Presence and recovery of Ascaridia dissimilis ova on the external shell surface of turkey eggs.

Ascaridia dissimilis, a roundworm in turkeys, has been noted with increased frequency in commercial turkeys. Because infected turkeys can shed A. dissimilis ova in their feces, the potential exists for the external surface of turkey eggshells to be contaminated with A. dissimilis ova. The objectives of this study were to determine the presence of and recover A. dissimilis ova on the external surface of the turkey egg. In Experiment 1, turkey eggs were collected from naturally infected flocks, and eggs were processed by a sodium hydroxide procedure to recover any A. dissimilis ova on the external egg surface. In Experiment 2, the external surface of the turkey eggs was inoculated with 116 A. dissimilis ova/g feces, and eggshells were sampled every 3 days until 28 days of incubation to assess the recovery of A. dissimilis ova from the eggshell. In Experiment 1, of the 36 eggs examined from a flock naturally infected with A. dissimilis, one egg had an A. dissimilis ovum on its external eggshell surface. Experiment 2 demonstrated that A. dissimilis ova can be recovered from the external egg surface after a 28-day incubation period in the incubator. Ova recovery declined from an average of 62 A. dissimilis ova/turkey egg at day 2 of incubation to an average of 3 A. dissimilis ova/turkey egg at day 28 of incubation.

Fecal shedding and antimicrobial susceptibility of selected bacterial pathogens and a survey of intestinal parasites in free-living waterfowl.

Free-living waterfowl residing in metropolitan parks in central Ohio were surveyed for the fecal shedding and antimicrobial susceptibility patterns of Campylobacter jejuni, Escherichia coli, Salmonella spp., and Pasteurella multocida. In addition, a survey for intestinal parasites was also conducted in these same waterfowl to determine parasite burdens in free-living waterfowl. Prevalences of 67%, 50%, and 0.2% of E. coli, C. jejuni, and Salmonella spp., respectively, were observed for all waterfowl species. Pasteurella multocida was not isolated from the sampled population. Salmonella java was isolated from one mallard duck. Statistically, there was a significantly higher E. coli isolation rate for mallard ducks than for Canada geese, but no difference was observed for C. jejuni isolation rates between waterfowl species. Antimicrobial susceptibility testing was conducted via the disk diffusion method and multidrug resistance was exhibited for penicillin G, lincomycin, vancomycin, erythromycin, and bacitracin. In addition, the prevalence of endoparasites in these sampled waterfowl ranged from 5% to 66%. Protozoan oocysts were most prevalent followed by nematode ova. No trematode or cestode ovum was recovered from this sampled population.

Experimental cyathostome challenge of ponies maintained with or without benefit of daily pyrantel tartrate feed additive: comparison of parasite burdens, immunity and colonic pathology.

Eighteen mixed-breed, naturally infected ponies ranging in age from 1 to 16 yr and four cyathostome-naïve ponies reared and maintained under parasite-free conditions ranging in age from 1 to 4 yr were used in this study. Naturally-infected ponies were treated with 1 dose of ivermectin (IVM) at 200 micrograms kg-1, followed by a 5-day regimen of oxibendazole (OBZ) at 20 mg kg-1 to remove existing cyathostome burdens; cyathostome-naïve control ponies were treated with IVM alone. The naturally infected ponies were matched on age and gender, then randomly assigned to one of three treatment groups of six animals per group; the four cyathostome-naïve ponies constituted a fourth group. Following OBZ treatment, Group 1 ponies were treated with pyrantel tartrate (PT) in their pelleted ration; the remaining ponies received only the pelleted ration. Beginning on experiment Day 3, a daily challenge infection of 10(4) mixed cyathostome larvae was administered orally to ponies of Group 1, Group 2 and the cyathostome-naïve controls. Group 3 ponies served as unchallenged controls to determine residual parasite burdens following IVM/OBZ treatment. Necropsy examinations were performed on three Group 3 ponies on Day 1; the remainder of the necropsy examinations began on Day 41. Cyathostome burdens were evaluated by recovery of larvae and adults from the luminal contents, by digestions of the intestinal mucosa, and by mural transillumination of full-thickness intestinal sections. Differences in postchallenge clinical responses were also compared. Necropsy examinations included comparisons of grossly visible inflammation of the large bowel, weights of biopsy specimens from each region, and histologic evaluations of these biopsies. Parasite recoveries at necropsy indicated a strong protective effect derived from daily PT treatment. Mean weights of intestinal biopsies corresponded with worm burdens, but histological evaluation did not reveal architectural or cellular changes to account for the increase in weight; therefore, edema was suspected. A strong age-related resistance to challenge infection was apparent in both the PT-treated and control groups by virtue of the lower mean worm burdens found in older ponies compared to younger ponies of the same treatment group; however, daily PT treatment of older ponies reduced the variability of their worm burdens to a uniformly low level. Comparisons of luminal and mucosal parasite burdens of age stratified nontreated controls further suggest that the age related resistance, which is acquired, targets increasing numbers of parasite stages as this resistance matures. Further, there is no evidence for an immune mediated acquisition of hypobiotic L3.

