Effects of snail size and diet on encystment of Echinostoma caproni cercariae in juvenile Helisoma trivolvis (Colorado strain) and observations on survival of infected snails

The effects of snail size and diet on encystment of Echinostoma caproni cercariae in juvenile Helisoma trivolvis (Colorado strain) snails were studied. Encystment in neonatal (<1-mm shell diameter) and juvenile (2- to 3-mm shell diameter) snails was compared 24 hr postinfection (PI) after individual exposure of snails of each size to 1, 5, 10, 25, or 50 cercariae. Significantly more cysts were recovered from juvenile snails exposed to 10, 25, or 50 cercariae than from neonatals with comparable exposure. The maximum number of cysts recovered from juveniles exposed to 50 cercariae was 42, compared with a maximum of 15 cysts in neonatals comparably exposed. Size of H. trivolvis was a major factor in determining cyst burden in this planorbid. A diet of either Romaine lettuce leaf or hen's egg yolk did not have a significant effect on the number of cysts recovered at 24 hr PI from juvenile snails exposed to 25 or 75 cercariae. Survival of infected versus uninfected neonatals was also examined for 7 days. Neonatals exposed to 10 cercariae showed a significant decrease in survival at 6 and 7 days PI when compared with uninfected controls.     

Toxigenic fungi isolated from cereal and legume products

Summary An investigation of the toxigenicity of moulds recovered from domestic cereal and legume crops is described. Two hundred and twenty-eight mould strains, representing 59 species, were tested by feeding Pekin ducklings on maize meal infected with pure cultures. Forty-six strains, representing 22 species, caused death within 14 days. These 22 species were subsequently fed to weaned white mice and rats. Seven of these species caused death within 14 days, 6 showed less severe toxic effects while the remaining 9 gave no signs of acute poisoning in the animals.     

Description of the life-cycle stages of Brachylaima cribbi n. sp. (Digenea: Brachylaimidae) derived from eggs recovered from human faeces in Australia

The life-cycle of Brachylaima cribbi n. sp. was established in the laboratory. Asymmetrical brachylaimid eggs, measuring 26-32 microm (29.1 microm) long and 16 -17.5 microm (16.6 microm) wide, were recovered from human faeces and fed to the helicid land snail Theba pisana as the first intermediate host. Sporocysts and cercariae were recovered from the T. pisana eight weeks after infection. The cercariae were used to infect the helicid land snails Cernuella virgata and Helix aspersa as second intermediate hosts. Metacercariae were recovered from the kidneys of these snails and used to infect mice. Adults of Brachylaima cribbi n. sp. were recovered from the small intestine of the mice. The differential features of B. cribbi n. sp. are the specificity for helicid snails as first and second intermediate hosts; characteristic ventral sucker and body cercarial chaetotaxy; and a long slender adult worm with equal size suckers in the first quarter of the worm, the ventral sucker occupying 41% of the body width, the uterus extending anterior to the ventral sucker and the vitelline follicles falling short of the posterior margin of the ventral sucker. No other known Brachylaima species exhibits all of these features. B. cribbi n. sp. is the first brachylaimid known to have infected humans and is probably of European origin, as the intermediate host snails were all introduced into Australia from Europe.     

Morphological study of muscular tissue collagen of wild and reared Cornu aspersum (Müller, 1774)

Muscular tissue collagen fibrils’ diameter and period of reared and wild snails (Cornu aspersum) were measured in order to investigate the role of nutrition on the collagen. Wild adult individuals were collected from Crete (Greece) and compared with adult individual snails reared under laboratory conditions fed a formulated diet. Transmission electron microscope and image analysis algorithms were used in the study. Statistically significant differences between the diameters of the collagen fibrils in the reared and the wild snails were found, and the D-period of the fibrils differed.     

Failure of Echinostoma lindoense to reinfect snails already harboring that species.

In Biomphalaria glabrata snails already harboring Echinostoma lindoense, attempts at reinfection with the same trematode species failed when the interval between exposures was 6 days or more. With 2 days between exposures, the experimental snails were as susceptible to reinfection as the control snails. Between these limits, the reinfection failure rate increased with the exposure interval. Failure to reinfect the snails was probably due to cannibalism, young sporocysts from the second infection being swallowed by predatory rediae from the first infection. Development of sporocysts in successfully reinfected snails was normal.     

