The effect of Plasmodium gallinaceum on a challenge infection with Ascaridia galli in chickens

The effect of a primary infection with the haemoparasite Plasmodium gallinaceum on the establishment of a challenge infection with the nematode Ascaridia galli in chickens was studied. Four groups were infected as follows. Group 1: inoculated intravenously with 10(6) P. gallinaceum-infected erythrocytes on day 0; group 2: orally infected with 500 embryonated A. galli eggs on day 10; group 3: infected with P. gallinaceum on day 0 and A. galli on day 10; and group 3: non-infected control birds. The results of this investigation demonstrates that a primary infection with P. gallinaceum in chickens alters the course of a subsequent infection with A. galli. Thus, an antagonistic effect was seen in which the malaria infection caused a significant reduction on the establishment of the nematode in concurrently infected animals.     

The Relationship of Erythrocyte Age and Parasitization with Plasmodium gallinaceum in Chickens

Erythrocyte labeling by random and cohort techniques was used to study erythrocyte survival in normal chickens and in chickens infected with Plasmodium gallinaceum. White Leghorn chickens, eight weeks of age, were used in this series of experiments.

In chickens given P. gallinaceum on the day following erythrocyte labeling there was destruction of labeled erythrocytes at a much more rapid rate than would result from normal ageing processes. Chickens given P. gallinaceum 12, 18 and 21 days after the labeling of the erythrocytes failed to show any greater destruction of the labeled red cells beyond that resulting from normal senescence. This result indicates that erythrocytes over 12 days of age are not destroyed by P. gallinaceum.

     

Live attenuated vaccine-based control of necrotic enteritis of broiler chickens

A vaccine for necrotic enteritis (NE) of chickens would reduce the current need to prevent or treat the disease in broiler chickens with antimicrobial drugs. The objective of this study was to understand aspects of immunity to the disease. The first experiment examined the virulence of six strains of Clostridium perfringens isolated from cases of NE in broiler chickens. Using a 5-day experimental oral infection of 2-week-old broiler chickens, four of the six strains were found to be virulent. Pulsed-field gel electrophoresis and PCR showed that virulence was not associated with a plasmid encoding the beta2 toxin gene, cpb2, since this was present in virulent and one of the two avirulent strains. In the second experiment, two virulent and one avirulent strains were tested for their ability to immunize ("infection-immunization") chickens through the oral route. The procedure used experimental infection for 5 days followed by bacitracin treatment for 9 days, and then re-challenge 2 days later with a virulent strain, CP4. Infection-immunization with the virulent isolates protected chickens from subsequent virulent challenge, whereas the infection-immunization with the avirulent isolate did not. In a third experiment, two of four alpha-toxin-negative mutants of CP4 protected birds from experimental NE after oral immunization. These two mutants were also attenuated for virulence. We conclude that it is possible to immunize chickens successfully against NE and that immunogen(s) other than alpha-toxin are important in protective immunity against oral infection.     

Vaccinating chickens against avian influenza with fowlpox recombinants expressing the H7 haemagglutinin

OBJECTIVE: To evaluate the vaccine efficacy of a fowlpox virus recombinant expressing the H7 haemagglutinin of avian influenza virus in poultry. PROCEDURE: Specific-pathogen-free poultry were vaccinated with fowlpox recombinants expressing H7 or H1 haemagglutinins of influenza virus. Chickens were vaccinated at 2 or 7 days of age and challenged with virulent Australian avian influenza virus at 10 and 21 days later, respectively. Morbidity and mortality, body weight change and the development of immune responses to influenza haemagglutinin and nucleoprotein were recorded. RESULTS: Vaccination of poultry with fowlpox H7 avian influenza virus recombinants induced protective immune responses. All chickens vaccinated at 7 days of age and challenged 21 days later were protected from death. Few clinical signs of infection developed. In contrast, unvaccinated or chickens vaccinated with a non-recombinant fowlpox or a fowlpox expressing the H1 haemagglutinin of human influenza were highly susceptible to avian influenza. All those chickens died within 72 h of challenge. In younger chickens, vaccinated at 2 days of age and challenged 10 days later the protection was lower with 80% of chickens protected from death. Chickens surviving vaccination and challenge had high antibody responses to haemagglutinin and primary antibody responses to nucleoprotein suggesting that although vaccination protected substantially against disease it failed to completely prevent replication of the challenge avian influenza virus. CONCLUSION: Vaccination of chickens with fowlpox virus expressing the avian influenza H7 haemagglutinin provided good protection against experimental challenge with virulent avian influenza of H7 type. Although eradication will remain the method of first choice for control of avian influenza, in the circumstances of a continuing and widespread outbreak the availability of vaccines based upon fowlpox recombinants provides an additional method for disease control.     

