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The Feather Follicle Method of Vaccinating with Fowl Laryngotracheitis Vaccine
POULTRY S C I E N C E November, 1947, Vol. XXVI, N o . 6
P. C. MOLGAED AND J. W. CAVETT Research Division, Dr. Salsbury's Laboratories, Charles City, Iowa (Received for publication February 19,1947)
T
HE accepted method for vaccinating poultry against fowl laryngotracheitis has been to apply the vaccine in the vent of the chicken. The belief has been general and widespread that Fowl Laryngotracheitis Vaccine could be used successfully only in this way and that it could not be applied advantageously into the feather follicles as is done with pox vaccine. During the fall of 1941 one of us (P.C.M.), while conducting experiments with Fowl Laryngotracheitis Vaccine, brushed the vaccine into the feather follicles on the legs of a few chickens as one, would do if vaccinating with pox vaccine. It was noted that the follicles began to swell on the second day, that the reaction reached its peak on about the fifth day, and that the swelling receded completely by the seventh or eighth day. The reaction or "take," was similar to that which appears after applying Pigeon Pox Vaccine to the follicles. However, the time elapsing during the development and recession of the take corresponded to the length of time required for a reaction to appear and
recede when laryngotracheitis virus is applied in the vent. After this observation had been made a few times the question, naturally, was raised, Would follicle vaccination produce immunity in chickens similar to that established when the vaccine is applied in the vent? To determine this, further experiments were set up with the assistance of Dr. W. G. Keehn, at that time bacteriologist at Dr. Salsbury's Laboratories. EXPERIMENTAL TESTS
On January 5, 1942, two chickens were each vaccinated by applying Laryngotracheitis Vaccine in the vent and, also, the vaccine was brushed into ten feather follicles on the right thigh of each chicken. The resulting reactions are shown in Table 1. On January 19, 1942, six New Hampshire chickens, 14 weeks of age, were vaccinated with a commercial vaccine in ten feather follicles on the leg. Six others were vaccinated in the vent. The results shown in Table 2 were obtained. On January 22, 1942, nine chickens,
563
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
T h e Feather Follicle Method of Vaccinating with Fowl.Laryngotracheal s Vaccine
564
P . C. MOLGARD AND J . W . CAVETT TABLE 1*
Chicken 1-7 no. 101 102
+ +
101 102
— —
!
1-8
1-9
1-10
Follicle reactions 2+ 3 + 2 + 2 + 3+ + Vent reactions 2+ 3 + 2+ 3++ +
1-11
1-12
1+ —
— —
4+ Receding 4 + Receding
five weeks of age (identified by band numbers 832, 847, 846, 818, 815, 857, 799, 848, 1008), were vaccinated in the feather follicles. On the fifth day these chickens showed 3 + reactions. Four other chickens of the same batch (identified by band numbers 814, 840, 842, 849) were used as controls. Sterile distilled water applied to the feather follicles of these chickens, produced no reaction. An experiment was begun January 26, 1942, with four Barred Rocks, 10 months of age (band numbers 3073, 5571, 3030, 3070), and five New Hampshires, 15 weeks of age (band numbers 668, 669,
TABLE 2
Chicken no.
