The invention relates to infectious bronchitis virus (IBV) vaccines
for poultry and more in particular to improved infectious bronchitis vaccines which
are extremely safe and effective for vaccinating day-old chickens.
The use of live infectious bronchitis vaccines for poultry has been
known for a great many years already. Infectious bronchitis is an important affection
of the bronchial tubes in poultry caused by a corona virus. The affection causes
great economic losses in poultry keeping, since infectious bronchitis still causes
enormous mortality especially in young poultry. Besides mortality and more or
less strong respiratory phenomena, damage to the hen's egg laying system and hence
reduction in production occurs in laying hens as a result of an IB infection. Moreover,
infections with IBV may stimulate virus and bacterial infections and thus result
in serious economic losses, in particular in the broiler sector.
Vaccines on the basis of live virus have initially been used to control
infectious bronchitis. For example, live IBV vaccines based on a modified H-strain
have been used for a long time already. The original H-strain was isolated by
Bijlenga, Hoekstra and Rispens (Tijdschrift voor Diergeneeskunde, 81, (1956),
p. 43, and 85 (1960), p. 279, and 85 (1960), p. 398) and was passed
a few times over hatched hen's eggs. Eventually, strains (H120 and H52) were obtained
which proved to be less virulent for the hen than the virus isolated from the field.
The modified strain H120 is used for vaccinating day-old chickens, while strain
H52 is used especially in animals at an age of approximately 8 weeks.
Although the use of vaccines based on the strains H120 and H52 is
fairly safe and effective, it has been found that the two live vaccines in certain
circumstances are not capable of preventing outbreaks of infectious bronchitis.
These outbreaks may be ascribed to the occurrence of modified strains. The occurrence
of modified strains called for the search for more effective vaccines based on
infectious bronchitis virus strains of different serotypes.
This investigation has resulted in the vaccines which are described
in European Patent Specification 0,030,063 and European Patent Application 0,086,025
and which are both based on infectious bronchitis virus (IBV) modified strains.
It has been found that an effective protection against infectious bronchitis is
obtained by using vaccines (live and inactivated ones) based on the so-called modified
Investigations have demonstrated that laying hens can be effectively
protected by a combined use of both live and inactivated vaccines.
Broilers have so far been vaccinated against infectious bronchitis
on the first day of life with a vaccine based on strain H120. However, due to the
occurence of the modified strains, said vaccination is no longer effective and
hence derivatives of the occurring modified strains ought to be found which can
be administered on day 1. Investigation in broilers carried out by the Public Health
Department for Poultry in Doorn has proved that besides the serotype Massachusetts
(H120, H52), mainly viruses of the serotype D207 are found. Consequently, an effective
vaccine for the protection of broilers against infectious bronchitis will have
to consist of H120 and a virus related to strain D207.
Although it is stated in the above-mentioned European Patent Specification
and the European Patent Application that the vaccines described therein can also
be used in young animals, experiments have proved that live vaccines based on
the IBV-modified strains known from these documents are too virulent for the vaccination
of day-old broilers. The strain D274 mentioned in the European Patent Application
(and registered in Central Veterinary Laboratory, New Haw, Weybridge, England VLO
10110/AVI/3; and Institut Pasteur No. I-216, respectively) proved to be too virulent
for vaccination of day-old chickens after 52 and even after 122 egg passages.
It has surprisingly been found that a safe and effective live vaccine
for the protection of day-old chickens against a modified strain of the infectious
bronchitis is obtained when the strain registered in the Institut Pasteur under
No. I-473 is used as a virus strain.
The virus strain used is derived from a strain isolated from the
field and will hereinafter be referred to as virus strain 84-3.
A generally known problem in administering vaccines based on more
than one live virus strain is the fact that the combined viruses become
less immunogenic due to a mutual interaction (see Am.J.Vet.Res. 36, (1965),
p. 4, 524 and 525; and Avian Diseases 12, (1968), p. 577).
It is extraordinarily surprising that the problem of interference
does not present itself when the new strain 84-3 according to the invention is
combined with H120 and other live poultry viruses.
Experiment 1: Safety of the strain 84-3.
Three groups of 20 day-old SPF chickens each were vaccinated on day
1 with a dose of 104.3 EID&sub5;&sub0; (egg infective dose) per chicken
by means of dripping in the eye (group 1 with the known strain H120; group 2 with
the strain D274 after it had been subjected to 52 egg passages; group 3 with the
strain 84-3 according to the invention). A fourth group of 20 animals served as
the control group.
