Biomedical subjects

L R McDougald

Publications and source records attributed to L R McDougald.

At least 19 recordsLinked to original sources

PubMed2006

Histomonas meleagridis in chickens: attempted transmission in the absence of vectors.

The progress and transmission of blackhead disease in chickens was studied in battery cages and floor pens in the absence of vectors. Two-week-old chicks were inoculated intracloacally with Histomonas meleagridis and allowed to commingle with others in floor pens. There was no confirmed transmission of blackhead to other birds in the pen, whether stocked at 10% or 25% with infected birds. A second experiment evaluated the effects of feed restriction of chickens on spread of blackhead within floor pens. Inoculated seeder birds had severe cecal lesions of blackhead at necropsy, regardless of feed restriction. Uninoculated birds did not develop lesions by the time of necropsy at 42 days of age, regardless of whether full-fed or limited by skip-day feeding. Chickens inoculated intracloacally with H. meleagridis and placed in battery cages became infected and had cecal lesions of blackhead, but few liver lesions. Chickens allowed to commingle with the inoculated birds in batteries had no lesions of histomoniasis at necropsy 2 wk postinoculation. Coccidial oocysts from turkeys (Eimeria adenoeides) were inoculated along with H. meleagridis from cultures to test the effects of sporozoite penetration in the ceca on progress of blackhead disease. Histomoniasis was not worsened by the interaction with sporozoites, as shown by unchanged severity of cecal lesions, the number of birds showing liver lesions, or the overall number of positive birds. Overall, blackhead infections showed no inclination to spread from bird to bird under conditions of these studies, in contrast to what has been reported for turkeys. These results suggest that the dynamics of blackhead transmission in chickens differs significantly from that of turkeys, where transmission from bird to bird is rapid and effective in the absence of vectors.

Animal Feed↗

PubMed2005

Blackhead disease in turkeys: direct transmission of Histomonas meleagridis from bird to bird in a laboratory model.

The spread of Histomonas meleagridis infections through groups of turkeys in the absence of the cecal worm vector (Heterakis gallinarum) was studied in a battery cage model. Battery-reared poults were exposed at 2 wk of age by commingling with infected birds into cages that had the floor lined with paper. One treatment received no exposure, whereas other birds were commingled with two, three, or four birds/cage (25%, 37.5%, or 50%) inoculated per cloaca with cultured H. meleagridis (200,000/bird). Inoculated birds died at 7-13 days postinoculation (DPI) showing typical liver and cecal lesions of histomoniasis. By 14 DPI, 87.5% of the directly inoculated birds died or had severe lesions of histomoniasis. Turkeys commingled with two, three, or four infected birds became infected at the rate of 72%, 80%, or 75%, respectively. In another experiment, two birds/cage (25%) were inoculated with Histomonas from culture and allowed to commingle with other birds for 1, 2, 3, or 4 days. Two of 12 (16.7%) birds had minor cecal lesions after contact with inoculated birds for 1 day, but 87.5%-100% became infected if inoculated birds remained in the cage for 2-4 days. Contemporaneous inoculation with cecal coccidia (Eimeria adenoeides) as a predisposing factor in blackhead infections was studied using the model. Turkey poults directly inoculated with Histomonas were allowed to commingle for 5 days with uninoculated birds that had received inoculation with 0, 10(3), or 10(4) sporulated oocysts. The coccidian infection appeared to interfere with transmission of blackhead infection by 7 DPI, as suggested by lessened severity of cecal lesions and a lower percentage of infected birds. These studies confirm that histomoniasis is transmitted readily from directly exposed young turkeys to others in the absence of the cecal worm vector, and that this phenomenon can be reproduced in battery cages as an experimental model.

Animals↗

PubMed2005

Blackhead disease (histomoniasis) in poultry: a critical review.

