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W L Shoop

Publications and source records attributed to W L Shoop.

53 records · Page 3Linked to original sources
PubMed1990

Laboratory selection of a benzimidazole-resistant isolate of Trichostrongylus colubriformis for ivermectin resistance.

In vivo ivermectin resistance was selected in an isolate of Trichostrongylus colubriformis (TcR) already known to be benzimidazole resistant. This was accomplished in sheep by using levels of ivermectin calculated to reduce the fecal egg output from each generation of T. colubriformis by congruent to 95%. The first indication of ivermectin resistance was observed with the F10. A dosage-titration trial comparing the parent TcR with the ivermectin-selected F21 demonstrated that the latter was congruent to 20 times more resistant to oral ivermectin therapy in experimentally infected sheep than was the parent isolate. Treatment of the F16 generation with 50 mg/kg of thiabendazole resulted in only 54% egg reduction and confirmed that benzimidazole resistance was stable.

Animals↗
PubMed1990

Anthelmintic activity of paraherquamide in sheep.

Paraherquamide, an oxindole alkaloid metabolite of Penicillium paraherquei, was tested against the common gastrointestinal nematode species of sheep at 0.25, 0.5, 1.0, and 2.0 mg/kg, per os. It was highly efficacious (greater than or equal to 98% reduction) as a single oral treatment dosages greater than or equal to 0.5 mg/kg against adult Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, Trichostrongylus colubriformis and Cooperia curticei, and the L4 stage of Cooperia spp. Noteworthy is the fact the isolate of H. contortus used was ivermectin-resistant and the isolate of T. colubriformis used was ivermectin- and benzimidazole-resistant. This suggests a different mode of action for paraherquamide relative to ivermectin and the benzimidazoles. The adult stage of Oesophagostomum columbianum was the dosage-limiting parasite with 79% efficacy recorded at the highest treatment level (2.0 mg/kg). Extrapolation from the O. columbianum response curve suggests a dosage in excess of 4.0 mg/kg would be required to attain 95% efficacy.

Animals↗
PubMed1989

Experimental human infection with Fibricola cratera (Trematoda: Neodiplostomidae).

Fibricola cratera is a strigeoid trematode indigenous to North America that, heretofore, was known only to infect wild mammals. Herein, it is reported that an experimental inoculation of a human volunteer produced a patent infection that lasted 40 months. Symptoms of epigastric discomfort, loose stools and flatulence occurred over the first year of infection and ameliorated thereafter. Eggs per gram of stool were low (less than or equal to 2) throughout the course of infection and were not detected by the standard technique of formalin-ether concentration. To monitor infection, the entire stool sample was examined each month after sieving through No. 10 (pore size 2 mm) and 100 (pore size 145 microns) sieves and collecting eggs on a No. 325 (pore size 45 microns) sieve. This is the first report of a North American strigeoid trematode capable of maturing in a human and is only the second species of strigeoid known to do so. The other species is F. seoulensis which has been implicated in 26 human infections in Korea.

Adult↗
PubMed1989

Systematic analysis of the Diplostomidae and Strigeidae (Trematoda)

A systematic analysis of the genera in the Diplostomidae and Strigeidae was made using the Proterodiplostomidae as the outgroup. The Proterodiplostomidae was the family with the greatest preponderance of primitive characters and its monophyly was supported by the unique paraprostate gland. However, no character state supported the monophyly of the Diplostomidae sensu Dubois, 1970. That paraphyletic taxon was composed of 3 monophyletic groups: the pseudosuckerless Neodiplostomidae n. fam. had the most primitive character states of the 3 and its monophyly was based on characters in the neascus/neodiplostomulum metacercariae; the Bolbophoridae n. fam., with pseudosuckers, had its monophyly supported by characters present in the newly named prodiplostomulum metacercaria; and the emended Diplostomidae, also with pseudosuckers, had the most derived states and its monophyly was supported by characters present in the diplostomulum. The presence of pseudosuckers united the Bolbophoridae n. fam., the emended Diplostomidae, and the Strigeidae as a monophyletic assemblage. The Strigeidae had the most derived characters of these 3 taxa and its monophyly was supported by characters in the tetracotyle and the cup-shaped forebody and bilobed tribocytic organ of the adult. In general, the adult stages of these strigeoid families showed very conserved morphology and it was the metacercariae that possessed the innovations. The conserved adult morphology was typical of what one might expect if the intramolluscan stages were analyzed. Thus, the data were concordant with the view that the mollusc and vertebrate definitive host were the original hosts to the Digenea and that the second intermediate host and metacercaria were more recently intercalated. More specifically, the phylogeny of these groups suggested that ancestral bisegmented strigeoids originally infected reptiles, they subsequently radiated into birds with which they coevolved extensively, and on 5 separate occasions they radiated into mammals. The radiations into mammals were, by all available evidence, preceded by second intermediate host shifts from fish to amphibians.

Animals↗
PubMed1989

Alaria nasuae (Trematoda: Diplostomidae) from domestic dogs.

