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Thirty-one of 290 cats (10.7%) from the area around St Louis, Mo, were infected with Eurytrema procyonis. In some cats, the pancreas was severely affected, with almost complete atrophy and fibrous replacement of the gland. Both bicarbonate and protein secretions were impaired, although clinically evident pancreatic insufficiency was not seen.
All polyopisthocotylean monogeneans previously studied, including representatives of the Polystomatidae infecting anuran amphibians, feed on host blood. However, the present analysis of species of Polystomoides, Polystomoidella and Neopolystoma, polystomatids which infect chelonian reptiles, has shown that this group has diverged nutritionally from related parasites. Histochemical tests failed to demonstrate haemoglobin in the gut caeca, and X-ray microanalysis confirmed the absence of haematin (or high concentrations of bound iron) in the gastrodermis. The chelonian polystomatids (and also the single monogenean which infects a mammal, Oculotrema hippopotami) feed on epithelial cells and mucus, the diet typical of monopisthocotyleans. Transmission electron microscopy revealed the same gastrodermal architecture in representatives of Polystomoides from Africa, N. America and S.E. Asia. The organization of the caecal epithelium conforms with that of blood-feeding polyopisthocotyleans, with two components: lamellated cells responsible for intracellular digestion interspersed with elements of a non-lamellated connecting syncytium. In other polyopisthocotyleans, the syncytium probably has a skeletal, supportive role, related to the problems of intracellular accumulation of haematin, but in polystomatids infecting chelonians the syncytium is extremely reduced and its presence probably reflects an ancestry amongst blood-feeding relatives. The utilization of the presumably more primitive monogenean diet of epithelial cells and mucus by chelonian polystomatids may be related to the scarcity of superficial blood vessels in their oral and urinary bladder habitats.
The life span and the pathogenicity of amphistomes developing from Cercariae indicae XXVI (Paramphistomum epicilitum) were considerably reduced when the metacercariae were gamma-irradiated at 2 krad or 3 krad. The higher irradiation dose resulted in the complete absence of the flukes in infected animals. Single vaccination of lambs and kids with 3000 metacercariae irradiated at 2 krad or 3 krad stimulated a significant degree of resistance against challenge with 5000 non-irradiated metacercariae. The resistance was more pronounced in the group vaccinated with metacercariae irradiated at 3 krad.
An indirect enzyme-linked immunosorbent assay (ELISA) using 27 kDa glycoprotein of Fasciola gigantica has been evaluated for its potential use in the diagnosis of bovine fasciolosis. Following experimental infection of rabbits, F. gigantica infection-induced antibodies were isolated and later used as ligands in affinity chromatography for isolation of infection-induced antibody-specific proteins. Among the five infection-specific proteins isolated, a glycoprotein of 27 kDa was later isolated by second-step purification using concanavalin A matrix. In crossbred cattle receiving different doses of infection (100, 200 and 400 metacercariae), the anti-27 kDa antibodies were detected as early as the 2nd week post infection. No direct correlation between initial dose, antibody response and fluke establishment was recorded. No cross-reaction was noted with the sera of goats experimentally infected with Paramphistomum epiclitum. ELISA with the 27 kDa glycoprotein could be a feasible diagnostic tool for the early detection of bovine fasciolosis.
As the major contagious epidemics in the tropics are today more or less under control, the most important diseases of livestock are due to parasitic infections. Precise knowledge concerning the biology of parasites and their seasonality is a prerequisite for any control strategy. Therefore, epidemiological investigations into the effect of helminths on ruminant livestock production must include I. A vertical section through the age dependent helminthic burden of a representative number of animals of a given population, i.e. the sampling of faeces at regular intervals during the first 18 months of life. II. Investigations into the horizontal development of the helminthic situation, whether soil-transmitted and/or vector-transmitted. a. The seasonal fluctuation of egg excretion from gastrointestinal nematodes. b. The seasonal incidence of nematode larvae on pastures. c. The seasonal survival time of nematodes larvae on pastures. III. The seasonal fluctuation of vector snails and their incidence of infection with trematode larvae. For the economic evaluation of control measures it is necessary that the following parameters should be recorded: The age dependent mortality rate, the development of the average body weight, the birth/slaughter weight, the age at first calving and the calving intervals.
