Some Physiological Effects of Eimeria acervulina, E. brunetti, and E. mivati Infections in Young Chickens1 J. F . STEPHENS, 2 W . J. BORST 3 AND B . D . BARNETT
Poultry Science Department, Clemson University, Clemson, South Carolina 29631 (Received for publication January 14, 1974)
ABSTRACT Selected physiological effects of coccidiosis in young chickens were studied in a series of nine trials involving three species of Eimeria. Four-week-old chicks were inoculated individually with a number of sporulated oocysts sufficient to cause morbidity with minimum mortality. Eight to ten inoculated and an equal number of uninoculated chicks were examined at pre-determined intervals for 18 to 21 days. Weight gains of the chicks infected with E. acervulina were depressed from the fifth day postinoculation until the termination of each of two trials. There was no significant difference between average total weight gains of chicks infected with E. brunetti and control chicks at the termination of two trials. The effect of E. mivati infection upon weight gain was, in general, less severe than that of either E. brunetti or E. acervulina. Each species of Eimeria caused a decrease in light absorbance of the plasma of infected chicks. E. acervulina had a more severe effect upon light absorbance of the plasma than did either E. brunetti or E. mivati. All three species studied caused an increase in acidity of the digestive tract at the principal site of infection. Chicks infected with E. acervulina had the lowest intestinal pH values recorded. Significant differences between the erythrocyte sedimentation rates and packed erythrocyte volume of infected chicks and control chicks were observed in individual trials; however, when data from the series of three trials conducted with each species were combined and analyzed, no significant differences between means representing control and infected chicks were found. Increased buffy blood coat values caused by E. acervulina infection were less than those caused by E. brunetti but greater than those caused by E. mivati. Infection of E. mivati had little effect on buffy blood coat values. POULTRY SCIENCE 53: 1735-1742, 1974
INTRODUCTION OCCIDIOSIS continues to be one of the most economically important diseases of poultry. Extensive research has been reported on the pathogenicity and the life cycles of the causative agents, and on the transmission, prevention, and treatment of the disease; but few reports have been found concerning physiological alterations induced by the infections. Natt and Herrick (1955) observed a decrease of approximately 50% in erythrocyte count and in hematocrit values on the fifth
C
1. Published with the approval of the Director, S.C. Agricultural Experiment Station as technical contribution no. 1135. 2. Present address: Department of Poultry Science, The Ohio State University, Columbus, Ohio 43210 3. Present address: 4635 Poplar, Richton, Illinois 60471
and sixth days of an infection of E. tenella. In later studies they found decreases in percentage of corpuscular volume and total blood volume, but no change in the plasma volume during the hemorrhagic phase of the disease (Natt and Herrick, 1956). Natt (1959) reported that E. tenella infection caused a reduction in hemoglobin concentration, red blood cell count and packed cell volume on days five through seven postinoculation. Similarly, Bierer et al. (1964) reported packed cell volume below 26% and other evidence of anemia in chickens infected with cecal coccidiosis. All portions of the alimentary tract in chickens are normally acid, with the lowest pH recorded in the gizzard and the highest in the ileum (Farner, 1942). Much variation exists in the pH values reported (Buckner et al., 1944; Heller and Penquite, 1936). Buckner et al. (1944) reported that pH values of the contents of the intestinal tract and
1735
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J. F. STEPHENS, W. J. BORST AND B. D. BARNETT
