Praca oryginalna Original paper
Bovine spongiform encephalopathy (BSE) is a fatal neurodegenerative disease characterized by a long incubation period and a gradual accumulation of an anomalous isoform of prion protein (PrPRes) in the
cen-tral nervous system causing degeneration of neurons and ultimately leading to death in all cases (12, 17). Cattle affected by BSE demonstrate chronic neuro-logical signs consisting of behavioural changes, abnor-malities of posture and movement, and hyperaesthesia (15). Diagnostics of BSE in live cattle is impossible since pathologic prion protein (PrPRes) does not
stimu-late an immune or inflammatory response in the host (16). BSE was first described in Great Britain in 1987 (17). Since then, BSE has occurred in many countries involving imported and indigenous cattle (9, 10). BSE has been identified since 1988 in Great Britain (14) and in Lithuania since 1990. In passive monitoring any person who has in their possession or charge a bovine animal suspected or being affected by BSE must re-port about the case immediately to the relative autho-rities. Since July 2001, Lithuania, like other European
countries, has begun to actively monitor BSE among specific populations of bovine animals (3).
The aim of this study was to evaluate BSE monito-ring system in Lithuania dumonito-ring the period of 2001--2006.
Material and methods
Since 2000 all cattle in Lithuania have been individually identified by ear tags. Individual data of bovine animals are collected at birth and stored in the Central Data Base of Iden-tification and Registration of bovine animals (therefore CDB). All movements of cattle are traced and recorded by competent authorities; slaughterhouses, farmers and proces-sing plants of animal by-products have access to CDB in order to check identification, age and movements of bovine animals. All slaughter products of bovine animals are identi-fied and kept at the slaughterhouse before BSE test results are obtained. All animal origin by-products are collected and processed at the processing plant.
The monitoring of cattle for the presence of BSE was divided into target groups described below (tab. 1). Healthy slaughtered bovine animals were cattle subject to normal
Analysis of BSE monitoring system in Lithuania
PETRAS MACIULSKIS, KAZIMIERAS LUKAUSKAS, ANTANAS SEDEREVICIUS, GEDIMINAS PRIDOTKAS, VAIDOTAS KIUDULAS, ALIUS POCKEVICIUS,
EUGENIJUS JONAITIS
Lithuanian Veterinary Academy, Tilzes street 18, 47181 Kaunas, Lithuania
Maciulskis P., Lukauskas K., Sederevicius A., Pridotkas G., Kiudulas V., Pockevicius A., Jonaitis E. Analysis of BSE monitoring system in Lithuania
Summary
Lithuania has been strengthening its BSE monitoring program since July 2001. A total of 264,268 cattle were examined during the period of 2001-2006. No BSE positive case was found. A total of 93.1% of healthy slaughtered cattle, 6.3% of fallen stock, 0.4% of emergency slaughtered cattle and 0.2% of cattle with clinical signs were tested at ante mortem inspection. The number of tested adult cattle has increased 4.5 times from 4.17% in 2001 to 18.88% in 2006. 2.41% adult cattle were tested in 2002, 1.97% in 2003, 10.59 % in 2004 and 18.92% in 2005. The number of tested healthy slaughtered adult cattle has increased 4 times from 4.09% in 2001 to 17.41% in 2006. 2.11% of healthy slaughtered adult cattle were tested in 2002, 1.5% in 2003, 9.96% in 2004 and 17.66% in 2005. The number of tested risk group adult cattle has increased 18 times from 0.08% in 2001 to 1.47% in 2006. 0.3% of risk group of adult cattle were tested in 2002, 0.47% in 2003, 0.63% in 2004 and 0.96% in 2005. 94.3% of all tested cattle were from 2 to 11 years old, 0.1% of them were less than 2 years old, 3.0% were 12 years old and 2.6% were 13 years old and more. 54.3% of all tested cattle were more than 5 years old. A total of 53.9% of healthy slaughtered cattle, 59.0% of fallen stock, 61.9% emergency slaughtered cattle and 62.6% of cattle with clinical signs at ante mortem inspection were more than 5 years old. Significant correlation was found between the age of healthy slaughtered cattle and emergency slaughtered cattle and cattle with clinical signs at ante mortem inspection (P < 0.05). There was no correlation between the age of fallen stock and healthy slaughtered cattle. The mean age of healthy slaughtered cattle was 6.5 years and the mean age of fallen stock was 6.7 years in 2005. Enfer TSE and Bio-Rad rapid tests were applied for BSE monitoring. Inconclusive test results were subjected to histopathological and immunocytochemical examination.