After its discovery in 1893 in Rhode Island, blackhead disease was reported across the continent and soon in many other countries. It decimated the turkey industry in New England and followed production like a faithful shadow. Blackhead disease causes high mortality in turkeys, sometimes approaching 100% of a flock. In chickens, the mortality may be 10%-20% with high morbidity, although many outbreaks pass unnoticed. Early workers identified Histomonas meleagridis, a protozoan related to Entamoeba histolytica, Giardia lamblia, and Trichomonas, as the causative agent. Like many other parasites, its life cycle is complex, involving as an intermediate host, the common cecal worm Heterakis gallinarum. The necessity for bacteria for Histomonas to become virulent in the turkey and chicken, notably Escherichia coli, Bacillus subtilis, and Clostridium spp., was discovered by research in gnotobiotic birds. Changes in management brought the disease under control, although it remained the first cause of mortality in turkeys until modern antihistomonal products were developed after WWII. The ban of nitroimidazole products in the United States and Europe was followed by an upsurge in reported cases in turkeys and chickens. Immunization is not an option for prevention, as birds do not reliably become resistant to reinfection after suffering a primary exposure. Recent research demonstrated that histomoniasis could spread rapidly through a flock of turkeys by direct contact, probably involving the phenomenon of cloacal drinking. Direct transmission was not demonstrated for chickens, stressing dependence on H. gallinarum as the source of infection. The lack of suitable treatment drugs or vaccines emphasizes the importance of prevention by worm control and management.

Animals↗

PubMed2004

The efficacy of some drugs with known antiprotozoal activity against Histomonas meleagridis in chickens.

Nine drugs with known or suspected antiprotozoal activity were tested in vitro, and in vivo for activity against Histomonas meleagridis. The nitroimidazoles dimetridazole, metronidazole, ornidazole, and tinidazole suppressed growth of H. meleagridis in vitro at 10 microg/ml or higher. Paromomycin sulfate, and carbadox were weakly effective at high levels. Quinolinol, mebendazole, diloxanide furoate, and albendazole had no demonstrable efficacy in vitro. Drugs showing some activity in vitro were tested in young chickens inoculated intracloacally with 2 x 10(5) H. meleagridis/bird. Dimetridazole, metronidazole, ornidazole, and tinidazole were highly effective at 200 ppm in feed. Paromomycin sulfate, and carbadox were ineffective in vivo, with no improvement in liver or cecal lesion scores compared to that of infected controls. Thus, the only new entities with efficacy against blackhead disease in vivo were nitroimidazoles, related to the positive control dimetridazole.

Animals↗

PubMed2004

Infection of turkeys with Histomonas meleagridis by the cloacal drop method.

The infection of turkeys with Histomonas meleagridis was attempted in the absence of its normal vector Heterakis gallinarum, using several experimental techniques. Battery-reared poults were inoculated at 2 wk of age with histomonads cultured in vitro, by several routes, including (a) per os (PO), (b) intradoacal (CI), and (c) cloacal drop (CD). Feed restriction was also studied as a predisposing factor. Intracloacal inoculation (CI) consistently produced severe infections in all experiments. In several experiments, turkeys did not become infected after inoculation PO with 1 x 10(5) cultured histomonads. Feed restriction prior to inoculation did not make turkeys susceptible to infection inoculated PO. However, when liquid cultures containing histomonads were applied to the vent (CD) and the dorsal lip stimulated to initiate cloacal drinking, the histomonads were taken into the cloaca and transported to the ceca by retrograde peristalsis. Heavy infections were produced by this method, with severe liver and cecal lesions recorded when birds were necropsied 12 days later. These results suggest that CD may provide ready entry into the lower intestinal tract for these parasites and may facilitate spread of infection through flocks.

Animals↗

PubMed2002

Lectin-binding by sporozoites of Elmeria tenella.

Sporozoites of Eimeria tenella were reacted in vitro with 19 different lectins characterized with a variety of carbohydrate-binding properties. Nine lectins caused sporozoite agglutination, which was inhibited by the specific carbohydrates mannose, sialic acid, melibiose, D-galactose, or D-galNAc. When intact live or fixed whole sporozoites were reacted with fluorescein isothiocyanate-conjugated lectins, another nine lectins bound to sporozoites, giving weak to strong fluorescence but not agglutination. Of these, all nine lectins bound to surface sites, but four also bound to the refractile body. Two of the agglutinating lectins also bound to intracellular organelles of air-dried sporozoites. SDS-PAGE analysis showed that biotinylated lectins bound a wide variety of parasite proteins. Lectins with similar carbohydrate specificities had some similarity in binding patterns of parasite proteins, as well as marked differences. In a few cases lectins with different carbohydrate specificities bound common protein bands. Only one lectin (Dolichos biflorus) showed no evidence of binding to whole sporozoites, organelles, or proteins.

Acetylgalactosamine↗

PubMed2001

Cell membrane labeling of Eimeria tenella sporozoites with the fluorescent dye PKH-67 GL for tracking parasite-host interactions.

