specimens : the present study was conducted between february 2010 and 
 august 2011 in 10 swine commercial herds in the high density pig raising areas in thailand 
 ( i.e. , herds a to j ) . aborted fetuses ( n=32 ) , mummified fetuses ( n=30 ) and stillborn piglets 
 ( n=27 ) were collected from 89 landrace x yorkshire crossbred gilts / sows . the specimens were 
 collected from the herd , placed on ice and transported to the laboratory within 24 hr . herd location and general management : the herds were located in the 
 eastern ( a and g ) , middle ( b , d , e , i and j ) , northeastern ( c and h ) and southern ( f ) parts 
 of thailand . all herds were breeding herds with 900 to 5,000 sows per herd and were defined 
 as prrs virus - positive herds according to the results of a commercial elisa test 
 ( herdchek prrsv antibody test kit 2xr , idexx laboratories , inc . , 
 westbrook , me , u.s.a . ) and a reverse transcription polymerase chain reaction ( rt - pcr ) of the 
 herd s monitoring data . gilts and sows were 
 housed in a conventional open housing system with equipment , e.g. , water sprinklers , fans 
 and roofs with heat reflecting material , to reduce the impact of high temperatures . on 
 average , the outdoor 24-hr average temperature and humidity in these area in the hot ( 15 
 february to 14 june ) , rainy ( 15 june to 14 october ) and cool ( 15 october to 14 february ) 
 seasons were 29.4c/71.7% , 28.5c/78.1% and 26.4c/68.1% , respectively . the average 
 minimum - maximum daily temperatures were 24.634.9c , 24.833.0c and 21.432.1c in the hot , 
 rainy and cool seasons , respectively . in general , gilts entered the gilt pool at a body 
 weight of 80100 kg . feeding was provided twice a day at about 3 kg of feed / animal / day . in general , the feed 
 ( corn - soybean - fish based ) contained 1618% crude protein , 3,0003,250 kcal / kg metabolisable 
 energy and 0.851.10% lysine . the herd management recommended breeding replacement gilts 
 from 32 weeks of age onwards at the second or a later estrus and at a body weight of at 
 least 130 kg . all herds used conventional artificial insemination . gilts and sows were 
 routinely vaccinated against foot - and - mouth disease virus , classical swine fever virus , 
 aujeszky s disease virus and porcine parvovirus . herds a , b , c , d , e and f did not vaccinate 
 gilts and sows against prrs mlv vaccine ( n=66 ) , while herds g , h , i and j ( n=23 ) vaccinated 
 all gilts and sows with prrs mlv vaccine ( ingelvac prrs mlv , 
 boehringer - ingelheim vetmedica inc . , st . joseph , mo , u.s.a . [ herd g , n=9 ] or 
 amervac , laboratories hipra , girona , spain [ herds h , i and j , n=14 ] ) . among 
 the prrs - mlv - vaccinated herds , the gilts and sows were routinely vaccinated against prrs mlv 
 vaccine every 34 months . historical data and post - mortem examination : historical data for all 
 specimens including herd , animal identity , breed , vaccination protocol , parity number and 
 date of mating , farrowing or abortion were collected . the age of the aborted fetuses and 
 stillborn piglets were defined as the interval from mating to abortion or from mating to 
 farrowing , respectively . the 
 age of the mummified fetuses was estimated from crl : age of fetus=21.07 + ( 3.11  crl ) , 
 where crl was the fetal body length ( from crown or frontal crest to anus in cm ) . tissue samples , including lung , liver , spleen , 
 thymus , tonsil , lymph node and umbilical cord , were collected from stillborn piglets and 
 aborted fetuses and were kept at 80c until rna extraction . for mummified fetuses , only 
 lung , liver and spleen were collected . the dead fetuses were classified into two age groups : 
 < 70 days and 70 days . the prevalence of prrs virus detection was compared between groups 
 ( see below ) . viral rna extraction and cdna synthesis : the pool organs ( 2.0 g ) from each 
 case were homogenized and suspended in phosphate buffered saline ( pbs ) solution ( 10.0% w / v ) . 