slaughter for human consumption and cattle without clinical signs of disease slaughtered in the context of a disease eradi-cation campaign other than BSE. Emergency slaughtered bovine animals were cattle subject to special emergency slaughtering. Bovine animals with clinical signs at ante mortem inspection were cattle sent for normal slaughter but suspected of suffering from a disease which is communicable to man and to animals or showing symptoms or being in a general condition such as to indicate that such a disease may occur and cattle showing symptoms of a disease or of a disorder of their general conditions which is likely to make their meat unfit for human consumption. Fallen stock was cattle that had died or been killed on the farm or in transport, but not slaughtered for human consumption nor killed in the framework of an epidemic. BSE suspects were cattle repor-ted as suspects of BSE.
The study data were extrapolated from the BSE monito-ring reports in 2001-2006. Brainstem samples from slaughte-red cattle were collected at a slaughterhouse and from dead cattle on a farm or at a processing plant of animal origin by-products using the methods and protocols laid down in the Fifth Edition of the Manual Diagnostic Tests and Vaccines for Terrestrial Animals published by the World Organisation
for Animal Health (OIE) (2). The samples were correctly marked as to identify the sampled cattle. A form which accompanies the samples was filled in and sent to National Veterinary Laboratory (thereafter NVL), which is TSE refe-rence laboratory in Lithuania. Samples from bovine animals were subjected to rapid tests (Bio-Rad and Enfer TSE) and to histopathological and immunocytochemical examination (3). Monthly reports from NVL and regional competent authori-ties were analyzed. The data were broken-down by categories of cattle tested in the framework of BSE monitoring program and distribution of cattle by year of birth and geographical origin. Records of post mortem examination were examined. Descriptive epidemiology and time series data analysis were performed to describe the trends of BSE monitoring program. Statistical analysis was done by statistical program Prism 2.01. Correlation coefficient (r) and its 95% confidence interval and P value were calculated.
Results and discussion
A total of 264,268 cattle were tested in the frame-work of BSE monitoring program during 2001-2006 in Lithuania. No BSE positive case was found. There was a significant difference between sizes of target groups of cattle tested in 2001-2006 (P < 0.05). A total of 246 018 healthy slaughtered cattle, 1206 emergency slaughtered cattle, 447 cattle with clinical signs at ante mortem inspection and 16597 fallen stocks were tested in the framework of BSE monitoring programs in 2001-2006 (fig. 1). 93.1% of all tested cattle were healthy slaughtered cattle, 6.3% fallen stock, 0.4% emergency slaughtered cattle and 0.2% cattle with clinical signs at ante mortem inspection.
