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Synthetic oligodeoxynucleotides (ODN) containing unmethylated cytosine phosphodiester guanine (CpG) motifs (CpG-ODN) are effective immunostimulatory agents against a variety of viral, bacterial, and protozoan diseases in different animals including poultry. We have recently demonstrated that in ovo injection of CpG-ODN confers protection in neonatal chickens against bacterial septicemias. The objective of this study was to investigate the effectiveness of needle-free intrapulmonary (IPL) delivery of CpG-ODN microdroplets against Escherichia coli infection in neonatal chicks. In the present study, we used 880 chicks in total keeping 40 chicks per group. Chicks were delivered CpG-ODN or saline by IPL at the day 1 of hatch. Three days later, chicks were challenged with two doses (1 × 104 CFU, n = 20 or 1 × 105 CFU, n = 20) of E. coli. Chicks treated with CpG-ODN by the IPL route had significantly lower clinical signs and bacterial load compared to the group treated with saline ( P < 0.05). CpG-ODN-treated groups were significantly protected against E. coli septicemia. We observed dose- and exposure time-dependent immunoprotective effects of IPL CpG-ODN in chicks. We found that IPL delivery of CpG-ODN can induce protective immunity as early as 6 hr that remains effective at least until day 5 post-treatment. Moreover, there were no adverse effects of IPL delivery of CpG-ODN on growth or mortality up to 42 days of age. Based on these findings, it can be suggested that CpG-ODN delivery by IPL route can be a promising alternative to antibiotics for inducing protective immunity in chicks during the critical first week of neonatal life.

A study was conducted to evaluate the effects of ochratoxin A (OA) on Escherichia coli-challenged broiler chickens. Day-old broiler chicks were separated into two groups of 92 chicks each, with one group fed a control mash diet, and the other fed a mash diet containing 2 ppm OA. On day 14, each group was further separated into two groups, with one group inoculated with E. coli O78 (1 x 10(7) colony-forming units/0.5 ml), whereas the other group was not inoculated with E. coli. After E. coli inoculation on day 14, four birds from each group were euthanatized at 1, 2, 3, 5, 7, 10, 14, and 21 days postinoculation. Escherichia coli infection caused dullness, depression, huddling, and diarrhea. Mortality was 14.3% in chicks infected with E. coli but fed no OA. Mortality increased to 35.7% in chicks fed OA and infected with E. coli. Decreased body weight and reduced feed intake were observed in chicks fed OA, and the effects were more pronounced in chicks fed OA and infected with E. coli. Increased serum levels of aspartate aminotransferase, alanine aminotransferase, uric acid, and creatinine and decreased levels of total proteins, albumin, globulins, calcium, and phosphorus were observed in OA-fed birds. Escherichia coli infection did not cause significant alteration in any of the serum biochemical parameters. The presence of OA in poultry rations increased mortality and the severity of an E. coli infection.

Three types of Bifidobacterium thermophilum extract were prepared and fed to 2-wk-old chickens to evaluate their usefulness in enhancing the defense activity of the chickens against pathogenic Escherichia coli. All three preparations resulted in significant reduction (P < 0.05) of E. coli numbers in the lungs of the treated chicken groups compared with the control nontreated group. Besides, improvement in the survival rate was observed in the treated chicken groups, especially the one administered the enzyme-digested B. thermophilum extract sample. Concanavalin A-stimulated lymphocytes from the latter group demonstrated significantly higher proliferation activity compared with those from the control group. These results suggest that oral administration of B. thermophilum preparations may be used to enhance the resistance of chickens against E. coli infection.

Common commercial strain male broilers aged 14 days were intratracheally inoculated with 0.2 ml of 1.2 x 10(6) colony-forming units of Escherichia coli in nutrient broth and kept in a cool environment during the experiment. Ascites was produced in five surviving and two dead birds out of 50 but not in 50 mock-infected control birds. Among the 40 survivors that were infected, the erythrocyte packed cell volume (PCV) of the 10 birds with pericarditis was the same as in 21 grossly normal birds, although that of the four birds with enlarged right ventricle (RV) was high. The pericarditis caused by E. coli septicemia was not the primary cause of ascites. However, the PCV was high in some of the survivors with an enlarged RV without pericarditis, indicating overload due to the lung lesion. These data suggested that some of the birds with an enlarged RV, caused by supplying blood that was insufficiently oxygenated for the body size, suffered from ascites.

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.

