The Effect of Social Isolation on Resistance to Some Infectious Diseases

Transcription

1 514 A. T. LEIGHTON, JR. AND L. M. POTTER Marsden, S. J., and L. M. Lucas, Effect of short-day or low-intensity light treatments on reproduction of fall-hatched turkeys in two environments. Poultry Sci. 43: Marsden, S. J., L. M. Lucas and S. P. Wilson, The influence of daylength and environment on reproduction, broodiness and mortality of turkeys. Poultry Sci. 45: McCartney, M. G., V. L. Sanger, K. I. Brown and V. D. Chamberlin, Photoperiodism as a factor in the reproduction of the turkey. Poultry Sci. 40: Milby, T. T., and K. B. Thompson, Some observations on fertility in turkeys. Poultry Sci. 24: Nakajo, S., and K. Imai, Gonadotropin content in the cephalic and the caudal lobe of the anterior pituitary in laying, non-laying and broody hens. Poultry Sci. 40: Ogasawara, F. X., W. O. Wilson and V. S. Asmundson, The effect of restricting light during the adolescent period on reproductive performance in turkeys subsequently exposed to 12, 14 and 20 hour day. Poultry Sci. 41: TN PREVIOUS experiments (Gross and -* Siegel, 1965; and Gross and Colmano, 1967) it was shown that cockerels which were moved daily among unfamiliar individuals were much more resistant to Escherichia coli infection than cockerels kept in groups of 6 for 4 weeks prior to challenge. It was also shown (Gross and Colmano, 1967) that plasma corticosterone levels could identify highly resistant or highly susceptible birds. No effect of social stress on Mycoplasma gallisepticum infection was reported (Gross and Siegel, This work was supported in part by Grant A from the National Institutes of Health. Phillips, R. E., Comparative gonadotropic potency of unfractionated extracts of poultry pituitaries. Poultry Sci. 21: Shoffner, R. N., E. R. Polley, R. E. Burger and E. L. Johnson, Light regulation in turkey management. 2. Female reproductive performance. Poultry Sci. 41: Siegel, P. B., and C. E. Howes, Age at lighting and egg production of Bronze and Large White turkeys. Virginia Agr. Exp. Sta. Bui Smyth, J. R., Jr., and A. T. Leighton, Jr., A study of certain factors affecting fertility in the turkey. Poultry Sci. 32: Wilson, W. O., F. X. Ogasawara and V. S. Asmundson, Artificial control of egg production by photoperiods. Poultry Sci. 41: Wilson, W. O., F. X. Ogasawara and A. E. Woodard, Increasing egg production in winter hatched turkeys by a restricted light treatment. Poultry Sci. 46: Wolfson, A., Animal photoperiodism: Photophysiology. Vol. II pp Academic Press, N. Y. and London. The Effect of Social Isolation on Resistance to Some Infectious Diseases W. B. GROSS AND G. COLMANO Veterinary Science Department, Virginia Polytechnic Institute, Blacksburg, Virginia (Received for publication August 19, 1968) 1965). Roberts and McDaniel (1967) associated mycoplasmal bacteremia with fighting that occurred following the mixing of cockerels which had been raised separately until they were placed together at the time of inoculation. Brown (1968) reported that turkeys selected for low plasma corticosterone response to cold stress were more resistant to Mycoplasma meleagridis infection than birds selected for high plasma corticosterone response. The present report describes the effect of social interaction in cockerels on resistance to infection with Escherichia coli, Staphylococcus aureus, Mycoplasma gallisepticum and Newcastle disease virus.

