Comparison of the efficacy of a subunit and a live streptomycin-dependent porcine pleuropneumonia vaccine

Objective To evaluate the efficacy of two new-generation porcine pleuropneumonia vaccines when challenged with Australian isolates of Actinobacillus pleuropneumoniae of serovars 1 and 15.
Design The Porcilis APP vaccine and an experimental streptomycin-dependent strain of A pleuropneumoniae were evaluated in a standardised pen trial. Each vaccine/challenge group consisted of 10 pigs.
Results With the serovar 1 challenge, the Porcilis APP vaccine and the live vaccine, compared with the control group, gave significant protection in terms of clinical signs, lung lesions, re-isolation scores and average daily gain (ADG) postchallenge. Only the Porcilis APP vaccine provided significant protection against mortality. In the serovar 15 challenged pigs, the only significant difference detected was that the Porcilis APP vaccinated pigs had a better postchallenge ADG than the controls. None of the Porcilis APP vaccinated pigs showed signs of depression postvaccination and none were euthanased after challenge with either serovar 1 or 15. The pigs vaccinated with the live vaccine showed obvious depression after each vaccination and a total of 3 pigs were euthanased after challenge (one with serovar 1 and two with serovar 15).
Conclusions Both of the vaccines provided significant protection against a severe challenge with serovar 1 A pleuropneumoniae. Neither vaccine was effective against a serovar 15 A pleuropneumoniae challenge. There was evidence that the Porcilis APP vaccine did provide some protection against the serovar 15 challenge because the ADG, after challenge of pigs given this vaccine, was greater than the control pigs.     

Comparative efficacy of two single-dose bacterins in the control of Mycoplasma hyopneumoniae in swine raised under commercial conditions in Brazil

A field study was conducted in Brazil to evaluate the efficacy of single vaccination of pigs with two bacterins to prevent Mycoplasma hyopneumoniae lung lesions. The first (T1) treatment group (174 pigs) was injected with 2 mL of saline solution; group T2 (177 pigs) with 2 mL of bacterin A, and group T3 (174 pigs) with 2 mL of bacterin B. On days-on-test (DOT) 0, 35, 66, 97 and 125, blood samples and tonsil swabs were collected from selected pigs for antibody determination (indirect ELISA) and PCR assay for the presence of M. hyopneumoniae. Pigs were slaughtered on DOT 126-129 and lung lesions were scored blindly. Bacterin A vaccinated pigs had significantly (P < or = 0.05) lower lung lesion scores (0.2%) than bacterin B (0.4%) or saline-treated pigs (1.2%); there was also a significantly lower (P < or = 0.05) number of pigs with lung lesions (27.1%), than bacterin B (38.2%) or saline-treated (55.4%) pigs. The two vaccines had similar (P>0.05) results in terms of mean weight gain, average daily weight gain, feed efficiency, frequency of PCR positives, and there was similar antibody conversion (ELISA). It was concluded that although the productivity parameters and antibody conversions were similar, bacterin A was more effective in preventing and reducing the severity of lung lesions than bacterin B.     

Mortality in swine herds endemically infected with Haemophilus pleuropneumoniae: effect of immunization with cross-reacting lipopolysaccharide core antigens of Escherichia coli

The benefit of increased immunity to cross-reacting lipopolysaccharide core antigens of gram-negative bacteria induced by vaccination with an Rc mutant of Escherichia coli 0111:B4 (strain J5) was evaluated in commercial swine herds endemically infected with Haemophilus pleuropneumoniae. Weanling pigs were vaccinated IM with E coli J5 (group 1) before the expected time of H pleuropneumoniae infection. Clinical signs, antibiotic treatment frequency, mortality, growth performance (days to market weight), and serologic responses of the pigs were monitored for approximately 5 months after vaccination. The results were compared with those of pigs vaccinated IM with a commercial H pleuropneumoniae bacterin (group 2) and with those of nonvaccinated control pigs of the same age (group 3). The treatment frequency and growth performance were similar in the 3 groups. However, vaccination with E coli J5 or with the H pleuropneumoniae bacterin lowered mortality, compared with mortality in the controls. Serum titers against E coli J5 increased after vaccination with the E coli J5 bacterin, but were not increased by vaccination with the H pleuropneumoniae. In contrast, serum titer to E coli J5 increased in all treatment groups as a result of H pleuropneumoniae infection or exposure. The protection against lethal H pleuropneumoniae infections in swine that was provided by vaccination with the E coli J5 and the H pleuropneumoniae bacterin appeared to be immunologically distinct on the basis of serologic analysis, indicating the possibility of different mechanisms of protection.     

