- Email: [email protected]
Whither disease control in poultry?
Br. vel. J. (1988) . 144, 3 1 3
PERSONAL VIEWPOINT
WHITHER DISEASE CONTROL IN POULTRY?
Both are inter-related, and probably increasingly so with the trend towards larger sites . We must not forget this when new management techniques are developed . Water control in broiler breeders and nipple drinkers in broiler flocks have already produced problems of management . Separate sex feeding in the breeder flocks presents no disadvantages, the problem being to keep the cocks out of the hens' food! Where it is done well, cockerel lameness is decreased and hence fertility improved . Further sophisticated management developments will appear, not perhaps with care-reared broilers in this country but with `free range broilers' as a specialist market . These will run into all the problems experienced with free range laying flocks . Any disease adversely affects weight gain, egg production, feed conversions, mortality, carcase quality, rejection and downgrading . Sloppy management allows the introduction of many infectious diseases . When the infectious disease problems are negligible, site security and hygiene tend to become very slack. The massive problems caused by the widespread outbreaks of Newcastle Disease in the 1970s were soon forgotten . The salutory experience of subsequent pigeon paramyxo I, infectious laryngotracheitis (ILT) outbreaks and the outbreak of influenza in USA highlighted how rapidly situations can develop . The frightening situation caused by influenza A in the USA was to a large extent due to inadequate site security and hygiene . ILT is not a notifiable disease . It is easily spread by infected birds, contaminated clothing, equipment and Keys trays . I believe that any poultry keeper who is unlucky enough to have ILT should inform his neighbours, feed suppliers, hatchery and packing station . He should not try to hide it and put everyone else at risk . The pigeon paramyxo I incidents and Salmonella control emphasize the fact that disease precautions and hygiene have to start with the collection and storage of raw feed ingredients . Some of our feed compounding colleagues are not as `lily white' as they sometimes pretend to be . An integrated group's own feed lorries are just as capable of spreading disease amongst the companies' sites as are compounders' lorries . Consumers will, I am sure, insist on further reduction of Salmonella and Campylobacter contamination . The technique of competitive exclusion appears to have foundered . These enteric infections are so ubiquitous in nature that any control must depend upon a reduction of the numbers of organisms in the feed, the environment and birds in the breeding, growing and slaughtering operations, together with a more widespread appreciation of good kitchen hygiene routines . All aspects must be attacked ; concentrating on one aspect alone is virtually useless . The poultry industry will continue to be at risk from ill informed scare reports . This was highlighted recently in Sweden where broiler consumption dropped by nearly 30% in a matter of a few weeks following such articles in the popular press and media .
314
BRITISH VETERINARY JOURNAL, 144, 4
As an industry we must be aware of these problems, be prepared to face up to them and attempt to put the situation into the right perspective by educating people before similar scare tactics develop . This can be a difficult and delicate task . The basics of good disease control do not change . Site security, hygiene, good vaccination techniques and, when applicable, feeding of preventive medication for parasitic conditions will remain of paramount importance . We could see a change in coccidiosis control when the vaccines on trial come onto the market . When this happens we must not forget about necrotic enteritis that at present is held in check by the anticoccidials . These vaccines utilize precocious strains of all the seven significant species affecting the chicken . As a longer term project there is also a possibility of a non-living genetically engineered vaccine . Whether these developments will be cheaper than the present £5 .25 million pounds spent on anticoccidial drugs remains to be seen . I doubt it, even assuming that they are as effective . Their availability will please the `additive free lobby' . They are already being marketed from this angle . In the next decade we will see more and improved viral vaccines on the market, produced by genetic manipulation or other laboratory selection procedures . These should be more effective and have less stressful effects than those available today . It is time that the requirements for the licensing of vaccines, especially inactivated ones, as stipulated in the Medicines Act, should be reassessed . The present requirements of evidence of safety, potency and efficacy were accelerated by the thalidomide catastrophe and as such are more applicable to the human rather than the animal field . Many developing situations in poultry are a combination of problems that may feature one or more infections which by themselves are not significant but together are . In these cases it is very difficult, if not impossible to prove efficacy with each individual component . We must not forget the considerable progress that has been made in the last decade by the better use of available vaccines . There is no doubt that infectious