Journal of Wildlife Diseases, 35(3), 1999, p. 608–612 ᭧ Wildlife Disease Association 1999

Leucocytozoonosis in Nestling Bald Eagles in Michigan and Minnesota

John N. Stuht,1 William W. Bowerman,2,4 and David A. Best31Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48823, USA; 2 Gale Gleason Environ- mental Institute, Lake Superior State University, Sault Sainte Marie, Michigan 49783, USA; 3 U.S. Fish and Wildlife Service, 2651 Coolidge Road, East Lansing, Michigan 48823, USA; and 4 Corresponding author (e-mail: [email protected]).

ABSTRACT: Thirteen of 21 nestling bald eagles permit No. 96-03 (U.S. Fish and Wildlife (Haliaeetus leucocephalus) examined for blood Service, Fort Snelling, Minnesota, USA). parasites in Michigan and Minnesota (USA) during June and July 1997 had patent infec- Nestlings were sexed and aged using the tions of Leucocytozoon toddi. No other para- methods of Bortolotti (1984). sites were seen. The degree of parasitemia was Thin blood smears were prepared in the light and varied from 1 to 2 on the Ashford field using a drop of blood from the bra- Scale. Several of the infected nestlings ap- chial vein. The smears were air dried im- peared to have elevated levels of heterophils in their peripheral circulating blood. One of the mediately and stored in an envelope or infected nestlings also showed signs of severe slide box to protect them from insects. anemia. We believe this is the first report of L. They were later fixed in absolute methanol toddi in the bald eagle. and stained with Giemsa in the laboratory. Key words: Anemia, bald eagle, Haliaeetus Each slide was examined for parasites in leucocephalus, leucocytosis, Leucocytozoon ϫ toddi, parasites, survey, threatened species. its entirety using low magnification (100 ) and for an additional 5 min under oil im- The bald eagle (Haliaeetus leucocephal- mersion (970ϫ). Each slide where para- us) has been listed as a threatened species sites were not observed was re-examined. in Michigan and Minnesota (USA) under The degree of parasitemia was estimated the United States Endangered Species Act on a logarithmic scale of 0 to 4 following (Grier et al., 1983). Its status as a threat- the method of Ashford et al. (1990) as fol- ened species makes it somewhat difficult lows: 0 ϭ no parasites seen in the entire to study and there are still aspects of its smear examined at low power (100ϫ); 1 ϭ life history that are poorly understood. fewer than 1 parasite per 100 high power Morbidity and mortality factors effecting (400ϫ) fields; 2 ϭ 1–10 parasites per 100 populations are one of the areas that need high power fields; 3 ϭ 11–100 parasites further study. The purpose of this investi- per 100 high power fields; 4 ϭ more than gation was to look for occurrences of blood 100 parasites per 100 high power fields. parasites in nestling bald eagles and to be- Parasites were identified by comparing gin to assess the impact of blood parasites color, morphology and size against descrip- on bald eagle populations. tions of known species. Blood smears with Twenty-one nestling bald eagles from 19 representative infections (Accession # breeding areas in Michigan and Minnesota 88010 and 88011) were deposited at the were sampled during annual banding op- U.S. National Parasite Collection (USDA, erations during June and July 1997 (Table Beltsville, Maryland, USA). 1). Nestlings were from 12 breeding areas Leucocytozoon toddi was the only blood within Voyageurs National Park (Minne- parasite seen in any of the 21 nestlings ex- sota), and six breeding areas in the Upper amined (Table 1). Blood smears from 14 Peninsula and one from the Lower Pen- of the nestlings showed relatively light in- insula of Michigan. Nestlings were han- fection (1–2 on the Ashford Scale). All 12 dled in accordance with established guide- nestlings from Minnesota were infected, lines and protocols of the U.S. Fish and and 2 of 9 nestlings from Michigan, both Wildlife Service Endangered Species Sub- from breeding areas within Seney National

608 SHORT COMMUNICATIONS 609

TABLE 1. Bald eagle nestlings examined for blood parasites in Michigan and Minnesota (USA) during June and July 1997.

