canine intestinal parasites have recently become a more important pathogen for humans , as some parasites , e.g. , giardia ( g. ) intestinalis , toxocara ( t. ) canis and others , have become potential public health hazards due to zoonotic transmission . in particular , private household dogs
that have relatively close contact with humans represent a serious potential source of direct parasitic transmission .
although human parasitic diseases are well controlled in japan , many people are still contract zoonotic parasites .
epidemiological data from dogs can undoubtedly contribute to preventing direct zoonotic transmission from dogs to humans via the control of infectious animals .
in japan , recent reports have indicated that the prevalence of intestinal parasites in private household dogs kept in the same area has declined in comparison with previous years [ 1,12 - 14 ] .
however , the epidemiological background is extremely important for the interpretation of results relating to canine intestinal parasites , since prevalence differs significantly according to the profiles of surveyed dogs [ 3 - 7 ] .
unfortunately , previous long - term surveillance studies in japan [ 1,12 - 14 ] have lacked data analysis based on multifactorial considerations in regard to epidemiological backgrounds .
previous our reports [ 3 - 7 ] suggest that the considering of high detective factor may be helpful for the comparison of data among differentiated studies .
the aim of this investigation was to determine the prevalence of g. intestinalis and other intestinal parasites ( isospora spp .
, t. canis , ancylostoma ( a. ) caninum , trichuris ( t. ) vulpis and strongyloides ( s. ) stercoralis ) in private household dogs of hachinohe region in aomori prefecture , japan in 1997 , 2002 and 2007 .
data were analyzed based on consideration of epidemiological backgrounds such as canine ages and origin .
fresh fecal specimens were collected from 420 , 350 and 335 private household dogs presented to individual veterinary clinics regardless of illness history and living in the hachinohe area of tohoku region in aomori prefecture of japan , in 1997 , 2002 and 2007 , respectively .
hachinohe is situated in the northern part of japan , with approximately 300,000 people living in this area .
parasitic agents in stools were detected using the formalin - ethyl acetate sedimentation technique as previously described .
obtained data was analyzed by considering the high detective factor complex for each parasitic agent , and statistical significance of results was calculated using fisher 's exact probability test . values of p < 0.05 were considered significant .
epidemiological high detective factors for each intestinal parasite of private household dogs have already been described in our previous reports [ 3 - 7 ] .
considering the high detective factor is helpful for the comparison of data among differentiated studies .
therefore , the concept of a high detective factor complex was accepted for the evaluation of the results in the present study .
the high detective factor complex for each parasite in the present study was as follows : group 1 ( g. intestinalis , isospora spp . and
s. stercoralis ) comprised dogs under 1 year old , derived from pet shops / breeding kennels and kept indoors ; group 2 ( t. canis ) comprised dogs under 1 year old , bred by private owners and kept outdoors ; and group 3 ( a. caninum and t. vulpis ) comprised dogs over 2 years old , bred by private owners and kept outdoors .
there were no significant changes in the overall prevalence of individual parasites in the three years except for isospora spp .
( table 1 ) . a significant difference ( p < 0.01 ) in isospora spp .
infection was found between 1997 ( 9.5% ) and 2007 ( 4.5% ) . in all years , all canine intestinal parasites examined in the present study ( g. intestinalis , isospora spp .
, t. canis , a. caninum , t. vulpis and s. stercoralis ) showed significantly higher ( p < 0.05 or p < 0.01 , respectively ) prevalence in groups with high detective factor complexes compared to others ( non - high detective factor complex ) , except for s. stercoralis in 2002 .
no parasites in either group of high detective factor complexes or others revealed any significant difference related to surveyed years .
in particular , the prevalence of g. intestinalis in the group with a high detective factor complex was almost unchanged over the 10 years , with high levels ( > 15.0% ) were recorded every year .
and t. canis also had no changes in the high detective factor complex group , with the prevalence > 10.0% every year .
until the present study was performed , the authors believed that the recent regional prevalence of intestinal parasites in private household dogs had decreased compared to 10 years ago , since the knowledge of owners regarding canine intestinal parasites and parasitic zoonoses has been increased provably .
several papers in japan have actually shown that the prevalence of intestinal parasites in private household dogs had decreased compared to past years [ 1,12 - 14 ] .
unexpectedly , the prevalence of all intestinal parasites studied had not changed over the past 10 years in the present study , when data was analyzed based on the concept of epidemiological high detective factor complex .
the present results indicate that profiles in surveyed dogs are important for the interpretation of data from epidemiological studies on canine intestinal parasites . although the prevalence of isospora spp .
protozoa in the present study outwardly showed a significant decline associated with the studied year in terms of overall prevalence , the real prevalence under the consideration of epidemiological factors showed no changes .
