/J r. vl'l.j. ( I 9 7 7), 133, 4 71
PROPOSED LIFE CYCLE OF EIMERIA ZUERNII By P. H. G . STOCKDALE Animal Pathology Division, H ealth of Animals Branch Agriculture Canada, Animal Diseases Research institute ( W) P.O. Box 640, Lethbridge, Alberta, Canada
SU MMARY
Ten bull ca lves, three months o ld or less, were infected with oocysts of Eimeria wemii. At post-mortem examiria tion large sch izonts were found in the lower ileum and small schizonts were present in the colon and caecum. Gametogony occurred in the co lon and caecum. The life cycle of E. zuemii apparently contains at least two sch izogonous generations before gametogony.
INTRODUCTION
Davis & Bowman (J 95 7) described the endogenous development of E. w emii in experimentally infected cattle. They reported that schizonts were seen from two to 19 days after inoculation in the upper, middle and lower portions of the small intestine and in the caecum and colo n. They found macrogametes and oocysts in the lower small intes tine, caecum a nd colon. In the work described here calves were infected with E. wemii and examined post mortem for the presence of the protozoan. MATERIALS AND METHODS
Ten Holstein (Fries ian ) bull calves were infected with 600000 oocysts of E. zuemii by stomach tube. The calves varied in age from one day to 10 weeks o ld and were raised under cond itions as free o f coccid ial contamination as possible (Stockdale & Niilo, 1976). The d egree of contamination of the inoculum of E. w emii used for infection was minimal. On examina tion of 500 oocysts from the pool of oocysts used to produce inocula, no coccidian species other than E. zuemii were found. However, in nearly a ll ca lves infected, oocysts of E . ellipsoidalis were found in the faeces of the calves from the I I th to the 16th day after inoculation. All calves, that were killed after patency of E. wemii was established, shed oocysts of-that species with less than 5% contam ination by o ther species. The calves were killed 10, 12, 14, 16, 18, 19,20,21,22 a nd 24 days after infection a nd their a limentary tracts removed. The small intestine was severed at the ileo-caecal junction and p ylo rus, cut into I m lengths and fixed in Serra's fixative (Fernando & McCraw, 197 3). The colon a nd caecum were similarly fixed. Sections of paraffinembedded tissue were cut at 511 and stained with haem atoxylin and eosin.
BRI T ISH VETE RINARY JOURNAL, 133,5
472
RESUL TS
Large schizonts, probably first generation , were found in the last 3 m o f small intesti ne, their greatest concentration was in the second metre from the ileo-caecal junction. The mean sizes of these schizonts in calves killed 10, 12, 14 and 16 days after infection are given in Table I. These schizonts were usually found in cells o f the lamina propria close to the muscularis mucosa. They were found o nl y in the sm all intestine a nd never in the colon or caecu m. The development o f the merozo ites within the schizo nt from spherical bodies is similar to the 'blastophore' formation described in the first generatio n schizogony of E. boviJ (Hammond, Ernst & Miner; 1966).
TABLE I TS OFE. ZUERNll IN CA LVESATPOST·M ORTEM EXAMI NATIO
SI ZE OF FIRST G ENERAT I 0
Day after infection 10 12 14 16
Range of length and width
Mean length and width 90
~
x 59
~
8 7~ x5 7~
149 ~ x J09 ~ 167~ x I 22 ~
(J 10 ~ - 8 7 ~ ) x (78 ~ - 46 ~ ) (JO I ~-74~ ) x (69 ~- 46 ~ ) (234 ~-1 20 ~ ) x ( 133 ~ -69 ~ ) (2 25 ~-11 5 ~ ) x (202 ~ -78 ~ )
The next generation of schizonts, presumably second, were found in sectio ns of the colon and caecum in epithelial cells , none were found in any of the sections of small intestine. The mean size of - these schizonLS was 14 11 x 13·5 11 (range 181l-131lx 1811- 13 11) and the mean number of the merozoites was 32. Schizogony in th e colon and caecum was found in all calves killed from day 16 to day 22 after infection . Gametogony occurred in the co lons and caeca o f all calves killed from days 16 to 22 after infection and took place in the epithelial cells . Oocysts were found in the large bowel of the calf killed 16 days after infection but occurred in greater numbers in calves killed 18, 19 and 20 days after infection . They were less common in th e calves kill ed later. The mean size of oocysts in tissue sections was 14 ·5 11 x 12·9 11 (range 16.411-12 . 7 Il x 14 .6 11-10.911). The measurements of the various stages of the life cycle reported here were all made from sections of the parasites in tissue after it had been fixed and processed and thus had probably decreased in size: oocysts in faeces from these animals, based on 60 oocysts measured , was 19 11 x 17· 8 11 (range 23· 7 11-1 4.6 11 x 2 1·8 11- 12. 7 11).