On day 5, 10 chickens of each group were killed for tissue investigation
of the trachea (see R.W. Winterfield et al, Avian Dis. 16 (1972),
pp. 260-269). The remaining 10 chickens of each group were also killed on
day 5 for investigation of ciliary activity (J.H. Darbyshire, Avian Pathol.
9 (1980), pp. 179-184). The results of this experiment are recorded
in Table A:
It appears from the above that, starting from a dose of 104.3
EID&sub5;&sub0; per animal, i.e. more than a 10-fold excess, based on ciliary activity
the strain 84-3 is less virulent than the strain D274 after 52 eggs passages and
the strain H120. However, based on trachea lesions, the strain 84-3 is slightly
more virulent than the strain H120. An explanation for this difference could be
that the strain 84-3 causes more lesions without destroying the ciliary activity,
which then would mean that the strains 84-3 and H120 have slightly different pathology.
In general, the presence of ciliary activity is considered as a reliable
indication for protection against a challenge with virulent virus.
Since 9 out of 10 chickens vaccinated with strain 84-3 showed ciliary
activity, it could be concluded that the strain is safe for day-old chickens, the
more so when it is considered that in this experiment more than a 10-fold excess
has been administered to extremely sensitive animals, namely SPF-chickens without
Experiment 2: Efficacy of the vaccination with strain
Two groups of 30 day-old chickens each were housed separately.
On day 1, the test group was vaccinated by eye drop with a dose of
103.3 EID&sub5;&sub0; per animal (of the strain 84-3 according to the
invention). Two weeks after vaccination, 5 chickens from each group were killed
and examined for ciliary activity. This was repeated 4 weeks after vaccination.
Both groups demonstrated 100% ciliary activity.
Four weeks after vaccination, 12 animals from each group were challenged
with 103.0-3.5 EID&sub5;&sub0; per chicken with the virulent strain
D207. The challenge virus was administered partly intranasally and partly intraocularly.
Six days after the animals were examined for ciliary activity and trachea lesions.
The results are recorded in Table B hereinafter:
As is demonstrated by the results obtained, more than 83% of the
animals from the test group are protected, whereas only 17% of the non-vaccinated
control group are protected. This result is confirmed by the score of the trachea
lesion examination in both groups.
Experiment 3: Combined administration of strain 84-3 and
strain H120 to day-old chickens.
Two groups of 17 day-old SPF chickens each were vaccinated on day
1 with a dose of 103.0 EID&sub5;&sub0; of strain 84-3 + 103.5
EID&sub5;&sub0; of strain H120 per chicken. Each test group was accompanied by
a control group of 8 chickens. Four weeks after the vaccination the animals of
one test group and one control group were challenged with 103.5 EID&sub5;&sub0;
of the virulent strain D207. The other test group and control group were challenged
at the same point of time with 103.5 EID&sub5;&sub0; of the strain Voet
(i.e. the virulent strain). Both virulent strains were administered both intranasally
and intraocularly. Before administration of the challenge virus the vaccinated
and non-vaccinated chickens were joined together. Six days after administration
of the challenge virus the animals were killed and examined for ciliary activity
and trachea lesions. The results are recorded in Table C:
From this it appears that the ciliary activity in the chickens of
both groups was intact, which indicates 100% protection. This is confirmed by the
low lesion score in the two test groups (0.51 and 0) with respect to the control
groups (1.63 and 2.63).
Vaccination of day-old SPF chickens with a combination of the strains
84-3 and H120 provides a good protection against a challenge with virus of the
strain D207 or the strain Voet, which indicates that both viruses do not adversely
influence each other during the vaccination. This may once more appear from experiment
Experiment 4: Field experiment on a small scale.
Three groups of 375 (group 1), 400 (group 2) and 50 (group 3) day-old
broilers, and one group of 40 day-old SPF-chickens (group 4) were used.
Group 1 was vaccinated on day 0 with a dose of 104.5
of strain 84-3 and 103.3 EID&sub5;&sub0; of strain H120 per animal.
On day 0, a dose of 103.3 EID&sub5;&sub0; of strain H120 per animal
was administered to group 2 (spray method). Groups 3 and 4 served as non-vaccinated
On day 10, 20 animals of the groups 1 and 2 were killed for trachea
The breathing of the animals was checked from day 0 to day 21.
On day 28, 25 animals of the groups 1, 2 and 3 and 10 animals of
group 4 were challenged intraocularly with a dose of 103.8 EID&sub5;&sub0;
of the virulent strain Voet.
