 26 fresh bottlenose dolphin carcasses were necropsied on the coast of Georgia, USA. Here, we present the pathological and microbiological findings associated with their most likely causes of death. The primary cause of death was determined in 25 individuals and included systemic bacterial infection (n = 7), verminous and bacterial bronchopneumonia (n = 5), drowning/entanglement (n = 5), disseminated histoplasmosis (n = 1), intestinal intussusception (n = 1), vegetative endocarditis (n = 1), meningitis (n = 1), necrotizing dermatitis (n = 1), disseminated angiomatosis (n = 1), emaciation (n = 1) and stingray spine trauma (n = 1). Histiocytic and eosinophilic bronchopneumonia associated with Halocerchus sp. infection was observed in 69% of the animals (18/26) and eosinophilic gastritis due to Anisakidae nematodes was found in 36% of the examined stomachs (8/22). Moderate to severe eosinophilic pancreatitis with fibrosis was observed in 4 animals infected with Brachycladiidae trematodes. Proliferative and ulcerative lymphoplasmacytic dermatitis was found in 5 animals and was considered to contribute to deteriorated health status in 2 calves. Pulmonary and lymph node angiomatosis were observed in 15 and 10 animals, respectively. In at least 2 animals, the concentration of polychlorinated biphenyls (PCBs) in the blubber exceeded 1500 µg g-1 of lipid. Bottlenose dolphins stranded on the Georgia coast have a wide range of inflammatory lesions associated with a variety of helminth, bacterial, and fungal pathogens. Some resident animals have also been exposed to high levels of PCB contamination, which could reduce host immunocompetence. Higher exposure to these or other pathogens could result in further decline in the health of resident and migrant dolphin populations in this region.

Development and validation of a portable, point-of-care canine distemper virus qPCR test

Canine distemper virus (CDV) is a multi-host pathogen that can cause significant mortality in domestic, wild terrestrial and marine mammals. It is a major conservation threat in some endangered species. Infection can result in severe respiratory disease and fatal encephalitis. Diagnosis and disease monitoring in wildlife, and differentiation of CDV from rabies (a life-threatening zoonotic disease that can produce similar neurologic signs), would benefit from the availability of a portable, point-of-care (POC) diagnostic test. We therefore developed a quantitative RT-PCR assay for CDV using shelf-stable, lyophilized reagents and target-specific primers and probes for use with the handheld Biomeme two3™ qPCR thermocycler. Biomeme's extraction methodology, lyophilized reagents, and thermocycler were compared to our standard laboratory-based methods to assess sensitivity, efficiency and overall test performance. Results using a positive control plasmid for CDV showed comparable sensitivity (detection of 50 copies) and PCR efficiency between the two platforms, and CDV detection was similar between platforms when tested using a modified live CDV vaccine. Significantly higher Ct values (average Ct = 5.1 cycles) were observed using the Biomeme platform on known CDV positive animal samples. CDV detection using the Biomeme platform was similar in 25 of 26 samples from suspect CDV cases when compared to standard virology laboratory testing. One false positive was observed that was negative upon retest. The Biomeme methodology can be adapted for detection of specific targets, and this portable technology saves time by eliminating the need for local or international sample transport for laboratory-based diagnostics. However, results of our testing suggest that decreased diagnostic sensitivity (higher Ct values) relative to laboratory-based methods was observed using animal samples, so careful validation and optimization are essential. Portable qPCR platforms can empower biologists and wildlife health professionals in remote and low-resource settings, which will greatly improve our understanding of CDV disease ecology and associated conservation threats in wildlife.