 the suspension was left on ice for sedimentation . the supernatant was collected and 
 subjected to rna extraction using a commercial kit ( nucleospin rna virus test 
 kit , macherey - nagel inc . , briefly , rna virus was lysed , bound to the silica 
 membrane and washed . the rna was eluted from the silica membrane with 50 l 
 of rnase - free water . the concentration of the extracted rna was measured by using thermo 
 scientific nanodrop 2000 ( thermo fisher scientific , wilmington , de , u.s.a . ) . the rna from 
 each sample was diluted with rnase - free water to prepare 500 ng rna per 
 reaction and was subjected to cdna synthesis using omniscript reverse 
 transcriptase ( qiagen , hilden , germany ) . briefly , a 20 l reaction 
 ( i.e. , 0.5 m dntp , 1 m random primer , 10 units of rnase 
 inhibitor [ ribolock rnase inhibitor , fermentas inc . , glen burnie , maryland , 
 u.s.a . ] , 4 units of reverse transcriptase and rna template from each sample in the kit s 
 buffer ) was incubated at 37c for 1 the synthesized cdna was kept at 20c until the 
 quantitative polymerase chain reaction ( qpcr ) was performed . quantitative polymerase chain reaction : the qpcr was carried out on orf7 
 of the prrs viral genome using real - time polymerase chain reaction technique using a 
 commercial kit ( express qpcr supermix universal , invitrogen , carlsbad , ca , 
 u.s.a . ) . the primer sequences ( us align eu forward and reverse primer , which yielded 96 bp 
 for genotype 1 and 105 bp for genotype 2 ) and fluorogenic probe sequences used were taken 
 from a previous study . the fluorescent dyes 
 labeling the probes for genotypes 1 and 2 detection were cyanine 5 ( cy5 ) and 
 6-carboxy - fluorescine ( fam ) , respectively . the reactions for genotypes 1 and 2 detection 
 were performed separately . each 20 l reaction was composed of 10 
 l of express qpcr super mix universal , 1.25 m of us 
 align eu forward primer , 1.25 m of us align eu reverse primer , 0.5 
 m of genotypes 1 and 2 probe and 5 l of cdna template . the qpcr was carried out using rotor - gene rg-3000 ( corbett research , sydney , australia ) at 
 50c for 2 min , 95c for 2 min and 40 cycles of 95c for 15 sec , 50c for 20 sec and 60c 
 for 30 sec . the known serial concentrations , i.e. , 10 , 10 , 
 10 , 10 and 10 copies/l of genotypes 
 1 and 2 prrs viral cdna were used as a positive control , and the cycle threshold ( ct ) values 
 were used to determine the standard curve . a negative control was performed using rnase - free 
 water instead of cdna template . the ct values of each sample were plotted on the standard 
 curve and were determined the amount of copy number ( copies/l ) using 
 rotor - gene real - time analysis software 6.0 ( corbett research ) . the amounts ( i.e. , copy 
 number ) of prrs virus in the samples were transformed into logarithms ( log10 ) for 
 further analyses . statistical analyses : statistical analyses were performed using 
 statistical analysis system ( sas ) version 9.0 ( sas institute inc . , cary , nc , u.s.a . ) . descriptive statistics ( means  standard deviation ) were conducted for the continuous data , 
 i.e. , gestation length and copy number of prrs virus ( log ) . the percentage of prrs virus detection was 
 compared among groups of types of specimen ( aborted fetuses , mummified fetuses and stillborn 
 piglets ) , prrs mlv vaccination ( yes , no ) and parity number ( 0 , 1 , 24 , 511 and unknown 
 parity ) by using r  k contingency table and  analyses . the copy number of prrs 
 virus was compared among types of specimen , prrs mlv vaccination and sow s parity number by 
 using general linear model procedure ( proc glm ) . least - squares means were obtained from each 
 class of the factors and were compared by using least significant difference ( lsd ) test . on average , the ages of aborted fetuses , mummified fetuses and stillborn piglets were 73.9 
  26.4 ( range 31105 days ) , 101.0  18.9 days ( range 62119 days ) and 114.4  1.7 days 
 ( range 111116 days ) , respectively . prrs virus detection : prrs virus was detected in 67.4% ( 60/89 ) of the 
