Horizontal Transmission of Turkey Herpesvirus to Chickens 3. TRANSMISSION IN THREE DIFFERENT LINES OF CHICKENS' B. R. CHO AND S. G.
KENZY
Department of Veterinary Science, Washington Agricultural Experiment Station; and Department Veterinary Microbiology, Washington State University, Pullman, Washington 99163
of
(Received for publication April 4, 1974)
POULTRY SCIENCE 54: 109-115, 1975
INTRODUCTION
H
ORIZONTAL transmission of turkey herpesvirus (HVT) from inoculated chickens to contact cagemates and some of the factors affecting such transmission were previously reported (Cho et al, 1971, 1973). Those studies were done with an experimental line of White Leghorns selectively bred for enhanced susceptibility to Marek's disease herpesvirus (MDHV). This study was to compare the horizontal transmission of HVT in three different lines of chickens. MATERIALS AND METHODS Experimental Chickens. The three lines of chickens employed were an experimental line of White Leghorns (W.S.U.-V.S.) which were progenies of Cornell S x RPL Line
7, and two commercial lines, one of White Leghorns (C.-W.L.) and one of meat-type (C.-M.T.) chickens. W.S.U.-V.S. chicks highly susceptible to MD were the same as those used in the previous studies (Cho et al., 1971,1973). C.-W.L. chicks were hatched at the department from fertile eggs obtained from a commercial specific-pathogen-free (SPF) flock (H & N Inc.). C.-M.T. chicks from another commercial source were obtained as day-olds. The parent stocks of these chicks were not free of MDHV infection and those of C.-M.T. had been vaccinated with HVT vaccine. The hatching and rearing of these chicks were done as described previously (Cho. et al., 1968). Chicken Embryos for Cell Cultures. Fertile White Leghorn eggs from a commercial SPF flock (H & N Inc.) served as a source of embryos for chicken embryo fibroblast (CEF) cell cultures which were prepared as described previously (Cho et al, 1971).
1. Supported in part by funds from Project 10A3073-1773, 10A-3073-0138, Washington Agricultural Experiment Station and Grant No. 12-14-100-9929, Agricultural Research Grant, USDA, Scientific Paper No. 4213.
HVT. 109
In all trials, cell-associated HVT (FC
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ABSTRACT Horizontal transmission of turkey herpesvirus (HVT) was studied in three separate trials using three different lines of chickens in each trial. There was no horizontal spread of HVT to contact cagemates through 8 weeks regardless of the line of donor chickens, when inoculated subcutaneously with 9.2 x 103 plaque-forming units (PFU) of HVT at 1 week of age. The virus spread poorly to a few cagemates from an experimental line of White Leghorns (W.S.U.-V.S.), but not from a commercial line of White Leghorns (C.-W.L.) or meat-type (C.-M.T.) chickens, when inoculated with 9.4 x 104 PFU of HVT at 1 week of age. The virus spread readily to contact cagemates from W.S.U.-V.S. but not at all from C.-W.L. or C.-M.T. chickens when inoculated with 2 x 104 PFU of HVT at 8 weeks of age. The incidence among cagemates of contact infection by HVT appeared similar regardless of genetic lines. This observation indicated a difference among different genetic lines of chickens in the development and/or shedding of infectious HVT following virus inoculation.
110
B. R. CHO AND S. G. KENZY
TABLE 1.—Experimental design
Within each group HVT-inoculated donors Trial
Contact cagemates
Group
Chicken line
HVT-dose per donor
Exposure age
A
W.S.U.-V.S.'(3) 2
9.2 x 103 PFU 3
1 week
B
C.-W.L. 4 (3)
9.2 x 103 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
„
C
C.-M.T. 5 (3)
9.2 x 103 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
"
D
None
W.S.U.-V.S. (4) C.-W.L. (4) C.-M.T. (4)
"
A
W.S.U.-V.S. (3)
9.4 x 104 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
B
C.-W.L. (3)
9.4 x 104 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
C
C.-M.T. (3)
9.4 x 104 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
D
None
A
W.S.U.-V.S. (2)
1
B
C.-W.L. (2)
W.S.U.-V.S. (5) C.-W.L. (5) C.-M.T. (5) 2 x 104 PFU
2 x 104 PFU
D
C.-M.T. (2)
2 x 10" PFU
1 An experimental line of White Leghorn 2 Number of birds. 3 Plaque-forming units. 4 A commercial line of White Leghorn. 5
1 week
„ »
„
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
8 days
8 days
8 weeks
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
8 weeks
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12) W.S.U.-V.S. (4) C.-W.L. (4) C.-M.T. (4)
None
1 week
8 weeks
3 C
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
Exposure age
4 days
4 days 8 days 4 days 8 days 4 days
Cross (Cornell S X RPL Line 7).