Streptococcus suis serotype 9 bacterin immunogenicity and protective efficacy

Streptococcus suis diseases in pigs, most importantly meningitis, are worldwide responsible for major economic losses in the pig industry. About one fourth of invasive S. suis diseases are caused by S. suis serotype 9 strains in Europe. However, little is known about serotype 9 since most studies were performed with serotype 2. The objective of this study was to determine the immunogenicity and protective efficacy of a serotype 9 bacterin in piglets. Challenge was conducted with a reference serotype 9 strain, belonging to the same clonal complex but to a different sequence type as the bacterin strain. The bacterin induced protection against mortality but not morbidity. Eleven days post infection, 3 of 7 vaccinated survivors were not fully convalescent and had not eliminated the challenge strain from inner organs completely. In accordance with the clinical findings, the majority of piglets showed fibrinous-suppurative lesions in at least one inner organ or tissue. In contrast to the placebo group such lesions were not detected in one third of bacterin-vaccinated piglets. Determination of specific serum IgG titers revealed that the bacterin elicited seroconversion against muramidase-released protein and basic membrane lipoprotein. Furthermore, vaccination was associated with induction of opsonizing antibodies against the serotype 9 challenge strain. However, titers of opsonizing antibodies were rather low in comparison to those found in our previous serotype 2 vaccination trial. Piglets developed substantially higher titers of opsonizing antibodies after challenge. Opsonizing antibodies were absorbable with the serotype 9 challenge strain but not with an unencapsulated isogenic mutant of a serotype 2 strain indicating their specificity. The results indicate that a serotype 9 bacterin is less protective than a serotype 2 bacterin, most likely due to inducing only low titers of opsonizing antibodies. This might contribute to emergence of serotype 9 strains, in particular strains of this clonal complex, in Europe.     

Effect of endobronchial challenge with Actinobacillus pleuropneumoniae serotype 10 of pigs vaccinated with bacterins consisting of A. pleuropneumoniae serotype 10 grown under NAD-rich and NAD-restricted conditions

The efficacy of two bacterins containing an Actinobacillus pleuropneumoniae serotype 10 strain was evaluated. The bacterial cells constituting bacterin 1 and 2 were grown under nicotinamide adenine dinucleotide (NAD)-rich (low-adherence capacity to alveolar epithelial cell cultures) and NAD-restricted (high-adherence capacity to alveolar epithelial cell cultures) conditions, respectively. Ten pigs were vaccinated twice with the bacterin 1 and nine pigs with the bacterin 2. Ten control animals were injected twice with a saline solution. Three weeks after the second vaccination, all pigs were endobronchially inoculated with 106.5 colony-forming units (CFU) of an A. pleuropneumoniae serotype 10 strain. In the bacterin 1 and 2 group, three and two pigs died after inoculation, respectively. Only two pigs of the control group survived challenge. Surviving pigs were killed at 7 days after challenge. The percentage of pigs with severe lung lesions (> 10% of the lung affected) was 100% in the control group, 70% in the bacterin 1 group and 22% in the bacterin 2 group. Actinobacillus pleuropneumoniae was isolated from the lungs of all animals. The mean bacterial titres of the caudal lung lobes were 7.0 x 10(6) CFU/g in the control group, 6.3 x 10(5) CFU/g in the bacterin 1 group and 1.3 x 10(6) CFU/g in the bacterin 2 group. It was concluded that both bacterins induced partial protection against severe challenge. Furthermore, there are indications that the bacterin 2, containing A. pleuropneumoniae bacteria grown under conditions resulting in high in vitro adhesin, induced better protection than the bacterin 1.     

