- Email: [email protected]
(4) Sweden
CONTROL OF POULTRY DISEASE
133
diseases. It is not desirable that the control of poultry disease should be undertaken by poultry breeders themselves or by lay advisers to the industry.
(D) General state measures In addition to endeavours by the state to control the different poultry diseases, there are general official measures which are carried out for the prevention of the spread of infectious poultry diseases. Poultry exhibitions and poultry markets are supervised by the staff of the state veterinary service and there are certain regulations which must be carried out, for example the vaccination against Newcastle disease. There is also in preparation a law for the construction of poultry slaughter houses and the carrying out of poultry meat inspection, as already practised in some countries. REFERENCE TRAUB,
E. (1943). Berl. Munch., tieriirz tl. Wschr., 56, 39.
(4) SWEDEN By N. O. LINDGREN State Veterinary Medical Institute, Stockholm Legislative control In accordance with the law for the control of infectious diseases of domestic animals (1935), fowl plague and fowl cholera are notifiable poultry diseases in Sweden. In 1939 infectious laryngotracheitis was added to these two. Measures according to this law were applied in 1947 when Newcastle disease, in the peracute form, appeared for the first time in Sweden as a few isolated, primary outbreaks due to feeding of small flocks with offal from imported frozen table poultry. The disease was first diagnosed as fowl plague but when it was subsequently confirmed by laboratory investigations as Newcastle disease the list of notifiable poultry diseases was extended to apply to "fowl plague-like diseases". Since the eradication of the disease was successfully brought about by the slaughter policy, only a few new sporadic outbreaks of the same kind have occurred, all primary and mainly due to importation of frozen poultry products such as table chickens, partridges and turkeys, mostly from Hungary and/or the Netherlands. The last outbreak occurred in 1956 and as a result a law was introduced prohibiting the importation of all but eviscerated table poultry or, alternatively, the sale and distribution of such products within the country. Pullorum disease History. In an account of the control of avian disease in Sweden, pullorum disease deserves special mention. In 1927 the disease was first recorded in a report from the Royal Medical Board- then the administrative body for veterinary legislation- and the following year it was declared as prevalent in the country. Three years later the disease was controlled by legislation. The
134
BRITISH VETERINARY JOURNAL, 119, 3
regulations were augmented in 1933 when the disease was regarded as a notifiable disease subject to strict control measures, and it remained so until the end of the 1940s. These facts encouraged owners of breeding flocks to carry out pullorum disease control measures by means of regular blood testing and this was shown by the steady increase in the number of serological tests (tube test) for Salmonella pullorum which were carried out at the State Veterinary Medical Institute. From a total of only 4,000 tests in 1939 these examinations reached a peak of 293,693 in 1948, of which 4,837 or 1·6 per cent were positive. On the other hand the strict obligatory measures enforced upon the farmers when the disease was suspected or diagnosed tended to render the control programme unpopular. Doubtless this led to concealment of the existence of outbreaks of the disease and hindered successful control of the disease. Present control oj pullorum disease. Such was the situation when in 1950 a new law was passed regulating the control of pullorum disease. All breeding flocks may now participate in a control programme; the regulations for this are designed by the state and they aim at the total eradication of the disease. Flocks which show positive reactors at two subsequent blood tests carried out at a six-month interval are given an official certificate stating that they are free from pullorum disease. Regular retesting is carried out yearly or every second or third year. From the start this programme was not considered by the veterinary authorities to be an ideal solution to the problem of pullorum disease control. Firstly, the scheme is restricted to breeding flocks and thus imposes no control of the disease in commercial laying flocks, and secondly, since participation is voluntary, it is possible for those breeders who have not the welfare of the industry at heart to allow the disease to flourish in their flocks. However, some compulsion can be exerted when the disease is diagnosed in a flock which, for example, by its geographical position constitutes a threat to neighbouring flocks. This regulation has not been used often during the ten years during which the programme has been in existence. Despite these disadvantages the control programme has had some success, especially during the first few years of its existence. In 1950 the owners of 1,034 flocks, comprising 518,929 birds, volunteered to join the scheme and in the years 1952-55 the number of participant flocks remained steady at around 1,200, which is approximately the total number of breeding flocks in the country. The number of birds within these flocks has been slightly over 700,000 and corresponds to about 10 per cent of the present total fowl population of Sweden. The progress of the work is illustrated by the fact that the percentage of officially declared pullorum-free flocks has increased from 42'3 in 1950 to 92'9 in 196 I. During the same period the percentage of infected flocks has been reduced from 8'1 in 1950 to 1'1 in 1961. The apparent discrepancy in these figures is due to the fact that there are always some flocks which, though not having any reactors, are on a "waiting list" for the official pullorumfree certificate. Future control. Progress in the eradication of pullorum disease, if studied
CONTROL OF POULTRY DISEASE
135
closely, shows a regression from the second half of the 1950S onwards. This is mainly due to the fact that some flocks were voluntarily withdrawn from the scheme and others were excluded from it for different reasons. Even if the majority of these flocks are still pullorum-free it is unsatisfactory not to have all breeding flocks under constant supervision. Results of this lack of supervision are now beginning to show by the appearance of outbreaks of pullorum disease in replacement or laying stock which can be traced back to such renegade breeding flocks. Therefore in Sweden the time is now thought to be opportune for the original plan of 1950 to be brought into force and for the voluntary control programme to be changed to a compulsory one, including all breeding flocks, and making freedom from pullorum disease a condition for the hatching and selling of all types of replacement stock. A law along these lines is ready to be adopted by the Swedish parliament in 1963; it was originally hoped that it would be passed in 1962.