Dose response to ethanol-containing liquid diets for use in a murine model for studies of biological effects due to ethanol consumption.

Dose-response experiments were performed to establish an optimum concentration of ethanol (EtOH) in liquid diet formulations for use with a murine model (C57B1/6) of potential biological effects attributable to EtOH consumption. An optimum concentration was predetermined to be the highest EtOH concentration consumed by mice without resulting in a loss of body weight. Feeding trials were performed using EtOH concentrations that ranged from 25 to 36% ethanol-derived calories (EDC) during 7-day experiments, or 10 to 30% EDC fed during 21-day experiments. The parameters studied included body weight changes, diet consumptions, daily g EtOH kg-1 body weight, as well as differences in mononuclear cell numbers from the spleen, thymus, and bone marrow. Diet consumptions by the EtOH groups and pair-fed (PF) groups were monitored by weight rather than by volume. During either 7-day or 21-day trials, diet consumptions were lower by groups receiving diets of higher EtOH concentrations; however, daily EtOH intake was maximal by groups fed diets of 25% EDC in all experiments. These mice also gained weight, whereas mice maintained on 30% EDC did not gain weight, and mice maintained on diets of 33 or 36% EDC lost significant body weight. Body weight changes in PF groups were similar to their respective EtOH group. Changes in mononuclear cell numbers of the spleen and thymus paralleled the changes seen in body weights. In the 7-day trials, cell counts declined progressively in groups maintained on diets of high EDC (> or = 30% EDC) or their PF controls. From the 21-day trials, cell counts of both the 30% EDC group and their PF controls declined, compared with all other groups. Together, the conclusion drawn from these findings was that nutritional stress was principally responsible for the mononuclear cell depletions. This contradicts previous reports and highlights the need for strict attention to the pairfeeding paradigm to avoid masking a nutritional component of such studies through overfeeding of the PF controls. Liquid diets of 25% EDC were determined to be optimal for immunological studies using a murine model, because this concentration maximizes EtOH consumption and maintains body weight of the experimental animals.

Foals raised on pasture with or without daily pyrantel tartrate feed additive: comparison of parasite burdens and host responses following experimental challenge with large and small strongyle larvae.

Three groups of foals were raised under different management programs in this study: Group 1 (n = 6) and Group 2 (n = 6) were raised with their dams on pasture; Group 3 foals (n = 5) were raised under parasite-free conditions. Mares and foals of Group 1 received daily pyrantel tartrate (PT) treatment with their pelleted feed ration, whereas mares and foals of Groups 2 and 3 received only the pelleted ration. Pasture-reared foals were weaned and moved to a heavily contaminated pasture for 5 weeks. Group 1 foals continued to receive daily PT treatment whereas Group 2 foals received only the pelleted feed ration. Following this period, all foals were moved into box stalls. Half of each group was challenged with 10(3) Strongylus vulgaris infective third-stage larvae (L3), 5 x 10(3) Strongylus edentatus L3 and 10(5) mixed cyathostome L3; the remaining half served as unchallenged controls. Necropsy examinations were performed 6-week post-challenge for evaluation of parasite burdens and lesions. Daily PT treatment of Group 1 reduced the patent cyathostome infections of both mares and foals and was effective in reducing pasture burdens of infective larvae. Daily treatment of Group 1 foals during weaning continued to suppress EPG levels; however, it did not prevent large strongyle infections during the weaning period. Group 1 foals were more sensitive to challenge than Group 2 foals, which did not exhibit any post-challenge disturbances. Group 1 foals were equally susceptible to challenge as parasite-free foals.