A commercial line of meat-type birds.
126 strain) grown in CEF cell cultures was employed at the 14th (Trial 1) and 18th passage (Trials 2 and 3) for inoculation of donor chickens. The procedures for preparing and assaying HVT inocula in CEF cell cultures have been described (Cho et al., 1971, 1973).
Experimental Design. Three trials were undertaken employing three lines of chickens in each trial as shown in Table 1. Trial 1. The W.S.U.-V.S., C.-W.L., and C.-M.T. chicks were allocated into Groups A through D and treated at 1 week of age
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->
Chicken line
111
TRANSMISSION OF HERPESVIRUS
Trial 2. This trial was similar to Trial 1 except for inoculation of donor birds with a greater dose of HVT (9.4 x 10" PFU). When selected hatchmates were tested at the time of treatment, none of 5 W.S.U.-V.S., 3 of 5 C.-M.T., and all 5 C.-W.L. chicks were positive for HVT precipitins. Trial 3. This trial was similar to other trials but differed as follows: Each of 2 donor birds in each group was inoculated subcutaneously with 2 x 104 PFU of HVT at 8 weeks of age. W.S.U.-V.S. and C.-W.L. contact cagemates were 8 days and C.-M.T. chicks 4 days of age when exposed. When selected hatchmates were tested for maternal HVT precipitins at the time of treatment, none of 6 W.S.U.-V.S., one each
of 6 C.-W.L., and 6 C.-M.T. chicks were positive. RESULTS The results are summarized in Table 2. Trial 1. None of the contact cagemates in all groups was found to be infected with HVT through 8 weeks post-contact as indicated by failure to detect HVT viremia or precipitins against HVT antigens. The inoculated donor birds, however, were viremic and/or positive for HVT precipitins. All donors of Groups A and C and one of Group B were viremic with HVT. One of C.-W.L. (Group B) and 2 of C.-M.T. (Group C) donors, but none of W.S.U.-V.S. donors, had detectable HVT precipitins. Control birds (group D) consisting of 4 hatchmates from each of the three lines were all negative for HVT viremia and precipitins. Trial 2. At 4 weeks post-contact, none of the contact cagemates from Groups A, B, and C was found to be viremic or positive for HVT precipitins. At 8 weeks post-contact, there was horizontal spread of HVT to a few cagemates. However, the spread was found only in Group A (W.S.U.-V.S. donors) in which one from each of the three lines of contact cagemates was viremic and the one viremic C.-W.L. cagemate was also positive for HVT precipitins. All W.S.U.-V.S. donors of Group A were viremic without detectable antibodies. None of the contact cagemates of Groups B and C was viremic or positive for HVT precipitins, although every donor of Group B (C.-W.L. donors) and Group C (C.-M.T. donors) were viremic and one of Group B and all of Group C donors also positive for HVT precipitins. Non-exposed control birds (Group D) consisting of 5 hatchmates from each of the three lines were all negative for HVT viremia and antibodies.
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in the following manner. Each group (A, B, and C) consisted of 3 inoculated donors and 12 chicks each of the three lines as contact cagemates. The donor chicks in each group came from each one of the three lines and each donor chick was inoculated subcutaneously with 9.2 x 103 plaque-forming units (PFU) of HVT. Untreated controls (Group D) consisted of 4 hatchmates from each of the three lines. When 6 hatchmates from each of the three lines of chickens were examined at the time of treatment for maternal HVT antibodies by micro agar gel precipitin test (Okazaki et at, 1970), 5 each of C.-W.L. and C.-M.T. chicks, but none of the W.S.U.-V.S. chicks, were weakly positive. Half from each of the three lines of contact cagemates of Groups A through C was removed and tested for HVT infection at 4 weeks and the rest including donors and control birds (Group D) at 8 weeks after treatment. Horizontal transmission of HVT was determined by examining heparinized blood for HVT viremia and plasma samples for HVT precipitins as described previously (Cho et al., 1971).
Trial
0/6
Contact cagemates: W.S.U.-V.S.