 specimens . the genotype of the detected prrs virus included genotype 1 ( eu ) 19.1% ( 17/89 ) , 
 genotype 2 ( na ) 25.8% ( 23/89 ) and mixed genotypes 22.5% ( 20/89 ) ( p=0.316 ) . the percentage of prrs virus detection in each type of specimen is presented in table 1table 1.the percentage of porcine reproductive and respiratory syndrome ( prrs ) virus 
 detection in aborted fetuses , mummified fetuses and stillborn pigletsspecimennprrs virus detectiongenotypes of prrs virusgenotype 1genotype 2mixedaborted fetuses3221/32 ( 65.6%)5/32 ( 15.6%)9/32 ( 28.1%)7/32 ( 21.9%)mummified fetuses3019/30 ( 63.3%)7/30 ( 23.3%)6/30 ( 20.0%)6/30 ( 20.0%)stillborn piglets2720/27 ( 74.1%)5/27 ( 18.5%)8/27 ( 29.6%)7/27 ( 25.9%)total8960/89 ( 67.4%)17/89 ( 19.1%)23/89 ( 25.8%)20/89 ( 22.5%)a , b ) different superscript letters within columns indicate statistically significant 
 differences ( p<0.05 ) .. as can be seen from the table , prrs virus was detected in all types of the 
 specimens . the percentages of prrs virus detection were 65.6% ( 21/32 ) , 63.3% ( 19/30 ) and 
 74.1% ( 20/27 ) in aborted fetuses , mummified fetuses and stillborn piglets , respectively 
 ( p=0.664 ) . the percentage of prrs virus detection in two different age 
 groups of the fetuses ( < 70 and 70 days ) is presented in table 2table 2.the percentage of porcine reproductive and respiratory syndrome ( prrs ) virus 
 detection by age of fetusesage of fetusesnprrs virus detectiongenotypes of prrs virusgenotype 1genotype 2mixed<70 days2011/20 ( 55.0%)0/20 ( 0.0%)7/20 ( 35.0%)4/20 ( 20.0%)70 days6949/69 ( 71.0%)17/69 ( 24.6%)16/69 ( 23.2%)16/69 ( 23.2%)total8960/89 ( 67.4%)17/89 ( 19.1%)23/89 ( 25.8%)20/89 ( 22.5%)a , b ) different superscripts within columns indicate statistically significant 
 differences ( p<0.05 ) .. on average , the percentages of prrs virus detection in the fetuses < 70 
 days of age tended to be lower than that of the fetuses 70 days of age ( 55% [ 11/20 ] versus 
 71.0% [ 49/69 ] , p=0.179 ) . the age of the fetuses with prrs virus detection 
 did not differ significantly compared to the fetuses without prrs virus detection ( 95.9  
 26.0 days versus 88.6  25.7 days , p=0.336 ) . nevertheless , the age of 
 fetuses with prrs virus detection varied from 31 to 119 days . the fetal age in relation to 
 prrs virus detection is displayed in table 
 3table 3.the means age of the fetuses in porcine reproductive and respiratory syndrome 
 ( prrs ) virus positive and negative specimensspecimenprrs virus negativeprrs virus positivenage of fetusesnage of fetusesaborted fetuses1171.4  22.32175.3  29.0mummified fetuses1194.1  23.519104.2  16.1stillborn piglets7113.2  1.920115.0  1.3total2988.6  25.76095.9  26.0a , b ) different superscripts within rows indicate statistically significant 
 differences ( p<0.05 ) . a , b ) different superscripts within columns 
 indicate statistically significant differences ( p<0.05 ) .. the percentage of prrs virus detection varied among the herds from 0.0% to 
 100.0% ( p=0.001 ) ( table 
 4table 4.the percentage of porcine reproductive and respiratory syndrome ( prrs ) virus 
 detection in prrs virus non - vaccinated herds ( n=66 ) and in prrs - modified lived virus 
 vaccinated herds ( n=23)herdsnprrs virus detectionprrs virus detection by genotypesgenotype 1genotype 2mixednon - vaccinated herds6645/66 ( 68.2%)12/66 ( 18.2%)20/66 ( 30.3%)13/66 ( 19.7%)herd a4332/43 ( 74.4%)4/43 ( 9.3%)17/43 ( 39.5%)11/43 ( 25.6%)herd b126/12 ( 50.0%)3/12 ( 25.0%)2/12 ( 16.7%)1/12 ( 8.3%)herd c55/5 ( 100.0%)4/5 ( 80.0%)0/5 ( 0.0%)1/5 ( 20.0%)herd d32/3 ( 66.7%)1/3 ( 33.3%)1/3 ( 33.3%)0/3 ( 0.0%)herd e20/2 ( 0.0%)0/2 ( 0.0%)0/2 ( 0.0%)0/2 ( 0.0%)herd f10/1 ( 0.0%)0/1 ( 0.0%)0/1 ( 0.0%)0/1 ( 0.0%)vaccinated herds2315/23 ( 65.2%)5/23 ( 21.7%)3/23 ( 13.0%)7/23 ( 30.4%)herd g99/9 ( 100.0%)4/9 ( 44.4%)0/9 ( 0.0%)5/9 ( 55.6%)herd h74/7 ( 57.1%)1/7 ( 14.3%)3/7 ( 42.9%)0/7 ( 0.0%)herd i50/5 ( 0.0%)0/5 ( 0.0%)0/5 ( 0.0%)0/5 ( 0.0%)herd j22/2 ( 100.0%)0/2 ( 0.0%)0/2 ( 0.0%)2/2 ( 100.0%)total8960/89 ( 67.4%)17/89 ( 19.1%)23/89 ( 25.8%)20/89 ( 22.5% ) ) . nevertheless , the prrs virus could be detected in both prrs virus 
