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Original research
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November and December, 1996 |
Intradermal vaccination against pseudorabies virus and swine influenza in
growing/finishing pigs
Ioannis C. Papatsas, DVM; Spiros C. Kyriakis, DVM, PhD; Orestis Papadopoulos,
DVM, PhD; Kriton J. Sarris, DVM, PhD; Stefanos Lekkas, DVM, PhD
ICP, SCK: Clinic of Medicine, Faculty of Veterinary Medicine, University
of Thessaloniki, 540 06 Macedonia, Greece; OP, SJK: Laboratory of Microbiology
and Infectious Diseases, Faculty of Veterinary Medicine, University of Thessaloniki;
SL: Laboratory of Pathology, Faculty of Veterinary Medicine, University
of Thessaloniki, Greece
Copyright (C) 1996, American Association of Swine Practitioners.
Also available in PDF format.
Summary
Objective--To investigate the effect of vaccination against pseudorabies
virus (PRV) and swine influenza virus (SIV) in growing/finishing pigs on
growth performance parameters.
Methods--In a herd free of porcine reproductive and respiratory
syndrome virus (PRRSV), 300 growing/finishing pigs were vaccinated according
to one of five protocols: 1) a single PRV vaccination, 2) a double SIV vaccination,
3) a single PRV and a double SIV vaccination, 4) a double PRV and a double
SIV vaccination, and 5) no vaccination (control). Average daily gain (ADG),
average total feed consumption (ATFC), feed conversion ratio (F:G), and
pathological and bacteriological findings were compared among treatment
groups.
Results--Pigs vaccinated twice against PRV and SIV had significantly
better ADG, ATFC, and F:G than all other treatment groups. Twice-vaccinated
pigs also had significantly lower lung lesion scores. Bacteriological examination
revealed the presence of secondary bacterial pathogens, such as Pasteurella
multocida, Staphylococcus spp and Proteus spp, in lungs
of all treatment groups except those twice vaccinated against PRV and SIV.
Implications--Double intradermal vaccination of pigs against both
PRV and SIV may improve growth performance and may reduce the impact of
secondary bacterial pathogens on lungs.
Keywords: swine, pseudorabies virus, swine influenza virus, growth
Received: April 17, 1996
Accepted: August 12, 1996
Pseudorabies virus (PRV) (Aujeszky's disease) and
swine influenza are viral respiratory diseases of major economic importance
for the swine industry worldwide.1-6 Both PRV and SIV predispose
swine to secondary bacterial and viral infections, although the severity
of the disease depends on the health status of the infected farm.1,3-5,7
Severe respiratory disease and increased production losses have been reported,
for example, when viral respiratory infections, especially swine influenza
virus (SIV) infection, are combined with porcine reproductive and respiratory
syndrome virus (PRRSV).8,9
Growing/finishing pigs that received intranasal and parenteral vaccination
prior to being challenged with PRV had reduced weight loss and significantly
shorter periods of arrested growth compared to unvaccinated animals.10-13
Moreover, animals twice vaccinated against PRV had higher antibody titers
at slaughter and better weight gain performance than pigs that were vaccinated
once.14 Vaccines that contain the main serotypes H1N1 and human
H3N2 have been shown to confer clinical protection against SIV.2,15-17
The objective of this study was to evaluate the impact of vaccination
against pseudorabies and swine influenza with intradermally administered
vaccines under field conditions on growth parameters and on microbiologic
and pathological findings.
Materials and methods
Pretrial period
A serological survey was performed in six industrial pig units
with a total of 9700 sows. Blood samples were collected from 14 growing
pigs (total of 84 pigs) at 90 and 110 days of age. Serological analysis
was performed by serum neutralization (SN) test to detect antibodies against
PRV and by hemagglutination inhibition (HI) test to detect antibodies against
SIV. On the basis of the laboratory results, we selected the herd that had
the highest antibody titers against PRV and SIV to serve as the study herd
in this trial.
