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Abstract

Objective—To determine effects of time of administration of tilmicosin and feeding of chlortetracycline on colonization of the nasopharynx of transported cattle by Mannheimia haemolytica (MH).

Animals—454 steers (body weight, 200 kg).

Procedure—3 studies included 4 truckloads of steers assembled and processed in the southeastern United States. For each truckload of steers, a third received tilmicosin before transportation (PRIOR), then all were transported to a feedlot in New Mexico (23 hours). At arrival (day 0), another third received tilmicosin (ARR). The remaining third did not receive tilmicosin (control steers [CTR]). Steers in studies 1 and 2 were housed in a feedlot, and steers in study 3 were housed on wheat pasture. One half of the steers from each group in studies 2 and 3 were fed chlortetracycline on days 5 to 9. Steer with signs of respiratory tract disease were treated. Nasal swab specimens were examined for MH to determine colonization.

Results—PRIOR and ARR steers had a lower incidence of respiratory tract disease and MH colonization than CTR steers, but PRIOR and ARR steers did not differ. Feeding chlortetracycline did not have an effect.

Conclusions and Clinical Relevance—Tilmicosin can inhibit MH from colonizing the nasopharynx of cattle. Because tilmicosin inhibits the growth of MH in the respiratory tract, medication with tilmicosin prior to transport should reduce the incidence of acute respiratory tract disease during the first week at the feedlot when calves are most susceptible to infectious organisms. (Am J Vet Res 2000;61: 1479–1483)

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in American Journal of Veterinary Research

Summary

Four healthy calves were inoculated with Pasteurella haemolytica serotype 1 by instillation of a broth culture into the middle nasal meatus of the left nostril. Four weeks later, calves were exposed to infectious bovine rhinotracheitis virus by aerosol into both nostrils. All calves became ill, from approximately day 3 through day 10 after virus exposure, and shed increased amounts of nasal mucus. Two calves were induced to shed P haemolytica by the virus infection, and 2 calves required reinoculation with P haemolytica for nasal passages to become actively colonized.

Elastase activity in nasal mucus increased about 15-fold within 3 days and peaked about 60-fold over baseline by 7 days after virus exposure. Activity of N-acetyl-β-d-glucosaminidase, a measure of cell damage and serum leakage, increased slightly by day 3 and reached plateau on day 5, almost threefold over baseline activity. Protein and carbohydrate content increased at a rate similar to that of N-acetyl-β-d-glucosaminidase activity with about 12-fold and sixfold increases, respectively. None of the variables returned to baseline by 19 days after virus exposure. Increased elastase activity preceded colonization by P haemolytica and decreasing elastase activity preceded decreasing P haemolytica concentration in the nasal secretions. A causal relation between elastase activity and P haemolytica colonization could be mediated by cleavage of epithelial cell surface fibronectin and exposure of receptors.

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in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of intranasal exposure to live leukotoxin (LktA)-deficient Mannheimia haemolytica (MH) at the time of feedyard arrival on nasopharyngeal colonization by wildtype MH in calves.

Animals—200 calves.

Procedure—Calves from Arkansas (AR calves; n = 100; mean body weight, 205 kg) were purchased from an order buyer barn. Calves from New Mexico (NM calves; n = 100; mean body weight, 188 kg) were obtained from a single ranch. Calves were transported to a feedyard, where half of each group was exposed intranasally with LktA-deficient MH at the time of arrival. Calves were observed daily for respiratory tract disease (RTD), and nasal swab specimens were collected periodically to determine nasopharyngeal colonization status with MH. Serum samples were assayed for antibodies to MH.

Results—15 AR calves had nasopharyngeal colonization by wild-type MH at the order buyer barn, whereas none of the NM calves had nasopharyngeal colonization. Intranasal exposure to LktA-deficient MH elicited an increase in serum antibody titers against MH in NM calves, but titers were less in NM calves treated for RTD. Exposure of NM calves to LktA-deficient MH offered protection from nasopharyngeal colonization by wild-type MH.

Conclusions and Clinical Relevance—Exposure of calves to LktA-deficient MH elicited an increase in serum antibody titers against MH and decreased colonization of the nasopharynx by wild-type MH. Earlier exposure would likely allow an immune response to develop before transportation and offer protection from nasopharyngeal colonization and pneumonia caused by wild-type MH. ( Am J Vet Res 2003;64:580–585)

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in American Journal of Veterinary Research

Abstract

Objective—To characterize Pasteurella spp isolated from healthy pack goats and evaluate the effects of administration of a commercial Pasteurellavaccine.

Animals—45 goats.

Procedure—Pharyngeal swab specimens and blood samples were collected on day 0 before vaccination with a Pasteurella (Mannheimia) haemolytica serotype A1 bacterin. Samples were also collected from 17 goats on days 21 and 35. Isolated Pasteurella spp were assigned to biovariant groups on the basis of results of biochemical utilization tests and serotyped. Serum antibody titers were determined.

