The Public Health Implications of Urban Dogs ALAN M. BECK, ScD
Health problems due to the increasing urban population of pet and stray dogs are discussed.
Introduction There is an ever growing awareness of the impact that urban pet and stray dogs have on the public's health and general well being. During the early 1970s, cities all over the United States held public hearings to review their animal control ordinances; articles documenting and qualifying the problem appeared in newspapers and the scientific literature.'-IO The 1974 Science Year Annual of World Book and the 1974 Nature Science Annual of Time-Life Books each had a major article on the urban dog problem. Bills have been introduced into the U.S. Senate and various state assemblies to provide funds or loans to municipalities for the establishment and/or construction of nonprofit spaying and neutering clinics. There is a growing body of literature debating the value of such clinics, 11-7 which is of interest to the medical community, for in at least 47 per cent of the cities and counties around the country animal control is the province of the health department."8 When the National League of Cities surveyed the country's mayors, they asked "What do citizens most frequently complain about?" Over 60 per cent of the mayors ranked "dogs and animal control problems" number one. 19 Although part of this awareness may be generated by the recent publicity itself, it is probable that there are, in addition, ecological changes taking place in urban dog populations that have increased the negative interactions between man and dog. All of these changes were caused by man; man has always been a major ecological component in dogs' evolution and survival. Dogs, in turn, have been part of man's ecology; for example, dogs aid many in facing the isolation and fears of urban life.2022 For others, dogs may be a source of anxiety and annoyance. Non-owners are for the Dr. Beck is Director, Bureau of Animal Affairs, New York City Department of Health, New York, New York 10013. This article was accepted for publication August, 1975.
most part a disenfranchised majority with no social organization or industry to support their views. In contrast, dog owners have kennel clubs and pet food companies which have helped to make dogs a pervasive part of our society.
Sources of Data The information used in this article is derived from the author's research on the ecology of urban dogs in Baltimore (1968 to 1972)' and St. Louis (1972 to 1974) and from a general review of the literature. This information has been synthesized in an attempt to explain the nature of the public health relationship that now exists between the urban dweller and the companion dog population.
Population Size and Interaction There is no truly accurate census of the pet population, although the popular press and humane societies frequently draw attention to a recent pet population explosion. Some quantitative evidence comes from animal shelters around the country which report an increase in the numbers of dogs handled. The number of dogs registered with the American Kennel Club (AKC) has nearly doubled since 1963, with over 1.1 million dogs being registered in 1972. Although this population represents less than 4 per cent of the total pet population, it serves as an indicator of growth. Another indicator, dog food sales, has increased over 300 per cent since 1965, averaging an annual increase of 13 per cent. Over $2 billion worth of dog food was sold in 1973.23 It is now estimated that 38 per cent of all U.S. families own at least one dog, i.e., there is one dog for every 5.9 persons.' Pet owners are more likely to live in single family dwellings or larger apartments and have higher median incomes than non-owners.2' Indeed, only 8 per cent of each year's "puppy crop" comes from families whose mean annual income is less than $8,000.25 URBAN DOGS
1315
Although many believe that there is a rise in the dog population, there is evidence from a 5 per cent sample of all households in two California counties that the pet dog population has been declining since 1968.26 Anecdotally, the number of dogs being shipped for sale has been declining. Thus, it is possible that the recent pet population increase has leveled off. Any increase in the dog population must lead to increased interactions between people and dogs; thus it is not surprising that diseases and injuries previously associated exclusively with occupations involving animal contact are occurring in the general population. As an example, leptospirosis is traditionally listed as a disease of animalrelated occupations, but in 1971, 63 per cent of the cases were associated with dogs, as compared with 32 per cent for the period 1966 to 1970; 59 per cent of the victims were less than 20 years old." In St. Louis City, over 40 per cent of dogs sampled at the pound had titers to leptospirosis, indicative of present or previous disease, and several human cases occurred in the area.28 Rabies is another example of a dog contact problem. Although it is widely believed that rabies in domestic dogs is under control, and most rabies occurs in wildlife, rabies adds greatly to the trauma and expense of dog bite injury.29 30 For instance, in Illinois, from 1967 to 1968, although 71 per cent of the 937 rabid animals reported were skunks, skunks were responsible for only 2 per cent of the cases requiring human vaccination. Conversely, only 4 per cent of the rabid animals were dogs, but dog bite was responsible for 58 per cent of the incidents requiring vaccination for possible exposure to rabies.3" In 1972, over 35,000 people received 475,758 doses of rabies vaccine in the U.S., predominantly as a result of being bitten by pet dogs.32 Increased dog-human contact may be expected to lead to an increased incidence of 'other diseases shared by man and dog, such as tick-borne typhus.33
