Bull Vet Inst Pulawy 50, 143-147, 2006
SEROSURVEY OF WILD BOAR POPULATION
FOR PORCINE PARVOVIRUS
AND OTHER SELECTED INFECTIOUS DISEASES
IN LITHUANIA
RAIMUNDAS LELEŠIUS1, VILIMAS SEREIKA1,
DAINIUS ZIENIUS1 AND IRENA MICHALSKIENĖ2
1
Department of Virology, Veterinary Institute of Lithuanian Veterinary Academy,
LT-56115 Kaisiadorys, Lithuania
2
National Veterinary Laboratory, LT-08409 Vilnius, Lithuania
e-mail: [email protected]
Received for publication November 09, 2005.
Abstract
Wild boar (Sus scrofa scrofa) population in
Lithuania was tested for antibodies against porcine parvovirus
(PPV), foot and mouth disease virus (FMDV), Brucella sp.,
classical swine fever virus (CSFV), swine vesicular disease
virus (SVDV), and Aujeszky's disease virus (ADV). Blood
serum samples were collected from shot wild boars during
hunting season in 2004. Using ELISA no antibodies against
FMDV (n=504), Brucella sp. (n=23), CSFV (n=591), SVDV
(n=12), and ADV (n=24) were detected. With respect to PPV
haemagglutination inhibition test was used. Altogether 254
serum samples were tested. It was found that 67 (26.4%) wild
boars were seronegative, 64 (25.2%) had PPV antibody titres
from 1 to 5 log2 (2–32, possibly passive maternal immunity),
12 (4.7%) - from 6 to 7 log2 (64–128, possibly declining
passive maternal immunity or rising active postinfective
immunity), 30 (11.8%) - from 8 to 10 log2 (256–1 024, active
postinfective immunity), 75 (29.5%) - from 11 to 13 log2 (2
048–8 192, high active postinfective immunity) and in 6
(2.4%) boars the titre was 14 log2 (16 384, very high active
postinfective immunity). Thus, our data showed that PPV
circulates actively in Lithuanian wild boar population.
Key words: wild boars, porcine parvovirus,
epidemiology.
The wild boar is considered as a potential
carrier of viruses and bacteria pathogenic for domestic
pigs and may be also the reservoir of these pathogens.
Infections with CSFV, bovine viral diarrhoea virus
(BVDV), ADV, porcine reproductive and respiratory
syndrome virus (PRRSV), and PPV are considered the
most important diseases for swine industry (1, 4, 8).
Contacts between wild boars and domestic pigs can
result in transmission of these pathogens. It was shown
in Germany that since 1993 about 60 % of the primary
outbreaks have been linked with CSF epidemics in the
wild boar (3).
The wild boars positive for PPV have been
detected in Italy (2, 5). PPV infection is widespread on
Lithuanian swine farms and it was diagnosed also in
wild boar population (10, 11, 15).
Foot and mouth disease (FMD) is one of the
most contagious animal diseases with great economic
significance. The disease was diagnosed in cattle in
Lithuania more than 20 years ago, but so far it has never
been found in wild boars.
The aim of the investigations was to carry out
the serological examination of wild boar population in
Lithuania for PPV, FMDV, Brucella sp., CSFV, SVDV,
and ADV antibodies.
Material and Methods
Blood serum samples were collected during
hunting from shot wild boars (Sus scrofa scrofa) in
2004. Serological survey for antibodies to FMDV,
Brucella sp., ADV and SVDV was performed at the
Department of Serology (National Veterinary
Laboratory) and with respect to PPV antibodies at the
Department of Virology (LVA Veterinary Institute).
Serum samples for FMDV antibodies were
tested using the following ELISA kits: Ceditest
(Netherlands), UBI (USA) and Bommeli (Switzerland).
Ceditest and Bommeli kids were used also for the
detection of CSFV antibodies. Antibodies against
Brucella sp. were detected using ELISA kits of IDEXX
(USA) and Pourquier (France). ADV antibodies were
detected using ELISA kits of IDEXX, Pourquier and
Svanova (Sweden). SVDV antibodies were detected
using Ceditest and Cypress (Belgium) kits. Antibodies
against PPV were detected by haemagglutination
inhibition test (HI) (10).
Altogether different number of serum samples
was tested with respect to each pathogen: FMDV
144
against FMDV and CSFV (Table1). With respect to
Brucella sp., SVDV and ADV, too small number of
serum samples was tested to evaluate the
epidemiological situation of the wild boar population of
Lithuania. However, the results were negative also
(Table 1).