The fluorescent cell linker dye PKH-67 GL was used as a vital stain for sporozoites of Eimeria tenella for tests on viability, invasion of cultured primary chick kidney cells, flow cytometric analysis and fluorescence microscopy. The effect of PKH-67 GL on sporozoites was tested at a range of concentrations of dye and sporozoites. In flow cytometric analysis, 0.5-40x10(-6) M of PKH-67 GL labeled sporozoites to some degree, with the percentage of labeled sporozoites increasing with higher dye concentrations. The optimum concentration was 2x10(-6) M, allowing easy observation by fluorescence microscopy. Morphological changes in the sporozoite at concentrations greater than 5x10(-6) M were accompanied by loss of viability according to a propidium iodide inclusion assay. Sporozoite penetration of primary chick kidney cells was unaffected by the optimal level of 2x10(-6) M, allowing observation of intracellular activities. Overall, the cell linker dye greatly facilitated observation of E. tenella in vitro and in flow cytometric analysis.

Animals↗

PubMed1998

Residual activity of anticoccidial drugs in chickens after withdrawal of medicated feeds.

Seven anticoccidial drugs commonly used in poultry (diclazuri), monensin, salinomycin, halofuginone, nicarbazin, robenidine, amprolium, and lasalocid) were tested for residual activity after withdrawal. In each test, the products were given at the recommended level to cages of 10 broiler chickens. Oral inoculation with coccidia was given after withdrawal of medication. Birds pretreated with 1 ppm of diclazuril and inoculated with Eimeria tenella after drug withdrawal had normal weight gain and very low lesion scores. Residual activity depleted gradually over several days, as shown by higher lesion scores when medication was withdrawn for up to 3 days before inoculation. Similar results were observed when young birds were inoculated with a mixture of E. tenella, E. maxima and E. acervulina, and also when birds were given diclazuril to market weight (6 weeks of age) and inoculated with a mixture of six species of Eiméria (The above species plus E. brunetti, E. mitis, and E. necatrix) after withdrawal of medication for 2 days. In contrast, there was no evidence of residual anticoccidial activity with nicarbazin, halofuginone, lasalocid, amprolium, salinomycin or monensin. Overall, the residual activity was unique to diclazuril.

Amprolium↗

PubMed1998

Biological effects of gamma-irradiation on laboratory and field isolates of Eimeria tenella (Protozoa; Coccidia).

Sporulated oocysts of a field strain (FS-111) and a laboratory strain (WIS) of Eimeria tenella were exposed to 0, 50, 100, 150, or 200 Gy of gamma-radiation from a 60Co source. Irradiated oocysts of WIS and FS-111 were not significantly more fragile after irradiation as shown by the release of sporocysts after 5-105 s of vortex agitation with glass beads. Excystation was normal in both strains after treatment of the sporocysts with trypsin and sodium taurodeoxycholate, even in groups exposed to 200 Gy of radiation. Sporozoite release from irradiated sporocysts was more rapid than that from unirradiated sporocysts, primarily because of a shorter lag phase during the first 30 min. Irradiated sporozoites were slower to parasitize cultured chick kidney cells than were control sporozoites (4 h postinoculation), but after 24 h there was no significant difference (P < 0.05) between irradiated and control groups except for the WIS treated with 200 Gy. After 48 h, developing schizonts were reduced by 77-94% on exposure to 50-200 Gy. Strain FS-111 did not develop as well as WIS in vitro, but the effect of irradiation was similar. When irradiated oocysts of WIS or FS-111 were inoculated into chickens the prepatent period was unaffected, but fewer oocysts were produced, lesion scores were lower, and the weight gain was less strongly affected in proportion to the doses of radiation. These results suggest that the effects of radiation damage were largely confined to the mechanism of nuclear and cellular reproduction rather than other physiological processes.

Animals↗

PubMed1998

Intestinal protozoa important to poultry.

Parasites of two groups are important in poultry, the coccidia and the mastiogophora (flagellates) (Table 1). Most of the Coccidia in poultry are in the genus Eimeria, but a few species of Isospora, Cryptosporidium, and Sarcosporidia are represented. The Eimeria are best known, with seven important species recognized in chickens and several others in turkeys. Diagnosis of coccidiosis is by recognition of classic signs and lesions, by gross examination, and can be aided by microscopic examination of feces and intestinal contents. Control of coccidiosis is by preventive use of anticoccidials and by immunization. Cryptosporidium are common in poultry but little is known of their importance, except for the occasional outbreak of respiratory cryptosporidiosis in turkey poults. Of the flagellates, Histomonas meleagridis is the best known. Infections in turkeys may cause near 100% mortality, but outbreaks in chickens are more often marked by morbidity and subsequent recovery. Recent outbreaks in broiler breeder pullets caused excessive losses from mortality (5 to 20%) culling, and overall poor flock performance. Histomonas organisms are carried by eggs of the cecal worm Heterakis gallinarum enabling them to survive for long periods in soil as a source of infection. In the U.S. there are no products available for treatment of blackhead. Preventive use of anthelminthics to destroy the cecal worm carrier show some promise in reducing exposure.

