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Leucocytozoon simondi Infections in Domestic Ducks in Northern Michigan with a Note on Haemoproteus1
Leucocytozoon simondi Infections in Domestic Ducks in Northern Michigan with a Note on Haemoproteus1 E L I CHERNIN AND ELVIO H. SADUN2 (Received for publication May 7, 1949)
URING the summer of 1948 at the University of Michigan Biological Station, opportunity was afforded to determine the prevalence of Leucocytozoon simondi infections among domestic ducks in Emmet and Cheboygan Counties. The question was of particular interest since no information has been made available in the literature regarding the incidence of the disease in the endemic area of northern Michigan since O'Roke's observations were published almost 20 years ago. (O'Roke, 1930, 1934). For the summer of 1930, O'Roke reported that 74 percent of all flocks examined in the general vicinity of the Biological Station were positive, and that of 200 individuals sampled, 35 percent were infected. During 1931 he found that 60 percent of all flocks (a total of 300 ducks) harbored infected individuals. Morbidity was found to be high among all age groups, with a very high mortality rate among the young ducklings. Ducklings exposed experimentally to blackfly bites became infected in almost every case. In discussing 1 Contribution from the University of Michigan Biological Station, the School of Hygiene and Public Health, the Johns Hopkins University, and the School of Medicine, University of Arkansas. The authors wish to express their thanks to Dr. Gilbert F. Otto under whose guidance this work was done. 2 Now in the School of Medicine, Tulane University.
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the epizootiology of the Leucocytozoon infections, O'Roke pointed out that what might be a heavily infected area one year might not be one during the succeeding year. Also, that if blackfly density is assumed to be fairly constant from year to year, the critical factor in the propagation of the disease becomes the number of chronic carriers available in the area as reservoirs for the infection. His data also indicated that the largest number of infected ducks were to be found during the hottest part of July when the greatest number of blackflies were present. Some difficulty was encountered at the outset of the survey herein reported because considerably fewer ducks are being raised in the northern part of the Lower Peninsula now than there were in the 1930's. Especially odd, in view of O'Roke's reports, was the fact that almost all the farmers told us that they were not having, and could not remember having had, losses or signs of disease among the ducklings which they raised over the summer period. Essentially the same observations were made by local agricultural agents, State Wildlife personnel, feed dealers, and others. All were in general agreement that duck raising had fallen off because of a lack of demand coupled with the high cost of feed. Only once did a farmer inform us that he had discontinued raising ducks because of ah unexplained disease which had
Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015
D
INFECTIONS IN DOMESTIC DUCKS
Briefly then, in none of the 43 ducks examined between June 23 and June 30 could the infection be found. However, between July 10 and August 7 the infection was demonstrated in the blood of 37 of 38 ducks. An additional seven had died under conditions which suggest Leucocytozoon as the cause of death. The data are
thus in agreement with the observation by O'Roke that the greatest number of infections is coincident with the hottest part of the summer and seem to occur in
July. Repeated blood examinations on naturally infected ducks suggest that there may be a cyclical fluctuation in gametocyte level, at least among birds newly infected. Blood smears from four of the birds were taken at three to five day intervals during the period from July 10 to August 14, and counts were tabulated in terms of the number of gametocytes per field. These data suggest that a fluctuation in gametocyte level occurs in some of the birds during the first 30 days of the cycle. It is felt that further investigation of the possibility of such fluctuation occurring is warranted. The general situation in Emmet and Cheboygan Counties during the period of the survey opens to suggestion an interesting epizootiological possibility. The relatively small number of birds available for examination was widely scattered over the better part of two counties. From our own limited observations and from our contacts with State Wildlife personnel, it appeared that the number of wild ducks nesting in the region was very small. It has already been noted that only a very few domestic ducks are kept over winter, and, as a matter of record, we found only two. Some doubt is thus thrown on the possibility that the few year old domestic ducks and nesting wild ducks necessarily acted as the reservoirs for the infection of almost all of a comparatively small and scattered number of susceptibles, despite a relatively heavy blackfly density. Two possibilities suggest themselves: that the passage northward through the area of large numbers of wild ducks early in the season provided the sources of infection to the blackflies, or, that this source was
Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015
decimated his entire flock one summer some IS years ago. During the period from June 23 to June 30, 1948, five flocks were located and a total of 43 ducks examined for the presence of Leucocytozoon in the peripheral blood. A single search of smears taken on these birds failed to reveal any infections. Since those few farmers who still raised ducks were not in the habit of keeping breeding stock over winter, the birds which we examined were, for the most part, very young, ranging in age from two to six or seven weeks. On July 10, four of a flock of seven six-week-old ducklings were found to be heavily parasitized. That the remaining three were probably infected was shown when the entire flock was transferred to the Biological Station and isolated under blackfly-proof conditions on July 13th and leucocytozoa were readily demonstrated in blood smears from all seven birds on July 17th. The survey was repeated over the same territory from August 2 to August 7 with results markedly different from those of the preliminary June survey. Thirty-one of the original 43 birds were still available for re-examination and all were found to be parasitized by a single search of the smears. Seven of the original number had died, but since 100 percent of the survivors in their respective flocks were positive during this period, a plausible assumption may be ventured that the seven succumbed to Leucocytozoon infections. Of seven ducks not included in the first survey period, six were hosts to leucocytozoa.