1-21
1-22
1-23
1 2 3 4 5 6
+ + + + + +
242+ 2+ 2+ 2+ 2+
3+ 3+ 3+ 3+ 3+ 3+
7 8 9 10 11 12
— — — — — —
— — — — — —
— 2+
+ + 2+ 2+
1-24
1-25
Follicle-vaccinated 3+ 4+ 3+ 4+ 3+ 4+ 3+ 4+ 3+ 4+ 3+ 4+ Vent-vaccinated
2+
3+ 2+ 3+ 2+ 3+
+
3+ + 3+ + 3+
1-26
1-27
2+ 2+ 2+ 2+ 2+ 2+
+ + + + + +
+ + +
1-28
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
Key to Reactions: — = Normal + = Mild reaction (unsatisfactory) 2 + = Fair reaction (satisfactory) 3 + = Excellent reaction 4 + = Extra strong reaction
670, 671, and 672). These chickens previously had been vaccinated with Fowl Laryngotracheitis Vaccine by the vent method and had shown satisfactory takes. These chickens now were each vaccinated with Laryngotracheitis Vaccine in the feather follicles of the right thigh. At the same time sterile distilled water was applied to the feather follicles on the left thigh of each chicken. No reactions were produced by any of these inoculations, indicating that the takes observed in follicle-vaccinated birds in previous tests actually were due to the action of laryngotracheitis virus. Further tests to observe and compare the degree of immunity obtained from follicle and vent methods of vaccination were started on February 2, 1942, when the six chickens which had been vaccinated by the follicle method on January 19, and the nine vaccinated January 22 were each inoculated intratracheally with laryngotracheitis virus to determine whether the follicle inoculations had caused them to become immune to laryngotracheitis virus. As a control group, the six chickens vaccinated January 19 by the vent method, five chickens vaccinated December 12 by the vent method which
VACCINATION METHOD FOR LARYNGOTRACHEITIS
On February 25, 1942, thirteen 5-weekold chickens (band numbers 1586 to 1598 inclusive) were vaccinated in the feather follicles with a commercial vaccine. At the same time 11 other thickens (band numbers 1601 to 1611 inclusive) were vaccinated with a strain of laryngotracheitis virus isolated from a flock in Minnesota. Reactions were identical for all chickens,
indicating that another strain would produce similar results. On May 6, 1942, eight chickens picked at random from this group were tested for immunity by intratracheal inoculation with laryngotracheitis virus. None of them developed any symptoms of the disease. At the same time four susceptible chickens, inoculated with the same virus, developed the disease and two died. These results indicate that immunity had been established in the follicle-vaccinated chickens. Since it was evident from experiments conducted up to this time that feather follicle vaccinations produced as good results as the vent vaccinations, the question naturally was raised as to whether immunity could be produced by introducing Laryngotracheitis Vaccine into the skin of chickens by the use of stab-type vaccinators used for pox vaccination. On March 13,1942, three groups of chickens, six in each group, were vaccinated in the wing webs. Three different types of pox vaccinators were used for this experiment. A fourth group of seven chickens was vaccinated by the follicle method. The wing web reactions were negative or, mild while all follicle reactions were strong. To determine whether the wing web-vaccinated chickens had developed immunity to laryngotracheitis virus, 12 of these wing-vaccinated chickens were inoculated intratracheally with laryngotracheitis virus on May 6. At the same time five of the follicle-vaccinated chickens were inoculated with the same virus. The result was that five of the wingweb-vaccinated chickens developed the disease and three died. None of the feather follicle-vaccinated chickens developed the disease. From the results of this experiment, wing web vaccination does not appear to be a satisfactory method. An entire hatch of New Hampshire chicks, hatched on April 23, 1942, was
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
when examined all showed satisfactory takes, and five New Hampshire laryngotracheitis-susceptible chickens were also inoculated intratracheally with the same virus. Four of the laryngotracheitissusceptible chickens developed laryngotracheitis and two of them died. One did not develop the disease. No symptoms of laryngotracheitis were observed in any of the fifteen follicle-vaccinated chickens or the eleven vent-vaccinated chickens. These results indicate that immunity had been established in all vaccinated chickens. On February 21, 1942, tests were started on three groups of chickens. Group 1, consisting of nine 3-week-old chicks, was vaccinated by the follicle method and developed only + reactions. On May 6, seven of these chickens were inoculated intratracheally with laryngotracheitis virus, one of them developing the disease. Group 2, consisting of six 6-week-old chickens, was follicle vaccinated and produced 3 + reactions. Four of these inoculated intratracheally on May 6 did not develop laryngotracheitis, indicating that immunity had been established by the follicle vaccination. Group 3, consisting of five birds which had recovered from the disease and six chickens which previously had shown satisfactory vent vaccinations, developed no takes when inoculated in the feather follicle. This again indicated that laryngotracheitis-immune chickens would not develop follicle reactions when inoculated with laryngotracheitis virus.