those of scrapings from the mucosa were similar. He could determine no differences in the pH of the tract due to either sex or age. The effects of E. necatrix infection upon pH of the intestinal contents and selected blood values were reported by Stephens (1965). The pH of the intestinal contents was significantly decreased on the sixth and ninth days postinoculation of a severe infection. On the sixth day, increases in the erythrocyte sedimentation rate and in the percentage of light transmittance of plasma were observed. Stephens et al. (1967) reported that some of the physiological effects of coccidiosis associated with E. maxima infection were similar to those caused by E. necatrix infection, however, the increase in light transmittance of the plasma exceeded that of the plasma from chicks infected with E. necatrix. Hemoconcentration was observed on day 14 postinoculation with E. maxima. E. acervulina is, in general, more pathogenic than E. mivati, but less pathogenic than E. brunetti (Edgar and Seibold, 1964). Failure of E. acervulina to demonstrate any pronounced pathogenicity has been reported by several investigators (Becker, 1940; Dickinson, 1941; Morehouse and McGuire, 1958). Morehouse and McGuire (1958) reported that the degree of weight loss sustained by E. acervH/ina-infected chicks increased in proportion to the number of oocysts given. Single and multiple doses of 5 million or more E. acervulina oocysts caused up to 75% mortality among infected chicks. Reid and Johnson (1970) reported severely depressed weight gains for 7 days postinoculation in birds inoculated with 1,000,000 oocysts of E. acervulina. E. mivati is moderately pathogenic and causes gross changes in the anterior portion of the small intestine by the fourteenth day postinoculation (Edgar and Seibold, 1964). Hyperemia and edema are observed in severely affected regions of the intestine of
experimentally infected birds; and, if death occurs, it is usually on the sixth or seventh day postinoculation (Edgar and Seibold, 1964). Johnson and Reid (1971) reported that moderate infections (50,000 oocysts/chick) of E. mivati caused weight depression at seven, but not 28, days postinoculation; severe infections caused weight depression at both seven and 28 days postinoculation. The present study was designed to determine some of the effects of coccidiosis caused by three species (E. acervulina, E. brunetti, and E. mivati) upon young chickens. MATERIALS AND METHODS Nine trials involving a total of 1548 chicks were conducted to study the effects of E. acervulina, E. brunetti and E. mivati on selected physiological factors; three trials were conducted with each species. Male broiler chicks were used in all of the trials except trials 8 and 9 in which equal numbers of male and female chicks were used. One-day-old chicks, obtained from a single source within the state, were used in all of the trials. The chicks were reared in an electrically-heated, wire-floored starter battery until four weeks of age. Water and feed were supplied ad libitum throughout the trials, and a practical-type broiler ration containing no coccidiostat was fed. At four weeks of age, the chicks were wing-banded, weighed, randomly assorted into two groups, and transferred to grower batteries. Each trial conducted with E. acervulina or E. brunetti involved 180 chicks. The three trials conducted with E. mivati involved varying numbers of chicks depending on the number of oocysts available; the first (trial 7 of the series) involved the use of 168 chicks, the second involved 158, and the third involved 142 chicks. Chicks were inoculated at 4 weeks of age by introducing the sporulated oocysts directly into the crop with a pipette. One-half of the chicks in each trial were left uninoculated
PHYSIOLOGICAL EFFECTS OF EIMERIAE
1737
to serve as controls; the remaining chicks were inoculated with a pre-determined number of sporulated oocysts. The number of oocysts given was based on estimates of the number necessary to cause severe morbidity and minimum mortality. In trial 1, the chicks were individually inoculated with 1,000,000 sporulated oocysts of E. acervulina and in trials 2 and 3 with 1,500,000 oocysts. Approximately 150,000 oocysts of E. brunetti were given to each chick in trial 4, and 100,000 to each chick in trials 5 and 6. Chicks in trial 7 were inoculated with 1,000,000 oocysts of E. mivati and in trials 8 and 9 with 500,000 oocysts.
involving E. acervulina, contents of the colon and ileum in those involving E. brunetti, and of the duodenum in the study of E. mivati. The contents of that portion of the alimentary tract being studied were manually expressed into a small beaker, and the pH was determined with a Beckman Model 76 pH meter. The intestine of each chick was also examined visually for damage. A scoring system based on visual observation of damage to the intestine was used as a criterion to estimate severity of infection. A score of 0 indicated an absence of visual damage, 2 indicated a moderate degree of damage, and 3 indicated severe damage to the intestine.