Control of salmonellosis In 1950 when the present regulations for pullorum disease control were adopted it was believed not only that the change to a compulsory programme would sooner or later prove inevitable, but that efforts to control other salmonella infections of poultry would be included in the scheme. In Sweden, as in most other countries, such infections have shown an increasing incidence during the last 10-15 years. Some serotypes, such as Salmonella ryphimurium, Salmonella oranienburg, Salmonella montevideo, causing 36, 22 and 34 outbreaks respectively, have occurred throughout the entire period and have been of a more serious character. It was in 1953- 54 that efforts effectively to control salmonellosis in domestic animals were strongly advanced and were initiated by an outbreak of human salmonellosis which emanated from a slaughterhouse in the south of Sweden. In 1954 and for a number of years afterwards, animal salmonellosis was declared a notifiable disease and a slaughter policy was introduced whenever outbreaks were reported. The compensation of approximately £25,000 paid in 1956 for one single poultry-breeding farm, which was completely destroyed after having been incriminated as the source of S. ryphimurium infection in a few guests at a wedding dinner party, caused a change of mind in the responsible authorities and the slaughter policy was abandoned. However, salmonellosis has remained notifiable as a disease transmissible from animals to man. From a tentative start a programme was developed during the second half of the 1950S according to which each outbreak of salmonellosis is treated on its merits. An investigation by the local governmental veterinary officer is made into the epizootiology and distribution of the infection. A large number of different samples from every such investigation are taken for bacteriological examination, such as carcases, faeces, hatching eggs, shells, embryos, dust, feed and water, and likewise all purchases and sales of stock, eggs, feed, etc., are checked. Using these results, efforts are made to control the infection in a conservative manner and without disturbing the routine operations of the farm more than is necessary. Such measures may include the slaughter of a batch of
BRITISH VETERINARY JOURNAL, 119, 3
heavily infected chicks or destruction of a hatch of eggs, thereby creating, if possible, a "clean" unit on the premises where the management can continue while the outbreak is being controlled on the farm as a whole. In some instances chemotherapeutics or antibiotics are applied as adjuvants to this work. The progress of the work is followed by frequent sampling. Although it was realized that outbreaks of salmonellosis in animals are not easily controlled and that they offer most complex and intricate problems, it was also felt that the methods described were better than nothing and that their application under legislation might be worth while. InJuly, 1961, a new law for the control of salmonella infections in animals was instituted and details concerning the application of this law were issued by the Veterinary Board. Briefly, this law in principle is a legal confirmation of the control measures just described. Salmonella infections in all species of domestic animals are notifiable. Each outbreak is thoroughly investigated and the control measures, which may be compulsory, are decided upon on the basis of the findings. If slaughter or the destruction of hatching eggs is carried out, compensation is paid amounting to three-quarters of the value. These regulations have been in force for just over a year and it is too early to evaluate the results. To summarize, a total of 67 outbreaks of salmonellosis in animals have been reported, of which 14 were in poultry. On investigation seven of these lastmentioned outbreaks were negative and the rest have led to the application of control measures, including enforced partial slaughter in four cases. The total compensation paid in these outbreaks has amounted to approximately £10,000.