2 RESISTANCE TO DISEASE 515 MATERIALS AND METHODS Eight Horsfall-Bauer type units containing 8 cu. ft. each were modified by installing two plywood partitions so that a center compartment of approximately 8"X24" and 2 side compartments approximately 7"X24" were created. The partitions had large hardware cloth windows that could be made solid with plywood inserts. During most of the experiments half of the cages had solid partitions and half had mesh partitions. In these experiments, 2 cockerels were placed in the center compartment, one cockerel in each of the side compartments, 4 weeks before inoculation. They were compared with cockerels in 2 unmodified units containing 6 cockerels each. The White Leghorn cockerels used in those experiments were obtained from the Veterinary Science Department S.P.F. flock and were hatched, brooded and reared in an isolation building. Cultures of Escherichia coli, serotype 2-1, were grown in tryptose broth for 24 hours before use. They were administered by the air sac route (left posterior thoracic air sac) in doses of 10 8 cells per bird or by the aerosol route with a DeVilbiss #40 nebulizer at about 10 9 cells per 8 cubic foot cage. Examination for lesions was made 48 hours after inoculation. Air sacs were scored for thickness and exudate on a scale from 0 to 4 with 0 being for birds with no visible lesions and 4 being for the most severe lesions observed in previous experiments. The staphylococcal challenge consisted of equal portions of broth cultures of 2 strains of Staphylococcus aureus which had been selected for high pathogenicity and mortality because of septicemia. The challenge was 0.2 ml. of inoculum containing approximately 10 9 bacteria administered intravenously to each bird. Mycoplasma gallisepticum was passaged in the air sacs of Mycoplasma-free chickens and stored as ground tissue (10%) in broth at 40 C. It was administered via the air sac route. Newcastle disease virus inoculum was prepared by growing the California strain in embryonating eggs and collecting the virus-containing allantoic fluid. Approximately 10 4 ELD50 of virus was inoculated via the intramuscular route when used as a challenge.* EXPERIMENTAL PROCEDURES AND RESULTS In a series of 3 experiments, one half of the birds were kept in cages with a solid partition and the other half were kept in cages which had partitions with large hardware cloth windows. The birds in the side compartments remained there for the duration of the experiments. On each of 2 days before E. coli air sac challenge the 2 birds in the center compartment were moved separately to similar cages according to a plan which precluded contact with previously encountered birds. The incidence of pericarditis at 48 hours after inoculation in birds from partitioned cages was compared with that of 2 cages of controls (6 birds per 8 cubic foot cage) which were similarly challenged. The results are recorded in Table 1. Pericarditis occurred in 47% of the controls and 71% of the birds in single bird cages. The results were not influenced by birds being able to see other birds fighting or not. Among the paired birds which were moved before challenge, less susceptibility occurred in those which could not see the isolated birds (29%) than in those that could see the birds in the side compartments (54%). In a similar experiment in which the paired birds were not moved (Table 2), all of the experimental groups * The authors wish to thank Dr. R. T. DuBose for preparing the Newcastle disease virus.

3 516 W. B. GROSS AND G. COLMANO TABLE 1. The effect of social interaction and the type of cage partition on the incidence of pericarditis following Escherichia coli air sac challenge Solid partitions Mesh partitions Exp 1 Exp 2 Exp 3 T* Exp 1 Exp 2 Exp 3 T Moved 2 per cage 4/8 2/8 1/8 7/24(29%) 6/8 5/8 2/8 13/24(54%) Not moved 1 per cage 7/8 5/8 5/8 17/24(71%) 7/8 7/8 4/8 18/24(75%) Controls 6 per cage 6/12 5/12 6/12 17/36(47%) *T= total. were similar and were much more susceptible than the controls raised in groups of 6 birds per cage. This is in agreement with previously reported results (Gross and Colmano, 1967). In another similar experiment all of the partitions were made solid and 4 additional cages each containing 6 similar unfamiliar cockerels were prepared 3 days before inoculation. The staphylococcus inoculum resulted in an acute septicemia and the mortality which occurred during the first 4 days post inoculation was recorded. The results (Table 3) indicate that only the highest stressed group was able to resist infection. These results are in agreement with the previous reports employing an E. coli challenge (Gross and Colmano, 1967). Mycoplasma gallisepticum was inoculated into the left posterior thoracic air sac of cockerels after being maintained in units with solid partitions for 30 days. Paired birds were not moved before chal- TABLE 2. The