565
566
P. C. MOLGARD AND J. W. CAVETT
On June 17, 1942, 120 New Hampshire chickens hatched May 14 (band numbers 2750 to 2869) were vaccinated with Laryngotracheitis Vaccine in the feather follicles of the right thigh. At the same time these same chickens were also vaccinated with Fowl Pox Vaccine, 60 in the feather follicles of the left thigh and 60 in the wing web by the stab method. No untoward results followed the use of both pox and laryngotracheitis vaccine on these chickens at the same time. The following winter chickens picked at random from this group were periodically inoculated intratracheally with laryngotracheitis virus, which did not cause them to develop the disease.
DISCUSSION OF EXPERIMENTAL RESULTS
After finding in the laboratory that laryngotracheitis virus, when placed in feather follicles of the chicken, will produce immunity to laryngotracheitis, these questions arose: 1. Could this method of vaccinating be used successfully in the field? 2. What advantages, if any, would it have over the vent method? One of the chief objections to the vent method is the "watery vent" which is often encountered if the flock has not had proper care before vaccinating time. This watery condition may have a tendency to dilute or wash out the virus before it becomes established. This may be the reason why some vent-vaccinated chickens fail to develop reactions and remain susceptible to the disease. Follicle vaccinations produce strong takes on nearly every chicken as the virus, when it is once placed in the feather follicle, stands little chance of being expelled. When a laryngotracheitis reaction in the vent reaches its peak, an excessive amount of mucus is expelled. Undoubtedly, this causes the release of much laryngotracheitis virus. When the follicle method of vaccination is used, scarcely any secretion or exudate is thrown off. As a result, the virus is much less likely to cause heavy contamination of the premises. It appears that this should be a distinct advantage in favor of follicle vaccination. FARM FLOCK VACCINATION
On May 23, 1942, a farm flock of 2,025 White Leghorn chickens, 11 weeks of age, was vaccinated with Laryngotracheitis Vaccine, 1,992 by the vent method and 33 by the follicle method. On the fifth day all chickens were examined for takes. All follicle-vaccinated chickens showed good
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
held for use in further experimentation. On May 7, at two weeks of age, 39 of these chicks were vaccinated, 20 by the vent method and 19 by the follicle method. Two of the vent vaccinations produced unsatisfactory takes, while all of the follicle vaccinations showed satisfactory reactions. On May 28, at five weeks of age, another group of 20 chickens was vaccinated by the vent method and 20 by the follicle method. All reactions were satisfactory. On May 29, at five weeks of age, 13 chickens were vaccinated in the wing webs by the stab method. The stab method again produced only mild reactions. On June 15, at seven weeks of age, 20 chickens were vaccinated in the vent and 20 in the follicles. Three of the ventvaccinated chickens developed only + reactions whereas all follicle reactions were satisfactory. At various times during the following year, follicle-vaccinated chickens were removed from this flock and inoculated intratracheally with laryngotracheitis virus. None of these chickens developed laryngotracheitis, whereas unvaccinated chickens which were inoculated with the same virus developed the disease.