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E L I CHERNIN AND ELVIO H. SADUN
Four of the ducks died within three days of the inoculation. Blood smears made during this period were negative, and since autopsy revealed none of the pathology characteristic of early Leucocytozoon infection, it seems unlikely that Leucocytozoon was the cause of death. Of the five survivors, three which were 23 days of age at the time of inoculation had
parasites in their blood on the fifth day. The remaining two, six weeks of age at the time of inoculation, became positive by the eighth day. The three younger birds died within a day or two of the first appearance of gametocytes, while one of the older ducks survived until the third day after the appearance of gametocytes (July 28). The other six-week-old bird lived for 13 days after infection was first observed, but with progressive weakness, loss of weight, and almost total loss of feathers. Gross pathology of the internal organs at autopsy was limited to extreme hypertrophy of the liver and spleen accompanied by distinct friability of both organs. Of passing interest insofar as the primary scope of this paper is concerned, is the discovery by one of us (E. C.) of Haemoproteus infections in two of the dozen White Pekin ducks retained for observation during the winter. To the best of our knowledge, this is the first report of Haemoproteus in the common domestic duck of the United States, although there is one record of its having been found in common black ducks. Anas rubripes tristis, on Cape Cod (Herman, 1938), and another report of its presence in mallards, Anas p. platyrhynckos, in Wisconsin (Huff, 1942). Microfilariae have also been observed regularly on blood smear examinations of several of the birds being held for further study. SUMMARY
A survey of domestic ducks in Emmet and Cheboygan Counties, Michigan, was conducted during the summer of 1948 in order to determine the incidence of infection with Leucocytozoon simondi. The infection was not found in any of the 43 ducks examined during the latter part of June, but was found in all but one of 38 ducks by early August. Successful trans-
Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015
provided by other types of birds indigenous to the area during the summer months. Neither suggestion may be considered established, although the former seems the more probable within the framework of our present knowledge. It may be well to note, however, that since the host specificity of this infection has not been studied, one cannot exclude the possibility of other reservoir hosts, In addition to showing that Simulium could transmit the disease to ducks, O'Roke also demonstrated that it was possible to transmit the disease artificially by the inoculation of tissues from diseased ducks into healthy ones. (O'Roke, 1934). Prompted by the fact that there has been no corroborative evidence for this observation since O'Roke's report, and that O'Roke did not mention the details of the transmission, it was decided to attempt to repeat his work. Accordingly, two heavily infected birds were sacrificed on July 17, and portions of the heart, spleen, liver, and lungs of each were removed into normal saline. The tissues were then ground in a minimal amount of saline by means of a mortar and pestle until the supernatant homogenate could be drawn up into a syringe fitted with a #18 needle. One-half to 1 cc. of this material was inoculated intraperitoneally into a series of nine healthy ducks. All experimental ducks were housed under blackfly-proof conditions both before and after inoculation and for as long as they were under observation.
INFECTION IN DOMESTIC DUCKS
fer of the disease by means of inoculation of tissues from "donor" ducks during the acute phase of the disease is again reported. Epizootiological considerations suggest the possibility that early wild duck transients or birds other than ducks may serve as the reservoirs for the infection in the area. The possibility of fluctuation in gametocyte level is suggested. Two cases of infection with Hdemoproteus in the domestic White Pekin duck are recorded. It is believed that this constitutes the first such report in this country.