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.     

Immunologic response to Pasteurella haemolytica and resistance against experimental bovine pneumonic pasteurellosis, induced by bacterins in oil adjuvants

Immunogenicity of and protection afforded by Pasteurella haemolytica bacterins were studied in calves. Bacterins contained an aluminum hydroxide in gel (ALH) adjuvant or one of the following oil-in-water adjuvants: Freund's complete adjuvant (FCA), Freund's incomplete adjuvant (FIA), and trehalose dimycolate (TDM). On days 0 and 7, calves were vaccinated with phosphate-buffered saline solution (PBSS), a bacterin, or live P haemolytica. Transthoracic intrapulmonic challenge exposure was done on day 21. In 3 experiments, there were no significant (P greater than 0.05) differences between lung lesions induced in PBSS-or ALH bacterin-vaccinated calves. Both FCA and FIA bacterins significantly (P less than 0.05) enhanced resistance against challenge exposure. Resistance induced by FCA and FIA bacterins was comparable with that induced by vaccination with live P haemolytica. Calves vaccinated with FIA bacterin and challenge-exposed to P haemolytica at a concentration of 4.5 X 10(9) colony-forming units (4.5 times greater than used in the first 3 experiments) resisted challenge exposure similar to calves given live organisms. The TDM bacterin failed to enhance resistance. All bacterins caused a significant increase (P less than 0.05) in serum antibody to P haemolytica somatic antigens, as measured by a quantitative fluorometric immunoassay. Pasteurella haemolytica leukotoxin neutralizing antibody titers did not increase significantly (P greater than 0.05) in sera after vaccination with any bacterin. Vaccination with FCA and FIA bacterins resulted in a significant increase (P less than 0.001) in serum antibody to a carbohydrate-protein subunit of P haemolytica, as measured by an enzyme-linked immunosorbent assay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunity induced with an aluminum hydroxide-adsorbed Mycoplasma gallisepticum bacterin in chickens

The protective effect of an inactivated Mycoplasma gallisepticum (MG) bacterin was evaluated in chickens subsequently challenged intratracheally (IT) with the homologous strain. Antibody responses in sera and tracheal washings (TWs) from these chickens were determined by an enzyme-linked immunosorbent assay. A group of chickens was vaccinated intramuscularly (IM) with two doses of the bacterin containing aluminum hydroxide gel (IM + IM). Another group was vaccinated IM with the same bacterin followed by IT with bacterin lacking the adjuvant (IM + IT). Chickens of both vaccinated groups had similar levels of antibody in TWs at the time of challenge. MG was eliminated from the trachea at higher rates and inflammatory lesions in the trachea were less severe in vaccinated chickens than in unvaccinated controls. The protective effect in chickens vaccinated IM + IT was greater than that in chickens vaccinated IM + IM. Perhaps vaccinal immunity is mediated by local rather than systemic antibody responses, or perhaps resistance provided by vaccination IM + IT is conferred partly by another immune mechanism such as cell-mediated immunity.     

Cytokine expression in colostrum-deprived pigs immunized and challenged with Haemophilus parasuis

The expression of several cytokines in spleen, pharyngeal lymph nodes, lung and brain after different immunization procedures and a challenge with 5 × 10⁹ CFU of Haemophilus parasuis was compared. Five groups of colostrum-deprived pigs were used: vaccinated with (I) a bacterin, (II) an outer-membrane-protein-vaccine, (III) a recombinant transferring-binding protein B, (IV) exposed to a total dose of 10⁵ CFU, and (V) not previously immunized. All pigs in groups III and V died, while all animals in group I, most of group IV and half of group II survived until the end of the experiment. IL-1α was found in significantly higher levels (p < 0.05) in spleen, lymph nodes and brain of dead pigs, which could be explained by the major severity of lesions in these animals. However, IL-4, IL-10, TNF-α and IFN-γ were expressed in significantly higher levels by survivors (for all the four cytokines in lymph nodes; for IL-4, IL-10 and TNF-α in spleen; for IL-4, TNF-α and IFN-γ in lung, and only for TNF-α in brain), thus suggesting a role of these four cytokines in the adaptive response, which might contribute to protection against H. parasuis infection.     