Trial herd
We performed this trial in 1992 in a modern, 2500-sow farrow-to-finish
pig unit that produces 48,000 finishing pigs per year. This unit has a fully
automated feed mill and a private slaughterhouse. The farm is located in
the most densely pig-populated area in Greece, where PRV is endemic. Swine
influence virus infection had also been diagnosed in the herd within the
3 years previous to the trial.
Herd health status
A routine vaccination program against PRV with inactivated vaccine (breeding
animals) and attenuated vaccine (finishing pigs) had been carried out in
the study herd for the 3 years previous to the start of this trial. Vaccination
against SIV with inactivated vaccines containing both SIV serotypes (H1N1
and H3N2) had also been performed since the first outbreak of the disease,
also 3 years previous to the start of the trial. Furthermore, the manager
of this herd was routinely vaccinating boars, breeding sows, and replacement
stock against the following diseases:
- porcine parvovirus,
- colibacillosis,
- swine erysipelas,
- Clostridium perfringens infection (types A and C),
- leptospirosis, and
- atrophic rhinitis (AR).
During the experimental period, clinical and laboratory tests failed
to find evidence of PRRSV infection. Until the end of 1992, Greece was free
of PRRSV (i.e., no cases had been reported and breeding stock imports had
been intentionally restricted during the onset of the disease in other European
countries).
Antibacterials in feed were administered to:
- the breeding herd (700 ppm chlortetracycline for 8 consecutive days
3 times per year);
- the growing herd (100 ppm tylosin for 8 days); and
- the finishing herd (400 ppm oxytetracycline plus 200 ppm penicillin-V
and 100 ppm of monensin sodium for 10 consecutive days).
Also, animals in this herd were routinely treated for parasites, both
internal (275 mg per kg bodyweight piperazine citrate as 1-day medication
at the beginning of the growing and finishing stages) and external (animals,
pens, and surroundings sprayed with 0.05% phoxim solution [Sebacil(R),
Bayer] once per month).
Trial animals and treatments
Three hundred 11-week-old pigs were selected, ear-tagged, and placed
in 15 identical pens with 18-22 animals per pen.
Five different trial groups were allocated in the above pens, representing
the following treatment groups (3 pens per treatment group):
- "Controls": not vaccinated against either PRV or SIV,
- "Single PRV": vaccinated against PRV at 100 days of age,
- "Double SIV": vaccinated against SIV at 100 and 121 days
of age,
- "Single PRV and Double SIV": vaccinated against PRV at 100
days of age and against SIV at 100 and 121 days of age, and
- "Double PRV and Double SIV": vaccinated against PRV and SIV
at 100 and 121 days of age
for a total of 60 pigs per treatment group.
Each block of five pens was one experimental block where the above five
treatments were randomly assigned. Male and female pigs were evenly represented
in each treatment group, and the average weight was not significantly different
(P > .05) among treatments at the beginning of the trial.
Treatment groups were placed in adjacent pens of the same building. Feeding
conditions were the same for all trial animals during the study. The offered
feed was a balanced grower diet (up to 50 kg liveweight with 13.54 mJ per
kg digestible energy, 18.76% crude protein, 1.22% lysine, 0.44% methionine,
and 60 ppm salinomycin as performance enhancer) and finishing diet (50 kg
liveweight to slaughter age with 13.42 mJ per kg digestible energy, 16.57%
crude protein, 1.00% lysine, 0.35% methionine, and 30 ppm salinomycin as
performance enhancer), delivered by hand during the study.
An attenuated vaccine against PRV (Alfort-26 strain, Dergeskalone(R),
Rhone Merieux, France) and an inactivated vaccine against SIV that contained
H1N1 and H3N2 serotypes (Derflu(R), Rhone Merieux) were used
to vaccinate the study pigs. Both PRV and SIV vaccines were intradermally
administered using a high-pressure needleless device (Pigjet(R),
Rhone Merieux).
Serological examinations
From nine pigs per treatment group (n = 45), we collected blood samples
at 80, 100, 120, 140 days of age, and at slaughter (180 days of age). Serum
samples were analyzed to detect antibodies against PRV (using the serum
neutralization [SN] test) and the serotypes H1N1 and H3N2 of SIV (hemagglutination
inhibition [HI] test). Titers > 1:2 for PRV, > 1:16 for the
H1N1 serotype, and > 1:32 for the H3N2 serotype were considered as positives
for control group pigs.
