Newcastle Disease BY K. F. WELLS* N A DISCUSSION of any disease and its probable significance to the agricultural economy of the country, the history of the disease is im- portant and when this disease has only recently made its first appearance in the country the history becomes more important so that its probable impact may be judged. Newcastle Disease first was reported as such by Doyle in 1927 fol- lowing an outbreak of a severe high mortality disease in poultry at New- castle, England, and he gave it the name "Newcastle". Later it was found that the disease had actually been reported a year earlier in an obscure Veterinary Journal as occurring in the Dutch East Indies. Doyle was successful in demonstrating that the causative agent was a filtrable virus and that it was highly contagious, being easy to reproduce by inoculation. Newcastle Disease in Britain resulted in near 100 per cent mortality and an eradication policy was developed and with exception of a few out- breaks has successfully kept Britain free of the disease. During the next twenty years Newcastle Disease spread to a great many countries including Ceylon, India, the Philippines, Korea, Palis- tine, Africa, Japan, French Africa, Italy, Germany, Mexico and Austra- lia and in the majority of cases a new name was applied. The pathologists working with this disease soon began to wonder if these varieties of respiratory diseases were one and the same, so viruses were exchanged and following cross immunity and serum neutralization tests their suspicious were confirmed. Following this the name "New- castle" was generally adopted. In all these countries Newcastle Disease followed the pattern established in Britain, that is almost total mortality. In 1942 a respiratory nervous disorder of chickens called avian pneu- moencephalitis was described by Beach in California and in 1944 the virus of pneumoencephalitis and Newcastle disease were proven to be identical. This marked the first recognition of the condition in North America. Since the original work by Beach in California, Newcastle Disease has now spread to practically every State in the Union. Differences have been noted in the strains of viruses on its ap- pearance in many countries and these have often caused delay in its rec- ognition. This is particularly so in the case of the United States where the mild infectivity and low mortality rate which characterized the di- sease on its appearance in the United States had little in common with the highly fatal Newcastle Disease as seen in other parts of the world. The first obvious fact brought out by this brief review is that the disease is capable of very rapid spread. Another fact brought out by the literature is that when a new land is invaded the, first outbreaks usually occur in or near port cities. Realizing the potential danger to the Canadian poultry industry with * Health of Animals Branch, Department of Agriculture Ottawa, Address delivered at meeting of Western Ontario Veterinary Association Woodstock, April 1, 1948. [101]
Newcastle Disease
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Newcastle Disease BY K. F. WELLS*
N A DISCUSSION of any disease and its probable significance to the agricultural economy of the country, the history of the disease is im-
portant and when this disease has only recently made its first appearance in the country the history becomes more important so that its probable impact may be judged.
Newcastle Disease first was reported as such by Doyle in 1927 fol- lowing an outbreak of a severe high mortality disease in poultry at New- castle, England, and he gave it the name "Newcastle". Later it was found that the disease had actually been reported a year earlier in an obscure Veterinary Journal as occurring in the Dutch East Indies. Doyle was successful in demonstrating that the causative agent was a filtrable virus and that it was highly contagious, being easy to reproduce by inoculation. Newcastle Disease in Britain resulted in near 100 per cent mortality and an eradication policy was developed and with exception of a few out- breaks has successfully kept Britain free of the disease.
During the next twenty years Newcastle Disease spread to a great many countries including Ceylon, India, the Philippines, Korea, Palis- tine, Africa, Japan, French Africa, Italy, Germany, Mexico and Austra-lia and in the majority of cases a new name was applied.
The pathologists working with this disease soon began to wonder if these varieties of respiratory diseases were one and the same, so viruses were exchanged and following cross immunity and serum neutralization tests their suspicious were confirmed. Following this the name "New- castle" was generally adopted. In all these countries Newcastle Disease followed the pattern established in Britain, that is almost total mortality.
In 1942 a respiratory nervous disorder of chickens called avian pneu- moencephalitis was described by Beach in California and in 1944 the virus of pneumoencephalitis and Newcastle disease were proven to be identical. This marked the first recognition of the condition in North America. Since the original work by Beach in California, Newcastle Disease hasnow spread to practically every State in the Union.
Differences have been noted in the strains of viruses on its ap- pearance in many countries and these have often caused delay in its rec- ognition. This is particularly so in the case of the United States where the mild infectivity and low mortality rate which characterized the di- sease on its appearance in the United States had little in common with the highly fatal Newcastle Disease as seen in other parts of the world.The first obvious fact brought out by this brief review is that the disease is capable of very rapid spread. Another fact brought out by the literature is that when a new land is invaded the, first outbreaks usually occur in or near port cities.
