Antibodies in the serum of golden hamsters experimentally infected with the intestinal trematode Echinostoma caproni.

The serum antibody response in golden hamsters (Mesocricetus auratus) infected with the intestinal trematode Echinostoma caproni was examined with ELISA, SDS-PAGE and Western blot, and IFAT techniques. All methods showed that the hamsters responded slowly but developed a clear positive humoral response to the infection. In most hamsters, an antibody response to infection could not be detected earlier than 11-13 weeks after infection with 6 or 25 metacercariae, and responses were weak when compared to previous results from mice infected with the same parasite. IFAT with positive hamster sera on live juvenile E. caproni showed only fluorescence at the posterior tip, which is a different pattern from that seen using from infected mice, indicating a different response to antigens on the juvenile parasites by these two hosts. The results are discussed in relation to the limited selfcure and development of resistance which is observed in golden hamsters infected with E. caproni.     

Comparative efficiency of infecting laboratory animals via intravenous and subcutaneous administration of Schistosoma mansoni cercaria

Comparative study on effectiveness of intravenous and subcutaneous methods of infection of animals has shown that infection rate of helminths after the injection of equal dozes of cercariae under skin, into portal and femoral veins of golden hamsters does not differ significantly (42.6 +/- 4.2, 37.8 +/- 5.8 and 26.0 +/- 6.6 schistosomes, respectively). When using the above methods for cotton rats the infection rate was lower than that in golden hamsters. The most insignificant infection rate of parasites was recorded in both species after the injection of cercariae into the femoral vein. Results of the infection of golden hamsters with different dozes of cercariae have shown that with the increase of dozes of infectious material the infection rate of helminths rises during the experimental intestinal schistosomiasis only to a definite level, which is attained by the injection of cercariae into the portal vein in dozes lower than those used for subcutaneous infection.     

Mallard ducklings (Anas platyrhynchos) experimentally infected with Echinostoma trivolvis (Digenea)

Of 8, day-old mallard ducklings, each fed 50 encysted metacercariae of Echinostoma trivolvis, 4 (50%) were infected 15-31 days postinfection (PI) with a total of 10 (2.5%) worms. The worms were attached loosely to the mucosa of the lower ileum and rectum-cloaca, and some were ovigerous by day 15 PI. Ducklings, 4-14 days old when fed encysted metacercariae, became infected with E. trivolvis adults, but ducks 150 days old were refractory to infection. Compared to our previous studies on experimental infections of echinostomes, mallard ducklings were less susceptible than golden hamsters to E. trivolvis.     

Life cycle and morphology of Metagonimus miyatai (Digenea: Heterophyidae) from Nagano,Japan

The life cycle of Metagonimus miyatai Saito, Chai, Kim, Lee and Rim, 1997 (Digenea: Heterophyidae) was studied in the Hiroi River at Kotobuki, Iiyama City, Nagano Prefecture, central Japan. Daughter rediae and cercariae were found in Semisulcospira libertina (Gould) and S. dolorosa (Gould) (Gastropoda: Pleuroceridae). Metacercariae were found encysted in Phoxinus lagowskii steindachneri Sauvage (Osteichthyes: Cyprinidae). Cercariae were experimentally exposed to P. lagowskii steindachneri, and metacercariae were obtained from the fish. Metacercariae of natural and experimental infections were experimentally fed to respective golden hamsters, and gravid adults identifiable as M. miyatai were recovered from the small intestine of the golden hamsters. The daughter redia, cercaria, metacercariae and adults are described. The life cycle of M. miyatai is discussed.     

Early stage biliary and intrahepatic migration of Opisthorchis viverrini in the golden hamster

In Thailand, infection with the liver fluke Opisthorchis viverrini is a serious health problem, with over 8.6 million human infections each year. Early stage biliary intrahepatic migration and infection of O. viverrini in the Syrian golden hamster were used to study the growth and development of this fluke. Fifty metacercariae of O. viverrini were introduced into each hamster by gastric intubation. Worms were found to migrate rapidly from the stomach to the gall bladder and hepatic duct, where they remained in relatively constant numbers until the end of week 8. Sexual development of worms was rapid, with full development of the uterus and testes by one and one half weeks and the appearance of eggs in the uterus by the beginning of the third week of infection. Worm growth as indicated by body length had ceased by week 8. Hamsters demonstrated development of a full reproductive cycle with in three to four weeks, and this generation continued until 8 weeks.     

