Comparison of four immune variables and pulmonary lesions of goats with intrapulmonary exposure and subsequent intrathoracic challenge exposure with Pasteurella haemolytica

A comparison of immune variables following lung sensitization with live Pasteurella haemolytica serotype 1 (Ph1)-impregnated agar beads was done in 2 separate trials. The Ph1 immune variables studied were blood bactericidal activity, serum bacteriolysis, total classical complement, and indirect hemagglutination antibody. Each trial had 16 male weanling goats: 6 controls and 10 principals. In trial 1, each goat was surgically catheterized through the trachea, then the material was deposited in a bronchus. The controls received only agar beads and the principals received agar beads impregnated with live Ph1. These goats were studied for 32 days, euthanatized, and necropsied. In trial 2, the controls were each transthoracically injected with agar beads into the left lung and the principals were similarly injected with agar beads impregnated with live Ph1. These goats were studied for 35 days, then challenge exposed transthoracically by injection of Ph1 in saline solution (1.2 x 10(7) CFU/ml) into the right lung. Four days later, they were euthanatized and necropsied. The volume of lung consolidated tissue was an excellent measure of Ph1 immunity. Principal goats generated solid protective immunity to subsequent challenge exposure because minimal or no lung consolidation was observed, whereas large volumes of lung consolidation were seen in the controls. The principal goats in trial 1 gave a weak serum indirect hemagglutination Ph1 antibody response, which was attributed to the bronchial method of depositing the Ph1. The corresponding response of the control group remained negative. The Ph1 agar beads (1 x 10(6) CFU in 0.5 ml) protected the bacteria from immediate phagocytosis and lysis as indicated by the induced pneumonic deaths of 2 principals 5 days later.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of a toxoid vaccine to protect goats against intradermal challenge exposure to Corynebacterium pseudotuberculosis

Two groups of male, 9-week-old goats (5 goats/group) were vaccinated subcutaneously with formalized exotoxin of Corynebacterium pseudotuberculosis, with Freund's incomplete adjuvant. Each goat was given 2 vaccinations, 2 weeks apart. At each vaccination, each group 1 goat was given 0.5 ml of toxoid, and each group 2 goat was given 1 ml of toxoid. Twenty days after the 2nd vaccination, vaccinated goats and 5 nonvaccinated 12-week-old goats (controls) were inoculated intradermally (challenge exposed) with live C pseudotuberculosis, monitored for 13 weeks, and euthanatized. At necropsy, 5 of the 10 vaccinated goats did not have C pseudotuberculosis lesions, 3 had abscesses limited to the inoculation site and draining lymph node, and 2 had disseminated bacterial lesions. Of the 5 nonvaccinated controls, 4 had disseminated abscesses and 1 had a single abscess in an internal node. Serologically, 9 of the 10 vaccinated goats developed positive (greater than or equal to 1:8) antibody titers against the exotoxin within 1 week after inoculation; the 10th goat seroconverted 2 weeks after inoculation, whereas control goats required 3 weeks to develop a positive antibody response. Therefore, early during an infection with C pseudotuberculosis, antibodies against the exotoxin may protect a goat against spread of the organism. All goats were injected intradermally before challenge exposure, 10 days after challenge exposure, and at 4, 8, and 12 weeks after challenge exposure with a skin-test reagent composed of fragmented bacterial cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vivo evaluation of vaccine efficacy against challenge with a contemporary field isolate from the α cluster of H1N1 swine influenza virus

Influenza A virus vaccines currently contain a mixture of isolates that reflect the genetic and antigenic characteristics of the currently circulating strains. This study was conducted to evaluate the efficacy of a trivalent inactivated swine influenza virus vaccine (Flusure XP) in pigs challenged with a contemporary α-cluster H1N1 field isolate of Canadian swine origin. Pigs were allocated to vaccinated, placebo, and negative-control groups and monitored for respiratory disease for 5 d after challenge. On the challenge day and 5 d after challenge the serum of the vaccinated pigs had reciprocal hemagglutination inhibition antibody titers 40 for all the vaccine viruses but ≤ 20 for the challenge virus. Gross lesions were present in the lungs of all pigs that had been inoculated with the challenge virus, but the proportion of lung tissue consolidated did not differ significantly between the placebo and vaccinated pigs. However, the amount of virus was significantly reduced in the nasal secretions, lungs, and bronchoalveolar lavage fluid in the vaccinated pigs compared with the placebo pigs. These results indicate that swine vaccinated with Flusure XP were partially protected against experimental challenge with a swine α-cluster H1N1 virus that is genetically similar to viruses currently circulating in Canadian swine.     