VACCINATION METHOD FOR LARYNGOTRACHEITIS
During the past four seasons this method has been used successfully on a considerable number of flocks and no untoward results have been reported from the field. SUMMARY
1. It has been demonstrated that Fowl Laryngotracheitis Vaccine, when placed in the feather follicle of the chicken, will produce immunity to laryngotracheitis as it does when the vaccine is introduced into the vent or Bursa of Fabricius. 2. A follicle reaction expels very little exudate whereas a heavy take in the vent causes a relatively profuse exudation. 3. Follicle vaccinations give a higher
percentage of readable takes than are produced when chickens are vaccinated in the vent. Watery vents are not a problem when follicle method vaccination is used. 4. The results obtained in the field through vaccinating by this method have been very satisfactory. ADDENDUM
Since submitting this paper, a commercial Fowl Laryngotracheitis Vaccine which was being tested for other purposes was applied to the feather follicles of two chickens. A very questionable reaction developed. Since this strain of virus was being cultured on eggs, another feather follicle test was made using the material prepared in this Laboratory and also with another sample of the same commercial vaccine as prepared by the producer. Again, the takes which developed in the follicles from inoculation with both preparations were very questionable. Both vaccines produced excellent vent takes on other chickens from the same flock. The follicle vaccinated chickens were revaccinated four weeks later with a potent virus and no takes developed. Vaccines prepared by five other commercial concerns were purchased and tested for follicle reaction. One group of chickens was vaccinated by the vent method to determine if the virus was potent and to observe the take produced. Other chickens were also vaccinated by the follicle method. All five vaccines gave follicle reactions similar to those produced by the two strains we had used in our work. It has been suggested that this one strain of fowl laryngotracheitis virus is a mutant which, although it produces good vent reactions, does not produce very marked reaction in the follicle.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
reactions, but it was found that 3.4 percent of the vent-vaccinated chickens did not show a visible reaction. A flock of 3,161 White Leghorns, 14 weeks of age, belonging to the same poultry raiser, was vaccinated June 23, 1942, 2,108 by the vent method and 1,053 by the follicle method. On the fifth day examination revealed that 4.55 per cent of the vent-vaccinated chickens showed unsatisfactory takes. These chickens were revaccinated but it was impossible to observe the revaccinated chickens at the proper time because they had not been kept isolated. All of the 1,053 folliclevaccinated chickens developed satisfactory reactions from the first vaccination. The cockerels of this flock were sold at housing time, but the pullets were housed and held throughout the year. During this time observation revealed no distinguishable difference between the vent and follicle-vaccinated chickens. Since that time the owner of these flocks and the people associated with him have vaccinated between 20 and 30 thousand chickens each year and have used only the follicle method of vaccination.
567
P. C. MOLGAED AND J. W. CAVETT Research Division, Dr. Salsbury's Laboratories, Charles City, Iowa (Received for publication February 19,1947)
T
HE accepted method for vaccinating poultry against fowl laryngotracheitis has been to apply the vaccine in the vent of the chicken. The belief has been general and widespread that Fowl Laryngotracheitis Vaccine could be used successfully only in this way and that it could not be applied advantageously into the feather follicles as is done with pox vaccine. During the fall of 1941 one of us (P.C.M.), while conducting experiments with Fowl Laryngotracheitis Vaccine, brushed the vaccine into the feather follicles on the legs of a few chickens as one, would do if vaccinating with pox vaccine. It was noted that the follicles began to swell on the second day, that the reaction reached its peak on about the fifth day, and that the swelling receded completely by the seventh or eighth day. The reaction or "take," was similar to that which appears after applying Pigeon Pox Vaccine to the follicles. However, the time elapsing during the development and recession of the take corresponded to the length of time required for a reaction to appear and
recede when laryngotracheitis virus is applied in the vent. After this observation had been made a few times the question, naturally, was raised, Would follicle vaccination produce immunity in chickens similar to that established when the vaccine is applied in the vent? To determine this, further experiments were set up with the assistance of Dr. W. G. Keehn, at that time bacteriologist at Dr. Salsbury's Laboratories. EXPERIMENTAL TESTS
On January 5, 1942, two chickens were each vaccinated by applying Laryngotracheitis Vaccine in the vent and, also, the vaccine was brushed into ten feather follicles on the right thigh of each chicken. The resulting reactions are shown in Table 1. On January 19, 1942, six New Hampshire chickens, 14 weeks of age, were vaccinated with a commercial vaccine in ten feather follicles on the leg. Six others were vaccinated in the vent. The results shown in Table 2 were obtained. On January 22, 1942, nine chickens,
563
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
T h e Feather Follicle Method of Vaccinating with Fowl.Laryngotracheal s Vaccine
564
P . C. MOLGARD AND J . W . CAVETT TABLE 1*
Chicken 1-7 no. 101 102
+ +
101 102
— —
!