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.

Animals↗
PubMed1988

Trematode transmission patterns.

The primitive transmission pattern in the Trematoda is a 1-host pattern in which an aspidocotylean matures in a mollusc. The progeny from the parent aspidocotylean typically disseminate from the mollusc to establish in others, but the possibility that some progeny remain in the same mollusc as did the parent and produce a sequential generation exists. It is this potential for sequential generations in the mollusc that may be the key to understanding the complex transmission and life cycle patterns in the Digenea.

Animals↗
PubMed1987

Maternal transmission by Alaria marcianae (Trematoda) and the concept of amphiparatenesis.

The term amphiparatenic host was coined originally for hosts of Alaria marcianae that as adults are paratenic hosts, but as juveniles serve as definitive hosts. In this study the concept of amphiparatenesis is placed in a theoretical context, maternal transmission shown to be the basic mechanism, and the concept extended to include Toxocara canis, T. cati, T. pteropodis, Neoascaris vitulorum, Ancylostoma caninum, Uncinaria lucasi, various species of Strongyloides, Pharyngostomoides procyonis, and P. adenocephala. Alaria marcianae mesocercariae were used in a feline model to show that male and nonlactating female cats are definitive hosts, but lactating cats are primarily paratenic hosts. Inoculation of 1 female cat resulted in the infection of 21 of her offspring via the milk over the course of 5 litters and after a 3-yr period she still had viable larvae in her tissues. The ability of parasites to remain immature in amphiparatenic hosts is believed to be an adaptation on the part of the parasite to promote dissemination through maternal transmission and not the result of resistance, immunological or otherwise, on the part of the host. The amphiparatenic concept has important implications that include: the use of pregnant and lactating females as reservoirs of infection for the offspring; infection transmitted through a contagious transplacental or transmammary pathway; a parasite population structure in which adult worms are in greater abundance in neonate than adult hosts; and the effective control of parasites utilizing this strategy proving to be very difficult.

Animals↗
PubMed1987

Helminths of the raccoon (Procyon lotor) in western Kentucky.

Seventy raccoons (Procyon lotor) from western Kentucky were examined for helminths from December 1985 through May 1986. Twenty-three species of helminths were collected including 10 species of Trematoda (Brachylaima virginiana, Euryhelmis squamula, Eurytrema procyonis, Fibricola cratera, Gyrosoma singulare, Maritreminoides nettae, Mesostephanus appendiculatoides, Metagonimoides oregonensis, Paragonimus kellicotti, Pharyngostomoides procyonis), 2 species of Cestoda (Atriotaenia procyonis, Mesocestoides variabilis), 10 species of Nematoda (Arthrocephalus lotoris, Baylisascaris procyonis, Capillaria putorii, C. plica, Crenosoma goblei, Dracunculus insignis, Gnathostoma procyonis, Molineus barbatus, Physaloptera rara, Trichinella spiralis), and 1 species of Acanthocephala (Macracanthorhynchus ingens). A mean of 6.4 (3-11) helminth species per host was recorded. Fibricola cratera, Atriotaenia procyonis, Mesocestoides variabilis, Arthrocephalus lotoris, Capillaria plica, Dracunculus insignis, Molineus barbatus, and Physaloptera rara were ubiquitous parasites of the raccoon, whereas specific nidi were observed for Eurytrema procyonis, Gyrosoma singulare, Paragonimus kellicotti, Baylisascaris procyonis, Trichinella spiralis, and Macracanthorhyncus ingens. With an overall prevalence of 10% or higher, 15 of the 23 helminth species were considered common parasites of the raccoon in western Kentucky. When the 10% prevalence rate was applied within geographical quadrants to correct for the presence of nidi it was found that 18 of the 23 helminth species were common and 5 were regarded as rare parasites of the raccoon. Two species of nematodes, T. spiralis and B. procyonis, displayed a markedly higher prevalence in male raccoons.

Acanthocephala↗
PubMed1984

Transmammary infection of newborn by larval trematodes.

Newborn cats and mice became infected with Alaria marcianae if they nursed from females that had been experimentally infected with the parasite. All lactating females showed mesocercarial stages in their mammary glands. This may be the first trematode found to undergo transmission through the mammary glands under experimental conditions. Similarities in the behavior of mesocercariae in humans and in the mouse suggest that an infected human female might infect her infant if she elected to nurse it.

Animals↗
PubMed1984

Tegumental changes of Alaria marcianae (Trematoda) during migration in the domestic cat.