Effects of adjuvant-augmented germling vaccines in turkey poults challenged with Aspergillus fumigatus

Turkey poults were vaccinated with combinations of two different germling preparations and three adjuvants (N-acetylmuranyl-L-alanyl-D-isoglutamine, Pasteurella multocida lipopolysaccharide [LPS], and avridine) at 1 and 2 weeks of age, and their immunity was challenged by sublethal exposure to aerosols of Aspergillus fumigatus conidia at 1 month of age. Fewer turkeys in the groups given vaccines prepared from germlings grown on Dorset's and Henley's medium (D&H) had organisms in lung tissue at 2 weeks after challenge exposure as compared with those vaccinated with germling grown on neopeptone dialysate (Neo). The LPS of P. multocida appeared to be the most efficacious of the adjuvants in the D&H vaccine group, as A. fumigatus was isolated from only one of eight turkeys in this group; the number of organisms per gram of lung tissue was low compared with other vaccine groups at 2 weeks after challenge exposure; and poults given D&H vaccine with LPS as adjuvant had less-severe lung lesions than other groups. These differences in lung lesions were more marked at 2 weeks than at 8 weeks after challenge exposure. The only difference among other parameters in the vaccinated turkeys was lower heterophil counts in the turkeys given D&H-prepared vaccines than in unvaccinated controls. This was probably due to less-severe infections resulting from protective effects of these vaccines.     

Experimental infection of dogs with Brucella abortus

Thirteen female dogs, which included eight principals that were fed approximately 4.4 X 10(10) colony forming units (cfu) of Brucella abortus strain 2308 and five sentinels that were housed with the principals, were examined for serologic responses, blood culture, tissue distribution of the organisms and pathologic lesions. Serum samples from each dog were tested on the day of exposure and on post exposure days 5, 7, 10, 14, 21, 28, 35, 42 and 49 for antibodies to B. abortus, using the brucellosis card (BC), standard tube agglutination (STA), 2-mercaptoethanol (ME) and rivanol (RIV) tests. Antibodies were detected in the principals by day 5 and increased through day 21. The STA test was the first to become positive, followed by the BC, ME and RIV tests. After 28 days, the serologic titers receded. From day 14 through day 42, all principals had greater than or equal to 1:50 STA titers. On day 49, seven principals had greater than or equal to 1:50 STA titers and one had a 1:25 STA titer. The sentinels were negative for all tests, except sentinel number 9 which had STA titers ranging from 1:25 to 1:50 on day 14 through day 35. Blood cultures that were obtained from each principal at intervals from one hour after exposure through 49 days were negative. Brucella abortus was isolated from various lymph nodes of the eight principals and from sentinel number 9, which was apparently infected by ingesting brucellae contaminated feces from the principals. Microscopic lesions were not observed in the culture-positive tissues examined.     

Studies on the immunogenicity of Streptococcus equi vaccines in foals.

