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Brief communication
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Peer reviewed |
Evaluating the efficacy of protocols for decontaminating
tail-clipping instruments
Roberta M. Alvarez, DVM; Jason A. Kelly; Sandra F. Amass,
DVM, PhD, Diplomate ABVP; Jessica Schneider, BS, RVT; Darryl Ragland,
DVM, PhD
Department of Veterinary Clinical Sciences, Purdue University,
1248 Lynn Hall, West Lafayette, IN 47907-1248; E-mail: amasss@purdue.edu.
Alvarez RM, Kelly JA, Amass SF, et al. Evaluating the efficacy
of protocols for decontaminating tail-clipping instruments. J
Swine Health Prod. 2002;10(5):209-211. Also
available as a PDF.
Summary
Research to determine effective protocols for decontaminating
pig-processing instruments is lacking. In this study, decontamination
of tail-clipping instruments by dipping in a chlorhexidine solution
or water was not as effective as wiping the instruments with a
clean cloth.
Keywords: swine, disinfection,
decontamination, processing, biosecurity
Received: December 17, 2001
Accepted: February 14, 2002
Despite the progress that has been made
in many areas of swine pro-duction, no one has published studies
addressing neonatal polyarthritis subsequent to pig processing
since the mid-1970's, even though it continues to be a problem.
In 1975, polyarthritis due to bacterial infections was reported
in 3.3% of pigs over 3 days of age.1 Neonatal poly-arthritis
is most commonly caused by hemolytic streptococci; however, Staphylococcus
spp, Escherichia coli, and many other bacteria may also
cause such infections.1,2
Risk factors for neonatal polyarthritis include tail docking
and teeth clipping.1,2 Thus, improper decontamination
of processing instruments may have a significant impact on pig
health. Protocols on many pork production facilities require that
instruments used in processing, such as teeth clippers, tail clippers,
and ear notchers, be decontaminated before each use. However,
strict implementation of instrument sanitation may be difficult.
Often producers neglect such procedures because they are
inconvenient. Moreover, there is no scientific evidence that these
procedures are effective.
We hypothesized that proper decontamination of processing instruments
might assist in preventing mechanical transmission of bacteria
among pigs during processing. Our premise was that efficacious
protocols should eliminate or significantly reduce numbers of
bacteria on the processing instrument. For the purposes of this
study, disinfection was defined as aerobic culture of less than
one viable bacterium per cm2 of instrument cutting
surface area.3 The objective of this study was
to determine which of the following protocols was most effective
at reducing aerobic bacterial contamination of tail-clipping instruments:
dipping instruments in a disinfectant solution; dipping instruments
in farm tap water; or wiping instruments with a clean cloth.
Materials and methods
Forty 2- to 4-day-old barrows from ten litters were randomly
allocated to three treatment groups and one control group of ten
pigs each. Each treatment group corresponded to one of three protocols,
each performed after clipping the tail of a single pig. Protocol
One consisted of dipping tail-clipping instruments for 3 seconds
in a freshly prepared solution of 2% chlor-hexidine diacetate
(Nolvasan; Fort Dodge Laboratories, Inc, Fort Dodge, Iowa) diluted
to 24 mL per liter of sterile water. Protocol Two consisted of
dipping tail-clipping instruments for 3 seconds in an unused cup
of farm tap water (chlorinated). Protocol Three consisted of wiping
tail-clipping instruments with a clean cloth laundered in Surf
Ultra laundry detergent (Lever Bros Co, Greenwich, Connecticut).
The positive control consisted of sampling untreated tail-clipping
instruments that had each been used to clip the tail of a single
pig. One individually wrapped, sterile tail-clipping instrument
(Supravet; Syrvet, Des Moines, Iowa) per pig was used to cut each
pig's tail to a length of approximately 1.9 cm. Ten repetitions
were performed for each treatment.
A standardized area (approximately 2 cm2) of each
tail-clipping instrument was sampled using a sterile cotton swab.
The sampled area included the bottom cutting edge and the surface
of the bottom blade that faced the pig's body. The top blade of
the instrument was not sampled. Swab samples were immediately
placed in individual tubes containing 2 mL of chemical broth to
inactivate residual disinfectant
(D/E Neutralizing Broth; Becton-Dickinson, Franklin Lakes, New
Jersey). The swab portion was broken off into the tube of solution
and the contents were mixed by hand agitation. Samples were placed
on cold packs in a cooler on the farm and during transport, then
refrigerated until processing. A 100-L aliquot of the original
sample was plated directly onto 5% blood agar. Additionally, serial
tenfold dilutions of original samples were made using D/E Neutralizing
Broth, and a 100-mL aliquot of each dilution was plated directly
onto 5% blood agar. Samples were incubated for 24 hours at 37°C.
Colonies of aerobic bacteria were counted and total aerobic bacterial
counts per 2 cm2 were calculated.
The resulting bacterial counts did not pass normality tests;
therefore, the Kruskal-Wallis test (nonparametric ANOVA) was the
statistical test of choice, as it is indicated to compare the
medians of three or more groups of non-parametric data sets.4
Dunn's multiple comparisons test was then used to compare the
difference in the sum of ranks between two treatments with the
expected average difference (based on the number of groups and
sample size). For all tests, P<.05 was considered statistically
significant. GraphPad InStat version 3.00 for Windows 95 (GraphPad
Software, San Diego, California) was used for statistical calculations.
