Local terrestrial snails as natural intermediate hosts of the zoonotic parasite Angiostrongylus cantonensis in the new European endemic area of Valencia, Spain

AIM

The rat lungworm, Angiostrongylus cantonensis, has recently been found in the city of Valencia, parasitizing rats, Rattus norvegicus and Rattus rattus, its natural definitive hosts. This is the first finding of this zoonotic nematode in continental Europe. After informing local and national health authorities, the collection of local terrestrial snails took place with the aim of elucidating their potential role as intermediate hosts of A. cantonensis.

METHODS AND RESULTS

A total of 145 terrestrial snails, belonging to the species Cernuella virgata, Cornu aspersum, Eobania vermiculata, Otala punctata, Pseudotachea splendida, Rumina decollata and Theba pisana, were randomly collected between May and December 2022 in public gardens, parks and orchards in six districts of Valencia, in five of which A. cantonensis had been reported previously in rats. Once collected and identified, the snails were frozen at -20°C. Subsequently, the DNA was isolated and screened by PCR using specific primers targeting the A. cantonensis COI gene. Seven individual snails, belonging to the species C. virgata, C. aspersum and T. pisana, were positive, for an overall prevalence of 4.8%. The PCR product from one of them was sequenced by Sanger sequencing.

CONCLUSIONS

The three positive terrestrial snail species are among the edible species that are frequently included in various dishes in Spain. C. virgata is reported as a previously unrecorded intermediate host and should be added to the list of more than 200 species of terrestrial snails that have been reported worldwide as intermediate hosts of the rat lungworm. Considering that these terrestrial snails may release infective larvae of A. cantonensis on leafy green vegetables on which they feed and during their handling and preparation for consumption, prophylactic measures to prevent human neuroangiostrongyliasis in Valencia and other regions to which this zoonotic parasite may spread are recommended.

A review of the genus Vitrea Fitzinger, 1833 (Gastropoda, Eupulmonata, Pristilomatidae) in Serbia: diversity, distribution and the description of a new species

In this paper, the genus Vitrea Fitzinger, 1833 in Serbia is reviewed. All previous literature data on this genus from Serbia are summarised and used to discuss its distribution in the country and create distribution maps, supplemented by new material collected by the authors. All Serbian species are figured. For each species, a brief description of the examined specimens, data on previous findings in Serbia, the material (including types) that were analysed, the distribution and habitats in Serbia they inhabit, as well as remarks on specific species are given. A new species, Vitreavirgo Gojšina & Dedov, sp. nov., is described from a pit on Mt. Devica in eastern Serbia. Vitreapygmaea (O. Boettger, 1880) is reported for the first time for the territory of Serbia. As some Vitrea species have a narrow geographical range and prefer certain habitats, they are particularly vulnerable to habitat changes, which is also discussed in the paper. An identification key for all hitherto known Serbian species is given.

Genetic diversity of a short-ranged endemic terrestrial snail

The factors that influence population structure and connectivity are unknown for most terrestrial invertebrates but are of particular interest both for understanding the impacts of disturbance and for determining accurate levels of biodiversity and local endemism. The main objective of this study was to determine the historical patterns of genetic differentiation and contemporary gene flow in the terrestrial snail, Austrochloritis kosciuszkoensis (Shea & O. L. Griffiths, 2010). Snails were collected in the Mt Buffalo and Alpine National Parks in Victoria, in a bid to understand how populations of this species are connected both within continuous habitat and between adjacent, yet separate environments. Utilising both mitochondrial DNA (mtDNA) and single nucleotide polymorphism (SNP) data, the degree of population structure was determined within and between sites. Very high levels of genetic divergence were found between the Mt Buffalo and Alpine snails, with no evidence for genetic exchange detected between the two regions, indicating speciation has possibly occurred between the two regions. Our analyses of the combined mtDNA and nDNA (generated from SNPs) data have revealed patterns of genetic diversity that are consistent with a history of long-term isolation and limited connectivity. This history may be related to past cycles of changes to the climate over hundreds of thousands of years, which have, in part, caused the fragmentation of Australian forests. Within both regions, extremely limited gene flow between separate populations suggests that these land snails have very limited dispersal capabilities across existing landscape barriers, especially at Mt Buffalo: here, populations only 5 km apart from each other are genetically differentiated. The distinct genetic divergences and clearly reduced dispersal ability detected in this data explain the likely existence of at least two previously unnamed cryptic Austrochloritis species within a 30-50 km radius, and highlight the need for more concentrated efforts to understand population structure and gene flow in terrestrial invertebrates.

Contact toxicity and biochemical impact of metaldehyde against the white garden snail Theba pisana (Müller, 1774)

BACKGROUND

Terrestrial snails are one of the most damaging threats to sustainable agriculture. Chemical control using molluscicides is the main approach used to combat these agricultural pests. Metaldehyde is the active ingredient in most snail control products in use. However, its toxicity indices and mode of action have scarcely been investigated. For the first time, we characterized the metaldehyde contact toxicity indices against the white garden snail Theba pisana. The biochemical impact of metaldehyde on acetylcholinesterase (AChE), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), alkaline phosphatase (ALP) and glutathione S-transferase (GST) activities and the lipid peroxidation (LPO) level was investigated.

RESULTS

The median lethal dose (LD₅₀ ) values at 24, 48 and 72 h of treatment were 11.33, 8.53, and 6.87 μg g^-1 body weight (BW), respectively; while, the median lethal time (LT₅₀ ) values were 88.16, 55.85, and 25.67 h when doses of 6, 8, and 12 μg g^-1 BW were applied, respectively. In the snails treated with 2.83 and 5.67 μg g^-1 BW (¼ and ½ LD₅₀ at 24 h of treatment) and 2.13 and 4.27 μg g^-1 BW (¼ and ½ LD₅₀ at 48 h of treatment), higher AChE, GST, AST, ALT, and ALP activities as well as higher levels of LPO were observed compared with that of untreated snails.

CONCLUSION

Metaldehyde displayed dose- and time-dependent contact toxicity. The biochemical results suggest that metaldehyde may have neurotoxic and cytotoxic actions in terrestrial snails. Application of metaldehyde in ways that could control pest snails and slugs and reduce its negative impact on the environment are discussed. © 2021 Society of Chemical Industry.

Antimicrobial properties of terrestrial snail and slug mucus

Snail and slug mucus is a viscous-elastic substance secreted by specific glands with adhesive and lubricants properties that allows them to adhere tenaciously to many different surfaces. It has been used since ancient times for care and human health and it is still very important in traditional and folkloristic medicine. Recently, mucus from snail and slugs and its protein and components have been subjected to some investigations on their antibacterial, antiviral and antifungal activity due to extensive traditional uses and for a future application in medicine. Antimicrobial activities of crude mucus, and its components, against different microorganism have been reported, showing antimicrobial activities that lead their potential employment in several fields as natural additives. The purpose of this Review is to summarize the results of antimicrobial studies of snail and slug mucus and its compounds from the first scientific applications to the isolation of the single components in order to better understand its application and propose an employment in future studies as a natural antimicrobial agent.