bronchitis in broilers is now much more under control since the advent of day-old coarse spray vaccination . The amount of secondary E. coli septicaemias in broiler flocks is minimal compared to what it was in the late seventies . Unfortunately, however efficient vaccination techniques may be, variant strains of established pathogens continue to appear . There has been a lot of discussion about variant infectious bronchitis which I am sure will continue to cause us problems for many, many years . These variants keep changing . There are different ones in different parts of the country so I think it is extremely doubtful if we will in the foreseeable future ever have fully effective vaccines against them . Respiratory problems, drops in egg production, loss of egg colour and shell quality, outbreaks of yolk peritonitis, are all part of the clinical picture that may be associated with some variant infectious bronchitis challenges . Unfortunately it is very difficult to prove that they are responsible for these defects . In fact in many cases they are not responsible but some management fault is . It is all too easy to blame infectious bronchitis and not look closely at day-to-day procedures . There is evidence that the nephrotoxic strains of infectious bronchitis frequently found in Italy are spreading into France . We now hear about variant gumboro viruses in the United States that are not controlled by the normal gumboro vaccines . So far there is no evidence of these in this country . Having said that, we do, however, see problems with gumboro outbreaks occurring in birds on some sites from about 30 days of age, after their maternal
WHITHER DISEASE CONTROL IN POULTRY
315
antibodies have waned . These birds go off their food, drink a lot, create wet litter and obviously for a few days do not put on any weight . Usually they make up the weight before slaughter unless the challenge occurs only a few days prior to slaughter, when carcase quality and weights are disadvantaged . This is a case where the pattern of a disease has been changed by effective vaccination . The poultry industry has learned to fear gumboro because of its immunosuppressive powers . In the next few years we will hear a lot about another immunosuppressive virus-the chick anaemia agent (CAA) . On serological evidence it is very widespread in our breeders, broilers and layers . This is a parvovirus that is spread both horizontallybetween chicks-and vertically via the egg . It causes the well known blue wing and some stunting conditions in broilers, but can also cause poor response to vaccination . This may explain some of the poor responses seen in some birds in some breeder flocks to Newcastle Disease, infectious bronchitis and Marek's vaccination and some uncontrollable non-specific conditions in younger birds . We must not fall into the trap of blaming everything on CAA . The level of mortality in the broiler house is higher than one would like . This is due mainly to non-infectious problems such as chick quality, infectious stunting syndrome, fatty liver kidney syndrome, ascites, sudden death syndrome and leg disorders . The last four are probably physiological problems whose incidence has been accentuated by genetic selection for rapid growth . The last three are difficult to control without holding back this growth potential . We may see more conditions like these in the future with further increases in growth and improvements in nutrition . There is already quite a lot of evidence that broiler breeders are becoming more predisposed to acquiring tendon or ligament failure (S .R .I . Duff-P .R.C .) . I don't envy the geneticists who are continually open to developing genetic predispositions that suddenly appear . The demand for more broilers seen over the last few years has encouraged some companies to put more birds in the broiler houses without upgrading the amount of feeding space, drinkers and ventilation . In other words an overcrowding situation has been created which in many instances is the main cause of increased broiler mortality . Great improvements have been made in the methods of catching, transporting and unloading broilers with the advent of various modular systems . There is still room for more development and one hopes that this will continue . Research facilities have been retracted over the past few years and may go even further with the Centres reduced to such an extent that a severe deficiency could be created-so much so that if we suddenly encounter a new serious disease problem there may be nowhere or nobody to investigate fully . I do not believe that the setting up of 2-year research contracts by the industry is the best way out . These take a long time to implement . We have seen recently how the research scientists appointed leave part way through the 2 years to go to a permanent post . One cannot blame them when there are fewer and fewer research facilities available to them . Unfortunately the net result is that the contracted work is held up whilst another person is found and trained . I believe that the industry will have to come together and help fund an ongoing research establishment on a continuing basis . It does not need to be heavily staffed if attached to an already established unit ; it could call upon the expertise of the other staff when necessary . J . C . STUART,
Norwich
PERSONAL VIEWPOINT
WHITHER DISEASE CONTROL IN POULTRY?