Growth performance data
For all treatments, we calculated average daily gain (ADG) for the following
experimental subperiods:
- days 80-119 of age,
- days 120-139 of age,
- days 140-180 of age, and
- days 80-180 (overall period).
Feed:gain ratio (F:G) and average total feed consumption (ATFC) values
were calculated for the overall period on a per-pen basis.
Health monitoring
For each trial animal, we assessed general health status, noting respiratory
problems (coughing, sneezing, abdominal breathing, etc.) for a period of
12 consecutive hours on a daily basis. Medications via feed or injectables
were also recorded for the whole experimental period. To all animals exhibiting
respiratory signs, we administered 10 mg per kg body weight of injectable
oxytetracycline daily for 3 consecutive days. Animals removed from the study
were examined according to appropriate clinical and laboratory procedures
to determine the cause of removal.
Snout morphology
Snouts of all trial animals were examined at slaughter for morphological
lesions due to AR by coronal sectioning at the level of the second premolar.
Morphological lesions were scored according to the Weybridge snout grading
system (i.e., snout scores range from 0 (unaffected) to 5 (totally devoid
of turbinate bones).18
Statistical analysis
Data were subjected to one-way analysis of variance, with the pen/replicate
as the experimental unit, using the general linear models (GLM) procedure
of the Statistical Analysis System (SAS).19 The analysis of variance
(ANOVA) model included terms for the treatment effect on least squares means
and error. Duncan's multiple range test was used as the comparison test
to distinguish the statistical difference among the five treatment groups.
The level of significance was set at a = .05.
Lung lesions
Lungs of all trial animals were examined at the slaughterhouse. For the
purposes of this trial, we attempted to discriminate between chronic lesions
typical of enzootic pneumonia (i.e., cranioventral consolidation) and lesions
resulting from acute infection.
We scored lesions we attributed to chronic enzootic pneumonia using the
methods of Walton.17 Briefly, for each lobe of the lung we assigned
a value corresponding to the approximate proportion of the total lung damage
that lobe represents. Degree of consolidation in each of these lobes was
assessed, and each was given a score of either 0-5 (for apical and intermediate
lobes) or 0-10 (for cardiac and diaphragmatic lobes). The maximum possible
total score was 55.18 A mean value for each treatment was calculated
for comparison among groups.
Lesions we attributed to viral infection were scored on a scale of 0
to 4, according to the following criteria:
- 0 = absence of lesions,
- 1 = small foci with congestion,
- 2 = extended foci with red and grey hepatization,
- 3 = extended foci with red and grey hepatization and presence of adhesions,
and
- 4 = greatly enlarged lung tissue and "fish flesh" consistency.
A Chi-square analysis was performed on the association between treatment
and the proportions of pigs in each lesion category for lesions attributed
to acute pneumonia.
Bacteriological examinations
We randomly collected two lung samples per pen at the slaughterhouse
(six for each trial group), which we cultured to detect Pasteurella multocida,
Actinobacillus pleuropneumoniae, Streptococcus suis, Staphylococcus
spp, and Proteus spp.
Results
Serology
Pigs in both the control group and in the "double SIV" group
seroconverted to PRV during the trial period (Figure 1). Antibodies against both serotypes of SIV
were consistently present in the control pigs during the trial (Figure 2).
Growth performance data
All three growth parameters measured (ADG, F:G, ATFC) were significantly
improved in pigs in all vaccinated treatment groups compared to pigs in
the control group (Figure 3).
Pigs in the "double PRV and double SIV" treatment group had
significantly higher ADG compared to pigs in all other groups, except during
the first trial subperiod, when there was no significant difference between
ADG in the "single PRV and double SIV" treatment group and the
"double PRV and double SIV" treatment group.
All vaccinated groups had significantly lower F:G values than
the control group pigs. Pigs in the "double PRV and double SIV"
group had significantly better F:G and ATFC (P < .05) compared
to the other vaccinated trial groups.
