Postexposure treatment and animal rabies, Ontario, 1958-2000. (Dispatches).This paper investigates the relationship between animal rabies rabies (rā`bēz, ră`–) or hydrophobia (hī'drəfō`bēə), acute viral infection of the central nervous system in dogs, foxes, raccoons, skunks, bats, and other animals, and in and postexposure treatment (PET) in Ontario by examining the introduction of human diploid cell diploid cell: see meiosis. vaccine (HDCV HDCV human diploid cell (rabies) vaccine; see rabies vaccine. ) in 1980 and the initiation of an oral rabies vaccination program for wildlife in 1989. Introducing HDCV led to an immediate doubling of treatments. Both animal rabies and human treatments declined rapidly after the vaccination program was introduced, but human treatments have leveled off at approximately 1,000 per year. ********** Jurisdictions across North America North America, third largest continent (1990 est. pop. 365,000,000), c.9,400,000 sq mi (24,346,000 sq km), the northern of the two continents of the Western Hemisphere. have identified animal rabies as a serious public health concern (1,2) because the epidemiology of human rabies closely follows the epizoology of animal rabies (3). Recent studies have examined the relationship between animal rabies and postexposure treatment (PET) for reasons of surveillance, economic impact, epidemiology, and appropriate treatment (2,4,5). We investigated the nature of this relationship in Ontario from 1958 to 2000, focusing on the impact of two important advances in rabies prevention: a) the introduction of human diploid cell rabies vaccine human diploid cell rabies vaccine n. Abbr. HDRV Rabies vaccine composed of inactive virus prepared from fixed rabies virus cultured on human diploid cells. (HDCV) and b) the initiation of an oral rabies vaccination program (ORVP ORVP Off Road Video Productions (Beaverton, OR) ). Animal rabies has had a long and varied history in Ontario. Before the 1950s, sporadic outbreaks of rabies occurred, usually associated with dogs. In the early 1950s, a rabies epizootic ep·i·zo·ot·ic adj. Affecting a large number of animals at the same time within a particular region or geographic area. Used of a disease. ep swept southward south·ward adv. & adj. Toward, to, or in the south. n. A southward direction, point, or region. south from the Arctic, entered northern Ontario Northern Ontario is the part of the province of Ontario which lies north of Lake Huron (including Georgian Bay), the French River and Lake Nipissing. Northern Ontario has a land area of 802,000 km² (310,000 mi²) and constitutes 87% of the land area of Ontario, although it in 1954, and by 1958 became enzootic en·zo·ot·ic adj. Prevalent among or restricted to animals of a specific geographic area. Used of a disease. n. An enzootic disease. enzootic peculiar to or present constantly in a location. See also endemic. in southern Ontario in red foxes (Vulpes vulpes Vulpes vulpes see red fox. ) and striped skunks (Mephitis mephitis Mephitis mephitis see skunk. ) (6). Sylvatic sylvatic /syl·vat·ic/ (sil-vat´ik) sylvan; pertaining to, located in, or living in the woods. sylvatic found in the woods; occurring in animals of the forest. rabies has, in turn, infected companion animals and livestock, the two groups responsible for most subsequent human exposures (Honig JM, unpub. data, 1985). In 1999, the strain of raccoon raccoon, nocturnal New World mammal of the genus Procyon. The common raccoon of North America, Procyon lotor, also called coon, is found from S Canada to South America, except in parts of the Rocky Mts. and in deserts. rabies that has moved north along the eastern seaboard of the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. entered eastern Ontario Eastern Ontario is the region of the Canadian province of Ontario which lies in a wedge-shaped area between the Ottawa and St. Lawrence Rivers. It shares water boundaries with Quebec, to the north and New York State to south. Population: 1,392,346 (2001), est. from northern New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of ; by the end of 2000, there were 48 reported cases in raccoons (8 during 1999; 40 during 2000) (7). Since 1958, Ontario has averaged 1,200 to 1,300 animal cases per year, for a total of >56,000 cases by 2000. The burden on the public health system has been substantial; for example, >63,000 PETs were reported in the same period. In addition, public health officials have had to investigate all contacts between humans and animals in which rabies may have been transmitted. In the 1980s, for example, at the height of the rabies enzootic, 15,000 to 25,000 such investigations were carried out annually (8). In Canada, all animal rabies collection and laboratory