Nonspecific innate immunity against Escherichia coli infection in chickens induced by vaccine strains of Newcastle disease virus

The objective was to test the hypothesis that vaccine strains of Newcastle disease virus (NDV) induce nonspecific immunity against subsequent infection with Escherichia coli. White leghorn chickens at 5 wk of age were vaccinated with a NDV vaccine at various days before challenge exposure with O1:K1 strain of E. coli via an intra-air sac route. Immunity was determined on the basis of the viable number of E. coli in the spleen 24 hr after the infection. Roakin strain induced significant (P < 0.05) immunity against E. coli at 4, 6, and 8 days, and La Sota strain at 2, 4, and 8 days, postvaccination. Secondary NDV vaccination administered 14 days later failed to induce immunity against E. coli when chickens were infected 1 or 5 days after the vaccination. Significant (P < 0.05) suppression of this nonspecific immunity was observed in birds treated with corticosterone, 40 mg/kg in feed, given for three consecutive days immediately prior to the bacterial exposure but not in those treated prior to the period. The results indicate that innate immunity induced by the primary NDV vaccination may significantly suppress the multiplication of E. coli in chickens for a period of 2-8 days postvaccination. The NDV-induced immunity was inhibited by corticosterone, which is known to mediate physiological responses to stress.     

Use of corticosterone and ampicillin for treatment of Streptococcus faecalis infection in chickens

Chickens were selectively bred for either high-antibody (HA) or low-antibody (LA) response to sheep erythrocytes. From 6 to 31 days after Streptococcus faecalis challenge exposure, LA-line chickens maintained a greater percentage of the prechallenge-exposure body weight and had lower heterophil-to-lymphocyte ratio than did HA-line chickens. The optimal dose of corticosterone (30 mg/kg of feed) was effective in maintaining postchallenge-exposure body weight greater than that of controls. Ampicillin (20 mg/d) alone was ineffective in almost all experiments. Treatment with 30 mg of corticosterone/kg of feed plus ampicillin resulted in increased body weight response to S faecalis infection when treatment was initiated 1 day before or 2 days after challenge exposure. Treatment with corticosterone was more effective in HA- than in LA-line chickens. Treatment before challenge exposure was more effective than treatment 2 days after challenge exposure.     

氟苯尼考与三甲氧苄啶水溶性粉对试验性鸡大肠杆菌病的疗效研究

为测定氟苯尼考与三甲氧苄啶(TMP)水溶性粉配伍应用对鸡大肠杆菌病的疗效,将试验鸡分为健康对照组、感染对照组、氟苯尼考组和氟苯尼考与TMP配伍应用的高、中、低3个剂量组。经对比治疗,试验结果表明,氟苯尼考与TMP配伍应用对大肠杆菌病的疗效(极)显著优于其他对照组,其中以中、高剂量组最明显,但3个剂量组间无显著差异,最佳配伍比例为5∶1,药物浓度为50μg/mL,即每毫升药液中含氟苯尼考42μg,TMP为8μg。     

Comparison of two infectious bursal disease vaccine strains: efficacy and potential hazards in susceptible and maternally immune birds.

