Volume 19
THE CANADIAN VETERINARY JOURNAL LA REVUE VPTE'RINAIRE CANADIENNE September-septembre 1978
Incidence of Clinical Coccidiosis in Chickens in the Ontario Veterinary Services Branch Records 1973-1977 ENG-HONG LEE AND D.K. ONDERKA*
INTRODUCTION
Coccidiosis is still being recorded as one of the most commonly diagnosed diseases of chickens in Canada (9, 10, I 1) despite millions of dollars being spent each year on anticoccidial drugs added in feed for its control. Records accumulated by the Ontario Veterinary Services Branch (VSB) during the period from 1973 to 1977 showed that clinical coccidiosis in Ontario was equally prevalent. These VSB records were analysed with a a view to gaining some information about the disease in the field. Use of some of the findings from these records in conjunction with drug rotation as a means of control of coccidiosis in chickens is discussed. MATERIALS AND METHODS
Results are mostly derived from the computerized data collected from materials submitted to all six regional laboratories of the Ontario Veterinary Services Branch in Brighton (144), Guelph (91), Kemptville (72), Huron Park (49), Ridgetown (40) and New Liskeard (10). The numbers in parenthesis indicate consignments or cases of clinical coccidiosis reported from each laboratory with a total of 406 during the five years from 1973 to 1977. In most cases, live or dead chickens were submitted but sometimes in referral cases of private practitioners or others, guts or fecal suspensions in potassium dichromate were also submitted. Diagnosis was based on clinical signs, gross lesions at postmortem examination, and the presence of parasites in intestinal or cecal scrapings. Efforts to identify species of coccidia were made
No. 9
inconsistently. As a consequence all coccidia were differentiated either as cecal or intestinal. Species identified in Guelph, appear to be similar to those reported recently in the U.S. (3), namely Eimeria acervulina, E. maxima, E. tenella and E. necatrix and E. brunetti. Data of the three other most frequently diagnosed diseases of chickens (Table I), one viral (Marek's) and two bacterial (necrotic enteritis and colibacillosis), were also plotted. They serve as internal sampling controls for detecting possible bias in the timing of submissions for diagnosis to the VSB laboratories at different months of the year. The chickens submitted were differentiated into three types: broilers, layers and others. The last type included the unrecorded, some breeders and both broilers and layers kept on hobby farms. RES ULTS
There were 18 consignments reported as infected with both cecal and intestinal coccidiosis decreasing the total number of consignments from 424 to 406 (Table 1). Four hundred and six is still the largest number among the four common poultry diseases reported here with Marek's disease (333), necrotic enteritis (219) and colibacillosis (88) ranked in descending order. Less than 2% (6/406 consignments) of these were diagnosed as infected with both necrotic enteritis and coccidiosis. The monthly incidence of clinical coccidiosis started *to increase in May, peaked in July, maintained relatively high levels until October, then declined to lower levels in the cold months (Figure 1). This trend was true for each of the five years from 1973 to 1977 except the decrease in June of 1974 and the peak in August of 1973. In order to show the trend more clearly, each of these monthly incidences was added to arrive at Figure 2. Figure 2 shows the cumulative incidence of clinical coccidiosis remained near 20 from November to May with 16 and 17 cases in December and April respectively. The incidence started to increase in May, rose to 39 in June and to 80 in July. The number then declined to 62 in August, 41 in September and 37 in October. This monthly distribution of the incidence of coccidiosis seemed to divide the year conveniently into two halves where the higher incidence (70%0 or
*Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario NIG 2WI (Lee) and Veterinary Services Branch, Ontario Ministry of Agriculture and Food, Box 3612, Guelph, Ontario NIH 6R8 (Onderka).
Can. vet. J. 19: 237-243 (September 1978)
237
TABLE I INCIDENCE OF THE FOUR MOST FREQUENTLY DIAGNOSED DISEASES OF CHICKEN IN THE Six REGIONAL LABORATORIES OF THE ONTARIO VETERINARY SERVICES BRANCH YEARS 1973-1977 IN VARIOUS TYPES OF CHICKENS Incidence
Type
Coccidiosis
37 Ca
Broilers
114 59 112 37 65
Layers
Others
lb C
Necrotic enteritis
Colibacillosis
53
141
53
156
31
9
4
124
47
26
2
333
219
88
6
333
219
88
6
I
C I
Sub Total 424 C+ I -18 Total 406 a C = cecal coccidiosis b I = intestinal coccidiosis 15
Marek's
283/406 consignments) occurred in the warmer six months between May and October and the lower incidence (30%) in the colder six months. For the warmer six months during the period from 1973 to 1976 (records for 1977 are not yet complete) the average temperature varied from 11.80 C in May to a high of 20.40 C in July and then declined to about 8.70 C in October. The average temperatures of the colder six months were 3.60C in November, a low of -5.60 C in January, and 6.10 C in April (Figure 2).
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201
1973
15
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FIGURE 1. Monthly distribution of the incidence of clinical coccidiosis of each of the five years from 1973 to 1977 recorded by the Ontario Veterinary Services Branch.