Age Structure Nationally, the annual destruction rate of dogs is estimated to be at least 12 per cent.2 In Baltimore, over 15 per cent of the estimated dog population was destroyed by the pound annually, and automobile traffic killed nearly 10 per cent yearly.1 High mortality in a growing population means a lowering of the age distribution. In both Baltimore and St. Louis, the mean age of impounded dogs was only 2.3 years, with over 60 per cent of the population under 2 years of age. By contrast, the household dogs of Alameda County, California, in 1965 had a mean age of 4.4 years with only 43.6 per cent under 2 years.34 A young population is composed.mostly of new, nonimmune individuals. Young animals are more bite-prone33 and are more susceptible to disease and worm infestation.36 Dog worms are more than a veterinary problem. Many human parasites have animal counterparts, e.g., the roundworms Ascaris lumbricoides and Toxocara canis. These counterparts will infect man, although they may not complete their life cycles. Host specificity may not manifest itself until after infection is established, which is important 1316 AJPH DECEMBER, 1975, Vol. 65, No. 12
in the evolution of the host-parasite relationship. A parasite's inability to complete its life cycle should not be equated with lack of infectivity. T. canis is the commonest parasite causing pathology in man, e.g., toxocariasis or visceral larva migrans.37-4 It is not possible to estimate prevalence of this disease in man, because it is usually undiagnosed, except when the larvae are observed in the eye. There are 403 cases described in the literature. However, as Brown46 notes " . . . the disease is too common for single case reports and is too rare for many large series." Almost all dogs are born with Toxocara infestation; indeed it is almost impossible to breed wormfree animals."7 In St. Louis, pound dogs under 1 year were nearly 30 per cent infected, although older groups averaged only 8 per cent infected. A younger animal population exposes humans to a greater risk of aberrant parasitism.
Biomass of the Population Another ecological parameter that appears to be changing is the biomass of the population; i.e., the population is becoming composed of larger dogs. The numbers of smaller breeds, e.g., poodles, beagles, and dachshunds, registered between 1963 and 1972 by the AKC was almost unchanged. However, the registration of the larger breeds showed marked increases: almost twice as many German shepherds, 6.6 times as many Doberman pinschers, 11 times as many St. Bernards, 6 times as many Great Danes, 13 times as many Siberian huskies, and 10 times as many malamutes. Less quantitatively, the author has observed that pet stores and animal shelters sell their larger breeds as fast as they become available. This trend may be motivated by the public's awareness of urban crime and the hope that larger dogs will warn and protect their owners. But increasing the biomass of the population also increases the waste output. Fecal output varies, but averages 340 gm (0.75 pound) per day for a large dog. That means that the streets and sewer systems of New York City will receive over 187 tons of feces daily from its estimated one-half million dogs as larger dogs become more common. Such fecal contamination is a public health problem that would not be tolerated from any other mammalian source. Larger dogs also inflict more serious bites, and this may be related to an increase in the number of reported bites. In St. Louis, 36.6 per cent of all biters were classified as large by the person filing the report,3 and in New York, 43.4 per cent of all biters had an average adult weight of at least 50 pounds.8 In Baltimore from 1960 to 1970, reported bites increased 78 per cent while the human population decreased 3.5 per cent. Indeed, over these years, dogs accounted for 95 per cent of all animal bites, and dog bites were the only animal injuries to increase consistently. In New York City, the dog bite rate was fairly constant until 1965, but increased 33 per cent between 1965 and 1970.8 Since 1960 in Baltimore, the proportion of reported bites from strays has also been increasing and now represents about 24 per cent of the total.48 In St. Louis, about 15 per cent of bites are from strays, indicating that, contrary to popular belief, the stray dog is not the source of the biggest bite problem. The U.S.
bite rate is now about 500 bites per 100,000 people. It is estimated that far less than one-half of the bites are reported.1' 35 In St. Louis, 2 per cent of all 5- to 9-year-old children are bitten each year, and 37 per cent of the children bitten are bitten on the face.3 The same pattern is observed in New York.8 The bite injury problem can be expected to become more serious as people own larger dogs, especially guard dogs. Larger dogs require more meat, which may aggravate the sensitive political problems related to shortages of food. Competition with humans for food was apparently one reason for the destruction of dogs in China.4"
Social Structure The social structure of dogs includes groups or packs. About one-half of all dogs observed on the streets are in the company of other dogs, 26 per cent in groups of two, 16 per cent in threes, and 5 per cent in fours, with sporadic groups of 20 or more.' About 2 per cent of all dog bites in St. Louis are attacks from more than one dog. Society's tolerance of dogs permits the proximity of people that may lead to a bite-especially in the case of larger animals. Socially facilitated behaviors, i.e., behaviors initiated by an individual dog and mimicked by the group, are common. Behaviors such as chasing and biting people, barking, and disrupting trash are therefore more of a health problem than would be the case if dogs were solitary, like cats. And, of course, disrupted trash encourages the breeding of houseflies and rats and greatly adds to the expense of trash removal.