Experimental infections of the marine topshell Gibbula umbilicalis with Lecithochirium furcolabiatum (Digenea: Hemiuroidea) have allowed the development of a model system which will enable further studies of the molluscan host response. The long-lived intertidal prosobranch host is easily maintained in the laboratory, and experimental infection rates of 98% were consistently achieved. The miracidium and mother sporocyst have been studied at both light and ultrastructural levels, providing the first account of the morphology of these stages in Hemiuridae. The ingested egg hatches within the host intestine, treatment with L-cysteine and alkaline pH stimulating miracidial emergence in vitro. The general body surface of the miracidium is devoid of spines or cilia, the latter being restricted to four plates near the anterior extremity. The miracidium swims actively prior to penetration of the gut wall, the sporocyst being released from the miracidial epidermal coat within the haemocoel. Within 5 weeks of infection, the filamentous mother sporocyst contains 1 to 3 oval germ balls, daughter sporocysts being recorded free within the digestive gland haemocoel 7 weeks later. Twenty three weeks after ingestion of eggs, the daughter sporocyst extends into the host gill filaments, containing cystophorous cercariae ready for emergence.
The bird nasal schistosome Trichobilharzia regenti is a new agent of cercarial dermatitis. Cercariae are able to penetrate the skin of birds and mammals including man. The parasite then attacks the central nervous system. The present study has shown that schistosomula avoid penetration of blood capillaries and enter the peripheral nerves of the legs of mice and ducks as early as 1 day post-infection (p.i.) and 1.5 days p.i., respectively. These peripheral nerves are used as a route to the spinal cord. In the specific host (duck) schistosomula were found in the spinal cord from 2 days p.i. until 15 days p.i. and in the brain from 12 days p.i. until 18 days p.i. In non-specific hosts (mice; inbred strains BALB/c, hr/hr, SCID) living schistosomula were found in the spinal cord from 2 days p.i. until 21 or 24 days p.i. (depending on the mouse strain) and in the brain of two (BALB/c, SCID) of three inbred strains from 3 days p.i. until 24 days p.i. No correlation was found between the infection dose and clinical status of the experimental hosts. A high affinity of schistosomula for the peripheral nerves was also proved in vitro, suggesting a new type of migratory behaviour in schistosomatids.
The susceptibility of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) to the monogenean Discocotyle sagittata in the United Kingdom was assessed by experimental infection of naive fish. One month postinfection with 100 oncomiracidia/host, brown trout harbored significantly lower burdens (27.7 worms/host +/- 4.13 SE) than rainbow trout (47.8 worms/host +/- 3.90; P = 0.002). This indicates that the consistently lower prevalence and intensity of D. sagittata recorded in naturally infected farmed fishes reflects differences in susceptibility to the parasite. The outcome may be related to the comparatively short-term association of this parasite with rainbow trout (introduced to Britain in the 1880s) compared with the established native host-parasite association.
An epidemiological study of Metagonimus infection was undertaken along the upper reaches of the Namhan River, with special consideration on the species (type) of the worms collected from humans. Eggs of Metagonimus spp. were detected from 15 (9.7%) of 154 people examined in Umsong-gun, and from each infected person (5 cases) 6,015-24,060 worms (mean 13,233) were recovered after treatment with praziquantel (10 mg/kg). Eggs were also detected from 37 (48.1%) of 77 people in Yongwol-gun, from whom (27 cases) 1-4,965 worms (means 1,215) were collected. The worm from Umsong-gun consisted of both Metagonimus Miyata type and Metagonimus takahashii, whereas those from Yongwol-gun consisted of only Metagonimus Miyata type. When the uterine eggs of the two kinds and M. yokogawai (obtained from people in Tamjin River basin) were morphologically compared, it was suggested that the egg size should be a good indicator for discrimination of the species or type. The source of human infection was proved to be fresh water fishes; 49 of 52 Zacco platypus examined, 6 of 8 Hemibarbus longirostris, 13 of 15 Pseudogobio esocinus, 4 of 6 Odontobutis obscura interrupta, and 17 of 18 Carassius carassius were found infected with Metagonimus metacercariae. From the results, it is concluded that the upper reaches of the Namhan River are endemic foci of Metagonimus Miyata type and M. takahashii.
