Analysis of Exotic Parasitic Infection in a Large Group of Imported Dogs Following an Animal Welfare Investigation

Background: Increased dog relocation can cause dissemination of parasite and vector populations and this is being recognised in countries across Northern Europe, including the UK. Data regarding the prevalence of exotic infections entering the UK would be beneficial to vets to help assess pets entering the UK from abroad, and to help calculate risk of establishment of novel pathogens. One such group of dogs were seized as part of an RSPCA-led animal welfare investigation and blood tested for exotic pathogens. Methods: As part of the RSPCA investigation, 151 dogs were removed from the site. Blood tests were performed for Babesia. canis, Ehrlichia canis, Hepatozoon canis and Leishmania infantum by PCR, Br.canis by antibody serology and D.immitis by blood antigen. In addition to pathogen screening, a serology titre for Rabies was measured for each dog. A clinical examination was performed by a veterinary surgeon and clinical signs recorded. Clinical signs data were analysed by the Fisher-Freeman-Halton Exact TestResults: Overall, 24% of the dogs tested positive for an infection. Two dogs were positive for Br.canis antibodies and had no clinical signs indicative of infection. Leishmania infantum was identified in 10.5% of dogs with all but two cases being diagnosed in dogs whose microchip originated in Romania. Hepatozoon canis was identified in 9.6% of dogs, all of which had a Romanian microchip. Dirofilaria immitis was identified in 4.1% of dogs, B.canis in 2.3% of dogs and E.canis was only present in 1.5% of dogs tested. Only four dogs were found to have co-infections. No significant association was found between the pathogens detected and presenting clinical signs. Conclusions: This study demonstrates a range of exotic pathogens entering the UK including Br.canis and demonstrates the importance of screening imported dogs. The emphasis for early recognition of exotic pathogens in imported dogs has relied on screening based on relevant clinical signs and the country of origin. While these factors are useful, this study demonstrated no significant association between presenting clinical signs and the pathogens carried.

Genomic Biosurveillance Detects A Sexual Hybrid in the Sudden Oak Death Pathogen

Invasive exotic pathogens pose a threat to trees and forest ecosystems worldwide1, hampering the provision of essential ecosystem services such as carbon sequestration and water purification2. Hybridization is a major evolutionary force that can drive the emergence of pathogens3. Phytophthora ramorum, an emergent pathogen that causes the sudden oak and larch death, spreads as reproductively isolated divergent clonal lineages. Sexual recombination has never been reported in this pathogen under natural conditions and laboratory crosses have yielded unfit progenies, suggesting postzygotic barriers to hybridization. Here we report the discovery in a plant nursery of novel variants of P. ramorum that are the result of homoploid hybridization via sexual recombination between North American and European lineages of the pathogen. We show that these hybrids are viable, can infect plants and produce spores for long-term survival and propagation. Genome sequencing revealed novel genotypic combinations, not present in the parental lineages, at 54,515 single nucleotide polymorphism loci. More than 6000 of the novel genotypes at these loci are predicted to have a functional impact in genes associated with host infection, including effectors, carbohydrate-active enzymes and proteases. We also observed post-meiotic mitotic recombination that could generate additional genotypic and phenotypic variation and contribute to homoploid hybrid speciation. Our study highlights the importance of plant pathogen biosurveillance to detect novel variants and inform management and control.

Pre-invasion assessment of exotic bark beetle-vectored fungi to detect tree-killing pathogens

Exotic diseases and pests of trees have caused continental-scale disturbances in forest ecosystems and industries, and their invasions are considered largely unpredictable. We tested the concept of pre-invasion assessment of not-yet invasive organisms, which enables empirical risk assessment of potential invasion and impact. Our example assesses fungi associated with Old World bark and ambrosia beetles and their potential to impact North American trees. We selected 55 Asian and European scolytine beetle species using host-use, economic, and regulatory criteria. We isolated 111 of their most consistent fungal associates and tested their effect on four important Southeastern American pine and oak species. Our test dataset found no highly virulent pathogens that should be classified as an imminent threat. Twenty-two fungal species were minor pathogens, which may require context-dependent response for their vectors at North American borders, while most of the tested fungi displayed no significant impact. Our results are significant in three ways: they ease the concerns over multiple overseas pests suspected of heightened potential risk; they provide basis for focus on the prevention of introduction and establishment of species that may be of consequence; and they demonstrate that pre-invasion assessment, if scaled up, can support practical risk assessment of exotic pathogens.

