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Semperula wallacei (Issel, 1874) is a species of terrestrial slug that occurs in southeast China and the Pacific Basin and is the only species of its genus that occurs beyond the Oriental region and to the east of Wallace's line in the Australian region, where it has probably been introduced. In this study, we report for the first time S. wallacei as an intermediate host for Angiostrongylus cantonensis (Chen, 1935) based on histological and molecular analyses of slugs from Tuamasaga, Samoa, deposited at the Medical Malacological Collection (Fiocruz-CMM). DNA was obtained from the deparafinized tissues scraped from specimen slides. Polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) targeted to the internal transcribed spacer 2 ( ITS2 ) region were carried out using the restriction enzyme Cla I. The RFLP profile observed for our larval specimen of S. wallacei was identical to the profile previously established for A. cantonensis , demonstrating that S. wallacei can be naturally infected with A. cantonensis and is likely to be an intermediate host for this parasitic nematode species in the field. The potential for geographical range expansion of S. wallacei in the Pacific Basin, its small size, and the general role of veronicellids as crop pests and hosts of nematodes, indicate the significance of S. wallacei as an invasive species in the Pacific Basin. Our work also highlights the importance of biological collections for investigating the environmental impact of invasive species on agriculture, public health, and biodiversity conservation.

Angiostrongylus costaricensis is a zoonotic parasitic nematode described for the first time in 1971 by Pedro Morera and Rodolfo Céspedes in Costa Rica. This parasite causes an infection known as abdominal angiostrongyliasis, affecting mainly school-aged children and young adults. Infection with A. costaricensis has been associated with a myriad of rodent and mollusk species in the Americas and the Caribbean, as its natural hosts and reservoirs. In this commemorative review, we highlight the extensive research collected through a 50-year journey, which includes ecological, pathological, and molecular studies on A. costaricensis and its implicated disease. We also identify major knowledge gaps in its evolutionary history, the ecological role of imported and invasive mollusk species, and immune response. We propose that the advent of -omics analyses will allow us to gather novel information regarding A. costaricensis biology and infection dynamics, as well as to promote the design of much-needed sensitive and specific diagnostic tools., (© 2021. The Author(s).)

In life cycle of Angiostrongylus costaricensis, veronicellidae mollusks participate as the invertebrate host while rodents as the main vertebrate host. The current work shows a sequential larval development of A. costaricensis in Sarasinula marginata, individually killed and digested from day 1 to 43, post infection. Some larvae, recovered from sedimentation, were submitted to selective staining after paraffin embedded or inclusion in JB-4 to study inner structures. As control, four slugs were used, two killed at the beginning of infection and the others at the end of the experiment. At day 2 post infection, larvae were motionless and thick, presenting initial retention of granules. At day 4, L2 were detected, persisting until 43 days post infection. Larvae L2 displayed a large amount of granules rich in lipids and carbohydrates through its overall body, with more accumulation at the medial third corresponding to the esophagus-intestine transition site. Lipid granules, the main energetic source, were located at the basal and apical regions of intestinal cells. Both L1 and L3 presented bilateral alae, which is also common in other nematodes. Transition forms between L2 to L3 molts were also observed.

Angiostrongylus costaricensis intermediate hosts are terrestrial mollusks mostly belonging to the Veronicellidae family. In the present investigation we focused on the mechanisms of larval expulsion from Sarasinula marginata infected with A. costaricensis. Twenty-five mollusks were individually infected with 5000 L1 and sacrificed at 30 min and 1, 2, 4, 6, and 8 h post-infection and at days 1, 2, 4, 5, 6, 8, 10, 11, 12, 14, 15, 16, 20, 21, 22, 25, 26, 28, and 30 post-infection; the mollusks were then fixed and stained. Diverse organs involved throughout the course of the migratory routes of larvae from oral penetration on were specified and the mechanisms of larval access to the fibromuscular layer through the kidney, rectum, and vascular system were defined. The elimination of L3, derived from oral and/or cutaneous infections, appears to depend on granulomas located close to the excretory ducts of mucous cells.