Bacteriological control offood An account of the control of salmonellosis in Sweden would be incomplete without reference to the bacteriological control of foodstuffs and their relation to animal health, a subject which has been of the greatest interest to the State Veterinary Medical Institute of Sweden for several years. In 1956 anthrax was introduced into Sweden by imported meat meal from Belgium and the bacteriological work carried out on different batches of meat meal during this investigation revealed a high contamination with Salmonellae. As a result the Royal Veterinary Board prescribed that all imported foodstuffs of animal origin had to be examined bacteriologically before their admission into the country and that, if contaminated by Salmonellae, they must be resterilized or re-exported. Thereafter, plans for the stricter veterinary control of foodstuffs took form and were brought into force at the beginning of 1960. Initiated by this institute, an association of Swedish foodstuff importers was formed to finance a bacteriological laboratory with modern equipment for the examination of foodstuffs, and staffed by a trained veterinary bacteriologist and technical assistants. In addition to the examination of all imported foodstuffs of both animal and vegetable origin, the activities of the laboratory include the epizootiological investigation of outbreaks of salmonellosis and the inspection of mills and factories ,vithin the commercial foodstuff industry, together with advisory
CONTROL OF POULTRY DISEASE
137
work arising from these investigations. Important results from this laboratory are (a) that feedstuffs not only of animal origin but also vegetable products, especially those industrially processed, may be heavily contaminated with Salmonellae, (b) the establishment of significant differences in the bacteriological quality of products from different factories and in different countries, and (c) the pasteurizing effect of hot pelleting. ~esJ1irato~
diseases Those who regard Newcastle disease, infectious bronchitis, infectious laryngotracheitis and mycoplasmosis as the chief disease problems of the poultry industries of their respective countries may have been given the impression that in Sweden these diseases are of little importance. This is true, inasmuch as the aforementioned diseases, except mycoplasmosis, are to the best of our knowledge seldom encountered. A brief account of the history of acute Newcastle disease outbreaks during the last 15 years has been given. In addition, infectious laryngotracheitis has been recorded on only two occasions, one from a very mild case without specific symptoms and one from a typical case in layers with about 10 per cent mortality. Infectious bronchitis virus has not been isolated · despite a detailed search for several years. Since 1955, 50 flocks with a more or less typical history of mycoplasmosis have been thoroughly investigated, and MycoJ1lasma has been isolated in 38 cases. Of these 38 strains, I I have proved to be identical culturally and serologically with M. galliseJ1ticum. The evidence suggests, therefore, that respiratory diseases present no problem provided that our frontiers are closed to imports. Control of imJ10rts Unfortunately this has been impossible. Faced by strong pressure from the poultry industry and with the ever-present menace of uncontrolled smuggling, the Royal Veterinary Board in 1959 decided to license the importation of poultry livestock in the form of hatching eggs or baby chicks. Each application is dealt with after consideration by the Royal Board of Agriculture and the Swedish Poultry Breeders' Association and no importation is licensed unless it is considered desirable by these authorities. Conditions under which import ation is licensed by the Veterinary Board are briefly as follows:( I) At the time of import a certificate issued by the veterinary authorities of the country of origin shall be produced to the Swedish customs authority showing:(a) that the export farm is situated in an area free from fowl cholera, fowl pest (Newcastle disease), infectious bronchitis, infectious laryngotracheitis and epidemic tremors. (b) that the export stock is free from fowl pox, avian diphtheria and salmonellosis (freedom from S. J1ullorum confirmed by a serological investigation within 12 months before the export). (c) that the chickens are healthy, show no evidence of contagious diseases, and have not originated from eggs produced within three weeks after the last vaccination of the breeding stock against Newcastle disease.
