Differential effects of progesterone on social recognition and the avoidance of pathogen threat by female mice.

Although pathogen threat affects social and sexual responses across species, relatively little is known about the underlying neuroendocrine mechanisms. Progesterone has been speculated to be involved in the mediation of pathogen disgust in women, though with mixed experimental support. Here we considered the effects of acute progesterone on the disgust-like avoidance responses of female mice to pathogen threat. Estrous female mice discriminated and avoided the urinary and associated odors of males subclinically infected with the murine nematode parasite, Heligmosomoides polygyrus. These avoidance responses were not significantly affected by pre-treatment with progesterone. Likewise, brief (1 min) exposure to the odors of infected males attenuated the subsequent responses of females to the odors of the normally preferred unfamiliar males and enhanced their preferences for familiar males. Neither progesterone nor allopregnanolone, a central neurosteroid metabolite of progesterone, had any significant effects on the avoidance of unfamiliar males elicited by pre-exposure to a parasitized male. Progesterone and allopregnanolone, did, however, significantly attenuate the typical preferences of estrous females for unfamiliar uninfected males, suggestive of effects on social recognition. These findings with mice indicate that progesterone may have minimal effects on the responses to specific parasite threat and the expression of pathogen disgust but may influence more general social recognition and preferences.

Alternative pathways in Angiostrongylus cantonensis (Metastrongyloidea: Angiostrongylidae) transmission.

In order to elucidate the infection pathways of third stage larvae (L3) of Angiostrongylus cantonensis, we performed experiments to assess: (i) the shedding of L3 from two species of experimental veronicellid slugs drowned in water and the ratio of emerged larvae, (ii) the transmission of viable L3 from drowned terrestrial gastropods to aquatic snails, and (iii) the transmission of viable L3 between terrestrial snails. Molluscs were experimentally infected by first stage larvae (L1) of A. cantonensis. Significantly more L3 larvae were released from Veronicella cubensis than from Veronicella sloanei. Numerous L3 were observed in the muscular foot, and also in the connective tissue between internal organs. Experimental exposure of P. maculata to L3 of A. cantonensis liberated from other gastropod species led to their infection and the infectivity of larvae after intermediesis was demonstrated by infection of laboratory rats (Rattus norvegicus). The transmission of L3 was observed in three out of four experiment replications and L3 were retrieved from 6 out of 24 Subulina octona snails. The infected synanthropic molluscs represent a key component in the epidemiology of human infections by A. cantonensis. Escape of L3 larvae from bodies of dead snails or slugs and their ability to infect further gastropod hosts (intermediesis) represents a public health risk. Thus, control of molluscs living in peri-domestic environment is an essential part of prevention of human infections.

Angiostrongylus cantonensis in urban populations of terrestrial gastropods and rats in an impoverished region of Brazil.

The nematode Angiostrongylus cantonensis is the most common cause of neuroangiostrongyliasis (manifested as eosinophilic meningitis) in humans. Gastropod molluscs are used as intermediate hosts and rats of various species are definitive hosts of this parasite. In this study, we identified several environmental factors associated with the presence and abundance of terrestrial gastropods in an impoverished urban region in Brazil. We also found that body condition, age and presence of co-infection with other parasite species in urban Rattus norvegicus, as well as environmental factors were associated with the probability and intensity of A. cantonensis infection. The study area was also found to have a moderate prevalence of the nematode in rodents (33% of 168 individuals). Eight species of molluscs (577 individuals) were identified, four of which were positive for A. cantonensis. Our study indicates that the environmental conditions of poor urban areas (presence of running and standing water, sewage, humidity and accumulated rain and accumulation of construction materials) influenced both the distribution and abundance of terrestrial gastropods, as well as infected rats, contributing to the maintenance of the A. cantonensis transmission cycle in the area. Besides neuroangiostrongyliasis, the presence of these hosts may also contribute to susceptibility to other zoonoses.

Gastrointestinal helminth parasites of the common wallaroo or euro, Osphranter robustus (Gould) (Marsupialia: Macropodidae) from Australia.