The ability of either formalin-treated or heat-inactivated whole Streptococcus equi cell vaccines or partially purified M-protein of S. equi to give rise to protective antibody levels was studied in Standardbred foals by serological means. Two commercial preparations, i.e. a beta-propiolactone killed whole S. equi cell bacterin and a cell-free extract of S. equi cells were included in the study. The mean passive hemagglutination antibody titers (10 X log2) in sera of foals given either four doses of formalin-treated whole cell vaccine or an initial dose of formalin-treated followed by three doses of heat-inactivated vaccine with or without levamisole were significantly higher two weeks after the final dose. These passive hemagglutination antibody titers were higher in foals given formalin-treated whole cell vaccine (6.7 +/- 1.5) than given commercial bacterin (4.5 +/- 2.1). The passive hemagglutination antibody titers in all the groups decreased at 12 to 16 weeks after fourth dose of the vaccine. Foals given a commercial cell-free extract did not show a significant increase in passive hemagglutination antibody titers even up to four weeks after third dose. A group of six pony foals immunized with partially-purified M protein showed mean passive hemagglutination antibody titers lower than those observed in foals given whole cell vaccines. In a challenge experiment with S. equi, two of six foals vaccinated with partially-purified M-protein and all three controls developed clinical disease. The passive hemagglutination antibody of vaccinated foals increased after challenge, while at 28 days postchallenge the passive hemagglutination antibody titers of vaccinates and recovered controls were similar.     

Effect of danofloxacin (Advocin A180) on goats affected with contagious caprine pleuropneumonia

The efficacy of danofloxacin (Advocin A180) was evaluated for the treatment of contagious caprine pleuropneumonia (CCPP) caused by Mycoplasma capricolum subsp. capripneumoniae. Ten healthy Angora goats, confirmed free of CCPP, were exposed to clinically affected animals from a natural outbreak in Thrace, Turkey. After 14 days exposure, 8 goats showed pyrexia ( > or = 41 degrees C). Shortly after, the Angora goats were divided randomly into two groups. Five of these were injected with danofloxacin (6 mg/kg subcutaneously), which was repeated after 48 h; the five remaining animals received saline. Goats were monitored clinically and blood samples were collected for serology. Animals with severe disease were withdrawn from the trial. Goats completing the study were euthanized at day 42. Lung tissue and bronchial fluid were collected for mycoplasma isolation. All danofloxacin-treated goats showed resolution of clinical disease by the end of the trial. Two saline-treated goats failed to complete the study owing to CCPP. Danofloxacin-treated goats showed fewer lung lesions and had significantly lower combined clinical scores than saline controls (p < 0.001). Danofloxacin was found to be highly effective in the treatment of CCPP in goats.     

Virulence of fungal spores determined by tracheal inoculation of goats following inhalation of aerosolized sterile feedyard dust

OBJECTIVE: To compare the virulence of spores of 7 fungi by tracheal inoculation of goats following exposure of goats to an aerosol of sterilized feedyard dust. Animals-54 weanling Boer-Spanish goats. PROCEDURE: A prospective randomized controlled study was conducted. There were 7 fungal treatment groups, a tent control group, and a pen control group (n = 6 goats/group). Goats in the 7 treatment and tent control groups were exposed to autoclaved aerosolized feedyard dust for 4 hours in a specially constructed tent. Goats in the 7 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas tent control goats were intratracheally inoculated with 30 mL of physiologic saline (0.9% NaCI) solution. These treatments were repeated each week for 6 weeks. RESULTS: Severity of pathologic changes differed significantly among the 7 fungal treatment groups as determined on the basis of gross atelectatic and consolidated lung lesions and histologic lesions of the lungs. Descending order for severity of lesions was Mucor ramosissimus, Trichoderma viride, Chaetomium globosum, Stachybotrys chartarum, Aspergillus fumigatus, Penicillium chrysogenum, and Monotospora lanuginosa. Trichoderma viride spores were the most invasive and were isolated from the bronchial lymph nodes and thoracic fluid of all 6 goats administered this organism. Spores were observed-histologically in lung tissues harvested 72 hours after inoculation from all treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: 4 of 7 fungal spore types induced significantly larger lung lesions, compared with those induced by the other 3 spore types or those evident in control goats.     