Eggs with filaments were detected in the faeces of Macaca mulatta. On the basis of morphological indications and reports from the literature, this infection was most probably caused by the genus Ogmocotyle. Egg output and the onset of diarrhoea were arrested by treatment with 20 mg fenbendazole/kg body weight for 5 days in the form of medicated feed. Follow-up studies over 9 months showed neither new egg output nor the occurrence of clinical symptoms.
Studies on infection patterns of diplostomid parasites in commercially exploited fishes have not been done in Patagonia (Argentina). The aim of this work was to study the population dynamics of two diplostomid species in the brain of patagonian silversides (Odontesthes hatchery), the interaction between them, and effect on health and physical condition of the hosts. Tylodelphys destructor and Diplostomum mordax metacercariae in the brain of Patagonian silversides in Lake Pellegrini were studied between January 1991 and February 1992. Tylodelphys destructor parasitized all silversides examined; prevalence of D. mordax varied between 7% and 100%. Mean intensity for T. destructor was 35-140 and for D. mordax was 3-49. Highest mean intensities of T. destructor coincided with the lowest mean intensities of D. mordax. Recruitment seems to occur from July-November for T. destructor and from April-June for D. mordax, revealing a temporal segregation with inverse patterns of infection and recruitment. Tylodelphys destructor has higher intensities in the brain of the older fish, whereas D. mordax did not, suggesting another type of segregation. There were no evidences of gross pathology. No covariation between abundance of larvae and condition factor, gonadosomatic index, and gut fullness was detected.
Two stray dogs were found naturally infected with adult Alaria nasuae in Tamaulipas, Mexico. This is the first report of this species from a domestic dog, the first report of it from Mexico, and the first time the species has been recorded since its original description.
The transmission of Cyclocoelum mutabile to snails was examined under natural conditions by sampling the snail communities of 4 natural ponds that had been exposed experimentally to infection by laboratory-infected coots (Fulica americana). Five of 6 snail species in the ponds, Physa jennessi, Promenetus exacuous, Armiger crista, Gyraulus parvus, and Stagnicola elodes, became infected. No natural infections were found in the few Helisoma trivolvis examined. The second most abundant species Promenetus exacuous was infected most often, whereas Physa jennessi, the most abundant species present, was rarely infected. The temporal pattern of infections in the snail community suggests the transmission window of this parasite in southern Manitoba is limited by both the 14 C hatching threshold of the fluke eggs and the seasonality of ovigerous infections in the coot host. No naturally overwintering infections were found in snails from these ponds, which were examined the following spring. None of the 1,120 laboratory-infected snails placed in cages and held overwinter in the ponds survived, whereas 14 of the 1,120 uninfected control snails kept in the same cages survived. These results are consistent with the hypothesis that C. mutabile must be reestablished in northern waterfowl breeding areas each spring.
Susceptibility and development of Clinostomum complanatum in the chicken (Gallus gallus domesticus) have been studied. The progenetic metacercariae of C. complanatum developed into ovigerous worms in 3 days in the buccal cavity of the chicken and survived only 6-7 days in this experimental host. The susceptibility is influenced by the age, sex and breed/type of the host. Both percent susceptibility and recovery of the worms decreased with increase in the age of the host. The egg laying chickens were found to be least susceptible to the infection. Mature male chickens were more susceptible than the females. The single comb white Leghorn (SCWL) was found to be susceptible while the local type (LT) and the cross breed (SCWLxLT) were not susceptible to C. complanatum. The possible reasons for these variations have been discussed.