Ten inoculated and ten control chicks were randomly selected and examined at pre-determined intervals in each of the trials, except trial 8 in which eight each of the inoculated and control chicks were examined. Blood samples were taken by cardiac puncture, using 20-gauge needles and 2-ml. syringes previously rinsed in a 25% solution of sodium citrate. Erythrocyte sedimentation rate (ESR) was recorded as the number of mm. which the erythrocytes settled in 1 hr. in Wintrobe tubes held at a 45° angle, as suggested by Sturkie and Textor (1958). Packed erythrocyte volume (PEV) and buffy blood coat (BC) were recorded as percentages of the total blood volume after the Wintrobe tubes were centrifuged for 30 min. at 2,000
The effects of the infections on weight gain, pH of the intestinal contents, ESR, PEV, BC value and light absorbance of the plasma were measured at intervals indicated in Tables 1-6. Weight gains represent the period between day of inoculation and time of examination. Weight gain data representing chicks used in the third trial was accidentally destroyed. Statistical procedures outlined by Steel and Torrie (1960) were used to analyze the data.
8The plasma from five blood samples (4 in trial 8) was pooled and its light absorption measured at 500 mix., so that two pooled samples from control chicks and two from infected chicks were examined at each interval. After the blood samples were drawn, the chicks were sacrificed and the pH of the intestinal contents from that portion of the alimentary tract normally affected by the species of coccidia being studied was determined. The pH of the contents of the jejenum and duodenum were measured in the trials
RESULTS AND DISCUSSION The characteristic symptoms of intestinal coccidiosis reported by several investigators (Tyzzer et al., 1932; Levine, 1942; Edgar and Seibold, 1964) were seen in varying degrees in this study. The infected chicks were observed standing huddled with wings drooping and feathers ruffled. Bloody droppings were seen during the acute phases of the infections. The most characteristic observation upon necropsy was enteritis. The effect of E. acervulina infection upon weight gain in this study was similar to that reported by Morehouse (1956). The average weight gain of the inoculated chicks during the 20-day postinoculation period was approximately 85% of that of the uninoculated chicks (Table 1). The greater intestinal damage of E. acervulina infection on days 5 and
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J. F. STEPHENS, W. J. BORST AND B. D. BARNETT
TABLE 1.— Weight gain depression' and intestinal damage caused by Eimeria acervulina infection Trial 22
Trial l 2 Days postinoculation
Weight gain3
Intestinal damage score 4
% 3 5 7 9 12 15 18 20
90.1 71.9* 63.3** 75.2** 77.0** 87.5* 75 9** 84.2**
Trial 3 2
Weight gain3
Intestinal damage score 4
Intestinal damage score 4
Ave.
%
Ave.
Ave.
0.0 1.7 1.8 1.4 0.2 0.1 0.1 0.0
80.4** 60.8** 61.4** 78.6* 67.4** 92.5 81.5* 86.7**
0.2 2.4 2.5 1.3 1.2 0.2 0.0 0.0
0.8 2.3 2.7 1.8 1.3 1.0 0.1 0.0
'Percentages followed by * and ** represent significant (P < .05) and highly significant (P < .01) weight gain depressions. 2 Each chick was inoculated with 1,000,000 oocysts in trial 1. Each chick was inoculated with 1,500,000 oocysts in trials 2 and 3. 3 Expressed as percent of average gain of corresponding uninoculated chicks. "Values represent average scores for 10 chicks at each interval. A score of 0 indicates no damage; 3 indicates severe damage. 7 in trial 2 than in trial 1 obviously resulted from the administration of more oocysts per chicks in the second trial (Table 1). The smallest average daily weight gains of chicks infected with E. brunetti occurred between the sixth and eighth day postinoculation in trials 4 and 5 (Table 2). At the termination of trials 4 and 5, there was no significant difference in total weight gains of the inoculated and control chicks. However, chicks inoculated with a larger number of E. brunetti oocysts in trial 6 gained significantly less weight (P < .01) than did the control chicks throughout the trial (Table 2). The portion of the alimentary tract in which sporozoites are released in E. brunetti infection is the large intestine (Levine, 1942). Damage to the large intestine in these trials was difficult to evaluate; for this reason, the intestinal damage scores of chicks infected with E. brunetti were not very reliable as an indication of the severity of the infection. However, the highest intestinal damage scores were recorded on the sixth day postinoculation in all trials involving this species (Table 2). The effect of E. mivati infection upon
weight gain was, in general, less severe than that of either E. brunetti or E. acervulina. However, when chicks were inoculated with 1,000,000 oocysts of E. mivati per bird in trial 7; the effect upon weight gain was severe. Weight gains of the inoculated chicks were significantly depressed (P < .01) from the first through twentieth day postinoculation (Table 3). When the dosage per bird was reduced to 500,000 oocysts in trials 8 and 9, the effect upon weight gain was less severe, particularly, during the first week of the infection (Table 3). Chicks infected with E. mivati had higher average intestinal damage scores on the sixth through the tenth day postinoculation than did the chicks infected with E. brunetti (Tables 2, 3). Chicks infected with E. acervulina suffered a more chronic type of illness than did those given either E. mivati or E. brunetti as indicated by intestinal damage scores and weight gains (Tables 1-3). The disease, regardless of species of Eimeria involved, caused a significant decrease in light absorbance of the plasma of infected chicks at some time in all trials. Of the three species studied, E. acervulina had a more severe effect on the light absorbance of the
1739
PHYSIOLOGICAL EFFECTS OF EIMERIAE
TABLE 2.— Weight gain depression1 and intestinal damage caused by Eimeria brunetti infection
Weight gain 3
Intestinal damage score 4
Ave.