Aromatic-dependent Salmonella dublin as a parenteral modified live vaccine for calves

A virulent Salmonella dublin isolate was made histidine-requiring (his-) to allow recognition. The his- derivative, SL1367 (still calf-virulent), was then given by transduction and mutation, a transposon-generated non-reverting aromatic biosynthesis (aro) defect; this defect caused loss of virulence for the mouse. The his- aro- derivative strain, SL1438, was effective as a live vaccine in mice. Twenty male Holstein calves were divided into 4 groups. Groups I, II, and III were vaccinated IM at 2 weeks and at 3 weeks of age with aromatic-dependent (aro-) S dublin strain SL1438. Groups I and III received freshly prepared vaccine and group II received lyophilized vaccine. Serious adverse reactions to the vaccination were not seen. After vaccination, the mean maximum increase in rectal temperature was 1.8 C in group I and III calves and 0.6 C in group II calves. Fewer group II calves developed diarrhea (1 of 5) or positive blood cultures (0 of 5) after vaccination compared with group I and III calves (6 of 10 and 5 of 10, respectively). Postvaccination diarrhea was mild and of short duration. Group IV was comprised of 5 nonvaccinated calves. At 5 weeks of age, all calves were challenge exposed orally. Group I, II, and IV calves were challenge exposed with 10(11) virulent S dublin SL1367. Group III was challenge exposed with 10(11) virulent S typhimurium UCD 108-11. Subsequently, fever and diarrhea (lasting 1 to 3 days), but no deaths, were observed in the vaccinated calves. Four of the 5 nonvaccinated (group IV) calves died (P less than 0.001) within 8 days after challenge exposure. Aro- S dublin SL 1438 did not cause serious adverse effects and provided protection against oral challenge exposure with either virulent S dublin or S typhimurium.     

Infectious bovine keratoconjunctivitis: subconjunctival administration of a Moraxella bovis pilus preparation enhances immunogenicity

To compare the immune response elicited by 3 routes of vaccination, 36 calves were randomly allotted to 4 groups of 9 calves each. Group I was vaccinated subconjunctivally only. Group II was vaccinated concomitantly, both subconjunctivally and in the dewlap. Group III was vaccinated in the dewlap only. Group IV was not vaccinated and served as a virulence control for the Moraxella bovis culture. Calves in groups I, II, and III were given 2 inoculations with 14 days between inoculations. Twenty-one days after the last inoculation, the ventral conjunctival sac of all calves was instilled with cells of a virulent M bovis strain. After challenge exposure, all vaccinated calves (groups I, II, and III) had evidence of enhanced resistance, compared with the nonvaccinated calves. The highest to lowest gradients of immune responsiveness were: Group I greater than or equal to group II greater than group III greater than group IV. When immune criteria, such as the percentage of diseased eyes, the mean duration of infection, the severity of corneal lesions, and the serologic response were compared, groups I and II were significantly (P less than 0.05) more resistant to challenge exposure than were groups III and IV. Group III was significantly (P less than 0.05) different from group IV in severity of lesions and in serologic response. Also, the mean duration of infection was shorter, and the percentage of diseased eyes was less in group III than in group IV (P greater than 0.10). Group I was more resistant than was group II (P less than 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute-phase protein response in pigs experimentally infected with Haemophilus parasuis