Summary and Conclusions Dogs have gone from being benignly accepted as man's best friend to becoming a source of social, political, and medical concern. This change is probably related to an increase in the number of dogs, especially younger animals, and the increased popularity of larger breeds. In view of these trends it is suggested that physicians give dog-related zoonoses a higher index of suspicion, and include pet ownership or contact as part of the patient's history. It is also time for the social and legislative forces of society to respond humanely, but strictly, by exercising greater control over the size of the dog population, the dogs' freedom to roam, and their promiscuous defecation. The dog should not be considered a pest to expel from society. In fact, the controls necessary to safeguard the public would also benefit the canine population. Dogs that are under direct supervision or control are healthier, live longer, and appear to be better adjusted, perhaps because a pet's real social group includes its owner. The unsafe aspects of livestock and wildlife populations have been made known to those in contact with them. It is now time for urban dwellers as well to have a more balanced view of the man-dog relationship so that man and dog can live together in health and peace. REFERENCES 1. Beck, A. M. The Ecology of Stray Dogs. York Press, Baltimore,
1973.
2. Beck, A. M. The Dog: America's Sacred Cow? Nation's Cities 12(2):28-31, 34-35, 1974. 3. Beck, A. M., Loring, H., and Lockwood, R. The Ecology of Dog Bite Injury in St. Louis, Mo. Public Health Rep. 90:262-267, 1975. 4. Lockwood, R., and Beck, A. M. Dog Bites amontg Letter Carriers in St. Louis, Public Health Rep. 90:267-269, 1975. 5. Djerassi, C., Israel, A., and Jochle, W. Planned Parenthood for Pets? Bull. Atom. Scientists January:10-19, 1973. 6. Feldmann, B. M., and Carding, T. H. Free-Roaming Urban Pets. Health Serv. Rep. 88:956-962, 1973. 7. Feldmann, B. M. The Problem of Urban Dogs (Editorial). Science 185:903, 1974. 8. Harris, D., Imperato, P. J., and Oken, B. Dog Bites-An Unrecognized Epidemic. Bull. N. Y. Acad. Med. 50:981-1000, 1973. 9. Robinson, D. Canis Familiaris (Editorial). N. Engl. J. Med. 290:1378-1379, 1974. 10. Berzon, D. R., and DeHoff, J. B. Medical Costs and Other Aspects of Dog Bites in Baltimore. Public Health. Rep. 89:377-381, 1974. 11. Beck, A. M. Ecology of Unwanted and Uncontrolled Pets. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp 31-39. American Veterinary Medical Association, Chicago, 1974. 12. Hoyt, J. A. A Case for Spay/Neuter Clinics. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp. 59-65. American Veterinary Medical Association, Chicago, 1974. 13. Drenan, D. M. Limitations of Spay/Neuter Clinics. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp. 67-74. American Veterinary Medical Association, Chicago, 1974. 14. Faulkner, L. C. Alternatives to Surgical Sterilization. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp. 75-81. American Veterinary Medical Association, Chicago, 1974. 15. Feldmann, B. M., and Carding, T. H. Minimal Cost, Nonprofit Veterinary Service. J. Am. Vet. Med. Assoc. 162:481-484, 1974. 16. Staff Report. Spay Clinics: Boon or Boondoggle? Mod. Vet. Pract. 23-29, March, 1973. 17. Staff Report. Spay Clinics: The Other Side of the Story. Mod. Vet. Pract. 29-34, April, 1973. 18. Reefer, J. D. Animal Control Survey. Community Service Department, City of Kansas City, MO, November, 1974. 19. Bancroft, R. America's Mayors and Councilmen: Their Problems and Frustrations. The National League of Cities Research Report. National League of Cities, Washington, DC, 1974. 20. Heiman, M. The Relationship between Man and Dog. Psychoanal. Q. 25:568-585, 1956. 21. Leigh, D. The Psychology of the Pet Owner. J. Small Anim. Pract. 7:517-521, 1966. 22. Levenson, B. Pets and Human Development. Charles C Thomas, Springfield, IL, 1972. 23. O'Keefe, P. Pet Food Institute Fact Sheet, 1973-1974. Pet Food Institute, Chicago, 1974. 24. Franti, C. E., and Kraus, J. F. Aspects of Pet Ownership in Yolo County, Calif. J. Am. Vet. Med. Assoc. 164: 166-171, 1974. 25. Schneider, R. Observations on Overpopulation of Dogs and Cats. J. Am. Vet. Med. Assoc. 167:281-284, 1975. 26. Schneider, R., and Vaida, M. L. Survey of Canine and Feline Populations: Alameda and Contra Costa Counties, Calif., 1970. J. Am. Vet. Med. Assoc. 166:481-486,1975. 27. Center for Disease Control. Leptospirosis Annual Summary, 1971. December, 1972. 28. Feigin, R. D., Lobes, L. A., Jr., Anderson, D., and Pickering, L. Human Leptospirosis from Immunized Dogs. Ann. Intern. Med. 79:777-785, 1973. 29. Cereghino, J. J., Osterud, J. J., Pinnas, J. L., and Holmes, M. A. Rabies: A Rare Disease But a Serious Pediatric Problem. Pediatrics 45:839-844, 1970. URBAN DOGS