1-8
1-9
1-10
Follicle reactions 2+ 3 + 2 + 2 + 3+ + Vent reactions 2+ 3 + 2+ 3++ +
1-11
1-12
1+ —
— —
4+ Receding 4 + Receding
five weeks of age (identified by band numbers 832, 847, 846, 818, 815, 857, 799, 848, 1008), were vaccinated in the feather follicles. On the fifth day these chickens showed 3 + reactions. Four other chickens of the same batch (identified by band numbers 814, 840, 842, 849) were used as controls. Sterile distilled water applied to the feather follicles of these chickens, produced no reaction. An experiment was begun January 26, 1942, with four Barred Rocks, 10 months of age (band numbers 3073, 5571, 3030, 3070), and five New Hampshires, 15 weeks of age (band numbers 668, 669,
TABLE 2
Chicken no.
1-21
1-22
1-23
1 2 3 4 5 6
+ + + + + +
242+ 2+ 2+ 2+ 2+
3+ 3+ 3+ 3+ 3+ 3+
7 8 9 10 11 12
— — — — — —
— — — — — —
— 2+
+ + 2+ 2+
1-24
1-25
Follicle-vaccinated 3+ 4+ 3+ 4+ 3+ 4+ 3+ 4+ 3+ 4+ 3+ 4+ Vent-vaccinated
2+
3+ 2+ 3+ 2+ 3+
+
3+ + 3+ + 3+
1-26
1-27
2+ 2+ 2+ 2+ 2+ 2+
+ + + + + +
+ + +
1-28
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
Key to Reactions: — = Normal + = Mild reaction (unsatisfactory) 2 + = Fair reaction (satisfactory) 3 + = Excellent reaction 4 + = Extra strong reaction
670, 671, and 672). These chickens previously had been vaccinated with Fowl Laryngotracheitis Vaccine by the vent method and had shown satisfactory takes. These chickens now were each vaccinated with Laryngotracheitis Vaccine in the feather follicles of the right thigh. At the same time sterile distilled water was applied to the feather follicles on the left thigh of each chicken. No reactions were produced by any of these inoculations, indicating that the takes observed in follicle-vaccinated birds in previous tests actually were due to the action of laryngotracheitis virus. Further tests to observe and compare the degree of immunity obtained from follicle and vent methods of vaccination were started on February 2, 1942, when the six chickens which had been vaccinated by the follicle method on January 19, and the nine vaccinated January 22 were each inoculated intratracheally with laryngotracheitis virus to determine whether the follicle inoculations had caused them to become immune to laryngotracheitis virus. As a control group, the six chickens vaccinated January 19 by the vent method, five chickens vaccinated December 12 by the vent method which
VACCINATION METHOD FOR LARYNGOTRACHEITIS
On February 25, 1942, thirteen 5-weekold chickens (band numbers 1586 to 1598 inclusive) were vaccinated in the feather follicles with a commercial vaccine. At the same time 11 other thickens (band numbers 1601 to 1611 inclusive) were vaccinated with a strain of laryngotracheitis virus isolated from a flock in Minnesota. Reactions were identical for all chickens,
indicating that another strain would produce similar results. On May 6, 1942, eight chickens picked at random from this group were tested for immunity by intratracheal inoculation with laryngotracheitis virus. None of them developed any symptoms of the disease. At the same time four susceptible chickens, inoculated with the same virus, developed the disease and two died. These results indicate that immunity had been established in the follicle-vaccinated chickens. Since it was evident from experiments conducted up to this time that feather follicle vaccinations produced as good results as the vent vaccinations, the question naturally was raised as to whether immunity could be produced by introducing Laryngotracheitis Vaccine into the skin of chickens by the use of stab-type vaccinators used for pox vaccination. On March 13,1942, three groups of chickens, six in each group, were vaccinated in the wing webs. Three different types of pox vaccinators were used for this experiment. A fourth group of seven chickens was vaccinated by the follicle method. The wing web reactions were negative or, mild while all follicle reactions were strong. To determine whether the wing web-vaccinated chickens had developed immunity to laryngotracheitis virus, 12 of these wing-vaccinated chickens were inoculated intratracheally with laryngotracheitis virus on May 6. At the same time five of the follicle-vaccinated chickens were inoculated with the same virus. The result was that five of the wingweb-vaccinated chickens developed the disease and three died. None of the feather follicle-vaccinated chickens developed the disease. From the results of this experiment, wing web vaccination does not appear to be a satisfactory method. An entire hatch of New Hampshire chicks, hatched on April 23, 1942, was