Results—Multiple strains of Pasteurellaspp were isolated from swab specimens and assigned to 30 nonhemolytic and 14 β-hemolytic biovariant groups. The most common biovariant isolated was nonhemolytic P trehalosi belonging to group 2. This strain was isolated from 41 goats. Nonhemolytic P haemolytica strains were isolated from 31 goats, whereas β-hemolytic strains of P trehalosi and P haemolytica were isolated from 8 and 35 goats, respectively. Vaccination with the A1 serotype did not affect the proportion of goats from which we isolated each biovariant group or the number of biovariant groups isolated.

Conclusion and Clinical Relevance—Multiple strains of P haemolytica and P trehalosi belonging to nonhemolytic and β-hemolytic biovariant groups were isolated from the pharynx of healthy domestic pack goats. Because hemolytic activity correlates with leukotoxin production, β-hemolytic strains may have a greater potential to cause disease in naive populations of wild ruminants. However, vaccination with an A1 serotype bacterin did not decrease the proportion of culture-positive goats. (Am J Vet Res 2002;63:119–123)

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in American Journal of Veterinary Research

Abstract

Objective

To develop a unique strain of Pasteurella haemolytica, selectable from nasopharyngeal respiratory tract secretions, that retains the ability to efficiently colonize the respiratory tract of calves.

Animals

26 calves that each weighed approximately 200 kg.

Procedure

Rifampicin-resistant mutants of P haemolytica were developed and tested for in vitro growth rate and leukotoxin production. After instillation into the tonsils of calves, an isolate that was efficient at colonizing was selected and transformed, using electroporation, with a 4.2-kilobase (kb) plasmid encoding for streptomycin resistance. This isolate was instilled into the tonsils of 4 of 14 commingled calves to examine transmission of organisms. Nasal secretion and tonsil wash specimens were collected, cultured, and examined for P haemolytica. Serum antibody concentration was measured by means of indirect hemagglutination.

Results

Selected P haemolytica organisms colonized the tonsils and nasal passages for more than 2 weeks. Exposed calves and contact calves shed the organism, which was recovered from specimens of nasal secretions and tonsil washes. The 4.2-kb plasmid was lost during in vivo colonization.

Conclusions and Clinical Relevance

The selected rifampicin-resistant P haemolytica organism colonized tonsils and nasal passages in a manner similar to the wild-type organisms. Selective media suppressed other bacterial flora to the extent that a single colony-forming unit was detectable from 200 μl of specimen, a 100-fold improvement in detection sensitivity. The selectable strain spread rapidly among commingled calves. A 4.2-kb plasmid marker was unstable when P haemolytica replicated in vivo. (Am J Vet Res 1998;59:426–430)

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in American Journal of Veterinary Research

SUMMARY

A rifampicin-resistant Pasteurella haemolytica serotype 1 with 2 added plasmids was used as a colonization-challenge strain in calves to test the resistance to colonization elicited by vaccination. Nine calves were vaccinated with a tissue culture-derived P haemolytica serotype-1 vaccine which, in a prior study, had elicited a serotype-specific inhibition of nasal and tonsillar colonization by the homologous serotype under field conditions. The vaccinates and 9 nonvaccinated control calves were exposed by tonsillar instillation with the challenge strain. The P haemolytica were enumerated in nasal secretion and tonsil wash specimens collected biweekly for 3 weeks. Rifampicin-supplemented agar medium inhibited growth of other bacterial species in the specimens and, thus, increased the sensitivity of detection of the challenge P haemolytica by 100-fold. The challenge strain retained its plasmids during the period of colonization. Inhibition of colonization was evidenced by lower frequency of isolations and fewer isolations of the challenge strain from nasal secretion and tonsil wash specimens of the vaccinates than from those of the nonvaccinates.

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in American Journal of Veterinary Research

Abstract

Objective—To determine whether increased conglutinin titers are evident in stressed calves that do not develop respiratory tract disease in feedlots,compared with respiratory tract disease, and to determine the increase in immunoconglutinin titers.

Animals—101 mixed-breed beef calves.

Procedure—Calves were processed at 4 farms of origin and allowed to remain with their dams for another 100 days. Calves from each farm were brought to a centrally located order-buyer barn. In a feedlot, 101 calves were assigned to pens and observed daily for clinical signs of acute respiratory tract disease. When sick calves were detected, they were treated with antibiotics and isolated in a pen for 4 days. Conglutinin and immunoconglutinin titers were determined for all calves.