238
Coccidiosis N. enteritis
These figures were those of the Lake Ontario counties. In general they were about two degrees lower than those of Lake Erie and Niagara counties but one or two degrees higher than the rest of Southern Ontario (Monthly Records, Fisheries and Environment Canada). The monthly distribution of necrotic enteritis followed the same pattern as coccidiosis (Figure 2) with 64% (140/219 consignments) in the warmer months and 36% in the colder months. No similar trend in distribution was detected for Marek's disease or colibacillosis. No monthly fluctuation was apparent in the number of laying hens maintained between January 1976 to December 1977 in Ontario (Figure 2) (personal communication, Mr. Marcus Walker, Ontario Egg Producers' Marketing Board). The number of layers in Figure 2 represent at least 95% of all laying hens 24 weeks of age or older in Ontario. The maximum monthly fluctuation in broiler production in Canada for the six years from 1971 to 1976 was about 27% or (1-14.4/ 19.8) x 100 (Figure 2). The number 14.4 refers to the number of million of broilers produced in February 1976 (the lowest month) and 19.8 million in July (the highest month) of the same year (Canadian Poultryman, July supplement 1977). More than one third (209/609 million pounds) of all broilers produced in Canada in 1976 were raised in Ontario (personal communication, Dr. John P. Walker, Department of Animal and Poultry Science. University of Guelph).
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FIGURE 2. Monthly distribution of the incidence of clinical coccidiosis and other frequently diagnosed chicken diseases in the Ontario Veterinary Services Branch records years 1973 to 1977. They are: clinical coccidiosis The average Marek's disease (0-O), necrotic enteritis (O O) and colibacillosis ) in Canada. The number of laying hens number of broilers produced in 1971 to 1975 (A--A) and in 1976 (Ain Ontario for the years 1976 and 1977 (+--.- +) were also superimposed. Numbers below the respective months of the year represent the averaged temperatures of the Lake Ontario counties from years 1973 to 1976. ........0
Infection among broilers occurred in birds as young as one week of age but 80% (112/140
consignments) of the infections occurred in three (Figure 3). The majority (58%) was concentrated in birds four to five weeks of age. The majority or 71% (91/142 consignments) of to seven week old chickens
the clinical coccidiosis among layers was found in birds four to 13 weeks of age (Figure 4). The proportion then decreased to 22% in the next 11 weeks. Infections were reported in birds of all age groups including a flock of two year old layers with cecal coccidiosis. The incidence of clinical coccidiosis among
239
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w
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6
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10
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14
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18
20
22
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FIGURE 3. Relation between incidence of clinical coccidiosis, intestinal (blank) and cecal (striped), and the age of broilers in the Ontario VSB records years 1973 to 1977. 20
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FIGURE 4. Relation between incidence of clinical coccidiosis, intestinal (blank) and cecal (striped), and age of layers in the Ontario VSB records years 1973 to 1977.
different age groups of other chickens was 61% (51/83 consignments) in the first ten weeks, 32% in the next eight weeks and became sporadic thereafter (Figure 5). A flock of two year old birds infected with coccidiosis (intestinal) was also reported. In almost all submissions a low mortality was observed. DISCUSSION
The monthly incidence curve in Figure 2 most likely represents the true trend in clinical cocci240
diosis among chickens raised in Ontario. The reasons are as follows: First, the trend was not influenced by the number of laying hens in Ontario because the latter showed no apparent monthly change (Figure 2). Second, even though fluctuation did occur in the number of broilers, the maximum monthly difference was 27% which could hardly account for the fivefold difference between the highest and lowest monthly incidence of clinical coccidiosis. Moreover, such difference occurred because of the unusually low number of broilers raised in the month of February. Otherwise, only slight monthly differences could be
15
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10
12
14
16
18
20
22
24
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7
9
11
WEEKS
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15
24
MONTHS
FIGURE 5. Relation between incidence of clinical coccidiosis, intestinal (blank) and cecal (striped), and age of other chickens in the Ontario VSB records years 1973 to 1977.