effect of raising birds singly or in pairs and the type of cage partitions on the incidence of pericarditis following Escherichia coli air sac challenge Solid partitions Mesh partitions 2 per cage 5/8 5/8 1 per cage 5/8 6/8 controls (6 per cage) 3/12 25% lenge. Lesions were scored for the posterior thoracic and lesser abdominal air sacs as a group and for the greater abdominal air sac 14 days after inoculation. Scores were made on a scale of from 0-3 with 0 being no lesions and 3 representing severe thickening and exudate. Right and left scores were recorded separately. The scores for each group of birds were averaged. The results which are recorded in Table 4 suggest that increased social interaction results in increased susceptibility to Mycoplasma infection in the inoculated air sac and increased spread of lesions to other air sacs. Birds kept singly or in pairs had similar resistance. Mycoplasma gallisepticum was inoculated into the left posterior thoracic air sac of a group of birds maintained in units with solid partitions. Fourteen days later they were challenged with E. coli by the aerosol route. During 4 days prior to this challenge, the birds in the center chambers TABLE 3. The effect of social interaction on mortality following Staphylococcus aureus intravenous challenge 6 unfamiliar cockerels placed in cages 3 days before challenge 2/24 8% 2 per cage for 30 days (moved each of 3 days before challenge) 13/16 81% 6 per cage 30 days before challenge 11/12 92% 1 per cage for 30 days before challenge 15/16 94%

4 RESISTANCE TO DISEASE 517 were moved daily as individuals according to a plan which precluded contact with previously encountered birds. These birds were compared with 2 cages of 6 similar birds. The results which appear in Table 5 suggest that the least stressed cockerels (in the single bird cages) were the most resistant to the E. coli aerosol challenge. The short term stressing of the moved birds resulted in a considerably increased susceptibility to E. coli over that of the birds in single cages. In another similar experiment 32, 5- week-old cockerels were placed in isolation cages for 3 weeks. They were inoculated via the air sac route with Mycoplasma gallisepticum. At that time 10 of the birds were removed from the isolation TABLE 4. The effect of social interaction on susceptibility to Mycoplasma gallisepticum challenge 1 6 per cage 2 per cage 1 per cage Average air sac scores 2 Left anterior*' Left Right (inoculated)? * antenor Right P»t«ior Average uninoculated air sacs Challenge 30 days after birds were placed in cages. 2 Recorded 14 days after inoculation. 8 Anterior =posterior thoracic on sac and lesser abdominal air sac. 4 Posterior =greater abdominal air sac. Source of Variation Analysis of Variance mean square Number of birds per cage *' Air Sacs *' left vs. right *' Interaction *' Number of birds per cage vs air sac scores Error ** Significant at 1% level. Kramer's modification of Duncan 's separation of mean test Birds per cage R. Ant Means over same line are similar Air Sacs ** R. Post L. Post L.. Ant TABLE 5. The effect of social interaction and Mycoplasma gallisepticum infection on the incidence of pericarditis following aerosol exposure to Escherichia coli Controls 6 per cage 4 weeks 2 per cage, 4 weeks (moved for 4 days before E. Coli exposure) 1 per cage for 4 weeks DeaH Peri " Ne S a " 07 p Uea<1 carditis tive /o F P =dead or with pericarditis. x' = significant at the 1% level. M. gallisepticum 14 days before E. coli aerosol exposure. cages and placed in 4, 8-cubic-foot Horsfall-Bauer modified cages where they were moved among unfamiliar individuals. During the 14-16th days after mycoplasma exposure 10 additional birds were removed from the isolation cages and moved among the original group of 10 birds. All of the birds were exposed to E. coli administered via the aerosol route 16 days after mycoplasma exposure. Four days after E. coli exposure all birds were examined for lesions of pericarditis. The results which are recorded in Table 6 were similar to those of the previous experiment. In a social stress experiment conducted TABLE 6. The effect of social interaction and Mycoplasma gallisepticum infection 1 on the incidence of pericarditis following aerosol exposure to Escherichia coli 2 Moved every other day 3 for 14 davs before E. coli aerosol Moved days before E. coli aerosol 1 per cage 16 days No pericarditis Pericarditis 4 7 (70%) 3 (30%) 0 ( 0%) 1 Mycoplasma gallisepticum in ground tissue administered into the left posterior thoracic air sac on the 1st day. 2 Broth culture of E. coli serotype 2-1 on day Prior to M. gallisepticum exposure all birds in cages with 1 or 2 birds for 4 weeks. 4 Examined for lesions 4 days after E. coli aerosol exposure. X 2 = significant at 1% level. X 2 = sig. at the 0.1% level for difference between high and low stress birds in tables 5 and 6.