Results—During the 28-day study, 73 calves developed respiratory tract disease, whereas 28 calves remained healthy. Mean conglutinin titers differed significantly among calves from the 4 farms. Significant differences were not detected in conglutinin titers among calves on the basis of sex, morbidity, or vaccination status against Mannheimia haemolytica at each farm, the order-buyer barn, or the feedlot on days 8, 15, and 28 after arrival. Immunoconglutinin titers in calves differed significantly among farms and morbidity status.

Conclusions and Clinical Relevance—Mean conglutinin titers in calves do not appear to be associated with the incidence of acute respiratory tract disease; however, increased immunoconglutinin titers appear to be associated with recovery of stressed calves from respiratory tract disease during the first 15 days after arrival in a feedlot. (Am J Vet Res 2000;61:1403–1409)

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in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of tilmicosin treatment on number of Pasteurella haemolytica (PH) organisms in nasal secretion specimens of calves with respiratory tract disease.

Animals—206 British mixed-breed beef calves, 2 to 5 months old.

Procedure—In 2 separate studies of outbreaks, calves (study 1, n = 101; study 2, n = 105) that developed respiratory tract disease after transport to a feedlot were treated with tilmicosin. Nasal secretion specimens were examined for PH organisms to determine the status of colonization.

Results—In both studies, PH serotypes A1 and A6 were isolated. In study 1, tilmicosin treatment eliminated or markedly reduced the number of PH organisms in calves on days 1, 4, and 5 after treatment. In study 2, tilmicosin treatment eliminated PH organisms in calves on days 1, 2, 5, and 6 after treatment.

Conclusions and Clinical Relevance—Overall, tilmicosin treatment increased the number of culture-positive calves that became culture-negative and decreased the number of culture-negative calves that became culture-positive for up to 6 days after treatment. Tilmicosin treatment decreased the number of PH organisms in nasal secretion specimens, which indicated that fewer PH organisms were available to infect the lungs or to infect other calves. By reducing colonization, prophylactic use of tilmicosin before transport or at the time of arrival at a feedlot is likely to reduce the incidence of acute respiratory tract disease in calves for the initial several days after arrival, which is the period when they are most susceptible to infectious organisms. ( Am J Vet Res 2000;61: 525–529)

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in American Journal of Veterinary Research

Abstract

Objective—To determine effects of vaccination prior to transit and prophylactic administration of florfenicol at time of arrival at a feedyard on health of cattle and colonization of the nasopharynx by Mannheimia haemolytica (MH).

Animals—121 steers from Tennessee and 84 steers from New Mexico.

Procedure—Half of the steers were vaccinated before transport to a feedyard. Steers from Tennessee were vaccinated with MH bacterin-toxoid, and steers from New Mexico were vaccinated intranasally with modified-live leukotoxin-deficient MH. Half of the vaccinates and nonvaccinates were randomly selected to receive florfenicol on arrival at the feedyard. Steers were observed daily for respiratory tract disease (RTD).

Results—Administration of florfenicol at time of arrival reduced the incidence of RTD, delayed the interval before onset of RTD, and reduced the incidence of MH colonization of the nasopharynx for at least 4 days, but vaccination did not have any effect. Vaccination elicited an increase in serum antibody titers to MH. Administration of florfenicol at time of arrival reduced the development of serum antibody titers in intranasally vaccinated steers and both groups of nonvaccinated steers, but intranasal vaccination did not affect colonization by wild-type MH.

Conclusions and Clinical Relevance—Administration of florfenicol at time of arrival decreased the incidence of MH organisms in the nasopharynx and delayed the onset of RTD. Prophylactic use of suitable antibiotics is likely to reduce the incidence of acute RTD in calves for several days after arrival at feedyards, which is the period when they are most susceptible to infectious organisms. (Am J Vet Res 2002;63:251–256)

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in American Journal of Veterinary Research

Abstract

Objectives

To follow incidence of Pasteurella haemolytica (PH) in the upper respiratory tract of healthy calves at the farm and through the marketing process, and to determine the effect of vaccination on PH colonization of the upper respiratory tract and on the incidence of respiratory tract disease (RTD).

Animals

2- to 5-month-old calves (n = 104) from 4 farms.

Procedure

Calves were vaccinated with a killed PH serotype-1 product. Nasal secretion and tonsil wash specimens were cultured for PH, and serum antibody was measured by indirect hemagglutination. Calves with RTD were treated with tilmicosin phosphate.

Results

At the feedyard, 73 calves had RTD. The incidence of RTD was significantly related to the farm of origin, and was inversely related to the PH serum titer at the farm, but was not influenced by vaccination. Isolations of PH serotype 1 however, were reduced by vaccination. The major serotypes of PH encountered were 1 and 6.

Conclusion

Vaccination can reduce the frequency of colonization of the uoper respiratory tract by PH. (Am J Vet Res 1936;57:1317-1320)

Free access
in American Journal of Veterinary Research