Cercarial shedding of Echinostoma cinetorchis and experimental infection of the cercariae to several kinds of snails

The development of Echinostoma cinetorchis in several snail species reared in laboratory aquaria was observed. The eggs from adult flukes collected from the intestine of rats were cultivated to miracidia, and exposed to Hippeutis sp. snails. Observations were made for cercarial shedding from the exposed snails. The cercariae shed from the snails were again exposed to several species of fresh water snails in order to observe metacercarial formation in the snails and their infectivity to final hosts. The results obtained in this study were as follows: 1. Twenty miracidia were exposed to each snail of Hippeutis sp. About 58.3% of the above snails (7 out of 12) were dead before shedding the cercariae, and the remainder shed the cercariae for a period of 7 to 9 days before death. 2. Cercarial shedding from the infected snails started from the 25th day after the exposure to miracidia, and the total number of cercariae shed per snail was 684 in average (range; 482-904). 3. The size of rediae developed in the infected Hippeutis sp. snails was 1,242 x 214 microns in average, and the number of rediae per snail was 350 in average (range; 120-510). 4. About 40 to 50 cercariae shed from the Hippeutis sp. snails were each exposed to several species of snails reared in the laboratory. The metacercarial formation was confirmed by dissecting the infected snails, 12 to 16 days after the infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Storage and incubation of Echinostoma revolutum eggs recovered from wild Branta canadensis, and their infectivity to Lymnaea tomentosa snails

Echinostoma revolutum eggs recovered from naturally infected wild Canada geese (Branta canadensis) were cold stored (4-6 degrees C) for up to 72 weeks. Successful hatching followed incubation for from 6 to 8 days at an optimum temperature of between 25 and 30 degrees C. A partial life cycle from adult worm to metacercarial encystment in Lymnaea tomentosa snails was completed in the laboratory. Snails were infected both by free miracidia and by ingestment of unhatched embryonated eggs. Infection was equally successful in environmental temperature ranges from 10 to 25 degrees C, and at challenge levels of 2, 5 or 10 embryonated eggs per snail. Exposure to 10 eggs was lethal. Ingestion by snails of embryonated eggs with successful infection at 10 degrees C suggests that embryonated eggs may be used to infect wild snails when the environmental water temperature has reached 10 degrees C.     

Metacercariae of Pharyngostomum cordatum found from the European grass snake, Rhabdophis tigrina, and its experimental infection to cats

The metacercariae of Pharyngostomum cordatum were found naturally infected in the European grass snake, Rhabdophis tigrina, purchased from a local snake collector in Jinju, Kyongsangnam-do. They were experimentally fed to several kinds of animals such as mice, rats, hamsters, ducklings, a dog, and cats. The adult worms were recovered from the cats 5 weeks after the infection, but none from other animals. The measurements and other morphological characters of the metacercariae and adults were both compatible with those of P. cordatum described by previous authors. The present study confirmed that the snake, Rhabdophis tigrina, serves as a second intermediate (or paratenic) host of P. cordatum in Korea.     

Cipangopaludina chinensis malleata (Gastropoda: Viviparidae): a new second molluscan intermediate host of a human intestinal fluke Echinostoma cinetorchis (Trematoda: Echinostomatidae) in Korea

Two species of the viviparid snails have been reported in Korea, e.g., Cipangopaludina chinensis malleata and Cipangopaludina japonica. Cipangopaludina chinensis malleata collected at 3 of 12 localities were found to be infected with metacercariae of Echinostoma cinetorchis, one of the snail-borne human intestinal trematodes in Korea. Metacercariae from these snails were fed to rats (S/D strain), and adult worms of E. cinetorchis, characterized by 37-38 collar spines on the head crown, were recovered from the ileocecal regions. However, no C. japonica collected from 2 localities harbored the metacercariae. In experiments with laboratory-bred viviparid snails, all viviparids were not susceptible to miracidia of E. cinetorchis. To confirm the identity of second intermediate hosts of E. cinetorchis experimentally, 2 species of viviparid snails were exposed to the cercariae from Segmentina hemisphaerula that had been infected with miracidia of E. cinetorchis. Both species of snails were susceptible to cercariae of E. cinetorchis. This is the first report of Cipangopaludina spp. serving as the second intermediate host of E. cinetorchis and as a potential source of human infection.     