Both are inter-related, and probably increasingly so with the trend towards larger sites . We must not forget this when new management techniques are developed . Water control in broiler breeders and nipple drinkers in broiler flocks have already produced problems of management . Separate sex feeding in the breeder flocks presents no disadvantages, the problem being to keep the cocks out of the hens' food! Where it is done well, cockerel lameness is decreased and hence fertility improved . Further sophisticated management developments will appear, not perhaps with care-reared broilers in this country but with `free range broilers' as a specialist market . These will run into all the problems experienced with free range laying flocks . Any disease adversely affects weight gain, egg production, feed conversions, mortality, carcase quality, rejection and downgrading . Sloppy management allows the introduction of many infectious diseases . When the infectious disease problems are negligible, site security and hygiene tend to become very slack. The massive problems caused by the widespread outbreaks of Newcastle Disease in the 1970s were soon forgotten . The salutory experience of subsequent pigeon paramyxo I, infectious laryngotracheitis (ILT) outbreaks and the outbreak of influenza in USA highlighted how rapidly situations can develop . The frightening situation caused by influenza A in the USA was to a large extent due to inadequate site security and hygiene . ILT is not a notifiable disease . It is easily spread by infected birds, contaminated clothing, equipment and Keys trays . I believe that any poultry keeper who is unlucky enough to have ILT should inform his neighbours, feed suppliers, hatchery and packing station . He should not try to hide it and put everyone else at risk . The pigeon paramyxo I incidents and Salmonella control emphasize the fact that disease precautions and hygiene have to start with the collection and storage of raw feed ingredients . Some of our feed compounding colleagues are not as `lily white' as they sometimes pretend to be . An integrated group's own feed lorries are just as capable of spreading disease amongst the companies' sites as are compounders' lorries . Consumers will, I am sure, insist on further reduction of Salmonella and Campylobacter contamination . The technique of competitive exclusion appears to have foundered . These enteric infections are so ubiquitous in nature that any control must depend upon a reduction of the numbers of organisms in the feed, the environment and birds in the breeding, growing and slaughtering operations, together with a more widespread appreciation of good kitchen hygiene routines . All aspects must be attacked ; concentrating on one aspect alone is virtually useless . The poultry industry will continue to be at risk from ill informed scare reports . This was highlighted recently in Sweden where broiler consumption dropped by nearly 30% in a matter of a few weeks following such articles in the popular press and media .
314
BRITISH VETERINARY JOURNAL, 144, 4
As an industry we must be aware of these problems, be prepared to face up to them and attempt to put the situation into the right perspective by educating people before similar scare tactics develop . This can be a difficult and delicate task . The basics of good disease control do not change . Site security, hygiene, good vaccination techniques and, when applicable, feeding of preventive medication for parasitic conditions will remain of paramount importance . We could see a change in coccidiosis control when the vaccines on trial come onto the market . When this happens we must not forget about necrotic enteritis that at present is held in check by the anticoccidials . These vaccines utilize precocious strains of all the seven significant species affecting the chicken . As a longer term project there is also a possibility of a non-living genetically engineered vaccine . Whether these developments will be cheaper than the present £5 .25 million pounds spent on anticoccidial drugs remains to be seen . I doubt it, even assuming that they are as effective . Their availability will please the `additive free lobby' . They are already being marketed from this angle . In the next decade we will see more and improved viral vaccines on the market, produced by genetic manipulation or other laboratory selection procedures . These should be more effective and have less stressful effects than those available today . It is time that the requirements for the licensing of vaccines, especially inactivated ones, as stipulated in the Medicines Act, should be reassessed . The present requirements of evidence of safety, potency and efficacy were accelerated by the thalidomide catastrophe and as such are more applicable to the human rather than the animal field . Many developing situations in poultry are a combination of problems that may feature one or more infections which by themselves are not significant but together are . In these cases it is very difficult, if not impossible to prove efficacy with each individual component . We must not forget the considerable progress that has been made in the last decade by the better use of available vaccines . There is no doubt that infectious bronchitis in broilers is now much more under