differentiation of surveyed canine populations may produce different results , as many factors related to dogs are mixed , and comparison under identical conditions is impossible .
data on canine intestinal parasites obtained without considering canine profiles seems to supply only limited information , and sometimes induces meaningless but apparently significant differences among the results . when zoonoses are discussed , epidemiological backgrounds , including information of dog - human contact are more important in public health .
even if the prevalence of zoonotic parasites in dogs is high , the problem will be minimal if contact between infected dogs and humans is infrequent .
in contrast , a serious problem is obviously present for humans if there is frequent close contact , even if prevalence is low .
certain indicators are needed to compare epidemiological data on canine intestinal parasites from differential populations .
the concept of high detective factor complex , which is supported by the results of previous reports [ 3 - 7 ] .
a surprising finding was that the protozoan g. intestinalis in the high detective factor complex group ( under 1 year old , derived from pet shops / breeding kennels and kept indoors ) recorded a high prevalence continuously over the past 10 years , with a peak of 26.2% in 2007 .
although there has been no clear evidence of giardia transmission from dogs to humans , there have been reports of suspected human cases of giardiasis from a canine source .
moreover , household dogs have the possibility of higher prevalence of g. intestinalis infection than seen in the present results .
this is because recent previous studies have demonstrated that enzyme - linked immune absorbent assay and polymerase chain reaction techniques are more sensitive to detecting giardia infection than the convenient microscopic examination method such as used in the present study .
however more sensitive methods were unused in the present study , because the certain technique was needed to evaluate the prevalence among the differentiated years .
emphasis should be placed on the fact that g. intestinalis infected dogs are often in very close contact with humans , creating a scenario for direct transmission .
t. canis is most famous nematode among the canine intestinal parasites , and the potential for zoonotic transmission is commonly recognized around the world . since numerous anthelmintic drugs for t. canis are sold in pet shops and home centers in japan , owners are easily able to obtain and treat their animals .
however , the prevalence in the group with a high detective factor complex ( under 1 year old , bred by private owners and kept outdoors ) has been steady ( > 10% ) over the past 10 years .
the risk of transmission through the contamination of t. canis eggs in the field has clearly not been reduced in the area of the present study .
the importance of regular fecal examination in household dogs needs to be recognized more among owners and clinical veterinarians .
although s. stercoralis is also a zoonotic nematode   in close contact with humans according to the epidemiological profile , prevalence has been low over the past 10 years .
s. stercoralis was detected to a limited extent in dogs derived from pet shops / breeding kennels under 1 year old .
this suggests that s. stercoralis transmission may occur continuously among young dogs in pet shops / breeding kennels .
infections , in that the infected dogs were almost all young dogs from pet shops / breeding kennels .
a. caninum and t. vulpis are mainly detected in older outdoor dogs , and the prevalence has not changed over the past 10 years .
contamination of fields via a. caninum and t. vulpis eggs is suspected to have contributed to the lack of change in the region of the present study . in conclusion ,
the present results indicate that the prevalence of g. intestinalis and other intestinal parasites in private household dogs has not always decreased , and the potential for parasitic zoonotic transmission from dogs to humans seems to remain at a higher level than we initially presumed .
we recommend careful surveillance of intestinal parasites and aggressive use of anthelminthic in private household dogs under considering the epidemiological factors .
 an epidemiological study on canine intestinal parasites was undertaken to evaluate changes in the prevalence among private household dogs from the hachinohe region of aomori prefecture , japan , in 1997 , 2002 and 2007 , using the formalin - ethyl acetate sedimentation technique . 
 the risk of zoonotic transmission from household dogs to humans was also discussed . 
 all intestinal parasites detected in the present study ( giardia intestinalis , isospora spp . 
 , toxocara canis , ancylostoma caninum , trichuris vulpis and strongyloides stercoralis ) showed no changes in prevalence over the past 10 years based on analysis considering canine epidemiological profiles . in particular , prevalence of giardia intestinalis in dogs under 1 year old , derived from pet shops / breeding kennels and kept indoors was unchanged , remaining at a high level of > 15.0% at each time point . 
 toxocara canis also showed no changes in the group of dogs under 1 year old , bred by private owners and kept outdoors , and the prevalence was > 10.0% every year . 
 the present results indicate that the prevalence of giardia intestinalis and other intestinal parasites in private household dogs has not always decreased , and the potential for direct parasitic zoonotic transmission from dogs to humans may be relatively high level , than from the environment ( indoors and outdoors ) . 
 we recommend careful surveillance of intestinal parasites and aggressive use of anthelminthic in private household dogs under considering the epidemiological factors . 
Introduction
Materials and Methods
Results
Discussion