Induction of systemic and mucosal immune response in cattle by intranasal administration of pig serum albumin in alginate microparticles.

Biodegradable microparticles are an efficient mucosal delivery system that protect antigens from the harsh mucosal environment and facilitate their uptake by M cells at the epithelium of mucosal-associated lymphoid tissue. In this study, we determined the systemic and mucosal immune response in calves following intranasal and oral immunization with pig serum albumin (PSA) encapsulated in alginate microparticles. The size of the particles ranged from 1 to 50 microm in diameter, with 95% of the particles being smaller than 5 microm. High levels of anti-PSA IgG1 antibodies were found in the serum, nasal secretions, and to a less extent in saliva of calves vaccinated intranasally, but not orally, with PSA-microparticles. There was no significant increase of PSA-specific IgA. A weak lymphocyte proliferative immune response was observed in peripheral blood mononuclear cells (PBMCs), and few anti-PSA antibody-secreting cells (ASC) were detected in the blood of calves immunized intranasally. The combined systemic and mucosal response observed in intranasally immunized animals may be attributed to the wide variation in the size of the alginate microparticles, with smaller particles translocating to regional lymph nodes and inducing a systemic immune response, and larger particles being retained in the NALT and inducing a mucosal immune response. The procedure presented here may be useful as an intranasal vaccine against respiratory diseases in cattle.

The efficacy of oral vaccination of mice with alginate encapsulated outer membrane proteins of Pasteurella haemolytica and One-Shot.

The goal of this study was to examine the efficacy of oral delivery of alginate encapsulated outer membrane proteins (OMP) of Pasteurella haemolytica and a commercial One-Shot vaccine in inducing protection in mice against lethal challenge with virulent P. haemolytica. We examined two alginate microsphere formulations and compared them with oral unencapsulated and subcutaneously administered vaccines. Alginate microspheres were made by the emulsion-cross-linking technique. They were examined for size, hydrophobicity, and antigen loading efficiency before they were used in the study. Mice were vaccinated by administering 200 microg of antigens in 200 microl of microspheres suspension orally or subcutaneously. One group of mice received blank microspheres and a second group was given unencapsulated antigen orally. A third and a fourth group received different formulations of alginate encapsulated antigens by oral administration. Three groups received subcutaneous inoculations (alginate encapsulated, non-adjuvanted and unencapsulated antigens, and adjuvanted One-Shot), and one group received water (naïve group). Mice were vaccinated orally for four consecutive days and challenged with P. haemolytica 5 weeks after the first vaccination. Weekly serum and feces samples were assayed for antigen specific antibodies. The number of dead mice in each group 4 days post challenge was used to compare the efficacy of the various vaccination groups. The mean volume sizes of blank alginate microsphere formulations A, and AA were 15.9, 16 and 9.2 microm, respectively. Hydrophobicity of the microspheres was evaluated by measuring contact angle on a glass slide coated with the microspheres. The contact angles on A and AA were 37.8 and 74.3 degrees, respectively. Antigen concentration in a 1:1 w/w suspension of microspheres in water was 0.9 mg/ml. Rate of death for the blank group was 42.8% whereas for groups vaccinated with antigens encapsulated in A and AA the death rates were 40 and 33.33%, respectively. The death rate in mice vaccinated with unencapsulated antigens was 55.6%. Groups vaccinated by subcutaneous inoculation showed the lowest death rate. These results show that encapsulating OMP and One-Shot in alginate microspheres improves their performance as an oral vaccine.

Intranasal vaccination of New Zealand white rabbits against pasteurellosis, using alginate-encapsulated Pasteurella multocida toxin and potassium thiocyanate extract.