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
when examined all showed satisfactory takes, and five New Hampshire laryngotracheitis-susceptible chickens were also inoculated intratracheally with the same virus. Four of the laryngotracheitissusceptible chickens developed laryngotracheitis and two of them died. One did not develop the disease. No symptoms of laryngotracheitis were observed in any of the fifteen follicle-vaccinated chickens or the eleven vent-vaccinated chickens. These results indicate that immunity had been established in all vaccinated chickens. On February 21, 1942, tests were started on three groups of chickens. Group 1, consisting of nine 3-week-old chicks, was vaccinated by the follicle method and developed only + reactions. On May 6, seven of these chickens were inoculated intratracheally with laryngotracheitis virus, one of them developing the disease. Group 2, consisting of six 6-week-old chickens, was follicle vaccinated and produced 3 + reactions. Four of these inoculated intratracheally on May 6 did not develop laryngotracheitis, indicating that immunity had been established by the follicle vaccination. Group 3, consisting of five birds which had recovered from the disease and six chickens which previously had shown satisfactory vent vaccinations, developed no takes when inoculated in the feather follicle. This again indicated that laryngotracheitis-immune chickens would not develop follicle reactions when inoculated with laryngotracheitis virus.
565
566
P. C. MOLGARD AND J. W. CAVETT
On June 17, 1942, 120 New Hampshire chickens hatched May 14 (band numbers 2750 to 2869) were vaccinated with Laryngotracheitis Vaccine in the feather follicles of the right thigh. At the same time these same chickens were also vaccinated with Fowl Pox Vaccine, 60 in the feather follicles of the left thigh and 60 in the wing web by the stab method. No untoward results followed the use of both pox and laryngotracheitis vaccine on these chickens at the same time. The following winter chickens picked at random from this group were periodically inoculated intratracheally with laryngotracheitis virus, which did not cause them to develop the disease.
DISCUSSION OF EXPERIMENTAL RESULTS
After finding in the laboratory that laryngotracheitis virus, when placed in feather follicles of the chicken, will produce immunity to laryngotracheitis, these questions arose: 1. Could this method of vaccinating be used successfully in the field? 2. What advantages, if any, would it have over the vent method? One of the chief objections to the vent method is the "watery vent" which is often encountered if the flock has not had proper care before vaccinating time. This watery condition may have a tendency to dilute or wash out the virus before it becomes established. This may be the reason why some vent-vaccinated chickens fail to develop reactions and remain susceptible to the disease. Follicle vaccinations produce strong takes on nearly every chicken as the virus, when it is once placed in the feather follicle, stands little chance of being expelled. When a laryngotracheitis reaction in the vent reaches its peak, an excessive amount of mucus is expelled. Undoubtedly, this causes the release of much laryngotracheitis virus. When the follicle method of vaccination is used, scarcely any secretion or exudate is thrown off. As a result, the virus is much less likely to cause heavy contamination of the premises. It appears that this should be a distinct advantage in favor of follicle vaccination. FARM FLOCK VACCINATION
On May 23, 1942, a farm flock of 2,025 White Leghorn chickens, 11 weeks of age, was vaccinated with Laryngotracheitis Vaccine, 1,992 by the vent method and 33 by the follicle method. On the fifth day all chickens were examined for takes. All follicle-vaccinated chickens showed good
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
