The Parasitology of Some Wild Ruminants Introduced into New Zealand

Abstract

From nine wild ruminants examined, 22 helminth parasite species were recorded; a further two helminths identified to generic level; and five arthropod species were recorded. These parasites species were distributed amongst the host species as follows (the numbers of helminths given first): chamois (Rupicapra rupicapra L.) 10,1; Tahr (Hemitragus jemlahicus Hamilton-Smith, 1827) 10,1; Wild goat (Capra hircus l.) 15,1; Sika (Japanese) deer (Cervus nippon mantchuricus Swinhoe, 1864) 2, 0; Rusa deer (Cervus timoriensis Blainville, 1822) 0,0; Sambar deer (Cervus unicolor unicolor Lydekker, 1913) 1,0; Wapiti (Cervus Canadensis Erxleben, 1777) 5,1; Virginia deer (Odocoileus virginianus Boddaert, 1875) 12,2; Fallow deer (Dama dama L.) 3,0. Namatode egg counts were made from the faecal pellets of red deer (Cervus elaphus L.) and some specimens of Damalinia Longicornis were examined from this host. Otherwise all other records from red deer, used for comparative purposes in this study are from Andrews (1963). Hosts examined in the present study are from the New Zealand mainland, Raoul Island (goats) and Steward Island (Virginia deer, red deer). Twenty-four new host-parasite records were made, and two helminth and three arthropod parasites were recorded for the first time in New Zealand. The systematics of the helminths recorded were reviewed with particular attention paid to the Subfamily Trichostrongylinae. Following an assessment of the diagnostic characters used to distinguish genera and species within this subfamily, eight of the genera are examined, resulting in a re-diagnosis of some genera and relocation of species. Seven of these genera were divided into three groups on the grounds of their morphology and host relationships, the suggested grouping being supported by records from this study. Several incidents of teratology were recorded among the trichostrongyline worms. The systematics of the arthropods recorded (all were from the genus Damalinia) were reviewed briefly. The males of D. hemitragi and D. longicornis are described for the first time and redescriptions of the females of these species are given, resulting in the naming of two Varieties for each species. Keys to both the helminth and the arthropod parasites are given. The helminth infections in cervids and bovids were examined and some comparisons made. Environmental Influences (Particularly climate) are suggested in explanation of differences in worm population levels in bovid hosts. Differences in the composition of the cervid and bovid helminth faunas are attributed to specificity. Lice were considered to be very host specific. A helminthological comparison of two populations of goats (one from Raoul Island, the other from Tahora, Taranaki) showed differences in faunal components and worm population levels that could be explained by environmental differences, such as climate, the presence of other host species, and the different feeding habits of the two host groups. In both herds, the worm population increased with host age. Faecal egg-counts from red deer, taken over a yearly period, showed two peaks: one in early summer, the other in autumn. The cause or causes of these rises in egg-counts were not clear. Lice infection figures from tahr show that the proportion of male tahr infected decreases with host age, while the proportion of females infected remains constant. Aspects of the hosts behaviour and variations in the quality of the host’s coat are considered as causes of this variation. Apart from generally minor tissue damage to the infected internal organs, the helminths recorded did not have any serious effect on the health of the host. Lice also were of minor importance in this respect. In a comparison with the domestic ruminants, the wild ruminants appeared less heavily infected. This is possibly attributable to differences in their feeding habits, the form of their faecal material (in which the helminth larvae develop), and the climate of their ranges. An experiment to test the viability of helminth larvae according to the form of faecal material inhabited showed that, compared with loose pellets, aggregated faecal material allowed a greater number of larvae to develop. Compared with the cervids, the wild bovid parasite fauna resembled the domestic bovid fauna more closely. The foregoing work indicated that the major factors affecting the parasitology of wild ruminants in New Zealand were: the host’s environment, behaviour and age; the presence of other host species; and the host specificity of the parasites. The wild ruminants have a parasite fauna basically similar to equivalent hosts studied in other countries. The helminth infections recorded were often concurrent and it was considered that there was some possibility of species interaction. Geographical distribution of the parasites was seen to depend on the host specificity of the parasites and the distribution of the hosts. The wild ruminants have contact with domestic ruminants in a number of areas so that the wild animals are most likely reservoirs of domestic ruminant parasites. At present this factor is considered of limited economic importance. The parasite recorded have no importance in measures to control populations of wild ruminants. Finally, host-parasite relationships are examined in the light of the phylogeny of the various hosts.