found in the number of broilers produced during the other 11 months of the year (Figure 2). Third, it was unlikely that farmers would send more of their sick chickens to the VSB laboratories but not to the private practitioners or laboratories for diagnosis in the warmer six months thus causing a rise in the incidence of clinical coccidiosis. If such bias existed, it could not explain why a similar trend did not occur for Marek's disease and colibacillosis (Figure 2). Fourth, the influence of the incidence of necrotic enteritis on that of clinical coccidiosis was negligible because less than 2% (6/406 consignments) of all clinical coccidiosis was diagnosed as also being infected by necrotic enteritis. Therefore, the trend of higher incidence of clinical coccidiosis in the warmer six months but lower in the colder six months was most likely true. Higher incidences of coccidiosis recorded between the months of May and October may be explained partly by the fact that the warmer (thus more humid) conditions favour oocyst sporulation. The same reason also seemed adequate to explain why all incidence of coccidiosis in the colder months, at least for those reported to the VSB laboratory in Guelph in 1976 and 1977, were reported from larger farms (Table II) capable of keeping the barn temperature and humidity rather constant year round. The marked difference in incidence of coccidiosis between the warmer and the colder months may be a useful piece of information for the chemotherapeutic control of coccidiosis. It is now evident that control of coccidiosis by drugs is becoming increasingly difficult, because of the emergence of drug resistant strains of coccidia refractory to one or many of the 19 anticoccidial drugs introduced since the 1940's (6, 8). Drug resistant strains of avian coccida have been reported in Canada (5). Presently, the only practical means of overcoming the problem of drug resistance is by rotating or switching drugs to a newly introduced drug or to an existing drug to which the coccidia
TABLE II INCIDENCE OF CLINICAL COCCIDIOSIS AMONG LARGE AND SMALL FARMS AS RECORDED BY THE ONTARIO VSB IN GUELPH FOR YEARS 1976 AND 1977 Incidence Months
Large farms
May to October
15
(5,000-60,000)
Small farms
12 (40-400)
chickens
Nov. to April
6 (3,000-18,000) chickens
chickens
0
are still sensitive. Clinical coccidiosis in chickens
may be better controlled if the timing of drug rotation was synchronized with the change in the incidence of coccidiosis between warmer and colder months. Changing of anticoccidial drugs near the end of April or early May might more effectively prevent clinical coccidiosis during the months of higher incidence. Changing again at the end of October or early November may be necessary to prevent unduly prolonged exposure, the main cause of drug resistance. It must be pointed out, however, that drug rotation without drug sensitivity tests sometimes may result in outbreaks rather than prevention (12). The relationship between the incidence of clinical coccidiosis and the age of the host shown in Figure 3 almost directly replicates that reported by Long (6). Long showed the mean number of oocysts per gram of litter started to increase when broilers were two weeks of age. The number then peaked among four week old broilers after which it decreased until it became negligible again at eight weeks. These two almost identical findings suggest that the number of oocysts in the litter may be the main cause of clinical coccidiosis in the field. Since it takes only five to six days for infections to show clinical signs, the peak infections among four week old broilers (Figure 3) likely resulted from ingestion of sporulated oocysts produced by themselves when they were two to three weeks of age.
241
Based on these findings a preventive measure for more effective control of coccidiosis among broilers may be feasible. The measure is to submit broilers two weeks of age or younger to the VS B or similar laboratories for diagnosis. If signs of coccidiosis or a large number of oocysts, particularly those of the more pathogenic species of E. tenella and E. necatrix, were found in these young birds, drug rotation should be immediately applied irrespective of the month of the year. Such preventive measures are particularly useful in broiler farms with a recent history of outbreak of clinical coccidiosis. Similar measures may be taken for young layers and other chickens. The fact that layers and other chickens were infected at all age groups, including birds as old as two years of age (Figures 4 and 5) suggests that the degree of immunity acquired varies among different flocks of birds (4). Such examples of older field flocks being susceptible to further (experimental) infections have been shown previously (2, 4). However, unlike the finding of Karlsson and Reid (4), some losses did occur in older birds submitted to the VSB laboratory in Guelph. Undoubtedly, in some instances other diseases might have also played a role in causing death. This and the relation of factors such as the size of farm operation, the quality of management, nutrition, and others, to clinical coccidiosis remain to be
investigated. Ideally, control of coccidiosis by drug rotation should be guided by drug sensitivity tests. However general availability of such tests presently is absent in Canada. As a consequence, drug rotation rather than a routine procedure, sometimes was practised only when high feed conversion or coccidiosis outbreaks among chickens were noticed. High feed conversion and outbreaks were two major reasons for submitting chickens to the VSB laboratories. Guidance for the logical rotation to, and selection of, anticoccidial drugs has been previously suggested by Reid (7), Ryley and Betts (8) and Eckman (1). However, there is no general guidance as to when a drug should be routinely rotated. The timing of high and low monthly incidence of clinical coccidiosis reported here perhaps can serve as a logical guide. SUMMARY
The incidence of clinical coccidiosis recorded by the six regional laboratories of the Ontario Veterinary Services Branch from years 1973 to 1977 was analysed. Seventy percent (283/406) of the consignments was distributed between May to October and 30% from November to April, with the highest incidence of 80 consignments in July and the lowest, 16 consignments, in December. Among broilers, infections occurred in birds as young as one week of age but 80% (112/140 consignments) were found in birds three to seven weeks of age with the majority (58%) concentrated in the four to five week old birds. 242
Although the higher incidence of clinical coccidiosis among layers and other chickens was in the younger birds (four to 12 weeks), infections were recorded in birds of all ages including two flocks of two year olds. Possible use of these data with drug rotation for better control of coccidiosis in chickens is discussed. Rt-S UM t
Les auteurs ont analyse l'incidence naturelle de la coccidiose, en Ontario, au cours de la periode de 1973 a 1977, en se basant sur les donnees disponibles dans les six laboratoires regionaux du Service veterinaire de cette province. Ils realiserent que 70% des envois (283/406) avaient eu lieu entre les mois de mai et d'octobre et que 30% avaient eu lieu entre les mois de novembre et d'avril. Le plus grand nombre d'envois, soit 80, se fit en juillet et le nombre le moins eleve, soit 16, en decembre. On diagnostiqua la coccidiose chez des poulets ages de seulement une semaine; 80% des cas affectaient cependant des sujets ages de trois a sept semaines et repartis dans 112 des 140 envois; la majorite de ces cas, soit 58%, impliquait neanmoins des sujets ages de quatre a cinq semaines. Meme si l'incidence la plus elevee de coccidiose clinique chez les pondeuses et les autres poulets s'observait chez les plus jeunes sujets de ces groupes (quatre a 12 semaines), on en enregistra des cas chez des sujets de tous les ages, y compris certains de deux troupeaux de pondeuses agees de deux ans. Les auteurs commentent en dernier lieu l'utilisation possible de ces donnees en rapport avec la rotation de la medication, dans le but d'obtenir un meilleur contrBle de la coccidiose aviaire. ACKNOWLEDGM ENTS
We thank Drs. J.P Lautenslager and K.R. Mittal for their assistance in the preparation of this manuscript and Dr. S.W. Martin for suggesting Figure 1. The partial financial support of the National Research Council and the Ontario Ministry of Agriculture and Food funded through Dr. M.A. Fernando and the Department of Pathology, University of Guelph is gratefully acknowledged. REFERENCES 1. ECKMAN, M.K. Evaluating anticoccidials in poultry in the United States. Practg. Nutr. 10: 14-21. 1976. 2. EDGAR, S.A. Coccidiosis of chickens and turkeys and control by immunization. Avicult. Mod. Mem. XI
Cong. Mondial Avicultura. pp. 415-421, 679. 1958. 3. JEFFERS, T.K.Eimeria acervulina and E. maxima: Incidence and anti-coccidial drug resistance of isolants in major broiler-producing areas. Avian Dis. 18: 331-342. 1974. 4. KARLSSON, T. and W.M. REID. Prevalence of Eimeria acervulina, E. necatrix, E. brunetti and E.