diagnoses are handled by the Canadian Food Inspection Agency The Canadian Food Inspection Agency (French: Agence canadienne d'inspection des aliments), or CFIA, which was created in April 1997, brought together inspection and related services previously provided through the activities of four federal government departments (CFIA CFIA Canadian Food Inspection Agency CFIA Center For International Affairs CFIA Component Failure Impact Analysis CFIA Colegio Federado de Ingenieros y de Arquitectos (Costa Rica) CFIA Canadian Fence Industry Association ), the federal ministry responsible for establishing the collection protocols and the laboratory diagnosis of submitted specimens that were suspected of carrying Rabies virus rabies virus n. A rather large, bullet-shaped virus of the genus Lyssavirus that causes rabies. (RABV). District veterinary officers throughout the country are responsible for specimen collection and the decision to send specimens to federally operated laboratories for testing. During the study period, Ontario's Ministry of Health and Long-Term Care long-term care (LTC), n the provision of medical, social, and personal care services on a recurring or continuing basis to persons with chronic physical or mental disorders. (MOHLTC) distributed vaccine to physicians, free of charge, for the prevention of human rabies. In the fiscal year 1980-81, the ministry began distributing the newly licensed HDCV to replace earlier Semple and duck embryo vaccines. By the fiscal year 1983-84, all distributed vaccines were HDCV (9). HDCV was an important advance in rabies prevention because "it is a better immunogen with fewer side effects Side effects Effects of a proposed project on other parts of the firm. and requires far fewer doses than the previously recommended duck embryo vaccine" (10). A second important advance in rabies prevention was ORVP. In 1989, the Ontario Ministry of Natural Resources initiated an ORVP in eastern Ontario, targeting the principal wildlife vectors (11). By 1994, the ministry had extended ORVP to cover the epizootic area in southern Ontario, and over 1 million vaccine baits were dropped annually. The program resulted in a dramatic drop in rabies incidence in southern Ontario (11). Methods We gathered the PET and animal rabies data (Table) from two government agencies. The MOHLTC annual reports from 1958 to 1978 list the number of courses of rabies vaccine rabies vaccine n. 1. A vaccine introduced by Pasteur as a method of treatment for the bite of a rabid animal, consisting of 23 daily injections of virus that are increased serially from noninfective doses to doses containing fully infective distributed in each calendar year; for this paper, we considered each such course as a PET. For 1979 to 1988 and 1998 to 2000, we obtained similar records directly from internal reports in the MOHLTC. For 1989 to 1997, we obtained vaccine distribution data from the Public Health and Epidemiology Reports for Ontario (12). We obtained the annual number of laboratory-confirmed cases of animal rabies in Ontario directly from CFIA. Data were compiled on all terrestrial animals and bats that tested positive for RABV. Data on the number of negative test results were not available. Our PET and rabies data were maintained for the entire study period by two central government agencies with a consistent mandate for collecting and reporting. Unfortunately, because these two agencies operate independently, we could not match the individual human treatments to the specific specimens that tested positive for rabies. Human population data were obtained from Statistics Canada Quarterly Estimates of Population for Canada, Provinces and Territories, 1951-2000. We used regression analysis In statistics, a mathematical method of modeling the relationships among three or more variables. It is used to predict the value of one variable given the values of the others. For example, a model might estimate sales based on age and gender. to examine the relationship between PET and the number of laboratory-confirmed cases of rabies in terrestrial animals and bats in Ontario. Analyses were done for the periods 1958 to 1980 and 1981 to 2000. As previously noted, HDCV was used during the second period. We used SPSS A statistical package from SPSS, Inc., Chicago (www.spss.com) that runs on PCs, most mainframes and minis and is used extensively in marketing research. It provides over 50 statistical processes, including regression analysis, correlation and analysis of variance. (release 10.0.5, SPSS Inc., Chicago, IL) to perform the regressions. Results From 1958 to 1980, the ratio of human treatments to animal cases was <1 in most years (Table, Figure). After HDCV was introduced in 1980, the yearly