Phytophthora Diversity in Pennsylvania Nurseries and Greenhouses Inferred from Clinical Samples Collected over Four Decades

The increasing movement of exotic pathogens calls for systematic surveillance so that newly introduced pathogens can be recognized and dealt with early. A resource crucial for recognizing such pathogens is knowledge about the spatial and temporal diversity of endemic pathogens. Here, we report an effort to build this resource for Pennsylvania (PA) by characterizing the identity and distribution of Phytophthora species isolated from diverse plant species in PA nurseries and greenhouses. We identified 1137 Phytophthora isolates cultured from clinical samples of >150 plant species submitted to the PA Department of Agriculture for diagnosis from 1975 to 2019 using sequences of one or more loci and morphological characteristics. The three most commonly received plants were Abies, Rhododendron, and Pseudotsuga. Thirty-six Phytophthora species identified represent all clades, except 3 and 10, and included a distinct subgroup of a known species and a prospective new species. Prominent pathogenic species such as P. cactorum, P. cinnamomi, P. nicotianae, P. drechsleri, P. pini, P. plurivora, and P. sp. kelmania have been found consistently since 1975. One isolate cultured from Juniperus horizontalis roots did not correspond to any known species, and several other isolates also show considerable genetic variation from any authentic species or isolate. Some species were isolated from never-before-documented plants, suggesting that their host range is larger than previously thought. This survey only provides a coarse picture of historical patterns of Phytophthora encounters in PA nurseries and greenhouses because the isolation of Phytophthora was not designed for a systematic survey. However, its extensive temporal and plant coverage offers a unique insight into the association of Phytophthora with diverse plants in nurseries and greenhouses.

Exotic Species and Autochthonous Parasites: Trichostrongylus Retortaeformis in Eastern Cottontail

Introduction: A parasite community is usually well adapted and specific to the host species they co-evolved with. Although exotic pathogens infecting autochthonous species have been documented, the infection of an alien species with native parasites is rare in lagomorphs. Trichostrongylus retortaeformis is a nematode parasite infecting the small intestine of domestic and wild lagomorphs in Europe. Methods: Thirty-two Eastern cottontails from a naturalized population in Italy were processed to describe the gastrointestinal parasite community. Results and discussions: T. retortaeformis is reported for the first time in the Eastern cottontail Sylvilagus floridanus introduced to Europe. The Eastern cottontail is an invasive lagomorph, living in sympatry with the autochthonous European brown hare in certain areas of Italy. This study provides new insights into the dynamics of parasite communities of native and alien lagomorph species in sympatric areas.

Canine olfactory detection of a vectored phytobacterial pathogen, Liberibacter asiaticus, and integration with disease control

Early detection and rapid response are crucial to avoid severe epidemics of exotic pathogens. However, most detection methods (molecular, serological, chemical) are logistically limited for large-scale survey of outbreaks due to intrinsic sampling issues and laboratory throughput. Evaluation of 10 canines trained for detection of a severe exotic phytobacterial arboreal pathogen, Candidatus Liberibacter asiaticus (CLas), demonstrated 0.9905 accuracy, 0.8579 sensitivity, and 0.9961 specificity. In a longitudinal study, cryptic CLas infections that remained subclinical visually were detected within 2 wk postinfection compared with 1 to 32 mo for qPCR. When allowed to interrogate a diverse range of in vivo pathogens infecting an international citrus pathogen collection, canines only reacted to Liberibacter pathogens of citrus and not to other bacterial, viral, or spiroplasma pathogens. Canines trained to detect CLas-infected citrus also alerted on CLas-infected tobacco and periwinkle, CLas-bearing psyllid insect vectors, and CLas cocultured with other bacteria but at CLas titers below the level of molecular detection. All of these observations suggest that canines can detect CLas directly rather than only host volatiles produced by the infection. Detection in orchards and residential properties was real time, ∼2 s per tree. Spatiotemporal epidemic simulations demonstrated that control of pathogen prevalence was possible and economically sustainable when canine detection was followed by intervention (i.e., culling infected individuals), whereas current methods of molecular (qPCR) and visual detection failed to contribute to the suppression of an exponential trajectory of infection.