The acute-phase protein (APP) response to an infection caused by Haemophilus parasuis, the etiological agent of Glässer's disease in pigs, was characterized measuring serum concentrations of pig major acute-phase protein (pig MAP), haptoglobin (HPT), C-reactive protein (CRP) and apolipoprotein A-I (ApoA-I) in colostrum-deprived pigs. They were divided into six experimental groups: non-immunized control group (I); immunized with a non-commercial bacterin (II); with an OMP-vaccine (III); with a sublethal dose (IV); and with two commercial bacterins (V and VI). All groups were challenged intratracheally with 5 × 10⁹ CFU of H. parasuis 37 days after immunisation. The highest levels of the positive APPs (pig MAP, HPT and CRP) and the lowest levels of the negative APPs (ApoA-I) were observed in the animals that died as a consequence of the infection, both those in the non-inmunized and in the immunized groups. However, the surviving animals (all of them in groups II, V and VI, two pigs in group III, and three in group IV) showed a minor variation in APP response, mainly on day 1 post-challenge (p.c.), and then tended to recover the initial values. APP response was still less pronounced in the groups of pigs previously immunized with bacterins. In conclusion, APP response can reflect Glässer-disease ongoing, showing a correlation between the severity and duration of the clinical signs and lesions and the magnitude of changes in the APP levels.     

Effect of Endobronchial Challenge with Actinobacillus pleuropneumoniae Serotype 10 of Pigs Vaccinated with Bacterins Consisting of A. pleuropneumoniae Serotype 10 Grown under NAD‐Rich and NAD‐Restricted Conditions

The efficacy of two bacterins containing an Actinobacillus pleuropneumoniae serotype 10 strain was evaluated. The bacterial cells constituting bacterin 1 and 2 were grown under nicotinamide adenine dinucleotide (NAD)‐rich (low‐adherence capacity to alveolar epithelial cell cultures) and NAD‐restricted (high‐adherence capacity to alveolar epithelial cell cultures) conditions, respectively. Ten pigs were vaccinated twice with the bacterin 1 and nine pigs with the bacterin 2. Ten control animals were injected twice with a saline solution. Three weeks after the second vaccination, all pigs were endobronchially inoculated with 106.5 colony‐forming units (CFU) of an A. pleuropneumoniae serotype 10 strain. In the bacterin 1 and 2 group, three and two pigs died after inoculation, respectively. Only two pigs of the control group survived challenge. Surviving pigs were killed at 7 days after challenge. The percentage of pigs with severe lung lesions (>10% of the lung affected) was 100% in the control group, 70% in the bacterin 1 group and 22% in the bacterin 2 group. Actinobacillus pleuropneumoniae was isolated from the lungs of all animals. The mean bacterial titres of the caudal lung lobes were 7.0 × 10⁶ CFU/g in the control group, 6.3 × 10⁵ CFU/g in the bacterin 1 group and 1.3 × 10⁶ CFU/g in the bacterin 2 group. It was concluded that both bacterins induced partial protection against severe challenge. Furthermore, there are indications that the bacterin 2, containing A. pleuropneumoniae bacteria grown under conditions resulting in high in vitro adhesin, induced better protection than the bacterin 1.     

Evaluation of local and systemic immune responses induced by intramuscular injection of a Mycoplasma hyopneumoniae bacterin to pigs

OBJECTIVE: To evaluate immune responses induced by administration of Mycoplasma hyopneumoniae bacterin to pigs. Animals-60 healthy 7- to 10-day-old cross-bred boars. PROCEDURE: Pigs were assigned to 1 of 4 pig groups (15 pigs/group): vaccinated, challenged; vaccinated, nonchallenged; nonvaccinated, challenged; nonvaccinated, nonchallenged. Vaccinated pigs received IM injections of a mycoplasma bacterin on days 0 and 14, whereas nonvaccinated pigs received saline (0.9% NaCl) solution. Pigs in the challenged groups were inoculated intratracheally with M hyopneumoniae on day 42. Pigs were euthanatized and necropsied 41, 44, 48, and 70 days after the first vaccination, and proportion of lung surface with pneumonic lesions was determined. Percentage of lymphocyte subpopulations and number of interferon-gamma (IFN-gamma) secreting lymphocytes in blood and tissues, cytokine and antibody concentrations in bronchoalveolar lavage (BAL) fluid, and serum antibody concentrations were determined. RESULTS: Vaccination against and infection with M hyopneumoniae induced a local mucosal immune response in the respiratory tract of pigs. Proportion of lung surface with pneumonic lesions in vaccinated challenged pigs was reduced on day 70, compared with nonvaccinated challenged pigs. Vaccination stimulated the production of M hyopneumoniae-specific IFN-gamma secreting blood lymphocytes. Tumor necrosis factor-alpha concentration in BAL fluid on day 70 was increased in nonvaccinated challenged pigs, compared with vaccinated challenged pigs. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination against M hyopneumoniae induced local, mucosal, humoral, and cellular immune responses. Moreover, vaccination reduced the severity of lung lesions in challenged pigs, suggesting that mucosal antibodies, mediation of the inflammatory response, and cell-mediated immune responses are important for control of mycoplasmal pneumonia in pigs.     

