A checklist of helminth parasite fauna in anuran Amphibia (frogs) of Nagaland, Northeast India

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.

Environmental, anthropogenic, and spatial factors affecting species composition and species associations in helminth communities of water frogs (Pelophylax esculentus complex) in Latvia

We investigated factors affecting species composition and patterns of species associations in parasite communities of water frogs (Pelophylax esculentus complex), applying the distance-based redundancy analysis for component communities (assemblages harboured by host populations) and Markov random fields modelling for infracommunities (assemblages harboured by individual hosts), respectively. We asked (a) What are the relative effects of variation in environmental, land use (i.e., anthropogenic), and spatial factors on the variation in the species composition of component communities (i.e., in a locality)? and (b) What is the dominant pattern of species associations in infracommunities (in a host individual), and how do these associations vary along environmental and/or anthropogenic gradients? In component communities, the greatest portion of variation in helminth species composition was explained by the combined effects of space, anthropogenic pressure, and NDVI, with the pure effect of the spatial predictor being much stronger than the effects of the remaining predictors. In infracommunities, the probability of occurrence of some, but not all, helminth species depended on the occurrence of another species, with the numbers of negative and positive co-occurrences being equal. The strength and/or sign of associations of some species pairs were spatially stable, whereas interactions between other species pairs varied along the gradient of the amount of green vegetation, from negative to positive and vice versa. We conclude that the processes in parasite infracommunities and component communities in frogs are intertwined, with both bottom-up and top-down effects acting at different hierarchical scales.

Parasitism with Acanthocephalus Ranae in Frogs (Pelophylax Ridibundus Pallas 1771), from North-east Romania

The present study was carried out on 10 frogs, Pelophylax ridibundus (Pallas, 1771), captured near the river Bahlui, Iasi, between April and May, 2019, for the study of digestive helminths and their effect on the digestive tract. Macroscopic examination of the general cavity revealed distension of the small intestine. The sectioning of the intestinal wall revealed a variable number of parasites (1 – 12) with a whitish cylindrical body, anchored in the duodenal mucosa. The morphological study of the parasites confirmed the species as Acantocephalus ranae. The prevalence of the infection was 60 % and the average intensity was 4.83 ± 4.15. Lesions of the small intestine were characterized by catarrhal enteritis, hemorrhagic spots and ulcers on the mucosa, occlusion and obstruction of the intestinal lumen. Histologically, eosinophilic inflammatory infiltrate in the glandular crypts, mucosal and submucosal edema, fibrosis and conjunctival hyperplasia, total mucosal atrophy, were found. The infection with Acanthocephalus ranae in Pelophylax ridibundus caused severe pathological changes, conditioned by the intensity of the infection, aspects revealed for the first time in Romania.

First report of Seuratascaris numidica Seurat, 1917 (Nematoda: Ascarididae) and other helminths from amphibians of West Bengal, India

Studies on nematode parasites from anuran hosts from Eastern India, particularly West Bengal, are rare. To our knowledge, there is a report of larvae of Monhysterides sp. (a fish parasite) from cysts within the body cavity and musculature of Duttaphrynus melanostictus, Hoplobatrachus tigerinus and Euphlyctis hexadactylus as well as descriptions of Aplectana duttaphryni from D. melanostictus, Aplectana dubrajpuri from H. tigerinus, Cosmocerca microhylae from Microhyla rubra and Rhabdias bulbicauda from D. melanostictus. Here, we report mature individuals of typical anuran parasites, Diplodiscus amphichrus and Seuratascaris numidica, from H. tigerinus and larvae of Acuariidae (a bird parasite) from Fejervarya limnocharis collected in Kulti, West Bengal.