Abstract
The extinction of host-specific parasites occurs with the extinction of their hosts-two species of host-specific lice were lost with extinction of the passenger pigeon (Ectopistes migratorius).3 When a host is either rare or removed from its ecosystem, parasite transmission may diminish to a level that results in the extinction of host-specific parasites. Two previously recorded species of parasites (Neotrichodectes mite and eimerian protozoa), possibly host-specific, are no longer observed in the endangered black-footed ferret (Mustela nigripes) population.2 The ethical and moral arguments used to justify the conservation of individual host species also apply to their co-evolved parasites.2,6 Utilitarian justifications for parasite conservation include: 1) The loss of one parasite can alter the competitive interactions of remaining parasite species, 2) parasitism in captivity may maintain the integrity of host immunity to pathogens still present in wild populations, and 3) the potential medicinal and biomedical research value of parasites.1,2,6
The United States Fish and Wildlife Service's consideration of parasites was evaluated by examination of the Threatened and Endangered Species System's Recovery Plans. All Recovery Plans for mammals available online (www.fws.gov) in March 2003 were reviewed for their mention of parasites. Seventy-six mammals were listed as either threatened or endangered. Twenty-eight Recovery Plans representing 37 endangered and four threatened mammals were reviewed. For the purpose of this analysis, parasites were defined as the resident fauna of a host animal without implying that pathologic changes result from the association. Only metazoan and protozoan parasites were included.
None of the 28 Recovery Plans specified actions to conserve parasites. Unique or species-specific parasites were discussed in two of the 28 (7.1%) Recovery Plans-the Point Arena mountain beaver (Aplodontia rufa nigra)5 and the Mexican long-nosed bat (Leptonycteris nivalis).4 Although the Recovery Plan for the Point Arena mountain beaver indicates awareness that mountain beavers are host to several host-specific mites and the largest known species of flea (Hystricopsylla schefferi), the parasite community of the Point Arena subspecies has not been investigated.5 The Mexican long-nosed bat (Leptonycteris nivalis) hosts a macronyssid mite that resides in the tissue surrounding the molar roots-the characteristic damage to the bone caused by the mites has been used to distinguish this bat species from others in the genus.4 Two of 28 (7.1%) plans listed, by either species or family name, three or more parasites found in the host. Thirteen of 28 (46.4%) plans either mentioned one or two specific parasitic diseases, or made a nonspecific reference to parasitism. Eleven of 28 (39.3%) plans made no reference to parasites as they affect either individuals or populations.
It is unlikely that government programs will be initiated to conserve parasites because of economic obstacles and/or negative public perceptions.2,6 Therefore, veterinarians and other ecological health professionals must be cognizant of the issue, as they are among those individuals most likely to determine the fate of parasites in a host. Suggested means of parasite conservation include a survey for host-specific parasites prior to implementing single-species conservation programs, use of alternative hosts to maintain the parasite population, establish programs that conserve the host parasite interaction, and emphasize community rather than species-level conservation programs.2 Resources permitting, all host-specific biologic entities, including bacteria and viruses, should be given similar considerations.
Literature Cited
1. Daszak, P., and A.A. Cunningham.·2002. Emerging infectious diseases: a key role for conservation medicine. In: Aguirre, A.A., R.S. Ostfeld, G.M. Tabor, C. House, and M.C. Pearl (eds.). Conservation Medicine: Ecological Health in Practice. Oxford University Press, New York, New York.
2. Gomper, M.E., and E.S. Williams. 1998. Parasite conservation and the black-footed ferret recovery program. Conservation Biol. 12: 730–732.
3. Stork, N.E., and C.H.C. Lyal. 1993. Extinction or 'co-extinction' rates? Nature 366: 307.
4. United States Fish and Wildlife Service. 1994. Mexican Long-nosed Bat (Leptonycteris nivalis) Recovery Plan. United States Fish and Wildlife Service, Albuquerque, New Mexico.
5. United States Fish and Wildlife Service. 1998. Point Arena Mountain Beaver (Aplodontia rufa nigra (Rafinesque )) Recovery Plan. United States Fish and Wildlife Service, Portland, Oregon.
6. Windsor, D.A. 1995. Equal rights for parasites. Conservation Biol. 9: 1–2.