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30. Schnurrenberger, P. R., Martin, R. J., Meerdink, G. L., and Rose, N. J. Epidemiology of Human Exposure to Rabid Animals in Illinois. Public Health Rep. 84:1078-1084, 1969. 31. Martin, R. J., Schnurrenberger, P. R., and Rose, N. J. Epidemiology of Rabies Vaccinations of Persons in Illinois, 1967-1968. Public Health Rep. 84: 1069-1077, 1969. 32. Center for Disease Control. Rabies Surveillance Annual Summary 1972. June, 1973. 33. Peters, A. H. Tick-Borne Typhus (Rocky Mountain Spotted Fever). J. A. M. A. 216:1003-1007, 1971. 34. Dorn, C. R., Terbrusch, F. G., and Hibbard, H. H. Zoographic and Demographic Analysis of Dog and Cat Ownership in Alameda Co., Calif. California Department of Public Health, Berkeley, 1965. 35. Parrish, H. M., Clack, F. B., Brobst, D., and Mock, J. F. Epidemiology of Dog Bites. Public Health Rep. 74:891-903, 1959. 36. Greve, J. H. Age Resistance to Toxocara canis in Ascarid-Free Dogs. Am. J. Vet. Res. 32:1185-1192, 1971. 37. Beaver, P. C. Visceral and Cutaneous Larva Migrans. Public Health Rep. 74:328-332, 1959. 38. Brown, D. H. Ocular Toxocara canis. J. Ped. Ophthalmol. 7:182-191, 1970. 39. Ehrenford, F. A. Canine Ascariasis, a Source of Visceral Larva Migrans. Am. J. Trop. Med. Hyg. 6:166-170, 1957.
40. Rubin, M. L., Kaufman, H. E., Tierney, J. P., and Lucas, H. C. An Intraretinal Nematode. Trans. Am. Acad. Ophthalmol. Otolaryngol. 72:855-866, 1968. 41. Snyder, C. H. Visceral Larva Migrans: Ten Years' Experience. Pediatrics 28:85-91, 1961. 42. Webb, C. H. Pets, Parasites, and Pediatrics. Pediatrics 36:521-522, 1965. 43. Wilkinson, C. P., and Welch, R. B. Intraocular Toxocara. Am. J. Ophthalmol. 71:921-930, 1971. 44. Wilder, H. C. Nematode Enophthalmitis. Trans. Am. Acad. Ophthalmol. Otolaryngol. 55:99-109, 1950. 45. Zinkham, W. H. Visceral Larva Migrans Due to Toxocara as a Cause of Eosinophilia. Johns Hopkins Med. J. 123:41-47, 1968. 46. Brown, D. H. The Geography of Ocular Toxocara canis. Ann. Opthalmol. 6:343-344, 1974. 47. Griesemer, R. H., Gibson, J. P., and Elassnar, D. S. Congenital Ascariasis in Gnotobiotic Dogs. J. Am. Vet. Med. Assoc. 143:962-964, 1963. 48. Berzon, D. R., Farber, R. E., Gordon, J., and Kelly, E. B. Animal Bites in a Large City-A Report on Baltimore, Maryland. Am. J. Public Health 62:422-426, 1972. 49. Kinmond, W. No Dogs in China. Thomas Nelson and Sons, New York, 1957.
AAAS MEETING SET FOR BOSTON IN FEBRUARY "Science and Our Expectations: Bicentennial and Beyond" is the theme of the 142nd Annual Meeting of the American Association for the Advancement of Science (AAAS), to be held February 18-24, 1976, in Boston. Several thousand scientists are expected to attend the 7-day meeting in the Sheraton-Boston Hotel and the adjacent John B. Hynes Auditorium at the Prudential Center. Some 180 symposiums will be presented on topics centered around three subthemes: Frontiers of Science, Uses of Science, and Perspectives on Science. In 20 daily concurrent sessions, speakers will explore not only advances in research in various areas of science, engineering, and medicine, but also the application of science and technology and the social and ethical implications of such use. The AAAS meeting also will feature 10 public lectures by noted scientists on such topics as "Exploration of the Midatlantic Rift," "Toward a Human Scientist," "The Emergence of Biochemistry," "Income Distribution and Economic Equity in the United States," and "Mapping the Grand Canyon." Science International, a major exhibition of scientific instruments and publications, will be an integral part of the meeting for the second consecutive year. As a part of its new Project on the Handicapped in Science, AAAS will make this year's meeting fully accessible to people who are in wheelchairs, who have visual or auditory disabilities, and who need assistance because of other disabilities. For further information, see the November 14 issue of Science, or write to the AAAS Meetings Office, 1776 Massachusetts Avenue, N.W., Washington, DC 20036.