Realizing the potential danger to the Canadian poultry industry with
* Health of Animals Branch, Department of Agriculture Ottawa, Address delivered at meeting ofWestern Ontario Veterinary Association Woodstock, April 1, 1948.
[101]
rio anadian Journal of Newcastle Disease April, 1948[1021 compaatJutdlo ecsl ies Vol. XII - No. 4[---~J Comparative Medicine Vl l o
Newcastle Disease so widespread in the United States and with consider- able interchange between the two countries, regulations were set up some- time ago prohibiting the entry into Canada of live poultry and hatching eggs unless accompanied by a certificate to the effect that they originated from flocks free of Newcastle Disease, also a regulation was established requiring the cleaning and disinfection of live poultry crates after each use. Along with these precautions Dr. Mitchell, Dominion Animal Pa- thologist, set up the necessary machinery to conduct accurate and rapid diagnosis.
Chickens appear to be the natural host of the virus but turkeys are highly susceptible. Pigeons, geese, ducks and other barnyard fowl are also susceptible, but to a lesser degree. The disease is easily trans- mitted to wild birds but the actual recovery of virus from these birds in an outbreak has not yet been reported.
Domestic birds of all ages are susceptible but the mortality rate varies considerably. The virus was recently demonstrated in chicks six days old at the Animal Diseases Research Institute. There was a history of a very high mortality rate in this case, but the majority of infections fall within three to eight weeks. Virus has also been demonstrated in mature fowl with very slight mortality. In fact all the possible com- binations of age., virulence and mortality can be found in the literature. Most reports indicate that the disease is seasonal. Adults appear to be infected during the winter closed housing season and then carrying on into the chicks during their hatching and brooding seasons. The infection appears to subside during the warmer weather. However, this may well be that the course has been run, and birds exposed or birds that have gone through an outbreak have resistance and it is not until next winter housing conditions return that there is a real opportunity for further spread.
Transmission is chiefly by means of infected exudates and excreta, with the digestive and respiratory systems being the main channels of natural infection. The offal of infected birds if refed to poultry is also considered a channel of dissemination. In view of this Great Britain has barred the import of undrawn poultry from all countries in which New- castle Disease is known to exist. Traffic in live birds is a definite danger - since inapparent and recovered cases can easily introduce infectiorn to new flocks. Dr. Jungherr of Storrs, Connecticut, reports that the virus of Newcastle Disease remained viable on non-sterile burlap, strips for twenty days regardless of the environmental conditions provided. On sterile strips the virus remained viable for thirteen days at 290F. and fifty-five days at 72°F. The virus was more resistant than fowl pox virus but considerably less resistant than Salmonella pullorum. In commenting upon his experiments he says that while none. permit any final conclu- sions the available results point towards the importance of the inanimate carrier due to the tenacity of the virus outside the body in the spread of Newcastle Disease.
While some differences may exist in the symptomatology of the infectious, extremely fatal malady in other parts of the world, our close proximity to the United States would warrant a description of the type of infection commonly described in that country which follows closely the symptoms found in recent outbreaks in Canada.
Canadian Journal of Newcstle Disease A uril. 1948 [1CQComparative Medicine Vol. XII - No. 4 [1031
In chicks of a few days to a few weeks of age, usually respiratory symptoms are first observed. Many will appear infected. Gasping for breath is frequent and if the bird is held close to the ear, moist rales or crackling sounds may be heard. If death does not result, the respiratory symptoms may subside and this syndrome may be followed by the ap- pearance of nervous symptoms. A profound stupor is first noticed and the affected chick rests on its hocks, with toes flexed, head depressed and eyes closed. The wings may also be abducted to support the body, other chicks may appear unable to use the legs and remain in lateral rec- umbency. Symptoms of ataxia such as staggering, torticollis and posterior propulsion are commonly present. Handling the chick, or drinking wa- ter, intensifies the nervous symptoms, causing the head to either be thrown backward or drawn under the body, or induces paroxysms in chicks which may not seem to be affected while undisturbed. Chicks which survive after showing nervous symptoms may continue to show evidence of damage for some weeks or even permanently.
The mortality rate in chick varies fromn 20 to 60 per cent. In adults likewise, respiratory symptoms are first seen and infection spreads ra- pidly. The most characteristic feature is the sudden drop in egg pro- duction which may drop to zero in a few days. An increase may be. noted in floor eggs some of which may be very soft shelled and odd shaped. Some cyanosis of the comb, loss of appetite and depression are present. The incidence of nervous symptoms in adults has been low and the mortality has been not nearly as high as that in young chicks.