"
NT
C.-W.L., inoculated donors (9.4 x 104 PFU)
„
NT
W.S.U.-V.S., inoculated donors (9.4 x 104 PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
0/6 0/6 0/6
NT
(Controls, 4 hatchmates each of the 3 lines)
D
A
0/6 0/6 0/6
Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
C
,,
NT
0/6 0/6 0/6
"
Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
0/6 0/6 0/6
NT 3
A
HVT virem P 4 weeks Viremia
NT
"
1 week
Exposure age
C.-W.L., inoculated donors (9.2 x 103 PFU)
Contact cagemates: W.S.U.-V.S. C.-W.L. 5 C.-M.T. 6
W.S.U.-V.S.', inoculated donors (9.2 x 103 PFU) 2
Exposure method
C.-M.T., inoculated donors (9.2 x 103 PFU)
B
A
Group
Exposure to HVT
TABLE 2.—Horizontal transmission of turkey herpesvirus (HVT) in three differ
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B
A
D
C
C.-W.L., inoculated donors (2 x 104 PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
(Controls, 5 hatchmates each of 3 lines) W.S.U.-V.S., inoculated donors (2 x 10" PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
8 days
4 days 8 weeks
8 days
8 weeks
3
4 days C.-M.T., inoculated donors 8 weeks (2 x 104 PFU) C Contact cagemates: W.S.U.-V.S. 8 days C.-W.L. C.-M.T. 4 days D (Controls, 4 hatchmates each 8 days of 3 lines) 4 days 'An experimental line of White Leghorns Cross (Cornell S x RPL Line 7). 2 Plaque-forming units. 3 Not tested. 4 Number of birds positive/number of birds examined. 5 A commercial line of White Leghorns. 6 A commercial line of meat-type chickens. 'A few chicks died of smothering within a week.
2
C.-W.L. C.-M.T. C.-M.T., inoculated donors (9.4 x 10" PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
0/6 0/6 0/6 NT
0/6 0/6 0/3' NT
0/6 1/6 0/6 NT
NT
0/6 0/6 0/6 NT
0/6 0/6 NT
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114
B. R. CHO AND S. G. KENZY
DISCUSSION HVT spread readily to contact cagemates from W.S.U.-V.S. donor chickens inoculated with 2 x 104 PFU of HVT at 8 weeks of age, while the virus either did not spread or poorly spread when inoculated at 1 week of age with 9.2 x 103 and 9.4 x 104 PFU of HVT, respectively. However, in corresponding groups employing C.-W.L. and C.-M.T. birds as inoculated donors, there was no horizontal spread of HVT. This observation indicated that W.S.U.V.S. chickens were capable of shedding infectious HVT following virus inoculation, while C.-W.L. and C.-M.T. birds were not, and suggested the genetic difference among lines of chickens in the development a n d / o r shedding of infectious HVT following virus
inoculation. Development of infectious HVT in the feather follicle epithelium, by analogy with MDHV, have been reported in chickens (Zygraich et al., 1972) and in turkeys (Witter et al., 1972). It was interesting to note that W.S.U.-V.S. birds highly susceptible to MD could become shedders of HVT, while the less MD-susceptible C.-W.L. and C.-M.T. birds failed to shed HVT. It was not likely that the observed difference in shedding HVT resulted from dissimilarity among the three lines of chickens in the level of passive immunity against MDHV and/or HVT, since 1) the source flock of C.-W.L. as well as W.S.U.-V.S. had never been exposed to HVT, and maternal HVT precipitins detected in some of the W.S.U.-V.S. and C.-W.L. birds were probably due to cross reaction of HVT antigens with MDHV antibodies (Witter et al, 1970); 2) HVT and MDHV maternal antibodies were known to have little or no effect on infection of chicks by cellassociated HVT (Eidson et al., 1973; Petrascu et al., 1972); and 3) maternal HVT and MDHV antibodies were found to disappear by the third to fifth week after hatching (Witter et al., 1971; Sharma et al., 1972). The results of this study confirmed the previous observations (Cho et al., 1971, 1973) which had shown the age of donor chickens at the time of HVT inoculation and the dose of HVT given to donor birds to be important factors determining horizontal transmission of HVT among chickens. ACKNOWLEDGEMENT We thank Mr. W. R. Bryson and Mrs. D. Edwards for excellent technical assistance. REFERENCES Cho, B. R., and S. G. Kenzy, 1973. Horizontal transmission of turkey herpesvirus to chickens. 2. Some factors affecting transmission. Poultry Sci. 52: 608-613. Cho, B. R., S. G. Kenzy and S. A. Haider, 1971. Horizontal transmission of turkey herpesvirus to
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Trial 3. At 4 weeks post-contact, all of the contact cagemates tested were negative for viremia (HVT) or for HVT precipitins, except one of C.-W.L. cagemates of Group A (W.S.U.-V.S. donors) which was viremic without detectable antibodies. At 8 weeks post-contact, there was horizontal spread of HVT which occurred only in those cagemates of Group A but not of Groups B and C. In Group A, 3 of 5 W.S.U.V.S., one of 6 C.-W.L., and 3 of 6 C.-M.T. cagemates were viremic. One each of the viremic W.S.U.-V.S. and C.-W.L. cagemates was also positive for HVT precipitins. Donors of Group A were all viremic without detectable HVT precipitins. However, in Groups B and C (C.-W.L. and C.-M.T. donor birds, respectively), none of the contact cagemates was viremic or positive for HVT precipitins. In these two groups, donors were also nonviremic but one of Group B and 2 of Group C donors were positive for HVT precipitins. Non-exposed control birds (Group D) consisting of 4 hatchmates from each of the three lines were all free of HVT viremia and antibodies.