Background contamination control samples were collected. Briefly,
five 3-mL aliquots, respectively, of unused farm tap water and
freshly prepared chlorhexidine diacetate solutions were cultured
as described above, except D/E broth was replaced by sterile water.
Clippers were
exposed to farrowing room air for approx-imately 3 seconds, sampled,
and processed as described above. Additionally, five unused towels
were sampled by exposing the towel to farrowing room air for approx-imately
3 seconds and then placing a 1-cm x 3-cm sample of
towel into sterile water and culturing as described above.
The prevalence of polyarthritis subsequent to treatment was
not measured in this study.
Results
Background contamination
The mean aerobic bacterial count (+/- SE) for the five tap
water samples was 692 +/- 594 colony forming units (CFU) per mL
and ranged from 0 to 3060 CFU per mL. Only one of the five water
samples was sterile. All five samples of chlorhexidine diacetate
solution were sterile. Four of five towel samples exposed to room
air were sterile. The aerobic bacterial count on the fifth towel
was 13.33 CFU per 2 cm2. The mean aerobic bacterial
count (+/- SE) on unused instruments exposed to room air was 32
+/- 12 CFU per 2 cm2 and ranged from 20 to 80 CFU per
2 cm2.
Bacterial counts on treated instruments
Variation among median aerobic bacterial counts for the treatments
was greater than expected by chance (P=.0004). There were
no differences between median bacterial counts after dipping the
instrument in chlorhexidine diacetate solution for 3 seconds or
dipping the instrument in water for 3 seconds, compared to not
treating the instrument. Wiping the instrument with a clean cloth
reduced the numbers of bacteria cultured (P<.01) compared
to not treating the instrument (Table 1).
Discussion
Many farrowing house personnel clean processing instruments
after treating each pig to minimize the risk of spreading infections
within and among litters. Common procedures include rinsing the
instruments with water or dipping them in a solution of disinfectant
after processing each pig. All treatments in this study were conducted
in the farrowing house of a commercial pork production unit. Consequently,
background contamination of tail-clipping instruments and towels
was expected and did occur. Additionally, the farm tap water used
was contaminated with bacteria and thus may have increased contamination
of the tail-clipping instruments in some cases.
The results of this study demonstrated that dipping tail-clipping
instruments in water or in a solution of chlorhexidine diacetate,
as commonly practiced in many pork production facilities, and
as implemented in this study, did not disinfect tail-clipping
instruments nor significantly reduce aerobic bacterial counts
compared to not treating instruments. Lack of disinfection using
chlorhexidine diacetate may have been the result of inadequate
contact time. A 10-minute contact time for disinfection of inanimate
objects is the label recommendation. A 10-minute contact time
was not tested in this study, so the efficaciousness of an extended
contact time is unknown and should be tested in future studies.
However, producers wishing to test the efficacy of an extended
disinfectant contact time for processing instruments can do so
by rotating multiple tail-clipping instruments, such that after
one instrument is used, it is soaked in disinfect for 10 minutes
before that instrument is reused.
These experiments demonstrated that wiping the instruments
with a clean cloth between uses was an effective means of reducing
aerobic bacterial counts on tail-clipping instruments most of
the time. Wiping the tail-clipping instrument with the cloth was
the only treatment that achieved disinfection. Disinfection occurred
in two of ten replicates using this treatment. However, the highest
bacterial count (256,000 CFU per 2 cm2) also resulted
from this treatment. In this study, wiping the contaminated blade
of the tail-clipping instrument with a clean cloth between uses
was the only treatment to significantly reduce aerobic bacterial
counts, compared to using untreated instruments. This study was
conducted in the farrowing house of a commercial farm, yet four
of five towels remained sterile after brief exposure to room air.
The towels used in this study were kept wrapped until use to prevent
contamination from facility air. Depending on farm sanitation,
towels might become increasingly contaminated and negate the beneficial
effects of this treatment. Moreover, using the same towel multiple
times might prove ineffective. Therefore, the authors recommend
that precautions be taken to protect single-use towels or unused
portions of multi-use towels on the processing cart by maintaining
them in a closed bag or container prior to use.
Implications
- Dipping tail-clipping instruments in chlorhexidine diacetate
solution or water after a single use did not significantly reduce
the median aerobic bacterial counts on the cutting blade compared
to not treating tail clippers.
- Wiping the cutting blade of processing instruments with a
clean cloth between uses provided an effective method for reducing
the median aerobic bacterial counts on tail-clipping instruments
most of the time.
Acknowledgements
This project was funded by the National Pork Board.
References - refereed
1. Nielsen NC, Bille N. Preweaning mortality in pigs. 7. Polyarthritis.
Nordisk Veterinaermedicin. 1975;27:529-543.
2. Riising HJ, Nielsen NC. Streptococcal infection in sucking
pigs.1. Epidemiological investigations. Nordisk Veterinaermedicin.
1976;28:65-79.
3. Tamasi G. Testing disinfectants for efficacy. Res sci
tech Off In Epiz.1995;14(1):75-79.
4. Motulsky H. Comparing three or more means: analysis of variance.
Intuitive Biostatistics. New York, New York: Oxford University
Press; 1995:255-262.
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