BRITISH VETERINARY JOURNAL, 119, 3
(2) At import, a guarantee from the exporter must be presented showing that the frequency ofleucosis and lymphomatosis in the breeding flocks during the previous two years did not exceed 4 per cent. (3) The imported stock must be quarantined for 12 months on previously inspected and approved premises, with bi-weekly inspection throughout the quarantine period by a government-appointed veterinary officer. (4) All chickens which die during the quarantine period must be sent to the State Veterinary Medical Institute for autopsy and bacteriological examination. (5) At 4-6 weeks and again at 12-14 weeks of age a proportionate number of ailing or retarded chicks must be sent to the State Veterinary Medical Institute for investigation, including examination for the presence of the viruses of Newcastle disease, infectious bronchitis and infectious laryngotracheitis, serological tests for Newcastle disease and mycoplasmosis, and cultivation for Mycoplasma. (6) At 16 weeks of age all chickens are tested for S. pullorum by the rapid slide agglutination test, and a 15 per cent sample of the birds are tested for . Newcastle disease by the haemagglutination inhibition test. Since 1959, 176,521 baby chicks have been imported into Sweden from eight exporting flocks in Belgium, Canada, Ireland, Italy, the U.S.A. and Western Germany, by eleven different importers. In all, 52 separate importations have been made, the majority of the chicks being intended as broiler parent stock. In four importations totalling 17,250 of Italian broiler parents during 1961, the total mortality up to 5 months of age varied between 2·8 and 6'0 per cent. In another importation of 4,000 laying stock parents and grandparents from the U.S.A., total mortality at 5 months was 3.8 per cent and at the end of the first year 8 ·67 per cent, which included 1··88 per cent leucosis, 0'26 per cent neurolymphomatosis and 1 '02 per cent egg peritonitis. The first generation of these birds hatched in Sweden experienced a mortality of slightly over 6 per cent up to sexual maturity. In 14,200 American broiler parents and grandparents imported, the mortality at 5 months was only 2'9 per cent. These figures represent the best results experienced with imported chicks in Sweden. They are not, however, chosen for this reason but because they apply to quarantine flocks in the neighbourhood of Stockholm and therefore fall within the writer's personal experience, and also because they include last year's imports from America. However, it is believed that, with few exceptions, these mortality statistics are representative of the majority of imported birds. To summarize, we feel that these importations have not prejudiced our position as far as infectious avian diseases are concerned. The few isolations of Newcastle disease and infectious laryngotracheitis viruses reported were made previous to any licensed importations and have no connection whatsoever with legally imported livestock. Some outbreaks of avian encephalomyelitis have occurred in broilers originating from imported birds, but this disease existed in Sweden as early as 1956 and its actual dissemination among Swedish breeding stock is uncertain.
CONTROL OF POULTRY DISEASE
I39
Poultry Stock Improvement Plan Within the Poultry Stock Improvement Plan disease control is regulated by the statutes of the Swedish Poultry Breeders' Association. Since 1920 blood testing for pullorum disease has been obligatory in order to obtain authorization by the Association as an approved breeding farm. In addition, such farms are subject to obligatory post-mortem examinations and the cause of mortality among all birds under progeny testing must be recorded. The autopsies are carried out by authorized veterinary laboratories throughout the country. All birds entered in the national laying test run by the Association are subject to similar regulations. These control measures, which are similar to those practised in stock improvement plans in other countries, are mainly aimed at controlling leucosis, and presumably have been about as effective as in other parts of the world. Leucosis is still the major problem, causing between 2.40 and 6·19 per cent mortality among the 800 pullets entered annually in the national laying test. The lack of progress in this work may be due to two main disadvantages in the scheme: firstly, the true disease incidence cannot be ascertained owing to the general practice of culling, even in breeding flocks under progeny testing, the culls not being checked on autopsy; secondly, the variable and even insufficient exposure to leucosis virus of flocks under a leucosis selection breeding programme. Furthermore, until recently, random sample tests have not been carried out in Sweden. Voluntary poultry health plans Partly to overcome these disadvantages, a Swedish veterinarian in 1940 instituted a voluntary Poultry Health Control programme, mainly for flocks outside the Poultry Stock Improvement Plan, operated in association with one of the provincial laboratories in the south-west of the country. The Royal Veterinary Board became interested in the programme and similar schemes have developed in several parts of the country. An interesting development in this programme is the association with a provincial veterinary laboratory and with a local poultry slaughterhouse. This association provides facilities for the post-mortem examination of 100 per cent of the birds in each flock, including the culls. A farmer participating in the plan must not send his culls or other birds for slaughter to any slaughterhouse other than that under the care of the veterinary officer in charge of the control programme. These schemes, however, have not been popular with the industry and have not yet received the interest and support they merit.
By
J.
KOHANE
Poultry Laboratory, Ministry of Agriculture, Hakirya, Tel-Aviv
The control of poultry diseases in Israel is performed by the Government Poultry Veterinary Service. This includes the department for poultry diseases of the Central Veterinary Institute and also four (soon to be increased to eight)
133
diseases. It is not desirable that the control of poultry disease should be undertaken by poultry breeders themselves or by lay advisers to the industry.