The gastrointestinal helminth parasites of 170 common wallaroos or euros, Osphranter robustus (Gould), collected from all mainland states in which the species occurs as well as the Northern Territory, are presented, including previously published data. A total of 65 species of helminths were encountered, including four species of anoplocephalid cestodes found in the bile ducts and small intestine, and 61 species of strongylid nematodes, all but two of which occurring in the stomach, and with the remainder occurring in the terminal ileum, caecum and colon. Among the mainland subspecies of O. robustus, 52 species of helminths were encountered in O. r. robustus, compared with 30 species in O. r. woodwardi and 35 species in O. r. erubescens. Of the parasite species encountered, only 17 were specific to O. robustus, the remaining being shared with sympatric host species. Host-specific species or species occurring in O. robustus at a high prevalence can be classified as follows: widely distributed; restricted to northern Australia; restricted to the northern wallaroo, O. r. woodwardi; found only in the euro, O. r. erubescens; found essentially along the eastern coast of Australia, primarily in O. r. robustus; and species with highly limited regional distributions. The data currently available suggest that the acquisition of a significant number of parasites is due to co-grazing with other macropodids, while subspeciation in wallaroos as well as climatic variables may have influenced the diversification of the parasite fauna.

Invasive slug Meghimatium pictum (Stoliczka, 1873) infected by Angiostrongylus costaricensis Morera & Céspedes, 1971, and the possible risk of human infection associated with grape consumption.

Many molluscs may be infected with angiostrongylid larvae. Following the histopathological diagnosis of abdominal angiostrongyliasis in a grape farmer from southern Brazil, molluscs in the area were investigated. During a nocturnal search, 245 specimens of slugs were collected and identified as the invasive Chinese slug Meghimatium pictum. Angiostrongylus costaricensis worms were recovered from mice that were experimentally infected with larvae obtained from 11 (4.5%) of the molluscs. This study presents the first report of M. pictum being identified as an intermediate host for A. costaricensis. Most of the slugs were collected from grape plants, which suggests that transmission may be associated with grape consumption.

First record of Halocercus sp. (Pseudaliidae) lungworm infections in two stranded neonatal orcas (Orcinus orca).

Orca (Orcinus orca) strandings are rare and post-mortem examinations on fresh individuals are scarce. Thus, little is known about their parasitological fauna, prevalence of infections, associated pathology and the impact on their health. During post-mortem examinations of two male neonatal orcas stranded in Germany and Norway, lungworm infections were found within the bronchi of both individuals. The nematodes were identified as Halocercus sp. (Pseudaliidae), which have been described in the respiratory tract of multiple odontocete species, but not yet in orcas. The life cycle and transmission pathways of some pseudaliid nematodes are incompletely understood. Lungworm infections in neonatal cetaceans are an unusual finding and thus seem to be an indicator for direct mother-to-calf transmission (transplacental or transmammary) of Halocercus sp. nematodes in orcas.

Angiostrongylus cantonensis DNA in Cerebrospinal Fluid of Persons with Eosinophilic Meningitis, Laos.

Definitive identification of Angiostrongylus cantonensis parasites from clinical specimens is difficult. As a result, regional epidemiology and burden are poorly characterized. To ascertain presence of this parasite in patients in Laos with eosinophilic meningitis, we performed quantitative PCRs on 36 cerebrospinal fluid samples; 4 positive samples confirmed the parasite's presence.

Angiostrongylus cantonensis Eosinophilic Meningitis in an Infant, Tennessee, USA.

Angiostrongylus cantonensis, the rat lungworm, is the most common infectious cause of eosinophilic meningoencephalitis worldwide. This parasite is endemic to Southeast Asia and the Pacific Islands, and its global distribution is increasing. We report A. cantonensis meningoencephalitis in a 12-month-old boy in Tennessee, USA, who had not traveled outside of southwestern Tennessee or northwestern Mississippi.

The cockroach Periplaneta americana as a potential paratenic host of the lungworm Aelurostrongylus abstrusus.