5. 6.
7.
8.
tenella in Georgia (USA) as demonstrated by immunity challenge techniques. Br. Poult. Sci. 18: 497-501. 1977. LEE, E.-H. and M.A. FERNANDO. Drug resistance in coccidia: A robenidine-resistant strain of Eimeria tenella. Can. J. comp. Med. 41: 466-470. 1977. LONG, P.L. Chickens: The control of coccidiosis. Span. pp. 26-28. Jan. 1977. REID, W.M. Anticoccidials: Differences in day of peak activity against Eimeria tenella. In Proceedings of the Symposium on Coccidia and Related Organisms. pp. 1 19-134. Guelph, Ontario: University of Guelph. 1973. RILEY. J.F. and M.J. BETTS. Chemotherapy of
ANALYSE DE VOLUME/ BOOK REVIEW Animal Physiologic Surgery. C. Max Lang. Published by Springer-Verlag, New York. 1976. 180 pages. Price $10.80.
Textbooks often develop from course handouts or mimeographed manuals. As mentioned in the preface, Dr Lang's text originates from these sources. The book is divided into three parts. The first, Introduction to Surgery, includes very basic information on operating room procedures, sutures and instruments, wound healing, anesthesia, and water and electrolyte balance. The second part deals with surgical instructions and some clinical consideration of nine surgical procedures, such as laparatomy, splenectomy, nephrectomy, etc. The third segment relates to laboratory methods used for the evaluation of the patient and postmortem techniques. The title of the book is misleading; "Elements of Physiological Surgery in the Dog" would have been more appropriate. The text is clear and succinct, even though the reader may get the impression that it has been hastily written. The book is intended for first year medical students and graduate students in physiology. It should serve that purpose
9. 10.
1l. 12.
chicken coccidiosis. Adv. Pharmac. Chemother. 11: 221-293. 1973. STEPHEN, L.E. Poultry diseases diagnosed in Canadian laboratories for the year 1973. Can vet. J. 16: 65-70. 1975. STEPHEN, L.E. Poultry diseases diagnosed in Canadian laboratories for the year 1974. Can. vet. J. 17: 145-149. 1976. STEPHEN, L.E. Poultry diseases diagnosed for Canadian laboratories for the year 1975. Can. vet. J. 18: 297-300. 1977. WEBER, L.J. Clinical coccidiosis. Can. vet. J. 19: 21. 1978.
provided ample complementary explanations are given by the instructors of the course. The text could serve as one of the reference books in medical and veterinary school libraries.
Les manuels originent souvent des notes de cours polycopiees. Le livre du docteur Lang en est un exemple. Ce livre est divise en trois parties. La premiere, introduction a la chirurgie, inclut des informations tres elementaires sur les methodes chirurgicales: preparation, sutures, instruments, anesthesie, etc. La deuxieme partie traite de la description des techniques chirurgicales telles que laparatomie, splenectomie, nephrectomie, etc. Le troisieme volet s'interesse aux methodes du laboratoire de diagnostic et aux techniques de necropsie. Le titre du livre est quelque peu trompeur "tlements de chirurgies physiologiques chez le chien" aurait ete un titre plus approprie. Le texte est clair et souvent un peu trop succinct. Ce livre est destine A des etudiants en medecine et A ceux des 2e et 3e cycles. II pourrait etre utile A ces fins pourvu que des explications et des references supplementaires soient fournies aux etudiants durant les cours. L'ouvrage du docteur Lang serait une acquisition a envisager par les bibliotheques des facultes de medecine et de medecine veterinaire. L. DeRoth.