Identification and characterization of a pyrantel pamoate resistant cyathostome population.

Three fecal egg count reduction assays (FECR) and one critical trial were performed to determine the efficacy of pyrantel pamoate (PP) at 6.6 mg base kg-1 on a well managed stud farm in Louisiana where a loss of efficacy was suspected. Efficacy of PP based on FECR varied from 25% in mares to 83% in yearlings. Second treatments with PP 2 weeks following an initial treatment failed to reduce eggs per gram (EPG). A critical trial was performed to determine the cyathostome species resistant to PP. Three strongyle-naive ponies which acquired infections on the farm were used for this purpose. Following treatment with PP at the recommended dose, 11 species of cyathostomes remained in the intestine of the tracer ponies. Reduced efficacies (62%-88%) were noted for seven species. Resistance to oxibendazole (OBZ), which was > 90% effective on this farm in 1982, was also evaluated by FECR and found to exist. The results of one experiment indicate that dual resistance of parasites to PP and OBZ also exists.

Comparison of moxidectin oral gel and ivermectin oral paste against a spectrum of internal parasites of ponies with special attention to encysted cyathostome larvae.

Two dosages of moxidectin oral gel were evaluated and compared to a therapeutic dose of ivermectin oral paste in the control of a spectrum of gastrointestinal parasites of ponies naturally infected in southern Louisiana or Mississippi. Thirty-two mixed-breed ponies ranging in age from one to 21 years were used in this controlled test. Eight weeks prior to the experiment, ponies grazing on contaminated pasture were moved to a paddock and fed a pelleted ration, thus reducing or eliminating the potential for additional infection and ensuring the existence of a population of encysted larvae. Ponies were then allocated to replicates of four animals based on values of fecal strongyle egg counts and percent strongyle larvae composition determined from Baermann sedimentations of fecal cultures. Members of replicates were allocated to one of four treatment groups: moxidectin oral gel administered at 300 micrograms kg-1 body weight, moxidectin oral gel at 400 micrograms kg-1, the oral gel vehicle as negative control, and ivermectin oral paste at 200 micrograms kg-1. Prior to treatment, ponies were confined in pairs to covered concrete runs by treatment group. Two weeks following treatment, necropsy examinations of all animals were performed. Parasites were recovered from the lumen of the stomach, the intestinal tract, the cranial mesenteric artery and its major branches, the peritoneal body wall and from pepsin digests of mucosal scrapings taken from the cecum and large colon. Encysted cyathostome larval burdens were also compared using mural transillumination of segments of the large colon for visualization of the encysted forms. Control ponies were not uniformly infected with the spectrum of parasites; however, moxidectin, at either dosage, compared favorably with ivermectin in the control of the adults of Strongylus vulgaris, Strongylus edentatus, Triodontophorus spp., Oesophagodontus robustus, Trichostrongylus axei, Oxyuris equi, Parascaris equorum, Habronema muscae, as well as both the adult and larval Cyathostominae recovered from the lumen. Moxidectin also appears as efficacious as ivermectin against migrating large strongyle larvae at the two weeks post-treatment evaluation. Moxidectin demonstrated a trend towards greater efficacy against encysted cyathostome larvae than a therapeutic dosage of ivermectin, but this difference was not statistically significant. Moxidectin was less effective than ivermectin against Gasterophilus intestinalis and was equally ineffective as ivermectin against Anoplocephala perfoliata.

Dose titration of moxidectin oral gel against migrating Strongylus vulgaris and Parascaris equorum larvae in pony foals.

Moxidectin was tested for efficacy in ponies against experimental infections of 56 day Strongylus vulgaris larvae and 11 day Parascaris equorum larvae. Three dosages of moxidectin were tested: 300 micrograms per kg live body weight, 400 micrograms per kg, and 500 micrograms per kg, and the vehicle served as control. Ponies were first infected with 600 S. vulgaris third-stage larvae (L3) on Experiment Day 0 and then with 3000 embryonated P. equorum eggs on Day 45. Moxidectin treatments were administered on Day 56 and necropsy examinations were performed on Day 91. Strongylus vulgaris fourth-stage (L4) and fifth-stage (L5) larvae were recovered at necropsy from the control ponies, in dissections of the cranial mesenteric artery and its branches (L4 and L5), and recovered from nodules in the wall of the cecum and ventral colon (L5). Parascaris equorum larvae were recovered from the small intestine of control ponies. Moxidectin was highly efficacious against S. vulgaris L4 and L5 at all three doses tested (99.6-100%), and appeared to be equally efficacious against P. equorum larvae (100%); however, control ponies had low levels of P. equorum infections compared to previous experimental infections performed using identical methods. This suggests that the prior S. vulgaris infection on Day 0 may have influenced the subsequent experimental P. equorum infection on Day 45 and contributed to the lower recovery.