Angiostrongylus costaricensis is a nematode parasite of wild rodents in the Americas. Man may become infected accidentally and, sometimes, suffers a very severe abdominal disease. Ingestion of raw vegetables has been proven to be a risk factor for the acquisition of A. costaricensis and, therefore, prophylaxis should include food disinfection. The larvicidal effect of wine vinegar, saturated cooking salt (SS) and a 1.5% bleach solution (BW) were compared with a 1-h-incubation period, at room temperature. Larval viability was tested through inoculation in Swiss mice. Only one out of 560 larvae treated with BW (97.3% of the animals were uninfected) was recovered as an adult worm, while 90/336 and 29/512 larvae treated, respectively, with SS and WV were recovered as adult worms. This larvicidal effect of BW was seen also in incubation times as short as 15 min. In conclusion, the 1.5% bleach solution may be helpful for prophylaxis of human abdominal angiostrongyliasis through disinfection of raw vegetables and unpeeled fruits.

The intermediate hosts of Angiostrongylus costaricensis are terrestrian molluscs, mostly of the family Veronicellidae. The present work aimed at clarifying more accurately the sites of penetration and the migratory routes of A. costaricensis in the tissue slugs and at verifying the pattern of the perilarval reaction at different times of infection. Slugs were individually infected with 5,000 L1, and killed from 30 min to 30 days after infection. From 30 min up to 2 hr after infection, L1 were found within the lumen of different segments of the digestive tube having their number diminished in more advanced times after exposition until complete disappearance. After 30 min of exposition, percutaneous infection occurred, simultaneously to oral infection. Perilarval reaction was observed from 2 hr of infection around larvae in fibromuscular layer, appearing later (after 6 hr) around larvae located in the viscera. A pre-granulomatous reaction was characterized by gradative concentration of amebocytes around larvae, evolving two well-organized granulomas. In this work we confirmed the simultaneous occurrence of oral and percutaneous infections. Perilarval reaction, when very well developed, defined typical granulomatous structure, including epithelioid cell transformation. The infection also caused a systemic mobilization of amebocytes and provoked amebocyte-endothelium interactions.

Human accidental infection with Angiostrongylus costaricensis may result in abdominal disease of varied severity. Slugs from the Veronicellidae family are the main intermediate hosts for this parasitic nematode of rodents. Phyllocaulis variegatus, Phyllocaulis soleiformis and Phyllocaulis boraceiensis were experimentally infected to describe the kinetics of L3 elimination in the mucus secretions of those veronicelid species. A maximum of 2 L3/g/day was found in the mucus, while the number of L3 isolated from the fibromuscular tissues varied from 14 to 448. Productive infection was established by inoculations in the hyponotum or in the body cavity, through the tegument. Intra-cavity injection is a less complex procedure and permits a better control of inocula. A preliminary trial to titrate the infective dosis for P. variegatus indicated that inocula should range between 1000 and 5000 L1. The data also confirmed the importance of P. variegatus as an intermediate host of A. costaricensis.

Angiostrongylus costaricensis is a parasitic nematode of rodents and molluscs are the intermediate hosts. Nocturnal collection of molluscs and search for infective third stage larvae of A. costaricensis was carried out in 18 endemic foci identified by the notification of a confirmed diagnosis in human biopsies or surgical specimens. Molluscs were digested in acidic solution and isolation of larvae eventually present was done in a Baermann funnel. Larvae identified by the presence of a delicate groove in the tail were counted to assess the individual parasitic burden. Four species were found infected, with ranges of prevalence in parenthesis: Phyllocaulis variegatus (7% to 33.3%); Bradybaena similaris (11.7% to 24.1%); Belocaulus angustipes (8.3%) and Phyllocaulis soleiformis (3.3% to 14.2%). Parasitic burden varied from 1 to 75 with P. variegatus, 1 to 98 with B. similaris. 1 to 13 with B. angustipes and 1 larvae in each of two specimens of P. solciformis. P. variegatus was present in all sites and was found infected with the highest prevalence figures and the highest individual parasitic burdens. These data stress the importance of veronicellid slugs as intermediate hosts for A. costaricensis in the endemic areas in Rio Grande do Sul, Brazil.

Veronicellid slugs are considered the most important intermediate hosts of Angiostrongylus costaricensis, an intra-arterial nematode of rodents. Studies undertaken in three localities in southern Brazil led to identification of molluscs other than veronicellid slugs as hosts of A. costaricensis: Limax maximus, Limax flavus and Bradybaena similaris. These data indicate a low host specificity of larval stages of A. costaricensis, as it has been reported to other congeneric species.