Second intermediate host land snails and definitive host animals of Brachylaima cribbi in southern Australia

This study of infection of southern Australian land snails with Brachylaima cribbi metacercariae has shown that all commonly encountered native and introduced snails are susceptible second intermediate hosts. The range of infected snails is extensive with metacercariae-infected snails being present in all districts across southern Australia. C. virgata has the highest average natural metacercarial infection intensity of 6.1 metacercariae per infected snail. The susceptibility of birds, mammals and reptiles to B. cribbi infection was studied in South Australia by capturing, dissecting and examining the intestinal tract contents of animals which commonly eat land snails as a food source. Indigenous Australian little ravens (Corvus mellori), which are a common scavenger bird, and two other passeriform birds, the black bird (Turdus merula) and the starling (Sturnus vulgaris), which are both introduced European birds, were found to have the highest infection rates of all animals examined. Other birds found infected with B. cribbi were an emu (Dromaius novaehollandiae), chickens (Gallus gallus) and a pigeon (Columba livia). Natural infections were also detected in field mice (Mus domesticus) and shingleback lizards (Tiliqua rugosa) although the intensity of infection was lower than that observed in birds. Susceptibility studies of laboratory mice, rats and ducks showed that mice developed patent infections which persisted for several weeks, rats developed a short-lived infection of three weeks' duration and ducks did not support infection. This study has shown for the first time that a brachylaimid can infect a wide host range of birds, mammals and reptiles in nature.     

The importance of learning young: the use of nesting material in laboratory rats

Unlike mice, adult laboratory rats do not spontaneously build nests when nesting material is offered. As a result, nesting material is often regarded as unsuitable environmental enrichment for laboratory rats. Wild rats and pet rats, however, have been observed to build complex nests from nesting material at hand. It was hypothesized that nest building in rats is an acquired behaviour, rather than genetically predisposed. To test this hypothesis, the progeny of three Wistar rats provided with nesting material (Kleenex tissues) during pregnancy and three standard-housed rats were divided in 34 same-sex couples with access to nesting material: (1) from the age of 8 weeks (n=7); (2) from weaning (n=8); (3) from birth (n=17). The latter were subdivided into two groups after weaning, one provided with Kleenex tissues (n=9), the other with Enviro-dri (n=8). At the age of 12 weeks, all couples were provided with both types of nesting material for one week. Amount, shape, and soiling of the nesting material were scored on weekdays, and behaviour of the rats was scored twice weekly. Results indicated that the older the rats were when first provided with nesting material, the greater the amount of nesting material eaten and soiled, and the nests built were less elaborate. Overall, Enviro-dri was eaten less than Kleenex tissues. It is concluded that rats need to learn the proper use of nesting material. When provided from birth, nesting material is a suitable type of environmental enrichment for laboratory rats.     

Experimental infection of Physa heterostropha, Helisoma trivolvis, and Biomphalaria glabrata (Gastropoda) with Echinostoma revolutum (Trematoda) Cercariae

Gross and histologic studies were done on laboratory-raised Physa heterostropha, Helisoma trivolvis, and Biomphalaria glabrata snails exposed individually to 100 cercariae of Echinostoma revolutum. Cercariae showed a predisposition for the kidneys of snails. They entered the nephridiopore, migrated up the tubular kidney, and encysted in the saccular kidney within 2 hr. Considerably more cysts were in the kidney of B. glabrata at 24 hr than in H. trivolvis or P. heterostropha kidneys. Encysted metacercariae were not infective to domestic chicks at 2 hr, but were infective by 4 hr. Biomphalaria glabrata exposed to about 1,000 cercariae/snail and necropsied either 10 or 16 wk postexposure contained 300-500 cysts/kidney; about one-half the cysts were viable and infective to chicks. Biomphalaria glabrata is an excellent second intermediate host for the laboratory propagation of E. revolutum.     