243
THE CANADIAN VETERINARY JOURNAL LA REVUE VPTE'RINAIRE CANADIENNE September-septembre 1978
Incidence of Clinical Coccidiosis in Chickens in the Ontario Veterinary Services Branch Records 1973-1977 ENG-HONG LEE AND D.K. ONDERKA*
INTRODUCTION
Coccidiosis is still being recorded as one of the most commonly diagnosed diseases of chickens in Canada (9, 10, I 1) despite millions of dollars being spent each year on anticoccidial drugs added in feed for its control. Records accumulated by the Ontario Veterinary Services Branch (VSB) during the period from 1973 to 1977 showed that clinical coccidiosis in Ontario was equally prevalent. These VSB records were analysed with a a view to gaining some information about the disease in the field. Use of some of the findings from these records in conjunction with drug rotation as a means of control of coccidiosis in chickens is discussed. MATERIALS AND METHODS
Results are mostly derived from the computerized data collected from materials submitted to all six regional laboratories of the Ontario Veterinary Services Branch in Brighton (144), Guelph (91), Kemptville (72), Huron Park (49), Ridgetown (40) and New Liskeard (10). The numbers in parenthesis indicate consignments or cases of clinical coccidiosis reported from each laboratory with a total of 406 during the five years from 1973 to 1977. In most cases, live or dead chickens were submitted but sometimes in referral cases of private practitioners or others, guts or fecal suspensions in potassium dichromate were also submitted. Diagnosis was based on clinical signs, gross lesions at postmortem examination, and the presence of parasites in intestinal or cecal scrapings. Efforts to identify species of coccidia were made
No. 9
inconsistently. As a consequence all coccidia were differentiated either as cecal or intestinal. Species identified in Guelph, appear to be similar to those reported recently in the U.S. (3), namely Eimeria acervulina, E. maxima, E. tenella and E. necatrix and E. brunetti. Data of the three other most frequently diagnosed diseases of chickens (Table I), one viral (Marek's) and two bacterial (necrotic enteritis and colibacillosis), were also plotted. They serve as internal sampling controls for detecting possible bias in the timing of submissions for diagnosis to the VSB laboratories at different months of the year. The chickens submitted were differentiated into three types: broilers, layers and others. The last type included the unrecorded, some breeders and both broilers and layers kept on hobby farms. RES ULTS
There were 18 consignments reported as infected with both cecal and intestinal coccidiosis decreasing the total number of consignments from 424 to 406 (Table 1). Four hundred and six is still the largest number among the four common poultry diseases reported here with Marek's disease (333), necrotic enteritis (219) and colibacillosis (88) ranked in descending order. Less than 2% (6/406 consignments) of these were diagnosed as infected with both necrotic enteritis and coccidiosis. The monthly incidence of clinical coccidiosis started *to increase in May, peaked in July, maintained relatively high levels until October, then declined to lower levels in the cold months (Figure 1). This trend was true for each of the five years from 1973 to 1977 except the decrease in June of 1974 and the peak in August of 1973. In order to show the trend more clearly, each of these monthly incidences was added to arrive at Figure 2. Figure 2 shows the cumulative incidence of clinical coccidiosis remained near 20 from November to May with 16 and 17 cases in December and April respectively. The incidence started to increase in May, rose to 39 in June and to 80 in July. The number then declined to 62 in August, 41 in September and 37 in October. This monthly distribution of the incidence of coccidiosis seemed to divide the year conveniently into two halves where the higher incidence (70%0 or
*Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario NIG 2WI (Lee) and Veterinary Services Branch, Ontario Ministry of Agriculture and Food, Box 3612, Guelph, Ontario NIH 6R8 (Onderka).
Can. vet. J. 19: 237-243 (September 1978)
237
TABLE I INCIDENCE OF THE FOUR MOST FREQUENTLY DIAGNOSED DISEASES OF CHICKEN IN THE Six REGIONAL LABORATORIES OF THE ONTARIO VETERINARY SERVICES BRANCH YEARS 1973-1977 IN VARIOUS TYPES OF CHICKENS Incidence
Type
Coccidiosis
37 Ca
Broilers
114 59 112 37 65
Layers
Others
lb C
Necrotic enteritis
Colibacillosis
53
141
53
156
31
9
4
124
47
26
2
333
219
88
6
333
219
88
6
I
C I
Sub Total 424 C+ I -18 Total 406 a C = cecal coccidiosis b I = intestinal coccidiosis 15
Marek's
283/406 consignments) occurred in the warmer six months between May and October and the lower incidence (30%) in the colder six months. For the warmer six months during the period from 1973 to 1976 (records for 1977 are not yet complete) the average temperature varied from 11.80 C in May to a high of 20.40 C in July and then declined to about 8.70 C in October. The average temperatures of the colder six months were 3.60C in November, a low of -5.60 C in January, and 6.10 C in April (Figure 2).
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5 .1
.
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*
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1974
15 10
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201
1973
15
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5
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FIGURE 1. Monthly distribution of the incidence of clinical coccidiosis of each of the five years from 1973 to 1977 recorded by the Ontario Veterinary Services Branch.