PCB levels in adipose tissue of dogs from illegal dumping sites in Campania region (Italy)

The aim of the study is to investigate the potential relationship between exposure to PCBs and cancer. In doing so we relied on a sample of dogs coming from a peculiar area of the Campania region (Italy), that has been suffering for illegal waste dumping and open air burning of plastic waste for many years. The latter determined the release of organic and inorganic pollutants, such as the PCBs. By comparing dogs with cancer and healthy dogs, we found much higher PCB concentrations in the former, with a significant difference (p < 0.05) for the non-indicator ∑10NDL-PCB and the DL-PCBs. A regression analysis, controlling for three potentially confounding factors, that are sex, age and weight, confirmed the higher ∑10NDL-PCB concentration in dogs with cancer. Hence, our evidence suggests a potential health hazard for animals and likewise people living in a risky area due to the presence of environmental organic pollutants.

Assessment of the Current State of the Caspian Sea and the Caspian Seal Habitat Analysis

This article is devoted to the determination of heavy metals and harmful organic compounds in sea water – the habitat of the Caspian seal. The group of the most common heavy metals, according to many authors, includes manganese, nickel, zinc, iron, cadmium, lead, copper and their salts, characterized by long-term preservation and accumulation in water, sediments and hydrobionts. The studies were conducted from February 7–12, 2017 on the route from the Kalamkas (Kazakhstan) field through the islands of Kulaly to the village of Bautino. Water samples were taken 10‒20 cm below the sea ice and surface level, each sample was taken in 2 replicates: one for the Kazakhstan laboratory in Almaty and one for the French independent laboratory. Water samples were analyzed for the content of 13 heavy metals such as – Co, Cu, Ti, Bi, Ag, V, Al, Be, Sb, Sn, Fe, Cr, Mo. It was established that in all water samples the content of vanadium exceeds the maximum permissible concentration (MPC) level by 1.5–7.4 times, beryllium ‒ 140–445 times, antimony 13.2–17.2 times. The maximum concentrations of the V and Be contents were found in water samples taken at sampling points No. 1 and 2, and Sb ‒ at points No. 1.6, 7.8. Cobalt, copper, iron and chromium were not detected in the samples presented. The content of other metals (Ti, Bi, Ag, Al, Sn, Mo) was significantly below the permissible levels or below the detection limits of the method. All samples of sea water are contaminated by several organic chemical pollutants, to various degrees and from different origins. Data on the accumulation of petroleum hydrocarbons and heavy metals in the habitat of Caspian seals characterize the toxicological situation in the study region.

Differential impact of anthropogenic pressures on Caspian Sea ecoregions

Over the past decades, overall ecological conditions in the Caspian Sea have deteriorated. However, a comprehensive understanding of lake-wide spatial differences in anthropogenic pressures is lacking and the biological consequences of human impacts are poorly understood. This paper therefore aims at assessing the individual and combined effects of critical anthropogenic pressures on the Caspian Sea ecoregions. First, cumulative pressure scores were calculated with a cumulative environmental assessment (CEA) analysis. Then, the individual contribution of anthropogenic pressures was quantified. Finally, ecoregion-specific differences were assessed. The analyses show that both cumulative and individual pressure scores are unevenly distributed across the Caspian Sea. The most important individual pressures are invasive species, chemical pollution and poaching. This uneven distribution of pressure scores across Caspian Sea ecoregions creates new challenges for future conservation strategies, as different ecoregions usually require different conservation measures.

Mills J, Kheirabady V. Frequency of exposure of endangered Caspian seals to Canine distemper virus, Leptospira interrogans, and Toxoplasma gondii

Canine distemper virus (CDV), Leptospira interrogans, and Toxoplasma gondii are potentially lethal pathogens associated with decline in marine mammal populations. The Caspian Sea is home for the endangered Caspian seal (Pusa caspica). In the late 1990s and early 2000s, CDV caused a series of mortality events involving at least several thousand Caspian seals. To assess current infection status in Caspian seals, we surveyed for antibodies to three pathogens with potential to cause mortality in marine mammals. During 2015–2017, we tested serum samples from 36, apparently healthy, Caspian seals, accidentally caught in fishing nets in the Caspian Sea off Northern Iran, for antibodies to CDV, L. interrogans, and T. gondii, by virus neutralization, microscopic agglutination, and modified agglutination, respectively. Twelve (33%), 6 (17%), and 30 (83%) samples were positive for CDV, L. interrogans and T. gondii antibodies, respectively. The highest titers of CDV, L. interrogans, and T. gondii antibodies were 16, 400, and 50, respectively. Frequencies of antibody to these pathogens were higher in seals >1 year old compared to seals <1 year old. Two serovars of L. interrogans (Pomona and Canicola) were detected. Our results suggest a need for additional studies to clarify the impact of these pathogens on Caspian seal population decline and the improvement of management programs, including systematic screening to detect and protect the remaining population from disease outbreaks.