OBJECTIVE: We evaluated the efficacy of intranasal administration of Pasteurella multocida toxin (PMT) and a potassium thiocyanate extract of P. multocida (CN) encapsulated in alginate microspheres, compared with unencapsulated PMT and CN antigens, in protection of rabbits against pasteurellosis. METHODS: New Zealand male rabbits (n=24) were allotted randomly into four intranasally administered vaccine groups: 1, PMT/CN; 2, microencapsulated PMT/CN with or; 3, without subcutaneous priming; and 4, empty microspheres (control). Blood samples and nasal wash specimens were collected before vaccination and one week after each vaccination (days 7, 21, 35, and 49). Rabbits were primed subcutaneously with either unencapsulated PMT/CN or aluminum hydroxide (control) (day 0), vaccinated intranasally (days 14, 28, and 42), challenged intranasally with live P. multocida (day 56), and necropsied (day 60). RESULTS: Compared with controls, PMT/CN-immunized rabbits had significantly higher concentrations of serum IgG and IgM, nasal IgG, and bronchoalveolar lavage fluid IgA and IgG against CN. Immunized rabbits had 100% survival rate and low numbers of bacteria in liver and lungs; the control group had 50% survival rate and higher numbers of bacteria (> 4x) per gram of tissue in liver and lungs. CONCLUSION: The PMT/CN microspheres stimulated systemic and mucosal immune responses similar in effectiveness (protection) to those in response to unencapsulated PMT/CN administration.

MICs of oxazolidinones for Rhodococcus equi strains isolated from humans and animals.

Eperezolid and linezolid are representatives of a new class of orally active, synthetic antimicrobial agents. The in vitro activity values (MICs) of linezolid, eperezolid, and comparator antibiotics against 102 strains of Rhodococcus equi isolated from humans and animals were determined. Linezolid was more active than eperezolid against the strains tested; premafloxacin was the most active comparator antibiotic.

Immunogenicity of antigens in boiled alginate microspheres.

Vaccine efficacy can be enhanced by delivery of antigens in synthetic microspheres. The process of antigen incorporation into microspheres can expose fragile antigens to damaging conditions, such as high temperatures, and to bacterial contamination. Maintenance of immunogenicity of several antigens and reduction of bacterial load in alginate microspheres following boiling was evaluated. Mice were immunized subcutaneously, initially and again 21 days later, with either non-boiled or boiled microspheres containing ovalbumin (OVA), a culture supernatant vaccine of Pasteurella haemolytica (PHV), or a potassium thiocyanate extract of P. multocida (PTE). Serum samples were obtained prior to immunization and at the time of euthanasia 28 days later. Culture of microspheres showed that boiling completely eliminated aerobic bacterial growth for OVA-containing microspheres, and reduced growth by a factor of 10(4) for PTE microspheres. More bacteria were cultured after boiling than before for PHV microspheres. ELISA performed on serum and intestinal lamina propria explant supernatants showed that immunogenicity of PHV microspheres was not altered by boiling. Boiled OVA microspheres were still able to stimulate a significant serum IgG anti-OVA titer in mice, but boiled PTE microspheres completely lacked immunogenicity. Elispot assays of spleens showed that only PHV microspheres were able to retain immunogenicity after boiling. Results indicate that boiling is not an effective means for reducing the bacterial load of alginate microspheres and that the process is associated with a diminution of vaccine immunogenicity.

Prevention of bacteremia in dogs undergoing dental scaling by prior administration of oral clindamycin or chlorhexidine oral rinse.

Dogs with periodontitis were used to determine the efficacy of an oral regimen of clindamycin versus chlorhexidine acetate oral rinse in reducing the total number of bacteria and the incidence of bacteremia before and after dental scaling. Aerobic and anaerobic bacteria, isolated from blood and gingival swab cultures, were identified to genus using an automated system.

Oral vaccination of animals with antigens encapsulated in alginate microspheres.

Most infectious diseases begin at a mucosal surface. Prevention of infection must therefore consider ways to enhance local immunity to prevent the attachment and invasion of microbes. Despite this understanding, most vaccines depend on parenterally administered vaccines that induce a circulating immune response that often does not cross to mucosal sites. Administration of vaccines to mucosal sites induces local immunity. To be effective requires that antigen be administered often. This is not always practical depending on the site where protection is needed, nor comfortable to the patient. Not all mucosal sites have inductive lymphoid tissue present as well. Oral administration is easy to do, is well accepted by humans and animals and targets the largest inductive lymphoid tissue in the body in the intestine. Oral administration of antigen requires protection of antigen from the enzymes and pH of the stomach. Polymeric delivery systems are under investigation to deliver vaccines to the intestine while protecting them from adverse conditions that could adversely affect the antigens. They also can enhance delivery of antigen specifically to the inductive lymphoid tissue. Sodium alginate is a readily available, inexpensive polymer that can be used to encapsulate a wide variety of antigens under mild conditions. Orally administered alginate microspheres containing antigen have successfully induced immunity in mice to enteric (rotavirus) pathogens and in the respiratory tract in cattle with a model antigen (ovalbumin). This delivery system offers a safe, effective means of orally vaccinating large numbers of animals (and perhaps humans) to a variety of infectious agents.