Thermal effects on the dynamics of infection with metacercariae of Diplostomum baeri and D. spathaceum were monitored between May and September, in a year-class of perch Perca fluviatilis, in an artificial lake receiving warm water discharges from a nuclear power station and in an unheated reference site, for a two year period. In the heated area the prevalence of infection of the retinal form, D. baeri, was always 100%, whereas in the unheated site there was an increase from 93% in May to 100% in June 1986. The relative density of D. baeri was found to increase gradually during the first summer in both areas, although the accumulation rate of metacercariae was significantly increased in the heated area. In August of the first year the relative density of D. baeri peaked in the heated area, whereas it continued to increase in the unheated control. However, in September of the following year, the relative densities were at the same level in both thermal regimes. A concomitant decline in the degree of overdispersion of metacercariae within the host population was observed in the heated area as the population density of metacercariae decreased, whereas the index of dispersion remained at the same level throughout the study in the unheated area. However, it was not possible to sample perch in the unheated area between October 1986 and May 1987 and changes in the parasite population could have occurred during this period. The prevalence and relative density of D. spathaceum, the lens form, was on the contrary low, especially in the unheated site where it was recorded only occasionally. The infection of D. baeri exhibited a convex pattern in both thermal regimens, although the peak infection was noticed earlier in the heated area. Regulation of the parasite infrapopulation may have been achieved by the combined effects of a decreased transmission rate of cercariae with increasing age of the host, the mortality of metacercariae as a natural termination of the life span and to selective predation of heavily infected hosts. However, regardless of an increased accumulation rate of metacercariae in the heated area, the relative densities of D. baeri became equal in both thermal regimes at the end of the study. The mortality rate of metacercariae in the heated area was therefore presumably increased as compared with the unheated reference site.
Using soles (Solea solea) infected experimentally with oncomiracidia of the monogenean skin parasite Entobdella soleae, it was found that the parasite begins to assemble eggs at about 85 days post infection and may survive for as long as 6 1/2 months at 12 +/- 1 degrees C. Growth of the anterior hamuli continues throughout life but the growth rate decreases with time. The oldest (largest) parasites recovered from laboratory soles were similar in size to the largest parasites collected in the wild.
Three free-ranging raccoons caught in southeastern Florida were found to be infected by Heterobilharzia americana. The livers were firm with rough surfaces and stellate patterns of periportal fibrosis. The portal tracts had excessive mature fibrous connective tissue and occasional ovum and necrotic fluke granulomas. There were also ovum granulomas with concomitant lesions in small and large intestine, pancreas, and lung. Numerous other parasites were seen.
Genus Metagonimus has been a subject of taxonomic debates for several years. In morphological aspects, M. yokogawai has been thought to have three subtypes, namely Yokogawa type (M. yokogawai in strict sense), Miyata type and Koga type, But differences in the intestinal pathology induced by these subtypes have not been studied yet. In this study we compared the pathological reactions induced by M. yokogawai and Metagonimus Miyata type using proliferating cell nuclear antigen (PCNA) index. Metacercariae (Mc) of M. yokogawai were collected by artificial digestion of Plecoglossus altivelis and Mc of Metagonimus Miyata type were collected from Zacco platypus. Three hundreds Mc of each species were infected orally to ICR mice. The mice were sacrificed at 3, 6, 10, 16 and 23 days after infection and the small intestines were resected into three portions (proximal, middle, and distal). Immunohistochemical staining for PCNA was done using PC-10 (DAKO-PCNA, CA, USA). The PCNA indices in M. yokogawai infected group on the 6th and 23rd day after infection were lower than in the control and Miyata type infected groups (p < 0.05) from all of the three intestinal regions. On the other hand, the control group and Metagonimus Miyata type infected group did not make any differences in PCNA indices. The villus/crypt (V/C) ratio was also decreased significantly in M. yokogawai infected mice but not in Metagonimus Miyata type infected ones. It is suggested that M. yokogawai induce villous atrophy through a decrease in the cell proliferation at the crypt. The results of this study suggested that M. yokogawai induce more serious intestinal pathology than Metagonimus Miyata type.