beginning in 1989 , oral vaccination using bait that contained the live , attenuated , evelyn - rokitnicki - abelseth ( era ) ( 6,7 ) strain of rabies virus was distributed in ontario to control rabies in red foxes in rural and urban habitats ( 4,810 ) . the bait matrix consisted of beef tallow , wax , and attractants such as chicken or cod ( 6 ) .
the vaccine was contained in a blister pack , which was embedded in the matrix of the bait ( figure 2 ) .
evelyn - rokitnicki - abelseth rabies vaccine bait , showing the vaccine container ( normally embedded in the matrix of the bait ) to the right of the bait .
the metropolitan toronto area ( centered at latitude 43 42 north , longitude 79 25 west ) was defined as a 638-km urban complex that included the cities of toronto , north york , etobicoke , east york , york , and north york .
the program in metropolitan toronto was expanded during 19941999 ( figure 3 ) to include the urban corridor from oshawa to hamilton ( greater metropolitan toronto , 1,850 km ) ( figure 3 ) . during 19981999 , baiting in rural southwestern ontario extended into the greater metropolitan toronto area ( figure 3 ) . during the 1990s
, 1,000 foxes ( about 1.5/km ) lived in close proximity to 3 million people in metropolitan toronto ( 10,11 ) .
in addition , during 19871996 , trap - vaccinate - release programs ( vaccination by hand - delivered injection ) to control rabies in striped skunks and raccoons ( procyon lotor ) were conducted in a 60-km portion of metropolitan toronto ( scarborough ) ( 9 ) . from a public health perspective ,
rabies control was crucial because since the 1950s , > 63,000 humans had been treated for exposure to potentially rabid animals in ontario ( 10,12 ) . greater metropolitan toronto area where rabies vaccine bait doses were distributed during 19891999 .
during 19891999 , a total of 332,257 bait doses containing era rabies vaccine were distributed in toronto and the greater metropolitan toronto area ( table ) .
bait was distributed primarily by personnel who walked ( ground baiting ) throughout the ravines and green - belt areas of greater metropolitan toronto ; ecologic studies of red foxes indicated that ravines are used as travel corridors by foxes ( 11 ) . in 1994 , 5,500 bait doses were also distributed aerially along the ravine systems from a turbo beaver aircraft flying at an altitude of 150 m with an approximate airspeed of 140 km / hr . in addition , during 1998 , about 16,000 doses were aerially distributed in the greater metropolitan toronto area by twin - otter aircraft .
timing of bait placement varied each year but was generally in june and november , from 1989 through 1999 .
hand - baiting personnel tried to place 1 vaccine - bait dose every 50 m on both sides of waterways in the ravine systems ( 9 ) .
as a modified live virus rabies vaccine was being used in an urban setting , news releases were issued to the media before and during annual baiting operations .
the primary objective of the media campaign was to notify the public of the program and ask people not to touch the bait .
we documented that 15 persons found bait ( but did not touch the vaccine ) and 22 dogs had contact with or consumed the bait during hand - baiting operations .
clinical signs in dogs after bait ingestion sometimes included diarrhea or vomiting ( most likely attributable to the tallow and wax in the bait ) .
three of the dogs had intestinal problems , and 1 had an intestinal obstruction , likely caused by the blister pack .
after the 1994 aerial baiting campaign , only 5 persons reported finding bait in their yards . the time needed to hand - distribute 28,000 vaccine - bait doses each year in metropolitan toronto was 145 person - days , which is 193 bait doses / person / day .
the annual cost to hand - distribute these 28,000 bait doses was about can $ 25,000 for labor , travel expenses , vehicles , and gas plus $30,000 for the bait ( total cost of $1.96/dose ) .
acceptance of vaccine - bait was determined by the presence of tetracycline in tooth sections ( 6 ) .
bait acceptance by foxes sampled in metropolitan toronto during 19891991 was 55%80% , and rabies antibody was detected in 74%100% of the foxes that consumed the bait ( 9 ) . during this period , 50%68% of the foxes were vaccinated each year ( 9,10 ) .
significantly fewer rabid foxes were reported in metropolitan toronto during the 17 years after fox baiting began ( 19902006 , 5 cases , mean 0.3/yr , standard deviation [ sd ] 0.6 ) than during the 17 years before baiting began ( 19731989 , 96 cases , mean 5.7/yr , sd 7.3 ) ( t=3.01 , p<0.005 ) ( figure 1 ) . on the basis of the cyclic nature of outbreaks in metropolitan toronto of rabies in foxes ( every 25 years ) , as well as in skunks , an outbreak should have occurred during the mid-1990s ; but no outbreak occurred . as of september 2006 , the last rabid fox in metropolitan toronto , as well as the greater metropolitan toronto area , had been reported in 1996 .
distribution of vaccine - bait in that urban complex was discontinued in 2000 because metropolitan toronto had been free from reported rabies in foxes for 3 years .
metropolitan toronto is connected to rural areas through a series of ravine systems dominated primarily by deciduous trees .
these ravines provide a travel corridor through which wildlife , including red foxes , moves into and out of metropolitan toronto ( 11 ) . the ground and aerial distribution of rabies vaccine bait in metropolitan and greater metropolitan toronto , which resulted in immunization of a substantial portion of the fox population against rabies , eliminated rabies from that urban complex .
aerial baiting in rural habitats surrounding metropolitan toronto , as well as greater metropolitan toronto , after 1995 may have contributed to rabies control in metropolitan toronto , as few rabid foxes have been available to disperse rabies into that urban complex .
as well , one can not discount the effect that the trap - vaccinate - release programs in scarborough had on the control of rabies in metropolitan toronto . however , the trap - vaccinate - release program targeted raccoons and skunks as opposed to foxes ( 9 ) .
greater metropolitan toronto has been free of reported cases of rabies in red foxes for a decade ( 19972006 ) and is a notable success for the ontario ministry of natural resources rabies control programs .
the results of this program confirm that distribution of oral rabies vaccine bait is a feasible tactic for controlling rabies in foxes in urban environments .
 to control the arctic variant of rabies virus in red foxes , 332,257 bait doses containing live , attenuated evelyn - rokitnicki - abelseth rabies vaccine were distributed in greater metropolitan toronto during 19891999 . 
 human and pet contact with bait was minimal , and no adverse reactions to the vaccine were noted . 
 significantly fewer rabid foxes were found during the 17 years after fox baiting ( 5 cases during 19902006 ) than in the 17 years before ( 96 cases during 19731989 ) . 
 the last report of a rabid fox in metropolitan toronto was in 1996 ( reporting period through september 2006 ) , which confirms that distributing oral rabies vaccine bait is a feasible tactic for the control of rabies in foxes in urban environments . 
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Discussion