1318 AJPH DECEMBER, 1975, Vol. 65, No. 12
Health problems due to the increasing urban population of pet and stray dogs are discussed.
Introduction There is an ever growing awareness of the impact that urban pet and stray dogs have on the public's health and general well being. During the early 1970s, cities all over the United States held public hearings to review their animal control ordinances; articles documenting and qualifying the problem appeared in newspapers and the scientific literature.'-IO The 1974 Science Year Annual of World Book and the 1974 Nature Science Annual of Time-Life Books each had a major article on the urban dog problem. Bills have been introduced into the U.S. Senate and various state assemblies to provide funds or loans to municipalities for the establishment and/or construction of nonprofit spaying and neutering clinics. There is a growing body of literature debating the value of such clinics, 11-7 which is of interest to the medical community, for in at least 47 per cent of the cities and counties around the country animal control is the province of the health department."8 When the National League of Cities surveyed the country's mayors, they asked "What do citizens most frequently complain about?" Over 60 per cent of the mayors ranked "dogs and animal control problems" number one. 19 Although part of this awareness may be generated by the recent publicity itself, it is probable that there are, in addition, ecological changes taking place in urban dog populations that have increased the negative interactions between man and dog. All of these changes were caused by man; man has always been a major ecological component in dogs' evolution and survival. Dogs, in turn, have been part of man's ecology; for example, dogs aid many in facing the isolation and fears of urban life.2022 For others, dogs may be a source of anxiety and annoyance. Non-owners are for the Dr. Beck is Director, Bureau of Animal Affairs, New York City Department of Health, New York, New York 10013. This article was accepted for publication August, 1975.
most part a disenfranchised majority with no social organization or industry to support their views. In contrast, dog owners have kennel clubs and pet food companies which have helped to make dogs a pervasive part of our society.
Sources of Data The information used in this article is derived from the author's research on the ecology of urban dogs in Baltimore (1968 to 1972)' and St. Louis (1972 to 1974) and from a general review of the literature. This information has been synthesized in an attempt to explain the nature of the public health relationship that now exists between the urban dweller and the companion dog population.
Population Size and Interaction There is no truly accurate census of the pet population, although the popular press and humane societies frequently draw attention to a recent pet population explosion. Some quantitative evidence comes from animal shelters around the country which report an increase in the numbers of dogs handled. The number of dogs registered with the American Kennel Club (AKC) has nearly doubled since 1963, with over 1.1 million dogs being registered in 1972. Although this population represents less than 4 per cent of the total pet population, it serves as an indicator of growth. Another indicator, dog food sales, has increased over 300 per cent since 1965, averaging an annual increase of 13 per cent. Over $2 billion worth of dog food was sold in 1973.23 It is now estimated that 38 per cent of all U.S. families own at least one dog, i.e., there is one dog for every 5.9 persons.' Pet owners are more likely to live in single family dwellings or larger apartments and have higher median incomes than non-owners.2' Indeed, only 8 per cent of each year's "puppy crop" comes from families whose mean annual income is less than $8,000.25 URBAN DOGS
1315
Although many believe that there is a rise in the dog population, there is evidence from a 5 per cent sample of all households in two California counties that the pet dog population has been declining since 1968.26 Anecdotally, the number of dogs being shipped for sale has been declining. Thus, it is possible that the recent pet population increase has leveled off. Any increase in the dog population must lead to increased interactions between people and dogs; thus it is not surprising that diseases and injuries previously associated exclusively with occupations involving animal contact are occurring in the general population. As an example, leptospirosis is traditionally listed as a disease of animalrelated occupations, but in 1971, 63 per cent of the cases were associated with dogs, as compared with 32 per cent for the period 1966 to 1970; 59 per cent of the victims were less than 20 years old." In St. Louis City, over 40 per cent of dogs sampled at the pound had titers to leptospirosis, indicative of present or previous disease, and several human cases occurred in the area.28 Rabies is another example of a dog contact problem. Although it is widely believed that rabies in domestic dogs is under control, and most rabies occurs in wildlife, rabies adds greatly to the trauma and expense of dog bite injury.29 30 For instance, in Illinois, from 1967 to 1968, although 71 per cent of the 937 rabid animals reported were skunks, skunks were responsible for only 2 per cent of the cases requiring human vaccination. Conversely, only 4 per cent of the rabid animals were dogs, but dog bite was responsible for 58 per cent of the incidents requiring vaccination for possible exposure to rabies.3" In 1972, over 35,000 people received 475,758 doses of rabies vaccine in the U.S., predominantly as a result of being bitten by pet dogs.32 Increased dog-human contact may be expected to lead to an increased incidence of 'other diseases shared by man and dog, such as tick-borne typhus.33