%
Ave.
%
Intestinal damage score 4 Ave.
0.0 1.5 0.6 0.0 0.0 0.0 0.0 0.0
47.1** 11.3** 30.4** 73.2** 65.8** 94.1 81.5* 89.9
0.3 1.8 0.2 0.0 0.0 0.0 0.0 0.0
-84.0** 9 9** -13.2** 49.8** 52.6** 45.6** 64.1**
0.3 0.6 0.1 0.0 0.0 0.0 0.0
Days postinoculation
Weight gain3
Intestinal damage score 4
% 4 6 8 11 14 16 18 21
44.7** -j j * *
0.9** 58.2** 60.7** 81.1 74 7** 88.2
Trial 6 2
Trial 5 2
Trial 4 2
Weight gain3
'Percentages followed by * and ** represent significant (P < .05) and highly significant (P < .01) weight gain depressions. 2 Each chick was inoculated with 100,000 oocysts in trial 4. Each chick was inoculated with 150,000 oocysts in trials 5 and 6. 3 Expressed as percent of average gain of corresponding uninoculated chicks. "Values represent average scores for 10 chicks at each interval. A score of 0 indicates no damage; 3 indicates severe damage. TABLE 3.— Weight gain depression' and intestinal damage caused by Eimeria mivati infection Trial 7 2 Days postinoculation 1 3 6 8 10 14 20
Trial 82
Weight gain3
Intestinal damage score 4
% -169.8** -46.3** 12.8** 37.2** 85.5 67.2** 77.8**
Trial 92 Weight gain3
Intestinal damage score 4
Ave.
%
Ave.
0.0 0.5 2.3 0.8 0.4 0.3 0.1
153.4 111.8 45.8** 54.4** 83.3 79.6* 91.6*
0.0 2.1 2.5 2.1 0.9 0.1 0.0
Weight gain3
Intestinal damage score 4
Ave.
%
0.0 0.1 2.1 1.2 0.3 0.0 0.0
106.8 87.8 81.9* 85.0 98.0 114.0 91.6
'Percentages followed by * and ** represent significant (P < .05) and highly significant (P < .01) weight gain depressions. 2 Each chick was inoculated with 1,000,000 oocysts in trial 7. Each chick was inoculated with 500,000 oocysts in trials 8 and 9. 3 Expressed as percent of average gain of corresponding uninoculated chicks. "Values represent average scores for 8 chicks at each interval. A score of 0 indicates no damage; 3 indicates severe damage.
plasma than did either E. brunetti or E. mivati, as indicated in Tables 4, 5, and 6. Light absorbance of the plasma of chicks infected with E. acervulina was significantly decreased on the fifth through the ninth day postinoculation; average light absorbance of the plasma of inoculated chicks on the seventh day postinoculation was about 50% of that of the uninoculated chicks (Table 4). Light absorbance of the plasma of chicks
infected with E. brunetti or E. mivati was significantly decreased in two of the three trials on the sixth day postinoculation, but was not significantly affected in more than one of three trials at any other time of examination (Tables 5, 6). The plasma of infected chicks lacked normal pigmentation and could be differentiated from that of the uninoculated birds by visual examination on the fifth or sixth day postino-
1740
J. F. STEPHENS, W. J. BORST AND B. D.
TABLE 4.—Effects
1 2
of Eimeria acervulina infection on young chicks—averages of three trials'
Erythrocyte sedimentation rate (mm./hr.)