(n=504), Brucella sp. (n=23), CSFV (n=591), SVDV
(n=12), ADV (n=24), and PPV (n=254) (Table 1).
Results
All serum samples collected from all 10 regions
of Lithuania were found to be negative for antibodies
Table 1
Results of serological survey of wild boar population for some diseases in Lithuania in 2004
Number of positive results
Region
n
Brucella sp.
ADV
FMDV
SVDV
CSFV
Alytus
63
-
-
63
-
61
Kaunas
77
-
-
75
-
76
Klaipeda
59
4
-
26
-
56
Marijampole
85
-
-
85
-
85
Panevezys
84
-
24
63
11
71
Siauliai
58
-
-
55
-
55
Taurage
62
-
-
47
-
62
Telsiai
11
-
-
11
-
11
Utena
52
19
-
52
1
52
Vilnius
62
-
-
27
-
62
Total
613
23
24
504
12
591
n - number of animal tested.
Table 2
PPV antibodies in serum samples of wild boar population in 2004
Region
n
Titres, log2
-
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Alytus
8
7
0
0
0
0
0
0
0
0
0
0
0
1
0
0
Kaunas
52
18
0
2
4
5
2
2
0
1
3
1
4
5
5
0
Klaipeda
32
1
4
0
0
0
9
6
1
1
0
0
3
7
0
0
Marijampole
4
1
0
0
2
0
0
0
0
0
1
0
0
0
0
0
Panevezys
27
2
7
4
2
1
0
0
0
0
4
3
2
2
0
0
Siauliai
36
4
0
0
0
8
2
2
0
0
1
4
6
4
4
1
Taurage
29
4
1
2
1
2
0
0
0
1
1
4
11
0
2
0
Telsiai
5
1
0
0
0
0
0
0
0
1
0
2
0
0
1
0
Utena
8
1
0
0
0
0
0
0
0
1
0
1
0
4
1
0
Vilnius
53
28
0
0
1
5
0
1
0
0
0
0
3
8
2
5
Total
254
67
12
8
10
21
13
11
1
5
10
15
29
31
15
6
%
26.4
4.7
3.1
3.9
8.3
5.1
4.3
0.4
1.9
3.9
5.9
11.4
12.2
5.9
2.4
n - number of animal tested.
145
Table 3
Distribution of wild boars according to PPV immunity status in 2004
Region
Number (N) and percentage of samples with PPV antibodies (titres log2)
n
-
1-5
6-7
8-10
11-13
14
N
%
N
%
N
%
N
%
N
%
N
%
Alytus
8
7
87.5
-
-
-
-
-
-
1
12.5
-
-
Kaunas
52
18
34.6
13
25.0
2
3.9
5
9.6
14
26.9
-
-
Klaipeda
32
1
3.1
13
40.6
7
21.9
1
3.1
10
31.2
-
-
Marijampole
4
1
25.0
2
50.0
-
-
1
25.0
-
-
-
-
Panevezys
27
2
7.4
14
51.9
-
-
7
25.9
4
14.8
-
-
Siauliai
36
4
11.1
10
27.8
2
5.6
5
13.9
14
38.9
1
2.7
Taurage
29
4
13.8
6
20.7
-
-
6
20.7
13
44.8
-
-
Telsiai
5
1
20.0
-
-
-
-
3
60.0
1
20.0
-
-
Utena
8
1
12.5
-
-
-
-
2
25.0
5
62.5
-
-
Vilnius
53
28
52.8
6
11.3
1
1.9
-
-
13
24.5
5
9.4
Total
254
67
26.4
64
25.2
12
4.7
30
11.8
75
29.5
6
2.4
n - number of animal tested.
100
90
87.5
87.5
80
80
70
65.5
60
55.5
51.9
50
52.8
% 50
40.7
40.6
40
30
20
36.5
34.6
34.3
25
21.9
33.9
25
27.8
25
20.7
12.5
10
0 0
3.9
11.1
7.4
3.1
0
20
13.8
12.5
5.6
0
0
0 0
0 0
Telsiai
Utena
11.3
1.9
0
Alytus
Kaunas
negative
Klaipeda
Marijampole
Panevezys
passive
Siauliai
Taurage
passive-active
Vilnius
active
Fig. 1. Percentage of PPV negative and positive wild boars in different regions of Lithuania
during hunting season in 2004
The different situation was with PPV infection.