The number of tested cattle increased 4.5 times from 4.17% in 2001 to 18.88% in 2006 in Lithuania. 2.41% adult cattle were tested in 2002, 1.97% in 2003, 10.59% in 2004 and 18.92% in 2005. A total of 19 282 cattle were tested in 2001, 11 136 in 2002, 9746 in 2003, 86 195 in 2005 and 87 406 in 2006 (fig. 1). The number of tested he-althy slaughtered adult cattle increased 4 times from 4.09% in 2001 to 17.41% in 2006. 2.11% of healthy slaughtered adult cattle were tested in 2002, 1.5% in 2003, 9.96% in 2004 and 17.66% in 2005. A total of 18 911 healthy slaughtered cattle were tested in the framework of BSE monitoring pro-grams in 2001, 9758 in 2002, 7418 in 2003, 47506 in 2004, 81 769 in Tab. 1. BSE monitoring of bovine animals
s l a m i n a e n i v o b f o s e ir o g e t a C Ageofbovineanimals g n ir o ti n o m e v it c A d e r e t h g u a l s y h tl a e H All>30months d e r e t h g u a l s y c n e g r e m E All>24months n o it c e p s n i m e tr o m e t n a t a s n g i s l a c i n il C All>24months k c o t s n e ll a F All>24months g n ir o ti n o m e v i s s a P s t c e p s u s E S B All 0 50 000 100 000 150 000 200 000 250 000 300 000 Healthy slaughtered 18991 9758 7418 47506 81576 80576 246018 Emergency slaughtered 29 78 113 200 331 455 1206
Clinical signs at ante mortem
inspection 0 0 28 127 137 155 447
Fallen stock 262 1300 2187 2670 3958 6220 16597
BSE suspects 0 0 0 0 0 0 0
Total 19282 11136 9746 50503 86195 87406 264268
2001y 2002y 2003y 2004y 2005y 2006y Total
Fig. 1. Number of bovine animals tested in the framework of BSE active and passive monito-ring program
2005 and 80576 in 2006. The number of tested risk group adult cattle increased 18 times from 0.08% in 2001 to 1.47% in 2006. 0.3% of risk group of adult cattle were tested in 2002, 0.47% in 2003, 0.63% in 2004 and 0.96% in 2005. A total of 371 risk group cattle were tested in 2001, 1378 in 2002, 2328 in 2003, 2997 in 2004, 4426 in 2005 and 6830 in 2006 (fig. 2). The num-ber of emergency slaughtered cattle incre-ased slightly. A total of 29 emergency cattle animals were tested in 2001, 78 in 2002, 113 in 2003, 200 in 2004, 331 in 2005 and 455 in 2006. The number of cattle with clinical signs at ante mortem inspection was low. No cattle with clinical signs at ante mortem inspection were tested in 2001 and 2002. A total of 28 cattle with clinical signs at ante mortem inspection were tested in 2003, 127 in 2004, 137 in 2005 and 155 in 2006. The number of fallen stock of bovine animals increased
signifi-cantly from 1.4% in 2001 to 7.1% in 2006. There were no BSE clinical suspects in Lithuania.
94.3% of all tested cattle were from 2 to 11 years old, 0.1% were less than 2 years old, 3.0% were 12 years old and 2.6% were 13 years old and more. 54.3% of all tested cattle were more than 5 years old. 4 year old cattle constituted the largest age group of tested bovine animals (fig. 3). The mean age of tested cattle was 7.1 years in 2001, 7.3 years in 2002, 7.0 years in 2003, 6.8 years in 2004, 6.4 years in 2005 and 5.7 years in 2006. The mean age of healthy slaughtered cattle was 7.1 years in 2001, 6.3 years in 2002, 7.1 years in 2003, 6.9 years in 2004, 6.5 years in 2005 and 5.6 years in 2006. The mean age of tested fallen stock was 5.9 years in 2001, 5.7 years in 2002, 6.7 years in 2003, 6.0 years in 2004, 6.7 years in 2005 and 7.4 years in 2006. A total of 53.9% of healthy slaughtered cattle, 59.0% of fallen stock, 61.9% emergency slaughtered cattle and 62.6% cattle with clinical signs at ante mortem inspection were more than 5 years old. Significant cor-relation was found between the age groups of healthy slaughtered cattle and emergency slaughtered cattle and cattle with clinical signs at ante mortem inspection (P < 0.05). There was no correlation between the age group of fallen stock and of healthy slaughtered cattle (fig. 4).