Effects of snail size and age on the prevalence and intensity of avian schistosome infection: relating laboratory to field studies

Both the prevalence and intensity of patent infection by avian schistosomes (Trichobilharzia ocellata) increase with increasing size of lymnaeid snails (Stagnicola elrodi) collected in Flathead Lake, Montana. Because the size and age of a snail are positively correlated, snails of different sizes may have experienced differential duration of exposure to and development of infection. Another possibility is that infection itself induces snail gigantism. Each of these possibilities could lead to increased prevalence and intensity of infection among the oldest-largest snails. To decouple size variation from many correlated effects of age and to test for parasite-induced gigantism, laboratory experiments standardized snail size-age-at-infection, exposure history, inoculating dose, and duration of infection. The positive relationship between size and prevalence was eliminated in the laboratory, but the relationship between size and infection intensity remained. Laboratory results thus suggest that infection intensity is related to snail size per se, whereas prevalence in the field is related to snail size only through the correlation between size and age. In addition, under these experimental conditions, infected snails were no larger than uninfected snails, so the patterns observed in the field might not be attributable to gigantism.     

Identification of an avian schistosome recovered from Aythya novaeseelandia and infectivity of its miracidia to Lymnaea tomentosa snails

A partial life cycle involving miracidia hatched from the eggs of Trichobilharzia sp. recovered from New Zealand scaup (Aythya novaeseelandia) to the release of furcocercariae by laboratory snails (Lymnaea tomentosa) was accomplished. Challenges with five and ten miracidia per snail were lethal. Challenge with three miracidia resulted in development to the daughter sporocyst stage and death in five, development to furcocercarial stage and death in one, and shedding of furcocercariae in one of seven snails. Observed lethality of schistosome miracidia to L. tomentosa may explain the low infection prevalence observed in the wild. Future work should plan challenge exposures of three or fewer miracidia to ensure snail survival and successful recovery of furcocercariae. The Trichobilharzia sp. found in the New Zealand scaup does not key morphologically to the literature. It may be a new species and further work is needed.     

Nematode cysts and larvae found in Achatina fulica Bowdich, 1822

This study describes the morphology of the nematode cysts and larvae found in Achatina fulica (giant African snail) in Brazil. Sixty snails were collected in Mesquita, Rio de Janeiro State. Fourteen of the snails were naturally infected. The cysts were spherical, pink colored and measured 0.97 to 1.57 mm in diameter. In the majority of cases they had a single larvae involved in amorphous material. A total of 222 encysted larvae were recovered. Of these, 30 were utilized in the morphological study. The length of the larvae varied from 2.57 to 5.8 mm and they were classified as small - up to 3.5 mm; medium - from 3.53 to 4.5 mm; and large - greater than 4.52 mm. The average length of the larvae in the three groups was 2.85, 3.87 and 5.23 mm, respectively. The larval cuticle was white, shiny and transversally striated until the posterior end of the body. At the anterior end there is a mouth with three lips, with amphids and papillae, followed by a muscular esophagus with average length of 0.61 mm, terminating in an esophageal bulb and having a nerve ring in the middle third of the esophagus, and an intestine with an opening near the posterior end. The tail begins from this opening and has two types of ends: short and abrupt or long and gradually tapering. The difference in the tail end can suggest sexual dimorphism, although no primordial reproductive structures were observed. These characteristics were not sufficient to identify the larvae, so there is a need for further study.     

Survival of Heterodera zeae in Soil in the Field and in the Laboratory

Eggs and (or) second-stage juveniles (J2) inside cysts of Heterodera zeae survived over winter in the field with no detectable mortality at all six depths to 30 cm from which soil samples were collected between corn stubble in the row at 4-8-week intervals. Few or no free J2 were recovered from soil collected in January-April from the top 5 cm, but some were recovered at all samplings from soil collected at greater depths. Emergence of J2 from cysts and numbers of females developing on corn roots in bioassays of cysts increased substantially between January and April. Cyst numbers in a fallow area of the corn field did not decline at any depth to 30 cm during 20 months. Free soil J2, J2 emerged from cysts, and females from the bioassay of cysts were highest at the first soil sampling in July after 10 months of fallow; numbers of nematodes in all three categories declined thereafter, but a few were still detectable after 20 months of fallow. Some cysts were still being recovered after 51 months from naturally infested field soil stored moist in the laboratory at 2 C and 24 C. Females were produced in the bioassays of cysts recovered from soil stored for 38 months at 24 C and for 32 months at 2 C. No free J2 were recovered from soil after 1 month of storage at -18 C, but even after 7 months storage J2 emerged from cysts that were recovered and many females developed in bioassays of those cysts.     