Para- Ashford Slidea Date State Latitude/longitude Ageb Sex Weightc sitesd scale Breeding area name

556 6/04/97 MI 43Њ10ЈN, 84Њ00ЈW 39 M — NPS 0 Shiawassee SGA 559 6/09/97 MI 46Њ10ЈN, 86Њ30ЈW 39 M 3.4 NPS 0 Baldy Lake 561 6/10/97 MI 46Њ00ЈN, 86Њ20ЈW 41 M 3.4 NPS 0 Thunder Lake 562 6/10/97 MI 46Њ00ЈN, 86Њ20ЈW 46 F 4.3 NPS 0 Thunder Lake 282 6/10/97 MI 45Њ50ЈN, 86Њ30ЈW 49 M 3.6 NPS 0 Fishdam River 283 6/10/97 MI 45Њ50ЈN, 86Њ30ЈW 51 M 3.4 NPS 0 Fishdam River 41563 6/11/97 MI 46Њ20ЈN, 84Њ10ЈW 31 M 2.6 NPS 0 Sugar Island 95035 6/26/97 MN 48Њ30ЈN, 93Њ00ЈW 55 M 3.9 L 2 Northland Is. II 95036 6/26/97 MN 48Њ30ЈN, 93Њ00ЈW 43 M 3.1 L 1 N. Windigo Point 95037 6/26/97 MN 48Њ20ЈN, 92Њ50ЈW 50 F 4.3 L 1 Moxie Is. W. 95038 6/26/97 MN 48Њ10ЈN, 92Њ20ЈW 60 F 4.0 L 1 Mukooda G 95039 6/27/97 MN 48Њ20ЈN, 92Њ40ЈW 47 M 3.6 L 1 Sullivan Bay 95040 6/27/97 MN 48Њ30ЈN, 92Њ40ЈW 47 M 3.2 L 1 Brown’s Bay 95041 6/27/97 MN 48Њ30ЈN, 92Њ50ЈW 42 M 3.4 L 1 Shelland Is. 95042 6/27/97 MN 48Њ30ЈN, 92Њ50ЈW 40 F 3.5 L 1 Fox Is. II 95043 6/28/97 MN 48Њ30ЈN, 92Њ50ЈW 42 F 3.4 L 1 W. Fox Is. 95044 6/28/97 MN 48Њ30ЈN, 93Њ00ЈW 45 M 3.2 L 2 Kocinski Is. 95046 6/28/97 MN 48Њ20ЈN, 93Њ00ЈW 47 F 4.0 L 1 Gold Portage 95047 6/28/97 MN 48Њ30ЈN, 93Њ00ЈW 53 F 4.4 L 1 W. Squaw Franks SC-2 7/01/97 MI 46Њ10ЈN, 86Њ00ЈW 37 M 1.8 L 1 Seney NWR C-2 SC-1 7/01/97 MI 46Њ10ЈN, 85Њ50ЈW 25 F 2.5 L 1 Seney NWR D a 95044 and SC-1 deposited with the U.S. National Parasite Collection (Accession #88010 and 88011). b Age in days. c Weight in kg. d NPS ϭ No parasites seen; L ϭ Leucocytozoon toddi.

Wildlife Refuge (Table 1), were infected. The prevalence data as a whole may be Seven of eight females and seven of 13 misleading and the differences noted were males were infected. There was no obvious probably due to our sampling chronology relationship between age or weight and in- and not a true difference in prevalence. fection rate. Several of the infected nest- None of the seven nestlings examined be- lings appeared to have a leucocytosis of fore 11 June showed infection, whereas all some degree. Heterophil numbers seemed 14 examined after this date were infected. unusually high in these birds. Due to a This suggests that many of the nestlings lack of baseline data, we could not judge were examined before patency or before the condition more thoroughly. transmission began. This would explain The blood from the infected nestling at what appears to be a significant difference Seney Site C-2 (Table 1) was thin and wa- between prevalence in Michigan and Min- tery as well and typical of a bird with se- nesota, and between males and females. It vere anemia. This bird was well below nor- is possible, however, that further study mal growth-weight curves when compared may show that L. toddi is indeed not trans- to other birds of its age and sex (Bortolotti, mitted at some of the sites in Michigan. 1984), but otherwise appeared healthy. We The lack of obvious relationship between did not have the opportunity to more fully prevalence and age or weight also was examine this nestling to rule out some con- most likely due to the limited temporal current problem other than infection with and spatial nature of our sampling proce- L. toddi that may have contributed to its dure. One would normally expect the in- condition. fection rate to be higher in older nestlings. 610 JOURNAL OF WILDLIFE DISEASES, VOL. 35, NO. 3, JULY 1999

