The B1 strain of Newcastle disease virus (NDV-B1), which is nonpathogenic for newly hatched chickens, killed embryos when it was used to inoculate chicken eggs at embryonation day 18. Treatment of NDV-B1 with an alkylating agent, ethylmethane sulfonate (EMS) markedly reduced the pathogenicity of the virus for 18-day-old chicken embryos. Eggs inoculated with the modified virus (NDV-B1-EMS) hatched, and the virus was isolated from lungs and spleen of 1-day-old chickens. The hatched chickens developed antibody to NDV and were protected against challenge exposure (at 4 weeks of age) with a highly virulent GB-Texas strain of NDV. Presence of maternal antibody to NDV in embryonating eggs did not influence the protective ability of NDV-B1-EMS, which also induced protective immunity when administered to 4-week-old chickens. The 50% protective dose of NDV-B1-EMS in maternal antibody-negative and -positive embryos was calculated to be 10.77 and 17.70 embryo 50% lethal doses, respectively. Results of the study indicated that NDV-B1-EMS may be used as an embryo vaccine to protect chickens against Newcastle disease.

Reference strains for Haemophilus parasuis serovars 1 to 7 were examined for virulence by inoculation of guinea pigs. Guinea pig response to intraperitoneal inoculation was similar for the 7 reference strains. However, apparent differences in virulence were detected after intratracheal inoculation. Cells of the reference strains for serovars 1 and 5 were most invasive, causing moribundity or death at higher doses and a persistent septicemia at lower doses. Haemophilus parasuis could be isolated from respiratory and systemic sites; purulent bronchopneumonia, pericarditis, and pleuritis were apparent in infected guinea pigs. Inoculation of cells of the reference strains for serovars 2 and 6 also resulted in bronchopneumonia and moribundity or death in some guinea pigs; however, reisolation of H parasuis and microscopic lesions at necropsy were less pronounced than those observed with serovars 1 and 5. Inoculation of cells of serovars 3, 4, and 7 induced only transient clinical signs and minimal evidence of H parasuis infection at necropsy. The data from intratracheal inoculation of guinea pigs are similar to data from other investigations in swine, indicating differences in the pathogenic potential of H parasuis strains. Thus, guinea pigs may be useful as a laboratory animal model for examining cellular factors associated with virulence and immunogenicity of H parasuis.

A study for about a 30-month period was done to compare strongyle control programs, using per os treatments of ivermectin (IVE) paste exclusively or alternation of 4 antiparasitic paste compounds: IVE, oxfendazole (OFZ), oxibendazole (OBZ), or pyrantel pamoate (PRT). Every 8 weeks, 1 group of horses (barn C; n = 14 to 16) was given IVE paste exclusively, and a second group (barn E; n = 16) was given the 4 antiparasitic pastes on an alternating schedule. Worm eggs and larvae per gram of feces (epg and lpg, respectively) values were determined every 2 weeks during the investigation. This study in grazing horses (mares and fillies), naturally infected with internal parasites, was conducted during the period between Oct 22, 1987 and Feb 8, 1990, with an additional observation on Mar 28, 1990. For barn-C horses, treated exclusively with IVE (200 micrograms/kg of body weight) 14 times, 2-week posttreatment mean strongyle epg and lpg (small strongyle) values were reduced 99 to 100%. Mean strongyle epg and lpg (small strongyle) values for each 2-week sample period remained low (< 20) throughout the study period, except for 1 moderate transient increase in July 1988. For the entire study period, the aggregate mean strongyle epg value was 12 and the lpg value was 6. Two-week posttreatment mean strongyle epg and lpg (small strongyle) values for barn-E horses, treated alternately with therapeutic (approx) dosage of IVE (200 micrograms/kg, 4 times), OFZ (10 mg/kg; 5 times), OBZ (10 mg/kg; 4 times), or PRT (6.6 mg base/kg; 2 times), varied within and between compounds. Posttreatment (2-week) mean epg values were reduced 100% by IVE, 0 to 100% by OFZ, 74 to 100% by OBZ, and 92 to 100% by PRT. Mean small strongyle lpg values at 2 weeks after treatment indicated reduction of: 100% for IVE, 0 to 76% for OFZ, 43 to 100% for OBZ, and 97 to 100% for PRT. For the entire study period, the aggregate mean strongyle epg value was 54 and the lpg value was 64. The epg and lpg reduction values for the 2 benzimidazoles indicated an increase in the benzimidazole-resistant segment of small strongyles. Fecal cultures for horses in both groups contained larvae of large strongyles (Strongylus vulgaris and S edentatus) only at the time of initial treatment. Treatment program evaluations included necropsy of 9 foals (56 to 203 days old), 7 born to barn-C mares and 2 born to barn-E mares. Generally, low numbers of bots (Gasterophilus intestinalis) and Habronema muscae were found in foals of both groups. Intestinal stages of immature and mature ascarids (Parascaris equorum) were also found in foals born to both groups of mares. Mature pinworms (Oxyuris equi) were found in 1 barn-C foal. Only barn-E foals had Strongyloides westeri. Small strongyles were detected in foals of both groups, up to several thousand in some. The latter finding indicates, in particular, that although barn-C mares had low small strongyle epg and lpg values throughout the study, eggs and larvae built up on pasture in sufficiently high numbers for major transmission to foals born there. Small strongyles in foals were composed of 3 genera and 10 species for barn-C foals and of 3 genera and 8 species for barn-E foals. Seasonal transmission of parasites also was observed.