A total of 1.2% of all tested cattle were sampled for BSE testing in Alytus county, 14.4% in Kaunas coun-ty, 22.9% in Klaipëda councoun-ty, 5.7% in Marijampolë county, 25.2% in Panevëþys county, 4.5% in Ðiauliai county, 8.8% in Tauragë county, 2.3% in Telðiai county, 11.6% in Utena county and 3.4% in Vilnius county (fig. 5).
A total of 116 825 (44.2%) of all samples were te-sted by Enfer TSE test, 146 412 (55.4%) samples were tested by Bio-Rad test, 1006 samples were subject to
0 10 000 20 000 30 000 40 000 50 000 60 000 70 000 80 000 90 000 100 000 2001y 18911 371 19282 2002y 9758 1378 11136 2003y 7418 2328 9746 2004y 47506 2997 50503 2005y 81769 4426 86195 2006y 80576 6830 87406
Healthy slaughtered Risk group Total
Fig. 2. Number of healthy slaughtered and risk group bovine animals tested in the framework of BSE monitoring program
3.0 0.1 10.2 12.4 12.9 10.1 9.7 8.3 6.5 9.3 8.5 6.4 2.6 0.03 0 2 4 6 8 10 12 14 <2y 3y 5y 7y 9y 11y 13y+
Fig. 3. Extrapolated age distribution of bovine animals tested in the framework of BSE monitoring program in 2001-2006 in Lithuania, y = year
0
<2y 2y 3y 4y 5y 6y 7y 8y 9y 10y 11y 12y 13y+ 2 4 Unknown 6 8 10 12 14 16 Healthy slaugtered Fallen stock Emergency slaughtered With clinical signs at ante mortem inspection
Fig. 4. Extrapolated age distribution of target groups of bovine animals tested in the framework of BSE monitoring program
histopathological examination and 25 samples were subject to immunocytochemical examination (fig. 6). There were no significant correlation between the number of healthy slaughtered and fallen stock cattle tested monthly in 2005-2006 (P > 0.05). Seasonal dif-ferences were noted between the number of sampled healthy slaughtered and fallen stock cattle in 2004-2005 and 2005-2006 (fig. 7).
Analysis of post mortem records revealed that the majority of cattle died from the following diseases: nervous ketoses, ruminal tympany, ruminal acidosis, abomasal dislocation, rabies, parturient paresis, abo-masal ulcers, mastitis, traumatic reticulitis, postope-rative septicaemia, trauma, poisonings and pathologi-cal parturition.
Until 1999, epi-demiological stu-dies on BSE were based on a manda-tory reporting sys-tem of clinically suspected bovine animals (11). The new generation of rapid tests for de-tecting the protein resistant prion protein (PrPRes) in
brain tissue has made it possible to test large numbers of samples, and even poor quality samples, in a short period of time (13). Enfer TSE and Bio-Rad rapid tests were applied for BSE monitoring in Lithuania. All in-conclusive test re-sults were subjected to histopathological and immunocytochemical examination. Since the start of an expanded monitoring program on BSE in 2001, 264 268 cattle have been tested. No BSE case has been diagnosed. The surveillance involves active monitoring of healthy slaughtered cattle, fallen stock, emer-gency slaughtered cattle and cattle with clinical signs at ante mortem inspection. BSE monitoring programs facilitate comparisons between the same target group over the monitoring years and within the same age group. Risk group cattle appeared to have a significantly higher prevalence of BSE than healthy cattle (12). In Lithuania the percen-tage of tested healthy slaughtered and risk cattle compared to the adult population was significantly lower than in EU countries. In EU 20.92% of adult cattle were tested in 2001 (EU15), 26.26% in 2002 (EU15), 24.66% in 2003 (EU25), 25.5% in 2004 (EU25) and 23.51% in 2005 (EU25), (4-8). In Lithu-ania 4.17% of adult cattle were tested in 2001, 2.43% in 2002, 1.97% in 2003, 10.59% in 2004, 18.62% in 2005 and 18.88% in 2006. Therefore the difference in the number of tests in risk cattle was rather signifi-cant. In EU 1.92% of adult risk cattle were tested in 2001, 3.13% in 2002, 3.26% in 2003, 3.42% in 2004 and 3.47% in 2005 (4-8). In Lithuania 0.08% of adult risk cattle were tested in 2001, 0.3% in 2002, 0.47% in 2003, 0.63% in 2004, 0.96% in 2005 and 1.47% in 2006. Inadequate financing in 2001-2004 had a nega-tive impact on the BSE monitoring program. 2003 was