Effect of vaccination with live or killed Pasteurella haemolytica on resistance to experimental bovine pneumonic pasteurellosis

Using 6- to 8-month-old beef calves, 3 experiments were conducted to compare the effect of vaccination with live or killed Pasteurella haemolytica on resistance to a transthoracic challenge exposure with the organism and to correlate serum antibody response with resistance. In each experiment, calves were vaccinated twice at 1-week intervals and were challenge exposed 21 days after the first inoculation. Lung lesions were evaluated by a system, such that higher scores indicated the more severe lesions. In each experiment, calves immunized with live P haemolytica had lower lesion scores than calves vaccinated with saline solution or bacterin. In 2 of the experiments, the differences were significant (P less than 0.05). In all experiments, calves vaccinated parenterally with a commercial P haemolytica/P multocida bacterin or with a formalin-killed P haemolytica bacterin had lesion scores that were not significantly different (P greater than 0.05) than for control calves vaccinated with saline solution. Live and killed bacterial preparations induced a significant serum antibody response to P haemolytica as measured by a quantitative fluorometric immunoassay. The antibody response to vaccination was not affected by preexisting titers to P haemolytica. Serum antibody titers were not consistently as high for calves vaccinated with bacterins as for calves vaccinated with live organisms. Although high antibody titers correlated with low lesion scores when calves vaccinated with saline solution or live organisms were analyzed collectively, there was not a significant correlation between the 2 variables when calves, vaccinated with saline solution or with bacterin, were analyzed collectively. These data indicate that, although bacterins may induce a detectable serum antibody response, they do not induce protection against transthoracic challenge exposure to P haemolytica.     

Absence of protection against challenge with aspergillus fumigatus by adoptive transfer of splenocytes from convalescent turkeys

Only limited protective immunity against aspergillosis after experimental immunization of turkeys has been previously demonstrated. No studies evaluating the efficacy of transfer of immunity in preventing aspergillosis in birds have been reported. This study consisted of two trials assessing the level of protection against Aspergillus fumigatus challenge afforded by transfer of splenocytes from convalescent turkeys. Three treatment groups of 12-to-14-wk-old Beltsville small white (BSW) turkeys comprising the splenocyte donors were prepared by one of the following: 1) intra-air sac (IA) challenge with A. fumigatus conidia 5 wk prior to transfer; 2) IA challenge and then intravenous (i.v.) injection of killed conidia 1 wk prior to transfer; or 3) sham inoculations. Splenocytes from each group were pooled, enriched for mononuclear leukocytes by density gradient centrifugation, and diluted in cell culture medium (CM). Cell viability was assessed by dye exclusion. Each splenocyte preparation was administered intravenously to one of three recipient groups consisting of 10 BSW turkeys each. A control group (n = 10) was given cell-free CM. Recipients were challenged with viable A. fumigatus conidia 16 hr after splenocyte transfer by unilateral IA (trial 1) or i.v. (trial 2) inoculation. Lesion scores postchallenge revealed no differences between turkeys given splenocytes from convalescent vs. naive (control) turkeys. IA exposure produced ipsilateral lesions in air sacs and lung, whereas i.v. exposure produced severe miliary hepatitis. Donor cell function was confirmed by mitogen blastogenesis; however, cells were nonresponsive to A. fumigatus antigens, regardless of previous exposure status.     

Effects of inhaled fine dust on lung tissue changes and antibody response induced by spores of opportunistic fungi in goats

OBJECTIVE: To investigate the effects of sterile fine dust aerosol inhalation on antibody responses and lung tissue changes induced by Mucor ramosissimus or Trichoderma viride spores following intratracheal inoculation in goats. ANIMALS: 36 weanling Boer-Spanish goats. PROCEDURES: 6 goats were allocated to each of 2 M ramosissimus-inoculated groups, 2 T viride-inoculated groups, and 2 control (tent or pen) groups. One of each pair of sporetreated groups and the tent control group were exposed 7 times to sterilized fine feedyard dust (mean+/-SD particle diameter, <7.72+/-0.69 microm) for 4 hours in a specially constructed tent. Goats in the 4 fungal treatment groups were inoculated intratracheally 5 times with a fungal spore preparation (30 mL), whereas tent control goats were intratracheally inoculated with physiologic saline (0.9% NaCl) solution (30 mL). Pen control goats were not inoculated or exposed to dust. Goats received an IV challenge with equine RBCs to assess antibody responses to foreign antigens. Postmortem examinations were performed at study completion (day 68) to evaluate lung tissue lesions. RESULTS: 5 of 7 deaths occurred between days 18 and 45 and were attributed to fine dust exposures prior to fungal treatments. Fine dust inhalation induced similar lung lesions and precipitating antibodies among spore-treated goats. Following spore inoculations, dust-exposed goats had significantly more spores per gram of consolidated lung tissue than did their nonexposed counterparts. CONCLUSIONS AND CLINICAL RELEVANCE: Fine dust inhalation appeared to decrease the ability of goats to successfully clear fungal spores from the lungs following intratracheal inoculation.     