held for use in further experimentation. On May 7, at two weeks of age, 39 of these chicks were vaccinated, 20 by the vent method and 19 by the follicle method. Two of the vent vaccinations produced unsatisfactory takes, while all of the follicle vaccinations showed satisfactory reactions. On May 28, at five weeks of age, another group of 20 chickens was vaccinated by the vent method and 20 by the follicle method. All reactions were satisfactory. On May 29, at five weeks of age, 13 chickens were vaccinated in the wing webs by the stab method. The stab method again produced only mild reactions. On June 15, at seven weeks of age, 20 chickens were vaccinated in the vent and 20 in the follicles. Three of the ventvaccinated chickens developed only + reactions whereas all follicle reactions were satisfactory. At various times during the following year, follicle-vaccinated chickens were removed from this flock and inoculated intratracheally with laryngotracheitis virus. None of these chickens developed laryngotracheitis, whereas unvaccinated chickens which were inoculated with the same virus developed the disease.
VACCINATION METHOD FOR LARYNGOTRACHEITIS
During the past four seasons this method has been used successfully on a considerable number of flocks and no untoward results have been reported from the field. SUMMARY
1. It has been demonstrated that Fowl Laryngotracheitis Vaccine, when placed in the feather follicle of the chicken, will produce immunity to laryngotracheitis as it does when the vaccine is introduced into the vent or Bursa of Fabricius. 2. A follicle reaction expels very little exudate whereas a heavy take in the vent causes a relatively profuse exudation. 3. Follicle vaccinations give a higher
percentage of readable takes than are produced when chickens are vaccinated in the vent. Watery vents are not a problem when follicle method vaccination is used. 4. The results obtained in the field through vaccinating by this method have been very satisfactory. ADDENDUM
Since submitting this paper, a commercial Fowl Laryngotracheitis Vaccine which was being tested for other purposes was applied to the feather follicles of two chickens. A very questionable reaction developed. Since this strain of virus was being cultured on eggs, another feather follicle test was made using the material prepared in this Laboratory and also with another sample of the same commercial vaccine as prepared by the producer. Again, the takes which developed in the follicles from inoculation with both preparations were very questionable. Both vaccines produced excellent vent takes on other chickens from the same flock. The follicle vaccinated chickens were revaccinated four weeks later with a potent virus and no takes developed. Vaccines prepared by five other commercial concerns were purchased and tested for follicle reaction. One group of chickens was vaccinated by the vent method to determine if the virus was potent and to observe the take produced. Other chickens were also vaccinated by the follicle method. All five vaccines gave follicle reactions similar to those produced by the two strains we had used in our work. It has been suggested that this one strain of fowl laryngotracheitis virus is a mutant which, although it produces good vent reactions, does not produce very marked reaction in the follicle.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 22, 2015
reactions, but it was found that 3.4 percent of the vent-vaccinated chickens did not show a visible reaction. A flock of 3,161 White Leghorns, 14 weeks of age, belonging to the same poultry raiser, was vaccinated June 23, 1942, 2,108 by the vent method and 1,053 by the follicle method. On the fifth day examination revealed that 4.55 per cent of the vent-vaccinated chickens showed unsatisfactory takes. These chickens were revaccinated but it was impossible to observe the revaccinated chickens at the proper time because they had not been kept isolated. All of the 1,053 folliclevaccinated chickens developed satisfactory reactions from the first vaccination. The cockerels of this flock were sold at housing time, but the pullets were housed and held throughout the year. During this time observation revealed no distinguishable difference between the vent and follicle-vaccinated chickens. Since that time the owner of these flocks and the people associated with him have vaccinated between 20 and 30 thousand chickens each year and have used only the follicle method of vaccination.
567