Dose titration of moxidectin oral gel against gastrointestinal parasites of ponies.

Moxidectin was tested as an oral gel formulation during a controlled test performed to evaluate dosages against equine gastrointestinal parasites. Four groups of ten ponies were used. Ponies ranged from 1 to 20 years of age and were naturally infected in southern Louisiana or Mississippi. Fecal exams and fecal cultures were performed on all ponies to determine the strongyle egg counts and the percent distributions of large and small strongyles. Following these determinations, ponies were allocated to replicates of four ponies to provide an even distribution of strongyle infection, age, weight and gender. Members of each replicate were then randomly assigned to one of four treatment groups. The doses tested were 300, 400 and 500 micrograms kg-1 body weight. The oral gel vehicle alone served as control. Treatments were administered behind the tongue and the ponies were observed continuously for 4 h for any adverse reactions; thereafter, ponies were observed at least twice daily. Necropsy examinations were performed 14 days post-treatment for the recovery and identification of any parasites present. Moxidectin, at all doses tested, was 100% efficacious against adults of Strongylus vulgaris, Strongylus edentatus, Triodontophorus spp. and 22 species of small strongyles. Moxidectin was also 100% efficacious against larvae of Strongylus edentatus and Oxyuris equi, greater than 94% efficacious against Strongylus vulgaris larvae and Oxyuris equi adults at 14 days post-treatment. Moxidectin proved highly efficacious against luminal small strongyle larvae (> 99.9% against L4 and > 92% against L3) and moxidectin demonstrated some efficacy against encysted small strongyle larvae as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of moxidectin oral gel against Onchocerca cervicalis microfilariae.

During a series of dose-titration experiments designed to evaluate the efficacy of moxidectin oral gel against equine gastrointestinal parasites, infection with Onchocerca cervicalis was diagnosed in 25 of 82 ponies prior to treatment. Microfilariae were identified in full-thickness skin biopsies taken from the ventral midline. Treatment with moxidectin in single doses of 300, 400, or 500 micrograms/kg of body weight was 100% effective in eliminating microfilariae from 20 skin biopsies taken 14 days posttreatment, whereas 5 microfilaria-positive ponies in 2 control groups remained positive following placebo treatment. No adverse reaction was seen in any pony following treatment with moxidectin or the vehicle control.

Experimental immunization of ponies with Strongylus vulgaris radiation-attenuated larvae or crude soluble somatic extracts from larval or adult stages.

Protection from Strongylus vulgaris infection through immunization with radiation-attenuated third-stage larvae (L3) or crude soluble homogenates from larval or adult stages was examined. Yearling ponies raised parasite-free were divided into 3 immunization groups: radiation-attenuated L3; soluble adult somatic extracts; larval somatic extracts with excretory/secretory products (E/S) from in vitro culture; and 1 medium control group. Ponies were immunized twice; attenuated larvae were administered orally and somatic extracts or controls injected intramuscularly with adjuvant. Approximately 6 wk following the second immunization, all ponies were challenged. Necrospy examinations were performed 6 wk following challenge. Irradiated larvae recipients had the fewest postchallenge clinical signs and lesions and were 91% protected from infection determined by larval recoveries from arterial dissections. Soluble antigen recipients and controls had similar larval recoveries and thus equal susceptibility to challenge. Soluble antigen recipients had more severe clinical signs and lesions than controls, suggesting that parenteral immunization exacerbated postchallenge inflammatory responses. Protection by immunization with irradiated larvae was associated with an anamnestic eosinophilia and postimmunization antibody recognition of S. vulgaris L3 surface antigens. Histologic staining of eosinophils within tissues of this group suggested that this immunization induced a cytophilic antibody response that facilitated degranulation.