Letters to the Editor

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Varying viewpoints on travel of AVMA members to Cuba

I applaud the recent decision by the AVMA Executive Board to facilitate travel of AVMA members to Cuba to attend the 2014 Pan-American Congress of Veterinary Sciences, which will be cohosted by the Pan-American Association of Veterinary Sciences and the Scientific Veterinary Council of Cuba.1

I recognize and appreciate the concerns this decision raises, given the oppressive and inhumane leadership of this island nation. Regrettably, dictatorial administrations have a long history in Cuba. However, we have much to share with our Cuban colleagues and others who will be attending this congress. Importantly, if this hemisphere is to advance in regard to veterinary medicine and associated public health practices and veterinary medical research, we must promote collaborative education, studies, practices, and research of mutual and beneficial interests.

Years ago, we shared a monumental learning experience with Cuban scientists and workers in identifying mosquito transmission of the yellow fever agent and developing control measures that led to the eradication of yellow fever from Havana and, subsequently, the Isthmus of Panama, enabling construction of the Panama Canal. It was the native-born Cuban physician Carlos Juan Finlay who, in the late 1800s, first provided experimental findings implicating mosquitos, specifically Aedes aegypti, in the transmission of the yellow fever virus. Major Walter Reed of the US Army Medical Corp and associates confirmed Finlay's theory and applied this knowledge under the leadership of William C. Gorgas to help eradicate the disease.

The world is indebted to this seminal and shared achievement in the eradication of yellow fever. I trust organizers of the Pan-American Congress of Veterinary Sciences will memorialize this historic medical discovery. The US veterinary medical profession cannot be on the sidelines.

Brigadier General Thomas G. Murnane, dvm

US Army, Retired Fort Worth, Tex

1. News. AVMA to help members travel to Havana. J Am Vet Med Assoc 2014;244:150.

I second Dr. Khuly's concerns regarding the AVMA's support of veterinarians wanting to travel to Havana to attend the 2014 Pan-American Congress of Veterinary Sciences.1 In their response, Drs. Meyer and Carlson2 suggested that the AVMA Executive Board saw this meeting as “a rare professional opportunity for US veterinarians to network with and learn from colleagues from neighboring countries…,” but I do not believe that this is sufficient reason to provide AVMA support for travel to a country with such a deplorable human rights record that has continually worked against US interests. There will be other meetings in other countries more deserving of our support. To me, the AVMA's support is a political statement, and I would ask that the Executive Board reconsider and reverse this action.

Leo L. Konermann Jr, dvm

Dallas, Tex

  • 1. Khuly P. AVMA support for travel to Cuba (lett). J Am Vet Med Assoc 2014;244:775.

  • 2. Meyer T, Carlson R. AVMA support for travel to Cuba: the AVMA responds (lett). J Am Vet Med Assoc 2014;244:775.

Speculation on cause of vertebral synovial cysts in rabbits

Wendy P. Feaga, dvm

Twin Oaks Animal Hospital Ellicott City, Md

In a recent report of the surgical management of vertebral synovial cysts in a rabbit,1 the authors stated that the etiology of these cysts is unknown. I wonder whether these cysts could be due to migrating Cuterebra larvae in some animals, particularly when the cysts develop during the summer.

Several summers ago, I examined several rabbits because of paraplegia that were returned 2 to 4 weeks later for treatment of one or more of these larvae, which would be located within 2 cm of the spinal canal. Anecdotally, the severity of their paresis appeared to be related to the number of Cuterebra larvae found.

1. Delamaide Gasper JA, Rylander H & Mans C, et al. Surgical management of vertebral synovial cysts in a rabbit (Oryctolagus cuniculus). J Am Vet Med Assoc 2014;244:830834.

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The authors respond:

We thank Dr. Feaga for her comments. Synovial cysts develop secondary to degenerative joint disease in the vertebral column. Histologic characteristics of the synovial cysts identified in the rabbit described in our report, including thickening of the joint capsule and degenerative changes in the adjacent bone, were comparable to changes described for other synovial cysts in the literature.1,2 There were no histologic indications of active or previous parasitic disease in the sections evaluated.

Helena Rylander, dvm

Joy A. Delamaide Gasper, dvm

Department of Medical Sciences

Christoph Mans, dr med vet

Ken R. Waller III, dvm, ms

Department of Surgical Sciences School of Veterinary Medicine University of Wisconsin Madison, Wis

Denise M. Imai, dvm, Phd

Comparative Pathology Laboratory School of Veterinary Medicine University of California-Davis Davis, Calif

  • 1. Levitski RE, Chauvet AE, Lipsitz D. Cervical myelopathy associated with extradural synovial cysts in 4 dogs. J Vet Intern Med 1999;13:181186.

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  • 2. Dickinson PJ, Sturges BK & Berry WJ, et al. Extradural spinal synovial cysts in nine dogs. J Small Anim Pract 2001;42:502509.