Induction of protective immunity in rabbits by coadministration of inactivated Pasteurella multocida toxin and potassium thiocyanate extract.

Pasteurella multocida is a bacterial pathogen that causes rhinitis (snuffles), pneumonia, otitis media, septicemia, metritis, and death in domestic rabbits. Currently, there are no effective vaccines to prevent infection by this organism. Subcutaneous (s.c.) immunization with either exotoxin or thiocyanate extracts of P. multocida induces partial protection in rabbits. Since disease begins at mucosal sites, induction of local immunity may be important in preventing systemic disease. Little is known concerning the efficacy of intranasal (i.n. ) administration of these antigens in inducing protective mucosal immunity to P. multocida in rabbits. The purpose of this study was twofold: (i) to investigate the effectiveness of vaccination with purified P. multocida toxin (PMT) and a potassium thiocyanate extract of P. multocida (CN) in combination and (ii) to evaluate the efficacy of administration of these antigens i.n. versus s.c. Forty-eight rabbits were randomly divided into eight different treatment groups. Rabbits received either one or both antigens by either s.c. or i.n. administration. Following vaccination, each group received an i.n. challenge of P. multocida. Rabbits vaccinated with both antigens i.n. or s.c. had a 100% survival rate, few or no bacteria in the liver and lungs, high serum immunoglobulin G (IgG) and IgM antibody titers, and significant numbers of IgG antibody-secreting cells (ASC) in the spleen and tracheobronchial lymph node. Rabbits vaccinated i.n. had significant nasal and bronchoalveolar lavage IgA antibody levels. Rabbits vaccinated with only one antigen, either PMT or CN, had lower antibody titers, moderate to severe liver and lung infections, and fewer ASC compared to rabbits receiving both antigens. Rabbits in the control groups had moderate to severe liver and lung infections. This study indicates that i.n. immunization with both PMT and CN induces an effective response against homologous P. multocida challenge.

Induction of pulmonary immunity in cattle by oral administration of ovalbumin in alginate microspheres.

Respiratory infectious diseases are an important cause of economic losses to the cattle industry. There is a need for an effective, easy to administer vaccine to the critical bacterial pathogens that cause pneumonia in cattle. An orally administered vaccine could be given to a large number of animals without significant stress to the animals and with minimal labor. The purpose of this study was to determine whether the oral administration of a model antigen (ovalbumin) in alginate microspheres could induce pulmonary immunity in cattle. Calves were vaccinated orally with ovalbumin (OVA) following either a subcutaneous (s.c.) or oral priming dose of OVA. Calves primed and boostered by oral administration (oral/oral) of OVA encapsulated in alginate microparticles had increased numbers of antigen-specific IgA ASCs (ASCs) in bronchoalveolar lavage (BAL) fluids. Calves that received a s.c. priming followed by an oral booster inoculation (s.c./oral) of OVA in alginate microspheres had a greater number of anti-OVA IgA, IgG1 and IgG2 ASCs in BALF. S.c./oral calves also had increased numbers of anti-OVA IgG1 ASCs in peripheral blood whereas oral/oral calves had none. S.c./oral calves had increased anti-OVA IgG1, IgG2, and IgA titers in BALF, and IgG1 and IgG2 in serum compared to both oral/oral and sham vaccinated calves. These results indicate that oral administration of antigen encapsulated in alginate microspheres results in a mucosal immune response in the respiratory tract of cattle. Furthermore, s.c. priming both enhanced the IgA response and stimulated an IgG1 and IgG2 response not seen in oral/oral calves. The difference in antibody isotype results suggest that design of the vaccination protocol can direct antibody responses as needed for a specific immunization program.