control since the advent of day-old coarse spray vaccination . The amount of secondary E. coli septicaemias in broiler flocks is minimal compared to what it was in the late seventies . Unfortunately, however efficient vaccination techniques may be, variant strains of established pathogens continue to appear . There has been a lot of discussion about variant infectious bronchitis which I am sure will continue to cause us problems for many, many years . These variants keep changing . There are different ones in different parts of the country so I think it is extremely doubtful if we will in the foreseeable future ever have fully effective vaccines against them . Respiratory problems, drops in egg production, loss of egg colour and shell quality, outbreaks of yolk peritonitis, are all part of the clinical picture that may be associated with some variant infectious bronchitis challenges . Unfortunately it is very difficult to prove that they are responsible for these defects . In fact in many cases they are not responsible but some management fault is . It is all too easy to blame infectious bronchitis and not look closely at day-to-day procedures . There is evidence that the nephrotoxic strains of infectious bronchitis frequently found in Italy are spreading into France . We now hear about variant gumboro viruses in the United States that are not controlled by the normal gumboro vaccines . So far there is no evidence of these in this country . Having said that, we do, however, see problems with gumboro outbreaks occurring in birds on some sites from about 30 days of age, after their maternal
WHITHER DISEASE CONTROL IN POULTRY
315
antibodies have waned . These birds go off their food, drink a lot, create wet litter and obviously for a few days do not put on any weight . Usually they make up the weight before slaughter unless the challenge occurs only a few days prior to slaughter, when carcase quality and weights are disadvantaged . This is a case where the pattern of a disease has been changed by effective vaccination . The poultry industry has learned to fear gumboro because of its immunosuppressive powers . In the next few years we will hear a lot about another immunosuppressive virus-the chick anaemia agent (CAA) . On serological evidence it is very widespread in our breeders, broilers and layers . This is a parvovirus that is spread both horizontallybetween chicks-and vertically via the egg . It causes the well known blue wing and some stunting conditions in broilers, but can also cause poor response to vaccination . This may explain some of the poor responses seen in some birds in some breeder flocks to Newcastle Disease, infectious bronchitis and Marek's vaccination and some uncontrollable non-specific conditions in younger birds . We must not fall into the trap of blaming everything on CAA . The level of mortality in the broiler house is higher than one would like . This is due mainly to non-infectious problems such as chick quality, infectious stunting syndrome, fatty liver kidney syndrome, ascites, sudden death syndrome and leg disorders . The last four are probably physiological problems whose incidence has been accentuated by genetic selection for rapid growth . The last three are difficult to control without holding back this growth potential . We may see more conditions like these in the future with further increases in growth and improvements in nutrition . There is already quite a lot of evidence that broiler breeders are becoming more predisposed to acquiring tendon or ligament failure (S .R .I . Duff-P .R.C .) . I don't envy the geneticists who are continually open to developing genetic predispositions that suddenly appear . The demand for more broilers seen over the last few years has encouraged some companies to put more birds in the broiler houses without upgrading the amount of feeding space, drinkers and ventilation . In other words an overcrowding situation has been created which in many instances is the main cause of increased broiler mortality . Great improvements have been made in the methods of catching, transporting and unloading broilers with the advent of various modular systems . There is still room for more development and one hopes that this will continue . Research facilities have been retracted over the past few years and may go even further with the Centres reduced to such an extent that a severe deficiency could be created-so much so that if we suddenly encounter a new serious disease problem there may be nowhere or nobody to investigate fully . I do not believe that the setting up of 2-year research contracts by the industry is the best way out . These take a long time to implement . We have seen recently how the research scientists appointed leave part way through the 2 years to go to a permanent post . One cannot blame them when there are fewer and fewer research facilities available to them . Unfortunately the net result is that the contracted work is held up whilst another person is found and trained . I believe that the industry will have to come together and help fund an ongoing research establishment on a continuing basis . It does not need to be heavily staffed if attached to an already established unit ; it could call upon the expertise of the other staff when necessary . J . C . STUART,
Norwich