Intermediate hosts of Angiostrongylus cantonensis in Tenerife, Spain

Abstract

The nematode Angiostrongylus cantonensis is the causative agent of human angiostrongyliasis, the main clinical manifestation of which is eosinophilic meningitis. Although this parasite has been found recently in its definitive rat host in Tenerife (Canary Islands, Spain), showing a widespread distribution over the north-east part of the island, there are no available data regarding which snail and/or slug species are acting as intermediate hosts on this island. Consequently, the objective of this work was to determine the possible role of three mollusc species, Plutonia lamarckii, Cornu aspersum and Theba pisana, as intermediate hosts of A. cantonensis in Tenerife. Between 2011 and 2014, 233 molluscs were collected from five biotopes where rats had been found previously to harbor either adult worms or antibodies against A. cantonensis, and the identification was carried out on the basis of morphological features and a LAMP technique. The prevalence of A. cantonensis larvae in the mollusc samples, based on morphological identification, was 19.3%, whereas 59 out of the 98 individuals (60.2%) analyzed by LAMP were positive. Positive results were obtained for the three mollusc species analyzed and two of the positive samples, both obtained from P. lamarckii, were confirmed as positive by 18S rRNA and ITS1 PCR. Sequence analysis of 18S rRNA PCR products showed 100% similarity with previously published A. cantonensis sequences. These results may be relevant from a public health point of view, since all the biotopes from which the samples were obtained were in inhabited areas or areas with human activity, but it is also important from the perspective of a possible transmission to other accidental hosts, such as dogs and horses, animals that are present in some of the areas analyzed.

Fig 1. Geographical distribution of the sampling areas in Tenerife.

1, El Pris; 2, Pico del Inglés; 3, La Esperanza; 4, La Laguna; 5, Pedro Álvarez.

Fig 2. Mollusc species included in the study.

Theba pisana (a), Cornu aspersum (b), Plutonia lamarckii (c).

Fig 3. Detection of Angiostrongylus cantonensis by LAMP reaction.

tube 1, DNA isolated from Plutonia lamarckii tissue; tube 2, DNA obtained from A. cantonensis adult worms; tube 3, negative control.

Fig 4. Light microscopy of third stage larvae (L3) morphologically compatible with Angiostrongylus cantonensis, obtained from Theba pisana.

General view of third-stage larvae with one sheath (S). A characteristic “T”-shaped structure (TS) is apparent at the anterior end of the sheath that surrounds the L3 larva (a). Posterior end of L3 larva with anus (A) at subterminal position. Anus cuticle (AC) is completely molted and can be seen on the sheath (b). Anterior end of L3 larva with esophagus bulbus (EB), excretory pore (EP) and nervous ring (NR) (c).