Sequential titration of bovine lung and serum antibodies after parenteral or pulmonary inoculation with Pasteurella haemolytica

Calves were vaccinated by intrabronchial or subcutaneous injection of formalinized Pasteurella haemolytica. Antibody in serum, nasal washings, and bronchoalveolar washings was titrated sequentially before and after calves were vaccinated and then challenge exposed with live homologous bacteria. Bronchoalveolar washings were collected by fiberoptics bronchoscopy, and antibody was titrated by indirect (antiglobulin) bacterial agglutination. Responsiveness to vaccination was related in initial serum antibody concentrations. Calves with serum antibody titers of 1:20 or more were nonresponsive, whereas with few exceptions, calves having titers of less than 1:20 responded to vaccination. Results indicated that serum and lung antibody were induced by subcutaneous or by intrabronchial inoculation of formalinized P haemolytica. By either route of immunization, serum antibody was more persistent than was lung antibody, and pulmonary challenge exposure with live P haemolytica did not alter existing titers.     

An epizootic of parainfluenza virus type 1 in a group of C57B16 mice

An epizootic of respiratory troubles was noticed in a group of C57B16 mice used to study their response following inoculations of different thymic extracts. The infection was characterized by a high level of mortalities. Macroscopically, the lungs of affected animals showed red consolidated areas on the lobes. Microscopically, an acute bronchopneumonia with eosinophilic intracytoplasmic inclusion bodies in the epithelial cells of the bronchi were seen. Those lesions suggest a parainfluenza virus type 1 infection.

The presence of viral particles, morphologically similar to members of the Paramyxoviridae family in lung homogenates observed under electron microscopy and the elevated serum complement fixation and hemagglutination inhibition antibody titers to parainfluenza virus type 1 confirm the diagnosis. The source of the infection is unknown but four hypothesis are proposed.

Healthy animals free of demonstrable antibodies specific to parainfluenza virus type 1 were obtained and the experiment was repeated. No mortalities were observed and the animals remained free of demonstrable complement fixation and hemagglutination inhibition antibodies throughout the experiment.

     

Recovery of transmissible gastroenteritis virus from chronically infected experimental pigs.

Transmissible gastroenteritis (TGE) virus was reisolated from pulmonary and intestinal tissues from 6 of 9 chronically infected experimental pigs (principals) necropsied 30 to 104 days after inoculation. Tissue homogenates (lung and small intestine) from the principals were prepared and inoculated into 3- to 5-day-old gnotobiotic pigs. The virus reisolated from the tissue homogenates produced a milder disease on 1st passage and a more severe disease on 2nd passage. The chronically infected experimental pigs (principals) developed serum-neutralization titers to TGE of 1:30 to 1:525. There appeared to be no relationship between serum titers and reisolation of TGE virus from the 9 principals. The persistence of virus in lung or intestine to 104 days indicates the recovered (or carrier) pig may be considered the primary source of TGE virus infection.     

Protection against feline leukemia virus infection by use of an inactivated virus vaccine.

