Experimental Infections with Histomonas meleagridis and Heterakis gallinarum in Ducks and Geese

Abstract

Heterakis gallinarum and Histomonas meleagridis have been reported sporadically from ducks and geese. Experimentally, neither bird could be infected by rectal inoculation of H. meleagridis until a strain of Histomonas was isolated that had multiplied in geese following its introduction by eggs of Heterakis gallinarum. H. gallinarum started its development in both ducks and geese. The recovery of worms was poor, but for the first 10 days, growth was almost normal for survivors in either host. When these 10-day larvae were transferred rectally into chickens or turkeys, the worms continued their development, but if they were left in ducks or geese, they became progressively more retarded. Heterakids grown 10 days in compatible hosts and then transferred into ducks or geese fared no better. No heterakids reached maturity in ducks or geese, but a few persisted for 35 days. Histomonas meleagridis and the nematode that carries it, Heterakis gallinarum, are usually considered to parasitize only birds of the order Galliformes. However, natural infections with H. gallinarum in domestic ducks and geese (Anseriformes: Anatidae) have been reported frequently from the USSR, continental Europe, and Great Britain and occasionally from Argentina, Cuba, Formosa, India, Japan, and the United States (for a partial listing, see Lapage, 1961). Histomoniasis in geese was reported by Vorobev and Kolotilov (1954), Contiu et al. (1961), and Zelenenko (1962). Horton-Smith (1957) stated that histomonads may occur in the ceca and livers of ducks and geese but gave no details. Specific information on the susceptibility of these birds to infection with either parasite and on the course of such infection is not available. This report describes attempts to establish experimental infections with H. gallinarum and Histomonas meleagridis in domestic ducks and geese under controlled conditions. Birds whose responses to infection with these parasites are well known (chickens, turkeys, and ringnecked pheasants) (Lund and Chute, 1972a, c) were included to test the potency of the various inocula. MATERIALS AND METHODS Day-old mallards (Anas platyrhynchos) and Chinese geese (Cygnopsis cygnoides) were obtained commercially. The Beltsville Small White turkeys, New Hampshire chickens, and ringnecked pheasants that served as controls were from Received for publication 26 October 1974. flocks maintained at the Animal Parasitology Institute. All birds were brooded on wire and then kept in wire-mesh cages to preclude extraneous infections with H. meleagridis and Heterakis gallinarum. The ducks were 3 to 9 weeks old when inoculated; the geese, 3 to 4 weeks; and the other species, 4 to 6 weeks. Three types of experiments were conducted, each with ducks and geese: (1) rectal inoculation with Histomonas meleagridis, a rigorous test of susceptibility in galliform birds (Lund and Chute, 1972d); (2) oral inoculation with heterakid eggs carrying histomonads; and (3) rectal inoculation with Heterakis larvae from favorable hosts (chickens or pheasants) to determine the influence of the worms' early environment on their survival and development in ducks and geese. The number and kind of birds on each test are shown in Tables I and II. With one exception, which will be considered in the results, histomonads for rectal inoculation were from strains maintained in young turkeys by serial passage per rectum. Inocula were prepared from cecal contents and administered as described by Lund and Chute (1970). About 100,000 histomonads were given to each bird. The heterakid eggs to be inoculated orally were pooled from worms collected from chickens and turkeys that had acquired natural infections with H. gallinarum and Histomonas meleagridis. The conditions under which the eggs were embryonated and stored and the methods for preparing and administering inocula were the same as those described in a previous report (Lund and Chute, 1972b). On the test using ducks, each bird was fed 250 embryonated eggs; but on the test using geese, each bird was fed 300 such eggs. Heterakid larvae for rectal transfer into ducks were obtained from pheasants that had been fed 150 embryonated heterakid eggs 10 days previously. Larvae to be transferred into geese were grown in chickens, also fed 150 heterakid eggs. The eggs used in the 2 inocula were from slightly