 non - vaccinated sows ( 45/66 , 68.2% ) and in prrs - mlv - vaccinated sows ( 15/23 , 65.2% ) 
 ( p=0.794 ) ( table 4 ) . the 
 percentage of prrs virus detection did not differ among parity number of sows 
 ( p=0.983 ) . prrs virus was detected by 66.7% ( 2/3 ) , 68.4% ( 13/19 ) , 62.5% 
 ( 10/16 ) , 64.7% ( 11/17 ) and 70.6% ( 24/34 ) of the fetuses collected from the gilts and the 
 sows parity numbers one , 24 , 511 and unknown parity , respectively . a , b ) different superscript letters within columns indicate statistically significant 
 differences ( p<0.05 ) . a , b ) different superscripts within columns indicate statistically significant 
 differences ( p<0.05 ) . a , b ) different superscripts within rows indicate statistically significant 
 differences ( p<0.05 ) . a , b ) different superscripts within columns 
 indicate statistically significant differences ( p<0.05 ) . quantitative pcr detection of prrs virus : the amount ( i.e. , copy number ) 
 of prrs virus detected by qpcr is presented in table 
 5table 5.the means of copy numbers ( log10 ) of porcine reproductive and 
 respiratory syndrome ( prrs ) virus in prrs virus positive aborted fetuses , mummified 
 fetuses and stillborn pigletsspecimennumber of prrs virus positivegenotype 1genotype 2ncopy numberncopy numberaborted fetuses211212.3  2.51612.0  1.3mummified fetuses191310.8  2.41210.4  1.5stillborn piglets201212.2 3.11511.2  1.4total603711.7  2.74311.3  1.5a , b ) different superscripts within columns indicate statistically significant 
 differences ( p<0.05 ) .. on average , the amount of genotype 1 prrs virus did not differ significantly 
 among aborted fetuses ( 12.3  2.5 copies/l ) , mummified fetuses ( 10.8  2.4 
 copies/l ) and stillborn piglets ( 12.2  3.1 copies/l ) 
 ( p=0.373 ) . however , aborted fetuses had a higher amount ( 12.0  1.3 
 copies/l ) of genotype 2 prrs virus than mummified fetuses ( 10.4  1.5 
 copies/l , p=0.004 ) , but did not differ significantly 
 compared to stillborn piglets ( 11.2  1.4 copies/l , 
 p=0.345 ) . the amount of prrs virus in prrs - mlv non - vaccinated and 
 vaccinated sows was not different in both genotype 1 ( 11.7  2.7 and 11.8  2.9 
 copies/l , p=0.689 ) and genotype 2 ( 11.2  1.6 and 11.7 
  1.3 copies/l , p=0.273 ) . the amount for both genotypes 1 
 and 2 of prrs virus did not differ significantly among parity number of sows . in gilts and 
 sows , parity numbers one , 24 , 511 and unknown parity , the amount of prrs virus genotype 1 
 was 10.2  1.9 , 10.9  1.7 , 12.1  2.9 , 11.8  3.0 and 12.2  3.0 
 copies/l , respectively ( p=0.655 ) . likewise , the amount of 
 prrs virus genotype 2 in gilts and sows parity numbers one , 24 , 511 and unknown parity was 
 11.0  0.0 , 11.0  1.7 , 11.7  1.7 , 11.4  1.5 and 11.2  1.4 copies/l , 
 respectively ( p=0.716 ) . a , b ) different superscripts within columns indicate statistically significant 
 differences ( p<0.05 ) . it 
 was found that prrs virus was detected in as high as 67.4% of the fetuses collected from 
 gilts and sows with reproductive failure . the present study confirms that prrs virus 
 detection is strongly associated with reproductive failures in gilts and sows in the thai 
 swine commercial herds . this is in agreement with our previous clinical study on 
 reproductive data in a commercial swine herd in thailand . in the previous study , although the homologous strain of prrs mlv vaccine was 
 implemented , some reproductive failures remained [ 6 , 
 7 , 18 ] . this 
 can be explained by the finding of the present study that prrs virus still exists and 
 circulates within the herds , although vaccination has been undertaken . interestingly , the 
 prevalence of prrs virus detection did not differ significantly between prrs mlv vaccinated 
 herds and non - vaccinated herds ( i.e. , 65.2% and 68.2% , respectively ) . this indicates that 
 prrs - mlv vaccination does not reduce the transplacental infection of the prrs virus under 
 field conditions . therefore , although vaccination has been done , herd health monitoring , 
 sanitation , biosecurity and general management are still important to minimize the viral 
