Commentary Commentaire Influenza A/H1N1 from a pig perspective Alejandro A. Nava-Ocampo, E. Yadira Velázquez-Armenta, María Alonso-Spilsbury, Daniel Mota-Rojas
s soon as the outbreak of influenza in Mexico began to be widely advertised by printed and electronic media, we became concerned about the use of the term “swine influenza.” This was aggravated by the fact that the World Health Organization (WHO) initially referred to the reported cases as “human cases of Swine Influenza A/H1N1” (URL: http://www.who.int/csr/don/2009_04_24/en/index.html). The pig was immediately stigmatized. For example, in Mexico, a swine farm located in the State of Veracruz (Gulf of Mexico) was identified as being responsible for the outbreak; this generated an angry response from the community. The consumption of pork immediately decreased. Pork from Mexico and later from Canada and the United States was banned by some countries, and Egypt announced the decision to sacrifice the total pig population. Soon after, the WHO modified its position regarding the “swine” component used in namingthe influenza outbreak, and indicated that there was no reason to avoid consuming properly cooked swine meat. Canada has publicly issued a reassurance that only healthy pigs are being slaughtered. In some Mexican towns the media reported politicians who ate swine meat in public places in order to demonstrate the safety of pork. However, we consider that the actions taken to reverse the initial damage inflicted on the production sector of the swine industry do not have any bearing on the potential damage also inflicted on the use of the pig for research purposes. When preparing this comment, we searched PubMed using the key word “piglets” and found 8926 references, 1779 (19.9%) of which had been published within the last 5 y. When the keyword “sows” was searched, we found 4212 references, 725 (17.2%) of which had been published after 2005; and when the word “pigs” was searched, we found 150 850 references, Department of Animal Production & Agriculture, Área de Investigación: Ecodesarrollo de la Producción Animal, Universidad Autónoma Metropolitana-Xochimilco, Calzada del Hueso No. 1100, Col. Villa Quietud, Coyoacán, México DF 04960, Mexico (Alonso-Spilsbury, Mota-Rojas); PharmaReasons, Toronto, Ontario (Nava-Ocampo, Velázquez-Armenta); Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario (Nava-Ocampo). Address all correspondence to Dr. Mota-Rojas; e-mail: [email protected]
Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office ([email protected]
) for additional copies or permission to use this material elsewhere. CVJ / VOL 50 / JULY 2009
Figure 1. Strict sanitary measures are in place for manipulation of piglets in the bioterium (A). On farms, a dress code and sanitary measures are used by researchers to protect both the personnel and the animals (B).
23 097 (15.3%) of which had been published after 2005. The data were corrected by subtracting the number of references found while searching the corresponding key word in combination with “guinea” to the number of manuscripts found using the key word only. These numbers roughly reflect the worldwide interest in pigs, sows, and piglets in a wide variety of research contexts, ranging from their use as a source of xenotransplants to their use as large animal models of human reproduction. Zoonotic transmission of infectious diseases, including influenza, has been extensively demonstrated. For example, in a cross-sectional study, blood samples from 42 veterinarians and 66 healthy controls were tested against 9 influenza A virus strains and significantly elevated titers were found against the H5, H6, and H7 avian influenza virus isolates among veterinarians (1). Another study evaluated the seropositivity to swine and human H1 influenza viruses in 74 swine farm owners, employees, their family members, and veterinarians in a rural area of Wisconsin, USA (2). Positive serum hemagglutination-inhibition antibody titers to swine influenza viruses . 40 were observed in 23% of the exposed population compared with 0.9% in a control group (2). Wolfe et al (3) have identified 5 intermediate stages through which a pathogen exclusively infecting wild animals may become transformed into a pathogen exclusively infecting humans. In such a process, the domestic pig may act as an intermediate host for viral infections, including the severe acute respiratory syndrome virus. Our group, consisting of persons of various professional backgrounds, and our students are constantly supervised by our veterinary staff, who are frequently involved in clinical (for undergraduate veterinary students) and research (for graduate students) activities in commercial swine farms. Our combined experience has resulted in the adoption of strict protective measures to prevent the transfer of disease from humans to pigs or vice versa. For example, in a recent study to preliminarily assess the neurofunctional consequences of piglets with asphyxia 773
C O M M E N TA I R E
at birth (4), the animals were maintained and examined in a bioterium that belongs to one of the Mexican national institutes of health and is certified by international regulatory bodies. We adhered to strict quality control and protective measures (Figure 1A). In contrast, it was not easy to convince the owners and managers of swine farms of the benefits of implementing some protective measures including dress codes for veterinarians and their students (Figure 1B), as it was considered that the farm workers would perceive these measures as indicators of a highrisk job. It was also difficult to obtain animals for experimental studies, since the pigs were already part of a commercial setting. One way to resolve the problem was to apply for grants to pay for the animals. We also ran studies that could have direct implications for improving aspects of swine production. For example, while studying the effects of oxytocin in sows at different doses (5) and at different times of parturition (6), we were able to counsel the farmers on the proper use of oxytocin and on reduction of the mortality rate for parturient sows in the participating swine farms. While running the studies, the owners, managers, and farm workers became accustomed to viewing us in surgical coats, masks and gloves, and seeing us follow strict hygiene procedures. They subsequently incorporated most of our safety recommendations relatively quickly. Pork is the second largest animal protein category worldwide, with an average consumption of 15.6 kg per capita,
just behind seafood, at 16.1 kg (http://www.albertapork.com/ news.aspx?NavigationID=2432). Therefore, the pigs will “survive” the current outbreak of influenza and remain as a major source of animal protein. It is in our best interest to ensure that this animal species also survives as an experimental animal model to resolve many unanswered scientific questions. In that context, the current outbreak of influenza A/H1N1 should stimulate us to increase our safety measures by implementing modern monitoring systems of viral infections in pigs, promoting vaccination programs among professionals and workers handling pigs, and implementing a monitoring program for viruses that may be transmitted from pigs to humans and vice versa.
References 1. Myers KP, Setterquist SF, Capuano AW, Gray GC. Infection due to 3 avian influenza subtypes in United States veterinarians. Clin Infect Dis 2007;45:4–9. 2. Olsen CW, Brammer L, Easterday BC, et al. Serologic evidence of H1 influenza swine varies infection in swine farm residents and employees. Emerg Infect Dis 2002;8:814–819. 3. Wolfe ND, Dunavan CP, Diamond J. Origins of major human infectious diseases. Nature 2007;447:279–283. 4. Orozco-Gregorio H, Mota-Rojas D, Alonso-Spilsbuty M, et al. Shortterm neurophysiologic consequences of intrapartum asphyxia in piglets born by spontaneous parturition. Int J Neurosci 2008;118:1299–1315. 5. Mota-Rojas D, Nava-Ocampo AA, Trujillo ME, et al. Dose minimization study of oxytocin in early labor in sows: Uterine activity and fetal outcome. Reprod Toxicol 2005;20:255–259. 6. Mota-Rojas D, Villanueva-García D, Velazquez-Armenta EY, et al. Influence of time at which oxytocin is administered during labor on uterine activity and perinatal death in pigs. Biol Res 2007;40:55–63.
CVJ / VOL 50 / JULY 2009