INTRODUCTION: Aelurostrongylus abstrusus is a well-known nematode affecting the respiratory system of felids worldwide. Snails and slugs act as intermediate hosts of this parasite, whereas rodents, birds and reptiles may serve as paratenic hosts. Periplaneta americana, the American brown cockroach, shares the same habitat and ecological features (e.g. nocturnal activity) with both snails and cats. The aim of this study was to evaluate the capability of P. americana to maintain alive A. abstrusus third stage larvae (L3s) after artificial inoculation. MATERIAL AND METHODS: Twenty-five specimens of P. americana were infected with 100 A. abstrusus L3s collected from experimentally infected Cornu aspersum snails, whereas five specimens were used as control group. After the infection, cockroaches were maintained in individual plastic boxes until dissection for the presence of L3s at 1 (T1), 5 (T5), 10 (T10), 15 (T15), and 20 (T20) days post-infection. RESULTS: Except for T15, alive A. abstrusus L3s (n = 63) were found at all time-points, being 26, 19, 16 and 2 L3s retrieved at T1, T5, T10 and T20, respectively. Eleven (17.4%) L3s were found within the digestive tract, 10 (15.9%) in other-than-digestive organs and 42 (66.7%) in the exoskeleton and associated tissues. Nine out of the twenty-five experimentally inoculated cockroaches (36%) died soon after the artificial infection (T1), while in the control group, two out of the five (40%) died before the end of the study (T15) with no difference in the mortality rate between groups. DISCUSSION: Results of this study suggest that P. americana could act as a paratenic host of A. abstrusus. Periplaneta americana cockroaches, have a ubiquitous distribution and may be preyed by cats, representing a potential source of infection to cats living in endemic areas.

Infection levels of protostrongylid nematodes in definitive caprine and intermediate gastropod hosts from Uzbekistan.

Morphological analysis of lungworms collected among Caprinae from Uzbekistan resulted in the identification of four species of Protostrongylidae: Protostrongylus rufescens, Protostrongylus hobmaieri, Spiculocaulus leuckarti and Cystocaulus ocreatus. The following species were recorded as definitive hosts: Ovis aries, Ovis ammon, Ovis vignei, Capra hircus, Capra falconeri and Capra sibirica. The prevalence of P. rufescens reached 45.3%, followed by S. leuckarti and C. ocreatus with 31.7% and P. hobmaieri with 16.9%. The sex ratio ranged between 1:3.1 and 1:6.2, with P. hobmaieri showing the strongest predominance of females over males. The prevalence of infection of small ruminants with protostrongylid nematodes increased with the age of the hosts. Protostrongyles use terrestrial gastropods as intermediate hosts, and infective larvae were found in the species Vallonia costata, Gibbulinopsis signata, Pupilla muscorum, Pseudonapaeus albiplicata, Pseudonapaeus sogdiana, Leucozonella ferghanica, Xeropicta candacharica, Candaharia levanderi and Macrochlamys sogdiana. Xeropicta candacharica was the most abundant gastropod and had the highest prevalence of infection with protostrongylids. Adult X. candacharica had a significantly higher infection intensity than juveniles. The epidemiology of protostrongylid infections is dynamic and subject to considerable changes. Further characterization of the interaction of protostrongylid parasites with their terrestrial gastropods as intermediate hosts and Caprinae as definitive hosts is required to understand these processes and to monitor the effects of changing ecological contexts.

An epidemiological study of A. cantonensis in Jamaica subsequent to an outbreak of human cases of eosinophilic meningitis in 2000.

The infection status of angiostrongylosis in Jamaica was assessed in wild rats and molluscs in the 5 years following the major outbreak of eosinophilic meningitis (EM) in 2000. Parasitological analyses of 297 Rattus rattus and 140 Rattus norvegicus, and 777 terrestrial molluscs from all 14 Parishes on the island revealed Angiostrongylus cantonensis in 32·0% of the rats and in 12·5% of the molluscs. Multivariate analyses confirmed that A. cantonensis occurred significantly more frequently in R. rattus (Odds Ratio [OR] = 1·76), while mean infection intensity in R. rattus was also significantly higher (16·8) than R. norvegicus (11·3) (Mann-Whitney U-test: P = 0·01). Third-stage larvae of A. cantonensis were detected in 29% of 86 Pleurodonte spp.; in 20% of five Poteria spp.; in 18·7% of 369 Thelidomus asper; in 11% of 18 Sagda spp.; and in 6% of 24 veronicellid slugs. Most rodent infections occurred in Northeastern Jamaica (OR = 11·66), a region where infected molluscs were also abundant. Given the prevalence of A. cantonensis infection in rats has significantly increased since the 2000 outbreak, and that a survey of human infections revealed at least ten autochthonous cases in the last 15 years, angiostrongylosis persists as an important zoonosis in Jamaica.

Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming: Nematodirus battus in lambs as a case study.