Infectivity, growth, survival, and pathogenicity of Zygocotyle lunata (Trematoda) in experimental rodent hosts

Laboratory mice, rats, and golden hamsters were fed metacercarial cysts of Zygocotyle lunata to examine infectivity, growth, survival, and pathogenicity of this trematode. All 3 rodent types became infected with Z. lunata. Eggs of Z. lunata were seen in the feces of the hamsters by day 21, in mice by day 26, and in rats by day 44. Eggs teased from worms and embryonated in tap water hatched from day 21 to day 26 for rats and mice and from day 40 to day 45 for hamsters. The body areas of sexually mature worms were similar in all 3 types of rodent species. It was possible to reinfect all 3 species with Z. lunata metacercariae. No sign of clinical amphistomiasis was evident in the experimental animals. The histopathological responses were progressive, and severity was related to the age of the infection and the number of worms in the infection.     

Biological effects of Spirometra erinacei plerocercoids in several species of rodents

Observations were made of the biological effects on infection with plerocercoids of Spirometra erinacei on normal female Snell mice, male chinese hamsters, golden hamsters, normal and hypox rats. Plerocercoid infection caused the strongest growth-promoting effect on normal Snell mice. In mice, this effect appears to be independent of strain. Chinese hamsters infected with these larvae showed similar growth. The infected normal rats and golden hamsters, however, showed a weight increase in the skeletal muscle only, while the hypox rats exhibited no effect at all. The elevation in the concentration of serum triglyceride was observed in all the animals investigated except for rats. Golden hamsters, in particular, exhibited a marked increase in the concentration of serum free fatty acids and total cholesterol. There was close correlation between the concentrations of serum triglyceride and free fatty acids, and the regression coefficient of the resulting linear regression equation for the experimentals was higher than that for the controls. This suggests that serum triglyceride results from an increased concentration of serum free fatty acids derived from stimulated lipolysis. The total cholesterol concentration in the serum decreased in chinese hamsters infected with larvae. The serum glucose concentration increased in normal Snell mice but decreased in chinese and golden hamsters. No difference in glycerol and free fatty acid concentration was observed in infected animals except for golden hamsters.     

Transmission of chronic wasting disease identifies a prion strain causing cachexia and heart infection in hamsters

Chronic wasting disease (CWD) is an emerging prion disease of free-ranging and captive cervids in North America. In this study we established a rodent model for CWD in Syrian golden hamsters that resemble key features of the disease in cervids including cachexia and infection of cardiac muscle. Following one to three serial passages of CWD from white-tailed deer into transgenic mice expressing the hamster prion protein gene, CWD was subsequently passaged into Syrian golden hamsters. In one passage line there were preclinical changes in locomotor activity and a loss of body mass prior to onset of subtle neurological symptoms around 340 days. The clinical symptoms included a prominent wasting disease, similar to cachexia, with a prolonged duration. Other features of CWD in hamsters that were similar to cervid CWD included the brain distribution of the disease-specific isoform of the prion protein, PrP(Sc), prion infection of the central and peripheral neuroendocrine system, and PrP(Sc) deposition in cardiac muscle. There was also prominent PrP(Sc) deposition in the nasal mucosa on the edge of the olfactory sensory epithelium with the lumen of the nasal airway that could have implications for CWD shedding into nasal secretions and disease transmission. Since the mechanism of wasting disease in prion diseases is unknown this hamster CWD model could provide a means to investigate the physiological basis of cachexia, which we propose is due to a prion-induced endocrinopathy. This prion disease phenotype has not been described in hamsters and we designate it as the 'wasting' or WST strain of hamster CWD.     

