Effects of tilmicosin treatment on Pasteurella haemolytica organisms in nasal secretion specimens of calves with respiratory tract disease.
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.


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


METHODS
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
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.
Frank
G H
GH
National Animal Disease Center, USDA, Agriculture Research Service, Ames, IA 50010, USA.
Briggs
R E
RE
Loan
R W
RW
Purdy
C W
CW
Zehr
E S
ES
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001831:Body Temperature; D002417:Cattle; D015169:Colony Count, Microbial; D004196:Disease Outbreaks / Q000662:veterinary; D018942:Macrolides; D008297:Male; D016978:Mannheimia haemolytica / Q000187:drug effects*; D009297:Nasal Mucosa / Q000378:metabolism / Q000382:microbiology; D009305:Nasopharynx / Q000378:metabolism / Q000382:microbiology; D012766:Pasteurellosis, Pneumonic / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D013048:Specimen Handling / Q000662:veterinary; D013781:Texas / Q000453:epidemiology; D015645:Tylosin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D018942:Macrolides; C052319:tilmicosin; D015645:Tylosin