Age Structure Nationally, the annual destruction rate of dogs is estimated to be at least 12 per cent.2 In Baltimore, over 15 per cent of the estimated dog population was destroyed by the pound annually, and automobile traffic killed nearly 10 per cent yearly.1 High mortality in a growing population means a lowering of the age distribution. In both Baltimore and St. Louis, the mean age of impounded dogs was only 2.3 years, with over 60 per cent of the population under 2 years of age. By contrast, the household dogs of Alameda County, California, in 1965 had a mean age of 4.4 years with only 43.6 per cent under 2 years.34 A young population is composed.mostly of new, nonimmune individuals. Young animals are more bite-prone33 and are more susceptible to disease and worm infestation.36 Dog worms are more than a veterinary problem. Many human parasites have animal counterparts, e.g., the roundworms Ascaris lumbricoides and Toxocara canis. These counterparts will infect man, although they may not complete their life cycles. Host specificity may not manifest itself until after infection is established, which is important 1316 AJPH DECEMBER, 1975, Vol. 65, No. 12
in the evolution of the host-parasite relationship. A parasite's inability to complete its life cycle should not be equated with lack of infectivity. T. canis is the commonest parasite causing pathology in man, e.g., toxocariasis or visceral larva migrans.37-4 It is not possible to estimate prevalence of this disease in man, because it is usually undiagnosed, except when the larvae are observed in the eye. There are 403 cases described in the literature. However, as Brown46 notes " . . . the disease is too common for single case reports and is too rare for many large series." Almost all dogs are born with Toxocara infestation; indeed it is almost impossible to breed wormfree animals."7 In St. Louis, pound dogs under 1 year were nearly 30 per cent infected, although older groups averaged only 8 per cent infected. A younger animal population exposes humans to a greater risk of aberrant parasitism.
Biomass of the Population Another ecological parameter that appears to be changing is the biomass of the population; i.e., the population is becoming composed of larger dogs. The numbers of smaller breeds, e.g., poodles, beagles, and dachshunds, registered between 1963 and 1972 by the AKC was almost unchanged. However, the registration of the larger breeds showed marked increases: almost twice as many German shepherds, 6.6 times as many Doberman pinschers, 11 times as many St. Bernards, 6 times as many Great Danes, 13 times as many Siberian huskies, and 10 times as many malamutes. Less quantitatively, the author has observed that pet stores and animal shelters sell their larger breeds as fast as they become available. This trend may be motivated by the public's awareness of urban crime and the hope that larger dogs will warn and protect their owners. But increasing the biomass of the population also increases the waste output. Fecal output varies, but averages 340 gm (0.75 pound) per day for a large dog. That means that the streets and sewer systems of New York City will receive over 187 tons of feces daily from its estimated one-half million dogs as larger dogs become more common. Such fecal contamination is a public health problem that would not be tolerated from any other mammalian source. Larger dogs also inflict more serious bites, and this may be related to an increase in the number of reported bites. In St. Louis, 36.6 per cent of all biters were classified as large by the person filing the report,3 and in New York, 43.4 per cent of all biters had an average adult weight of at least 50 pounds.8 In Baltimore from 1960 to 1970, reported bites increased 78 per cent while the human population decreased 3.5 per cent. Indeed, over these years, dogs accounted for 95 per cent of all animal bites, and dog bites were the only animal injuries to increase consistently. In New York City, the dog bite rate was fairly constant until 1965, but increased 33 per cent between 1965 and 1970.8 Since 1960 in Baltimore, the proportion of reported bites from strays has also been increasing and now represents about 24 per cent of the total.48 In St. Louis, about 15 per cent of bites are from strays, indicating that, contrary to popular belief, the stray dog is not the source of the biggest bite problem. The U.S.
bite rate is now about 500 bites per 100,000 people. It is estimated that far less than one-half of the bites are reported.1' 35 In St. Louis, 2 per cent of all 5- to 9-year-old children are bitten each year, and 37 per cent of the children bitten are bitten on the face.3 The same pattern is observed in New York.8 The bite injury problem can be expected to become more serious as people own larger dogs, especially guard dogs. Larger dogs require more meat, which may aggravate the sensitive political problems related to shortages of food. Competition with humans for food was apparently one reason for the destruction of dogs in China.4"
Social Structure The social structure of dogs includes groups or packs. About one-half of all dogs observed on the streets are in the company of other dogs, 26 per cent in groups of two, 16 per cent in threes, and 5 per cent in fours, with sporadic groups of 20 or more.' About 2 per cent of all dog bites in St. Louis are attacks from more than one dog. Society's tolerance of dogs permits the proximity of people that may lead to a bite-especially in the case of larger animals. Socially facilitated behaviors, i.e., behaviors initiated by an individual dog and mimicked by the group, are common. Behaviors such as chasing and biting people, barking, and disrupting trash are therefore more of a health problem than would be the case if dogs were solitary, like cats. And, of course, disrupted trash encourages the breeding of houseflies and rats and greatly adds to the expense of trash removal.
