The genetic mechanisms of how free-living nematodes evolved into parasites are unknown. Current genetic model nematodes (e.g.Caenorhabditis elegans) are not well suited to provide the answer, and mammalian parasites are expensive and logistically difficult to maintain. Here we propose the terrestrial gastropod parasitePhasmarhabditis hermaphroditaas a new alternative to study the evolution of parasitism, and outline the methodology of how to keepP. hermaphroditain the lab for genetic experiments. We show thatP. hermaphrodita(and several otherPhasmarhabditisspecies) are easy to isolate and identify from slugs and snails from around the UK. We outline how to make isogenic lines using ‘semi-natural’ conditions to reduce in-lab evolution, and how to optimize growth using nematode growth media (NGM) agar and naturally isolated bacteria. We show thatP. hermaphroditais amenable to forward genetics and thatuncandsmamutants can be generated using formaldehyde mutagenesis. We also detail the procedures needed to carry out genetic crosses. Furthermore, we show natural variation within ourPhasmarhabditiscollection, with isolates displaying differences in survival when exposed to high temperatures and pH, which facilitates micro and macro evolutionary studies. In summary, we believe that this genetically amenable parasite that shares many attributes withC. elegansas well as being in Clade 5, which contains many animal, plant and arthropod parasites, could be an excellent model to understand the genetic basis of parasitism in the Nematoda.

A parasitological survey of terrestrial slugs and snails was conducted at popular dog walking locations across the city of Nottingham, with the intensions of finding gastropods infected with parasites of medical (or veterinary) importance such as lungworm (metastrongyloid nematodes) and trematodes. A total of 800 gastropods were collected from 16 sites over a 225 km²area. The extracted nematodes and trematodes were identified by molecular barcoding. Of the 800 gastropods collected, 227 were infected (172 had nematode infections, 37 had trematode infections and 18 had both nematode and trematode infections). Of the nematode infected gastropods genotyped, seven species were identified,Agfa flexilis,Angiostoma gandavense,Angiostoma margaretae,Cosmocerca longicauda,Phasmarhabditis hermaphrodita,Phasmarhabditis neopapillosaand an unknown Cosmocercidae species. Of the trematode infected gastropods genotyped, four species were identified,Brachylaima arcuate,Brachylaima fuscata,Brachylaima mesostomaand an unknown Plagiorchioidea species. No lungworm species were found within the city of Nottingham. To our knowledge, this study represents the first survey of gastropod-associated nematodes and trematodes in the East midlands of the United Kingdom.

Summary: Phasmarhabditis hermaphrodita is a lethal parasite of several slug species and has been formulated into a biological control agent for farmers and gardeners. Phasmarhabditis hermaphrodita responds to slug faeces, mucus and volatile cues to find hosts in soil. However, these results have only focused on one strain of P. hermaphrodita (DMG0001). We exposed four strains of P. hermaphrodita (and DMG0001), three strains of P. neopapillosa and two strains of P. californica to mucus from seven common slug species. Furthermore, we investigated whether there was a relationship between chemoattraction and the numbers of offspring that were produced on each host species. Natural isolates of P. hermaphrodita differed in their preference of slug species whereas P. neopapillosa tended to prefer Arion sp. and strains of P. californica displayed striking differences in their responses. The reasons for positive chemoattraction to mucus were not due to higher numbers of offspring produced on these hosts.

