Studies on Survival of Pseudorabies Virus,Actinobacillus
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Peer reviewed Original research Studies on survival of pseudorabies virus, Actinobacillus pleuropneumoniae, and Salmonella serovar Choleraesuis in composted swine carcasses Josep Garcia-Siera, DVM, MS; Dale W. Rozeboom, MS, PhD; Barbara E. Straw, DVM, PhD; Brad J. Thacker, DVM, PhD; Larry M. Granger, DVM; Paula J. Fedorka-Cray, MS, MAS, PhD; Jeffrey T. Gray, MS, PhD. Summary tored daily, and samples were obtained culture negative for PRV and App. In Ex- Objective: To monitor survival of pseudo- from the carcasses for microbiologic evalu- periment Two, Sc was recovered from rabies virus (PRV), Actinobacillus ation at intervals throughout the samples collected on Composting Days 0, pleuropneumoniae (App), and Salmonella composting period. 1, and 3, but not from samples collected serovar Choleraesuis (Sc) in composted on Days 7 or 10. Results: Temperature of the composting swine carcasses. piles ranged from 27 to 51°C in Experi- Implications: Under the conditions of Methods: In Experiment One, pigs were ment One, and 27 to 62°C in Experiment these experiments, composting can be used infected with PRV, infected 2 days later Two. Composted carcasses degraded rap- to dispose of swine carcasses containing with App, and euthanized 15 to 16 hours idly. After 7 days, only bones, teeth, large PRV, App, and Sc. after App infection. Carcasses were then muscles, and portions of the hide were Keywords: swine, composting, pseudora- composted for 35 days. In Experiment physically recognizable. Muscle and bone bies, Actinobacillus pleuropneumoniae, Sal- Two, pigs were infected with Sc and were discolored, and bones were more eas- monella serovar Choleraesuis euthanized 3 days later, and carcasses were ily crushed or broken. The hide was less composted for 10 days. Compost piles collagenous and tore into several pieces were constructed inside buildings with when carcasses were extracted from piles. Received: December 8, 2000 concrete floors. In both experiments, tem- In Experiment One, tissue samples col- Accepted: March 11, 2001 perature of the composting piles was moni- lected on Composting Days 7 and 14 were n recent years, swine producers have not produce enough dead animals to justify composting is most widely used to dispose been challenged with the increasingly service by a rendering plant. Also, un- of yard waste. Recently, however, interest I difficult task of disposing of dead pigs weaned pigs and placentas have no value has been directed towards composting as a and placentas on the farm. Incineration, for rendering companies and are not col- method of dead animal disposal. burial, and rendering are frequently the lected for disposal. In addition, rendering In the US, composting of dead animals has only options. Incineration destroys patho- vehicles may serve as potential vectors of been confined primarily to poultry farms, gens, but has economical, environmental, disease as they travel from herd to herd. and aesthetic drawbacks. Burial is cheap, with fewer swine farms making use of this but not always convenient in cold climates Composting initially gained popularity practice. In several states, composting is where the ground is frozen during winter. during the 1970’s, largely because the Envi- not an approved method of carcass dis- Rendering recovers several animal by-prod- ronmental Protection Agency sponsored posal. Experimental evidence supporting its ucts and effectively controls transmissible development of specific composting tech- usefulness and safety as a means of pig car- diseases; however, not all producers have niques by the US Department of Agricul- cass disposal is lacking; therefore, regula- access to this method of disposal because of ture, primarily to treat municipal waste tions and laws governing pig carcass and logistics or the size of the farm. Frequently, water sludge or for solid waste manage- placenta composting have not been swine operations of 100 to 200 sows do ment (sewage sludge). Presently, established. Few reports exist on survival profiles of JGS: Indukern Corp, Miami, Florida 33178; DWR: Department of Animal Science, 2209 Anthony microorganisms in composting piles. Flegal Hall, Michigan State University, East Lansing, Michigan 48824-1225; BES: Department of Large 1 Animal Clinical Sciences, Michigan State University; East Lansing, Michigan 48824-1225; BJT: et al reported destruction of hemolytic Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, enteritis virus in poultry composting piles. Ames, Iowa 50011; LMG: Animal Health Division, Michigan Department of Agriculture, Lansing, Morrow et al2 reported partial destruction Michigan; PJFC, JTG: USDA-ARS-SAA, Richard Russell Research Center, Athens, Georgia. of salmonellae and total destruction of Ery- This article is available online at http://www.aasv.org/shap.html. sipelothrix rhusiopathiae and pseudorabies Garcia-Siera J, Rozeboom DW, Straw BE, et al. Studies on survival of