ratios of human treatments to animal cases were >1. Furthermore, from 1980 to 1981, the rate of PET per 100,000 persons almost doubled. The annual number of PETs increased from an average of approximately 1,000 in the 1970s to an average of more than 2,000 per year during the 1980s. During the 1980s and early 1990s, the annual number of PETs closely paralleled the annual number of animal cases. The regression for the 1958 to 1980 period showed a weak but significant relationship between PET and animal rabies ([R.sup.2]=0.42, p<0.001, n = 23, intercept = 557 [standard error, SE, 135.4], slope = 0.358 [SE 0.092]). After 1980 the relationship was much stronger ([R.sup.2]=0.91, p<0.001, n = 20, intercept = 861 [SE 100.5], slope = 0.877 [SE 0.067]). The slopes of these regressions indicate that before 1980, there were approximately three reports of rabid animals for every PET, whereas after 1980, the ratio was approximately 1:1. Finally, the regression demonstrates that the base level of treatments after 1980 was 861, approximately 55% higher than the base level (557) before 1980. Following the initiation of ORVP, the regular cycle of animal rabies was broken in the early 1990s (Figure) and the number of laboratory-confirmed rabid animals declined. The number of human treatments also declined by 50%, from more than 2,000 per year throughout most of the 1980s to approximately 1,000 per year in the late 1990s. [FIGURE OMITTED] During the period 1968 to 1980, there was an apparent change in the relationship between PET and animal rabies compared with the initial 1958 to 1967 period of the enzootic (Figure, Table). The ratios of PET per rabid animal and PET rate per 100,000 persons for the 1958 to 1967 period were 0.9 and 16.0, respectively, and declined to mean values of 0.7 and 13.2, respectively, for the 1968 to 1980 period. Discussion There was a dramatic change in the relationship between PET and animal rabies coincident with the introduction of HDCV in 1980. Furthermore, after 1980, the positive correlation Noun 1. positive correlation - a correlation in which large values of one variable are associated with large values of the other and small with small; the correlation coefficient is between 0 and +1 direct correlation between human treatments and animal rabies strengthened. We could not find any directives from the MOHLTC or published studies indicating a change in treatment policy when HDCV was introduced. Since HDCV had fewer side effects and the vaccination regime was simpler and less traumatic than previous treatments, there was, perhaps, less reluctance to administer PET after 1980 and, therefore, the use of PET increased and paralleled the incidence of animal rabies more closely. When Ontario began its ORVP, one of the arguments for it was that animal rabies would be reduced and human treatments would follow suit. Our findings support this argument and are consistent with reports from other jurisdictions (3,13,14). The decline in human treatments in Ontario, however, was not as rapid as the decline in rabies cases. In fact, in recent years, while animal rabies incidence dropped to approximately 100 to 200 reported cases per year, PET leveled off at approximately 1,000 per year, about the same level as immediately before HDCV was introduced. We suspect the reasons for the continued high ratio of PET to animal rabies are varied and complex. For instance, with the continued presence of rabies, if a suspect animal is not available for testing, PET is administered as a precautionary measure. Furthermore, rabies in bats has been unaffected by the ORVP. Bats have been implicated im·pli·cate tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates 1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot. 2. in more than half (15 of 28 cases) of the human rabies cases diagnosed in the United States since 1980 (15) and in a recent death in Quebec (16). The recent spread of raccoon rabies from New York State into southeastern Ontario has increased the media coverage of rabies and will contribute to uncertainty about the presence of the RABV in the province. Under these circumstances, with the relatively safe HDCV, a continuing high number of treatments should be expected. Even in the absence of further rabies cases, the regression results suggest, at the 95% confidence interval confidence interval, n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. , annual treatments would range from 650 to 1,072 annually. The decline in PET per rabid animal and PET rate per 100,000 persons in the 1968 to 1980 period hints at other factors affecting the relationship between animal rabies and the administration of PET. We were unable to find any evidence in published studies detailing a change of government policy about the administration of PET or some traumatic event A traumatic event is an event that is or may be a cause of trauma. The term may refer to one of the followiong:
