The increase in the reptile population has led to a rise in the number of zoonotic infections due to close contact with reptiles, with reptile-associated salmonellosis being particularly relevant. California kingsnake invasion not only threatens the endemic reptile population of the island of Gran Canaria (Spain) but also poses serious public health problems by spreading zoonotic pathogens and their antimicrobial resistance (AMR) to the environment. Thus, the aim of this study was to assess the occurrence, genetic diversity, and AMR among Salmonella spp. strains isolated from California kingsnakes in Gran Canaria Island (Spain). Of 73 invasive individuals captured, 20.5% carried Salmonella spp., belonging to different subspecies and serovars, with subsp. salamae as the most abundant. Pulsed-field electrophoresis showed high genetic diversity among subsp. salamae isolates, and among these, 73.3% showed resistance to at least one of the antimicrobials tested. In conclusion, the present study revealed the importance of wild invasive California kingsnakes as reservoirs of drug-resistant Salmonella spp. that could pose a direct threat to livestock and humans. Identification of drug-resistant Salmonella strains in wildlife provides valuable information on potential routes of transmission that involve risks to public and animal health.

The California kingsnake (Lampropeltis californiae), native to North America, is a significant threat to the conservation of endemic species in the Spanish Macaronesian island of Gran Canaria. However, its role disseminating potential invasive parasites, such as zoonotic pentastomids, has not been proven. Among its parasitic fauna, only protistans have been documented, in contrast to other Lampropeltis spp., which are known to carry pentastomids. Thus, a parasitological study is urgently required. Between 2016 and 2018, a total of 108 snakes were necropsied and stool samples examined. A single snake was infested with Ophionyssus natricis, and another individual with Serpentirhabdias sp. Only this latter snake presented gross lesions, characterized by granulomatous pneumonia. No Pentastomida were found. By contrast, almost the entire population (98.5%) was infested with larval helminths (three different nematode and two cestode species), characterized by granulomatous gastrointestinal serositis. This suggests the snake poses a ‘dead end’ host for local parasites. Based on these findings, snakes in Gran Canaria carry potential zoonotic mites, which along with Serpentirhabdias sp. could represent a threat to endemic lizards. The presence of metazoan parasites and their lesions are reported for the first time in the California kingsnake.

The influence of climate on parasite distribution has been demonstrated in different regions worldwide. Despite its small size, Gran Canaria (Canary Islands, Spain) constitutes a ‘biodiversity laboratory’ due to the huge climatic differences between municipalities. Feral cats may represent a threat to biodiversity due to their predatory behaviour. In addition, they may be a source of pathogens zoonotic to humans. To study the climatic/seasonal influence and prevalence of feral cat parasites throughout the island, a total of 290 stool samples from 29 feral cat colonies were analysed following standard concentration protocols (sodium chloride, formol-ether and zinc sulphate). In total, 13 feline parasitic taxa were found, with the most common species being Ancylostoma spp., which, together with Toxocara spp., Toxoplasma gondii and Giardia spp., are considered a concern for human health. Nematodes were the most common parasites in all areas. Nematodes and protozoans were significantly more prevalent in temperate mild (75.0% and 30.0%) than in dry desert areas (29.3% and 18.7%). In contrast, cestodes were significantly more prevalent in dry desert than in temperate mild areas (26.0% and 13.3%). Only protozoans exhibited statistically significant seasonal patterns, mostly in the wet season. Data reported in this study endorse the usage of small and diverse islands such as Gran Canaria to study the climatic influence on parasitic communities in wild/feral animals. Cat colonies require better management to reduce their threat to endemic wildlife, domestic animals and public health, being invasive species that harbour zoonotic parasites.

Invasive species pose a threat not only to biodiversity because they displace or compete with native fauna, but also because of the pathogens they can host. The Canary Islands are an Atlantic biodiversity hotspot threatened by increasing numbers of invasive species, including the California kingsnake Lampropeltis californiae, which was recently introduced to Gran Canaria. Seventy-seven snakes were examined for gastrointestinal parasites in 2019–2020. Sporocysts of Sarcocystis sp. were detected in 10 of them; detection of gamogonia stages in histological sections of 3 snakes confirmed the snake as a definitive host. Partial ssrDNA was amplified using SarcoFext/SarcoRext primers; an additional sequence of Sarcocystis was obtained from the tail muscle of the endemic Gran Canaria giant lizard Gallotia stehlini for a comparison. Identical ssrDNA sequences of unknown Sarcocystis sp. were obtained from 5 different snakes. Phylogenetic analysis showed that Sarcocystis sp. isolated from invasive California kingsnakes is unrelated to Sarcocystis provisionally considered S. stehlini from the endemic lizard. The dixenous coccidia are rarely reported to invade new predator–prey systems. However, the present data suggest that previously unknown Sarcocystis sp. is circulating among invasive snakes and as yet unknown vertebrate intermediate hosts, with undetermined consequences for the Gran Canaria ecosystem.

Within the family Adeleidae, Adelina spp. belong to a group of arthropod pathogens. These parasites have been reported to have a wide geographic distribution, however, there are no reports of these protists in the Canary Islands, Spain. One of the peculiarities of the life cycle of Adelina spp. is the participation of a predator, because fecundation and sporulation occur inside the body cavity, and so necessitate destruction of the definitive host. The involvement therefore of a ‘dispersion host’, which eats the definitive host and spreads the oocysts through its faeces, is critical for the maintenance of certain Adelina spp. On the island of Gran Canaria, adeleid oocysts have been found in stool samples from four animals, three California kingsnakes (Lampropeltis californiae), and one feral cat. These animals were part of a larger coprological study of vertebrate parasites (117 snakes, 298 cats), where pseudoparasitic elements were also recorded. L. californiae and feral cats are invasive species which are widespread across the island and this novel finding of Adelina spp. oocysts in their faeces suggests that they could also serve as potential sentinel species for arthropod parasites.

Microsporidia are a group of obligate intracellular parasites with a broad host range. These parasites can cause mild to severe harm to their hosts, making them important targets for research. However, studies on common wild-caught fish from the Atlantic Eastern Central Zone (FAO Area 34) remain scarce. 576 individuals across 35 fish species from this region were collected from local markets between 2011 and 2019. The specimens were dissected, and lesions were examined using histology, wet mounts, PCR, and transmission electron microscopy. However, microsporidian infection was detected only in round sardinella (Sardinella (S.) aurita), with 19 out of 39 individuals infected. Parasitized fish weighed nearly half as much as non-infected ones, indicating a potentially significant economic impact. Molecular and ultrastructural analyses identified the parasite as Glugea (G.) thunni, a species previously reported only from the Mediterranean Sea. This study provides the first record of G. thunni in FAO Area 34, with round sardinella likely serving as its primary host. This and other closely related sequences may represent a single taxonomic entity or, more likely, a complex of a few cryptic species geographically separated across the Mediterranean Sea and the eastern and western North Atlantic regions.