Background Rats ( Rattus spp.) invaded most of the world as stowaways including some that carried the rat lungworm, Angiostrongylus cantonensis , the cause of eosinophilic meningoencephalitis in humans and other warm-blooded animals. A high genetic diversity of A. cantonensis based on short mitochondrial DNA regions is reported from Southeast Asia. However, the identity of invasive A. cantonensis is known for only a minority of countries. The affordability of next-generation sequencing for characterisation of A. cantonensis genomes should enable new insights into rat lung worm invasion and parasite identification in experimental studies. Methods Genomic DNA from morphologically verified A. cantonensis (two laboratory-maintained strains and two field isolates) was sequenced using low coverage whole genome sequencing. The complete mitochondrial genome was assembled and compared to published A. cantonensis and Angiostrongylus malaysiensis sequences. To determine if the commonly sequenced partial cox 1 can unequivocally identify A. cantonensis genetic lineages, the diversity of cox 1 was re-evaluated in the context of the publicly available cox 1 sequences and the entire mitochondrial genomes. Published experimental studies available in Web of Science were systematically reviewed to reveal published identities of A. cantonensis used in experimental studies. Results New A. cantonensis mitochondrial genomes from Sydney (Australia), Hawaii (USA), Canary Islands (Spain) and Fatu Hiva (French Polynesia), were assembled from next-generation sequencing data. Comparison of A. cantonensis mitochondrial genomes from outside of Southeast Asia showed low genetic diversity (0.02–1.03%) within a single lineage of A. cantonensis . Both cox 1 and cox 2 were considered the preferred markers for A. cantonensis haplotype identification. Systematic review revealed that unequivocal A. cantonensis identification of strains used in experimental studies is hindered by absence of their genetic and geographical identity. Conclusions Low coverage whole genome sequencing provides data enabling standardised identification of A. cantonensis laboratory strains and field isolates. The phenotype of invasive A. cantonensis , such as the capacity to establish in new territories, has a strong genetic component, as the A. cantonensis found o...

The nematode Angiostrongylus cantonensis is a zoonotic pathogen and the etiological agent of human angiostrongyliasis or rat lungworm disease. Hawai‘i, particularly east Hawai‘i Island, is the epicenter for angiostrongyliasis in the USA. Rats (Rattus spp.) are the definitive hosts while gastropods are intermediate hosts. The main objective of this study was to collect adult A. cantonensis from wild rats to isolate protein for the development of a blood-based diagnostic, in the process we evaluated the prevalence of infection in wild rats. A total of 545 wild rats were sampled from multiple sites in the South Hilo District of east Hawai‘i Island. Adult male and female A. cantonensis (3,148) were collected from the hearts and lungs of humanely euthanized Rattus rattus, and R. exulans. Photomicrography and documentation of multiple stages of this parasitic nematode in situ were recorded. A total of 45.5% (197/433) of rats inspected had lung lobe(s) (mostly upper right) which appeared granular indicating this lobe may serve as a filter for worm passage to the rest of the lung. Across Rattus spp., 72.7% (396/545) were infected with adult worms, but 93.9% (512/545) of the rats were positive for A. cantonensis infection based on presence of live adult worms, encysted adult worms, L3 larvae and/or by PCR analysis of brain tissue. In R. rattus we observed an inverse correlation with increased body mass and infection level of adult worms, and a direct correlation between body mass and encysted adult worms in the lung tissue, indicating that larger (older) rats may have developed a means of clearing infections or regulating the worm burden upon reinfection. The exceptionally high prevalence of A. cantonensis infection in Rattus spp. in east Hawai‘i Island is cause for concern and indicates the potential for human infection with this emerging zoonosis is greater than previously thought.

Leinbach, Israel L.; Klasner, Ina H.; Kaluna, Lisa M.; Snook, Kirsten A.; Howe, M. Kathleen; Jacquier, Steven H.; Lange, Ingo; Atkinson, Abigail L.; Deane, Ashley R.; Niebuhr, Chris N.; and Siers, Shane R., "Validation of a death assay for Angiostrongylus cantonensis larvae (L3) using propidium iodide in a rat model (Rattus norvegicus)" (2019). AbstractAngiostrongylus cantonensis is a pathogenic nematode and the cause of neuroangiostrongyliasis, an eosinophilic meningitis more commonly known as rat lungworm disease. Transmission is thought to be primarily due to ingestion of infective third stage larvae (L3) in gastropods, on produce, or in contaminated water. The gold standard to determine the effects of physical and chemical treatments on the infectivity of A. cantonensis L3 larvae is to infect rodents with treated L3 larvae and monitor for infection, but animal studies are laborious and expensive and also raise ethical concerns. This study demonstrates propidium iodide (PI) to be a reliable marker of parasite death and loss of infective potential without adversely affecting the development and future reproduction of live A. cantonensis larvae. PI staining allows evaluation of the efficacy of test substances in vitro, an improvement upon the use of lack of motility as an indicator of death. Some potential applications of this assay include determining the effectiveness of various anthelmintics, vegetable washes, electromagnetic radiation and other treatments intended to kill larvae in the prevention and treatment of neuroangiostrongyliasis.