Spatial variation in parasite-induced mortality in an amphipod: shore height versus exposure history

Characterizing the causes of spatial and temporal variation in parasite-induced mortality under natural conditions is crucial to better understanding the factors driving host population dynamics. Our goal was to quantify this variation in the amphipod Paracalliope novizealandiae, a second intermediate host of the trematode, Maritrema novaezealandensis. If infection and development of trematode metacercariae are benign, we expected mature metacercariae to accumulate within amphipods inhabiting high infestation areas. In field samples, intensity levels of mature metacercariae decreased linearly when amphipods harbored >5 immature metacercariae. This finding is consistent with the hypothesis that the parasite can be detrimental at high intensities of infection. Short-term field experiments showed that host survival also declines with the intensity of new infections and drops below 80% when early stage metacercariae reach 10 amphipod^?1. However, parasite effects varied over space and time. High-shore amphipods suffered an increased risk of infection in the summer and a lower likelihood of survival: there was a 10–30% decrease in survivorship for any given infection intensity at high- versus low-shore locations. We also tested for differences in the susceptibility of naive and exposed populations using transplant experiments, and found that naive amphipods acquired greater parasite loads (on average, 4.7 vs. 2.8 metacercariae amphipod^?1). Because survival decreases rapidly with infection intensity of both early- and late-stage metacercariae, naive populations would suffer considerably if the parasite were to increase its range. Our results indicate that trematode infections cause high mortality in amphipods during summer months under natural conditions, and emphasize that the effects of parasitism vary at local spatial scales and with exposure history.     

Functioning of opisthorchiasis-tuberculosis parasitocenosis at different stages of invasion (experimental investigation)

In experiments on golden hamsters the mutual influence of the co-members of opisthorchiasis-tuberculosis parasitocenosis has been established. This mutual influence depends on the stage of invasion and the state of the immune reactivity of the host. After additional immunization of the experimental animals with sheep red blood cells (SRBC) parasitocenosis formed special immune response different from those observed in both opisthorchiasis and tuberculosis. In cases of mixed pathology (opisthorchiasis-tuberculosis), reproduced at the acute stage of invasion, additional body reserves are seemingly switched on, thus leading the immunity system to increased functioning with respect to specific and heterologous antigens. In the chronization of invasion a decreased formation of antibodies to heterologous antigens (SRBC) together with a simultaneous decreased level of specific antiopisthorchiasis and antituberculosis immune response suggest that the reserve capacities of the host immune system, especially of humoral factors, are exhausted.     

Hepatobiliary changes, antibody response, and alteration of liver enzymes in hamsters re-infected with Opisthorchis viverrini

We investigated pathological changes, antibody response, and liver enzymes in hamsters re-infected with Opisthorchis viverrini. Group 1 received a single dose of 50 metacercariae; Groups 2 and 3 were first dosed with of 30 metacercariae and re-infected with 20 more once or twice at three month intervals. Inflammation and liver cell necrosis were observed on 3D (day 3) for Group 3 and 7D for Group 2 in comparison with 21D for Group 1. Pathological changes included peri-ductal fibrosis, bile duct dilation, and small bile duct formation. Increased O. viverrini-specific IgG levels ranked in the order Group 3>Group 2>Group 1. Liver enzyme activity was related to inflammatory cell infiltration. Re-infection induced faster inflammation and more severe pathological changes in association with parasite-specific antibody during chronic inflammation. This study emphasizes that there is an important relationship between the gradual decreases of inflammation with a concomitant increase in fibrosis after re-infection.     

Comparative histopathology of Opisthorchis felineus and Opisthorchis viverrini in a hamster model: an implication of high pathogenicity of the European liver fluke