Health monitoring
Mortality during the trial was 0% for all experimental groups. However,
four trial animals (two from "single PRV" group, one from the
"double SIV" group, and one from the "single PRV and double
SIV" group) were removed and sent to the slaughterhouse before the
end of the experimental period due to severe streptococcal arthritis characterized
by swelling of the tarsal joints, lameness, and unwillingness to move.
Respiratory distress with coughing and sneezing, varying in intensity,
appeared in:
- 12 of 60 pigs in the control group,
- 10 of 60 pigs in the "single PRV" group,
- 10 of 60 pigs in the "double SIV" group,
- six of 60 pigs in "single PRV and double SIV" group, and
- three of 60 pigs in "double PRV and double SIV" group.
The duration of the symptoms varied from 5-8 days.
Snout morphology
No significant differences in snout morphology were found among treatment
groups.
Lung lesions
There was no significant difference in chronic lung lesion scores among
all treatment groups.
For acute lung lesions, the distribution of pigs among lesion categories
varied significantly among treatments (P < .001, Chi square =
153.6) (Figure 4). There was
a significantly higher proportion (75%) of pigs in the "double SIV
and double PRV" treatment group that had lesion scores of 0 compared
with all other groups.
Bacteriology
Pasteurella multocida was isolated from four of six lung samples
of the control group and from three of six samples in the "single PRV"
group (Figure 5). Nonhemolytic
Staphylococcus spp were isolated from three of six samples of the
control group and from two of six in the "single PRV" and the
"double SIV" groups. Proteus spp were isolated from two
of six lung samples of the "double SIV" group. No pathogens were
isolated from the samples of the "single PRV and double SIV" and
the "double PRV and double SIV" groups.
Discussion
Pseudorabies virus and SIV antibodies in the control group pigs indicated
the presence of these viruses in the study herd during the trial period.
The relatively low HI titers observed in the groups of animals vaccinated
against SIV is remarkable and, in association with the results obtained
for growth performance, may indicate that intradermal vaccination provides
sufficient protection for finishing pigs even when the level of antibodies
is lower than that provided by intramuscular vaccination.13
Our failure to detect pathogenic bacteria in the lung samples of pigs
in the "double PRV and double SIV" group suggest that double vaccinating
against PRV and SIV may eliminate the presence of pathogens in the lungs
as secondary complicating factors.
The similar ADG of pigs from 80-120 days of age in the "single PRV
and double SIV" and the "double PRV and double SIV" groups
is the only exception to our observation that the double-vaccinated pigs
had superior growth performance compared with pigs in all other treatment
groups for all parameters measured. The superiority of double-vaccinated
animals against both PRV and SIV in growth performance may indicate that
double vaccination against PRV and SIV can protect pigs from the clinical
manifestation of a mixed infection with the simultaneous presence of PRV
and SIV.
The increased lung lesion scores in control pigs, in association with
the bacteriologic findings, suggest that vaccination against PRV and SIV
may reduce secondary bacterial complications.
Our administration of oxytetracycline to animals found coughing and sneezing
during the study probably confounded the lung lesion findings, helping many
of the lesions to resolve before slaughter. It seems likely that the lung
lesions would have been more severe in those animals that received antibiotics
than the slaughter lung lesion scores they actually received.
The complete absence of tissue irritation at the site of injection and
the reduced labor associated with intradermal injection make this the preferred
vaccination strategy for PRV and SIV vaccines.
Since this trial was conducted, this herd has become infected with PRRSV.
The best vaccination protocol must be reconsidered in light of the availability
of live attenuated vaccines against PRRSV.20
Implications
- Double vaccination of finishing pigs against PRV and SIV can improve
growth performance and eliminate the negative effects of secondary pathogens.
- Double vaccination appears to be a valuable measure and is recommended
for preventing viral respiratory diseases of growing/finishing pigs.
- Intradermal vaccination with a needleless device appears to be an effective
means of administering vaccine.
References
1. Pensaert MB, Kluge JP. Pseudorabies Virus (Aujeszky's Disease). In:
Pensaert, MB (ed). Virus Infections of Porcines. Elsevier Publications.
1989:39-63.