DIS CUSSION
It appears that the life cycle of E. wemii contains at least two generations of schizogony before gametogony. The presumed first generation sch izogony occurs in the lower ile um and the second generation schizogony and gametogony occur in th e colon and caecum . It is possible that there could b e an earli er schizogony as the eadies t data obtained here were from the calf killed 10 days after infection. However the first schizont described here closely resembles the first generation schizont of E. w ernii
473
LIFE CYCLE O F EIMERIA ZUERNII
grown in tissue culture described by Speer, DeVos & H ammond (1973). They report ed that the first generation schizont matured 20 days after inocu lation in to tissue cu lture. The greatest number of mature sch izonts, fi lled with completely (ormed merozoites, were seen in the calf killed 16 days after infection . It is possible that the maturation of the first schizogony would occur earlier in the normal host. In most species o f Eimeria that have been grown in vitro the schizogonous stages resemble those seen in vivo . H owever, this may not be true for all species. The life cycle of E. z.uernii described here appears to be very simi lar to that of E. bovis (Hammond, Anderson & Miner, 1963) a nd different fi-om that of E. z.uemii described b y Davis & Bowm an (1957) at least from the tenth day of infection onwards. ACKNOWLEDGEMENTS
I gratefully acknowledge the excellen t technical assistance, suggestions and cooperation o f Mr G. B. Tiffin. I appreciate the facilities provided by the Institute Director, Dr S. E. Magwood. My final thanks to Mrs D. A. deBoer for typing the manuscript. R EFERENCES D AV IS, L. R . & B OWMAN, G. W. (1957 ). Am.j. vet. Res. 18,569. EERNA DO, M . A. & MCGRAW, B. M. (I 973 ).j. Parasit. 59, 493. h AMMOND, D. M., ANDERSEN , F. L. & MINER, M . L. (l963 ).j. Parasit . 49, 428 . HAMMOND, D . M. , ERNST,j. V . & MINER, M . L. (1966).j. Prot01.001. 13,559. SPEER, C. A. , D EVOS, A . J. & H AMMON D, D . M . (19 73). Proc. helminth. Soc., Wash . 40, STOC KD ALE, P. H . G. & NlILO, L. (1976 ). Can. vet .j. In press.
(Accepted for publication J I August 1976)
160.
PROPOSED LIFE CYCLE OF EIMERIA ZUERNII By P. H. G . STOCKDALE Animal Pathology Division, H ealth of Animals Branch Agriculture Canada, Animal Diseases Research institute ( W) P.O. Box 640, Lethbridge, Alberta, Canada
SU MMARY
Ten bull ca lves, three months o ld or less, were infected with oocysts of Eimeria wemii. At post-mortem examiria tion large sch izonts were found in the lower ileum and small schizonts were present in the colon and caecum. Gametogony occurred in the co lon and caecum. The life cycle of E. zuemii apparently contains at least two sch izogonous generations before gametogony.
INTRODUCTION
Davis & Bowman (J 95 7) described the endogenous development of E. w emii in experimentally infected cattle. They reported that schizonts were seen from two to 19 days after inoculation in the upper, middle and lower portions of the small intestine and in the caecum and colo n. They found macrogametes and oocysts in the lower small intes tine, caecum a nd colon. In the work described here calves were infected with E. wemii and examined post mortem for the presence of the protozoan. MATERIALS AND METHODS
Ten Holstein (Fries ian ) bull calves were infected with 600000 oocysts of E. zuemii by stomach tube. The calves varied in age from one day to 10 weeks o ld and were raised under cond itions as free o f coccid ial contamination as possible (Stockdale & Niilo, 1976). The d egree of contamination of the inoculum of E. w emii used for infection was minimal. On examina tion of 500 oocysts from the pool of oocysts used to produce inocula, no coccidian species other than E. zuemii were found. However, in nearly a ll ca lves infected, oocysts of E . ellipsoidalis were found in the faeces of the calves from the I I th to the 16th day after inoculation. All calves, that were killed after patency of E. wemii was established, shed oocysts of-that species with less than 5% contam ination by o ther species. The calves were killed 10, 12, 14, 16, 18, 19,20,21,22 a nd 24 days after infection a nd their a limentary tracts removed. The small intestine was severed at the ileo-caecal junction and p ylo rus, cut into I m lengths and fixed in Serra's fixative (Fernando & McCraw, 197 3). The colon a nd caecum were similarly fixed. Sections of paraffinembedded tissue were cut at 511 and stained with haem atoxylin and eosin.