Both positive serum samples and negative ones were
found in all regions of Lithuania (Table 2). Negative
serum samples (no HI at serum dilution 1:2) ranged
from 3.1% (1 out of 32, Klaipeda region) to 87.5% (7
out of 8, Alytus region) in different regions of Lithuania
(Tables 2 and 3). Antibody titres showing active
postinfective immunity to PPV infection were found in
some serum samples of wild boars in all regions of
Lithuania (Tables 2 and 3).
Altogether it was found that 67 (26.4%) wild
boars were seronegative, 64 (25.2%) had titres from 1 to
5 log2 (1:2– 1:32, possibly passive maternal immunity),
12 (4.7%) ones had titres from 6 to 7 log2 (64–28,
possibly declining passive maternal immunity or rising
active postinfective immunity), 30 (11.8%) - from 8 to
10 log2 (256– 1 024, active postinfective immunity), 75
146
(29.5%) - from 11 to 13 log2 (2 048–8 192, high active
postinfective immunity) and in 6 (2.4%) boars the titre
was 14 log2 (16 384, very high active postinfective
immunity) (Tables 2 and 3).
The percentage of wild boars with PPV
antibody titres from 1 to 5 log2 ranged from 0% (Alytus,
Telsiai, Utena regions) to 51.9 % (Panevezys region),
with titres from 6 to 7 log2 ranged from 0% (Alytus,
Marijampole, Panevezys, Taurage, Telsiai and Utena
regions) to 21.9% (Klaipeda region) (Tables 2 and 3),
and with titres from 8 to 14 log ranged from 12.5%
(Alytus region) to 87.5% (Utena region) (Fig. 1).
Discussion
The wild boar (Sus scrofa scrofa) population
was already tested for antibodies against some
pathogens (CSFV, PPV, PRRSV, ADV) in 9 different
districts (Alytus, Joniskis, Kaisiadorys, Kaunas,
Klaipeda, Lazdijai, Marijampole, Prienai, Sakiai) of
Lithuania in 2001 (16). It was demonstrated that 1 serum
sample out of 36 (2.7%) samples tested was positive for
CSFV antibodies. The same sample was positive for
BVDV antibodies in virus neutralization test. This wild
boar was shot in Joniskis district that is near the Latvian
border. Two out of 36 (5.5%) serum samples were found
to be positive for ADV antibodies. These wild boars
were shot in Kaisiadorys and Kaunas districts. One out
of 36 serum samples (2.7%) was found to be positive for
PRRSV antibodies. This boar was shot in Sakiai district
(16). However, in 2004 no positive samples with respect
to ADV and CSFV were found. We think that study
using molecular biological methods, for example,
polymerase chain reaction (PCR) should be used to get
more reliable results. PCR can detect wild boars, which
are CSFV and BVDV carriers. These wild boars are
seronegative, but can excrete the viruses.
The high incidence of CSF in Western and
Central Europe in the present decade has once more
demonstrated the great economic impact of the disease
(7, 8). It was shown that all CSFV types circulating in
the wild boar have been isolated from domestic pigs in
the corresponding geographic regions (9).
Infection of pregnant sows by BVDV and
Border disease virus (BDV) induces changes partially
resembling those of congenital CSF. The terms BVDV
and BDVV are used to indicate that the virus was
isolated from either cattle or sheep, although these
viruses cannot be differentiated morphologically or
structurally. In pigs, pestivirus isolates are usually
CSFV. However, BDVD and BDV can be isolated from
naturally infected pigs. Harasawa (6) constructed a
phylogenetic tree of pestiviruses. His results indicated
that the genetic relationship between BDV and CSFV is
much closer than that between genotypes of various
BVDV.
The wild boar is considered to be a potential
carrier of ADV and could also function as a reservoir of
the pathogen. So far, however, little is known about the
susceptibility of the wild swine, especially the wild boar,
to ADV. Although in recent years ADV has repeatedly
been isolated from wild pigs in the USA, Italy and
Germany, data on the virulence of these isolates are
sparse. Molecular characterization of ADV isolates
obtained from wild boars in Germany has revealed a
unique DNA pattern which had not been observed in
domestic animals before. In addition, studies on the
virulence of these isolates were required to evaluate the
potential risk of ADV infections for the wild boar as
well as for the domestic pig population. ADV is usually
transmitted from feral to domestic swine at the time of
mating. This would indicate that the isolation of
domestic herds by the use of a "double fence," should be
adequate protection against reinfection with ADV (13).
Our results show that the wild boars were
negative with respect to CSFV, ADV, FMD and SVD.