European liver fluke (Opisthorchis felineus) and Asian liver fluke (Opisthorchis viverrini) are similar in morphology but comparative pathology of the infections has not been described. We therefore did comparative histopathology of both parasites in an experimental animal model. The study was conducted in 3 groups of 105 Syrian golden hamsters; the first and second groups fed with 50 metacercariae of O. felineus (OF) or O. viverrini (OV) and the last group was uninfected controls. Five hamsters in each group were euthanized on weeks 1, 2, 4, 8, 12 and 24 post-infection. The liver tissue was fixed and processed for routine histopathology and immunohistochemistry for proliferation markers (BrdU or PCNA). Overall, the liver histopathology of O. felineus and O. viverrini infection was generally similar. However, various histopathogical features including intense inflammation, fibrosis, biliary and goblet cell hyperplasia and dysplasia occurred earlier in the OF group. In addition, the existence of precancerous lesions such as cholangiofibrosis in a long-term infection was observed only in this group. O. felineus is larger in size than O. viverrini which, together with its excreted and secreted antigens, likely is crucial in the induction of liver fluke induced disease. The differences in nature and timing of the histopathological profile indicate that opisthorchiasis caused by the European liver fluke O. felineus is more pathogenic than its Asian relative O. viverrini.     

Cutaneous Leishmaniasis in the Dorsal Skin of Hamsters: a Useful Model for the Screening of Antileishmanial Drugs

Traditionally, hamsters are experimentally inoculated in the snout or the footpad. However in these sites an ulcer not always occurs, measurement of lesion size is a hard procedure and animals show difficulty to eat, breathe and move because of the lesion. In order to optimize the hamster model for cutaneous leishmaniasis, young adult male and female golden hamsters (Mesocricetus auratus) were injected intradermally at the dorsal skin with 1 to 1.5 x l0⁷ promastigotes of Leishmania species and progression of subsequent lesions were evaluated for up to 16 weeks post infection. The golden hamster was selected because it is considered the adequate bio-model to evaluate drugs against Leishmania as they are susceptible to infection by different species. Cutaneous infection of hamsters results in chronic but controlled lesions, and a clinical evolution with signs similar to those observed in humans. Therefore, the establishment of the extent of infection by measuring the size of the lesion according to the area of indurations and ulcers is feasible. This approach has proven its versatility and easy management during inoculation, follow up and characterization of typical lesions (ulcers), application of treatments through different ways and obtaining of clinical samples after different treatments. By using this method the quality of animal life regarding locomotion, search for food and water, play and social activities is also preserved.     

The change of behaviour of two strains of Leishmania after cultivation in a defined medium

Attempts have been made to characterize two strains of Leishmania that became infective to golden hamsters only after they had been maintained for several years in a chemically defined culture medium. Observations were made on the growth rates of promastigotes in vitro, course of infection in hamsters, morphology of amastigotes, and electrophoretic mobility patterns of eight isoenzymes. Information was obtained about the buoyant densities of n-DNA and k-DNA, and one strain was tested against monoclonal antibodies. The identity of both strains remains obscure.     

Geographical distribution of Metagonimus yokogawai and M. miyatai in Shizuoka Prefecture, Japan, and their site preferences in the sweetfish, Plecoglossus altivelis, and hamsters

Sweetfish, Plecoglossus altivelis, obtained from 18 rivers in Shizuoka Prefecture were examined for metacercarial infection of 2 flukes, Metagonimus yokogawai and Metagonimus miyatai. The infection rate and density of metacercariae in the fish were higher in eastern and western regions than in central region of the prefecture. After infection of hamsters with metacercariae derived from the scale, 98.7% of the adult worms obtained from the intestine was found to be M. miyatai. Conversely, from infection with metacercariae from the flesh, 90.0% of the worms was M. yokogawai. Since the worms had no exclusivity in the tissues, we conclude that the flukes have location preference with the former primarily preferring the scale, and the latter the flesh. Fish from two rivers located in adjacent areas in the western region had relatively a higher ratio of M. yokogawai in the scale relative to other rivers, suggesting an intraspecific genetic variation due to geographical isolation. On examination of adult worms in the hamster's intestine, M. yokogawai was mainly located towards the anterior part of the intestine, unlike M. miyatai, suggesting that in mammalian host too, the parasites have site preference.     