 circulation and the clinical signs of the prrs virus infection . in the present study , the age of the fetuses with prrs virus detection varied from 31 to 
 119 days this is in agreement with the previous studies that prrs virus infection can occur 
 at any stage of gestation [ 9 , 29 ] . nevertheless , the sows with gestation length of 90 days are more 
 sensitive to prrs virus infection than sows with gestation length < 90 days [ 12 , 22 ] . in the 
 present study , the prevalence of prrs virus detection tended to be higher in fetuses aged 
 70 days compared to fetuses aged < 70 days . in general , the fetus ages > 70 days have 
 had an immune competency . this , in fact , increases the potential of the viral clearance from 
 the fetal tissue by the fetal immune system . however , it is known that prrs virus infection 
 and replication commonly occurred during the late state of gestation . thus , the viral detection is more common in the fetuses aged 70 
 days . the mechanism of reproductive failure ( i.e. , abortion and fetal death ) caused by prrs 
 virus infection is still unclear [ 3 , 12 ] . however , it was found that prrs virus may induce 
 apoptosis in prrs virus infection site ( i.e. , endometrial connective tissues and fetal 
 placenta ) and subsequently caused reproductive disorders , e.g. , abortion , premature 
 farrowing , stillbirth and prrs virus - infected live born piglets . prrs virus is able to replicate in the endometrium , cross the 
 maternal epithelium , replicate in the fetal placenta and reach the fetal internal organs 
 [ 12 , 20 ] . 
 additionally , sows experimentally infected with field strain of prrs virus can farrow both 
 non - infected and infected fetuses , and the infected fetuses are able to shed the virus 
 . moreover , prrs virus has been detected in 
 many tissues of the infected fetus , i.e. , umbilical cord , heart , lung , lymph node , spleen , 
 tonsil and thymus [ 3 , 22 ] . of these organs , the thymus is the primary site of the prrs virus replication 
 [ 3 , 22 ] . in 
 the present study , thymus thus , the amount 
 of prrs virus in mummified fetuses tended to be lower than that of the aborted fetuses and 
 stillborn piglets . furthermore , it has been demonstrated that prrs virus can be diminished 
 under dry or a low humidity conditions [ 5 , 21 ] . therefore , the amount of virus might be low in the 
 mummified fetus samples . in the present study , the prevalence of prrs virus from the dead fetuses did not differ 
 significantly among parity groups of sows . this might be due to the fact that the specimens 
 were collected only from the females that had reproductive failures . in the present study , 
 20% of the specimens had co - infection of genotypes 1 and 2 of prrs virus . this finding is 
 not surprising , because multiple isolates of the prrs virus strains in infected piglets had 
 been reported earlier , i.e. , a so called  quasispecies  . interestingly , genetic combination among these multiple isolates has occurred 
 and subsequently caused atypical clinical symptoms of prrs virus infection under field 
 conditions [ 17 , 22 , 28 ] . this may result in genetic 
 diversity of the prrs virus under field conditions , which may compromise immunological 
 protection after prrs  mlv vaccination . in the present study , vaccination was conducted by 2 different commercial vaccines , one 
 from european and another one from north american prrs virus strain . nowadays , both strains 
 of the prrs - mlv are used on most continents , because a strict geographical genotype barrier 
 no longer exists . in thailand , both vaccine 
 strains have been used in swine commercial herds for over 10 years . in fact , mixed genotypes 
 of prrs virus are commonly found in the herds using either european or north american 
 prrs - mlv strains ( table 4 ) . for instance , in a 
 herd using north american prrs - mlv strain , both genotypes of the prrs virus are detected in 
 5 of 9 samples . likewise , in a herd using european prrs virus strain , both genotypes of the 