An 8-yr retrospective study was conducted to evaluate the rate of Escherichia coli infection and antibiotic resistance of isolates from diseased broilers submitted for diagnosis in Trinidad from 1990 to 1997. Of a total of 906 cases of diseased birds subjected to postmortem examination, 603 (66.6%) had E. coli infection. The number of cases increased over the years from 16 in 1990 to a peak of 294 in 1996. For every year, at least 50% of all broiler cases had E. coli infection. The rate of infection was significantly higher during the rainy season (74.1 +/- 6.9%) than during the dry season (57.8 +/- 7.0%). Approximately 50% of all E. coli isolates were resistant to 9 out of a total of 11 antimicrobial drugs selected for the study. The isolates showed an increasing trend of resistance to amoxicillin, apramycin, gentamicin, nitrofurantoin, norfloxacin, and sulfamethoxazole-trimethoprim. However, only the trends of resistance to apramycin and norfloxacin were statistically significant. Overall, of the antimicrobial drugs selected, norfloxacin relatively appeared as the best choice for treatment. From this study, we conclude that the high rate of E. coli infection in broilers submitted for diagnosis along with the high resistance of isolates to antimicrobial drugs constitute a threat to the poultry industry on the island.

SUMMARY Septicemic strains of Escherichia coli cause systemic infection in chickens after the intra-airsac inoculation. We have investigated whether levels of immunity can be determined by the viable organism count in the internal organs of infected birds. The intra-airsac inoculation of 01:K1 strain caused acute systemic infection in 6 hr. The viable count was highest in the lung followed by the liver, spleen, and blood. The count was significantly (P < 0.05) lower in the liver or spleen of vaccinated birds at 6, 12, or 24 hr after inoculation than in controls. Vaccines containing various adjuvants were tested in this system, and three oilbased adjuvants demonstrated significant (P < 0.05) immunity, whereas an alum-precipitated vaccine or one without an adjuvant failed to do so compared with nonvaccinated controls. An oil-adjuvanted vaccine showed some deterioration in its immunogenicity after prolonged storage or heating at 100 C. The acute phase response induced by intravenous injection of killed 01: K1 cells or lipopolysaccharide purified from Salmonella typhimurium in aqueous suspension induced significant immunity against the E. coli infection. These results indicate that the method referred to as "in vivo viable count method" produces quantitative results in a reproducible manner and suggest that it may be used as an alternative method to mortality measurement.

Two challenge trials and one confirmation trial were conducted to evaluate the efficacy of spectinomycin in the treatment of 1-day-old ducklings infected with Escherichia coli. In the challenge trials, ducklings were injected in the right posterior thoracic air sac with 0.2 cm3 of broth containing 10(8) colony-forming units E. coli (strain O78, E38)/ml. Spectinomycin at dosage levels of 2.5 mg, 5.0 mg, and 10.0 mg of activity was injected subcutaneously 6 hours following infection. The confirmation trial was conducted to confirm the challenge trials; procedures were similar to those used in the challenge trials, except that only the 5.0 mg of activity dosage of spectinomycin was used. In both types of trials, spectinomycin-treated ducklings had significantly lower mortality and higher average weight gain, average daily gain, and feed consumption than infected unmedicated controls. These results indicate that spectinomycin is effective in treating ducks for experimentally induced colibacillosis caused by E. coli (strain O78, E38).

White leghorn chickens were given feed containing 100 mg of ascorbic acid (AA)/kg. One day later, treated chickens and a similar group of unmedicated control chickens were chilled for 1 hour at 6 C, exposed to an unusual sound, fasted, or subjected to rough handling. Heterophil:lymphocyte (H:L) ratios were determined one day later. The AA-treated birds had significantly lower H:L ratios than untreated controls. Chickens that received a diet containing AA had lower H:L ratios than controls (0.86 vs. 1.65) following administration of adrenocorticotropic hormone. Chickens fed a diet containing AA showed increased resistance to a combined Newcastle disease virus-Mycoplasma gallisepticum infection and to a secondary Escherichia coli infection, as well as to a primary E. coli challenge infection. The effects of AA and an antibacterial drug (furaltadone) were additive. In all experiments, the optimum dose of AA was 100 mg/kg of feed. There was a negative correlation between AA level in the diet and feed efficiency.

Swollen-head syndrome is a disease seen in broiler chickens between 4 and 6 weeks of age in Southern Africa. It appears to be caused by a mixed coronavirus and Escherichia coli infection. The coronavirus appears to be of a hitherto unrecorded serotype. The disease is controlled by an attenuated live-virus vaccine and antibacterial medication.