Nematode Transmission Research Articles

Host vegetation connectivity is decisive for the natural spread of pine wilt disease.

Pine wilt disease has caused significant economic, ecological, and social losses in China, but there is a notable lack of research on the dynamic process of its propagation and diffusion over long timescales. This study revealed the spatial and temporal spread of the natural invasion of pine wilt disease through an analysis of long time series at macroscopic scales. We analysed and verified by simulations the driving mechanisms of host and wind fields in the natural spread of pine wilt disease. The research findings indicate that from 1982 to 2019, the number of counties affected by pine wilt disease in the Yangtze River Delta region of China exhibited a pattern of 'steady increase-fluctuation-outbreak'. The host forest played a decisive role in the natural spread of the disease, while the wind field played a supporting role. The study revealed specific contributions from various factors, where host forest landscape connectivity, host forest area share, mean wind speed, and wind frequency accounted for 31.8%, 28.7%, 22.6%, and 8.8%, respectively. The interaction of increased host forest area and increased wind speed can significantly increase the risk of pine wilt disease transmission. To validate these findings, vectorial metacellular automata simulations of pine nematode transmission in the Yangtze River Delta were conducted, yielding results with an accuracy of 0.803. By quantifying the contribution of host forest connectivity to the natural spread of pine wilt disease, this research offers a scientific foundation and innovative insights for preventing and controlling its dissemination. © 2024 Society of Chemical Industry.

First report of Ophidascaris spp. (Class: Nematode) Infection in Wild-Caught Javanese Keelback Water Snake (Fowlea melanzostus) in Banyuwangi District

The javanese keelback water snake (Fowlea melanzostus) is a semi-aquatic reptile that often found in Indonesia and endemic to Java island. Water tiger snakes are usually kept as exotic pets. Wild caught javanese keelback water snakes have risks of spreading several disease agents that can be zoonotic, which is nematodiasis caused by Ophidascaris spp. This study aims to determine the prevalence level of Ophidascaris spp. infections in javanese keelback water snakes from Banyuwangi district. This study used a descriptive method with accidental sampling. The total sample in this study was 33 wild-caught javanese keelback water snakes. The identification method used is snake samples that have been collected are then euthanized and necropsied to check for nematode infections in the subcutan, muscular, and visceral part. The result showed that 28 samples were positive for nematode infection and 5 samples were negative with a prevalence rate of 84.84%. The nematodes that have been identified come from the genus Ophidascaris spp. Therefore, further research is needed to determine the incidence of nematode transmission in other wild caught snakes in Indonesia.

Expansion of Phalacrocorax carbo in reservoirs of the North-Eastern Kazakhstan

Initial data regarding the helminth fauna of the great cormorant (Phalacrocorax carbo) in the Pavlodar region of Kazakhstan have been acquired. The parasite fauna of the great cormorant is influenced by its diet of fish and consists of two fully developed helminth species - the nematode Contracaecum rudolphii Hartwich, 1964 and the cestode Ligula interrupta Rudolphi, 1810. An incidental finding was made when cestodes and their broken pieces were found in the intestines of cormorants. These cestodes were recognised as belonging to the genus Cyathocephalus, which is known to solely parasitize fish in its adult stage. Metacercariae of trematodes, specifically from the family Strigeidae, were found. These parasites are very new to fish intestines and are not commonly found in birds that consume fish. The growing population of great cormorants in the Ertis basin may introduce new kinds of helminths, some of which could have significant implications for the spread of diseases among animals. The prevalence of parasites in cormorants is a significant concern and has the potential to facilitate the transmission of nematodes and cestodes among other species, including fish-eating birds, poultry, fish, and aquatic invertebrates. This creates localised areas where nematodes and ligulidoses can thrive.

Host movement dominates the predicted effects of climate change on parasite transmission between wild and domestic mountain ungulates.

