Update on the First Finding of the Rat Lungworm, Angiostrongylus cantonensis, in Rattus spp. in Continental Europe, Valencia, Spain, 2022

Abstract

The rat lungworm, Angiostrongylus cantonensis, is an emerging parasite that can cause eosinophilic meningitis in humans. Over the past 60 years, the worm has greatly expanded its original Asian distribution to most tropical and subtropical areas of the world, mostly by traveling on ships with its definitive hosts, rats. Angiostrongylus cantonensis was recently found for the first time in Continental Europe, specifically in 3 (2 Rattus norvegicus and 1 Rattus rattus) out of 27 rats trapped in the sewer system of the city of Valencia, Spain. Updating the investigation, the parasite has subsequently been found in 8 (5 R. norvegicus and 3 R. rattus) out of 94 rats analyzed. The highest prevalence of infection (20%) was obtained in rats trapped in the orchards that surround the city, where both snails and slugs (intermediate hosts) abound, and where vegetables consumed in Valencia, other parts of Spain, and abroad, are produced. The presence of the parasite in rats does not necessarily mean that the disease it causes becomes a relevant public health concern since it strongly depends on the food habits of the population at risk. If proper precautions are taken, the risk of acquiring neuroangiostrongylosis should be minimal.

Application of the Midi Parasep® SF technique for the detection of L1 larvae of Angiostrongylus cantonensis in faeces of infected rats

“…Part of the concentrated sample, destined for DNA extraction for polymerase chain reaction testing for protozoan identification, was kept at -80 °C (Galán-Puchades et al . 2023). Another part was placed in 10% formalin for subsequent preparation of direct wet mounts that were observed under a microscope between slide and coverslip, with the aid of a drop of Lugol’s iodine, to carry out the morphological identification of protozoan cysts, helminth eggs, and larvae.

Figure 1. Midi Parasep® SF after the centrifugation process showing the layer of debris and the sediment.

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“…The trapped rats were preserved at -20 °C until parasitological study (Galán-Puchades et al 2023). After thawing, rats were dissected to remove adult helminths, and the contents of the large intestinesincluding those of the eight infected by Angiostrongylus cantonensiswere collected, filtered, and concentrated by centrifugation (2500 rpm/5 min) in Midi Parasep® SF (Figure 1 testing for protozoan identification, was kept at -80 °C (Galán-Puchades et al 2023).…”

“…As a result, among other helminth and protozoan zoonoses (unpublished data), the rat lungworm, Angiostrongylus cantonensisthe causative agent of eosinophilic meningitis in humanswas found in eight rats, i.e. five R. norvegicus and three R. rattus (Galán-Puchades et al 2023). In the adult stages, the parasites live in the pulmonary arteries of rats.…”

“…five R. norvegicus and three R. rattus (Galán-Puchades et al . 2023). In the adult stages, the parasites live in the pulmonary arteries of rats.…”

The scourge of Rat lungworm disease in Continental Europe, an emerging parasite

“…Rat lungworm disease, also known as angiostrongyliasis, is a globally emerging infectious disease [1,2] . Rat lungworm disease is increasingly recognized as an important infection in different parts of the world, especially from nonendemic to endemic areas of the world, for example, in Valencia, Spain [2,3] . Observations of rat lungworm disease beyond its historical subtropical prevalence in more temperate regions have raised some public health concerns regarding its current global distribution and increasing potential for spread due to introductions, host expansion, and climate change [4][5][6] .…”