238
Coccidiosis N. enteritis
These figures were those of the Lake Ontario counties. In general they were about two degrees lower than those of Lake Erie and Niagara counties but one or two degrees higher than the rest of Southern Ontario (Monthly Records, Fisheries and Environment Canada). The monthly distribution of necrotic enteritis followed the same pattern as coccidiosis (Figure 2) with 64% (140/219 consignments) in the warmer months and 36% in the colder months. No similar trend in distribution was detected for Marek's disease or colibacillosis. No monthly fluctuation was apparent in the number of laying hens maintained between January 1976 to December 1977 in Ontario (Figure 2) (personal communication, Mr. Marcus Walker, Ontario Egg Producers' Marketing Board). The number of layers in Figure 2 represent at least 95% of all laying hens 24 weeks of age or older in Ontario. The maximum monthly fluctuation in broiler production in Canada for the six years from 1971 to 1976 was about 27% or (1-14.4/ 19.8) x 100 (Figure 2). The number 14.4 refers to the number of million of broilers produced in February 1976 (the lowest month) and 19.8 million in July (the highest month) of the same year (Canadian Poultryman, July supplement 1977). More than one third (209/609 million pounds) of all broilers produced in Canada in 1976 were raised in Ontario (personal communication, Dr. John P. Walker, Department of Animal and Poultry Science. University of Guelph).
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-52
FIGURE 2. Monthly distribution of the incidence of clinical coccidiosis and other frequently diagnosed chicken diseases in the Ontario Veterinary Services Branch records years 1973 to 1977. They are: clinical coccidiosis The average Marek's disease (0-O), necrotic enteritis (O O) and colibacillosis ) in Canada. The number of laying hens number of broilers produced in 1971 to 1975 (A--A) and in 1976 (Ain Ontario for the years 1976 and 1977 (+--.- +) were also superimposed. Numbers below the respective months of the year represent the averaged temperatures of the Lake Ontario counties from years 1973 to 1976. ........0
Infection among broilers occurred in birds as young as one week of age but 80% (112/140
consignments) of the infections occurred in three (Figure 3). The majority (58%) was concentrated in birds four to five weeks of age. The majority or 71% (91/142 consignments) of to seven week old chickens
the clinical coccidiosis among layers was found in birds four to 13 weeks of age (Figure 4). The proportion then decreased to 22% in the next 11 weeks. Infections were reported in birds of all age groups including a flock of two year old layers with cecal coccidiosis. The incidence of clinical coccidiosis among
239
40
30
z
w
20
0
z
10
2
6
4
8
10
12
14
16
18
20
22
24
36
368
WEEKS
FIGURE 3. Relation between incidence of clinical coccidiosis, intestinal (blank) and cecal (striped), and the age of broilers in the Ontario VSB records years 1973 to 1977. 20
r
15
w
u
z
0
w10
z
S
I
I
L 4
6
6
10
12
14
16
18
WEEKS
20
22
24
26
a8
10
12
n n,Fl;I 16 24 14
MONTHS
FIGURE 4. Relation between incidence of clinical coccidiosis, intestinal (blank) and cecal (striped), and age of layers in the Ontario VSB records years 1973 to 1977.
different age groups of other chickens was 61% (51/83 consignments) in the first ten weeks, 32% in the next eight weeks and became sporadic thereafter (Figure 5). A flock of two year old birds infected with coccidiosis (intestinal) was also reported. In almost all submissions a low mortality was observed. DISCUSSION
The monthly incidence curve in Figure 2 most likely represents the true trend in clinical cocci240
diosis among chickens raised in Ontario. The reasons are as follows: First, the trend was not influenced by the number of laying hens in Ontario because the latter showed no apparent monthly change (Figure 2). Second, even though fluctuation did occur in the number of broilers, the maximum monthly difference was 27% which could hardly account for the fivefold difference between the highest and lowest monthly incidence of clinical coccidiosis. Moreover, such difference occurred because of the unusually low number of broilers raised in the month of February. Otherwise, only slight monthly differences could be
15
z w 0 u Z
5
4
6
8
10
12
14
16
18
20
22
24
26
7
9
11
WEEKS
13
15
24
MONTHS
FIGURE 5. Relation between incidence of clinical coccidiosis, intestinal (blank) and cecal (striped), and age of other chickens in the Ontario VSB records years 1973 to 1977.