Climate change is shifting the transmission of parasites, which is determined by host density, ambient temperature and moisture. These shifts can lead to increased pressure from parasites, in wild and domestic animals, and can impact the effectiveness of parasite control strategies. Understanding the interactive effects of climate on host movement and parasite life histories will enable targeted parasite management, to ensure livestock productivity and avoid additional stress on wildlife populations. To assess complex outcomes under climate change, we applied a gastrointestinal nematode transmission model to a montane wildlife-livestock system, based on host movement and changes in abiotic factors due to elevation, comparing projected climate change scenarios with the historic climate. The wildlife host, Alpine ibex (Capra ibex ibex), undergoes seasonal elevational migration, and livestock are grazed during the summer for eight weeks. Total parasite infection pressure was more sensitive to host movement than to the direct effect of climatic conditions on parasite availability. Extended livestock grazing is predicted to increase parasite exposure for wildlife. These results demonstrate that movement of different host species should be considered when predicting the effects of climate change on parasite transmission, and can inform decisions to support wildlife and livestock health.

Comparison of transmission of Bursaphelenchus mucronatus via two different pathways from Monochamus saltuarius to host trees

Summary Bursaphelenchus xylophilus, the causative agent of pine wilt disease, and B. mucronatus are transmitted by Monochamus adults to host trees. Feeding and oviposition wounds made by vectors are the primary transmission pathways to trees. Monochamus saltuarius female adults carrying B. mucronatus were reared singly and allowed to mate with nematode-free males at 5-day intervals, to determine the ratio of nematodes transmitted via the two different pathways. The survival time, lifetime fecundity and other reproductive traits decreased with increasing initial nematode load (number of nematodes carried by a newly-emerged adult). Model selection indicated that numbers of B. mucronatus departing from M. saltuarius and of those transmitted to pine via oviposition and feeding wounds were closely related to the initial nematode load, which was affected by survival time and number of oviposition wounds constructed. Most temporal patterns of nematode departure and transmission via oviposition or feeding wounds from individual vectors had a peak in the medium and heavy initial nematode loads. The nematode departure curve was significantly similar in shape to each of the nematode transmission curves via oviposition and feeding wounds, which were not significantly similar to each other, for individual vectors. After M. saltuarius females began to construct the oviposition wounds, it was estimated that B. mucronatus was transmitted via the oviposition wounds at a probability of 0.767. If B. xylophilus is transmitted in the same way as B. mucronatus, the incidence of pine wilt disease by mature vectors would be much lower than in the case of no oviposition-related transmission.

Influence of meteorological and seasonal parameters on the activity of Culicoides paraensis (Diptera: Ceratopogonidae), an annoying anthropophilic biting midge and putative vector of Oropouche Virus in Rondônia, Brazilian Amazon

Biting midges of the genus Culicoides are insects of proven medical and veterinary importance, because of their role in the transmission of viruses, bacteria, protozoa and nematodes. Culicoides paraensis has been considered the main vector of the Oropouche Virus (OROV) in the urban cycle of the disease in the neotropics. Due to the great abundance of Culicoides spp. in the State of Rondônia and its epidemiological history of OROV, we investigated the biting activity in humans, the abundance as a function of meteorological parameters and seasonality, and the detection of OROV. Entomological collections occurred in three municipalities from Brazilian State of Rondônia: Porto Velho, Ariquemes, and Ouro Preto do Oeste. GLMM's were used to determine if Culicoides spp. abundance was predicted by seasonal, diurnal, and meteorological factors. Total RNA was extracted from insects and viral RNA detection was performed using the S segment as the target region of OROV via RT-qPCR. In total, 7315 individuals were captured and identified as C. paraensis. In the dry season, 1488 individuals (24.5%) were recorded, 4591 (75.5%) in the rainy season, with peaks of biting activity between 4pm and 6pm. All variables showed a significative effect on the midge abundance. The rainy season, temperature between 30 °C and 32 °C and relative air humidity between 75% and 85% were the main predictive parameters for capturing the highest average number of insects. Our results confirm diurnal activity of C. paraensis and its greatest abundance in rainy periods. No sample was positive for the OROV, which could be explained by the virus absence in local human populations, C. paraensis as a minor vector species in the sampled localities, and probable low rate of infection of biting midges. Our findings on hourly and seasonal biting activities can provide support to intervention actions regarding vector control and surveillance of this species. This was the first study to collect and analyze biting midges in a region where human OROV cases had already been detected, but without previous information on entomovirological surveillance.