This phrase is used to characterize an officer, a government, a past action, or a state of affairs that must be accepted for all practical purposes, but is illegal or illegitimate. policy change. Indeed, studies during that period recommended a treatment approach similar to today's guidelines (17). Furthermore, compulsory vaccination of companion animals was not an explanation. Under the Health Protection and Promotion Act, a regulation governing rabies immunization immunization: see immunity; vaccination. was not introduced until 1984 and it has taken until 2000 for all district health units in southern Ontario to be included in it (18). All we know is that, early in this period, rabies incidence across southern Ontario had stabilized and developed regular cycles in various regions (19). We can only speculate that, as animal rabies incidence became more predictable, health professionals and the public learned to manage the risk and there was less pressure to give PET, especially with older vaccines and their lengthy regime of injections. Experience in the United States indicated that consultation with state health departments during management of potential rabies exposure reduced PETs (10). Conclusions Our data suggest that human interventions have played a major role in the relationship between PET and animal rabies. The introduction of a new, safer vaccine was associated with a sudden increase in the number of PETs per rabid animal. Furthermore, while the introduction of an ORVP reduced animal rabies, PET did not drop at a similar rate and has appeared to stabilize at approximately 1,000 persons per year. This stabilization, despite the diminishing number of rabies cases, is important in estimating the economic impact of rabies control and public education. However, as our data for the 1968 to 1980 period show, there are other, as-yet-unknown factors that affect the animal rabies/PET relationship. We believe that two general approaches are needed for the future study of this complex relationship. First, we need details of the circumstances of rabies incidents involving human exposures, such as those assembled by Moran et al. (5), Honig (unpub. data), and the Public Health Branch, Ministry of Health (12). For Ontario, assembling these data will require follow-up interviews on a case-by-case basis. Second, if we can obtain data on the distribution of PETs by the 32 health units in southern Ontario (we have distribution data for animal rabies), we may gain further insight by (a) examining the distribution and interaction of human and animal populations; (b) investigating the influence of the geographic scale at which the relationships are examined; and (c) making regional comparisons of the administration of PET and the relative surveillance efforts in an area over time, given the history of rabies incidence and public awareness campaigns in the area.
Table. Rabies postexposure treatment (PET) and
laboratory-confirmed animal rabies, Ontario, 1958 to 2000
Animal
Year PET rabies
1958 1,647 2,426
1959 479 1,210
1960 566 241
1961 790 636
1962 991 879
1963 965 907
1964 852 1,006
1965 1,367 1,352
1966 1,168 1,004
1967 1,461 1,232
1968 1,539 1,924
1969 1,187 2,154
1970 1,164 1,477
1971 960 1,428
1972 1,252 2,161
1973 1,020 1,503
1974 974 1,425
1975 1,050 1,954
1976 935 1,395
1977 957 1,267
1978 816 1,422
1979 1,002 1,480
1980 1,096 1,412
Average 1,054 1,387
1981 1,833 1,333
1982 2,402 2,095
1983 2,481 1,834
1984 2,027 1,366
1985 2,150 1,975
1986 4,212 3,274
1987 2,621 2,001
1988 2,266 1,830
1989 2,640 1,870
1990 1,991 1,611
1991 1,739 1,234
1992 2,186 1,371
1993 2,581 1,241
1994 1,437 613
1995 1,182 328
1996 937 149
1997 1,079 95
1998 1,048 80
1999 890 100
2000 1,073 183
Average 1,939 1,229
Ratio PET to PET rate per
Year animals rabies 100,000 (a)
1958 0.7 28.3
1959 0.4 8.0
1960 2.3 9.3
1961 1.2 12.7
1962 1.1 15.6
1963 1.1 14.9
1964 0.8 12.9
1965 1.0 20.2
1966 1.2 16.8
1967 1.2 20.5
1968 0.8 21.2
1969 0.6 16.1
1970 0.8 15.4
1971 0.7 12.4
1972 0.6 15.8
1973 0.7 12.7
1974 0.7 11.9
1975 0.5 12.6
1976 0.7 11.1
1977 0.8 11.3
1978 0.6 9.5
1979 0.7 12.0
1980 0.8 11.6
Average 0.8 14.3
1981 1.4 20.8
1982 1.1 27.0
1983 1.4 27.5
1984 1.5 22.1
1985 1.1 23.2
1986 1.3 44.7
1987 1.3 27.2
1988 1.2 23.1
1989 1.4 26.2
1990 1.2 19.4
1991 1.4 16.7
1992 1.6 20.7
1993 2.1 24.2
1994 2.3 13.3
1995 3.6 10.8
1996 6.3 8.5
1997 11.4 9.6
1998 13.1 9.2
1999 8.9 7.7
2000 5.9 9.2
Average 1.6 19.0
(a) Population figures are from Statistics Canada Quarterly
Estimates of Population for Canada, Provinces and Territories,
1951-2000.