Two infectious bursal disease vaccines were administered to separate groups of maternally immune and susceptible chickens at various ages. Vaccine B caused no damage to the bursae of chickens examined histologically at nine and 20 days after vaccination. The bursae of chickens given vaccine A were shown to be severely damaged when similarly examined. Both vaccines protected all the susceptible groups against challenge, but only vaccine A protected the groups of maternally immune chickens. Susceptible chickens vaccinated at one day of age with vaccine A showed a lowered response to Hitchner B1 Newcastle disease vaccine given at 14 days of age, judged by the haemagglutination-inhibition response and Newcastle disease challenge. The performance of the Newcastle disease vaccine was not affected in chickens given vaccine B. Bedding used by birds given vaccine A was shown to be capable of transmitting vaccinal virus to susceptible chickens, causing severe bursal damage.     

A comparison of the onset of protection induced by Newcastle disease virus strain B1 and a fowl poxvirus recombinant Newcastle disease vaccine to a viscerotropic velogenic Newcastle disease virus challenge

Four-week-old specific-pathogen-free white rock chickens were immunized with either a commercial recombinant fowl poxvirus-vectored Newcastle disease vaccine (FPN) expressing the hemagglutinin-neuraminidase and fusion protein genes of Newcastle disease virus (NDV) strain B1 or live NDV B1. Vaccinates and controls were challenged by eyedrop and intranasal (E/I) route with a viscerotropic velogenic NDV at 14 days postvaccination to determine the time of clearance of challenge virus. In a subsequent experiment, chickens were challenged at 3, 6, or 10 days postvaccination to determine the onset of immunity. Chickens that received a recommended field dose (1x) or a 0.01x dose of FP-N subcutaneously (s.c.) and were seropositive by hemagglutination-inhibition test at 14 days postvaccination cleared the challenge virus by 14 days postchallenge. Clinical Newcastle disease and high challenge virus titers in tissues were seen only in seronegative FP-N 0.01x dose vaccinates and controls. In a comparison of vaccination with FP-N (1x, 10(4,9) median tissue culture infective dose) s.c., B1 (10(6) median egg infective dose [EID50]) s.c., or B1 (10(6) EID50) E/I, chickens vaccinated at 6 or 10 days before challenge with all vaccines were protected against clinical disease, but only those vaccinated with B1 E/I 10 days before challenge were protected against infection with the challenge virus. Vaccination at 3 days before challenge with B1 E/I provided early protection, but severe nervous signs developed later and reduced overall protection to 60%, whereas disease in chickens vaccinated with B1 s.c. and FP-N s.c. 3 days before challenge was similar to the challenge controls.     

Resistance to velogenic Newcastle disease virus in leghorn chickens by use of prophylactic lymphokines

A group of 1-day-old commercial leghorn chickens was prophylactically treated with lymphokines obtained from lymphocyte cultures of chickens previously infected with Salmonella enteritidis (S. enteritidis-immune lymphokines [SE-ILK]) with the objective to investigate the effect of SE-ILK on development of Newcastle disease (ND) infection caused by Chimalguacan strain, a Mexican velogenic ND virus (vNDV). Clinical signs, histologic lesions, and hemagglutination-inhibition (HI) serum titers were compared with four other groups, namely, chickens without SE-ILK treatment with virus challenge; with SE-ILK without virus challenge; with nonimmune lymphokine (NILK) treatment and virus challenge; with lymphokine treatment and no virus challenge. SE-ILK was administered intraperitoneally in a dose of 0.5 ml/chicken and was followed 30 min later with the challenge of vNDV in a dose of 10(7.6) 50% embryo lethal dose/ml per bird. Birds were observed during 21 days of postchallenge. Detection of histologic changes and virus isolation procedures were carried out on the third, seventh, 14th, and 21st postinoculation days. HI tests were performed first before treatment and later on the days of histologic sample collection except on the third postinoculation day. Results showed that SE-ILK administration conferred resistance to the chickens because: 1) it significantly diminished the severity of ND infection by inhibiting appearance of clinical signs (P < 0.001), lesions (P < 0.005), and histopathologic changes (P < 0.005); 2) it decreased vNDV isolation rate from the organs (P < 0.001), and 3) it potentialized and even accelerated (P < 0.005) primary immune response by antibodies in the presence of vNDV.     