Parasitism of terrestrial gastropods by medically-important nematodes in Brazil.

An ample variety of parasitic associations are found between mollusks and nematodes, in which the mollusks may act as intermediate, paratenic or definitive hosts. Some free-living nematodes, in particular those of the order Rhabditida, are also found frequently in terrestrial mollusks. The present study reviews the results of the parasitological testing on samples of terrestrial mollusks conducted at the Brazilian National Reference Laboratory for Schistosomiasis and Malacology between 2008 and 2021. The samples were supplied primarily by the public health authorities from the different regions of Brazil, but also by research institutions and general population. The mollusks were processed individually and the obtained larvae were identified from their morphology and, whenever necessary, by molecular analysis. A total of 1,919 service orders were registered during the period, including 19,758 mollusk specimens collected from 23 of the 26 Brazilian states, as well as the Federal District, totalizing 145 municipalities. There was a marked predominance of the synanthropic species that are widely distributed in Brazil-Achatina fulica (87.08%), Bulimulus tenuissimus (4.18%), Bradybaena similaris (2.06%), and Sarasinula linguaeformis (1.50%). Of the 16,750 terrestrial mollusks examined, nematodes were recorded in 1,308 service orders, with the predominance of the superfamily Metastrongyloidea, in 616 service orders. They included Angiostrongylus cantonensis, rat lungworm, which was found in 252 samples, and Aelurostrongylus abstrusus in 145 samples. Free-living nematodes were found in 952 samples, Ancylostoma caninum and Cruzia tentaculata (previously identified as Strongyluris sp.) in one and 275 samples, respectively, and other parasites in 210 samples (not identified). The results highlight the diversity of the associations between nematodes and terrestrial mollusks in Brazil, in particular invasive and synanthropic species, with emphasis on the giant African land snail, Achatina fulica. They demonstrate the prominent role of this species of mollusk in the transmission of medically-important nematodes, which affect the health of both humans and animals, in particular eosinophilic meningitis, which is caused by Angiostrongylus cantonensis. This reinforces the need for more studies, and justify the growing demand for information as well as parasitological diagnosis of this mollusk, given its wide distribution in Brazil and its impact as an urban pest.

Mathematical study of nematode transmission in pine trees through bark beetles

In this work, deterministic model of pine wilt affliction has been worked out qualitatively. On the basis of a threshold parameter known as the “Basic Reproduction Number,” we have analyzed the global behaviour of equilibria. To check the Robustness of proposed model it is applied on exact number of tainted pines in Korea during a decade. Estimated parameters have been used to identify the important factors that contribute significantly in disease enhancement. Artificial Neural Network (ANN), a very efficient technique, has been used for the fitness of curves representing tainted pines and vectors with respect to the most influential factors. In addition, optimal control problem is developed by assuming three controls. We have seen the efficiency of applied control measures numerically. Subject classification34D23, 34H05.

Dirofilaria immitis antigenemia and microfilaremia in Iberian wolves and red foxes from Portugal

BackgroundDirofilaria immitis is a parasitic nematode endemic in the Mediterranean countries, which causes cardiopulmonary dirofilariosis in wild and domestic animals. Despite being recognized hosts of D. immitis, wild carnivores such as wolves and foxes are frequently disregarded when considering a potential role in the transmission of these zoonotic nematodes. In Portugal, studies available regarding D. immitis circulation are scarce, likely underestimating its relevance. To add knowledge on this, we sought to assess Iberian wolves (Canis lupus signatus) and red foxes (Vulpes vulpes) from northern Portugal for D. immitis antigenemia and microfilaremia.MethodsBlood samples from 42 Iberian wolves and 19 red foxes were collected, during 2010–2012, in Peneda-Gerês National Park. Antigenemia was searched for by rapid antigen detection test kits (Uranotest Dirofilaria ®). Microfilaremia was assessed by polymerase chain reaction (PCR). Nucleic acids were extracted from blood using QIAamp® DNA Mini Kit (Qiagen), and DNA was screened for the presence of microfilaria using a conventional PCR targeting the 5.8S-internal transcribed spacer 2–28S regions, followed by bidirectional sequencing, Basic Local Alignment Search Tool analysis and phylogenetic analysis.ResultsThree red foxes had antigenemia, with an occurrence of 15.8% (95% confidence interval [CI] 3.4–39.6), while showing no evidence for the presence of microfilaremia. No wolf samples presented evidence for D. immitis antigenemia. Nevertheless, two wolves were positive for D. immitis microfilaremia (4.8%; 95% CI 0.6–16.2%) as revealed by PCR and confirmed by bidirectional sequencing.ConclusionsAlthough Dirofilaria microfilaremia in wolves does not necessarily correlate to an endangerment of the infected animal's health, positive individuals can act as a reservoir for further infection if the intermediate mosquito hosts are present. To the best of our knowledge, one single study had reported that wolves were suitable Dirofilaria hosts, but microfilaremia have never been reported.Graphical