Leucocytozoon toddi is a common blood tion at a young age is more likely to be parasite of falconiformes. It has been re- harmful than a light infection at any age. corded in at least 38 species of birds from It is unfortunate that we were unable to around the world (Greiner and Kocan, examine the eagle nestlings more thor- 1977), including the African fish eagle oughly. The mere presence of L. toddi tells (Haliaeetus vocifer) and golden eagle (Aq- us very little about the effects of the par- uila chrysaetos). We believe that this is the asite on its host. Though leucocytosis and first report of L. toddi in the bald eagle. anemia are both conditions that are com- The only blood parasites previously re- monly associated with leucocytozoonosis in ported from bald eagles are Plasmodium birds (Fallis and Desser, 1974), they can polare (Greiner et al., 1981) and P. elon- be caused by other conditions as well. Typ- gatum (Nayar et al., 1998). We suspect ically, with leucocytozoonosis, anemia and that the method we used for detecting leucocytosis accompany morbidity and blood parasites was not sensitive enough mortality, but not always (Kocan and for us to find any of the other parasites Clarke, 1966; Fallis and Desser, 1974; commonly seen in the blood of birds. It is Herman et al., 1975; Hodge et al., 1981). often necessary to use isodiagnosis, or oth- Anemia can also be caused by nutritional er methods to detect infections outside of factors or by simple blood loss alone. peak parasitemias (Herman, 1968). It is Hunter et al., (1997) recently reported fa- likely that a more comprehensive survey tal anemia in fledgling great horned owls would produce a more accurate picture of (Bubo virginianus) from black fly hema- the true occurrence of blood parasites in tophaga. Not much is known about he- the bald eagle. matophaga in birds though Fallis and Des- Despite the common occurrence of L. ser (1974) suggested that any birds con- toddi, there appears to be relatively little fined to nests in the canopy that are un- known about many basic aspects of its life able to seek shelter from biting insects are history (Greiner and Kocan, 1977). Schi- at high risk of excessive hematophaga by zogony is unknown, but may be multiform black flies. They are also at risk of acquir- similar to L. simondi (Peirce and Marquis, ing heavy infections of Leucocytozoon sp. 1983). The vector is unknown but may be as well. These conditions certainly apply to a black fly (Simuliidae) (Greiner and Ko- the Seney National Wildlife Refuge where can, 1977) or a Culicoides spp. (Ashford et ornithophilic black flies are present from al., 1991). In all likelihood it is a black fly. April to September in most years, and The only species of Leucocytozoon known Voyageurs National Park where black flies to be transmitted by Culicoides spp. may and other blood feeding insects are known belong to another genus entirely (Bennett to be abundant at times. et al., 1965). These are particularly impor- Although most investigators believe tant bits of information on the life history that L. toddi is harmless (Ashford et al., of L. toddi that need further clarification 1990, 1991), Peirce and Marquiss (1983) if we are to better understand the impacts found that chicks of sparrow hawks (Ac- of this parasite on its host and host pop- cipiter nisus) in Scotland (UK) with very ulations. All species of the genus Leuco- high parasitemias of L. toddi may become cytozoon that have been shown to have a temporarily listless from anemia. Al- multiform schizogony like L. simondi ap- though the eagle nestling that we exam- pear to be pathogenic to some degree ined with signs of anemia from a breeding (Fallis and Desser, 1974). Equally impor- area in Seney did not have a large number tant is more information on vectors. Their of L. toddi parasites in its peripheral cir- abundance and emergence pattern will de- culating blood at the time we obtained a termine to a great degree what effect L. blood sample, it is very difficult to eval- toddi will have on its host. A heavy infec- uate parasitemia without some supporting SHORT COMMUNICATIONS 611 information. Leucocytozoon simondi for ,E.E.GREEN,P.R.HOLMES, AND A. J. LU- example can kill goslings (Herman et al., CAS. 1991. Leucocytozoon toddi in British spar- rowhawks Accipiter nisus: Patterns of infection 1975) and ducklings (Hodge et al., 1981) in nestlings. Journal of Natural History 25: 269– without detectable parasites in peripheral 277. circulating blood. Toyne and Ashford BENNETT, G. F., P. C. C. GARNHAM, AND A. M. FAL- (1997) speculate that this might explain LIS. 1965. On the status of the genera Leucocy- why they found only light infections of L. tozoon Ziemann, 1898 and Haemoproteus Kruse, 1890 (Haemosporidiida: Leucocytozoidae and toddi in a study of nestling goshawks (Ac- Haemoproteidae). Canadian Journal of Zoology cipiter gentilis). Heavy infections if they 43: 927–932. occurred, may have killed nestlings before BORTOLOTTI, G. R. 1984. Criteria for determining patency. age and sex of nestling bald eagles. Journal of As is often the case with so many par- Field Ornithology 55: 467–481. DESSER, S. S., AND A. RYCKMAN. 