Animals↗

PubMed1997

Clostridial population and the intestinal lesions in chickens infected with Clostridium perfringens and Eimeria necatrix.

Chickens infected with Clostridium perfringens and Eimeria necatrix were examined bacteriologically and pathologically. When chickens were inoculated with 1.0 x 10(8) C. perfringens and/or 2 x 10(4) E. necatrix sporulated oocysts, populations of C. perfringens in the intestinal contents were examined on 3, 5 and 7 days after E. necatrix inoculation. In both groups infected with E. necatrix, the mean clostridial counts were significantly higher than those of uninfected controls. The concurrent infection had no enhancing effects on increasing the clostridial population more than E. necatrix-alone. Mortality of 4-day-old chickens inoculated on 5 consecutive days with C.perfringens after receiving E. necatrix was higher than those of chickens inoculated with the both organisms. However, intestinal lesions of the concurrently infected group were not different from E. necatrix-alone-infected group on 5 and 7 days after the coccidial infection. When chickens received a large dose (1.5 x 10(9)) of C. perfringens after the inoculation with E. necatrix, edema in the duodenum through jejunum were observed early after the bacterial broth inoculation. These results suggest that the concurrent infection with E. necatrix and C. perfringens increases clostridial population in the intestine of the chickens and has synergic effects on mortality and edema in the upper intestine.

Animals↗

PubMed1995

Efficacy of semduramicin and salinomycin against Eimeria maxima in a laboratory test using two levels of oocyst inocula.

The anticoccidial efficacies of semduramicin and salinomycin against five field isolates of Eimeria maxima in broiler chickens were compared in five trials. Uninfected, unmedicated; infected, unmedicated; infected, 25 ppm semduramicin; and infected, 66 ppm salinomycin treatments were assigned to battery cages using a randomized, complete block design. Two levels of inocula, 10(3) and 10(4) oocysts per bird, were used in each trial in the infected treatments, creating a total of seven treatments per trial. Each treatment consisted of five replicate cages of eight broiler cockerels each. Medications were given in the feed continuously for 7 d beginning 24 h before inoculation. Response variables measured included bird weight gain by pen, feed consumption, feed conversion, plasma carotenoid concentrations, and coccidial lesion score. By using two levels of inocula it was demonstrated that the efficacy of each anticoccidial was equal to or greater than 90% in controlling these E. maxima isolates. It was also demonstrated that 25 ppm semduramicin was more efficacious than 66 ppm salinomycin based on improvements in weight gain, feed conversion, plasma carotenoid concentrations, and coccidial lesion control.

Animals↗

PubMed1995

Flow cytometric analysis of the response of Eimeria tenella (Coccidia) sporozoites to coccidiocidal effects of ionophores.

Fluorescein diacetate (FDA) and propidium iodide (PI) were used as indicators of membrane integrity after Eimeria tenella sporozoites were treated with polyether ionophores. Flow cytometry was used to quantitate the structural and functional effects based on red or green fluorescence and shape index of the sporozoites. Two field isolates (FS119 and FS139) were essentially resistant to polyether ionophores administered under practical conditions, whereas a laboratory strain was considered sensitive. The shape of sporozoites changed after treatment with ionophores, and this could be detected by flow cytometry. Green-fluorescing cells declined in number as the membranes were compromised by ionophore treatment. Red-fluorescing cells increased as the compromised membranes allowed entry of PI to bind with the nucleic acids. These effects were generally slower to develop in ionophore-tolerant field isolates compared with the sensitive laboratory strain. The effect of lasalocid on FDA and PI uptake, change in shape of the sporozoites, and lysis of sporozoites was more rapid than that of monensin or salinomycin. The 2 field isolates responded at different rates to salinomycin and monensin. Flow cytometry was a sensitive and accurate instrument for analysis of the effects of ionophores on sensitive and resistant lines of coccidia.

Animals↗

PubMed1994

Amplification of ionophore resistance in a field strain of Eimeria tenella by treating free sporozoites with monensin in vitro.