Mesocercariae of Alaria marcianae were removed from snake paratenic hosts and fed to domestic cats. The cats were necropsied at specified intervals, the parasites recovered, and studied by SEM. During the prepulmonary phase of migration in cats, mesocercariae recovered from the stomach wall, abdominal cavity, diaphragm, liver, and heart underwent no tegumental modification compared to those fixed immediately after removal from the paratenic host. The mesocercaria resembled the body of an enlarged cercaria. The oral sucker was encircled by 14 or 15 rows of simple, posteriorly directed spines. Similar spines were also located along the margins of the venter and equatorially at the level of the acetabulum. This spinal pattern left two regions, one anterior and one posterior to the acetabulum, devoid of spines. Uniciliate papillae were found in a distinct pattern associated with the spined areas. In the pulmonary phase, the mesocercariae transformed into diplostomula. Earlike lappets on either side of the oral sucker developed with subsequent differentiation of microvilliform processes on their ventral sides. Body spines divided to give rise to three-pronged serrations. A depression on the venter between the acetabulum and posterior end of the body gave rise to the tribocytic organ. Stout, densely-clustered spines arose de novo on this organ. A rudimentary cylindrical hindbody gave the diplostomulum a distinct scoop-shaped appearance. Worms coughed up from the lungs and swallowed were later found in the duodenum. This postpulmonary phase of migration was a quick event and young worms in the duodenum were indistinguishable from those in the lungs. Within 4 days, the diplostomula in the duodenum matured to adulthood.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Pathway of mesocercariae of Alaria marcianae (Trematoda) through the mammary glands of lactating mice.

Lactating mice were infected with mesocercariae of Alaria marcianae to demonstrate more precisely how these parasites migrate within the mammary glands. The infected dam that first transmitted larvae to all of her young was necropsied and her mammary glands removed and sectioned serially. Mesocercariae penetrated the dense connective tissue surrounding the lobules. Within the stroma the larvae migrated along tracks of fat cells and were consistently found in pools of milk created from the destruction of alveoli. These pools of milk led directly into the large lactiferous ducts. It was notable that no mesocercaria was found in the lactiferous or galactiferous ducts indicating that clearance from these vessels was rapid. No larva was found in any blood vessel nor was any significant hemorrhage demonstrable. Lack of an inflammatory response surrounding the worm was characteristic, although large numbers of neutrophils were scattered diffusely throughout the lobules, and multiple, proliferative lymph nodules were present.

Adipose Tissue↗
PubMed1983

Transmammary infection of paratenic and definitive hosts with Alaria marcianae (trematoda) mesocercariae.

Transmammary infection with Alaria marcianae mesocercariae was demonstrated using mice as model, paratenic hosts. Prenatal transmission was ruled out because neonates removed immediately postpartum from infected dams were never infected. Mesocercarial distribution in virgin females and in females examined immediately postpartum showed no marked preference for the mammary glands. In contrast, infection of neonates that were allowed to suckle on infected dams was absolute, and the number of mesocercariae in the mammary glands of postparturient dams that suckled their young was increased significantly. These experimental observations were coupled with other observations on paratenic hosts to outline the pathways open to mesocercariae in gravid hosts. The term amphiparatenic host is coined for those host species that are paratenic hosts as adults, but as juveniles can serve as definitive hosts.

Animals↗
PubMed1983

Migration of Alaria marcianae (Trematoda) in domestic cats.

The migration of Alaria marcianae was studied in domestic cats. Mesocercariae penetrated the stomach wall, entered the abdominal cavity, and penetrated the diaphragm within 3 hr. Direct penetration of the lungs via the thoracic cavity occurred within 6 hr. Also observed was a circulatory route to the lungs when mesocercariae were recovered from both the liver and the chambers of the heart. Upon entrance into the lungs, mesocercariae began to enlarge with sequential lappet formation, holdfast development, and penetration gland atrophy. By day 7, they were recognized as fully formed diplostomula. The diplostomula resided a minimum of 4 days in the lungs as they first appeared in the duodenum by day 11. Diplostomula were found in both the trachea and stomach, indicating that they reach the duodenum after being coughed up from the lungs and swallowed. Diplostomula recovered from the duodenum were indistinguishable morphologically from the most advanced lung forms. Maturation of the reproductive organs occurred in as little as 4 days as the first ovigerous specimens were seen on day 15. The bidirectional route to the lungs may be significant when viewed in light of the recent discovery of transmammarian transmission. If a hormonal stimulus is involved, it is conceivable that those mesocercariae in the circulatory system may be more readily influenced than those undergoing a somatic migration. This may account for why some larvae are diverted to the mammary glands in a pregnant mammal instead of the normal, maturative migration to the duodenum.

Animals↗
PubMed1981

Epidemiology of Alaria marcianae mesocercariae in Louisiana.

Natural infections of Alaria marcianae mesocercariae were detected in five amphibian, seven reptilian, and two mammalian species in Louisiana. Alligators were susceptible to experimental infections with mesocercariae. Natural infections were also found in the subcutaneous fat of raccoons and opossums. Examination of three gravid opossums showed a marked preference of the mesocercariae for the mammary glands, however, we were unable to find transmission of mesocercariae to any of the 27 young. Based on morphological, geographical, and host evidence we believe the etiological agent of the human infection reported by Beaver et al. (1977) to be A. marcianae. Our results emphasize the requirement for precautions when cleaning and eating game animals such as frogs, snakes, alligators, and raccoons.

Amphibians↗