The influence of habitat on the distribution and abundance of metacercariae of Macravestibulum obtusicaudum (Pronocephalidae) in a small Indiana stream

Snails (Elimia livescens) from a central Indiana stream were examined for encysted metacercariae of Macravestibulum obtusicaudum (Pronocephalide) to determine the distribution and abundance of this parasite on its second intermediate host. Five samples of snails were collected, with 2 samples being restricted to high-flow (riffle) or low-flow (pool) areas of the stream. Snails (n = 386) were measured for shell length; the shell and the inner and outer surfaces of the operculum (in most samples) were examined for metacercariae. Seventy-five percent of snails (overall) had encysted metacercariae (range, 52-97%), primarily on the opercula. A significantly lower proportion of snails from riffles were infected, and these snails had significantly fewer cysts as well. Snails collected from pools showed up to 10 times as many metacercariae than those from riffles, although there was no significant difference in the proportion of snails with intramolluscan infections of M. obtusicaudum. The inner opercular surface appeared to be the preferred site of encystment in both flow regimes. Differences in microhabitats, in terms of both snails in the stream and metacercariae on the snails, clearly must be considered when evaluating the infection patterns of this trematode.     

In vitro and in vivo encystment of the cercariae of Echinostoma caproni

In vitro and in vivo studies were conducted on the cercariae of Echinostoma caproni. Of the 15 media tried, 2 resulted in effective in vitro encystment in petri dish cultures maintained at 23 +/- 1 C. They were a Locke's--artificial springwater (ASW) (1:1) medium (67% encystment) and a Biomphalaria glabrata embryonic cell line medium (23% encystment). To obtain large numbers of in vitro--formed cysts, finger bowl cultures containing 40 ml of the Locke's-ASW (1:1) medium were used at 23 +/- 1 C. Of 3,000 cercariae tested, 1,890 (63%) were encysted in this medium by 48 hr. Most of these cysts looked similar to those formed in vivo, although some showed abnormalities in the outer cyst wall and other malformations. A total of 200 in vitro-formed cysts treated in an alkaline trypsin-bile salts (TB) medium for 2 hr at 41 C showed 94% excystation. In vitro-formed cysts fed to mice produced ovigerous adults within 2 wk postinfection (PI). Eggs from these worms gave rise to miracidia that produced patent intramolluscan infections in B. glabrata snails. In vivo encystment was studied in lab-raised juvenile Helisoma trivolvis (Colorado strain) snails, 1-3 mm in shell diameter. From 6 to 24 hr PI, 93-100% of the cercariae were recovered as metacercarial cysts in the snail tissue. Treatment of these cysts in the TB medium resulted in 96% excystation within 2 hr at 41 C.     

Besnoitia darlingi (Brumpt, 1913) in Panama

SYNOPSIS. Besnoitia darlingi (Brumpt, 1913) Mandour, 1965 has been rediscovered in the common opossum Didelphis marsupialis in the Republic of Panama. A strain (D3) has been established in laboratory white mice. Proliferative crescents of the D3 strain are 6.1 (range 6.0-9.0) by 2.1 (range 1.7-4.0).
Mouse-adapted B. darlingi produced acute, fatal infections in white mice, hamsters, 14 marmosets ( Saguinus geoffroyi ), 2 squirrels ( Sciurus variegatoides and S. granatensis ), a woolly opossum ( Caluromys derbianus ) and a four-eyed opossum ( Philander opossum ) It probably produced chronic infections (cysts) in 2 wild-caughtopossums ( Didelphis marsupialis ) and one lizard ( Ameiva ameiva ). Animals in which induced infection could not be found after inoculation with trophozoites of mouse-adapted B. darlingi were: 2 adult and 2 new-born guinea pigs, laboratory rats, 1 night monkey ( Aotus trivirgatus ), 2 rhesus monkeys ( Macacca mulatta ), one iguana ( Iguaanaiguana ) and 2 baby caimans ( Caiman sclerops ).