Microsphere uptake by the intestine of White Leghorn chickens.

A study was conducted to determine the effective size for latex microsphere uptake in the intestine of white leghorn chickens. Three trials were conducted in which ligated intestinal segments of anesthetized 8-wk-old chickens were injected with 0.2-, 0.5-, 2-, 6-, 10-, or 20-mu diameter fluoresceinated latex microspheres. Microspheres were counted in brush border, epithelium, and lamina propria of each intestinal segment, liver, and spleen. After 1 hr, the 0.2-, 0.5-, and 2-mu microspheres were oriented along the brush border of epithelial cells and microsphere uptake into the epithelium and lamina propria was observed in the duodenum, ileum, cecum, cecal tonsil, and colon. Uptake of microspheres of 6, 10, and 20 mu diameter into epithelium and lamina propria was not observed in any intestinal segment. Also, no microspheres of any diameter were observed in sections of liver and spleen to suggest that there was no appreciable entry of microspheres into the bloodstream within 1 hr after administration. The results indicated that uptake of microspheres by the chicken intestine is a size-dependent process with microspheres < or = 2 mu being taken up to an equal extent by most segments of intestine.

Derivation of Pasteurella multocida-free rabbit litters by enrofloxacin treatment.

Pasteurella multocida is an important bacterial pathogen of rabbits that is easily transmitted from infected does to their kits prior to weaning. Enrofloxacin, a flouroquinolone antibiotic, is effective at limiting nasal carriage of P. multocida in rabbits. To determine if enrofloxacin treatment of pregnant does infected with P. multocida can be used to produce P. multocida-free litters, groups of 3 rabbits were inoculated intranasally on day 10 of gestation with 1.0 x 10(6) P. multocida CFUs. Beginning on day 14, one group received enrofloxacin IM (5 mg kg-1, BID), and a second group received enrofloxacin in the drinking water (200 mgl-1). IM treatment continued until kindling, while PO treatment continued 1 week after kindling. A third group was infected but received only IM saline, and a fourth group was infected but not treated. In addition, a fifth group was neither infected nor treated. Culture of nasal lavage samples and tissues from does and kits showed that both routes of enrofloxacin treatment failed to completely eliminate P. multocida from does, but all kits from enrofloxacin-treated does were free from P. multocida. These results suggest that treatment does with enrofloxacin during the periparturient period may interrupt transmission of P. multocida from infected does to their kits and that this treatment may be useful for deriving Pasteurella-free rabbits from infected does.

Systemic and pulmonary immune response to intrabronchial administration of ovalbumin in calves.

Local immunization of the respiratory tract may be the best way to achieve protection against respiratory pathogens. In order to do so successfully, it is important to fully understand how the immune response to antigen administered via the respiratory route develops. We studied the respiratory and systemic immune response after subcutaneous (SC) and intrabronchial (IB) inoculation of calves with ovalbumin (OVA). Eight calves received two SC inoculations of OVA and eight other calves received two SC and three additional IB inoculations of OVA. The occurrence of OVA-specific antibodies and antibody-secreting cells (ASC) was measured over time using isotype-specific enzyme linked immunosorbent assay (ELISA) and ELISPOT. SC immunization of calves did not result in OVA-specific IgA in bronchoalveolar lavage (BAL) fluid. Subcutaneous priming followed by intrabronchial challenge caused an initial IgG1 response in the bronchoalveolar lavage fluid, followed by a large IgA response. The presence of IgG1-ASCs indicated that the IgG1 was at least partially locally produced. Most of the OVA-specific IgA in the BAL fluid was secreted by pulmonary ASCs as indicated by the large number of IgA-ASCs in BAL samples and the low serum level of OVA-specific IgA. Antigen-specific IgG1 ASCs were detectable among peripheral mononuclear cells after culture with OVA.

Enhancement of respiratory immunity to Pasteurella multocida by cholera toxin in rabbits.