1
Packed erythr ocyte volume (%)
Buffy blood coat (%)
Light absorbance of plasma
pHof intestinal contents
Days postinoculation
Control
Infected 2
Control
Infected 2
Control
Infected 2
Control
Infected 2
Control
Infected 2
1 3 5 7 9 12 15 18
23.88 25.60 25.74 25.93 22.08 24.42 24.00 23.85
25.00 23.18(1) 25.90 25.27 21.67 24.70(1) 23.62(1) 21.22(1)
21.15 22.27 21.15 21.40 22.17 21.37 20.93 22.15
20.88 22.10 20.90 21.58 20.70(1) 20.80 20.70 22.42
.85 .92 .90 .92 .92 .92 .85 .98
.87 .87 .82 1.02(1) 1.15(2) 1.04 1.02(1) .88(1)
.712 .773 .727 .804 .767 .742 .750 .773
.712 .798 .401(3) .403(3) .535(2) .635 .733 .748
6.13 6.08 6.02 5.98 6.31 6.28 6.18 6.11
6.02 5.90(1) 4.96(3) 5.52(2) 5.86(1) 6.09 6.11 6.01
Number in parenthesis indicates number of trials in which value was significantly different from corresponding control value. Each chick was inoculated with 1,000,000 oocysts in trial 1; each chick was inoculated with 1,500,000 oocysts in trials 2 and
TABLE 5.—Effects
2
BARNETT
of Eimeria brunetti infection on young chicks—averages of three trials1
Erythrocyte sedimentation rate (mm./hr.)
Packed erythrocyte volume (%)
Buffy blood coat (%)
pHof intestinal i:ontents
Light absorbance of plasma
Days postinoculation
Control
Infected 2
Control
Infected 2
Control
Infected 2
Control
Infected 2
Control
Infected 2
1 3 6 8 11 14 16 18 21
20.60 20.53 21.40 23.41 21.00 20.62 21.88 23.06 19.75
19.61(1) 19.63 19.29(1) 22.85(1) 23.20(1) 21.24 21.85(1) 22.54 22.59(1)
21.76 21.21 22.03 20.82 19.61 20.74 20.70 21.20 21.54
23.33 21.23 23.13 20.56(1) 20.08 20.25 20.55(1) 20.60 21.00
.91 .93 .86 .92 .91 .76 .85 .81 .91
1.06 .98 .99 .98(1) 1.21(1) .84 .89 .88 .97
.880 .792 .842 1.006 .809 .780 .793 .809 .720
.687 .611 .460(2) .690(1) .639 .631 .800 .768 .673
6.94 6.71 7.02 7.03 7.01 7.09 7.14 7.14
6.59 6.34 5.84(1) 5.97(1) 7.24 6.85 7.09 6.80
—
—
Number in parenthesis indicates number of trials in which value was significantly different from corresponding control value. Each chick was inoculated with 100,000 oocysts in two trials and with 150,000 oocysts in the third.
culation. Stephens (1965) suggested that the chicks may be unable to absorb pigments during the hemorrhagic phase of coccidiosis caused by E. necatrix; this would explain the lack of pigmentation of the plasma. The fact that E. brunetti infection caused a less drastic effect on light absorbance of the plasma than did either of the other species used in this study may be explained by the fact that E. brunetti causes damage to the large intestine where little absorption takes place and has little or no effect on the mucosa of the small intestine where there is greater absorption of pigments. Coccidiosis caused an increase in acidity of the digestive tract at the principal site of
infection. Chicks infected with E. acervulina had the lowest intestinal pH values recorded; the average pH value was 4.96 on the fifth day postinoculation (Table 4). The pH of the intestinal contents of the duodenum and jejunum of the chicks infected with E. acervulina was more acid than those of the same segments of the controls throughout the twelfth day postinoculation period, but the difference was statistically significant (P < .01) in all three trials only on the fifth day (Table 4). The pH of the contents of the large intestine of chicks infected with E. brunettiwas also lower than that of the control chicks throughout the trials, but a statistically significant reduction in pH occurred only in
1741
PHYSIOLOGICAL EFFECTS OF EIMERIAE
TABLE 6.—Effects
of Eimeria mivati infection on young chicks—averages of three trials'
Erythrocyte sedimentation rate (mm./hr.)