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REFERENCES Herman, C. M., 1938. Haemoproteus sp. from the common black duck. Anas rubripes tristis. Jour. Parasit. 24: 53-56. Huff, C. G., 1942. Schizogany and gametocyte development in Leucocytozoon simondi and comparisons with Plasmodium and Haemoproteus. Jour. Infect. Dis. 71: 18-32. O'Roke, E. C , 1930. The incidence, pathogenicity, and transmission of Leucocytozoon anatis of ducks. Jour. Parasit. 17 (suppl.): 112. , 1934. A malaria-like disease of ducks caused by Leucocytozoon anatis Wickware. Univ. Michigan Sch. of Forestry and Conservation Bull. #4. 44 pp. Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015
URING the summer of 1948 at the University of Michigan Biological Station, opportunity was afforded to determine the prevalence of Leucocytozoon simondi infections among domestic ducks in Emmet and Cheboygan Counties. The question was of particular interest since no information has been made available in the literature regarding the incidence of the disease in the endemic area of northern Michigan since O'Roke's observations were published almost 20 years ago. (O'Roke, 1930, 1934). For the summer of 1930, O'Roke reported that 74 percent of all flocks examined in the general vicinity of the Biological Station were positive, and that of 200 individuals sampled, 35 percent were infected. During 1931 he found that 60 percent of all flocks (a total of 300 ducks) harbored infected individuals. Morbidity was found to be high among all age groups, with a very high mortality rate among the young ducklings. Ducklings exposed experimentally to blackfly bites became infected in almost every case. In discussing 1 Contribution from the University of Michigan Biological Station, the School of Hygiene and Public Health, the Johns Hopkins University, and the School of Medicine, University of Arkansas. The authors wish to express their thanks to Dr. Gilbert F. Otto under whose guidance this work was done. 2 Now in the School of Medicine, Tulane University.
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the epizootiology of the Leucocytozoon infections, O'Roke pointed out that what might be a heavily infected area one year might not be one during the succeeding year. Also, that if blackfly density is assumed to be fairly constant from year to year, the critical factor in the propagation of the disease becomes the number of chronic carriers available in the area as reservoirs for the infection. His data also indicated that the largest number of infected ducks were to be found during the hottest part of July when the greatest number of blackflies were present. Some difficulty was encountered at the outset of the survey herein reported because considerably fewer ducks are being raised in the northern part of the Lower Peninsula now than there were in the 1930's. Especially odd, in view of O'Roke's reports, was the fact that almost all the farmers told us that they were not having, and could not remember having had, losses or signs of disease among the ducklings which they raised over the summer period. Essentially the same observations were made by local agricultural agents, State Wildlife personnel, feed dealers, and others. All were in general agreement that duck raising had fallen off because of a lack of demand coupled with the high cost of feed. Only once did a farmer inform us that he had discontinued raising ducks because of ah unexplained disease which had
Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015
D
INFECTIONS IN DOMESTIC DUCKS
Briefly then, in none of the 43 ducks examined between June 23 and June 30 could the infection be found. However, between July 10 and August 7 the infection was demonstrated in the blood of 37 of 38 ducks. An additional seven had died under conditions which suggest Leucocytozoon as the cause of death. The data are
thus in agreement with the observation by O'Roke that the greatest number of infections is coincident with the hottest part of the summer and seem to occur in
July. Repeated blood examinations on naturally infected ducks suggest that there may be a cyclical fluctuation in gametocyte level, at least among birds newly infected. Blood smears from four of the birds were taken at three to five day intervals during the period from July 10 to August 14, and counts were tabulated in terms of the number of gametocytes per field. These data suggest that a fluctuation in gametocyte level occurs in some of the birds during the first 30 days of the cycle. It is felt that further investigation of the possibility of such fluctuation occurring is warranted. The general situation in Emmet and Cheboygan Counties during the period of the survey opens to suggestion an interesting epizootiological possibility. The relatively small number of birds available for examination was widely scattered over the better part of two counties. From our own limited observations and from our contacts with State Wildlife personnel, it appeared that the number of wild ducks nesting in the region was very small. It has already been noted that only a very few domestic ducks are kept over winter, and, as a matter of record, we found only two. Some doubt is thus thrown on the possibility that the few year old domestic ducks and nesting wild ducks necessarily acted as the reservoirs for the infection of almost all of a comparatively small and scattered number of susceptibles, despite a relatively heavy blackfly density. Two possibilities suggest themselves: that the passage northward through the area of large numbers of wild ducks early in the season provided the sources of infection to the blackflies, or, that this source was
Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015
decimated his entire flock one summer some IS years ago. During the period from June 23 to June 30, 1948, five flocks were located and a total of 43 ducks examined for the presence of Leucocytozoon in the peripheral blood. A single search of smears taken on these birds failed to reveal any infections. Since those few farmers who still raised ducks were not in the habit of keeping breeding stock over winter, the birds which we examined were, for the most part, very young, ranging in age from two to six or seven weeks. On July 10, four of a flock of seven six-week-old ducklings were found to be heavily parasitized. That the remaining three were probably infected was shown when the entire flock was transferred to the Biological Station and isolated under blackfly-proof conditions on July 13th and leucocytozoa were readily demonstrated in blood smears from all seven birds on July 17th. The survey was repeated over the same territory from August 2 to August 7 with results markedly different from those of the preliminary June survey. Thirty-one of the original 43 birds were still available for re-examination and all were found to be parasitized by a single search of the smears. Seven of the original number had died, but since 100 percent of the survivors in their respective flocks were positive during this period, a plausible assumption may be ventured that the seven succumbed to Leucocytozoon infections. Of seven ducks not included in the first survey period, six were hosts to leucocytozoa.