(D) General state measures In addition to endeavours by the state to control the different poultry diseases, there are general official measures which are carried out for the prevention of the spread of infectious poultry diseases. Poultry exhibitions and poultry markets are supervised by the staff of the state veterinary service and there are certain regulations which must be carried out, for example the vaccination against Newcastle disease. There is also in preparation a law for the construction of poultry slaughter houses and the carrying out of poultry meat inspection, as already practised in some countries. REFERENCE TRAUB,
E. (1943). Berl. Munch., tieriirz tl. Wschr., 56, 39.
(4) SWEDEN By N. O. LINDGREN State Veterinary Medical Institute, Stockholm Legislative control In accordance with the law for the control of infectious diseases of domestic animals (1935), fowl plague and fowl cholera are notifiable poultry diseases in Sweden. In 1939 infectious laryngotracheitis was added to these two. Measures according to this law were applied in 1947 when Newcastle disease, in the peracute form, appeared for the first time in Sweden as a few isolated, primary outbreaks due to feeding of small flocks with offal from imported frozen table poultry. The disease was first diagnosed as fowl plague but when it was subsequently confirmed by laboratory investigations as Newcastle disease the list of notifiable poultry diseases was extended to apply to "fowl plague-like diseases". Since the eradication of the disease was successfully brought about by the slaughter policy, only a few new sporadic outbreaks of the same kind have occurred, all primary and mainly due to importation of frozen poultry products such as table chickens, partridges and turkeys, mostly from Hungary and/or the Netherlands. The last outbreak occurred in 1956 and as a result a law was introduced prohibiting the importation of all but eviscerated table poultry or, alternatively, the sale and distribution of such products within the country. Pullorum disease History. In an account of the control of avian disease in Sweden, pullorum disease deserves special mention. In 1927 the disease was first recorded in a report from the Royal Medical Board- then the administrative body for veterinary legislation- and the following year it was declared as prevalent in the country. Three years later the disease was controlled by legislation. The
134
BRITISH VETERINARY JOURNAL, 119, 3
regulations were augmented in 1933 when the disease was regarded as a notifiable disease subject to strict control measures, and it remained so until the end of the 1940s. These facts encouraged owners of breeding flocks to carry out pullorum disease control measures by means of regular blood testing and this was shown by the steady increase in the number of serological tests (tube test) for Salmonella pullorum which were carried out at the State Veterinary Medical Institute. From a total of only 4,000 tests in 1939 these examinations reached a peak of 293,693 in 1948, of which 4,837 or 1·6 per cent were positive. On the other hand the strict obligatory measures enforced upon the farmers when the disease was suspected or diagnosed tended to render the control programme unpopular. Doubtless this led to concealment of the existence of outbreaks of the disease and hindered successful control of the disease. Present control oj pullorum disease. Such was the situation when in 1950 a new law was passed regulating the control of pullorum disease. All breeding flocks may now participate in a control programme; the regulations for this are designed by the state and they aim at the total eradication of the disease. Flocks which show positive reactors at two subsequent blood tests carried out at a six-month interval are given an official certificate stating that they are free from pullorum disease. Regular retesting is carried out yearly or every second or third year. From the start this programme was not considered by the veterinary authorities to be an ideal solution to the problem of pullorum disease control. Firstly, the scheme is restricted to breeding flocks and thus imposes no control of the disease in commercial laying flocks, and secondly, since participation is voluntary, it is possible for those breeders who have not the welfare of the industry at heart to allow the disease to flourish in their flocks. However, some compulsion can be exerted when the disease is diagnosed in a flock which, for example, by its geographical position constitutes a threat to neighbouring flocks. This regulation has not been used often during the ten years during which the programme has been in existence. Despite these disadvantages the control programme has had some success, especially during the first few years of its existence. In 1950 the owners of 1,034 flocks, comprising 518,929 birds, volunteered to join the scheme and in the years 1952-55 the number of participant flocks remained steady at around 1,200, which is approximately the total number of breeding flocks in the country. The number of birds within these flocks has been slightly over 700,000 and corresponds to about 10 per cent of the present total fowl population of Sweden. The progress of the work is illustrated by the fact that the percentage of officially declared pullorum-free flocks has increased from 42'3 in 1950 to 92'9 in 196 I. During the same period the percentage of infected flocks has been reduced from 8'1 in 1950 to 1'1 in 1961. The apparent discrepancy in these figures is due to the fact that there are always some flocks which, though not having any reactors, are on a "waiting list" for the official pullorumfree certificate. Future control. Progress in the eradication of pullorum disease, if studied
CONTROL OF POULTRY DISEASE
135
closely, shows a regression from the second half of the 1950S onwards. This is mainly due to the fact that some flocks were voluntarily withdrawn from the scheme and others were excluded from it for different reasons. Even if the majority of these flocks are still pullorum-free it is unsatisfactory not to have all breeding flocks under constant supervision. Results of this lack of supervision are now beginning to show by the appearance of outbreaks of pullorum disease in replacement or laying stock which can be traced back to such renegade breeding flocks. Therefore in Sweden the time is now thought to be opportune for the original plan of 1950 to be brought into force and for the voluntary control programme to be changed to a compulsory one, including all breeding flocks, and making freedom from pullorum disease a condition for the hatching and selling of all types of replacement stock. A law along these lines is ready to be adopted by the Swedish parliament in 1963; it was originally hoped that it would be passed in 1962.