Mismatch in the phenology of trophically linked species as a result of climate warming has been shown to have far-reaching effects on animal communities, but implications for disease have so far received limited attention. This paper presents evidence suggestive of phenological asynchrony in a host-parasite system arising from climate change, with impacts on transmission. Diagnostic laboratory data on outbreaks of infection with the pathogenic nematode Nematodirus battus in sheep flocks in the UK were used to validate region-specific models of the effect of spring temperature on parasite transmission. The hatching of parasite eggs to produce infective larvae is driven by temperature, while the availability of susceptible hosts depends on lambing date, which is relatively insensitive to inter-annual variation in spring temperature. In southern areas and in warmer years, earlier emergence of infective larvae in spring was predicted, with decline through mortality before peak availability of susceptible lambs. Data confirmed model predictions, with fewer outbreaks recorded in those years and regions. Overlap between larval peaks and lamb availability was not reduced in northern areas, which experienced no decreases in the number of reported outbreaks. Results suggest that phenological asynchrony arising from climate warming may affect parasite transmission, with non-linear but predictable impacts on disease burden. Improved understanding of complex responses of host-parasite systems to climate change can contribute to effective adaptation of parasite control strategies.

Angiostrongylus cantonensis infection in molluscs in the municipality of São Gonçalo, a metropolitan area of Rio de Janeiro, Brazil: role of the invasive species Achatina fulica in parasite transmission dynamics.

The aim of this study was to analyse the infection dynamics of Angiostrongylus cantonensisin its possible intermediate hosts over two years in an urban area in the state of Rio de Janeiro where the presence ofA. cantonensis had been previously recorded in molluscs. Four of the seven mollusc species found in the study were exotic.Bradybaena similaris was the most abundant, followed by Achatina fulica, Streptaxis sp., Subulina octona, Bulimulus tenuissimus, Sarasinula linguaeformis and Leptinaria unilamellata. Only A. fulica and B. similaris were parasitised by A. cantonensis and both presented co-infection with other helminths. The prevalence of A. cantonensis in A. fulica was more than 50% throughout the study. There was an inverse correlation between the population size ofA. fulica and the prevalence of A. cantonensis and abundance of the latter was negatively related to rainfall. The overall prevalence of A. cantonensis in B. similaris was 24.6%. A. fulica was the most important intermediary host of A. cantonensis in the studied area and B. similaris was secondary in importance for A. cantonensis transmission dynamics.

[Experimental study on the artificial infection of common freshwater snails with Angiostrongylus cantonensis in Dali Bai Autonomous Prefecture, Yunnan Province].

OBJECTIVE: To evaluate the potential risk of transmission of angiostrongyliasis by common freshwater snails in Dali Bai Autonomous Prefecture, Yunnan Province, so as to provide insights into local surveillance of angiostrongyliasis. METHODS: Common freshwater snails were collected from Dali Bai Autonomous Prefecture, Yunnan Province from March to April, 2020, and identified and bred in laboratory. SD rats were infected with third-stage larvae of Angiostrongylus cantonensis that were isolated from commercially available Pomacea canaliculata snails in Dali Bai Autonomous Prefecture, and freshwater snails were infected with the first-stage larvae of A. cantonensis that were isolated from the feces of SD rats 39 days post-infection at room temperature. The developmental process and morphological characteristics of worms in hosts were observed, and the percentages of A. cantonensis infections in different species of freshwater snails were calculated. Then, SD rats were infected with the third-stage larvae of A. cantonensis that were isolated from A. cantonensis-infected freshwater snails, and the larval development and reproduction was observed. RESULTS: More than 3 000 freshwater snail samples were collected from farmlands, ditches and wetlands around Erhai Lake in Dali Bai Autonomous Prefecture, and Cipangopaludina chinensis, P. canaliculata, Parafossarulus striatulus, Oncomelania hupensis robertsoni, Galba pervia, Physa acuta, Radix swinhoei, Assiminea spp., Tricula spp. and Bellamya spp. were morphologically identified. A total of 105 commercially available P. canaliculata snails were tested for A. cantonensis infections, and 2 P. canaliculata snails were found to be infected with A. cantonensis, in which the third-stage larvae of A. cantonensis were isolated. Ten species of freshwater snails were artificially infected with the third-stage larvae of A. cantonensis, and all 10 species of freshwater snails were found to be infected with A. cantonensis, with the highest positive rate of A. cantonensis infections in Bellamya spp. (62.3%, 137/204), and the lowest in C. chinensis (35.5%, 11/31). After SD rats were infected with the third-stage larvae of A. cantonensis isolated from different species of freshwater snails, mature adult worms of A. cantonensis were yielded. CONCLUSIONS: Multiple species of freshwater snails may serve as intermediate hosts of A. cantonensis under laboratory conditions in Dali Bai Autonomous Prefecture of Yunnan Province. Further investigations on natural infection of A. cantonensis in wild snails in Dali Bai Autonomous Prefecture seem justified.