Summary and Conclusions Dogs have gone from being benignly accepted as man's best friend to becoming a source of social, political, and medical concern. This change is probably related to an increase in the number of dogs, especially younger animals, and the increased popularity of larger breeds. In view of these trends it is suggested that physicians give dog-related zoonoses a higher index of suspicion, and include pet ownership or contact as part of the patient's history. It is also time for the social and legislative forces of society to respond humanely, but strictly, by exercising greater control over the size of the dog population, the dogs' freedom to roam, and their promiscuous defecation. The dog should not be considered a pest to expel from society. In fact, the controls necessary to safeguard the public would also benefit the canine population. Dogs that are under direct supervision or control are healthier, live longer, and appear to be better adjusted, perhaps because a pet's real social group includes its owner. The unsafe aspects of livestock and wildlife populations have been made known to those in contact with them. It is now time for urban dwellers as well to have a more balanced view of the man-dog relationship so that man and dog can live together in health and peace. REFERENCES 1. Beck, A. M. The Ecology of Stray Dogs. York Press, Baltimore,
1973.
2. Beck, A. M. The Dog: America's Sacred Cow? Nation's Cities 12(2):28-31, 34-35, 1974. 3. Beck, A. M., Loring, H., and Lockwood, R. The Ecology of Dog Bite Injury in St. Louis, Mo. Public Health Rep. 90:262-267, 1975. 4. Lockwood, R., and Beck, A. M. Dog Bites amontg Letter Carriers in St. Louis, Public Health Rep. 90:267-269, 1975. 5. Djerassi, C., Israel, A., and Jochle, W. Planned Parenthood for Pets? Bull. Atom. Scientists January:10-19, 1973. 6. Feldmann, B. M., and Carding, T. H. Free-Roaming Urban Pets. Health Serv. Rep. 88:956-962, 1973. 7. Feldmann, B. M. The Problem of Urban Dogs (Editorial). Science 185:903, 1974. 8. Harris, D., Imperato, P. J., and Oken, B. Dog Bites-An Unrecognized Epidemic. Bull. N. Y. Acad. Med. 50:981-1000, 1973. 9. Robinson, D. Canis Familiaris (Editorial). N. Engl. J. Med. 290:1378-1379, 1974. 10. Berzon, D. R., and DeHoff, J. B. Medical Costs and Other Aspects of Dog Bites in Baltimore. Public Health. Rep. 89:377-381, 1974. 11. Beck, A. M. Ecology of Unwanted and Uncontrolled Pets. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp 31-39. American Veterinary Medical Association, Chicago, 1974. 12. Hoyt, J. A. A Case for Spay/Neuter Clinics. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp. 59-65. American Veterinary Medical Association, Chicago, 1974. 13. Drenan, D. M. Limitations of Spay/Neuter Clinics. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp. 67-74. American Veterinary Medical Association, Chicago, 1974. 14. Faulkner, L. C. Alternatives to Surgical Sterilization. In Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, pp. 75-81. American Veterinary Medical Association, Chicago, 1974. 15. Feldmann, B. M., and Carding, T. H. Minimal Cost, Nonprofit Veterinary Service. J. Am. Vet. Med. Assoc. 162:481-484, 1974. 16. Staff Report. Spay Clinics: Boon or Boondoggle? Mod. Vet. Pract. 23-29, March, 1973. 17. Staff Report. Spay Clinics: The Other Side of the Story. Mod. Vet. Pract. 29-34, April, 1973. 18. Reefer, J. D. Animal Control Survey. Community Service Department, City of Kansas City, MO, November, 1974. 19. Bancroft, R. America's Mayors and Councilmen: Their Problems and Frustrations. The National League of Cities Research Report. National League of Cities, Washington, DC, 1974. 20. Heiman, M. The Relationship between Man and Dog. Psychoanal. Q. 25:568-585, 1956. 21. Leigh, D. The Psychology of the Pet Owner. J. Small Anim. Pract. 7:517-521, 1966. 22. Levenson, B. Pets and Human Development. Charles C Thomas, Springfield, IL, 1972. 23. O'Keefe, P. Pet Food Institute Fact Sheet, 1973-1974. Pet Food Institute, Chicago, 1974. 24. Franti, C. E., and Kraus, J. F. Aspects of Pet Ownership in Yolo County, Calif. J. Am. Vet. Med. Assoc. 164: 166-171, 1974. 25. Schneider, R. Observations on Overpopulation of Dogs and Cats. J. Am. Vet. Med. Assoc. 167:281-284, 1975. 26. Schneider, R., and Vaida, M. L. Survey of Canine and Feline Populations: Alameda and Contra Costa Counties, Calif., 1970. J. Am. Vet. Med. Assoc. 166:481-486,1975. 27. Center for Disease Control. Leptospirosis Annual Summary, 1971. December, 1972. 28. Feigin, R. D., Lobes, L. A., Jr., Anderson, D., and Pickering, L. Human Leptospirosis from Immunized Dogs. Ann. Intern. Med. 79:777-785, 1973. 29. Cereghino, J. J., Osterud, J. J., Pinnas, J. L., and Holmes, M. A. Rabies: A Rare Disease But a Serious Pediatric Problem. Pediatrics 45:839-844, 1970. URBAN DOGS