Specimens of Sarasinula marginata were collected in kitchen and house gardens of Belo Horizonte, Minas Gerais. The susceptibility of these molluscs for Angiostrongylus costaricensis was tested by infecting 15 laboratory--reared slugs (F1). The positivity demonstrated was of 80.0%.

A study of 94 slugs, collected from urban and rural areas in and around Léon, Nicaragua, was carried out in order to confirm the role of Vaginulus plebeius as an intermediate host of Angiostronglylus costaricensis. Third-stage larvae of A. costaricensis were obtained from these molluscs. Some of these larvae were then orally inoculated into two laboratory-bred rats Sigmodon hispidus and adult worms of A. costaricensis were recovered two months later. The infection rate of these slugs ranged from 4% in urban areas to 85% in rural areas. These data suggest that contamination to man is a major risk especially in rural areas and that abdominal angiostrongyliasis could be a health problem in Nicaragua.

Molluscs collected in five localities in the State of Rio Grande do Sul (Brazil) were digested and examined. The infected slugs were identified as Phyllocaulis variegatus and the larvae found were inoculated per os into mice. After 50 days, worms with the caracteristics of Angiostrongylus costaricensis were recovered from the mesenteric arterial system. The results establish the role of P. variegatus as intermediate host of A. costaricensis in south Brazil, where many cases of abdominal angiostrongyliasis have been diagnosed.

An experimental infection with a smaller number of Angiostrongylus cantonensis, using rats as hosts, was carried out. When the rats were infected with one and two larvae of A. cantonensis, the infection rates were 45.5% and 73.3% and recovery rates of the adult worms were 45.5% and 66.7%, respectively. In cases when more than three larvae were given to rats, all rats were found to be infected and recovery rates were around 70%, which is the same as in the case of infection with many larvae. The recovered worms were all mature and showed no important difference in their morphological measurements. It was concluded that the larvae of A. cantonensis were able to infect rats in small numbers, and completely develop into adult worms. It is suggested that human infection could occur in the same way.

Third-stage metastrongyle larvae were recovered from slugs (Vaginulus sp.) collected in Santa Lucia, Ecuador, a town about 40 miles north of Guayaquil. Some of the larvae were inoculated into laboratory-bred cotton rats and adults of Angiostrongylus costaricensis were later recovered. This is the first report of this parasite in Ecuador.

Wild rats and molluscs were examined for Angiostrongylus cantonensis infection on Viti Levu, Fiji. A. cantonensis were recovered from 29.6% (16/54) of Rattus rattus and 59.5% (25/42) of R. exulans. A. cantonensis-like larval nematodes were found in all of four slugs, Laevicaulis alte, and ten of 20 unidentified land snails. The larvae developed to adult A. cantonensis in the pulmonary arteries of laboratory rats 40 to 42 days after ingestion. This is the first record of A. cantonensis in Fiji.

The authors report the first observation, in West Africa, of eosinophilic meningitis in an ivorian child who ingested raw Achatina sp. The presence of a Parastrongylus. sp. in the cerebrospinal fluid was detected.

Angiostrongylus costaricensis, producing abdominal angiostrongyliasis, is known to occur in humans and/or rodents in the Western Hemisphere, namely in the U.S.A. (Texas), Mexico, Honduras, El Salvador, Costa Rica, Panama, Venezuela, and Brazil, Rats, Oryzomys caliginosus, in Colombia were found to harbor the parasite. First-stage larvae from one of these rats developed to third-stage larvae in the slug Veronicella occidentalis, also from Colombia.

In Costa Rica, Veronicellid slugs are the most important intermediate hosts for Angiostrongylus costaricensis. Apparently, these molluscs develop a resistant mechanism after being exposed to the infection. In naturally infected slugs, the higher infection rates were found in large slugs, but they usually bear few larvae. Large number of larvae were found in medium sized molluscs. Experimental infection in laboratory breed slugs produced an amebocytic reaction around developing larvae; later, the formation of a fibrotic capsule is observed. When there is a second infection, cell reaction is stronger and the larvae show degenerative signs. This cell-mediated resistant mechanism seems to explain why the biggest molluscs, although more probably exposed to infection, bear fewer larvae.