Control of salmonellosis In 1950 when the present regulations for pullorum disease control were adopted it was believed not only that the change to a compulsory programme would sooner or later prove inevitable, but that efforts to control other salmonella infections of poultry would be included in the scheme. In Sweden, as in most other countries, such infections have shown an increasing incidence during the last 10-15 years. Some serotypes, such as Salmonella ryphimurium, Salmonella oranienburg, Salmonella montevideo, causing 36, 22 and 34 outbreaks respectively, have occurred throughout the entire period and have been of a more serious character. It was in 1953- 54 that efforts effectively to control salmonellosis in domestic animals were strongly advanced and were initiated by an outbreak of human salmonellosis which emanated from a slaughterhouse in the south of Sweden. In 1954 and for a number of years afterwards, animal salmonellosis was declared a notifiable disease and a slaughter policy was introduced whenever outbreaks were reported. The compensation of approximately £25,000 paid in 1956 for one single poultry-breeding farm, which was completely destroyed after having been incriminated as the source of S. ryphimurium infection in a few guests at a wedding dinner party, caused a change of mind in the responsible authorities and the slaughter policy was abandoned. However, salmonellosis has remained notifiable as a disease transmissible from animals to man. From a tentative start a programme was developed during the second half of the 1950S according to which each outbreak of salmonellosis is treated on its merits. An investigation by the local governmental veterinary officer is made into the epizootiology and distribution of the infection. A large number of different samples from every such investigation are taken for bacteriological examination, such as carcases, faeces, hatching eggs, shells, embryos, dust, feed and water, and likewise all purchases and sales of stock, eggs, feed, etc., are checked. Using these results, efforts are made to control the infection in a conservative manner and without disturbing the routine operations of the farm more than is necessary. Such measures may include the slaughter of a batch of
BRITISH VETERINARY JOURNAL, 119, 3
heavily infected chicks or destruction of a hatch of eggs, thereby creating, if possible, a "clean" unit on the premises where the management can continue while the outbreak is being controlled on the farm as a whole. In some instances chemotherapeutics or antibiotics are applied as adjuvants to this work. The progress of the work is followed by frequent sampling. Although it was realized that outbreaks of salmonellosis in animals are not easily controlled and that they offer most complex and intricate problems, it was also felt that the methods described were better than nothing and that their application under legislation might be worth while. InJuly, 1961, a new law for the control of salmonella infections in animals was instituted and details concerning the application of this law were issued by the Veterinary Board. Briefly, this law in principle is a legal confirmation of the control measures just described. Salmonella infections in all species of domestic animals are notifiable. Each outbreak is thoroughly investigated and the control measures, which may be compulsory, are decided upon on the basis of the findings. If slaughter or the destruction of hatching eggs is carried out, compensation is paid amounting to three-quarters of the value. These regulations have been in force for just over a year and it is too early to evaluate the results. To summarize, a total of 67 outbreaks of salmonellosis in animals have been reported, of which 14 were in poultry. On investigation seven of these lastmentioned outbreaks were negative and the rest have led to the application of control measures, including enforced partial slaughter in four cases. The total compensation paid in these outbreaks has amounted to approximately £10,000.