 prrs virus these findings indicate that the prrs viral shedding can be found in any 
 vaccinated herds with regardless to the vaccine strain used . earlier studies have shown that 
 prrs - mlv is able to induce virus neutralizing antibodies , prevent prrs virus replication in 
 target cells , viremia and reduce clinical symptoms [ 11 , 23 ] . furthermore , experimental 
 inoculation with either european or north american strains of prrs - mlv in gestating gilts 
 and sows cause trans - placental infection to the fetus [ 16 , 23 ] . therefore , the prrs virus isolated 
 from the fetus can be either vaccine or field strains . nevertheless , in the present study , 
 no significant difference on the prevalence of prrs virus detection between vaccinated and 
 non - vaccinated herds was found . under field condition , many strategies including prrs - mlv vaccination have been used to 
 control infertility problems caused by prrs virus . in thailand , .   found that reproductive 
 performance of sows in selected prrs virus seropositive herds with prrs - mlv vaccination were 
 superior compared with those in prrs - mlv non - vaccinated herds . the reason might be that 
 prrs - mlv vaccination is able to reduce viral shedding and partially prevent transplacental 
 transmission , and thus , reduced infertility 
 problems caused by the field strain prrs virus infection nevertheless , although a number of 
 comprehensive studies on the effect of prrs - mlv vaccination on reproductive performance of 
 sows have been conducted worldwide , the results are still controversial ( i.e. , negative , 
 neutral and positive effects have been found ) [ 11 , 
 18 , 19 , 
 23 ] . .   demonstrated that prrs virus 
 antigen was detected in the uterine tissues in gilts culled due to reproductive failure in 
 both prrs - mlv vaccinated and non - vaccinated herds . furthermore , vertical transmission of 
 prrs virus has been clearly demonstrated [ 11 , 12 , 23 ] . therefore , it is not surprising to detect the prrs virus in aborted fetuses , mummified 
 fetuses or stillborn piglets under field condition , although prrs - mlv has been 
 implemented . it can be concluded that prrs virus was frequently detected in aborted fetuses , mummified 
 fetuses and stillborn piglets in swine commercial herds in thailand , both in prrs - mlv 
 vaccinated herds and non - vaccinated herds . this indicated that the dead fetuses as well as 
 stillborn piglets are important sources of the prrs virus within the herd . therefore , the 
 routine management of dead fetuses and stillborn piglets in prrs virus - positive herds should 
 be emphasized in order to minimize the viral load and the viral shedding within the 
 herd .
the objective of the present study was to investigate the prevalence of porcine 
 reproductive and respiratory syndrome ( prrs ) virus detection in aborted fetuses ( n=32 ) , 
 mummified fetuses ( n=30 ) and stillborn piglets ( n=27 ) from 10 swine herds in thailand 
 using quantitative polymerase chain reaction ( qpcr ) . 
 pooled organs and umbilical cord from 
 each fetus / piglet were homogenized and subjected to rna extraction and cdna synthesis . 
 the 
 qpcr was carried out on the orf7 of the prrs viral genome using fluorogenic probes for 
 amplified product detection . 
 the results revealed that 67.4% ( 60/89 ) of the specimens 
 contained prrs virus . 
 the virus was found in 65.6% ( 21/32 ) of aborted fetuses , 63.3% 
 ( 19/30 ) of mummified fetuses and 74.1% ( 20/27 ) of stillborn piglets 
 ( p=0.664 ) . 
 genotype 1 , genotype 2 and mixed genotypes of prrs virus were 
 detected in 19.1% ( 17/89 ) , 25.8% ( 23/89 ) and 22.5% ( 20/89 ) of the specimens , respectively 
 ( p=0.316 ) . 
 prrs virus antigen was retrieved from both 
 non - prrs - vaccinated herds ( 68.2% , 45/66 ) and prrs - vaccinated herds ( 65.2% , 15/23 ) 
 ( p=0.794 ) . 
 these findings indicated that these specimens are important 
 sources of the prrs viral load and the viral shedding within the herd . 
 thus , intensive 
 care on the routine management of dead fetuses and stillborn piglets in prrs 
 virus - positive herds should be emphasized .