David E. Worley

Helminths of the Coyote (Canis latrans Say) in Montana1

desirable to confirm conclusively that one injection is completely effective in eliminating psoroptic mites from bighorn sheep. The high degree of acanicidal effectiveness demonstrated indicate that injectable ivermectin has a strong potential for management of P. avis infections in bighonn sheep. Of particular interest is the possibility of using aerial delivery systems that may allow efficient injection of this acanicide without the necessity of capturing the animals for treatment.

Experimental Studies on Obeliscoides cuniculi, a Trichostrongylid Stomach Worm of Rabbits. I. Host-Parasite Relationships and Maintenance in Laboratory Rabbits

Susceptibility to a cottontail strain of Obeliscoides cuniculi was demonstrated in New Zealand White and Dutch rabbits. Stable infections lasting 4 to 8 months were induced by oral inoculation of 80 to 10,000 larvae in immature or adult rabbits of either sex. A larger infective dose was poorly tolerated and the resulting infection was transient. Immature albino guinea pigs were slightly susceptible to infection, but young albino mice, rats, and golden hamsters were refractory. The prepatent period averaged about 19 days. The mean recovery rate of the total larval dose in immature rabbits was 29.8%, with a male/female ratio of 0.26. Following spontaneous cure, rabbits were susceptible to reinfection. Certain gross biological similarities to ruminant stomach worm infections were noted.

Experimental studies on Trichuris muris in mice with an appraisal of its use for evaluating anthelmintics.

Attempts to infect white mice from five commercial sources with Trichuris muris yielded discouraging results. DBA-2 hybrid mice, particularly weanlings, were the most useful experimental hosts among nine types of rodents studied for susceptibility. In these mice, from 10 to 27 per cent of the administered eggs developed. Approximately 1 month was required for the worms to mature, and mature worms persisted for 2 to 3 months. However, the infections appeared to be of limited value in drug screening for trichuricidal activity, since they were refractory to treatment with the known trichuricides: dithiazanine iodide and pyrvinium chloride. Infection of laboratory rodents with Trichuris muris (Schrank, 1788) was first reported by Shikhobalova (1937). He experimentally infected white mice to study the developmental stages, with reference to the use of the worm for chemotherapeutic testing. Tissue reactions to the parasite in the cecum of white mice were described by Efremov and Shikhobalova (1939), and resistance of white mice to superinfection with T. muris was demonstrated by Shikhobalova (1940, 1941). Attempts to induce immunity in mice by oral or parenteral vaccination with extracts of T. muris were reported by Leikina (1944). Previously, T. vulpis in dogs had been the main experimental trichurid infection (Lammler, 1958). The limitations of work with this host, in contrast to a small rodent, are readily apparent. Fahmy (1954) induced T. muris infections in laboratory-reared albino mice with eggs from wild house mice. He described the main points of the life cycle, including the morphogenesis of the larval stages, but failed to disclose the strain of mice used, the proportion of exposed mice that became infected, or the relative susceptibility among strains. Each of these factors may influence decisively the maintenance of the infection on a routine basis in the

Comparison of Montana and Alaska isolates of Echinococcus multilocularis in gerbils with observations on the cyst growth, hook characteristics, and host response

To assess its biological distinctness, an isolate of Echinococcus multilocularis from Montana was compared with an isolate from Alaska in gerbils (Meriones unguiculatus) by means of intraperitoneal inoculations with protoscoleces. The cysts formed by the Montana isolate were entire, hyaline, and translucent, whereas those produced by the Alaska isolate were granular, yellowish, and opaque. Vesicles of the Montana isolate were larger, produced protoscoleces more slowly but in greater numbers, and required a longer period to develop surfacial germ cell protrusions, which were of smaller size. Also delayed was invasion of the laminate layer by granulocytes and macrophages, and a longer time was required for the appearance of pulmonary metastases. The 2 isolates differed also in characteristics of rostellar hooks, those from the Montana isolate being fewer and larger, often with accessory hooks.