Bacteriological control offood An account of the control of salmonellosis in Sweden would be incomplete without reference to the bacteriological control of foodstuffs and their relation to animal health, a subject which has been of the greatest interest to the State Veterinary Medical Institute of Sweden for several years. In 1956 anthrax was introduced into Sweden by imported meat meal from Belgium and the bacteriological work carried out on different batches of meat meal during this investigation revealed a high contamination with Salmonellae. As a result the Royal Veterinary Board prescribed that all imported foodstuffs of animal origin had to be examined bacteriologically before their admission into the country and that, if contaminated by Salmonellae, they must be resterilized or re-exported. Thereafter, plans for the stricter veterinary control of foodstuffs took form and were brought into force at the beginning of 1960. Initiated by this institute, an association of Swedish foodstuff importers was formed to finance a bacteriological laboratory with modern equipment for the examination of foodstuffs, and staffed by a trained veterinary bacteriologist and technical assistants. In addition to the examination of all imported foodstuffs of both animal and vegetable origin, the activities of the laboratory include the epizootiological investigation of outbreaks of salmonellosis and the inspection of mills and factories ,vithin the commercial foodstuff industry, together with advisory
CONTROL OF POULTRY DISEASE
137
work arising from these investigations. Important results from this laboratory are (a) that feedstuffs not only of animal origin but also vegetable products, especially those industrially processed, may be heavily contaminated with Salmonellae, (b) the establishment of significant differences in the bacteriological quality of products from different factories and in different countries, and (c) the pasteurizing effect of hot pelleting. ~esJ1irato~
diseases Those who regard Newcastle disease, infectious bronchitis, infectious laryngotracheitis and mycoplasmosis as the chief disease problems of the poultry industries of their respective countries may have been given the impression that in Sweden these diseases are of little importance. This is true, inasmuch as the aforementioned diseases, except mycoplasmosis, are to the best of our knowledge seldom encountered. A brief account of the history of acute Newcastle disease outbreaks during the last 15 years has been given. In addition, infectious laryngotracheitis has been recorded on only two occasions, one from a very mild case without specific symptoms and one from a typical case in layers with about 10 per cent mortality. Infectious bronchitis virus has not been isolated · despite a detailed search for several years. Since 1955, 50 flocks with a more or less typical history of mycoplasmosis have been thoroughly investigated, and MycoJ1lasma has been isolated in 38 cases. Of these 38 strains, I I have proved to be identical culturally and serologically with M. galliseJ1ticum. The evidence suggests, therefore, that respiratory diseases present no problem provided that our frontiers are closed to imports. Control of imJ10rts Unfortunately this has been impossible. Faced by strong pressure from the poultry industry and with the ever-present menace of uncontrolled smuggling, the Royal Veterinary Board in 1959 decided to license the importation of poultry livestock in the form of hatching eggs or baby chicks. Each application is dealt with after consideration by the Royal Board of Agriculture and the Swedish Poultry Breeders' Association and no importation is licensed unless it is considered desirable by these authorities. Conditions under which import ation is licensed by the Veterinary Board are briefly as follows:( I) At the time of import a certificate issued by the veterinary authorities of the country of origin shall be produced to the Swedish customs authority showing:(a) that the export farm is situated in an area free from fowl cholera, fowl pest (Newcastle disease), infectious bronchitis, infectious laryngotracheitis and epidemic tremors. (b) that the export stock is free from fowl pox, avian diphtheria and salmonellosis (freedom from S. J1ullorum confirmed by a serological investigation within 12 months before the export). (c) that the chickens are healthy, show no evidence of contagious diseases, and have not originated from eggs produced within three weeks after the last vaccination of the breeding stock against Newcastle disease.