891
892
E L I CHERNIN AND ELVIO H. SADUN
Four of the ducks died within three days of the inoculation. Blood smears made during this period were negative, and since autopsy revealed none of the pathology characteristic of early Leucocytozoon infection, it seems unlikely that Leucocytozoon was the cause of death. Of the five survivors, three which were 23 days of age at the time of inoculation had
parasites in their blood on the fifth day. The remaining two, six weeks of age at the time of inoculation, became positive by the eighth day. The three younger birds died within a day or two of the first appearance of gametocytes, while one of the older ducks survived until the third day after the appearance of gametocytes (July 28). The other six-week-old bird lived for 13 days after infection was first observed, but with progressive weakness, loss of weight, and almost total loss of feathers. Gross pathology of the internal organs at autopsy was limited to extreme hypertrophy of the liver and spleen accompanied by distinct friability of both organs. Of passing interest insofar as the primary scope of this paper is concerned, is the discovery by one of us (E. C.) of Haemoproteus infections in two of the dozen White Pekin ducks retained for observation during the winter. To the best of our knowledge, this is the first report of Haemoproteus in the common domestic duck of the United States, although there is one record of its having been found in common black ducks. Anas rubripes tristis, on Cape Cod (Herman, 1938), and another report of its presence in mallards, Anas p. platyrhynckos, in Wisconsin (Huff, 1942). Microfilariae have also been observed regularly on blood smear examinations of several of the birds being held for further study. SUMMARY
A survey of domestic ducks in Emmet and Cheboygan Counties, Michigan, was conducted during the summer of 1948 in order to determine the incidence of infection with Leucocytozoon simondi. The infection was not found in any of the 43 ducks examined during the latter part of June, but was found in all but one of 38 ducks by early August. Successful trans-
Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015
provided by other types of birds indigenous to the area during the summer months. Neither suggestion may be considered established, although the former seems the more probable within the framework of our present knowledge. It may be well to note, however, that since the host specificity of this infection has not been studied, one cannot exclude the possibility of other reservoir hosts, In addition to showing that Simulium could transmit the disease to ducks, O'Roke also demonstrated that it was possible to transmit the disease artificially by the inoculation of tissues from diseased ducks into healthy ones. (O'Roke, 1934). Prompted by the fact that there has been no corroborative evidence for this observation since O'Roke's report, and that O'Roke did not mention the details of the transmission, it was decided to attempt to repeat his work. Accordingly, two heavily infected birds were sacrificed on July 17, and portions of the heart, spleen, liver, and lungs of each were removed into normal saline. The tissues were then ground in a minimal amount of saline by means of a mortar and pestle until the supernatant homogenate could be drawn up into a syringe fitted with a #18 needle. One-half to 1 cc. of this material was inoculated intraperitoneally into a series of nine healthy ducks. All experimental ducks were housed under blackfly-proof conditions both before and after inoculation and for as long as they were under observation.
INFECTION IN DOMESTIC DUCKS
fer of the disease by means of inoculation of tissues from "donor" ducks during the acute phase of the disease is again reported. Epizootiological considerations suggest the possibility that early wild duck transients or birds other than ducks may serve as the reservoirs for the infection in the area. The possibility of fluctuation in gametocyte level is suggested. Two cases of infection with Hdemoproteus in the domestic White Pekin duck are recorded. It is believed that this constitutes the first such report in this country.
893
REFERENCES Herman, C. M., 1938. Haemoproteus sp. from the common black duck. Anas rubripes tristis. Jour. Parasit. 24: 53-56. Huff, C. G., 1942. Schizogany and gametocyte development in Leucocytozoon simondi and comparisons with Plasmodium and Haemoproteus. Jour. Infect. Dis. 71: 18-32. O'Roke, E. C , 1930. The incidence, pathogenicity, and transmission of Leucocytozoon anatis of ducks. Jour. Parasit. 17 (suppl.): 112. , 1934. A malaria-like disease of ducks caused by Leucocytozoon anatis Wickware. Univ. Michigan Sch. of Forestry and Conservation Bull. #4. 44 pp. Downloaded from http://ps.oxfordjournals.org/ by guest on April 10, 2015