Evidence for direct transmission of the cat lungworm Troglostrongylus brevior (Strongylida: Crenosomatidae).

Metastrongyloids of cats are emerging pathogens that may cause fatal broncho-pulmonary disease. Infestation of definitive hosts occurs after ingestion of intermediate or paratenic hosts. Among metastrongyloids of cats, Troglostrongylus brevior and Troglostrongylus subcrenatus (Strongylida: Crenosomatidae) have recently been described as agents of severe broncho-pulmonary disease. Here, we provide, for the first time, observational evidence suggesting the direct transmission of T. brevior from queen cat to suckling kittens. This new knowledge will have a significant impact on current scientific information of this parasite and shed new light into the biology and epidemiology of metastrongyloid nematodes.

Larval development of the feline lungworm Aelurostrongylus abstrusus in Helix aspersa.

The cat lungworm Aelurostrongylus abstrusus affects the domestic cat and other felids all over the world. Feline aelurostrongylosis is of importance in clinical feline medicine and is gaining more and more attention for the present expansion in the geographical range of A. abstrusus. Global warming and changes in phenology of snail intermediate hosts have been incriminated in this spreading. Helix aspersa, a potential vector of A. abstrusus, is endemic in most regions of the world, where it has become recently a pest outside its native Mediterranean range. The present work evaluated key features of larval development of A. abstrusus in H. aspersa at two different temperature conditions. The results showed that A. abstrusus may reach the infective stage in muscular foot and viscera of H. aspersa and that environmental temperatures may influence the biological cycle of the cat lungworm. In particular, the higher the average temperature, the higher the rate of larval development, i.e., about 50% of larvae of A. abstrusus reached the infective stage between temperatures of 18.8-29.5 °C, while only 17.8% of larvae completed their development at temperatures of 6.7-22 °C. Biological and epidemiological implications are discussed.

Synergistic effects of seasonal rainfall, parasites and demography on fluctuations in springbok body condition.

1. Seasonality of rainfall can exert a strong influence on animal condition and on host-parasite interactions. The body condition of ruminants fluctuates seasonally in response to changes in energy requirements, foraging patterns and resource availability, and seasonal variation in parasite infections may further alter ruminant body condition. 2. This study disentangles the effects of rainfall and gastrointestinal parasite infections on springbok (Antidorcas marsupialis) body condition and determines how these factors vary among demographic groups. 3. Using data from four years and three study areas, we investigated (i) the influence of rainfall variation, demographic factors and parasite interactions on parasite prevalence or infection intensity, (ii) whether parasitism or rainfall is a more important predictor of springbok body condition and (iii) how parasitism and condition vary among study areas along a rainfall gradient. 4. We found that increased parasite intensity is associated with reduced body condition only for adult females. For all other demographic groups, body condition was significantly related to prior rainfall and not to parasitism. Rainfall lagged by two months had a positive effect on body condition. 5. Adult females showed evidence of a 'periparturient rise' in parasite intensity and had higher parasite intensity and lower body condition than adult males after parturition and during early lactation. After juveniles were weaned, adult females had lower parasite intensity than adult males. Sex differences in parasitism and condition may be due to differences between adult females and males in the seasonal timing of reproductive effort and its effects on host immunity, as well as documented sex differences in vulnerability to predation. 6. Our results highlight that parasites and the environment can synergistically affect host populations, but that these interactions might be masked by their interwoven relationships, their differential impacts on demographic groups, and the different time-scales at which they operate.

A case report on eosinophilic meningitis caused by Angiostrongylus cantonensis.

Angiostrongylus cantonensis is the most common cause of eosinophilic meningitis in humans. It is usually caused by ingestion of raw or inadequately cooked intermediate hosts or food contaminated with infective third-stage larvae. We describe a case of eosinophilic meningitis caused by A. cantonensis in a male Chinese patient. The patient had a history of eating raw fish and snail. We describe the clinical features of the patient, the diagnostic process and treatments. We also provide a brief update for physicians on the characteristics, diagnosis and treatment of eosinophilic meningitis caused by A. cantonensis, with particular emphasis on the update of prevalence and treatment of the disease in China.