Acknowledgments We thank Charles MacInnes for his valuable input, Lindsay Elmgren for providing the results of animal rabies laboratory tests for analysis, and Celine Muis for assisting with background research. References (1.) Ontario Ministry of Health. 59th annual report. Toronto: The Ministry; 1984. (2.) Noah DL, Smith MG, Gotthardt JC, Krebs JW, Green D, Childs JE. Mass human exposure to rabies in New Hampshire New Hampshire, one of the New England states of the NE United States. It is bordered by Massachusetts (S), Vermont, with the Connecticut R. forming the boundary (W), the Canadian province of Quebec (NW), and Maine and a short strip of the Atlantic Ocean (E). : exposures, treatment, and cost. Am J Public Health 1996;86:1149-51. (3.) Plotkin SA, Rupprecht CE, Koprowski H. Rabies vaccine. In: Plotkin SA, Orenstein WA, editors. Vaccines. 3rd ed. Philadelphia: WB Saunders Company; 1999. p. 743-66. (4.) Krebs JW, Long-Marin SC, Childs JE. Causes, costs and estimates of rabies postexposure prophylaxis Postexposure prophylaxis (PEP) Any treatment given after exposure to a disease to try to prevent the disease from occurring. In the case of rabies, PEP involves a series of vaccines given to an individual who has been bitten by an unknown animal or one that is treatments in the United States. J Public Health Management Practice 1998;4:56-62. (5.) Moran GJ, Talan DA. Mower mower, farm machine used for cutting grasses and other hay crops. Mowers, drawn by or attached to tractors, or self-propelled, have superseded scythes. The mower is essentially an adaptation of the much earlier reaper. The first commercial mower was patented in 1847. W, Newdow M, Ong S, Nakase JY, et al. Appropriateness of rabies postexposure prophylaxis treatment for animal exposures. JAMA JAMA abbr. Journal of the American Medical Association 2000;284:1001-7. (6.) label H, Corner AH, Webster WA, Casey CA. History and epizootiology of rabies in Canada. Can Vet J 1974:15:271-81. (7.) Rabies Research and Development Unit, Ontario Ministry of Natural Resources. Rabies in Ontario review of the year 2000. The Rabies Reporter 2001;11:1-4. (8.) MacInnes CD, LeBer CA. Wildlife management agencies should participate in rabies control. Wildlife Society Bulletin 2000:28:1156-67. (9.) Ontario Ministry of Health. 55th to 59th annual reports. Toronto: The Ministry; 1979/1980 to 1983/1984. (10.) Helmick CG. The epidemiology of human rabies postexposure prophylaxis, 1980-81. JAMA 1983;250:1990-6. (11.) MacInnes CD, Smith SM, Tinline RR, Ayers NR, Bachmann P, Ball DGA DGA Directors Guild of America (movie directors union) DGA Délégation Générale pour l'Armement (France) DGA Directeur-Grootaandeelhouder (Dutch: Managing Director and Major Shareholder) , et al. Elimination of rabies from red foxes in eastern Ontario. J Wildl Dis 2001;37:119-32. (12.) Public Health Branch, Ontario Ministry of Health. Rabies post-exposure treatment (PET): Ontario, April 1 to June 30, 1998. Public Health and Epidemiology Report Ontario 1999;10:16-18. (13.) Rupprecht CE, Smith JS, Fekadu M, Childs JE. The ascension of wildlife rabies: a cause of public health concern or intervention? Emerg Infect Dis 1995;1:107-14. (14.) Mitchell KD, Heilman JP, Howard BW, Agnew EW Jr. Raccoon rabies--the urban challenge [abstract]. Proceedings of the 10th Annual International Meeting of Rabies in the Americas, San Diego, California “San Diego” redirects here. For other uses, see San Diego (disambiguation). San Diego is a coastal Southern California city located in the southwestern corner of the continental United States. As of 2006, the city has a population of 1,256,951. , 1999. San Diego San Diego (săn dēā`gō), city (1990 pop. 1,110,549), seat of San Diego co., S Calif., on San Diego Bay; inc. 1850. San Diego includes the unincorporated communities of La Jolla and Spring Valley. Coronado is across the bay. : California Association of Public Health Directors; 1999. p. 90 (15.) Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. . Human rabies--Connecticut, 1995. MMWR MMWR Morbidity & Mortality Weekly Report Epidemiology A news bulletin published by the CDC, which provides epidemiologic data–eg, statistics on the incidence of AIDS, rabies, rubella, STDs and other communicable diseases, causes of mortality–eg, Morb Mortal Wkly Rep 1996;45:207-9. (16.) Population and Public Health Branch, Health Canada Health Canada (French: Santé Canada) is the department of the government of Canada with responsibility for national public health. Health Canada's goal is to improve Canadian life by improving Canadian longevity, lifestyle and use of public healthcare. . A case report--human rabies in Montreal, Quebec--October, 2000. Can Commun Dis Rep 2000:26:209-10. (17.) McWilliam RS, Penistan JL. Immunization against rabies. Canadian Medical Association Journal The Canadian Medical Association Journal (CMAJ) is a general medical journal that is published biweekly by the Canadian Medical Association (CMA). It is considered to be one of the top six general medical journals; the others being the 1967;94:153-7. (18.) Rabies Immunization. Revised Regulations of Ontario. 1990, Reg. 567. Amended to O. Reg. 331/00. (19.) Voigt D, Tinline RR. Fox rabies and trapping: a study of disease and fur harvest interaction. In: Sanderson GG, editor. Midwest furbearer fur·bear·er also fur-bear·er n. An animal whose skin is covered with fur, especially fur that is commercially valuable. fur management: proceedings of the symposium held at the 43rd Midwest Wildlife Conference. Washington: The Wildlife Society; 1982. p. 139-56. Address for correspondence: R. R. Tinline, Queen's GIS Laboratory, Queen's University Queen's University, at Kingston, Ont., Canada; nondenominational; coeducational; founded 1841 as Queen's College. It achieved university status in 1912. It has faculties of arts and sciences, education, law, medicine, and applied science, as well as schools of , Kingston, Ontario Kingston, Ontario, is a Canadian city located at the eastern end of Lake Ontario, where the lake runs into the St. Lawrence River and the Thousand Islands begin. Kingston is the county seat of Frontenac County. , Canada K7L 3N6; fax: 613-533-6948; e-mail: tinliner@qsilver.queensu.ca Christopher P. Nunan, * Rowland R. Tinline, ([dagger]) Janet M. Honig, ([dagger]) David G. A. Ball, ([dagger]) Peggy Hauschildt, ([dagger]) and Charles A. LeBert ([double dagger double dagger n. A reference mark (  ) used in printing and writing. Also called diesis.Noun 1. ]) * Ontario Ministry of Natural Resources, Peterborough, Ontario, Canada; ([dagger]) Queen's University, Kingston, Ontario, Canada Dr. Nunan is a research biologist with the Rabies Research Unit of the Ontario Ministry of Natural Resources. His major research interests lie in the assessment and management of risk in situations involving human response to animal disease. |
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