Packed erythrocyte volume (%)
Buffy blood coat (%)
Light absorbance of plasma
pHof intestinal icontents
Days postinoculation
Control
Infected 2
Control
Infected 2
Control
Infected 2
Control
Infected 2
Control
Infected 2
1 3 6 8 10 14 20
22.23 24.37 21.62 22.45 22.75 21.61 21.75
21.16 21.89(1) 22.61(1) 23.23 22.85(1) 20.79 20.18(1)
21.75 20.71 21.77 19.93 20.75 21.88 20.10
22.00 20.85(1) 20.71(1) 20.40 20.85 21.51 21.08(1)
.96 .79 .94 .74 .88 1.03 1.00
1.16(1) .91 .90 .82 .95 1.18(2) 1.04
.978 1.012 .785 .957 .937 .892 .901
.981(1) •795(1) .495(2) .713(1) .778(1) .948(1) .818
6.36 6.38 6.40 6.31 6.46 6.45 6.37
5.80(1) 6.20(1) 5.58(2) 5.62(2) 6.13(1) 6.24 6.44
Number in parenthesis indicates number of trials in which value was significantly different from corresponding control value. Each chick was inoculated with 1,000,000 oocysts in the first trial; each chick was inoculated with 500,000 oocysts in the second and third trials.
the third trial in which each chick was inoculated with 150,000 sporulated oocysts (Table 5). The pH of the intestinal contents of chicks infected with E. brunetti returned to approximately that of the controls on the eleventh day postinoculation (Table 5). On days six and eight postinoculation of trials involving E. mivati, infected chicks in two of the three trials had significantly lower pH values of intestinal material than did the control chicks (Table 6). A possible explanation for the change in the hydrogen ion concentration of the digestive tract during the hemorrhagic phase of coccidiosis is the destruction of the cells of the small intestine which produce secretin. This hormone, formed in the walls of the small intestine, determines the quantity of pancreatic juice that is secreted (Sturkie, 1965). According to Sturkie, the hydrogen ion concentration of the digestive tract is dependent upon the amount of hydrochloric acid secreted into the proventriculus; and the pancreatic juice acts to neutralize this acid in the tract. Therefore, if the production of secretin is reduced, less pancreatic juice may be secreted; and, consequently, the tract may become more acid. Stephens (1965) observed a decrease in the hydrogen ion concentration of the digestive tract during E. necatrix infection, and suggested that it might be due to
the absence of feed in the intestine, tissue degradation in the intestine or the absence of the buffering effect of the feed. Significant differences in ESR of infected chicks were observed in this study in individual trials, regardless of species of Eimeria involved. However, the changes in ESR on specific days were not always reproducible in succeeding trials. When data from the series of three trials conducted with each species was combined and analyzed statistically, no significant (P = .05) differences between means representing ESR of infected and control chicks were found. Natt and Herrick (1955) observed a decrease of approximately 50% in hematocrit values on the fifth and sixth day of an infection of E. tenella; no effect on PEV of this magnitude was observed following inoculation of chicks with E. acervulina, E. brunetti or E. mivati. Statistically significant differences in PEV between infected and non-infected chicks were seldom observed (Tables 4, 5, 6). Average BC values of E. acervulina-infected chicks exceeded those of the controls on the seventh through the fifteenth day postinoculation (Table 4). BC values of chicks infected with E. brunetti were higher than those of the control chicks from the first through twenty-first day but the difference
1742
J. F. STEPHENS, W. J. BORST AND B. D. BARNETT
