Penicillin is the antimicrobial for which consultation is most frequently sought through FARAD and is one of the most commonly detected drug residues in tissue and milk. This article reviews studies related to extralabel penicillin administration and provides recommendations to assist veterinarians in preventing violative residues in tissue and milk.
Allergic reactions to foods containing residue concentrations of penicillin are rare and are almost always dermatologic reactions.1 There are, however, reports2,3 of anaphylactic reactions developing after consumption of food containing penicillin residues. Pasteurization only reduces penicillin residues approximately 10% to 20%,4 and penicillin can
Amajor animal welfare issue facing the livestock industry is the care, handling, and transport of nonambulatory cattle. Consumers, researchers, practitioners, and animal protection organizations have questioned the quality of care provided to and management of nonambulatory cattle and raised questions about possible food safety concerns. Veterinarians and producers continue to be challenged with providing quality care for nonambulatory cattle. In addition, veterinarians are recognized as a credible source of information for consumers, regulators, and policy makers. Thus, it would be beneficial to provide peer-reviewed information to practitioners and others who must make clinical and policy decisions.
Objective—To determine efficacy of treatment with a
combination febantel-praziquantel-pyrantel product,
with or without vaccination with a commercial Giardia
vaccine, in dogs with naturally occurring giardiasis.
Animals—16 Beagles naturally infected with Giardia
Procedures—During phase 1, 6 dogs were treated
with the parasiticide for 3 days (4 were also vaccinated).
Four weeks later, all 6 dogs were treated with the
parasiticide again for 5 days and were bathed and
moved to clean cages after the last treatment (phase
2). Nine dogs were treated with the parasiticide for 3
(n = 4) or 5 (5) days and bathed and moved to clean
cages after the last treatment (phase 3). Fecal samples
were collected twice weekly for 24 days after
treatment and tested for cysts with a quantitative zinc
sulfate flotation technique and for Giardia antigen
with an immunoassay.
Results—Dogs in phase 1 were all shedding cysts
again by day 24. In phase 2, only 1 dog shed cysts
after treatment, and shedding was transient (day 17).
In phase 3, neither cysts nor antigen was detected in
fecal samples from 2 of 4 dogs treated for 3 days and
4 of 5 dogs treated for 5 days. In 18 of 57 (31.6%)
fecal samples, cysts were seen, but results of the
immunoassay were negative.
Conclusions and Clinical Relevance—Results suggest
that when a combination febantel-praziquantelpyrantel
product is used to treat dogs with giardiasis,
bathing and changing the environment after treatment
may be more important in preventing recurrence
than duration of treatment. (J Am Vet Med
Objective—To compare the results of regulatory
screening and confirmation assays with those of highperformance
liquid chromatography (HPLC) in the
detection of ceftiofur metabolites in the tissues of
culled dairy cattle.
Animals—17 lactating Holstein dairy cows.
Procedure—Daily IM injections of ceftiofur sodium
were administered at a dose of 2.2 mg of ceftiofur
equivalents/kg (n = 6) or 1.0 mg of ceftiofur equivalents/kg (10) for 5 days. Following withdrawal times of
12 hours (high-dose ceftiofur) and either 5 or 10 days
(low-dose ceftiofur), cows were slaughtered and liver,
kidney, and diaphragmatic muscle specimens were
harvested and analyzed by HPLC and standard regulatory
methods that included the following assays:
the swab test on premises, the fast antimicrobial
screen test, the calf antibiotic and sulfa test, and the
7-plate bioassay confirmation test.
Results—In all tissue specimens, residues of ceftiofur
and desfuroylceftiofur-related metabolites, as
measured by HPLC, were less than regulatory tolerance,
as defined by the FDA. False-positive screening
assay results were more likely for tissue specimens
that had been frozen for shipment to a federal laboratory,
compared with fresh tissue specimens that
were assayed at the slaughter establishment (23% vs
3% false-positive results, respectively).
Conclusions and Clinical Relevance—The observation
that fresh tissues had negative results on screening
assays, whereas subsets of the same tissue specimens
had false-positive results on screening assays
following freezing, suggests that freezing and thawing
interferes with microbial inhibition-based regulatory
screening assays. (Am J Vet Res 2004;65:1730–1733)