Outbreak and genotyping of canine distemper virus in captive Siberian tigers and red pandas

In this study, four canine distemper virus (CDV) strains were isolated from captive Siberian tigers (Panthera tigris altaica) and red pandas (Ailurus fulgens) during two separate CDV outbreaks in a zoo in Guangdong province, China. Sequence alignment and phylogenetic analyses based on the full-length hemagglutinin (H) and fusion (F) genes showed that they were closely identical to genotype Asia-1. Prior to confirmation of CDV in Siberian tigers, to control spread of the disease, a live attenuated combination CDV vaccine was used among almost all carnivore animals except for red pandas in which another recombinant combination CDV vaccine was used. However, about two months later, CDV re-emerged and caused the death among red pandas. Based on the vaccination records, the live combination vaccine could be considered an ideal weapon against CDV in zoo carnivore animals. Although the recombinant combination CDV vaccine was safe for red pandas, its protection effectiveness remains to be further investigated. Moreover, according to the outbreak interval time and sequence characterization, we suspected that stray cats circulating in the zoo were the intermediate host, which contributed to CDV spread from stray dogs to zoo animals. This study revealed the importance of vaccination and biosecurity for zoo animals.

In Vitro Exposure of Harbor Seal Immune Cells to Aroclor 1260 Alters Phocine Distemper Virus Replication

In the last 30 years, several large-scale marine mammal mortality events have occurred, often in close association with highly polluted regions, leading to suspicions that contaminant-induced immunosuppression contributed to these epizootics. Some of these recent events also identified morbillivirus as a cause of or contributor to death. The role of contaminant exposures regarding morbillivirus mortality is still unclear. The results of this study aimed to address the potential for a mixture of polychlorinated biphenyls (PCBs), specifically Aroclor 1260, to alter harbor seal T-lymphocyte proliferation and to assess if exposure resulted in increased likelihood of phocine distemper virus (PDV USA 2006) to infect susceptible seals in an in vitro system. Exposure of peripheral blood mononuclear cells to Aroclor 1260 did not significantly alter lymphocyte proliferation (1, 5, 10, and 20 ppm). However, using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), lymphocytes exposed to 20 ppm Aroclor 1260 exhibited a significant decrease in PDV replication at day 7 and a significant increase at day 11 compared with unexposed control cells. Similar and significant differences were apparent on exposure to Aroclor 1260 in monocytes and supernatant. The results here indicate that in harbor seals, Aroclor 1260 exposure results in a decrease in virus early during infection and an increase during late infection. The consequences of this contaminant-induced infection pattern in a highly susceptible host could result in a greater potential for systemic infection with greater viral load, which could explain the correlative findings seen in wild populations exposed to a range of persistent contaminants that suffer from morbillivirus epizootics.