TRANSMISSION OF HERPESVIRUS
Sharma, J. M., and H. A. Stone, 1972. Genetic resistance to Marek's disease. Delineation of the response of genetically resistant chickens to Marek's disease virus infection. Avian Dis. 16: 894-906. Witter, R. L., K. Nazerian, H. G. Purchase and G. H. Burgoyne, 1970. Isolation from turkey of a cell-associated herpesvirus antigenically related to Marek's disease virus. Am. J. Vet. Res. 31: 525-538. Witter, R. L., K. Nazerian and J. J. Solomon, 1972. Studies in the in vivo replication of turkey herpesvirus. J. Nat. Cancer Inst. 49: 1121-1130. Witter, R. L., and J. J. Solomon, 1971. Epidemiology of a herpesvirus of turkeys: Possible sources and spread of infection in turkey flocks. Infect. Immunity 4: 356-361. Zygraich, N., and C. Huygelen, 1972. Inoculation of one-day-old chicks with different strains of turkey herpesvirus. II. Virus replication in tissues of inoculated animals. Avian Dis. 16: 793-798.
NEWS AND NOTES (Continued from page 90)
SHAVER NOTES During 1974, the Centennial Year of the Ontario Agricultural College, University of Guelph, Centennial Medals will be presented to 100 living individuals, other than present faculty or staff, who have made a significant contribution to the advancement of agriculture, and supported and assisted the various programs of the College. On June 12, during the Poultry Institute Conference held in London, Ontario, a Medal was presented to Donald McQ. Shaver. The citation read: "Donald McQueen Shaver, Chairman and Chief Executive Officer, Shaver Poultry Breeding Farms, Cambridge, Ontario, has developed one of the leading egg production type birds in the world. It is now distributed in some 60 countries. As a boy he bred laying chickens and, at the age of 15, entered these in the Canadian Egg Laying Contest held in Ottawa. His entry of White Leghorns won the contest. "He served with the Montreal Hussars Armored Regiment in World War II, and was discharged with the rank of Major.
"After the War he returned to his poultry operations and produced the World's Champion Layer, which produced 360 eggs in 365 days. He named her Hussar's Pride. Shaver Starcross 288, a hybrid layer developed in Canada, was first marketed in 1955 and was the recent winner of the Poultry Tribune Trophy. The winner of this Trophy is selected on the basis of highest income over feed and chick cost per pullet housed as computed by the U.S. Department of Agriculture in its two year summary of Random Sample Egg Production Tests. This was the fourth win in four years, and a seven-time win in nine years. "He received the Ontario Poultry Council Award of Merit in 1969. He has initiated a crossbreeding project with beef cattle. "Mr. Shaver included the underdeveloped countries in the international organization he developed to bring the benefits of Canadian technology to the World's less fortunate people. He recognized that it was necessary not only to supply a Canadian bird but that technological skills were also needed. The Company operates a successful training program to impart the
(Continued on page 118)
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chickens. 1. Preliminary observation. Poultry Sci. 50: 881-887. Cho, B. R., S. G. Kenzy and U. H. Kim, 1968. Atypical cells in the peripheral blood of chickens exposed to Marek's disease agent. Canad. J. Comp. Med. 32: 562-567. Eidson, C. S., S. H. Kleven and D. P. Anderson, 1973. Efficacy of cell-free and cell-associated herpesvirus of turkeys vaccines in progeny from vaccinated parental flocks. Am. J. Vet. Res. 34: 869-872. Patrascu, I. V., B. W. Calnek and M. W. Smith, 1972. Vaccination with lyophilized turkey herpesvirus (HVT): Minimum infective and protective doses. Avian Dis. 16: 86-93. Okazaki, W., H. G. Purchase and L. Noll, 1970. Effect of different conditions on precipitation in agar between Marek's disease antigen and antibody. Avian Dis. 14: 532-537.