1976. The devel- asites, only well controlled experimental opment of pathogenesis of Leucocytozoon simon- infections can answer the question of di in Canada and domestic geese in Algonquin whether or not they are harmful to their Park, Ontario, Canada. Canadian Journal of Zo- hosts. The difference between what ap- ology 54: 634–643. pears to be a benign parasitism and path- ,J.STUHT, AND A. M. FALLIS. 1978. Leuco- cytozoonosis in Canada geese in Upper Michigan ogenesis depends entirely on the nature of I. Strain differences among geese from different the interaction between the host, parasite localities. Journal of Wildlife Diseases 14: 124– and the environment. This interaction is 131. complex and unique to each site where the FALLIS, M. A., AND S. S. DESSER. 1974. On species parasite and host occur. If the schizogony of Leucocytozoon. Advances in Parasitology 12: 1–67. L. toddi of is shown to be strain dependent GREINER,E.C.,AND A. KOCAN. 1977. Leucocyto- like it is for the schizogony of L. simondi zoon (Haemospordia: Leucocytozoidae) of the (Desser and Ryckman, 1976; Desser et al., falconiformes. Canadian Journal of Zoology 55: 1978) then L. toddi may well prove to be 761–770. a harmless parasite to a host in one loca- , D. J. Black, and W. O. Iverson. 1981. Plas- modium in a bald eagle (Haliaeetus leucocephal- tion and pathogenic to the same host in us) in Florida. Journal of Wildlife Diseases 17: another. 555–558. We thank the Michigan Department of GRIER, J. W., J. B. ELDER,F.J.GRAMLICH,N.F. Natural Resources for their help. The GREEN,J.V.KUSSMAN,J.E.MATHISEN, AND J. Wildlife Division provided laboratory P. M ATTSSON. 1983. Northern States Bald Eagle Recovery Plan. U.S. Fish and Wildlife Service, space and a microscope at the Cusino Washington, D.C., 128 pp. Wildlife Research Center. The Wildlife HERMAN, C. M. 1968. Blood protozoa of free-living Pathology Laboratory provided reagents birds. Symposium of the Zoological Society of and supplies for thin blood smears. This London 24: 177–195. research was supported in part by Mede- ,J.H.BARROW,JR., AND I. B. TARSHIS. 1975. Leucocytozoonosis in Canada geese at the Seney co, U.S. Fish and Wildlife Service, U.S. National Refuge. Journal of Wildlife Diseases 11: National Park Service, Lake Superior State 404–411. University, and the College of Veterinary HODGE, M., J. STUHT, AND J. KREHBIEL. 1981. He- Medicine, Michigan State University. We matological changes related to the pathogenesis also appreciate the help of all of the other of Leucocytozoon simondi in Canada geese and mallard ducks. Report Number 2885, Michigan scientists and students that assisted in all Department of Natural Resources, Wildlife Di- phases of work with the eaglets. vision, Lansing, Michigan, 14 pp. HUNTER, D. B., C. ROHNER, AND D. C. CURRIE. LITERATURE CITED 1997. Mortality in fledgling great horned owls ASHFORD, R. W., I. WYLLIE, AND I. NEWTON. 1990. from black fly hematophaga and leucocytozoo- Leucocytozoon toddi in British sparrowhawks Ac- nosis. Journal of Wildlife Diseases 33: 486–491. cipiter nisus: Observations on the dynamics of KOCAN,R.M.,AND D. T. CLARK. 1966. Anemia in infection. Journal of Natural History 24: 1101– ducks infected with Leucocytozoon simondi. 1107. Journal of Protozoology 13: 465–468. 612 JOURNAL OF WILDLIFE DISEASES, VOL. 35, NO. 3, JULY 1999

NAYAR, J. K., J. W. KNIGHT, AND S. R. TELFORD,JR. nisi sp. nov. from the sparrowhawk (Accipiter ni- 1998. Vector ability of mosquitos for isolates of sus). Journal of Natural History 17: 813–821. Plasmodium elongatum. The Journal of Parasi- TOYNE,E.P.,AND R. W. ASHFORD. 1997. Blood par- tology 84: 542–546. asites of nestling goshawks. Journal of Raptor Re- PEIRCE, M. A., AND M. MARQUISS. 1983. Haemato- search 31: 81–83. zoa of British birds. VII. Haematozoa of raptors in Scotland with description of Haemoproteus Received for publication 29 September 1998.