Development of resistance to reinfection by Clonorchis sinensis in rats

We investigated the induction of resistance to Clonorchis sinensis infection by prior infection in rat and hamster models. Animals were challenged with C. sinensis metacercariae, then treated with praziquantel and reinfected. Worm recovery rate in reinfected animals was used to estimate resistance to reinfection. The determined resistance rates to reinfection in rats and hamsters were 97.7% and 10.3%, respectively. In rats, cure from the primary infection of C. sinensis increased resistant to reinfection, and the greater the worm burden and the longer the duration of primary infection, the higher was the resistance rate. For primary infection doses of 10, 40 and 100 metacercariae per rat, the resistance rates were 87.4%, 93.8% and 98.4%, respectively. The resistance rates in rats after 2 or 8-week primary infection were 78.7% and 95.3%, respectively. All worms recovered from reinfected rats were immature. When cured rats were administered with methylprednisolone, resistance to reinfection became impaired. These findings indicate that rats develop a high degree of resistance to reinfection by C. sinensis after cure. The growths and maturations of reinfected worms were also impaired.     

Multiplication of Legionella pneumophila Philadelphia-1 in cultured peritoneal macrophages and its correlation to susceptibility of animals

Intracellular growth of Legionella pneumophila Philadelphia-1 strain in peritoneal macrophages (PMP) from various rodents was measured and its correlation to the level of susceptibility of the animal was examined. In guinea pig PMP, the organism grew well and the guinea pig was very susceptible to it (50% lethal dose, LD50 = 7.6 X 10(4)). On the other hand, the bacteria hardly multiplied in mouse PMP and the animal was resistant to infection (LD50 = 6.7 X 10(7)). Intracellular growth rate correlated well with susceptibility in these animals. In golden hamsters, a discrepancy between intracellular growth and susceptibility was found. The organism grew intracellularly as rapid as in guinea pig PMP, but the golden hamster was very resistant to infection (LD50 = 2.2 X 10(8)). In rat PMP, the organism did not grow intracellularly during a 24-h period of infection, but started to grow after that and the growth rate thereafter was as rapid as in guinea pig PMP. WKA rats were resistant and the LD50 in the animal was 1.9 X 10(7). In vivo natural resistance of rats and golden hamsters to the organism was considered to be a result of other factors than macrophages.     

Extraintestinal strobilar development of immature Echinococcus multilocularis in laboratory rodents following intratracheal inoculation of the protoscoleces

Intratracheal inoculation of Echinococcus multilocularis protoscoleces was performed in prednisolone tertiary-butylacetate(PTBA)-treated and untreated golden hamsters and AKR/J mice. Repeated PTBA treatments prior to the day of inoculation prevented the influx of neutrophils against the cestode. More than 1 month after infection, living immature adult forms of E. multilocularis, showing some somatic prolongation, were recovered from the pulmonary alveolar space of PTBA-treated golden hamsters, in the absence of any cystic development.     

Sensibilité comparée de divers animaux de laboratoire à l'infection par instillations nasales de la phase saprophytique d'Emmonsia crescens Emmons & Jellison, 1960: Fréquence et intensité du parasitisme,réactions histopathologiques

Comparative observations were made on the development of Emmonsia crescens in the lungs of laboratory rats and mice, golden hamsters and guinea pigs after a nasal instillation of a heavy suspension of the saprophytic phase of the fungus. 95% of 80 experimental rats were found to be parasited against 80% of 200 inoculated mice, while only 30% of 70 hamsters and all of 4 guinea pigs showed an infection. The lungs of the mice, rats and guinea pigs were frequently more heavily infected than those of the hamsters. In addition, the adiaspores obtained from the mice and rats had, on average, a diameter double those from the hamsters and their walls were thicker. Thus, the laboratory mice and rats were shown to be better hosts of E. crescens than were golden hamsters.     

Species affiliation of metacercaria of the genus Metorchis (Trematoda, Opisthorchidae) from fishes in Western Siberia

Two larval species of the genus Metorchis, M. bilis and M. xanthosomus, are reported from fishes of West Siberia. Larvae of the first species can develop into adult forms in birds (terns, gulls, ducks) and in mammals (cats, golden hamsters, white mice). Larvae of the second species developed only in ducks. Experimental infection of golden hamsters, white mice and black terns with M. xanthosomus failed. On the results of the experimental infection and literary data the synonyms, M. bilis and M. xanthosomus, are given.