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.
Neuroangiostrongyliasis, caused by Angiostrongylus cantonensis , has been reported in Hawaiʻi since the 1950's. An increase in cases is being reported primarily from East Hawaiʻi Island, correlated with the introduction of the semi-slug Parmarion martensi . Households in areas lacking infrastructure for water must use rainwater catchment as their primary domestic water supply, for which there is no federal, state, or county regulation. Despite evidence that slugs and snails can contaminate water and cause infection, regulatory bodies have not addressed this potential transmission route. This study evaluates: 1) the emergence of live, infective-stage A . cantonensis larvae from drowned, non-native, pestiforous gastropods; 2) larvae location in an undisturbed water column; 3) longevity of free-living larvae in water; and 4) effectiveness of rainwater catchment filters in blocking infective-stage larvae. Larvae were shed from minced and whole gastropods drowned in either municipal water or rainwater with ~94% of larvae recovered from the bottom of the water column 72–96 hours post drowning. Infective-stage larvae were active for 21 days in municipal water. Histological sectioning of P . martensi showed proximity of nematode larvae to the body wall of the gastropod, consistent with the potential for shedding of larvae in slime. Gastropod tissue squashes showed effectivity as a quick screening method. Live, infective-stage larvae were able to traverse rainwater catchment polypropylene sediment filters of 20 μm, 10 μm, 5 μm, and 1 μm filtration ratings, but not a 5 μm carbon block filter. These results demonstrate that live, infective-stage A . cantonensis larvae emerge from drowned snails and slugs, survive for extended periods of time in water, and may be able to enter a catchment user's household water supply. This study illustrates the need to better investigate and understand the potential role of contaminated water as a transmission route for neuroangiostrongyliasis.
The nematode Angiostrongylus cantonensis is a rat lungworm, a zoonotic pathogen that causes human eosinophilic meningitis and ocular angiostrongyliasis characteristic of rat lungworm (RLW) disease. Definitive diagnosis is made by finding and identifying A. cantonensis larvae in the cerebral spinal fluid or by using a custom immunological or molecular test. This study was conducted to determine if genomic DNA from A. cantonensis is detectable by qPCR in the blood or tissues of experimentally infected rats. F1 offspring from wild rats were subjected to experimental infection with RLW larvae isolated from slugs, then blood or tissue samples were collected over multiple time points. Blood samples were collected from 21 rats throughout the course of two trials (15 rats in Trial I, and 6 rats in Trial II). In addition to a control group, each trial had two treatment groups: the rats in the low dose (LD) group were infected by approximately 10 larvae and the rats in the high dose (HD) group were infected with approximately 50 larvae. In Trial I, parasite DNA was detected in cardiac bleed samples from five of five LD rats and five of five HD rats at six weeks post-infection (PI), and three of five LD rats and five of five HD rats from tail tissue. In Trial II, parasite DNA was detected in peripheral blood samples from one of two HD rats at 53 minutes PI, one of two LD rats at 1.5 hours PI, one of two HD rats at 18 hours PI, one of two LD rats at five weeks PI and two of two at six weeks PI, and two of two HD rats at weeks five and six PI. These data demonstrate that parasite DNA can be detected in peripheral blood at various time points throughout RLW infection in rats.
16 Neuroangiostrongyliasis, caused by Angiostrongylus cantonensis, has been reported in Hawaiʻi 17 since the 1950's. An increase in cases is being reported primarily from East Hawaiʻi Island, 18 correlated with the introduction of the semi-slug Parmarion martensi. Households in areas 19 lacking infrastructure for water must use rainwater catchment as their primary domestic water 20 supply, for which there is no federal, state, or county regulation. Despite evidence that 21 contaminated water can cause infection, regulatory bodies have not addressed this potential 22 transmission route. This study evaluates: 1) the emergence of live, infective-stage A. cantonensis 23 larvae from drowned, non-native, pestiforous gastropods; 2) larvae location in an undisturbed 24 water column; 3) longevity of free-living larvae in water; and 4) effectiveness of rainwater 25 catchment filters in blocking infective-stage larvae. Larvae were shed from minced and whole 26 gastropods drowned in either municipal water or rainwater with >94% of larvae recovered from 27 the bottom of the water column. Infective-stage larvae were active for 21 days in municipal 28 water. Histological sectioning of P. martensi showed proximity of nematode larvae to the body 29 wall of the gastropod, consistent with the potential for shedding of larvae in slime. Gastropod 2 30 tissue squashes showed effectivity as a quick screening method. Live, infective-stage larvae were 31 able to traverse rainwater catchment polypropylene sediment filters of 20 µm, 10 µm, 5 µm, and 32 1 µm filtration ratings, but not a 5 µm carbon block filter. These results demonstrate that live, 33 infective-stage A. cantonensis larvae can and do emerge from drowned snails and slugs, survive 34 for extended periods of time in water, and that the potential exists that they enter the household 35 water supply. This study illustrates the need to better investigate and understand the potential 36 role of contaminated water as a transmission route for neuroangiostrongyliasis. 37 38 Introduction 39 The nematode Angiostrongylus cantonensis is established throughout the main Hawaiian Islands 40 with the possible exception of Lānaʻi [1, 2, 3]. The complex lifecycle of this parasite has been 41 well-described in the literature [4, 5, 6, 7]. In Hawaiʻi, Rattus rattus and Rattus exulans are 42 important definitive hosts, and many gastropod species are effective intermediate hosts including 43 Achatina fulica, Euglandia rosea, Laevicaulis alte, Limax maximus, Parmarion martensi and 44 Veronicella cubensis [1, 2, 8]. The third stage larva (L3) is harbored in the intermediate host, and45 it is this larval stage that is infective to rats and accidental hosts, including humans, as the L3 46 larvae can safely pass through the acidic environment of the mammalian gut. There are also 47 paratenic hosts that can carry the infective stage larvae; these include shrimp, prawns, crabs, 48 frogs, water monitor lizards, centipedes, and some planarians [7. 9, 10, 11, 12]. Of planarians, 49 the predacious Platydemou...
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