Relationship between the initial number of carried Bursaphelenchus xylophilus and its transmission by Monochamus carolinensis with reference to virulence

Summary The pine wood nematode (PWN), Bursaphelenchus xylophilus, is the causative agent of pine wilt disease and is transmitted by cerambycid adults of the genus Monochamus. It is believed to have been introduced into Japan from North America in the 1900s and since then it has been devastating the native pine forests. By contrast, the epidemics of the disease have never occurred in pine forests native to North America in the original habitats, indicating no expression of virulence. To determine the evolutionary change in the transmission traits of PWN, the temporal pattern of PWN transmission to fresh branch sections of Pinus sylvestris was studied using 38 Monochamus carolinensis adults in Illinois, USA, and compared with previous studies on the PWN-M. alternatus and B. mucronatus-M. saltuarius systems in Japan. A great difference was observed in the initial nematode load among vectors irrespective of the three systems. The maximal numbers of PWN transmitted (5 days)−1 by individual vectors were greater and the efficiencies of nematode transmission and invasion were higher for the Japanese PWN-M. alternatus system than for the North American PWN-M. carolinensis system in two heavy classes of initial load of over 1000 nematodes. The proportion of PWN transmitted to healthy pine trees by reproductively immature female vectors was small (2.5-11.5%) in the three nematode-vector systems in most cases. The evolutionary changes in the transmission traits and the control of the range expansion of the PWN were discussed in relation to the expression of virulence.

Investigating parasite dynamics of migratory ungulates for sustaining healthy populations: Application to critically-endangered saiga antelopes Saiga tatarica

Contact between wild and domestic ungulates is increasing across rangelands, enabling disease co-transmission. Disease management is difficult given uncertainties in complex system behavior, limited empirical data, and logistical obstacles to interventions. We studied gastrointestinal nematode (GIN) transmission in a rangeland shared by both livestock and the critically-endangered migratory saiga antelope, Saiga tatarica, in order to model infection dynamics under current and plausible future scenarios of increasing livestock numbers, climate change and anti-helminth treatments. Our model was parameterised for trichostrongylid GIN – a cause of mortality and morbidity in ungulates globally - using data on observed faecal nematode egg output and host numbers and distribution. Results showed that seasonal saiga migration leads to asymmetry in parasite transmission, with the majority of GIN acquired by saigas in their autumn and winter range through prior pasture contamination from livestock. Consequently, reducing parasite burdens in livestock early in the season in these areas could disproportionately reduce cross-transmission to saigas. Early-season GIN suppression in livestock in the saiga's spring and summer range was predicted to have weaker effect on parasite transmission to saigas but reduces infections during the calving period, potentially increasing population health and resilience at this critical time. Optimally timed treatments could offset the effects of increasing livestock numbers on GIN infection pressure, while climate warming had only marginal impacts on GIN transmission under all scenarios. Our findings could support better understanding and mitigation of factors affecting saiga health and rural livelihoods. Our approach is transferable to other systems, particularly those with migratory hosts.

Phylogenetics of tobacco rattle virus isolates from potato (Solanum tuberosum L.) in the USA: a multi-gene approach to evolutionary lineage.