115
KENZY
Department of Veterinary Science, Washington Agricultural Experiment Station; and Department Veterinary Microbiology, Washington State University, Pullman, Washington 99163
of
(Received for publication April 4, 1974)
POULTRY SCIENCE 54: 109-115, 1975
INTRODUCTION
H
ORIZONTAL transmission of turkey herpesvirus (HVT) from inoculated chickens to contact cagemates and some of the factors affecting such transmission were previously reported (Cho et al, 1971, 1973). Those studies were done with an experimental line of White Leghorns selectively bred for enhanced susceptibility to Marek's disease herpesvirus (MDHV). This study was to compare the horizontal transmission of HVT in three different lines of chickens. MATERIALS AND METHODS Experimental Chickens. The three lines of chickens employed were an experimental line of White Leghorns (W.S.U.-V.S.) which were progenies of Cornell S x RPL Line
7, and two commercial lines, one of White Leghorns (C.-W.L.) and one of meat-type (C.-M.T.) chickens. W.S.U.-V.S. chicks highly susceptible to MD were the same as those used in the previous studies (Cho et al., 1971,1973). C.-W.L. chicks were hatched at the department from fertile eggs obtained from a commercial specific-pathogen-free (SPF) flock (H & N Inc.). C.-M.T. chicks from another commercial source were obtained as day-olds. The parent stocks of these chicks were not free of MDHV infection and those of C.-M.T. had been vaccinated with HVT vaccine. The hatching and rearing of these chicks were done as described previously (Cho. et al., 1968). Chicken Embryos for Cell Cultures. Fertile White Leghorn eggs from a commercial SPF flock (H & N Inc.) served as a source of embryos for chicken embryo fibroblast (CEF) cell cultures which were prepared as described previously (Cho et al, 1971).
1. Supported in part by funds from Project 10A3073-1773, 10A-3073-0138, Washington Agricultural Experiment Station and Grant No. 12-14-100-9929, Agricultural Research Grant, USDA, Scientific Paper No. 4213.
HVT. 109
In all trials, cell-associated HVT (FC
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on July 2, 2015
ABSTRACT Horizontal transmission of turkey herpesvirus (HVT) was studied in three separate trials using three different lines of chickens in each trial. There was no horizontal spread of HVT to contact cagemates through 8 weeks regardless of the line of donor chickens, when inoculated subcutaneously with 9.2 x 103 plaque-forming units (PFU) of HVT at 1 week of age. The virus spread poorly to a few cagemates from an experimental line of White Leghorns (W.S.U.-V.S.), but not from a commercial line of White Leghorns (C.-W.L.) or meat-type (C.-M.T.) chickens, when inoculated with 9.4 x 104 PFU of HVT at 1 week of age. The virus spread readily to contact cagemates from W.S.U.-V.S. but not at all from C.-W.L. or C.-M.T. chickens when inoculated with 2 x 104 PFU of HVT at 8 weeks of age. The incidence among cagemates of contact infection by HVT appeared similar regardless of genetic lines. This observation indicated a difference among different genetic lines of chickens in the development and/or shedding of infectious HVT following virus inoculation.
110
B. R. CHO AND S. G. KENZY
TABLE 1.—Experimental design
Within each group HVT-inoculated donors Trial
Contact cagemates
Group
Chicken line
HVT-dose per donor
Exposure age
A
W.S.U.-V.S.'(3) 2
9.2 x 103 PFU 3
1 week
B
C.-W.L. 4 (3)
9.2 x 103 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
„
C
C.-M.T. 5 (3)
9.2 x 103 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
"
D
None
W.S.U.-V.S. (4) C.-W.L. (4) C.-M.T. (4)
"
A
W.S.U.-V.S. (3)
9.4 x 104 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
B
C.-W.L. (3)
9.4 x 104 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
C
C.-M.T. (3)
9.4 x 104 PFU
1 week
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
D
None
A
W.S.U.-V.S. (2)
1
B
C.-W.L. (2)
W.S.U.-V.S. (5) C.-W.L. (5) C.-M.T. (5) 2 x 104 PFU
2 x 104 PFU
D
C.-M.T. (2)
2 x 10" PFU
1 An experimental line of White Leghorn 2 Number of birds. 3 Plaque-forming units. 4 A commercial line of White Leghorn. 5
1 week
„ »
„
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
8 days
8 days
8 weeks
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
8 weeks
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12) W.S.U.-V.S. (4) C.-W.L. (4) C.-M.T. (4)
None
1 week
8 weeks
3 C
W.S.U.-V.S. (12) C.-W.L. (12) C.-M.T. (12)
Exposure age
4 days
4 days 8 days 4 days 8 days 4 days
Cross (Cornell S X RPL Line 7).