Cholera toxin (CT) is a potent adjuvant for the mucosal immune system. The purpose of this study was to determine if coadministration of CT with a potassium thiocyanate extract of Pasteurella multocida (PTE) leads to enhanced anti-PTE antibody activity and increased protection of rabbits against infection with P. multocida and associated disease. Groups of rabbits were immunized intranasally on days 0, 7, and 14, with phosphate buffered saline (PBS), 200 micrograms of CT, 1.0 mg of PTE, or 1.0 mg PTE with 200 micrograms CT. Nasal lavage and serum samples were collected over 28 days after initial immunization and evaluated by ELISA for specific antibody directed against PTE. Marked increases in serum (IgG) and nasal lavage (IgA) anti-PTE antibody activity were found beginning after day 14 in rabbits immunized with PTE. Rabbits immunized with PTE and CT demonstrated further increases in this activity. Tracheobronchial lavage samples collected at the time of necropsy demonstrated a significant level of anti-PTE IgA activity in animals immunized with PTE, and coadministration with CT stimulated a further significant increase in this activity. Groups of similarly immunized rabbits were challenged 16 days after initial immunization with 5 x 10(7) CFUs of P. multocida. Nasal lavage samples were cultured for P. multocida over the next 10 days. Rabbits were euthanized within 10 days after challenge, tissues cultured for P. multocida, and histopathologic lesion severity graded using a numeric scale. Rabbits immunized with PTE survived longer, had less severe lesions of the lungs, pleura, and liver, and fewer P. multocida CFUs cultured from samples than PBS or CT controls. Coadministration of CT led to further reductions in lesion severity of those tissues and numbers of P. multocida CFUs cultured from samples. Increased nasal turbinate atrophy of rabbits immunized with PTE with or without CT was associated with increased mean survival time. In summary, coadministration of CT with PTE enhanced protective immunity to P. multocida disease and infection in rabbits.

Oral immunization of rabbits against Pasteurella multocida with an alginate microsphere delivery system.

Oral delivery of microencapsulated antigens is a potential means to vaccinate rabbits against Pasteurella multocida, a common bacterial pathogen. Groups of five rabbits were dosed orally on days 0, 7, and 14 with alginate microspheres prepared to contain no added protein, 5 mg of a potassium thiocyanate extract of P. multocida (PTE), or 5 mg of PTE with 200 micrograms of cholera toxin (CT). In addition, groups were dosed orally with 5 mg of soluble PTE with or without 200 micrograms CT, intranasally (IN) with 1 mg of soluble PTE, or with saline. Serum and nasal lavage samples collected prior to initial immunization and 10, 16, and 21 days later were assayed by ELISA for anti-PTE IgG and IgA. Strong nasal lavage IgA and serum IgG activities were found in samples from rabbits immunized with PTE IN or orally when incorporated into microspheres. Addition of CT did not significantly enhance either response. To examine the development of protective immunity, groups were similarly immunized and challenge-exposed IN on day 16 with 10(6) CFU of P. multocida. One week later, rabbits were euthanized, and specimens from the lungs, nasopharynx, liver, and inner ear were cultured for P. multocida. Less severe infections of the lung and nasopharynx developed in rabbits immunized with PTE IN or orally in microspheres, with or without added CT. In addition, culture of liver and tympanic bullae samples from these rabbits yielded growth of P. multocida less frequently compared to other P. multocida-challenged rabbits. Coadministration of CT and PTE did not significantly improve protective immunity to challenge.

Protective immunity to Pasteurella multocida heat-labile toxin by intranasal immunization in rabbits.

Heat-labile Pasteurella multocida toxin (PMT) is an important virulence factor of some isolates from rabbits. To determine whether protective immunity to PMT could be induced in rabbits by intranasal immunization with heat-inactivated PMT, we immunized groups of rabbits intranasally at days 0, 7, 14, and 21 with inactivated PMT, with or without cholera toxin, an adjuvant for the mucosal immune system. Significant increases in anti-PMT IgA in nasal lavage samples and anti-PMT serum IgG, as determined by enzyme-linked immunosorbent assay, developed within 2 weeks after initial immunization. Coadministration of cholera toxin with inactivated PMT enhanced anti-PMT activity in the samples. Rabbits similarly immunized on days 0, 7, and 14 were challenged with PMT, and tissues were graded histologically on a numeric scale of lesion severity. Immunization conferred partial protection against development of pneumonia, pleuritis, hepatic necrosis, and testicular atrophy in rabbits challenged 16 days after initial immunization. Thus, immunization with inactivated PMT stimulates a protective response to PMT challenge in rabbits that is enhanced by coadministration of cholera toxin.