The hemolytic effect of onion consumption in dogs with hereditary high erythrocyte reduced glutathione and potassium concentrations (designated HK dogs) was compared with that in clinically normal dogs. Twelve hours after oral administration of boiled onions (200 g/dog), hemoglobin concentration decreased to 84.4% of the initial value in HK dogs; it decreased only to 90.5% in clinically normal dogs. At 24 hours, methemoglobin concentration was significantly (P < 0.05) higher in HK dogs than in clinically normal dogs. The concentration of erythrocyte oxidized glutathione increased about fivefold at 10 hours in HK dogs, whereas it did not change during the experimental period in clinically normal dogs. In addition, at 12 hours, the proportion of erythrocytes containing Heinz bodies increased to 24.4% in HK dogs, but increased only to 1.2% in clinically normal dogs. Thus, results indicated that HK dogs were more susceptible to the oxidant action of onions than were clinically normal dogs.

Isoelectric focusing was performed on the soluble proteins of whole-body and excretory-secretory products (ESP) of Fasciola hepatica and Fascioloides magna. Adult F hepatica flukes were recovered from experimentally infected sheep and ESP obtained from the flukes; portions of liver were cut and frozen at -70 C. Fascioloides magna adults were collected from naturally infected white-tailed deer and ESP obtained; portions of liver were collected from noninfected white-tailed deer. Adult flukes and their host tissues were homogenized and centrifuged; protein concentrations with their ESP were determined and adjusted to < 2.50 mg/ml. Seven ESP samples from F hepatica and 1 from Fascioloides magna were subjected to isoelectric focusing with the 2 species of fluke and their respective host liver homogenates. After separation, gels were stained with silver and scanned on a laser densitometer. Protein banding patterns of the 2 species of flukes were dissimilar. In the pH range of 3.5 to 9.6, the body protein had approximately 30 peaks and ESP about 23 peaks in both species. Overall banding patterns of the body protein and ESP of both species were distinct from those of respective host tissues. Of the peaks reported as dominant, 3 of the body protein and 2 of ESP were shared between the 2 species. Fascioloides magna had more dominant peaks than F hepatica. This technique of soluble protein isoelectric focusing is simple and reproducible, and the 2 fluke species can easily be differentiated by this technique, as well as by morphologic characteristics.

Although cats are less susceptible to infection with Dirofilaria immitis than are dogs, the possibility of severe consequences from infection or adulticidal treatment renders preventive treatment a desirable alternative in endemic areas. To evaluate the efficacy of milbemycin oxime as a chemoprophylactic agent in cats, 48 cats were inoculated with infective D immitis larvae. Single oral treatment with 2.3 mg of milbemycin oxime (0.5 to 0.9 mg/kg of body weight) at 30 or 60 days after inoculation with infective larvae gave strong but incomplete protection. Treatment at 60, as well as 90, days after inoculation with infective larvae was completely effective in preventing development of infection. A control group of inoculated, but untreated, cats was monitored biweekly for hematologic changes and for changes in parasite-specific serum antigen and antibody concentrations. Pronounced increases in total leukocyte counts and eosinophil numbers were associated with the estimated time of in vivo molting from fourth- to fifth-stage larvae. Antibody reactivity correlated with infection status, but serum antigen concentrations through 161 days after inoculation were undetectable.

A study was performed to determine whether equine peritoneal macrophages produce interleukin 6 (IL-6) in vitro in response to endotoxin. Peritoneal fluid was collected from 14 clinically normal adult horses and was used as the source of peritoneal macrophages. Macrophages from each horse were isolated and cultured separately in vitro in the absence or presence of various concentrations (0.5, 5, or 500 ng/ml) of endotoxin (lipopolysaccharide from Escherichia coli 055:B5). Culture medium supernatants were collected after 3, 6, 12, and 24 hours' incubation and were frozen at - 70 C until assayed for IL-6 activity. Supernatant IL-6 activity was determined by use of a modified colorimetric assay and the murine hybridoma cell line B13.29 clone B.9, which is dependent on IL-6 for survival. Results indicated that equine peritoneal macrophages produce IL-6 in vitro and that supernatant medium IL-6 activity was significantly (P < 0.05) increased by exposure to endotoxin. Significant (P < 0.05) time and treatment effects on macrophage IL-6 production were apparent. The IL-6 activity peaked at 6 or 12 hours' incubation, then remained high through 24 hours' incubation, regardless of endotoxin exposure. Medium IL-6 activity during 3 and 6 hours' incubation was significantly (P < 0.05) greater in macrophages exposed to 5 or 500 ng of endotoxin/ml than in those exposed to 0.5 ng of endotoxin/ml; however peak IL-6 activity was similar among all endotoxin concentrations. Endotoxin concentration did not have an effect on medium IL-6 activity from macrophages exposed to endotoxin for 12 or 24 hours.