0 10 000 20 000 30 000 40 000 50 000 60 000 70 000 80 000 90 000 100 000 2001y 562 2431 3665 1477 6024 2431 1013 320 698 661 19282 2002y 315 1383 1479 1237 3592 1045 922 204 435 524 11136 2003y 160 797 1921 812 3311 913 707 456 215 454 9746 2004y 769 6615 11574 3103 14690 2539 5764 1025 1732 2692 50503 2005y 724 13085 22790 4162 17985 2606 8089 1409 12633 2663 86195 2006y 610 13683 19149 4195 20946 2465 6859 2536 15025 1938 87406 Alytus Kaunas pëdaKlai- Marijam-polë Pane-vëþys Ðiauliai Tauragë Telðiai Utena Vilnius Total
Fig. 5. Number of bovine animals tested in the framework of BSE monitoring program in Counties of Lithuania 0 10 000 20 000 30 000 40 000 50 000 60 000 Enfer TSE 19110 5732 2860 4556 51157 33410 Bio-Rad 0 4865 6591 45941 35023 53992 Histopathology 172 539 295 0 0 0 IHC 0 0 0 6 15 4
2001y 2002y 2003y 2004y 2005y 2006y
the worst for the BSE monitoring. The year 2005 was the first year of full BSE monitoring of healthy slaugh-tered cattle in Lithuania. However, the percentage of tested adult slaughtered cattle in 2005 was lower than EU mean average. The number of adult fallen stock has been increasing from 2004, but still it remains lower than the EU average. The mean incubation period of BSE is estimated to be approximately five years (1). The mean age of healthy slaughtered cattle in Lithu-ania was 6.5 years, meanwhile in the EU (EU15) it was 7.9 years in 2005 (8). The mean age of fallen stock in Lithuania was 6.7 years while in the EU it was 10.1 years in 2005 (8). It shows that cattle in other EU co-untries have been used longer than in Lithuania. How-ever, the majority of tested cattle in Lithuania were older than the mean incubation period of BSE. The number of tested cattle in counties was significantly different and it depended on the location of cattle ghterhouses (fig. 5). The majority of cattle were slau-ghtered in Kaunas, Klaipëda, Panevëþys and Utena counties. BSE was differentiated mainly from meta-bolic and posparturient disorders, and rabies.
Conclusions
The survey of BSE monitoring systems in Lithuania was the first attempt to evaluate the various data pro-vided by the mandatory reporting system. The study gave a precise estimation of the size of targeted groups of cattle monitored for BSE. In recent years BSE monitoring systems have made it possible to check all adult cattle at the time of slaughter or death. Analysis of all these data helps to detect the trends of BSE mo-nitoring system, investigate risk factors and determine the effective control measures for the disease. The cattle population of Lithuania is still free from BSE. Cattle cohorts born at the end of the nineteen-nineties did not carry a risk for human beings.
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Authors address: Dr. Petras Maciulskis, Lithuanian Veterinary Acade-my, Tilzes 18, 47181, Lithuania; e-mail: maciulskis@lvvpi.lt
Fig. 7. Number of monthly tested bovine animals in 2005-2006
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10 000
2005y Risk group 256 304 358 399 480 394 373 367 376 455 503 359
2005y Healthy slaugtered 7306 6236 6996 5647 6437 6486 7000 7335 7877 8057 7161 5231
2006y Risk group 395 489 714 570 697 589 483 489 586 637 634 436
2006y Healthy slaughtered 4020 4861 6336 5764 7382 6441 7754 6236 7153 8709 8881 7039