A commercial line of meat-type birds.
126 strain) grown in CEF cell cultures was employed at the 14th (Trial 1) and 18th passage (Trials 2 and 3) for inoculation of donor chickens. The procedures for preparing and assaying HVT inocula in CEF cell cultures have been described (Cho et al., 1971, 1973).
Experimental Design. Three trials were undertaken employing three lines of chickens in each trial as shown in Table 1. Trial 1. The W.S.U.-V.S., C.-W.L., and C.-M.T. chicks were allocated into Groups A through D and treated at 1 week of age
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on July 2, 2015
->
Chicken line
111
TRANSMISSION OF HERPESVIRUS
Trial 2. This trial was similar to Trial 1 except for inoculation of donor birds with a greater dose of HVT (9.4 x 10" PFU). When selected hatchmates were tested at the time of treatment, none of 5 W.S.U.-V.S., 3 of 5 C.-M.T., and all 5 C.-W.L. chicks were positive for HVT precipitins. Trial 3. This trial was similar to other trials but differed as follows: Each of 2 donor birds in each group was inoculated subcutaneously with 2 x 104 PFU of HVT at 8 weeks of age. W.S.U.-V.S. and C.-W.L. contact cagemates were 8 days and C.-M.T. chicks 4 days of age when exposed. When selected hatchmates were tested for maternal HVT precipitins at the time of treatment, none of 6 W.S.U.-V.S., one each
of 6 C.-W.L., and 6 C.-M.T. chicks were positive. RESULTS The results are summarized in Table 2. Trial 1. None of the contact cagemates in all groups was found to be infected with HVT through 8 weeks post-contact as indicated by failure to detect HVT viremia or precipitins against HVT antigens. The inoculated donor birds, however, were viremic and/or positive for HVT precipitins. All donors of Groups A and C and one of Group B were viremic with HVT. One of C.-W.L. (Group B) and 2 of C.-M.T. (Group C) donors, but none of W.S.U.-V.S. donors, had detectable HVT precipitins. Control birds (group D) consisting of 4 hatchmates from each of the three lines were all negative for HVT viremia and precipitins. Trial 2. At 4 weeks post-contact, none of the contact cagemates from Groups A, B, and C was found to be viremic or positive for HVT precipitins. At 8 weeks post-contact, there was horizontal spread of HVT to a few cagemates. However, the spread was found only in Group A (W.S.U.-V.S. donors) in which one from each of the three lines of contact cagemates was viremic and the one viremic C.-W.L. cagemate was also positive for HVT precipitins. All W.S.U.-V.S. donors of Group A were viremic without detectable antibodies. None of the contact cagemates of Groups B and C was viremic or positive for HVT precipitins, although every donor of Group B (C.-W.L. donors) and Group C (C.-M.T. donors) were viremic and one of Group B and all of Group C donors also positive for HVT precipitins. Non-exposed control birds (Group D) consisting of 5 hatchmates from each of the three lines were all negative for HVT viremia and antibodies.
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in the following manner. Each group (A, B, and C) consisted of 3 inoculated donors and 12 chicks each of the three lines as contact cagemates. The donor chicks in each group came from each one of the three lines and each donor chick was inoculated subcutaneously with 9.2 x 103 plaque-forming units (PFU) of HVT. Untreated controls (Group D) consisted of 4 hatchmates from each of the three lines. When 6 hatchmates from each of the three lines of chickens were examined at the time of treatment for maternal HVT antibodies by micro agar gel precipitin test (Okazaki et at, 1970), 5 each of C.-W.L. and C.-M.T. chicks, but none of the W.S.U.-V.S. chicks, were weakly positive. Half from each of the three lines of contact cagemates of Groups A through C was removed and tested for HVT infection at 4 weeks and the rest including donors and control birds (Group D) at 8 weeks after treatment. Horizontal transmission of HVT was determined by examining heparinized blood for HVT viremia and plasma samples for HVT precipitins as described previously (Cho et al., 1971).
Trial
0/6
Contact cagemates: W.S.U.-V.S.