From the standpoint of the veterinarian, Newcastle Disease should be suspected when a respiratory disease is present in a large percentage of the young chicks and associated with or followed by nervous or para- lytic symptoms. In such a combination the nervous symptoms exclude consideration of infectious bronchitis or laryngotracheitis.
Nervous or paralytic symptoms may be seen in riboflavin (B2) defi- ciency, encephalomalacia (E deficiency) and in avian encephalomyelitis (epidemic tremor) but in none of these instances is there a history of initial respiratory symptoms. The curled-in toes of the otherwise lively chick resting on its hocks is diagnostic of B2 deficiency. In E deficiency usually a high fish-liver oil content is noted in the feed. Both diseases recover with a change in ration.
While epidemic tremor is more difficult to diagnose, the tremor sytnptom is quite conspicuous and the disease does not yield to dietary changes. But in every instance the percentage of affected chicks is much lower than in Newcastle disease.
In adults, as in chicks, the symptoms may be somewhat similar to bronchitis and laryngotracheitis, but again in this instance, the appear- ance of nervous symptoms would eliminate both diseases. Also the mark- edly reduced egg production is not observed in these diseases.
Upon autopsy there is little to be found that would aid in the field diagnosis of Newcastle Disease. There may be evidence of dehydration. The trachea may contain fluid, mucous or even caseous material; there may even be caseous plugs but exudates of this nature are also seen in bronchitis and are therefore not singularily indicative of Newcastle. The air sac membranes in respiratory cases are usually clouded and may con- tain yellowish slime or yellow caseous masses but these changes are also seen in bronchitis. In acute changes the spleen may show some enlarge-
[10A1 Canadian Journal of Newcastle Dise April, 1948 Comparative Medicine Vol. XII - No. 4
ment. There are no gross changes in the brain regardless of the extent of the nervous symptoms.
From the varied symptoms and lack of definite postmortem clues it is apparent that a laboratory diagnosis is most essential in establishing an outbreak. The Hemagglutination test as described by Dr. Beach of California is used by the Animal Diseases Research Institute. The fact that the virus of Newcastle Disease has the ability to agglutinate red blood cells is the basis on which this test was developed. When suspected cases are submitted to the laboratory the spleen is removed in a manner to avoid outside contamination. The tissue or tissues taken are ground and mixed with broth. Fertile eggs incubated for nine to eleven days are then inoculated. The inoculated eggs are candled daily until the death of the embryo takes place. If Newcastle is present this takes place anywhere from forty-eight hours to the fifth or sixth day. The fluids are drawn from the dead embryo and set up with red blood cells (chicken). If positive, hemagglutination takes place in a short time (approximately thirty minutes). This is then checked by mixing known immune serum with the fluids from the dead embryo and setting up another test. The immune serum will neutralize the virus in the em- bryonic fluid and hemagglutination will not take place. This ability to agglutinate red blood cells is also exhibited by the virus of influenza and precautions must be taken to eliminate the possibility of this being the agent responsible for the agglutination.
The work on immunization of chickens against Newcastle Disease can be summed up by saying that the use of a killed virus has met with little success, however, chickens recovered from natural infection or inoculated with a potent live virus will develop an immunity which ap- pears to be permanent. A study was conducted at the Massachusetts State College to pick a strain of the virus which would have potential value in a practical immunization program and yet not be of sufficient viru- lence to cause an outbreak. Such a strain seems to have been found but the usual question remains-are these vaccinates carriers and once this system is adopted would it necessitate continual vaccination in all flocks.
N A DISCUSSION of any disease and its probable significance to the agricultural economy of the country, the history of the disease is im-
portant and when this disease has only recently made its first appearance in the country the history becomes more important so that its probable impact may be judged.
Newcastle Disease first was reported as such by Doyle in 1927 fol- lowing an outbreak of a severe high mortality disease in poultry at New- castle, England, and he gave it the name "Newcastle". Later it was found that the disease had actually been reported a year earlier in an obscure Veterinary Journal as occurring in the Dutch East Indies. Doyle was successful in demonstrating that the causative agent was a filtrable virus and that it was highly contagious, being easy to reproduce by inoculation. Newcastle Disease in Britain resulted in near 100 per cent mortality and an eradication policy was developed and with exception of a few out- breaks has successfully kept Britain free of the disease.
During the next twenty years Newcastle Disease spread to a great many countries including Ceylon, India, the Philippines, Korea, Palis- tine, Africa, Japan, French Africa, Italy, Germany, Mexico and Austra-lia and in the majority of cases a new name was applied.