found in the number of broilers produced during the other 11 months of the year (Figure 2). Third, it was unlikely that farmers would send more of their sick chickens to the VSB laboratories but not to the private practitioners or laboratories for diagnosis in the warmer six months thus causing a rise in the incidence of clinical coccidiosis. If such bias existed, it could not explain why a similar trend did not occur for Marek's disease and colibacillosis (Figure 2). Fourth, the influence of the incidence of necrotic enteritis on that of clinical coccidiosis was negligible because less than 2% (6/406 consignments) of all clinical coccidiosis was diagnosed as also being infected by necrotic enteritis. Therefore, the trend of higher incidence of clinical coccidiosis in the warmer six months but lower in the colder six months was most likely true. Higher incidences of coccidiosis recorded between the months of May and October may be explained partly by the fact that the warmer (thus more humid) conditions favour oocyst sporulation. The same reason also seemed adequate to explain why all incidence of coccidiosis in the colder months, at least for those reported to the VSB laboratory in Guelph in 1976 and 1977, were reported from larger farms (Table II) capable of keeping the barn temperature and humidity rather constant year round. The marked difference in incidence of coccidiosis between the warmer and the colder months may be a useful piece of information for the chemotherapeutic control of coccidiosis. It is now evident that control of coccidiosis by drugs is becoming increasingly difficult, because of the emergence of drug resistant strains of coccidia refractory to one or many of the 19 anticoccidial drugs introduced since the 1940's (6, 8). Drug resistant strains of avian coccida have been reported in Canada (5). Presently, the only practical means of overcoming the problem of drug resistance is by rotating or switching drugs to a newly introduced drug or to an existing drug to which the coccidia
TABLE II INCIDENCE OF CLINICAL COCCIDIOSIS AMONG LARGE AND SMALL FARMS AS RECORDED BY THE ONTARIO VSB IN GUELPH FOR YEARS 1976 AND 1977 Incidence Months
Large farms
May to October
15
(5,000-60,000)
Small farms
12 (40-400)
chickens
Nov. to April
6 (3,000-18,000) chickens
chickens
0
are still sensitive. Clinical coccidiosis in chickens
may be better controlled if the timing of drug rotation was synchronized with the change in the incidence of coccidiosis between warmer and colder months. Changing of anticoccidial drugs near the end of April or early May might more effectively prevent clinical coccidiosis during the months of higher incidence. Changing again at the end of October or early November may be necessary to prevent unduly prolonged exposure, the main cause of drug resistance. It must be pointed out, however, that drug rotation without drug sensitivity tests sometimes may result in outbreaks rather than prevention (12). The relationship between the incidence of clinical coccidiosis and the age of the host shown in Figure 3 almost directly replicates that reported by Long (6). Long showed the mean number of oocysts per gram of litter started to increase when broilers were two weeks of age. The number then peaked among four week old broilers after which it decreased until it became negligible again at eight weeks. These two almost identical findings suggest that the number of oocysts in the litter may be the main cause of clinical coccidiosis in the field. Since it takes only five to six days for infections to show clinical signs, the peak infections among four week old broilers (Figure 3) likely resulted from ingestion of sporulated oocysts produced by themselves when they were two to three weeks of age.
241
Based on these findings a preventive measure for more effective control of coccidiosis among broilers may be feasible. The measure is to submit broilers two weeks of age or younger to the VS B or similar laboratories for diagnosis. If signs of coccidiosis or a large number of oocysts, particularly those of the more pathogenic species of E. tenella and E. necatrix, were found in these young birds, drug rotation should be immediately applied irrespective of the month of the year. Such preventive measures are particularly useful in broiler farms with a recent history of outbreak of clinical coccidiosis. Similar measures may be taken for young layers and other chickens. The fact that layers and other chickens were infected at all age groups, including birds as old as two years of age (Figures 4 and 5) suggests that the degree of immunity acquired varies among different flocks of birds (4). Such examples of older field flocks being susceptible to further (experimental) infections have been shown previously (2, 4). However, unlike the finding of Karlsson and Reid (4), some losses did occur in older birds submitted to the VSB laboratory in Guelph. Undoubtedly, in some instances other diseases might have also played a role in causing death. This and the relation of factors such as the size of farm operation, the quality of management, nutrition, and others, to clinical coccidiosis remain to be
investigated. Ideally, control of coccidiosis by drug rotation should be guided by drug sensitivity tests. However general availability of such tests presently is absent in Canada. As a consequence, drug rotation rather than a routine procedure, sometimes was practised only when high feed conversion or coccidiosis outbreaks among chickens were noticed. High feed conversion and outbreaks were two major reasons for submitting chickens to the VSB laboratories. Guidance for the logical rotation to, and selection of, anticoccidial drugs has been previously suggested by Reid (7), Ryley and Betts (8) and Eckman (1). However, there is no general guidance as to when a drug should be routinely rotated. The timing of high and low monthly incidence of clinical coccidiosis reported here perhaps can serve as a logical guide. SUMMARY
The incidence of clinical coccidiosis recorded by the six regional laboratories of the Ontario Veterinary Services Branch from years 1973 to 1977 was analysed. Seventy percent (283/406) of the consignments was distributed between May to October and 30% from November to April, with the highest incidence of 80 consignments in July and the lowest, 16 consignments, in December. Among broilers, infections occurred in birds as young as one week of age but 80% (112/140 consignments) were found in birds three to seven weeks of age with the majority (58%) concentrated in the four to five week old birds. 242