鸡痘母源抗体对重组鸡痘疫苗免疫效果的影响

为了检测抗鸡痘病毒母源抗体对喉气管炎重组鸡痘疫苗的影响,孵化一批来自禽痘病毒高免母鸡的雏鸡,采用ELISA方法检测鸡痘疫苗免疫鸡后代的血清抗体。检测结果表明,雏鸡自孵出2d开始,血清鸡痘病毒抗体水平就开始缓慢下降,到15日龄时下降至临界值,已有部分鸡开始出现抗体阴性反应;到21日龄时,全部被检血清抗体水平均转为阴性。分别于不同日龄对试验雏鸡免疫接种重组鸡痘疫苗,结果只有当鸡体内的鸡痘病毒母源抗体全部为阴性(21日龄)后免疫时才能产生可靠的保护作用,保护率达到80％以上。这说明鸡痘病毒母源抗体对重组鸡痘疫苗的效果有一定的影响,因此重组疫苗合理的首免时间应选择在3周龄以后。     

Preliminary results of an anticircumsporozoite DNA vaccine trial for protection against avian malaria in captive African black-footed penguins (Spheniscus demersus).

Captive juvenile African black-footed penguins (Spheniscus demersus) housed in an outdoor enclosure at the Baltimore Zoo have an average 50% mortality from avian malarial (Plasmodium sp.) infection each year without intense monitoring for disease and chemotherapeutic intervention. During the 1996 malaria transmission season, the safety and efficacy of an anti-circumsporozoite (CSP) DNA vaccine encoding the Plasmodium gallinaceum CSP protein against P. relictum were studied. The goal was to reduce clinical disease and death without initiating sterile immunity after release into an area with stable, endemic avian malaria. The birds were monitored for adverse clinical signs associated with vaccination, the stimulation of an anti-CSP antibody response, and protection afforded by the vaccine. The presence of P. relictum in trapped culicine mosquitoes within the penguin enclosure was monitored to assess parasite pressure. Among the vaccinated penguins, the parasitemia rate dropped from approximately 50% to approximately 17% despite intense parasite pressure, as determined by mosquito infection rate. During the year of the vaccine trial, no mortalities due to malaria occurred and no undesirable vaccination side effects occurred. This is the first trial of an antimalarial vaccine in a captive penguin colony.     

类脂作为佐剂对新城疫灭活疫苗免疫效果的影响

对免疫新城疫(ND)类脂灭活疫苗的雏鸡分别于免疫后2、7、14、21、28、35和42 d进行法氏囊、脾脏、胸腺指数测定,以注射生理盐水、ND抗原、类脂的鸡只为对照.结果表明,免疫后2～14 d,各组指数差异不显著,14 d以后,疫苗组与其他组比较差异显著,与类脂组差异不显著.表明,类脂作为佐剂用于制备ND疫苗,具有较强的免疫增强作用.     

Social stress and resistance of chicken and swine to Staphylococcus aureus challenge infections.

The purpose of this research was to determine the effect of social stress on the susceptibility of chickens and swine to Staphylococcus aureus infection. Chickens were housed under four levels of social stress. Weaned pigs remained with their litter or were housed separately. One day after some birds were placed in the high stressed environments all were challenged intravenously with S. aureus. Susceptibility was characterized by joint infection in swine and reduced weight gain in chickens. Chickens which were moved into the high stressed environments before challenge lost weight while the controls gained weight (P less than 0.001). During the three days postchallenge the most severely stressed chickens lost less than half as much body weight as did the least stressed (P less than 0.001). During the post-challenge period chickens selected for high corticosterone response in a high social stress gained weight while chickens selected for a low corticosterone response in a low stress environment lost weight (P less than 0.0001). Swine housed under a reduced level of stress (social) were more susceptible to S. aureus than those kept under higher levels of stress (P = 0.0001).     