BRI T ISH VETE RINARY JOURNAL, 133,5
472
RESUL TS
Large schizonts, probably first generation , were found in the last 3 m o f small intesti ne, their greatest concentration was in the second metre from the ileo-caecal junction. The mean sizes of these schizonts in calves killed 10, 12, 14 and 16 days after infection are given in Table I. These schizonts were usually found in cells o f the lamina propria close to the muscularis mucosa. They were found o nl y in the sm all intestine a nd never in the colon or caecu m. The development o f the merozo ites within the schizo nt from spherical bodies is similar to the 'blastophore' formation described in the first generatio n schizogony of E. boviJ (Hammond, Ernst & Miner; 1966).
TABLE I TS OFE. ZUERNll IN CA LVESATPOST·M ORTEM EXAMI NATIO
SI ZE OF FIRST G ENERAT I 0
Day after infection 10 12 14 16
Range of length and width
Mean length and width 90
~
x 59
~
8 7~ x5 7~
149 ~ x J09 ~ 167~ x I 22 ~
(J 10 ~ - 8 7 ~ ) x (78 ~ - 46 ~ ) (JO I ~-74~ ) x (69 ~- 46 ~ ) (234 ~-1 20 ~ ) x ( 133 ~ -69 ~ ) (2 25 ~-11 5 ~ ) x (202 ~ -78 ~ )
The next generation of schizonts, presumably second, were found in sectio ns of the colon and caecum in epithelial cells , none were found in any of the sections of small intestine. The mean size of - these schizonLS was 14 11 x 13·5 11 (range 181l-131lx 1811- 13 11) and the mean number of the merozoites was 32. Schizogony in th e colon and caecum was found in all calves killed from day 16 to day 22 after infection . Gametogony occurred in the co lons and caeca o f all calves killed from days 16 to 22 after infection and took place in the epithelial cells . Oocysts were found in the large bowel of the calf killed 16 days after infection but occurred in greater numbers in calves killed 18, 19 and 20 days after infection . They were less common in th e calves kill ed later. The mean size of oocysts in tissue sections was 14 ·5 11 x 12·9 11 (range 16.411-12 . 7 Il x 14 .6 11-10.911). The measurements of the various stages of the life cycle reported here were all made from sections of the parasites in tissue after it had been fixed and processed and thus had probably decreased in size: oocysts in faeces from these animals, based on 60 oocysts measured , was 19 11 x 17· 8 11 (range 23· 7 11-1 4.6 11 x 2 1·8 11- 12. 7 11).
DIS CUSSION
It appears that the life cycle of E. wemii contains at least two generations of schizogony before gametogony. The presumed first generation sch izogony occurs in the lower ile um and the second generation schizogony and gametogony occur in th e colon and caecum . It is possible that there could b e an earli er schizogony as the eadies t data obtained here were from the calf killed 10 days after infection. However the first schizont described here closely resembles the first generation schizont of E. w ernii
473
LIFE CYCLE O F EIMERIA ZUERNII
grown in tissue culture described by Speer, DeVos & H ammond (1973). They report ed that the first generation schizont matured 20 days after inocu lation in to tissue cu lture. The greatest number of mature sch izonts, fi lled with completely (ormed merozoites, were seen in the calf killed 16 days after infection . It is possible that the maturation of the first schizogony would occur earlier in the normal host. In most species o f Eimeria that have been grown in vitro the schizogonous stages resemble those seen in vivo . H owever, this may not be true for all species. The life cycle of E. z.uernii described here appears to be very simi lar to that of E. bovis (Hammond, Anderson & Miner, 1963) a nd different fi-om that of E. z.uemii described b y Davis & Bowm an (1957) at least from the tenth day of infection onwards. ACKNOWLEDGEMENTS
I gratefully acknowledge the excellen t technical assistance, suggestions and cooperation o f Mr G. B. Tiffin. I appreciate the facilities provided by the Institute Director, Dr S. E. Magwood. My final thanks to Mrs D. A. deBoer for typing the manuscript. R EFERENCES D AV IS, L. R . & B OWMAN, G. W. (1957 ). Am.j. vet. Res. 18,569. EERNA DO, M . A. & MCGRAW, B. M. (I 973 ).j. Parasit. 59, 493. h AMMOND, D. M., ANDERSEN , F. L. & MINER, M . L. (l963 ).j. Parasit . 49, 428 . HAMMOND, D . M. , ERNST,j. V . & MINER, M . L. (1966).j. Prot01.001. 13,559. SPEER, C. A. , D EVOS, A . J. & H AMMON D, D . M . (19 73). Proc. helminth. Soc., Wash . 40, STOC KD ALE, P. H . G. & NlILO, L. (1976 ). Can. vet .j. In press.
(Accepted for publication J I August 1976)
160.