Tobacco rattle virus (TRV) is an important soil-borne virus of potato that is transmitted by stubby-root nematodes. TRV causes corky ringspot, a tuber disease of economic importance to potato production. Utilizing protein-coding regions of the whole genome and a range of computational tools, the genetic diversity, and population structure of TRV isolates from several potato-growing regions (Colorado, Idaho, Indiana, Minnesota, Nebraska, North Dakota, and Washington State) in the USA were determined. Phylogenetic analyses based on RNA2 nucleotide sequences, the coat protein (CP) and nematode transmission (2b) genes, showed geographical clustering of USA isolates with previously known American isolates, while European isolates grouped in a distinct cluster. This was corroborated by the observed genetic differentiation and infrequent gene flow between American and European isolates. Low genetic diversity was revealed among American isolates compared to European isolates. Phylogenetic clustering based on RNA1 genes (RdRp, RdRp-RT, and 1a) were all largely incongruent to that of 1b gene (virus suppressor of RNA silencing). This genetic incongruence suggested the influence of recombination. Furthermore, the RdRp, RdRp-RT, and 1a genes were predicted to be more conserved and under negative selection, while the 1b gene was less constrained. Different evolutionary lineages between TRV RNA1 and RNA2 genomic segments were revealed.

Metagenomic analysis of nepoviruses: diversity, evolution and identification of a genome region in members of subgroup A that appears to be important for host range

Data mining and metagenomic analysis of 277 open reading frame sequences of bipartite RNA viruses of the genus Nepovirus, family Secoviridae, were performed, documenting how challenging it can be to unequivocally assign a virus to a particular species, especially those in subgroups A and C, based on some of the currently adopted taxonomic demarcation criteria. This work suggests a possible need for their amendment to accommodate pangenome information. In addition, we revealed a host-dependent structure of arabis mosaic virus (ArMV) populations at a cladistic level and confirmed a phylogeographic structure of grapevine fanleaf virus (GFLV) populations. We also identified new putative recombination events in members of subgroups A, B and C. The evolutionary specificity of some capsid regions of ArMV and GFLV that were described previously and biologically validated as determinants of nematode transmission was circumscribed in silico. Furthermore, a C-terminal segment of the RNA-dependent RNA polymerase of members of subgroup A was predicted to be a putative host range determinant based on statistically supported higher π (substitutions per site) values for GFLV and ArMV isolates infecting Vitis spp. compared with non-Vitis-infecting ArMV isolates. This study illustrates how sequence information obtained via high-throughput sequencing can increase our understanding of mechanisms that modulate virus diversity and evolution and create new opportunities for advancing studies on the biology of economically important plant viruses.

Ascaris suum Informs Extrasynaptic Volume Transmission in Nematodes.

Neural circuit synaptic connectivities (the connectome) provide the anatomical foundation for our understanding of nematode nervous system function. However, other nonsynaptic routes of communication are known in invertebrates including extrasynaptic volume transmission (EVT), which enables short- and/or long-range communication in the absence of synaptic connections. Although EVT has been highlighted as a facet of Caenorhabditis elegans neurosignaling, no experimental evidence identifies body cavity fluid (pseudocoelomic fluid; PCF) as a vehicle for either neuropeptide or biogenic amine transmission. In the parasitic nematode Ascaris suum, FMRFamide-like peptides encoded on flp-18 potently stimulate female reproductive organs but are expressed in cells that are anatomically distant from the reproductive organ, with no known synaptic connections to this tissue. Here we investigate nonsynaptic neuropeptide signaling in nematodes mediated by the body cavity fluid. Our data show that (i) A. suum PCF (As-PCF) contains a catalog of neuropeptides including FMRFamide-like peptides and neuropeptide-like proteins, (ii) the A. suum FMRFamide-like peptide As-FLP-18A dominates the As-PCF peptidome, (iii) As-PCF potently modulates nematode reproductive muscle function ex vivo, mirroring the effects of synthetic FLP-18 peptides, (iv) As-PCF activates the C. elegans FLP-18 receptors NPR-4 and -5, (v) As-PCF alters C. elegans behavior, and (vi) FLP-18 and FLP-18 receptors display pan-phylum distribution in nematodes. This study provides the first direct experimental evidence to support an extrasynaptic volume route for neuropeptide transmission in nematodes. These data indicate nonsynaptic signaling within the nematode functional connectome and are particularly pertinent to receptor deorphanization approaches underpinning drug discovery programs for nematode pathogens.