BRITISH VETERINARY JOURNAL, 119, 3
(2) At import, a guarantee from the exporter must be presented showing that the frequency ofleucosis and lymphomatosis in the breeding flocks during the previous two years did not exceed 4 per cent. (3) The imported stock must be quarantined for 12 months on previously inspected and approved premises, with bi-weekly inspection throughout the quarantine period by a government-appointed veterinary officer. (4) All chickens which die during the quarantine period must be sent to the State Veterinary Medical Institute for autopsy and bacteriological examination. (5) At 4-6 weeks and again at 12-14 weeks of age a proportionate number of ailing or retarded chicks must be sent to the State Veterinary Medical Institute for investigation, including examination for the presence of the viruses of Newcastle disease, infectious bronchitis and infectious laryngotracheitis, serological tests for Newcastle disease and mycoplasmosis, and cultivation for Mycoplasma. (6) At 16 weeks of age all chickens are tested for S. pullorum by the rapid slide agglutination test, and a 15 per cent sample of the birds are tested for . Newcastle disease by the haemagglutination inhibition test. Since 1959, 176,521 baby chicks have been imported into Sweden from eight exporting flocks in Belgium, Canada, Ireland, Italy, the U.S.A. and Western Germany, by eleven different importers. In all, 52 separate importations have been made, the majority of the chicks being intended as broiler parent stock. In four importations totalling 17,250 of Italian broiler parents during 1961, the total mortality up to 5 months of age varied between 2·8 and 6'0 per cent. In another importation of 4,000 laying stock parents and grandparents from the U.S.A., total mortality at 5 months was 3.8 per cent and at the end of the first year 8 ·67 per cent, which included 1··88 per cent leucosis, 0'26 per cent neurolymphomatosis and 1 '02 per cent egg peritonitis. The first generation of these birds hatched in Sweden experienced a mortality of slightly over 6 per cent up to sexual maturity. In 14,200 American broiler parents and grandparents imported, the mortality at 5 months was only 2'9 per cent. These figures represent the best results experienced with imported chicks in Sweden. They are not, however, chosen for this reason but because they apply to quarantine flocks in the neighbourhood of Stockholm and therefore fall within the writer's personal experience, and also because they include last year's imports from America. However, it is believed that, with few exceptions, these mortality statistics are representative of the majority of imported birds. To summarize, we feel that these importations have not prejudiced our position as far as infectious avian diseases are concerned. The few isolations of Newcastle disease and infectious laryngotracheitis viruses reported were made previous to any licensed importations and have no connection whatsoever with legally imported livestock. Some outbreaks of avian encephalomyelitis have occurred in broilers originating from imported birds, but this disease existed in Sweden as early as 1956 and its actual dissemination among Swedish breeding stock is uncertain.
CONTROL OF POULTRY DISEASE
I39
Poultry Stock Improvement Plan Within the Poultry Stock Improvement Plan disease control is regulated by the statutes of the Swedish Poultry Breeders' Association. Since 1920 blood testing for pullorum disease has been obligatory in order to obtain authorization by the Association as an approved breeding farm. In addition, such farms are subject to obligatory post-mortem examinations and the cause of mortality among all birds under progeny testing must be recorded. The autopsies are carried out by authorized veterinary laboratories throughout the country. All birds entered in the national laying test run by the Association are subject to similar regulations. These control measures, which are similar to those practised in stock improvement plans in other countries, are mainly aimed at controlling leucosis, and presumably have been about as effective as in other parts of the world. Leucosis is still the major problem, causing between 2.40 and 6·19 per cent mortality among the 800 pullets entered annually in the national laying test. The lack of progress in this work may be due to two main disadvantages in the scheme: firstly, the true disease incidence cannot be ascertained owing to the general practice of culling, even in breeding flocks under progeny testing, the culls not being checked on autopsy; secondly, the variable and even insufficient exposure to leucosis virus of flocks under a leucosis selection breeding programme. Furthermore, until recently, random sample tests have not been carried out in Sweden. Voluntary poultry health plans Partly to overcome these disadvantages, a Swedish veterinarian in 1940 instituted a voluntary Poultry Health Control programme, mainly for flocks outside the Poultry Stock Improvement Plan, operated in association with one of the provincial laboratories in the south-west of the country. The Royal Veterinary Board became interested in the programme and similar schemes have developed in several parts of the country. An interesting development in this programme is the association with a provincial veterinary laboratory and with a local poultry slaughterhouse. This association provides facilities for the post-mortem examination of 100 per cent of the birds in each flock, including the culls. A farmer participating in the plan must not send his culls or other birds for slaughter to any slaughterhouse other than that under the care of the veterinary officer in charge of the control programme. These schemes, however, have not been popular with the industry and have not yet received the interest and support they merit.
By
J.
KOHANE
Poultry Laboratory, Ministry of Agriculture, Hakirya, Tel-Aviv
The control of poultry diseases in Israel is performed by the Government Poultry Veterinary Service. This includes the department for poultry diseases of the Central Veterinary Institute and also four (soon to be increased to eight)