Streptococcus suis infection in swine: a retrospective study of 256 cases. Part II. Clinical signs, gross and microscopic lesions, and coexisting microorganisms.

A retrospective study of 256 cases of naturally acquired Streptococcus suis infections in swine submitted to the Indiana Animal Disease Diagnostic Laboratory from 1985 to 1989 was undertaken to describe the clinical signs, lesions, and coexisting organisms associated with S. suis serotypes 1-8 and 1/2. Infected pigs generally had clinical signs and gross lesions referable to either the respiratory system or to the central nervous system (CNS), but not both. Neurologic signs were inversely related to gross lesions in the respiratory tract (R2 = -0.19, P = 0.003), as were respiratory signs and gross lesions in the CNS (R2 = -0.19, P = 0.003). Suppurative bronchopneumonia was the most common gross lesion observed (55.2%, overall). Fibrinous and/or suppurative pleuritis, epicarditis, pericarditis, arthritis, peritonitis, and polyserositis were also reported. In 68% of the pigs, other bacteria in addition to S. suis were isolated. Escherichia coli (35.0%) and Pasteurella multocida (30.0%) were the most commonly recovered bacterial agents. Mycoplasma and viral agents were identified less often, and their role in the development of streptococcosis was difficult to assess. In pigs infected with serotypes 2-5, 7, 8, and 1/2, suppurative meningitis with suppurative or nonsuppurative encephalitis, suppurative bronchopneumonia, fibrinopurulent epicarditis, multifocal myocarditis, and cardiac vasculitis were the most common microscopic lesions observed, whereas pigs infected with serotype 1 generally presented with suppurative meningitis and interstitial pneumonia. Microscopic lesions were morphologically similar among serotypes and were also similar to those reported with other pyogenic bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of an orally administered vaccine, using hydrogels containing bacterial exotoxins of Pasteurella haemolytica, in cattle.

Poly(methacrylic acid) hydrogels were tested for oral delivery of a vaccine against Pasteurella haemolytica infection in cattle. Culture supernatants of P haemolytica, the most common bacterium associated with pneumonia in cattle, were used as the antigens in the vaccine. Hydrogels containing culture supernatants were administered orally to calves. Calves were then challenge-exposed with virulent P haemolytica. Calves were euthanatized 3 days after challenge exposure. The lungs of each calf were scored for severity and size of pneumonic lesions. Results indicated that vaccinated calves had smaller, less severe pneumonic lesions and lived longer than nonvaccinated calves. These results indicated that hydrogels can be used to deliver vaccines orally to calves to enhance resistance to pneumonia caused by P haemolytica.

Interaction of Mycoplasma hyopneumoniae and Pasteurella multocida infections in swine.

To investigate the interaction between Mycoplasma hyopneumoniae and Pasteurella multocida infection, 32 pigs were randomly assigned by litter, sex, and weight to 4 treatment groups. Group-1 pigs were inoculated with M hyopneumoniae and allowed to recover from M hyopneumoniae infection. Group-2 pigs were vaccinated against M hyopneumoniae and then inoculated with M hyopneumoniae. Group-3 pigs were inoculated with M hyopneumoniae and developed clinical signs of mycoplasmosis. Group-4 pigs had never been exposed to M hyopneumoniae. All pigs were initially seronegative for M hyopneumoniae. All pigs were subsequently inoculated with P multocida and euthanatized 2 weeks later. Pasteurella multocida was isolated only from the lungs of group-3 pigs, and these pigs had a significantly higher median percentage of lung surface area affected by pneumonia than did pigs in the other groups. For group-3 pigs, percentage of lung surface area affected by pneumonia was positively correlated with the number of P multocida colonies isolated. We concluded that P multocida is not a primary respiratory pathogen in pigs, but that M hyopneumoniae infection can render the lungs susceptible to P multocida colonization and infection. Pigs recovered from or vaccinated against infection with M hyopneumoniae were resistant to P multocida infection.

Effect of spectinomycin on Escherichia coli infection in 1-day-old ducklings.

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).