"
NT
C.-W.L., inoculated donors (9.4 x 104 PFU)
„
NT
W.S.U.-V.S., inoculated donors (9.4 x 104 PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
0/6 0/6 0/6
NT
(Controls, 4 hatchmates each of the 3 lines)
D
A
0/6 0/6 0/6
Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
C
,,
NT
0/6 0/6 0/6
"
Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
0/6 0/6 0/6
NT 3
A
HVT virem P 4 weeks Viremia
NT
"
1 week
Exposure age
C.-W.L., inoculated donors (9.2 x 103 PFU)
Contact cagemates: W.S.U.-V.S. C.-W.L. 5 C.-M.T. 6
W.S.U.-V.S.', inoculated donors (9.2 x 103 PFU) 2
Exposure method
C.-M.T., inoculated donors (9.2 x 103 PFU)
B
A
Group
Exposure to HVT
TABLE 2.—Horizontal transmission of turkey herpesvirus (HVT) in three differ
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B
A
D
C
C.-W.L., inoculated donors (2 x 104 PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
(Controls, 5 hatchmates each of 3 lines) W.S.U.-V.S., inoculated donors (2 x 10" PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
8 days
4 days 8 weeks
8 days
8 weeks
3
4 days C.-M.T., inoculated donors 8 weeks (2 x 104 PFU) C Contact cagemates: W.S.U.-V.S. 8 days C.-W.L. C.-M.T. 4 days D (Controls, 4 hatchmates each 8 days of 3 lines) 4 days 'An experimental line of White Leghorns Cross (Cornell S x RPL Line 7). 2 Plaque-forming units. 3 Not tested. 4 Number of birds positive/number of birds examined. 5 A commercial line of White Leghorns. 6 A commercial line of meat-type chickens. 'A few chicks died of smothering within a week.
2
C.-W.L. C.-M.T. C.-M.T., inoculated donors (9.4 x 10" PFU) Contact cagemates: W.S.U.-V.S. C.-W.L. C.-M.T.
0/6 0/6 0/6 NT
0/6 0/6 0/3' NT
0/6 1/6 0/6 NT
NT
0/6 0/6 0/6 NT
0/6 0/6 NT
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114
B. R. CHO AND S. G. KENZY
DISCUSSION HVT spread readily to contact cagemates from W.S.U.-V.S. donor chickens inoculated with 2 x 104 PFU of HVT at 8 weeks of age, while the virus either did not spread or poorly spread when inoculated at 1 week of age with 9.2 x 103 and 9.4 x 104 PFU of HVT, respectively. However, in corresponding groups employing C.-W.L. and C.-M.T. birds as inoculated donors, there was no horizontal spread of HVT. This observation indicated that W.S.U.V.S. chickens were capable of shedding infectious HVT following virus inoculation, while C.-W.L. and C.-M.T. birds were not, and suggested the genetic difference among lines of chickens in the development a n d / o r shedding of infectious HVT following virus
inoculation. Development of infectious HVT in the feather follicle epithelium, by analogy with MDHV, have been reported in chickens (Zygraich et al., 1972) and in turkeys (Witter et al., 1972). It was interesting to note that W.S.U.-V.S. birds highly susceptible to MD could become shedders of HVT, while the less MD-susceptible C.-W.L. and C.-M.T. birds failed to shed HVT. It was not likely that the observed difference in shedding HVT resulted from dissimilarity among the three lines of chickens in the level of passive immunity against MDHV and/or HVT, since 1) the source flock of C.-W.L. as well as W.S.U.-V.S. had never been exposed to HVT, and maternal HVT precipitins detected in some of the W.S.U.-V.S. and C.-W.L. birds were probably due to cross reaction of HVT antigens with MDHV antibodies (Witter et al, 1970); 2) HVT and MDHV maternal antibodies were known to have little or no effect on infection of chicks by cellassociated HVT (Eidson et al., 1973; Petrascu et al., 1972); and 3) maternal HVT and MDHV antibodies were found to disappear by the third to fifth week after hatching (Witter et al., 1971; Sharma et al., 1972). The results of this study confirmed the previous observations (Cho et al., 1971, 1973) which had shown the age of donor chickens at the time of HVT inoculation and the dose of HVT given to donor birds to be important factors determining horizontal transmission of HVT among chickens. ACKNOWLEDGEMENT We thank Mr. W. R. Bryson and Mrs. D. Edwards for excellent technical assistance. REFERENCES Cho, B. R., and S. G. Kenzy, 1973. Horizontal transmission of turkey herpesvirus to chickens. 2. Some factors affecting transmission. Poultry Sci. 52: 608-613. Cho, B. R., S. G. Kenzy and S. A. Haider, 1971. Horizontal transmission of turkey herpesvirus to
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Trial 3. At 4 weeks post-contact, all of the contact cagemates tested were negative for viremia (HVT) or for HVT precipitins, except one of C.-W.L. cagemates of Group A (W.S.U.-V.S. donors) which was viremic without detectable antibodies. At 8 weeks post-contact, there was horizontal spread of HVT which occurred only in those cagemates of Group A but not of Groups B and C. In Group A, 3 of 5 W.S.U.V.S., one of 6 C.-W.L., and 3 of 6 C.-M.T. cagemates were viremic. One each of the viremic W.S.U.-V.S. and C.-W.L. cagemates was also positive for HVT precipitins. Donors of Group A were all viremic without detectable HVT precipitins. However, in Groups B and C (C.-W.L. and C.-M.T. donor birds, respectively), none of the contact cagemates was viremic or positive for HVT precipitins. In these two groups, donors were also nonviremic but one of Group B and 2 of Group C donors were positive for HVT precipitins. Non-exposed control birds (Group D) consisting of 4 hatchmates from each of the three lines were all free of HVT viremia and antibodies.