5 518 W. B. GROSS AND G. COLMANO TABLE 7. The effect of social interaction on mortality following exposure to Newcastle disease virus Mortality Visitors (moved among residents for 2 days before challenge) 7/12 58% Residents (groups of 4 birds among which visitors were moved) 9/24 37% Controls, 6 per cage for 4 weeks 0/12 0% X 2 =8.09 significant at 1% level for difference between highest and lowest stressed groups. similarly to those of Gross and Siegel (1965), 6 groups of 2 birds (visitors) were moved as individuals daily among 6 groups of 4 birds each (residents) for 2 days according to a plan which precluded contact with previously encountered birds. These were compared with 2 cages of 6 birds each (controls) that were not moved. All of the birds were challenged intramuscularly with ELD50IO 4 of the California strain of Newcastle disease virus. Mortality during the first 48 hours post inoculation (Table 7) indicated a much higher susceptibility to Newcastle disease in groups subjected to more social stress than in the control groups. In another similar experiment 6 pairs of 6 week-old cockerels were placed in 6 8- cubic-foot modified Horsfall-Bauer cages. Twelve additional cockerels were placed in single bird cages. After 2\ weeks the 12 birds in the single bird cages were stressed TABLE 8. The effect of social interaction on mortality following exposure to Newcastle disease virus Survived Died High stress (moved among unfamiliar individuals every third day for (92%) days) Low stress (2 birds per cage for 26 days) S 7 (58%) x 2 = 3.96 sig. at the 5% level. x 2 = significant at the 0.1% level for difference in mortality between the high and low stressed birds in Tables 7 and 8. by placing them among unfamiliar individuals every 3rd day for 9 days. Both the high and low stress groups were challenged via the intramuscular route with Newcastle disease virus diluted to contain an ELD50 of Both the greatest and least stressed birds in this experiment were less stressed than greatest and least stressed birds in the previous Newcastle disease experiment. Post challenge mortality was recorded and is reported in Table 8. DISCUSSION The degree of social interaction appears to have a major effect on the susceptibility or resistance of individual cockerels to a wide variety of infectious agents. The mechanism of action is unknown although Gross and Colmano (1967) found that corticosterone and ACTH play some part in increased resistance. None of the birds was visibly injured by the experimental social stress and in previous experiments there were no differences in weight gain among the various stress groups. Resistance to bacteria was associated with a high degree of social interaction while resistance to viruses and mycoplasma was associated with a low degree of social interaction. A previous report (Gross and Siegel, 1967) indicated that stress had little effect on mycoplasma. Data presented here suggests that all of the groups in the previous report received too much social stress to demonstrate major resistance to mycoplasma. Two methods for evaluating the effect of social interaction on Mycoplasma gallisepticum infection were employed. The first demonstrated that the lesion at the site of inoculation was much more severe in the high stress than in the low stress birds and that the spread of lesions was much more severe among the high stressed birds. The second method demonstrated

6 RESISTANCE TO DISEASE 519 that mycoplasma infected birds under high stress were much more susceptible to E. coli in an aerosol than similar birds under low stress. According to Fabricant and Levine (1962) air sac disease results from E. coli infection of chickens previously infected with Mycoplasma galliseplicum. Chickens were found by Dawson and Siegel (1967) to begin encounters for dominance at about 2 weeks of age. These encounters increased in frequency until about 8 weeks of age after which they decreased in frequency. According to Harry (1964) the rise in incidence of "air sac disease" occurs about 2 weeks after the increase of encounters for dominance. Air sac disease decreased in incidence when the encounters for dominance decreased. These observations suggest that the social stress created by the establishment of peck orders among growing birds is a factor in the development of "air sac disease." When the local respiratory tract susceptibility to E. coli was increasing in Mycoplasma galliseplicum infected birds due to social stress, this same stress was resulting in increased resistance to systemic E. coli infection. The changes in Mycoplasma galliseplicum infected air sacs associated with increased susceptibility to E. coli have not been described although Gross (1961) demonstrated that susceptibility does not begin until between 8 and 16 days after mycoplasma inoculation. A neurogenic Newcastle disease virus challenge was used to demonstrate the effect of social interaction on a virus infection because the effect could be observed quickly and in absolute