Cross-species transmission of canine distemper virus-an update

Canine distemper virus (CDV) is a pantropic morbillivirus with a worldwide distribution, which causes fatal disease in dogs. Affected animals develop dyspnea, diarrhea, neurological signs and profound immunosuppression. Systemic CDV infection, resembling distemper in domestic dogs, can be found also in wild canids (e.g. wolves, foxes), procyonids (e.g. raccoons, kinkajous), ailurids (e.g. red pandas), ursids (e.g. black bears, giant pandas), mustelids (e.g. ferrets, minks), viverrids (e.g. civets, genets), hyaenids (e.g. spotted hyenas), and large felids (e.g. lions, tigers). Furthermore, besides infection with the closely related phocine distemper virus, seals can become infected by CDV. In some CDV outbreaks including the mass mortalities among Baikal and Caspian seals and large felids in the Serengeti Park, terrestrial carnivores including dogs and wolves have been suspected as vectors for the infectious agent. In addition, lethal infections have been described in non-carnivore species such as peccaries and non-human primates demonstrating the remarkable ability of the pathogen to cross species barriers. Mutations affecting the CDV H protein required for virus attachment to host-cell receptors are associated with virulence and disease emergence in novel host species. The broad and expanding host range of CDV and its maintenance within wildlife reservoir hosts considerably hampers disease eradication.

Phylodynamic analysis of the canine distemper virus hemagglutinin gene

Background

Canine distemper (CD) is one of the most contagious and lethal viral diseases in dogs. Despite the widespread use of vaccines, the prevalence of the CD virus (CDV) has increased at an alarming rate in recent years. In this phylodynamic study, we investigated the spatiotemporal modes of dispersal, viral demographic trends, and effectiveness of vaccines for CDV. A total of 188 full-length CDV hemagglutinin (H) gene sequences dataset were subjected to recombination analysis, including seven from modified live vaccine (MLV) strains and 12 from Taiwan specimens. After excluding the MLV strains and potential recombinant strains, alignments of 176 of 188 previous CDV strains were further used to analyze phylodynamic characteristics, and evidence of selection, and co-evolution.

Results

The CDV genotype consisted of MLV-associated genotypes such as America-1 and Rockborn-like strains, which were characterized by long terminal branches and no distinct geographical patterns among lineages. In contrast, wild-type isolates clustered into lineages with a spatiotemporal structure and short terminal branches. Co-circulation and extensive diversification were simultaneously observed. The sequence variation signature was shaped by both geographic diversity and host tropism. Codon 506 was identified as a multi-epistatic interacting in the H protein.

Conclusions

The topological signature revealed in this study suggests different epidemic scenarios. For example, a ladder-like backbone is a hallmark of directional selection, and cladogenesis at long terminal branches indicates the emergence of a surviving lineage. The stable effective viral population of CDV indicate the effectiveness of vaccines currently used to control the virus.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0491-9) contains supplementary material, which is available to authorized users.

Rapid and sensitive detection of canine distemper virus by one-tube reverse transcription-insulated isothermal polymerase chain reaction

Background

Canine distemper virus (CDV) has been associated with outbreaks of canine infectious respiratory disease in shelters and boarding kennel environments. POCKIT^TM Nucleic Acid Analyzer is a field-deployable device capable of generating automatically interpreted insulated isothermal polymerase chain reaction (iiPCR) results from extracted nucleic acid within one hour. In this study, reverse transcription iiPCR (RT-iiPCR) was developed to facilitate point-of-need diagnosis of CDV infection.

Results

Analytical sensitivity (limit of detection 95%) of the established CDV RT-iiPCR was about 11 copies of in vitro transcribed RNA per reaction. CDV RT-iiPCR generated positive signals from CDV, but not Bordetella bronchiseptica, canine parvovirus, canine herpesvirus, canine adenovirus 2, canine influenza virus (subtype H3N8), canine parainfluenza virus, and canine respiratory coronavirus. To evaluate accuracy of the established reaction in canine distemper clinical diagnosis, 110 specimens from dogs, raccoons, and foxes suspected with CDV infection were tested simultaneously by CDV RT-iiPCR and real-time RT-PCR. CDV RT-iiPCR demonstrated excellent sensitivity (100%) and specificity (100%), compared to real-time RT-PCR.

Conclusions

The results indicated an excellent correlation between RT-iiPCR and a reference real time RT-PCR method. Working in a lyophilized format, the established method has great potential to be used for point-of-care diagnosis of canine distemper in animals, especially in resource-limited facilities.