Protective effects of sugar cane extracts (SCE) on Eimeria tenella infection in chickens

The effects of oral administration of sugar cane extracts (SCE) on Eimeria tenella oocysts infection in chickens were studied with 2 different experiments. In Experiment 1, 3-week-old inbred chickens (MHC; H.B15) were inoculated into the crop with SCE (500 mg/kg/day) for 1 day or 3 consecutive days, and then challenged with E. tenella sporulated oocysts (2 x 10(4) cells/chicken). In Experiment 2, 1-week-old chickens were orally administered SCE at the same dose for 3 consecutive days, and then initially infected with E. tenella sporulated oocysts (2 x 10(3) cells/chicken). At 2 and 3 weeks of age, these chickens were immunized intravenously with the mixed antigens of sheep red blood cells (SRBC) and Brucella abortus (BA). At 4 weeks of age, chickens were challenged with E. tenella sporulated oocysts (1 x 10(5)/chicken). Challenged chickens with E. tenella oocysts showed markedly decreased body weight gain/day, severe hemorrhage and great number of shedding oocysts in feces and high lesion scores. Oral administration of SCE and initial infection with oocysts (2 x 10 (3)/chicken) resulted in a remarkable improvement in body weight gain/day, hemorrhage, the number of shedding oocysts and lesion score, compare to other infected groups. In addition, SCE-inoculated chickens with the initial infection showed a significant increase in antibody responses against SRBC and BA and also improvement in decreased relative proportions of Bu-1a(+) and CD4( )cells in cecal tonsil lymphocytes of E. tenella-challenged chickens. Cecal tissues of chickens administered SCE and initially infected with E. tenella oocysts showed lower numbers of schizonts, gametocytes and oocysts than those of infected control chickens. These results suggest that SCE have immunostimulating and protective effects against E. tenella infection in chickens.     

Safety and efficacy of the cell-associated vaccine prepared by an attenuated infectious laryngotracheitis virus.

The safety and efficacy of the cell-associated (C-A) vaccine prepared by chicken embryo fibroblast (CEF) cells infected with the tissue-culture-modified strain of infectious laryngotracheitis (ILT) virus were studied in chickens. Over seventy percent of chickens inoculated with the C-A vaccine by the subcutaneous (S.C.) or intramuscular (I.M.) route at 1 day of age was protected against challenge with a virulent strain of ILT virus without any clinical signs. Chickens vaccinated with the C-A vaccine at 1 day of age acquired immunity within 6 days after vaccination, and the protection rate maintained more than 60% until 10 weeks post-vaccination. The C-A vaccine was invariably effective for chickens at various age. There was no evidence that the development of immunity was hindered by further vaccination with Newcastle disease and infectious bronchitis combined live vaccine. In addition, the C-A vaccine was safe when chickens were inoculated with 10 doses. In the field trials of the C-A vaccine, no adverse reaction was observed, and over 65% of vaccinated chickens was protected against the challenge of the virulent ILT virus at 8 weeks after vaccination.     

Early posthatch protection against Marek's disease in chickens vaccinated in ovo with a CVI988 serotype 1 vaccine

CVI988, a serotype 1 Marek's disease virus (MDV), was used as an in ovo vaccine in specific-pathogen-free chickens to determine if this virus induces early posthatch protection against Marek's disease as has been shown previously for turkey herpesvirus. MDV CVI988 was injected at embryonation day (ED) 17 (group 1) or at hatch (group 2). A third group (group 3) was left unvaccinated. At 1, 2, 3, 4, 5, and 7 days of age, chickens from each group were sampled and examined as follows: a) single-cell suspensions of spleen were inoculated onto chicken embryo fibroblast monolayers to isolate the virus; b) sections of bursal tissues were stained by indirect immunofluorescence assays with anti-pp38 monoclonal antibody to identify viral antigen expression; and c) chickens were exposed intra-abdominally to MDV RB1B, a virulent serotype 1 MDV. Results revealed that in chickens given MDV CVI988 at ED 17, virus and virus-encoded protein were not detected until chickens were 3 and 2 days old after hatching, respectively. Results also indicated that during the first 4 days after hatch, the chickens given MDV CVI988 at ED 17 were better protected against virulent MDV than those given MDV CVI988 at hatch (P < or = 0.001). These results suggested that MDV CVI988 proteins were adequately expressed in the embryo to initiate prehatch immunologic response. Additional efforts with more sensitive techniques than used in this study are needed to identify the nature of viral expression in embryos.     