terms of mortality. Social interaction might also have an effect on the results of other virus challenges. Experimental procedures which affect social grouping of chickens could easily influence their susceptibility to infectious agents. This could be especially important in treatment and immunization trials and in infectivity determination. A common practice is to put birds in their experimental cages according to weight, which would tend to mix unfamiliar birds; administer the experimental drug the next day and the infectious agent on the third day. This would be an excellent way to produce increased resistance to bacterial diseases and increased susceptibility to viruses and mycoplasma. Placing the birds in their cages at least a week before the administration of the infectious agents would greatly decrease the problem. It appears, where infectivity of material containing unidentified agents was being determined, that a group of birds with high and a group of birds with low degrees of social interaction should be employed. Control of social interaction could be used to produce birds which would be susceptible to bacteria or to mycoplasma and viruses. It is interesting that the birds in experiment 1 which were moved and could not see the birds on either side of their cage had much more resistance than those which could see the birds in the single cages. Perhaps it was less stressful to see other birds which were not social competitors. Apparently it made little difference to the birds in the side cages (single birds) whether they could see the social competition in the center cages or not. It should be apparent that the cockerels which were alone in solid partitioned compartments were not completely isolated because they could hear other birds. SUMMARY The degree of social interaction in 8- week-old White Leghorn cockerels markedly affected their susceptibility or resistance to infectious agents. A high degree of social interaction resulted in increased

7 520 W. B. GROSS AND G. COLMANO resistance to Escherichia coli and Staphylococcus aureus infection and decreased resistance to Mycoplasma gallisepticum and Newcastle disease virus infection. A low degree of social interaction had the opposite effect. REFERENCES Brown, K. I., Environmentally imposed stress. Environmental Control in Poultry Production. Olivier and Boyd Limited, Edinburgh, Dawson, J. S., and P. B. Siegel, Behaviour patterns of chickens to ten weeks of age. Poultry Sci. 46: Fabricant, J., and P. P. Levine, Experimental production of complicated chronic respiratory TTARSCHFIELD (1965) has reviewed -*- A the literature with reference to immunization against fowl cholera. His only reference to a living vaccine was Pasteur's attenuated fowl cholera vaccine. Hayden (1914) produced immunity against Pasteurella multocida in rabbits, chickens, and pigeons by injecting an avirulent live P. multocida vaccine. Sinha et al. (1957) found that a living avirulent mouse strain of P. multocida was a better immunizing agent than heat-killed strains. Ose et al. * B. W. Bierer is Professor of Poultry Science, Clemson University Department of Poultry Science. W. F. Scott is General Manager of Nicholas Turkey Breeding Farm at Pageland, South Carolina. 1 Published with approval of Director of South Carolina Agr. Exp. Sta. as Technical Contribution No disease infection (air sac disease). Avian Dis. 6: Gross, W. B., and H. S. Siegel, The effect of social stress on resistance to infection with Escherichia coli or Mycoplasma gallisepticum. Poultry Sci. 44: Gross, W. B., and G. Colmano, Further studies on the effects of social stress on the resistance to infection with Escherichia coli. Poultry Sci. 46: Gross, W. B., The development of air sac disease. Avian Dis. 5: Harry, E. G., A study of 119 outbreaks of colisepticemia in broiler flocks. Veterinary Record, 76: Roberts, D. H., and J. W. McDaniel, Mechanism of egg transmission of Mycoplasma gallisepticum. J. Comp. Path. 77: Comparison of Attenuated Live Pasteurella multocida Vaccine Given in the Drinking Water Every Two Weeks to an Injected Oil-Base Bacterin Administered to Turkeys 1 B. W. BIERER* AND W. F. SCOTT South Carolina Agricultural Experiment Station, Clemson, South Carolina (Received for publication August 19, 1968) (1963) reported on the use of an avirulent oral live erysipelas vaccine for use in swine; this type vaccine is presently produced commercially. Bain (1963), referring to pasteurellosis in cattle, has suggested that with improved methods of technology, living attenuated vaccines may become the main method of prophylaxsis in the future. Heddleston and Rebers (1968) have reported that active immunity was induced in chickens and turkeys by oral administration of a killed P. multocida vaccine. Bierer and Eleazer (1968) found that continuous use of a living attenuated P. multocida vaccine in the drinking water protected turkeys against exposure to a pathogenic strain by the drinking water route. The use of continuous drinking water