The protective immunity induced by 3 experimental FeLV vaccines were evaluated: Prototype inactivated FeLV vaccine developed from a molecularly cloned FeLV isolate (FeLV-FAIDS-61E-A); a mixture of immunodominant synthetic peptides corresponding to regions of the FeLV-Gardner-Arnstein-B (FeLV-GA-B) envelope proteins; and an adjuvant-disrupted but non-activated virus prepared from a non-cloned FeLV field isolate comprised of subgroup A and B viruses (FeLV-05821-AB). Included as controls were parallel groups of cats inoculated with adjuvants alone or with an established commercial FeLV vaccine. After each inoculation and after virulent virus challenge exposure, sera from all cats were assayed for ELISA-reactive antibody against purified FeLV, FeLV neutralizing (VN) antibody, and FeLV antigenemia/viremia--viral p27 antigen in serum and within circulating leukocytes. Immunity was challenged by oral/nasal exposure of vaccinated and control cats with FeLV-FAIDS-61E-A or FeLV-05821-AB, an infective, noncloned, tissue-origin, FeLV field isolate containing subgroup-A and -B viruses. Vaccine-induced immunity was assessed by comparing the postchallenge-exposure incidence of persistent viremia and the pre- and postchallenge exposure titers of VN and ELISA antibody in cats of the control and vaccine groups. The percentage of cats, that resisted development of persistent viremia after FeLV challenge exposure and the preventable fraction (PF) for the vaccine groups (which adjusts for the severity of the challenge and the degree of innate resistance in the controls) were as follows: adjuvant controls, 26%; FeLV-FAIDS-61E-A inactivated virus vaccine, 95% (PF = 93.2%); FeLV-GA-B peptide vaccine, 5% (-28.4%); FeLV-05821-AB noninactivated vaccine, 67% (55.4%); and commercial FeLV vaccine, 35% (12.2%). The prechallenge exposure mean VN antibody titer for each group was: less than 1:8 in the adjuvant controls; 1:43 in the FeLV-FAIDS-61E-A-vaccinated cats; less than 1:8 in the peptide-vaccinated cats; 1:38 in the noninactivated virus-vaccinated cats group; and 1:12 in the cats vaccinated with the commercial vaccine. Thus, induction of VN antibody in the vaccinated cats, although modest, appeared to be correlated with induction of protective immunity as defined by resistance to FeLV challenge exposure. Results of these studies indicate that inoculation of cats with an experimental inactivated virus vaccine prepared from a molecularly cloned FeLV isolate was most effective in stimulating protective immunity against heterologous and homologous FeLV challenge exposure.     

Bovine pneumonic pasteurellosis: effect of culture age of Pasteurella haemolytica used as a live vaccine

Five experiments were conducted that compared aerosol immunization of calves with live Pasteurella haemolytica from logarithmic (6 hour) or stationary (20 to 22 hour) phase cultures. Calves were challenge exposed by transthoracic injection with P haemolytica. In 4 experiments, calves inoculated with 6-hour cultures had slightly lower mean lesion scores (indicating greater resistance to challenge exposure) than those inoculated with 20- to 22-hour cultures. High antibody titers, as detected by a quantitative fluorometric immunoassay or the indirect hemagglutination test, correlated directly with lung resistance (based on lesion scores) regardless of the age of the culture used as the immunogen.     

The Effects of Dexamethasone on the Response of Bronchus-associated Lymphoid Tissue to Intranasal Administration of Formalin-killed Pasteurella haemolytica A2 in Goats

A trial was conducted to observe the immediate and chronic effects in goats of dexamethasone administration on the bronchus-associated lymphoid tissue (BALT) response to intranasal administration of formalin-killed Pasteurella haemolytica A2. Twenty-four goats were divided into four groups. Those in group 1 were injected intramuscularly with 1 mg/kg dexamethasone on three consecutive days, followed by intranasal exposure to formalin-killed P. haemolytica A2 one day after the last dexamethasone treatment. The goats in group 2 were similarly injected with dexamethasone followed by intranasal exposure to formalin-killed P. haemolytica A2 21 days after the last dexamethasone treatment. The animals in group 3 were exposed intranasally to formalin-killed P. haemolytica A2 without prior dexamethasone treatment. The animals in group 4 were untreated controls. The intranasal exposures to formalin-killed P. haemolytica A2 were repeated 2 weeks later. Intranasal exposure to formalin-killed P. haemolytica 1 day after dexamethasone treatment further reduced the number and size of BALT compared to the untreated control. Significantly (p<0.01) more reduction of BALT occurred in goats exposed to formalin-killed P. haemolytica A2 21 days after dexamethasone treatment. On the other hand, intranasal exposure of goats without prior dexamethasone treatment stimulated the BALT compared to the untreated controls.     