DNA-based blood meal analysis of Culicoides (Diptera: Ceratopogonidae) species from Jamari National Forest, Southwestern Amazon, Brazil

Culicoides biting midges are insects involved in the transmission of filarial nematodes, protozoans, and viruses. Greater knowledge of Culicoides blood meal sources could improve our understanding of parasite transmission cycles. Our study used molecular tools to evaluate the blood meal sources of Culicoides biting midges from sylvatic environments. This study was conducted in Jamari National Forest, Rondônia, Brazil. Culicoides were captured using HP light traps positioned at ground level (1.5 m above ground) and in canopy (15 m above ground). To identify blood meal sources, females were subjected to DNA extraction and PCR targeting the cytb gene fragment, and the obtained sequences were analyzed and compared with sequences from GenBank. DNA extraction and PCR were performed on 455 Culicoides females, and blood meal sources were identified in 186 females. Thirty Culicoides specimens were collected from the Potosi trail and 156 were collected from the Santa Maria trail. A total of 22 species were captured; all 22 species were collected in canopy (100%) but only three species were collected at ground level (13.6%). The cytb fragment was amplified in 162 of 186 samples. Sample sequencing identified cytb DNA from nine blood-meal sources: Pauxi sp., Psophia viridis, Ramphastos tucanus tucanus, Choloepus didactylus, Choloepus hoffmanni, Tamandua tetradactyla, Ateles chamek, Homo sapiens and Pithecia irrorata. We observed that several different blood meal sources were utilized by a high diversity of Culicoides species. The abundance of Culicoides in the canopy may be related to the fact that the majority of blood meal hosts feed in treetops. We observed that C. (Hoffmania) sp. and C. coutinhoi tend to be more generalist, feeding on a range of mammals and piciform, gruiform and galliform birds. This data improves our knowledge of the feeding profile of biting midges from forest environments and should serve as a future basis for defining zoonotic transmission cycles.

The prevalence of intestinal nematodes among red foxes (Vulpes vulpes) in north-western Poland

BackgroundThe red fox (Vulpes vulpes) is widely distributed in the Northern Hemisphere and Australia. The presence of nematode-infected foxes in urbanized areas increases the risk of transmission of nematodes to domestic dogs and thus, to humans. The aim of this study was to determine the prevalence and species composition of intestinal nematodiasis in red foxes in Western Pomerania, a province in north-western Poland. The intestinal contents of 620 red foxes killed during a government reduction shooting programme were examined for adult nematodes using the sedimentation and counting technique (SCT).ResultsIntestinal nematodes, including Toxocara canis, Toxascaris leonina, Uncinaria stenocephala and Trichuris vulpis, were found in 77.3% (95% CI 73.8–80.4%) of the examined foxes with a mean infection burden of 20.1 nematode per animal. Male and female foxes had similar infection burdens.ConclusionsThe nematodes are present in high prevalence and intensity among foxes in north-western Poland. Furthermore, this high prevalence of nematodes in foxes may likely constitute a health risk to humans and domestic animals due to increasing fox densities in urban and periurban areas.

Transcriptomic Insights into the Insect Immune Response to Nematode Infection.

Insects in nature interact with a wide variety of microbial enemies including nematodes. These include entomopathogenic nematodes that contain mutualistic bacteria and together are able to infect a broad range of insects in order to complete their life cycle and multiply, filarial nematodes which are vectored by mosquitoes, and other parasitic nematodes. Entomopathogenic nematodes are commonly used in biological control practices and they form excellent research tools for understanding the genetic and functional bases of nematode pathogenicity and insect anti-nematode immunity. In addition, clarifying the mechanism of transmission of filarial nematodes by mosquitoes is critical for devising strategies to reduce disease transmission in humans. In all cases and in order to achieve these goals, it is vital to determine the number and type of insect host genes which are differentially regulated during infection and encode factors with anti-nematode properties. In this respect, the use of transcriptomic approaches has proven a key step for the identification of insect molecules with anti-nematode activity. Here, we review the progress in the field of transcriptomics that deals with the insect response to nematode infection. This information is important because it will expose conserved pathways of anti-nematode immunity in humans.