Phasmarhabditis hermaphrodita is a parasitic nematode of terrestrial gastropods that has been formulated into a biological control agent for farmers and gardeners to kill slugs and snails. In order to locate slugs it is attracted to mucus, faeces and volatile cues; however, there is no information about whether these nematodes are attracted to snail cues. It is also unknown how wild isolates of P. hermaphrodita or different Phasmarhabditis species behave when exposed to gastropod cues. Therefore, we investigated whether P. hermaphrodita (commercial and wild isolated strains), P. neopapillosa and P. californica were attracted to mucus from several common snail species (Cepaea nemoralis, Cepaea hortensis, Arianta arbustorum and Cornu aspersum). We also examined whether snails (C. aspersum) collected from different locations around the UK differed in their attractiveness to wild isolates of P. hermaphrodita. Furthermore, we also investigated what properties of snail mucus the nematodes were attracted to, including hyaluronic acid and metal salts (FeSO₄, ZnSO₄, CuSO₄ and MgSO₄). We found that the commercial strain of P. hermaphrodita responded poorly to snail mucus compared to wild isolated strains, and C. aspersum collected from different parts of the UK differed in their attractiveness to the nematodes. We found that Phasmarhabditis nematodes were weakly attracted to all metals tested but were strongly attracted to hyaluronic acid. In a final experiment we also showed that pharmacological manipulation of cyclic guanosine monophosphate (cGMP) increased chemoattraction to snail mucus, suggesting that the protein kinase EGL-4 may be responsible for Phasmarhabditis sp. chemoattraction.

Biomphalaria pfeifferi snails serve as the major intermediate host for intestinal schistosomiasis in Sudan. The genetic structure and infection status of 163 B. pfeifferi collected from six localities in Gezira State, Sudan (East Gezira, Greater Wadmedani, Hasahisa, North Umelgura, South Gezira, and Managil) were characterized. Cytochrome oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) mitochondrial genes were used for B. pfeifferi molecular identification and genetic diversity investigation. Schistosoma mansoni infection was detected using the traditional cercarial shedding and molecular methods (Sm^F/R primers). Five COI haplotypes and ten 16S haplotypes were identified, with haplotype diversity of 0.50 for COI and 0.11 for 16S. High evolutionary divergence was observed between groups (Fst = 0.94) for the COI, and low genetic divergence (Fst = 0.04) for the 16S, indicating genetic divergence among Sudanese B. pfeifferi, with the 16S showing lower divergence than the COI, consistent with a post-bottleneck population expansion. Cercarial shedding detected an overall infection prevalence of 3.6% (8/219), with only two snails from Hasahisa shedding S. mansoni cercariae. The Sm^F/R primers revealed a higher infection prevalence of 7.4% (12/163), with all S. mansoni positive samples found at the Hasahisa site. Findings highlight the value of molecular diagnostic tools for accurate surveillance and emphasize the need for site-specific control strategies.

Background: Golden apple snails (Gastropoda: Ampullariidae: Pomacea ) were introduced into China in the 1980s for aquaculture and have since become widespread agricultural pests across East Asia. In addition to their invasive impact, they are a key intermediate host of the rat lungworm Angiostrongylus cantonensis (Secernentea: Angiostrongylidae) in China, the causative agent of eosinophilic meningitis in humans. Methods: We conducted a malacological survey of 55 freshwater sites across Shanghai and neighboring East China provinces to assess Pomacea distribution, genetic diversity, and A. cantonensis infection status. A total of 700 Pomacea snails were examined for A. cantonensis using traditional lung microscopy and molecular xenomonitoring (PCR and LAMP). Mitochondrial COI barcoding was performed on 200 individuals from 20 high-density sites to assess species composition and genetic diversity. Results: Pomacea snails were found at 81.8% (45/55) of sites surveyed. No A. cantonensis infections were detected by microscopy or molecular assays. Genetic analyzes revealed three Pomacea species ( P. canaliculata , P. maculata , and P. occulta ) and nine distinct COI haplotypes. Pomacea canaliculata was the most common and genetically diverse species, with four unique haplotypes (H5–H8) occurring only in Shanghai, indicative of recent introductions. Overall, populations showed moderate haplotype diversity ( Hd = 0.73) and population structure ( F _ST = 0.24). Conclusions: Although no A. cantonensis infections were detected in the snails examined in this survey, these negative findings do not preclude the possibility of low-prevalence or newly emerging infections. The wide distribution and high genetic diversity of Pomacea populations across Shanghai and East China highlight that suitable hosts are already well-established, emphasizing the ongoing risk of parasite introduction and spread into currently nonendemic regions. Continued molecular surveillance, public awareness, and strengthened biosecurity measures remain essential to effectively manage invasive snail populations and mitigate future public health threats. Graphical