Earthworm Transmission of Heterakis and Histomonas to Turkeys and Chickens

Abstract

Lumbricus terrestris, Allolobophora caliginosa, and Eisenia foetida are vectors in the transmission of Heterakis gallinarum and Histomonas to chickens and turkeys. infective stage for Heterakis was found to be the second-stage (first post-hatching stage) larvae. Earthworms from infected premises that were maintained 2 to 3 days in each of three or more changes of clean soil or 7 days on moist filter paper transmitted as many cecal worms and produced as many Histomonas infections as did worms of the same species and source fed directly from the contaminated soil. worms' castings produced no infections. Subjecting earthworms to either 1% formalin or 1.5% nitric acid prevented the transmission of Heterakis and Histomonas. Heterakis eggs were never found in dissected earthworms or in washings of parts of earthworms. Living larvae emerged from the tissues into the coelomic cavities of dissected worms, and into the medium in which intact worms were immersed. As early as 1907, Curtice reported fatal blackhead in turkeys produced by feeding earthworms from a poultry yard. He noted that turkeys fed earthworms from soil not traversed by poultry did not acquire the disease. He, of course, knew nothing of the role of the cecal worm, Heterakis gallinarum (Shrank, 1788) Madsen, 1949, in the transmission of Curtice concluded, The earthworms in this instance were probably carriers of infected soil and were not necessarily a second host of the parasite. Ackert (1917) infected chickens with Heterakis (probably H. gallinarum) by feeding them earthworms, but if Histomonas infections occurred, they did not come to his attention. He suggested that the heterakid eggs might be carried on the slimy surface of the earthworm or in its engulfed food, but he did not rule out the possibility of other means of transmission. Madsen (1962) reported that some chickens acquired Heterakis and some developed blackhead after having been fed earthworms from pheasant yards. He commented as follows: Before being fed to the chicks, the worms were thoroughly washed and allowed to empty their intestines as much as possible. Nevertheless a certain amount of contents must have remained, as the group contracted infections with Heterakis gallinarum and blackhead. Received for publication 14 March 1966. *Portions of this study were presented at the 38th Annual Meeting of the American Society of Parasitologists, November 1963. An abstract of that presentation has been published (Lund et al., 1963). In our laboratories, the earthworm had been under suspicion for years as playing a part in the transmission of blackhead (Lund, 1960). senior author later observed that turkeys given earthworms sometimes developed clinical blackhead 24 to 48 hr sooner than could be expected as a result of feeding them embryonated Heterakis eggs. This prompted a more thorough investigation of the role the earthworm actually plays in the transmission of the parasites. MATERIALS AND METHODS All earthworms used for the initial studies here reported were collected from a yard that had been used for several years exclusively for rearing ringnecked pheasants, Phasianus colchicus L. 1758. Lumbricus terrestris L. 1758 and Allolobophora caliginosa Rosa were used for three major experiments. Also, miscellaneous other studies were conducted using these two species and Eisenia foetida Savigny, collected at times from sources other than the pheasant yard. birds used in the three major studies were 5-week-old Small Beltsville White turkey poults that had been reared and maintained in wirefloored batteries or cages under conditions that precluded the possibility of accidental infections with the parasites being studied. Chickens used for the miscellaneous tests were New Hampshires of similar age, reared and maintained in a similar