was statistically significant (P < .05) only on days 8 and 11, and in only one trial each day (Table 5). Infection of E. mivati caused no statistically significant change in BC values (Table 6). There was no mortality among chicks infected with E. acervulina and only one death attributable to E. mivati in three trials. Chicks infected with E. brunetti in trial 5 suffered 10% mortality; 6.5% of the infected chicks died in trial 6. REFERENCES Becker, E. R., 1940. Coccidiosis of domestic birds, with special reference to the common fowl. Vet. Med. 35: 401-407. Bierer, B. W., T. H. Eleazer and D. E. Roebuck, 1964. Hematologic findings associated with some common diseases of poultry. J. Am. Vet. Med. Ass. 145: 141-143. Buckner, G. D., W. M. Insko and A. H. Henry, 1944. Does breed, age, sex or laying condition affect the pH of the digestive tract system of chickens? Poultry Sci. 33: 457-458. Dickinson, E. M., 1941. The effects of variable dosage of sporulated Eimeria acervulina oocysts in chickens. Poultry Sci. 20: 413-424. Edgar, S. A.,andC.T. Seibold, 1964. Anew coccidium of chicks, Eimeria mivati sp.n. (Protozoa: Eimeriidae) with details of its life history. J. Parasitol. 50: 193-204. Farner, D. S., 1942. The hydrogen ion concentration in avian digestive tracts. Poultry Sci. 21: 445-450. Heller, V.G., and R.Penquite, 1936. Effect of minerals and fiber on avian intestinal pH. Poultry Sci. 15: 397-399. Johnson, J., and W. M. Reid, 1971. Pathogenicity of Eimeria mivati in light and heavy coccidial infections. Poultry Sci. 50: 1202-1205. Levine, P. P., 1942. A new coccidium pathogenic for chicks, Eimeria brunetti. Cornell Vet. 33: 430-439.
Morehouse, N. F., 1956. Morbidity and mortality among chickens infected with large numbers of the intestinal coccidium, Eimeria acervulina. J. Parasitol. 42 (No. 4, Sec. 2): 24. Morehouse, N. F., and W. C. McGuire, 1958. The pathogenicity of Eimeria acervulina. Poultry Sci. 37: 665-672. Natt, M. P., 1959. The effect of cecal coccidiosis on the blood cells of the domestic fowl. 3. The changes in the leucocyte picture during the course of the infection. Exptl. Parasitol. 8: 182-187. Natt, M. P., and C. A. Herrick, 1955. The effect of cecal coccidiosis on the blood cells of the domestic fowl. 1. A comparison of the changes in the erythrocyte count resulting from hemorrhage in infected and mechanically bled birds. Poultry Sci. 34: 11001106. Natt, M. P., and C. A. Herrick, 1956. The effect of cecal coccidiosis on the blood cells of the domestic fowl. 2. The changes in the blood volume during the course of the infection. Poultry Sci. 35: 311-316. Reid, W. M., and J. Johnson, 1970. Pathogenicity of Eimeria acervulina in light and heavy coccidial infections. Avian Dis. 14: 166-171. Steele, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Co., N.Y. Stephens, J. F., 1965. Some physiological effects of coccidiosis caused by Eimeria necatrix in the chicken. J. Parasitol. 51: 331-335. Stephens, J. F., L. M. Kowalski and W. J. Borst, 1967. Some physiological effects of coccidiosis caused by Eimeria maxima in young chickens. J. Parasitol. 53: 176-179. Sturkie, P. D., and K. Textor, 1958. Sedimentation rate of erythrocytes in chickens as influenced by method and sex. Poultry Sci. 37: 60-63. Sturkie, P. D., 1965. Avian Physiology. Cornell University Press, Ithaca, N.Y. Tyzzer, E. E., H. Theiler and E. E. Jones, 1932. Coccidiosis in gallinaceous birds. II. A comparative study of species of Eimeria in the chickens. Amer. J. Hyg. 15: 319-393.
NEWS AND NOTES (Continued from page 1734) transportation and warehouse services; and emergency preparedness functions and activities assigned to A.M.S. Mr. Blum, a native of Terryville, Connecticut, has
been with the U.S.D.A. since 1939, when he was employed as an Agricultural Economist in Upper Darby, Pennsylvania. He came to Washington in 1942 to work with wartime food marketing programs, then
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