Safety and efficacy of vaccination of pregnant gilts against porcine reproductive and respiratory syndrome.

OBJECTIVE: To determine the safety and efficacy of vaccination of pregnant gilts with an attenuated strain of porcine reproductive and respiratory syndrome virus (PRRSV). ANIMALS: 16 pregnant gilts. PROCEDURE: Pregnant gilts free of antibodies for PRRSV were assigned (4 gilts/group) to the following groups: group I, untreated controls; group II, vaccinated on day 60 of gestation; group III, vaccinated on day 60 of gestation and exposed to virulent PRRSV on day 90 of gestation; and group IV, exposed to virulent PRRSV on day 90 of gestation. Safety and efficacy of vaccination was evaluated by group comparisons of prenatal and postnatal survival of fetuses and pigs, respectively, and by the condition and rate of weight gain of liveborn pigs. RESULTS: Collective (prenatal and postnatal) death losses up to day 15 after farrowing (conclusion of study) were similar for groups I (7/47, 14.9%) and II (7/44, 16.9%) but were greater for group III (18/49, 36.7%) and were greater still for group IV (23/37, 62.2%). Mean body weight 15 days after farrowing was greatest for pigs in litters of group I (4.46 kg) and progressively less for the other groups (3.87, 3.76, and 2.18 kg for groups II, III, and IV, respectively). CONCLUSIONS: Using these conditions, vaccination of gilts during midgestation appeared to be safe. However, it provided only partial protection against subsequent exposure to virulent virus. CLINICAL RELEVANCE: Attenuated-PRRSV vaccines may have to be administered to naive gilts > 30 days before conception to provide maximum protection throughout gestation.     

Effect of vaccinating sows and their piglets on the development of Glässer's disease induced by a virulent strain of Haemophilus parasuis serovar 5

Ten pregnant gilts were divided into two groups of five and one group was vaccinated at 80 and 95 days of pregnancy with a commercial bacterin containing Haemophilus parasuis serovars 2, 3 and 5. Half the piglets born to each group of gilts were vaccinated at seven and 21 days of age with the same bacterin, and one week after they were weaned at five weeks, all the piglets were inoculated intratracheally with 10(6) colony-forming units of Hparasuis serovar 5. At slaughter, a significantly smaller percentage of the lungs of the pigs born to the vaccinated gilts was affected by pneumonic lesions, and significantly fewer of them had arthritic joint changes. The average daily liveweight gain of the pigs born to the vaccinated gilts was significantly greater than that of those born to the unvaccinated gilts, but the vaccination of the piglets had no effect. There was no significant difference between the feed conversion ratios of the four groups of piglets, and none between the average times they took to reach slaughter weight. The pigs born to the vaccinated gilts had higher ELISA titres to Hparasuis than those born to the unvaccinated gilts.     

Efficacy of Corynebacterium pseudotuberculosis bacterin for the immunologic protection of sheep against development of caseous lymphadenitis

The efficacy of a Corynebacterium pseudotuberculosis bacterin to protect sheep immunologically against development of caseous lymphadenitis was evaluated in controlled challenge-exposure experiments. Sixty-three mixed-breed, white-faced lambs were used. The lambs were 10 to 12 weeks old and were randomly assigned to 3 groups (21 lambs/group). Group 1 was vaccinated once, using 2 ml of a C pseudotuberculosis bacterin (given subcutaneously) in the right axillary region at the beginning of the study. Group 2 was vaccinated twice; the 1st vaccination was given at the same time that lambs in group 1 were vaccinated and the 2nd vaccination was given 4 weeks later. Group 3 (nonvaccinated controls) was given physiologic saline solution (2 ml, subcutaneously). Each lamb was challenge exposed (ie, given 2 ml of live Corynebacterium pseudotuberculosis inoculum [6 X 10(6) colony-forming units/ml], subcutaneously at 4 different sites) during the 20th week of the study. All lambs were killed and necropsied during week 33. The mean number of abscesses per lamb was 7 for group 1, 4 for group 2, and 32 for group 3. Significant differences in the size of the abscesses were not found between the groups. Results of the study indicated that the vaccine provided immunologic protection of lambs against challenge exposure to Corynebacterium pseudotuberculosis.     