pseudorabies virus, virus (PRV) by the heat produced in swine Actinobacillus pleuropneumoniae, and Salmonella serovar Choleraesuis in composted swine carcasses. composting piles (internal temperatures in J Swine Health Prod. 2001;9(5):225-231. excess of 60°C). In that study, salmonellae Journal of Swine Health and Production — Volume 9, Number 5 225 and Erysipelas organisms were grown in lethargy, inappetence). Lung and brain tis- from bottom to top was St-Sd-C-Sd-C-Sd- culture tubes that were sealed and buried in sue from three carcasses (controls) were C-Sd, with each layer approximately 15 cm compost piles. Nine of 15 salmonellae cul- collected immediately after euthanasia deep. Strata in Pile Two were the same as in ture tubes were culture negative when re- (Composting Day 0) to determine the Pile One, but there were only two layers of trieved on day 127 of composting, and on presence of PRV and App. The remaining carcasses. In each pile, a layer of carcasses day 177, 11 of 14 tubes were culture nega- 15 whole carcasses were placed in compost contained three whole pigs. Total carcass tive. All 18 Erysipelas tubes were culture piles and tested for viral and bacterial sur- weight was 92 kg for Pile One and 63 kg negative when withdrawn from the com- vival after composting for 7, 14, or 35 for Pile Two. The internal temperature of post pile on days 245 and 351 (9 tubes on days. the compost piles was recorded with a 90- each day). In the same study, tonsils from cm, probe-type thermometer. Temperature PRV-infected pigs, in sterile wide mouth Challenge inocula and procedures measurements were taken every 1 to 3 days glass bottles, and carcasses of four PRV- The strain of PRV used in this study was by randomly inserting the probe approxi- infected pigs, securely wrapped in plastic prepared as previously described.3 A 0.5- mately 30 to 45 cm into several areas of the biohazard bags, were placed in compost mL dose of challenge inoculum, containing pile. Early in the composting process, car- piles. After extraction from the compost 106 Tissue Culture Infective Doses (TCID) casses were struck with the probe and pro- pile on days 29 and 53, tonsillar tissue of PRV per mL, was instilled into each nos- hibited complete insertion. The thermom- samples from bottles and bagged carcasses tril over a 30-second period.3 Infectivity of eter was then inserted adjacent to the were placed in a common scintillation vial, the inoculum was confirmed by titration carcasses. After approximately 7 to 10 days stored frozen for an unspecified length of using the Crandall-Reese Feline Kidney of decomposition, the probe passed time, and used to prepare an inoculum (CRFK) cell line. through carcasses. Piles were intentionally which was injected into PRV-free sentinel aerated on Day 21, after pile temperatures An App serotype 1 strain (Shope) was pre- pigs. At the end of a 28-day observation had peaked. Contents were manually pared for intratracheal challenge as previ- period, serum samples collected from the turned and mixed using a garden shovel ously described4 and contained 10 colony pigs were negative for PRV antibodies. and fork. As a consequence, each pile was forming units (CFU) of App in 10 mL of moved from its original location to a spot While results from Morrow et al2 suggest normal saline. Pigs were anesthetized by IV immediately adjacent. Prior to this, piles that pathogenic organisms may be inacti- administration of a mixture of ketamine were aerated to an unknown but lesser ex- vated by composting, the conditions of the hydrochloride (Ketaset; Fort Dodge Labo- tent by the random temporary removal of trial did not reflect an “on-farm” situation. ratories, Ft Dodge, Iowa), 4.4 mg per kg carcasses from their respective piles when In their experiment, the pathogenic micro- BW, and xylazine hydrochloride (Rompun; samples were obtained. organisms were not directly in contact with Miles Inc, Shawnee, Kansas), 1.65 mg per the compost material, and conditions in- kg BW. The inoculum was placed in the Microbiologic techniques side the culture tubes may not have ad- trachea via percutaneous injection using an Animal tissue or compost material was col- equately reflected those surrounding an 18-gauge spinal needle. The inoculating lected on Composting Days 0, 7, 14, and infected carcass in a compost pile. The dose was confirmed by back titration on 35 to test for presence of infective microor- study reported here investigated the effect brain-heart infusion agar (BHI; Difco ganisms. Carcasses were randomly desig- of composting the carcasses of experimen- Laboratories, Detroit, Michigan ) contain- nated for sampling on Days 7 and 14. On tally infected pigs under simulated swine ing V factor (nicotinamide adenine di- Day 7, three whole pigs or their remains farm conditions in late spring to summer, nucleotide; Sigma, St Louis, Missouri) as were extracted from each pile. One 15-g in a structure with a roof and impermeable previously described.4 tissue sample was collected from the brain floor.