Co-occurrence of Eutrombicula alfreddugesi and Oswaldofilaria chabaudi in Tropidurus torquatus and first report of microfilariae in the chigger mite: possible evidence of a lifecycle pathway?

While much attention has been paid to vector-borne filariasis, diseases that threaten millions of people in tropical and subtropical countries, the literature on host-parasite associations and transmission strategies of filarial nematodes in wildlife is scarce. Here, we report the co-occurrence of chigger mites (Eutrombicula alfreddugesi) and onchocercid nematodes (Oswaldofilaria chabaudi) parasitizing the lizard Tropidurus torquatus in the State of Minas Gerais, Brazil. Examination of chiggers established, for the first time, the occurrence of microfilariae in trombiculid mites (Trombiculidae). These larvae were morphologically similar to those recovered from adult females of O. chabaudi. The current evidence suggests that chiggers do not play a role in the transmission of filarioid nematodes, but rather act as accidental or dead-end hosts. Nevertheless, considering the polyphagous nature of trombiculid mites, similar to blood-sucking insects involved in the transmission of several infectious diseases, further studies may shed light on the potential role of chiggers as vectors of filarioids.

Demographics of the semi-slug Parmarion martensi, an intermediate host for Angiostrongylus cantonensis in Hawai'i, during laboratory rearing.

The semi-slug, Parmarion martensi, is an intermediate host of the zoonotic nematode, Angiostrongylus cantonensis, the aetiological agent of neuroangiostrongyliasis or rat lungworm disease in humans. Rearing methods were developed for P. martensi to facilitate studies on nematode transmission and control. Parmarion martensi exhibited high survivorship when reared on a diet of dog food and fresh fruits and vegetables in temperature-controlled cabinets at 21.4°C, 98% relative humidity and 12:12 L:D cycle. Rearing containers were lined with moist paper towels for substrate and plastic pots were provided for hiding/resting and egg-laying. Under these conditions, time to first reproduction was 165.3 ± 12.3 days, fecundity was approximately 34.5 ± 7.8 eggs per adult, and hatch rate was 52.7 ± 3.2%. Survivorship post egg hatch was 86.2 ± 2.9% at 30 days (neonates had a mortality rate of about 14%) and 99% thereafter for up to a year. The demographics of laboratory-reared and wild-caught P. martensi were similar except for the weight of reproductive adults, which was significantly higher in laboratory-reared adults (4.0 ± 0.2 g) than in field-collected adults (1.5 ± 0.1 g).

Effectiveness of clear‐cuttings in non‐fragmented pine forests in relation to EU regulations for the eradication of the pine wood nematode

Abstract The invasive pine wood nematode (PWN) Bursaphelenchus xylophilus is one of the most serious threats to pine forests across the world. Detected in Europe in 1999, it has largely spread despite containment measures. Following the European Union regulations, the requested eradication measure is to fell, remove and dispose of all susceptible plants within a clear‐cut zone (CCZ) of a radius of 500 m around any infected tree. This measure is controversial since its effectiveness is questioned. An individual‐based model, describing the dispersal of the nematode vector and the nematode transmission, was used to estimate the relationship between the radius and the effectiveness of the CCZ at eradicating the PWN. Clear‐cutting of a 500‐m radius is poorly effective in non‐fragmented pine forests since it reduces the number of PWN transmissions by only 0.6%–11.5%. To significantly reduce the number of transmissions, the radius should be between 14 and 38 km, which is not technically nor ethically feasible. Policy implications. Our results, based on model simulations at a fine spatial scale, prove that clear‐cutting susceptible trees 500 m around any infested tree—as requested by EU regulation to eradicate the PWN—is not effective in large and continuous pine forests. Instead, strengthened surveillance and sanitation felling could be explored.