The same number of animals of each group were challenged on day 28
with a dose of 103.5 EID&sub5;&sub0; of the virulent strain D274 (intranasally
Six days after administration of the challenge virus, the animals
were killed and tested for trachea lesions and ciliary activity.
The challenge of day 28 was repeated with identical groups on day
42. These animals were also killed 6 days later and examined.
The remaining animals of groups 1 and 2 were weighed on day 60 so
as to determine the average weight on the day of slaughter.
The results of the trachea lesion test after 10, 28 + 6 and 42 +
6 days are recorded in table D hereinafter:
The results of the cilia stopping test (CST) are recorded in Table
E, in which the numbers indicate the percentage of protection.
On the day of slaughter, the animals of group 1 had an average weight
of 2350 g (n = 221), those of group 2 had an average weight of 2310 g (n = 233).
From the above results it follows that the combination of strain
84-3 according to the invention and H120 is safe for day-old broilers, because
1) no increase of respiratory symptoms occurs after administration of the combination
2) there is no higher trachea lesion score after vaccination;
3) there is no significant difference in slaughter weight.
The protection after challenge with virulent virus of the strain
D274 is much better for group 1 (92 and 100% after 4 and 6 weeks, respectively)
than for group 2 (64 and 83%). Non-vaccinated animals are already fully affected
at an age of 4 weeks.
These results were confirmed entirely by the trachea lesion score.
Group 1: 0.31 and 0.04. Group 2: 0.60 and 0.57 at an age of 4 and 6 weeks, respectively.
Group 3: 1.83 at an age of 4 weeks.
The protection against challenge with the strain Voet which is homologous
for H120 is comparable in the groups 1 and 2.
Group 1: 100% after 4 and 6 weeks;
Group 2: 91% (4 weeks), 100% (6 weeks).
This is also confirmed by the trachea lesion score:
Group 1: 0.17 and 0.00 after 4 and 6 weeks, respectively;
Group 2: 0.24 and 0.08 after 4 and 6 weeks, respectively;
Group 3: 1.59 after 4 weeks.
So the combined vaccine with strain 84-3 and strain H120 gives an
excellent protection against infection with both the strain D274 and against the
Massachusetts strain during the whole fattening period.
On the basis of the above it will be clear that the present invention
relates to new live IBV vaccines which are derived at least from the new IBV strain
84-3 and to the use thereof for vaccinating day-old chickens.
Vaccines are preferably derived from the H120 virus strain and from
IBV of the strain 84-3. The new virus strain 84-3 can be processed to a live vaccine
according to standard methods. In these methods, the virus is mixed with stabilisers
conventionally used for this purpose and then freeze-dried. For administration
purposes, the freeze-dried vaccine should be dissolved in a liquid solvent suitable
for that purpose. The vaccine may be administered by means of the so-called eye
drop, nose drop, drinking-water or spray methods for live vaccines. Vaccination
by means of the new live vaccines according to the invention is preferably carried
out in day-old poultry.
It will be obvious that combined live vaccines derived from the new
IBV strain 84-3, strain H120 and from one or more other poultry virus types, for
example, Newcastle disease virus, also form part of the present invention.
1. A live vaccine against infectious bronchitis, characterized in that it comprises
a virus of the strain 84-3 which is registered in the Institut Pasteur in Paris
under No. I-473.
2. A vaccine as claimed in Claim 1, characterized in that it comprises a quantity
of virus of the strain 84-3 of at least 102.5 EID&sub5;&sub0; per dose.
3. A vaccine as claimed in Claim 1 or 2, characterized in that it also comprises
one or more viruses of other IBV-strains.
4. A vaccine as claimed in Claim 3, characterized in that, besides virus of
the strain 84-3, it also comprises virus of the strain H120.
5. A vaccine as claimed in Claim 4, characterized in that the overall quantity
of IBV is at least 106.0
EID&sub5;&sub0; per dose.
6. A vaccine as claimed in Claims 1-5, characterized in that it also comprises
one or more other poultry viruses.
7. A vaccine as claimed in Claim 6, characterized in that, besides virus of
one or more IBV strains, it also comprises Newcastle Disease Virus.
8. A method of preventing infectious bronchitis in poultry, characterized in
that day-old chickens are vaccinated with a vaccine as claimed in one or more of
the claims 1-7.
9. A virus strain IBV 84-3 registered in the Institut Pasteur in Paris under