Experience of breathing carbon dioxide

In their recent report on the development of a method for on-site mass depopulation of pigs, Meyer et al1 conclude, “The gradual displacement application of CO2 as described in this report should be considered as one of several possible methods for mass depopulation of pigs in the event of an animal health emergency or other exigent situations,” implying that they believe their method is an acceptable method for mass depopulation of pigs. The authors cite research2 I conducted many years ago, along with several other studies, as support for their statement that other researchers have not consistently observed distress in pigs during exposure to CO2.

It is true that in my study,2 some pigs exposed to high concentrations of CO2 assumed lateral recumbency in what appeared to be a peaceful manner. However, pigs were not necessarily unconscious while recumbent and seemed to be in distress. In fact, for many pigs, exposure to 50% to 80% CO2 caused them to struggle violently or make extreme leaping movements in an apparent attempt to escape from the apparatus. Also, 20% of the pigs I studied developed what appeared to be clonic convulsive seizures when exposed to high concentrations of CO2.

In an attempt to learn more about the experience of breathing CO2, I tried breathing 5% CO2 myself. The feeling was one of suffocation, even though the background gas was oxygen, and I would never expose myself or any animal to this experience again. If CO2 is “one of several methods for mass depopulation of pigs,” I would like to learn more about the others. Carbon monoxide, which produces tissue hypoxia and lightheadedness prior to unconsciousness, is, to me, far preferable. Give me hypoxia over hypercapnia any day.

Nicholas H. Dodman, bvms

Department of Clinical Sciences Cummings School of Veterinary Medicine Tufts University North Grafton, Mass

  • 1. Meyer RE, Morrow WEM & Stikeleather LF, et al. Evaluation of carbon dioxide administration for on-site mass depopulation of swine in response to animal health emergencies. J Am Vet Med Assoc 2014;244:924933.

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  • 2. Dodman NH. Observations on the use of the Wernberg Dip-Lift carbon dioxide apparatus for pre-slaughter anaesthesia of pigs. Br Vet J 1977;133:7180.

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The authors respond:

We thank Dr. Dodman for sharing his concerns and providing an opportunity to further describe the advantages of gradual-inflow CO2 for the mass depopulation of swine, as detailed in our recent report.

Unlike Dr. Dodman's 1977 study, we used a gradual inflow of CO2 at approximately 20% of the chamber volume/min, as currently recommended by the 2013 AVMA Guidelines for the Euthanasia of Animals.1 We did not observe escape behaviors such as panicked running or climbing during the gradual inflow of CO2 into the chamber. Unconsciousness, determined as defined in the 2013 guidelines,1 occurred prior to exposure to CO2 concentrations known to produce aversion in conscious pigs or mucosal pain in other species.

Genetics likely play a role in the variability in the response to CO2. The genetic background of some pigs, especially excitable lines such as the Hampshire and German Landrace, has been associated with animals that react poorly to CO2 stunning, whereas calmer genetic lines combining the Yorkshire or Dutch Landrace breeds have much milder reactions.2 In humans, enhanced sensitivity to CO2 is genetically linked to panic disorders.3 The neural fear network, comprising the hippocampus, the medial prefrontal cortex, and the amygdala and its brainstem projections, appears to be abnormally sensitive to CO2 in these patients.4 An accidental occupational exposure to high CO2 concentrations several years ago by one of the investigators (RM) evoked feelings of breathlessness, as one might experience following a period of intense physical activity, but not suffocation.

We do not consider CO to be a practical or safe option for mass depopulation of swine. Long-term exposure to low concentrations of CO is a recognized human health hazard, especially with regard to cardiovascular disease and teratogenic effects.5 Gerritzen et al6 reviewed the use of CO for whole-house poultry depopulation during the 2003 Netherlands avian influenza outbreak. They concluded that CO provided no smoother induction of unconsciousness than did CO2 and noted that large-scale use of the gas requires strict safety regulations and procedures to minimize risk to workers.

A review of the existing methods of mass depopulation of swine is contained within our report and convincingly shows that many of these methods are inadequate in the face of exigent animal emergencies. There is no question that simply turning off the ventilation systems within a typical swine barn will eventually kill all of the animals. However, we owe the animals in our care the most humane death possible under these difficult conditions. Furthermore, the method should be reasonably safe for workers charged with carrying out this difficult task. We believe gradual-inflow CO2 meets these criteria.

Robert Meyer, dvm

Mississippi State University Mississippi State, ms

W. E. Morgan Morrow, bvsc, phd

Department of Animal Science North Carolina State University Raleigh, NC

Larry Stikeleather, phd

Biological and Agricultural Engineering North Carolina State University Raleigh, NC

Darrel K. Styles, dvm, phd

National Center for Animal Health Emergency Management USDA APHIS Veterinary Services Riverdale, Md

  • 1. AVMA guidelines for the euthanasia of animals: 2013 edition. Available at: www.avma.org/KB/Policies/Documents/euthanasia.pdf. Accessed Apr 16, 2014.

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  • 2. Grandin T. Improving livestock, poultry, and fish welfare in slaughter plants with auditing programmes. In: Grandin T, ed.Improving animal welfare: a practical approach. Wallingford, Oxfordshire, England: CAB International, 2010;160185.