2. Pensaert MB. Pathogenie comparee de la grippe et de la maladie d'
Aujeszky - Consequences pour la prophylaxie medicale. Proc Congres AFMVP.
10 Octobre 1989; Paris, France.
3. Kyriakis SC, Saoulidis K, Sarris K, Papatsas J, Kantas D. Swine influenza:
New information and present status in Greece. Bul Hell Vet Med Soc.
1992;43(2):89-94.
4. Kyriakis SC. Aetiology and control of the respiratory syndrome in
finishing pigs. Proc 6th Cong Hell Vet Med Soc. Athens, Greece;1993;48.
5. Papatsas J, Kyriakis SC, Saoulidis K, Sarris K, Paschaleri-Papadopoulou
E. The main viral respiratory diseases of growing/fattening pigs and their
present status in Greece. Bul Hell Vet Med Soc. 1994;45:195-202.
6. Papatsas J, Kyriakis SC, Papadopoulos O, Koubati - Artopiou M, Kritas
SK. Aujeszky's disease virus of pigs: Update review and proposals for its
control and eradication in Greece. Bul Hell Vet Med Soc. 1995; 46(1):19-29.
7. Iglesias G, Pijoan C, Molitor T. Interactions of pseudorabies virus
with swine alveolar macrophages: Effects of virus infection on cell functions.
J Leukocyte Biol. 1989;45:410-415.
8. Van Reeth K, Koyen A, Pensaert M. Clinical effects of dual infections
with porcine epidemic abortion and respiratory syndrome virus, porcine respiratory
coronavirus and swine influenza virus. Proc 13th IPVS Congress, Bangkok,
Thailand. 1994;51.
9. Kay RM, Done SH, Paton DJ. Effect of sequential porcine reproductive
and respiratory syndrome and swine influenza on the growth performance of
finishing pigs. Vet Rec. 1994;135:199-204.
10. Pensaert MB, Maes L. Parenteral and intranasal vaccination of finishing
pigs against pseudorabies virus (pseudorabies). Zbl Vet Med., 1984;B.31:682-689.
11. Meliota F, Prosperi S, Ostanello F, Callegari V. Efficacy of an inactivated
gI deleted vaccine against pseudorabies virus. Proc 12th IPVS Congress,
The Hague, Netherlands. 1992;72.
12. Visser N, Verbuggen W, Markx D, Lµtticken D. Elimination of
pseudorabies from a highly infected herd using vaccination with gI-vaccine
and economical replacement of sows. Proc 12th IPVS Congress, The
Hague, Netherlands. 1992;80.
13. Vannier P, Cariolet R. Vaccination of pigs against pseudorabies virus
by the intadermal route using live attenuated and inactivated virus vaccines.
Vet Microbiol. 1991;26:11-23.
14. Stegeman JA, van Nes A, de Jong MCM, Bolder FW, Elbers ARW. Efficacy
of vaccination against pseudorabies virus: Comparison of single versus double
vaccination. Proc 13th IPVS Congress, Bangkok, Thailand. 1994;46.
15. Haesebrouck F, Pensaert M, Wyffels R. Vaccination of swine against
H3N2 influenza field isolates using the human Philippines-strain. Vet
Quarterly. 1987; 9:9-14.
16. Vandeputte J. Vaccination against swine influenza of fattening pigs.
Proc Swine Influenza Seminar, 27 February 1987. Kortrijk, Belgium.
8-13.
17. Schirvel C, Brun A, Lacoste F, Noe T. Intradermal vaccination of
pigs. Proc 6th Cong Hell Vet Med Soc. Athens, Greece.1993; 58.
18. Walton JR. In: Walton, JR (ed). A Handbook of Pig Diseases.
Liverpool, England: Liverpool University Press; 1987:126-129.
19. SAS User's Guide. version 6, 4th ed. Cary, North Carolina:
SAS Institute Inc., 1994:891-896.
20. Gorcyca D, Schlesinger K, Chladek D, Behan W. RespPRRS(R):
A new tool for the prevention and control of PRRS in pigs. Proc AASP
Annual Meeting, Omaha, Nebraska. 1995;1-11.
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