The pathologists working with this disease soon began to wonder if these varieties of respiratory diseases were one and the same, so viruses were exchanged and following cross immunity and serum neutralization tests their suspicious were confirmed. Following this the name "New- castle" was generally adopted. In all these countries Newcastle Disease followed the pattern established in Britain, that is almost total mortality.
In 1942 a respiratory nervous disorder of chickens called avian pneu- moencephalitis was described by Beach in California and in 1944 the virus of pneumoencephalitis and Newcastle disease were proven to be identical. This marked the first recognition of the condition in North America. Since the original work by Beach in California, Newcastle Disease hasnow spread to practically every State in the Union.
Differences have been noted in the strains of viruses on its ap- pearance in many countries and these have often caused delay in its rec- ognition. This is particularly so in the case of the United States where the mild infectivity and low mortality rate which characterized the di- sease on its appearance in the United States had little in common with the highly fatal Newcastle Disease as seen in other parts of the world.The first obvious fact brought out by this brief review is that the disease is capable of very rapid spread. Another fact brought out by the literature is that when a new land is invaded the, first outbreaks usually occur in or near port cities.
Realizing the potential danger to the Canadian poultry industry with
* Health of Animals Branch, Department of Agriculture Ottawa, Address delivered at meeting ofWestern Ontario Veterinary Association Woodstock, April 1, 1948.
[101]
rio anadian Journal of Newcastle Disease April, 1948[1021 compaatJutdlo ecsl ies Vol. XII - No. 4[---~J Comparative Medicine Vl l o
Newcastle Disease so widespread in the United States and with consider- able interchange between the two countries, regulations were set up some- time ago prohibiting the entry into Canada of live poultry and hatching eggs unless accompanied by a certificate to the effect that they originated from flocks free of Newcastle Disease, also a regulation was established requiring the cleaning and disinfection of live poultry crates after each use. Along with these precautions Dr. Mitchell, Dominion Animal Pa- thologist, set up the necessary machinery to conduct accurate and rapid diagnosis.
Chickens appear to be the natural host of the virus but turkeys are highly susceptible. Pigeons, geese, ducks and other barnyard fowl are also susceptible, but to a lesser degree. The disease is easily trans- mitted to wild birds but the actual recovery of virus from these birds in an outbreak has not yet been reported.
Domestic birds of all ages are susceptible but the mortality rate varies considerably. The virus was recently demonstrated in chicks six days old at the Animal Diseases Research Institute. There was a history of a very high mortality rate in this case, but the majority of infections fall within three to eight weeks. Virus has also been demonstrated in mature fowl with very slight mortality. In fact all the possible com- binations of age., virulence and mortality can be found in the literature. Most reports indicate that the disease is seasonal. Adults appear to be infected during the winter closed housing season and then carrying on into the chicks during their hatching and brooding seasons. The infection appears to subside during the warmer weather. However, this may well be that the course has been run, and birds exposed or birds that have gone through an outbreak have resistance and it is not until next winter housing conditions return that there is a real opportunity for further spread.
Transmission is chiefly by means of infected exudates and excreta, with the digestive and respiratory systems being the main channels of natural infection. The offal of infected birds if refed to poultry is also considered a channel of dissemination. In view of this Great Britain has barred the import of undrawn poultry from all countries in which New- castle Disease is known to exist. Traffic in live birds is a definite danger - since inapparent and recovered cases can easily introduce infectiorn to new flocks. Dr. Jungherr of Storrs, Connecticut, reports that the virus of Newcastle Disease remained viable on non-sterile burlap, strips for twenty days regardless of the environmental conditions provided. On sterile strips the virus remained viable for thirteen days at 290F. and fifty-five days at 72°F. The virus was more resistant than fowl pox virus but considerably less resistant than Salmonella pullorum. In commenting upon his experiments he says that while none. permit any final conclu- sions the available results point towards the importance of the inanimate carrier due to the tenacity of the virus outside the body in the spread of Newcastle Disease.
While some differences may exist in the symptomatology of the infectious, extremely fatal malady in other parts of the world, our close proximity to the United States would warrant a description of the type of infection commonly described in that country which follows closely the symptoms found in recent outbreaks in Canada.