抗菌药物联合应用对霉形体的药效学研究

本研究采用试管肉汤稀释法和棋盘法测定了１７种抗菌药物单独或几种药联合对鸡败血霉形体Ｓ＿６株（ＭＧＳ＿６）的最低抑菌和最低杀菌浓度．结果表明，ＭＧＳ＿６对北里霉素、四环素、红霉素、氟哌酸等高度敏感；四环素类与ＴＭＰ联合呈现协同作用。对实验性感染ＭＧＳ＿６的病鸡进行联合用药治疗试验，初步筛选出几个有良好治疗作用的联合用药配方。本研究是对联合应用抗菌药物治疗实验性鸡败血霉形体病进行的初步探讨，对防治本病具有一定的理论与实践意义。     

Systemic and mucosal antibody responses to selected cell surface antigens of avian pathogenic Escherichia coli in experimentally infected chickens

The immune response to four cell surface antigens of avian pathogenic Escherichia coli (APEC) was investigated as the first step in identifying vaccine candidates. F1 pilus adhesin, P pilus adhesin, aerobactin receptor protein, and lipopolysaccharide (LPS) from an O78 E. coli (strain EC99) were used as antigens. The proteins were purified as 6xhistidine-tagged recombinant proteins and LPS was purified from a phenol/water extract. Groups of 12 broiler chickens were vaccinated intranasally with the EC99 strain and challenged with the same strain 10 days later via the intra-air sac route. The chickens that survived were euthanatized 10 days postchallenge. Scores were assigned to infected chickens on the basis of lesions and recovery of the challenge E. coli. The immunoglobulin (Ig) IgG, IgA, and IgM antibodies to the four antigens were measured in serum and air sac washings in an enzyme-linked immunosorbent assay. Among the chickens that were not vaccinated prior to challenge, two died and three of the survivors were ill, whereas, of the chickens that were vaccinated prior to challenge, one died and one of the survivors became ill. After the intranasal vaccination, high antibody activity against all four antigens was associated with each Ig isotype in serum and air sac washings. IgG was the predominant isotype of Ig in air sac washings as detected by radial immunodiffusion. Chickens that were not ill after challenge had greater IgG, IgA, and IgM antibody activity against all four antigens in serum and air sac washings than did sick chickens. Thus, all of the antigens tested appear to be suitable candidates for a vaccine to protect chickens from respiratory tract infections caused by APEC.     

Effect of rutin and chloroquine on White Leghorn chickens infected with <Emphasis Type="Italic">Plasmodium (Bennettinia) juxtanucleare</Emphasis>

Plasmodium juxtanucleare is one of the agents that cause avian malaria in chickens and little is known about the treatment of the infection. The aim of this study was to compare the antimalarial activities of rutin and chloroquine in chickens infected with P. juxtanucleare after immunossuppression with corticosteroid. Antimalarial activity was verified in 33 fowls by evaluation of parasitemia levels in Giemsa-stained blood smears taken to 30 days. Rutin did not exert a reduction in parasitemia from P. juxtanucleare when compared to chloroquine treatment that kept the parasites at a low level, demonstrating its antimalarial effect. During the course of the infection, the trophozoite stage predominated (80%), followed by schizont (17%) and gametocyte (3%). Maximum parasitemia levels were recorded on day 12 in control and rutin groups. There were no significant differences in the hematocrit values, weight body or the temperature of the fowls among the groups evaluated (p > 0.05).