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  • 3. Battaglia M, Ogliari A & Harris J, et al. A genetic study of the acute anxious response to carbon dioxide stimulation in man. J Psychiatr Res 2007;41:906917.

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  • 4. Nardi AE, Freire RC, Zin WA. Panic disorder and control of breathing. Respir Physiol Neurobiol 2009;167:133143.

  • 5. Raub JA, Mathieu-Nolf M & Hampson NB, et al. Carbon monoxide poisoning—a public health perspective. Toxicology 2000;145:114.

  • 6. Gerritzen MA, Lambooij E & Stegeman JA, et al. Slaughter of poultry during the epidemic of avian influenza in the Netherlands in 2003. Vet Rec 2006;159:3942.

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Clinical veterinarians can help protect the public's health

Veterinarians are a trusted source of information on pet selection and animal care and husbandry and play a critical role in protecting the health of both their patients and their patient's families. Recent national outbreaks of zoonotic Salmonella enterica infections have been linked to nontraditional pets, highlighting the critical role veterinarians and their staff can play in preventing disease through client education.

In August 2013, J AVMA News published an article1 discussing the need for veterinarians to be comfortable with providing care for backyard poultry, which are increasingly being regarded as pets and family members rather than production animals. At the same time, an increasing number of human S enterica outbreaks have been linked to contact with chicks, ducklings, and other live poultry.2 In 2012 and 2013, 12 national outbreaks resulting in 1,096 illnesses, 182 hospitalizations, and 3 deaths were investigated. Most people with Salmonella infections are in for an unpleasant few days of abdominal cramps and watery diarrhea. However, certain people, such as young children, seniors, pregnant women, and immunocompromised individuals, are at increased risk for developing severe illness with potentially deadly complications, including septicemia, joint infections, and meningitis. This is especially relevant for families with young children because most reported illnesses in enteric zoonotic outbreaks involve children < 10 years old. Other recent outbreaks of human Salmonella infections have been linked to contact with African dwarf frogs, hedgehogs, guinea pigs, hamsters, small turtles, and even frozen rodents used to feed reptiles.

Pet turtles remain an important source of human illnesses. They have been linked to 13 multistate S enterica outbreaks since 2006, with 8 outbreaks involving 473 illnesses and 78 hospitalizations reported in 2012 alone.3,4 Most exposures were to small turtles with shell lengths < 4 inches. Although a federal ban on the sale of small turtles was enacted in 1975,5 these popular pets remain available for sale from a variety of sources such as street vendors, flea markets, and beach souvenir shops.

As veterinarians, we do not want to dissuade people from the rewarding experience of owning pets. Although there is a right pet out there for everyone, not all pets are right for all people. Clinical veterinarians have the opportunity to educate people about the health risks associated with pets and other animals. Healthy animals can still harbor bacteria that can make humans sick, but simple steps can be taken to reduce the risk of illness from enteric zoonoses: wash hands thoroughly after touching animals or their environments, do not let young children interact with animals without supervision, do not allow animals on or around food preparation areas and sinks, and do not keep chickens inside the house. Additionally, children ≤ 5 years old and other individuals at higher risk for serious illness should not handle reptiles, amphibians, or live poultry. Free educational materials are available from the CDC.6 Together, clinical and public health veterinarians can ensure pet owners are educated about animal-associated health risks and how they can enjoy their pets without getting sick.

Colin A. Basler, dvm, mph

Stacey A. Bosch, dvm, mph

Casey Barton Behravesh, ms, dvm, drph

Division of Foodborne, Waterborne, and Environmental Diseases National Center for Emerging and Zoonotic Infectious Diseases CDC Atlanta, Ga

  • 1. Kaiser J. Chickens are moving from the henhouse to the backyard and looking for veterinary care. J Am Vet Med Assoc 2013;243:458463.

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  • 2. Behravesh CB, Brinson D & Hopkins B, et al. Backyard poultry flocks and salmonellosis: a recurring, yet preventable public health challenge [published online ahead of print Feb 20, 2014]. Clin Infect Dis doi: 10.1093/cid/ciu067.

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  • 3. National Association of State Public Health Veterinarians Animal Contact Compendium Committee 2013. Compendium of measures to prevent disease associated with animals in public settings, 2011. J Am Vet Med Assoc 2013;243:12701288.

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  • 4. Eight multistate outbreaks of human Salmonella infections linked to small turtles (final update). Available at: www.cdc.gov/Salmonella/small-turtles-03-12/index.html. Accessed Mar 3, 2014.

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  • 5. CPG Sec. 170.100. Turtles—ban on interstate and intrastate sales and distribution. Available at: www.fda.gov/ICECI/ComplianceManuals/CompliancePolicyGuidanceManual/ucm073858.htm. Accessed Mar 3, 2014.

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  • 6. CDC. Gastrointestinal (enteric) diseases from animals. Available at: www.cdc.gov/zoonotic/gi/. Accessed Mar 3, 2014.

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