Although the higher incidence of clinical coccidiosis among layers and other chickens was in the younger birds (four to 12 weeks), infections were recorded in birds of all ages including two flocks of two year olds. Possible use of these data with drug rotation for better control of coccidiosis in chickens is discussed. Rt-S UM t
Les auteurs ont analyse l'incidence naturelle de la coccidiose, en Ontario, au cours de la periode de 1973 a 1977, en se basant sur les donnees disponibles dans les six laboratoires regionaux du Service veterinaire de cette province. Ils realiserent que 70% des envois (283/406) avaient eu lieu entre les mois de mai et d'octobre et que 30% avaient eu lieu entre les mois de novembre et d'avril. Le plus grand nombre d'envois, soit 80, se fit en juillet et le nombre le moins eleve, soit 16, en decembre. On diagnostiqua la coccidiose chez des poulets ages de seulement une semaine; 80% des cas affectaient cependant des sujets ages de trois a sept semaines et repartis dans 112 des 140 envois; la majorite de ces cas, soit 58%, impliquait neanmoins des sujets ages de quatre a cinq semaines. Meme si l'incidence la plus elevee de coccidiose clinique chez les pondeuses et les autres poulets s'observait chez les plus jeunes sujets de ces groupes (quatre a 12 semaines), on en enregistra des cas chez des sujets de tous les ages, y compris certains de deux troupeaux de pondeuses agees de deux ans. Les auteurs commentent en dernier lieu l'utilisation possible de ces donnees en rapport avec la rotation de la medication, dans le but d'obtenir un meilleur contrBle de la coccidiose aviaire. ACKNOWLEDGM ENTS
We thank Drs. J.P Lautenslager and K.R. Mittal for their assistance in the preparation of this manuscript and Dr. S.W. Martin for suggesting Figure 1. The partial financial support of the National Research Council and the Ontario Ministry of Agriculture and Food funded through Dr. M.A. Fernando and the Department of Pathology, University of Guelph is gratefully acknowledged. REFERENCES 1. ECKMAN, M.K. Evaluating anticoccidials in poultry in the United States. Practg. Nutr. 10: 14-21. 1976. 2. EDGAR, S.A. Coccidiosis of chickens and turkeys and control by immunization. Avicult. Mod. Mem. XI
Cong. Mondial Avicultura. pp. 415-421, 679. 1958. 3. JEFFERS, T.K.Eimeria acervulina and E. maxima: Incidence and anti-coccidial drug resistance of isolants in major broiler-producing areas. Avian Dis. 18: 331-342. 1974. 4. KARLSSON, T. and W.M. REID. Prevalence of Eimeria acervulina, E. necatrix, E. brunetti and E.
5. 6.
7.
8.
tenella in Georgia (USA) as demonstrated by immunity challenge techniques. Br. Poult. Sci. 18: 497-501. 1977. LEE, E.-H. and M.A. FERNANDO. Drug resistance in coccidia: A robenidine-resistant strain of Eimeria tenella. Can. J. comp. Med. 41: 466-470. 1977. LONG, P.L. Chickens: The control of coccidiosis. Span. pp. 26-28. Jan. 1977. REID, W.M. Anticoccidials: Differences in day of peak activity against Eimeria tenella. In Proceedings of the Symposium on Coccidia and Related Organisms. pp. 1 19-134. Guelph, Ontario: University of Guelph. 1973. RILEY. J.F. and M.J. BETTS. Chemotherapy of
ANALYSE DE VOLUME/ BOOK REVIEW Animal Physiologic Surgery. C. Max Lang. Published by Springer-Verlag, New York. 1976. 180 pages. Price $10.80.
Textbooks often develop from course handouts or mimeographed manuals. As mentioned in the preface, Dr Lang's text originates from these sources. The book is divided into three parts. The first, Introduction to Surgery, includes very basic information on operating room procedures, sutures and instruments, wound healing, anesthesia, and water and electrolyte balance. The second part deals with surgical instructions and some clinical consideration of nine surgical procedures, such as laparatomy, splenectomy, nephrectomy, etc. The third segment relates to laboratory methods used for the evaluation of the patient and postmortem techniques. The title of the book is misleading; "Elements of Physiological Surgery in the Dog" would have been more appropriate. The text is clear and succinct, even though the reader may get the impression that it has been hastily written. The book is intended for first year medical students and graduate students in physiology. It should serve that purpose
9. 10.
1l. 12.
chicken coccidiosis. Adv. Pharmac. Chemother. 11: 221-293. 1973. STEPHEN, L.E. Poultry diseases diagnosed in Canadian laboratories for the year 1973. Can vet. J. 16: 65-70. 1975. STEPHEN, L.E. Poultry diseases diagnosed in Canadian laboratories for the year 1974. Can. vet. J. 17: 145-149. 1976. STEPHEN, L.E. Poultry diseases diagnosed for Canadian laboratories for the year 1975. Can. vet. J. 18: 297-300. 1977. WEBER, L.J. Clinical coccidiosis. Can. vet. J. 19: 21. 1978.
provided ample complementary explanations are given by the instructors of the course. The text could serve as one of the reference books in medical and veterinary school libraries.
Les manuels originent souvent des notes de cours polycopiees. Le livre du docteur Lang en est un exemple. Ce livre est divise en trois parties. La premiere, introduction a la chirurgie, inclut des informations tres elementaires sur les methodes chirurgicales: preparation, sutures, instruments, anesthesie, etc. La deuxieme partie traite de la description des techniques chirurgicales telles que laparatomie, splenectomie, nephrectomie, etc. Le troisieme volet s'interesse aux methodes du laboratoire de diagnostic et aux techniques de necropsie. Le titre du livre est quelque peu trompeur "tlements de chirurgies physiologiques chez le chien" aurait ete un titre plus approprie. Le texte est clair et souvent un peu trop succinct. Ce livre est destine A des etudiants en medecine et A ceux des 2e et 3e cycles. II pourrait etre utile A ces fins pourvu que des explications et des references supplementaires soient fournies aux etudiants durant les cours. L'ouvrage du docteur Lang serait une acquisition a envisager par les bibliotheques des facultes de medecine et de medecine veterinaire. L. DeRoth.
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