Canadian Journal of Newcstle Disease A uril. 1948 [1CQComparative Medicine Vol. XII - No. 4 [1031
In chicks of a few days to a few weeks of age, usually respiratory symptoms are first observed. Many will appear infected. Gasping for breath is frequent and if the bird is held close to the ear, moist rales or crackling sounds may be heard. If death does not result, the respiratory symptoms may subside and this syndrome may be followed by the ap- pearance of nervous symptoms. A profound stupor is first noticed and the affected chick rests on its hocks, with toes flexed, head depressed and eyes closed. The wings may also be abducted to support the body, other chicks may appear unable to use the legs and remain in lateral rec- umbency. Symptoms of ataxia such as staggering, torticollis and posterior propulsion are commonly present. Handling the chick, or drinking wa- ter, intensifies the nervous symptoms, causing the head to either be thrown backward or drawn under the body, or induces paroxysms in chicks which may not seem to be affected while undisturbed. Chicks which survive after showing nervous symptoms may continue to show evidence of damage for some weeks or even permanently.
The mortality rate in chick varies fromn 20 to 60 per cent. In adults likewise, respiratory symptoms are first seen and infection spreads ra- pidly. The most characteristic feature is the sudden drop in egg pro- duction which may drop to zero in a few days. An increase may be. noted in floor eggs some of which may be very soft shelled and odd shaped. Some cyanosis of the comb, loss of appetite and depression are present. The incidence of nervous symptoms in adults has been low and the mortality has been not nearly as high as that in young chicks.
From the standpoint of the veterinarian, Newcastle Disease should be suspected when a respiratory disease is present in a large percentage of the young chicks and associated with or followed by nervous or para- lytic symptoms. In such a combination the nervous symptoms exclude consideration of infectious bronchitis or laryngotracheitis.
Nervous or paralytic symptoms may be seen in riboflavin (B2) defi- ciency, encephalomalacia (E deficiency) and in avian encephalomyelitis (epidemic tremor) but in none of these instances is there a history of initial respiratory symptoms. The curled-in toes of the otherwise lively chick resting on its hocks is diagnostic of B2 deficiency. In E deficiency usually a high fish-liver oil content is noted in the feed. Both diseases recover with a change in ration.
While epidemic tremor is more difficult to diagnose, the tremor sytnptom is quite conspicuous and the disease does not yield to dietary changes. But in every instance the percentage of affected chicks is much lower than in Newcastle disease.
In adults, as in chicks, the symptoms may be somewhat similar to bronchitis and laryngotracheitis, but again in this instance, the appear- ance of nervous symptoms would eliminate both diseases. Also the mark- edly reduced egg production is not observed in these diseases.
Upon autopsy there is little to be found that would aid in the field diagnosis of Newcastle Disease. There may be evidence of dehydration. The trachea may contain fluid, mucous or even caseous material; there may even be caseous plugs but exudates of this nature are also seen in bronchitis and are therefore not singularily indicative of Newcastle. The air sac membranes in respiratory cases are usually clouded and may con- tain yellowish slime or yellow caseous masses but these changes are also seen in bronchitis. In acute changes the spleen may show some enlarge-
[10A1 Canadian Journal of Newcastle Dise April, 1948 Comparative Medicine Vol. XII - No. 4
ment. There are no gross changes in the brain regardless of the extent of the nervous symptoms.
From the varied symptoms and lack of definite postmortem clues it is apparent that a laboratory diagnosis is most essential in establishing an outbreak. The Hemagglutination test as described by Dr. Beach of California is used by the Animal Diseases Research Institute. The fact that the virus of Newcastle Disease has the ability to agglutinate red blood cells is the basis on which this test was developed. When suspected cases are submitted to the laboratory the spleen is removed in a manner to avoid outside contamination. The tissue or tissues taken are ground and mixed with broth. Fertile eggs incubated for nine to eleven days are then inoculated. The inoculated eggs are candled daily until the death of the embryo takes place. If Newcastle is present this takes place anywhere from forty-eight hours to the fifth or sixth day. The fluids are drawn from the dead embryo and set up with red blood cells (chicken). If positive, hemagglutination takes place in a short time (approximately thirty minutes). This is then checked by mixing known immune serum with the fluids from the dead embryo and setting up another test. The immune serum will neutralize the virus in the em- bryonic fluid and hemagglutination will not take place. This ability to agglutinate red blood cells is also exhibited by the virus of influenza and precautions must be taken to eliminate the possibility of this being the agent responsible for the agglutination.
The work on immunization of chickens against Newcastle Disease can be summed up by saying that the use of a killed virus has met with little success, however, chickens recovered from natural infection or inoculated with a potent live virus will develop an immunity which ap- pears to be permanent. A study was conducted at the Massachusetts State College to pick a strain of the virus which would have potential value in a practical immunization program and yet not be of sufficient viru- lence to cause an outbreak. Such a strain seems to have been found but the usual question remains-are these vaccinates carriers and once this system is adopted would it necessitate continual vaccination in all flocks.
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