TRANSMISSION OF HERPESVIRUS
Sharma, J. M., and H. A. Stone, 1972. Genetic resistance to Marek's disease. Delineation of the response of genetically resistant chickens to Marek's disease virus infection. Avian Dis. 16: 894-906. Witter, R. L., K. Nazerian, H. G. Purchase and G. H. Burgoyne, 1970. Isolation from turkey of a cell-associated herpesvirus antigenically related to Marek's disease virus. Am. J. Vet. Res. 31: 525-538. Witter, R. L., K. Nazerian and J. J. Solomon, 1972. Studies in the in vivo replication of turkey herpesvirus. J. Nat. Cancer Inst. 49: 1121-1130. Witter, R. L., and J. J. Solomon, 1971. Epidemiology of a herpesvirus of turkeys: Possible sources and spread of infection in turkey flocks. Infect. Immunity 4: 356-361. Zygraich, N., and C. Huygelen, 1972. Inoculation of one-day-old chicks with different strains of turkey herpesvirus. II. Virus replication in tissues of inoculated animals. Avian Dis. 16: 793-798.
NEWS AND NOTES (Continued from page 90)
SHAVER NOTES During 1974, the Centennial Year of the Ontario Agricultural College, University of Guelph, Centennial Medals will be presented to 100 living individuals, other than present faculty or staff, who have made a significant contribution to the advancement of agriculture, and supported and assisted the various programs of the College. On June 12, during the Poultry Institute Conference held in London, Ontario, a Medal was presented to Donald McQ. Shaver. The citation read: "Donald McQueen Shaver, Chairman and Chief Executive Officer, Shaver Poultry Breeding Farms, Cambridge, Ontario, has developed one of the leading egg production type birds in the world. It is now distributed in some 60 countries. As a boy he bred laying chickens and, at the age of 15, entered these in the Canadian Egg Laying Contest held in Ottawa. His entry of White Leghorns won the contest. "He served with the Montreal Hussars Armored Regiment in World War II, and was discharged with the rank of Major.
"After the War he returned to his poultry operations and produced the World's Champion Layer, which produced 360 eggs in 365 days. He named her Hussar's Pride. Shaver Starcross 288, a hybrid layer developed in Canada, was first marketed in 1955 and was the recent winner of the Poultry Tribune Trophy. The winner of this Trophy is selected on the basis of highest income over feed and chick cost per pullet housed as computed by the U.S. Department of Agriculture in its two year summary of Random Sample Egg Production Tests. This was the fourth win in four years, and a seven-time win in nine years. "He received the Ontario Poultry Council Award of Merit in 1969. He has initiated a crossbreeding project with beef cattle. "Mr. Shaver included the underdeveloped countries in the international organization he developed to bring the benefits of Canadian technology to the World's less fortunate people. He recognized that it was necessary not only to supply a Canadian bird but that technological skills were also needed. The Company operates a successful training program to impart the
(Continued on page 118)
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chickens. 1. Preliminary observation. Poultry Sci. 50: 881-887. Cho, B. R., S. G. Kenzy and U. H. Kim, 1968. Atypical cells in the peripheral blood of chickens exposed to Marek's disease agent. Canad. J. Comp. Med. 32: 562-567. Eidson, C. S., S. H. Kleven and D. P. Anderson, 1973. Efficacy of cell-free and cell-associated herpesvirus of turkeys vaccines in progeny from vaccinated parental flocks. Am. J. Vet. Res. 34: 869-872. Patrascu, I. V., B. W. Calnek and M. W. Smith, 1972. Vaccination with lyophilized turkey herpesvirus (HVT): Minimum infective and protective doses. Avian Dis. 16: 86-93. Okazaki, W., H. G. Purchase and L. Noll, 1970. Effect of different conditions on precipitation in agar between Marek's disease antigen and antibody. Avian Dis. 14: 532-537.
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