Efficacy of swine influenza A virus vaccines against an H3N2 virus variant

We compared the efficacy of 3 commercial vaccines against swine influenza A virus (SIV) and an experimental homologous vaccine in young pigs that were subsequently challenged with a variant H3N2 SIV, A/Swine/Colorado/00294/2004, selected from a repository of serologically and genetically characterized H3N2 SIV isolates obtained from recent cases of swine respiratory disease. The experimental vaccine was prepared from the challenge virus. Four groups of 8 pigs each were vaccinated intramuscularly at both 4 and 6 wk of age with commercial or homologous vaccine. Two weeks after the 2nd vaccination, those 32 pigs and 8 nonvaccinated pigs were inoculated with the challenge virus by the deep intranasal route. Another 4 pigs served as nonvaccinated, nonchallenged controls. The serum antibody responses differed markedly between groups. After the 1st vaccination, the recipients of the homologous vaccine had hemagglutination inhibition (HI) titers of 1:640 to 1:2560 against the challenge (homologous) virus. In contrast, even after 2nd vaccination, the commercial-vaccine recipients had low titers or no detectable antibody against the challenge (heterologous) virus. After the 2nd vaccination, all the groups had high titers of antibody to the reference H3N2 virus A/Swine/Texas/4199-2/98. Vaccination reduced clinical signs and lung lesion scores; however, virus was isolated 1 to 5 d after challenge from the nasal swabs of most of the pigs vaccinated with a commercial product but from none of the pigs vaccinated with the experimental product. The efficacy of the commercial vaccines may need to be improved to provide sufficient protection against emerging H3N2 variants.     

Response of goats to repeated infections with Fasciola gigantica

One or two mature primary infections with Fasciola gigantica which had been removed by anthelmintic treatment resulted in a significant reduction in the number of flukes recovered from challenge infection as compared with that from controls.

Characteristic lesions of fascioliasis were seen in the livers of the 3 groups, however, goats with two primary abbreviated infections prior to challenge showed more severe lesions than those of animals with one primary abbreviated infection or those of challenge controls. The former group also showed the highest serum glutamate dehydrogenase and sorbitol dehydrogenase peaks following challenge infections and pulmonary fascioliasis was encountered in one of the goats of this group. Haemoglobin concentration and packed-cell volume decreased after infection in the three groups of goats.     

Assessment of the efficacy of a single dose of a recombinant vaccine against West Nile virus in response to natural challenge with West Nile virus-infected mosquitoes in horses

OBJECTIVE: To determine the onset of immunity after IM administration of a single dose of a recombinant canarypox virus vaccine against West Nile virus (WNV) in horses in a blind challenge trial. ANIMALS: 20 mixed-breed horses. PROCEDURE: Horses with no prior exposure to WNV were randomly assigned to 1 of 2 groups (10 horses/group). In 1 group, a recombinant canarypox virus vaccine against WNV was administered to each horse once (day 0). The other 10 control horses were untreated. On day 26, 9 treated and 10 control horses were challenged via the bites of mosquitoes (Aedes albopictus) infected with WNV. Clinical responses and WNV isolation were monitored for 14 days after challenge exposure; antibody responses against WNV after administration of the vaccine and challenge were also assessed in both groups. RESULTS: Following challenge via WNV-infected mosquitoes, 1 of 9 treated horses developed viremia. In contrast, 8 of 10 control horses developed viremia after challenge exposure to WNV-infected mosquitoes. All horses seroconverted after WNV challenge; compared with control horses, antibody responses in the horses that received the vaccine were detected earlier. CONCLUSIONS AND CLINICAL RELEVANCe: In horses, a single dose of the recombinant canarypox virus-WNV vaccine appears to provide early protection against development of viremia after challenge with WNV-infected mosquitoes, even in the absence of measurable antibody titers in some horses. This vaccine may provide veterinarians with an important tool in controlling WNV infection during a natural outbreak or under conditions in which a rapid onset of protection is required.