An Overview of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae), an Emerging Cause of Human Angiostrongylosis on the Indian Subcontinent

Human angiostrongylosis is an emerging zoonosis caused by the larvae of three species of metastrongyloid nematodes of the genus Angiostrongylus, with Angiostrongylus cantonensis (Chen, 1935) being dominant across the world. Its obligatory heteroxenous life cycle includes rats as definitive hosts, mollusks as intermediate hosts, and amphibians and reptiles as paratenic hosts. In humans, the infection manifests as Angiostrongylus eosinophilic meningitis (AEM) or ocular form. Since there is no comprehensive study on the disease in the Indian subcontinent, our study aims at the growing incidence of angiostrongylosis in humans, alongside its clinical course and possible causes. A systematic literature search revealed 28 reports of 45 human cases from 1966 to 2022; eosinophilic meningitis accounted for 33 cases (75.5%), 12 cases were reported as ocular, 1 case was combined, and 1 case was unspecified. The presumed source of infection was reported in 5 cases only. Importantly, 22 AEM patients reported a history of eating raw monitor lizard (Varanus spp.) tissues in the past. As apex predators, monitor lizards accumulate high numbers of L3 responsible for acute illness in humans. For ocular cases, the source was not identified. Most cases were diagnosed based on nematode findings and clinical pathology (primarily eosinophilia in the cerebrospinal fluid). Only two cases were confirmed to be A. cantonensis, one by immunoblot and the other by q-PCR. Cases of angiostrongylosis have been reported in Delhi, Karnataka, Kerala, Maharashtra, Madhya Pradesh, Puducherry, Telangana, and West Bengal. With a population of more than 1.4 billion, India is one of the least studied areas for A. cantonensis. It is likely that many cases remain undetected/unreported. Since most cases have been reported from the state of Kerala, further research may focus on this region. Gastropods, amphibians, and reptiles are commonly consumed in India; however, typical preparation methods involve cooking, which kills the nematode larvae. In addition to studying rodent and mollusk hosts, monitor lizards can be used as effective sentinels. Sequence data are urgently needed to answer the question of the identity of Angiostrongylus-like metastrongylid nematodes isolated from all types of hosts. DNA-based diagnostic methods such as q-PCR and LAMP should be included in clinical diagnosis of suspected cases and in studies of genetic diversity and species identity of nematodes tentatively identified as A. cantonensis.

<i>PHYSELLA ACUTA </i>(DRAPARNAUD, 1805) (MOLLUSCA: GASTROPODA: PHYSIDAE) IN THE ĐANHIM RIVER BASIN (LÂM ĐỒNG PROVINCE, VIETNAM): GENETIC AND MORPHOLOGICAL IDENTIFICATION

Invasive freshwater molluscs of the genus Physella (Gastropoda: Physidae) were discovered in the basin of the Dong Nai River, Vietnam for the first time. Based on the analysis of morphological features and the nucleotide sequence of the fragment of the COI mitochondrial gene, these molluscs were identified as belonging to the species Physella acuta (Draparnaud, 1805). The paper summarizes the available information on the distribution of this species in the waterbodies of Vietnam, provides the morphological characteristics of the studied individuals, and compares them with other populations of the species found in tropic and subtropic regions. It is shown that, despite the more than twenty-year history of registration of Physella acuta in Vietnam, the species remains relatively rare in the country's waterbodies. The presence in the studied sample of individuals of different size groups suggests that, in the basin of the Dong Nai River, self-reproducing population of Physella acuta has been established.

Mass Mortality as a Way of Structuring Amazonian and Alpine Tree Populations: Evidence After Storm Vaia

By logging in the past, humans can determine current tree population structures, but fast stump decomposition makes difficult to falsify that for Amazonian Rainforests. We reconstructed land-use histories and surveyed trees ≥ 10 cm diameter at breast height on three 1-ha plots (K1, K2, and K6) in Kühbergl, South Tyrolean Alps as we did for four plots in Atacapi, Ecuador (plots A, B, C, and D). Storm Vaia (October 27 –November 1, 2018) stroke Kübergl providing dated evidence of mass tree-mortality on plot K6. We used K6 as control for comparing its pre- and post-storm population structures with the ones of four Amazonian, and three Alpine species where Vaia did not kill trees (Kolmogorov-Smirnov tests). When compared with K6’s Picea abies, the following species had size distributions similar to post-storm, but not to pre-storm situation. Amazonian: Piptocoma discolor, Vochysia bracelineae (plots B and D), Miconia decurrens (plots B and C), and Pseudobombax sp (plot C). Alpine: Larix decidua (plot K1) and Picea abies (plot K2). Storms do not occur in Atacapi, where logging is a common practice. That makes plausible that discrete events of compulsive logging during secondary succession made Amazonian population structures to look similar to K6’s P. abies. Logging is forbidden in Kühbergl, but storms are common there. Thus, the current population structures of Larix decidua (plot K1) and Picea abies (plot K2) should be legacies of storms before Vaia. Looking into tree populations’ history can impulse research for answering some basic questions of Ecology: what alters population structures, and which population structuring processes are more influential than others.

Morphological and molecular identification of the invasive freshwater snail Physa acuta (Gastropoda: Physidae) into Llanquihue Lake, Chilean Patagonia

The sewage snail Physa acuta, native to North America, is an effective invasive species around the world. In Chile, it was first reported in 2014 in the north central area of the country. So far, the species has not been recorded in southern Chile. Sampling performed in 2015 in three localities from Llanquihue Lake, Chilean Patagonia, only provided native freshwater snails. However, new collections performed in February 2018 in the same three sites were successful for physid specimens suggesting a biological invasion entailing a large southward range expansion of these snails. Here we performed morphological, microstructural and phylogenetic analyses to investigate whether the new samples belong to Physa acuta. The shell morphology, male copulatory complex and radula microstructure of the new material agree with those of the sewage snail. The molecular phylogenetic analyses using the cytochrome c oxidase subunit 1 (COI) gene confirmed morphological identification. We suggest to take prompt measures to prevent the expansion of Physa acuta in Llanquihue Lake or nearby aquatic ecosystems.