Haemophilus somnus Infections II. A Canadian Field Trial of a Commercial Bacterin: Clinical and Serological Results

To evaluate the efficacy of a Haemophilus somnus bacterin a total of 1114 beef calves or yearling bulls were used in the province of Saskatchewan. The six herds were included in a vaccination trial in which the vaccine was administered subcutaneously in one or two doses. The prevalence of H. somnus in nasal swabs of these animals at the time of the initial vaccination was 0.35% Postvaccination information on morbidity and mortality for a four month period was requested from the five ranches where there were nonvaccinated control calves. Postvaccination outbreaks of infectious thromboembolic meningoencephalitis occurred in two of these herds and, although the numbers were limited, there was a trend to reduced morbidity and mortality in the vaccinated animals compared to controls. Seroconversion rates, as determined by the complement fixation test, in the six herds were 28.3% for control calves, 57% for animals vaccinated once and 80.3% for animals vaccinated twice. On the basis of these results the bacterin was considered to be sufficiently efficacious to warrant its further evaluation under field conditions.     

Effect of levamisole on the clinical and immunologic responses to oral vaccine of Treponema hyodysenteriae

Conventionally raised crossbred Hampshire pigs were vaccinated orally with attenuated Treponema hyodysenteriae in combination with an anthelmintic, levamisole or dichlorvos. Pigs in group I (n = 9) were treated with levamisole and vaccinated with attenuated T hyodysenteriae and those in group II (n = 9) were treated with levamisole and permitted to commingle (contact exposure) with group I. Pigs in group III (n = 9) were vaccinated in a similar manner and were treated with dichlorvos. Pigs in group IV (n = 9) were treated with dichlorvos and permitted to commingle with group III. Control pigs (group V; n = 9) were not given any anthelmintic, nor were they vaccinated; they were housed separately. During the 8-week interval between vaccination and challenge inoculation, 4 total days and 8 total days of diarrhea were observed in pigs in groups I and II, respectively. Likewise, 5 total days and 10 total days of diarrhea were seen in groups III and IV, respectively. In all groups, the pigs tended to shed the organism in their feces after they were vaccinated or challenge inoculated, as determined by a fluorescent antibody technique (FAT) and culture procedure (CP). Overall mean shedding patterns of 5.5% and 24.5% identified by CP and FAT, respectively, were seen in the 2 levamisole-treated groups (I and II). In contrast, mean shedding patterns of 4% and 18% of the isolation attempts were detected by CP and FAT, respectively, in the 2 dichlorvos-treated groups. Diarrhea and shedding of T hyodysenteriae in the controls (group V) did not occur.(ABSTRACT TRUNCATED AT 250 WORDS)     

The pathology and pathogenesis of pleural adhesions in sheep

Pleural adhesions in 155 young (3 to 15 months old) and 474 older sheep were examined macroscopically and by light microscopy. The pulmonary tissue under the adhesions was also examined. Two major types of adhesions were encountered, and were called type I and type II adhesions. Stages in the development and resolution of the type I adhesions were called fibrinous, early dense, dense and thin. Except for abnormalities of the blood circulatory system, the type I adhesions were similar to those in experimental models. Type II adhesions were proliferative lesions with villous projections, strands and nodules. Abnormality of the blood circulatory system also occurred in these adhesions. Most type I adhesions appeared to have developed in association-with pulmonary abscessation and pneumonia. No relationship between type II adhesions and lesions in the underlying lung was obvious.