Monensin resistance in a field strain of Eimeria tenella (FS139) was successfully amplified by an in vitro method. Sporozoites of parent FS139, designated as FS139(0), were treated with monensin at 5 micrograms ml-1 before inoculation into chickens. Oocysts developing from these drug-treated sporozoites were designated FS139(5). Sporozoites of FS139(5) were then treated with a higher level of monensin (25 micrograms ml-1), which produced another line called FS139(25). Sporozoites of FS139(25) received a monensin treatment of 100 micrograms ml-1 which yielded line FS139(100). After one passage in chickens, sporozoites of FS139(0), FS139(25) and FS139(100) were treated with either 0, 1, 25, or 100 micrograms ml-1 of monensin and inoculated into chicken primary kidney cell cultures to observe sporozoite invasion rates and development of first generation schizonts. Data on invasion rates and development of schizonts showed that FS139(100) was the most drug-resistant line while FS139(25) was the second most resistant line compared with the parent line FS139(0). These in vitro treatment techniques could be used to develop resistant coccidia for laboratory study of the physiological mechanisms of resistance.

Animals↗

PubMed1994

Simple method to purify chicken immunoglobulin G.

A new method for purifying IgG was adapted for use with chicken serum. Chicken serum was mixed with caprylic acid, precipitated with ammonium sulfate, and dialyzed against PBS. Analysis by SDS-PAGE and Western blot confirmed successful purification of chicken IgG. Large quantities of highly purified IgG were easily obtainable for use in immunological investigations or for labeling. This technique is rapid, inexpensive, and simpler to perform than traditional ion exchange or gel filtration chromatography.

Ammonium Sulfate↗

PubMed1994

Peptides associated with monensin resistance in sporozoites of Eimeria tenella (Coccidia).

Resistance to monensin in the sporozoites of a laboratory strain (WIS) of Eimeria tenella was amplified by treating free sporozoites with increased monensin levels in vitro, followed by propagation of these treated sporozoites in chickens. The parent strain of WIS and its subsequent lines developed from the treatment of monensin at 1, 5, or 25 micrograms/ml were designated as WIS(0), WIS(1), WIS(5), or WIS(25), respectively. The penetration rate of sporozoites into primary chicken kidney cell cultures showed that the sensitivity of sporozoites to the treatment of monensin at 1 and 5 micrograms/ml was significantly reduced in the WIS(25) line in comparison with the WIS(0) line. When native polyacrylamide gel electrophoresis (PAGE) was conducted, a change in the relative mobility of a protein band was found in the protein samples of these coccidial lines. Sodium dodecyl sulfate PAGE revealed that 2 peptides with molecular weights of approximately 50.0 and 31.4 kDa were present in the sporozoites of resistant lines but undetectable in their WIS-parent sporozoites. Derivation of the resistant lines from a drug-sensitive parent line gave strong support to a link between the appearance of the peptides and resistance to ionophores in this strain of E. tenella.

Animals↗

PubMed1993

Variant proteins associated with ionophore resistance in sporozoites of Eimeria tenella (Coccidia).

Protein samples prepared from sporozoites of two ionophore-sensitive strains (WIS and Penn St) and three resistant strains (FS139, FS459, and FS462) of Eimeria tenella were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), native polyacrylamide gel electrophoresis (native PAGE), or two-dimensional electrophoresis with native PAGE and SDS-PAGE. Variant proteins that might be associated with ionophore resistance were observed in resistant field strains on native PAGE. When two-dimensional electrophoresis was conducted, four over-expressed peptides with approximate molecular weights of 97, 71, 70, and 50 kDa were observed in the FS139 field strain in comparison with the WIS laboratory strain.

Animals↗

PubMed1992

Influence of coccidiosis on Salmonella colonization in broiler chickens under floor-pen conditions.

The influence of coccidiosis on colonization of Salmonella typhimurium in broiler chickens under floor pen conditions was studied by semiquantitative methods. Chickens of two groups, unmedicated and medicated with nicarbazin (125 ppm via the feed), were exposed to three species of Eimeria (Eimeria tenella, Eimeria maxima, and Eimeria acervulina) at 2, 3, and 4 wk of age and given S. typhimurium in the feed 2 days later. Salmonella typhimurium was isolated most often (100%) from ceca of chickens exposed at 3 wk of age. Birds in the unmedicated group were positive for S. typhimurium at a higher rate than those in the medicated group. Salmonella typhimurium was detected in livers only in a few unmedicated birds.

Animals↗