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30. Schnurrenberger, P. R., Martin, R. J., Meerdink, G. L., and Rose, N. J. Epidemiology of Human Exposure to Rabid Animals in Illinois. Public Health Rep. 84:1078-1084, 1969. 31. Martin, R. J., Schnurrenberger, P. R., and Rose, N. J. Epidemiology of Rabies Vaccinations of Persons in Illinois, 1967-1968. Public Health Rep. 84: 1069-1077, 1969. 32. Center for Disease Control. Rabies Surveillance Annual Summary 1972. June, 1973. 33. Peters, A. H. Tick-Borne Typhus (Rocky Mountain Spotted Fever). J. A. M. A. 216:1003-1007, 1971. 34. Dorn, C. R., Terbrusch, F. G., and Hibbard, H. H. Zoographic and Demographic Analysis of Dog and Cat Ownership in Alameda Co., Calif. California Department of Public Health, Berkeley, 1965. 35. Parrish, H. M., Clack, F. B., Brobst, D., and Mock, J. F. Epidemiology of Dog Bites. Public Health Rep. 74:891-903, 1959. 36. Greve, J. H. Age Resistance to Toxocara canis in Ascarid-Free Dogs. Am. J. Vet. Res. 32:1185-1192, 1971. 37. Beaver, P. C. Visceral and Cutaneous Larva Migrans. Public Health Rep. 74:328-332, 1959. 38. Brown, D. H. Ocular Toxocara canis. J. Ped. Ophthalmol. 7:182-191, 1970. 39. Ehrenford, F. A. Canine Ascariasis, a Source of Visceral Larva Migrans. Am. J. Trop. Med. Hyg. 6:166-170, 1957.
40. Rubin, M. L., Kaufman, H. E., Tierney, J. P., and Lucas, H. C. An Intraretinal Nematode. Trans. Am. Acad. Ophthalmol. Otolaryngol. 72:855-866, 1968. 41. Snyder, C. H. Visceral Larva Migrans: Ten Years' Experience. Pediatrics 28:85-91, 1961. 42. Webb, C. H. Pets, Parasites, and Pediatrics. Pediatrics 36:521-522, 1965. 43. Wilkinson, C. P., and Welch, R. B. Intraocular Toxocara. Am. J. Ophthalmol. 71:921-930, 1971. 44. Wilder, H. C. Nematode Enophthalmitis. Trans. Am. Acad. Ophthalmol. Otolaryngol. 55:99-109, 1950. 45. Zinkham, W. H. Visceral Larva Migrans Due to Toxocara as a Cause of Eosinophilia. Johns Hopkins Med. J. 123:41-47, 1968. 46. Brown, D. H. The Geography of Ocular Toxocara canis. Ann. Opthalmol. 6:343-344, 1974. 47. Griesemer, R. H., Gibson, J. P., and Elassnar, D. S. Congenital Ascariasis in Gnotobiotic Dogs. J. Am. Vet. Med. Assoc. 143:962-964, 1963. 48. Berzon, D. R., Farber, R. E., Gordon, J., and Kelly, E. B. Animal Bites in a Large City-A Report on Baltimore, Maryland. Am. J. Public Health 62:422-426, 1972. 49. Kinmond, W. No Dogs in China. Thomas Nelson and Sons, New York, 1957.
AAAS MEETING SET FOR BOSTON IN FEBRUARY "Science and Our Expectations: Bicentennial and Beyond" is the theme of the 142nd Annual Meeting of the American Association for the Advancement of Science (AAAS), to be held February 18-24, 1976, in Boston. Several thousand scientists are expected to attend the 7-day meeting in the Sheraton-Boston Hotel and the adjacent John B. Hynes Auditorium at the Prudential Center. Some 180 symposiums will be presented on topics centered around three subthemes: Frontiers of Science, Uses of Science, and Perspectives on Science. In 20 daily concurrent sessions, speakers will explore not only advances in research in various areas of science, engineering, and medicine, but also the application of science and technology and the social and ethical implications of such use. The AAAS meeting also will feature 10 public lectures by noted scientists on such topics as "Exploration of the Midatlantic Rift," "Toward a Human Scientist," "The Emergence of Biochemistry," "Income Distribution and Economic Equity in the United States," and "Mapping the Grand Canyon." Science International, a major exhibition of scientific instruments and publications, will be an integral part of the meeting for the second consecutive year. As a part of its new Project on the Handicapped in Science, AAAS will make this year's meeting fully accessible to people who are in wheelchairs, who have visual or auditory disabilities, and who need assistance because of other disabilities. For further information, see the November 14 issue of Science, or write to the AAAS Meetings Office, 1776 Massachusetts Avenue, N.W., Washington, DC 20036.
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