Three doses of sodium monoiodoacetate (MIA) were used to induce degenerative changes in articular cartilage in middle carpal joints of horses. Twelve young (2- to 5-year-old) horses, free of lameness, were randomly allotted to 3 groups. One middle carpal joint of each horse was injected with 0.9% NaCl solution (control joint). The contralateral middle carpal joint was injected with 0.09 mg of MIA/kg of body weight (group 1); 0.12 mg(kg (group 2); or 0.16 mg(kg (group 3). After MIA administration, horses were allowed ad libitum exercise in a 2-acre paddock for 12 weeks. At the end of the study, gross and microscopic tissue changes were evaluated and biochemical analyses of articular cartilage were done. Grossly, diffuse partial-thickness articular cartilage lesions were observed in group-2 (n = 2) and group-3 (n = 4) horses, but not in group-1 horses. Articular cartilage uronic acid content was significantly (P < 0.03) decreased in all MIA-injected joints, compared with controls. Articular cartilage matrix staining with safranin-O was decreased in 3 of 4 MIA-injected joints of group-1 horses and in all MIA-injected joints of group-2 and group-3 horses, compared with controls (P < 0.06). Microscopic degenerative changes in articular cartilage were not significantly different between MIA-injected and control joints in group-1 horses, but were increased (P < 0.06) in all MIA-injected joints of group-2 and group-3 horses, compared with controls. Qualitatively, decreased matrix staining and degenerative changes were more severe in group-3 horses. On the basis of articular cartilage gross and microscopic changes, as well as biochemical changes, 0.12 mg of MIA/kg injected intra-articularly was determined to induce moderate degrees of articular cartilage degeneration. This model of chemically induced articular cartilage injury could be useful for evaluating treatment effects of anti-arthritic drugs in horses.

Forty-eight cattle were used in 4 experiments; 6-week-old calves in experiments 1-3 (n = 24) and 10-month-old heifers in experiment 4 (n = 24). In experiments 1-3, 7 groups of 3 calves each were inoculated SC with 5 strains of Brucella abortus: virulent strain 2308 (2 groups), vaccine strain 19 (2 groups), and mutant strains RB51, 19 delta 31K, and 19 delta SOD. Sera and lymph node tissues were examined at 2-week intervals for evidence of infection. At postinoculation (PI) week 12, 2 calves in each group were given dexamethasone for 5 days. Calves were then euthanatized and lymphoid tissue, spleen, liver, and bone marrow were examined for evidence of B abortus. Calves given strain 2308 had large numbers of bacteria in their lymph nodes, marked granulomatous lymphadenitis in the deep cortex, and loss of lymphoid cells in superficial cortical areas. In addition, they had high serum antibody titers at PI week 16. Calves given strain 19, or genetic mutants derived from strain 19, cleared bacteria from lymph nodes more rapidly, had less lymphoid destruction, and developed antibody titers that did not persist for 16 weeks. The RB51 strain (rough) was cleared most rapidly from lymphoid tissues and induced serum antibody responses only to the core of the lipopolysaccharide molecule. Treatment of calves with dexamethasone did not cause B abortus to reappear in tissues of any calves, nor did serum antibody titers increase. In experiment 4, designed to compare the effects of age, 4 groups (n = 4) of 10-month-old heifers were given 1 B abortus strain each (19, RB51, 19 delta 31K, or 19 deltaSOD), using the same methods. Results of bacteriologic culturing and antibody responses were similar to those in the calves, except that strain RB51 persisted longer in heifers. Results of these studies indicated that, in cattle, the genetically engineered deletion mutants of B abortus do not cause unusual lesions, do have characteristics that closely resemble the parental strain, and could be candidates for use in a live vaccine.

Conditions for purification of the ninth component of bovine complement (C9) were established. The conditions for binding and elution from diethylaminoethyl cellulose and hydroxylapatite were different than for human C9. Serum albumin, a frequent contaminant of bovine C9 preparations, was removed by chromatography on reactive-red agarose. The calculated molecular weight of bovine C9 was 66,000, and reduction with 2-mercaptoethanol affected its migration on polyacrylamide gel electrophoresis. Some preparations of bovine C9 migrated as 2 bands when partially reduced, but extensively reduced preparations had a single band.