However, prophylactic measures should be taken to
avoid the contacts between domestic and wild pigs,
since the situation in bordering countries: Latvia,
Poland, Belarus and Russian Kaliningrad region is
different or unclear.
In 2001, 20 out of 36 serum samples (55.5 %)
were found to be seropositive for PPV by HI in
Lithuania (16). The seropositive wild pigs were found in
8 out of 9 districts (all except Prienai). The antibody
titres ranged from 32 to 8 192.
Different results were found in studies
performed in the various countries, their regions or
periods. For example, in southcentral Spain, during
hunting season in 1999-2000, the serological survey of
serum samples (n=78) collected from European wild
boars (Sus scrofa) were tested for PPV, ADV,
Leptospira interrogans serovar pomona, Erysipelothrix
rhusiopathiae, swine influenza virus (SIV) serotypes
H1N1 and H3N2, Salmonella serogroups (B, C, D),
Brucella
sp.,
CSFV,
Haemophilus
parasuis,
Mycoplasma
hyopneumoniae,
PRRSV,
and
Streptococcus suis antibodies (17). It was found that the
boars were positive for PPV (10%), ADV (36%), L.
interrogans ser. pomona (12%), E. rhusiopathiae (5%),
SIV serotype H1N1 (4%), Salmonella serogroup B
(4%), and Salmonella serogroup C (3%) antibodies.
Another study showed the seroprevalence of 6
pathogens in hunter-harvested wild boar females in
Spain (14). The sample was representative of the
hunting harvest in the studied hunting estates. Mean
antibody prevalences were: 56.6% for PPV, 60.6% for
ADV, 51.8% for porcine circovirus type 2 (PCV2),
29.7% for Brucella sp., and 36.3% for Toxoplasma
gondii. The PRRSV antibodies were not detected. ADV
seroprevalence was associated with PPV and PCV2
seroprevalence in Spanish wild boar females (14). These
two studies showed how different numbers can be
obtained in different regions and conditions.
In other study blood samples collected from
120 wild swine (Sus scrofa) in 13 Oklahoma (USA)
counties during 1996 were tested for antibodies against
some viral and bacterial pathogens (15). PPV and SIV
antibodies were detected in 17% and 11% of the swine,
respectively. Antibodies to one or more leptospiral
serovars were found in 44% of the samples. L.
interrogans ser. bratislava (29%) and pomona (27%)
were most frequently detected serovars. Two samples
147
(2%) were positive for antibody to PRRSV. No ADV,
Brucella sp., transmissible gastroenteritis virus and
vesicular stomatitis virus antibodies were detected (15).
New et al. (12) collected blood samples from
108 wild hogs (Sus scrofa) from the Great Smoky
Mountains National Park, USA, from February to July
1990 and found PPV antibodies in 15 (14%) samples
and antibodies to one or more leptospiral serovars - in
48 (44%) samples. Thirty-nine (89%) of the 44 positive
samples reacted to 5 leptospiral serovars tested. Brucella
sp., ADV, BVDV and porcine rotavirus antibodies were
not found.
In Italy (Liguria) 96 serum samples were tested
by HI for PPV in 1992-1993. Ninety-five out of 96 had
PPV antibody titres from 32 (5 log2) up to 16 384 (14
log2). Only one sample was regarded as negative,
however, it inhibited HA in titre 16. On the other hand,
the different situation with respect to PPV was found in
Italian another study (5), in the context of "Regional
Control Program for Swine Classical Fever", in which
548 sera of wild boar, shot during hunting season in the
last three months of 1992, were examined. The sera
were tested using blocking ELISA for the detection of
SCFV, ADV, PPV, SIV type A and SVDV antibodies.
All the sera were negative for SIV type A and SVDV
antibodies and 10.7% positively reacted with CSFV,
20% with ADV and 56.7% with PPV antigens.
According to Lelesius and Sereika (11), PPV is
endemically widespread in Lithuanian swine farms and
the contact of boars with domestic pigs can be
dangerous for wild boar population and vice versa, as it
was demonstrated in the present study, PPV circulating
actively in Lithuanian wild boars is hazardous for
domestic pigs in respect to their reproductive
performance.
It should be stressed that, according to our data,
Lithuanian wild boar population is free from FMDV.
Seropositive boars were also not found in regard to
ADV, CSFV and SVDVinfection.
Acknowledgments: This study was supported
by grant from Lithuanian State Science and Studies
Foundation (Treaty No. T-80/85, 2005 04 12, “The
environment pollution of swine farms with pathogenic
microorganisms”).
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