Title: EXPERIMENTAL INFECTIONS OF MUSKOXEN (OVIBOS MOSCHATUS) AND DOMESTIC SHEEP WITH UMINGMAKSTRONGYLUS PALLIKUUKENSIS (NEMATODA: PROTOSTRONGYLIDAE); PARA-SITE DEVELOPMENT, POPULATION STRUCTURE AND PATHOLOGY
Submitted to: Canadian Journal of Zoology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 10, 1999
Publication Date: N/A
Interpretive Summary: A paucity of information on the distribution and life cycles of lungworms in ruminants from boreal to arctic latitudes hinders an understanding of the potential impact of these parasites. Following the discovery of Umingmakstrongylus, a pathogenic lungworm in muskoxen in 1995, we initiated experimental and comparative studies of parasite development and life history. Adult parasites live in massive cysts in the lung parenchyma of muskoxen; significantly, Umingmakstrongylus may not develop to patency in domestic sheep, although lesions consistent with parasite migration may develop following infection. In muskoxen, the prepatent period (the interval for development from infective larva to adult worm in the ruminant host) was found to be 91-97 days; larvae were shed continuously for up to 26 months, with a peak estimated at 1-2 million larvae per day. Exceptional longevity of adult parasites and shedding of massive numbers of larvae are considered to be adaptations for survival in harsh and unpredictable environments of the Arctic. Umingmakstrongylus is an apparently emerging pathogen in muskoxen that may be influenced by changing climates at high latitudes. These data serve to broaden our understanding of nematode faunal diversity in North America and are the foundation for defining the impact of this parasite on ruminant populations that represent irreplaceable food resources for northern communities.
Three muskoxen and two domestic sheep were experimentally infected with third stage larvae of U. pallikuukensis derived from the slugs Deroceras reticulatus and D. laeve. The course of parasite development and patency was followed for up to 26 months post infection (PI) using fecal examinations and radiography. The prepatent period in muskoxen was 91-97 days and the patent period extended to the time of euthanasia, 11 and 26 months PI. Larval production peaked 13-14 months PI. At post mortem of one muskoxen on day 97 PI, not all adult parasites were within typical pulmonary cysts; two were found free in interlobular septa. By months 11 and 26 PI adult parasites were found only within cysts. In two muskoxen, cysts were randomly distributed between left and right lungs. Dimensions of cysts were positively correlated with the number of adult parasites they contained. Lung pathology appeared localized and was associated with adult nematodes. Adult parasites did not establish in sheep. Patterns of parasite development, patency and pathology associated with U. pallikuukensis differ considerably from other lung-dwelling protostrongylids.