Helminth and Arthropod Parasites of Grizzly and Black Bears in Montana and Adjacent Areas

Parasites of free-ranging grizzly and black bears in North America have been investigated periodically since the early part of the present century. The emphasis in many of these studies was on the role of bears as potential sources of parasites transmissible to man such as the trichina worm, Trichinella spiralis (Maynard & Pauls 1962, Harbottle et al. 1971,Wand & Lyman 1972) and the broad fish tapeworm (Vergeer 1930. Rush 1932, Skinker 1931,1932). Other work has been confined primarily to taxonomic surveys or descriptive studies of parasitism in wild bears (Horstman 1949, Olsen 1968, Choquette et al. 1969). Little of the literature has been concerned with the potential influences of parasitism on the health of bear populations in the environment. The present study was designed with this objective in mind.

Experimental studies on Obeliscoides cuniculi, a trichostrongylid stomach worm of rabbits. II. Anthelmintic studies in the dutch rabbit.

Phenothiazine, tetrachlorethylene, hexylresorcinol, CI-416 (a 2,4,5-trichlorophenolpiperazine salt), CI-474 (a cyanine compound), pyrvinium pamoate, and methyridine were effective against Obeliscoides cuniculi in single oral doses, as measured by reduction in worm burden and/or the percentage of rabbits cleared of worms. CI-474 and CI-416 showed the greatest potency of the ten compounds tested. The therapeutic failure of bephenium pamoate, thiabendazole, or Ruelene indicates an absence of direct correlation of effect of these drugs in rabbits with their action against trichostrongylid stomach worms of ruminants. The availability of nematode strains adapted to laboratory animals has assumed increasing importance as the search for new anthelmintics has intensified. Despite taxonomic dissimilarities between many laboratory host-parasite systems and the ultimate parasite problems of human or veterinary importance, the success of such laboratory screening is a matter of record. The development of bephenium as an anthelmintic for hookworms, Ascaris, and Nematodirus was based upon the initial discovery of its effect on Nematospiroides dubius and Nippostrongylus muris in rodents (Copp et al., 1958). Likewise, the oxyuricidal effect of pyrvinium pamoate was first detected against oxyurids in mice (Thompson et al., 1962). The present study was undertaken to evaluate the response of Obeliscoides cuniculi in the Dutch rabbit to a series of standard anthelmintics. A primary objective was to determine to what extent such rabbit bioassay data could be extrapolated to the chemotherapy of ruminant nematodiasis. MATERIALS AND METHODS The nematode strain and methods for its handling have been described (Worley, 1963). Dutch rabbits of either sex were infected with 40 to 150 larvae when 6 to 10 weeks old and were housed in groups of 3 or 4 in wire-bottomed cages. Dosing was deferred for 16 to 20 days postinoculation to permit the worms to mature. Composite fecal samples from each group were examined for worm eggs before treatment was started. Pelleted Rockland rabbit ration was fed ad libitum. Drugs were administered by gavage as a single dose suspended in 0.5% hydroxyethyl cellulose after an 18-hr fast. Dosages were expressed as the active component and were administered in a volume of 10 ml of vehicle per kg of body weight with a flexible plastic catheter. Drug effect was assessed by comparing the number of worms remaining in the stomach 3 to 5 days after treatment with the number in sham-dosed controls. Host tolerance of drugs was evaluated by post-treatment weight changes and by gross indications of intolerance such as diarrhea. The rabbits were fasted for a minimum of 32 hr before necropsy to permit the clearance of excessive ingesta from the stomach. This extended fasting period was necessary because the habitual reingestion of fecal pellets resulted in delayed emptying of the stomach. Post-mortem worm counts were made after removing the excised stomach of each animal to a petri dish containing 0.86% saline solution. The mucosa was scraped and examined for worms under a Dazor 3X magnifying lens, and any remaining ingesta were washed through a 20-mesh screen to remove finer debris. The mucosal scrapings and washed stomach contents were examined with a dissecting microscope, and the number, sex, and condition of the worms recorded. Statistical analysis of the percentage of rabbits cleared of worms was obtained with the fourfold contingency tables of Mainland, Herrera, and Sutcliffe (1956), and worm burden means were compared with Students t test. Anthelmintics tested, with key references to the newer ones, were: phenothiazine, CI-416 [bis (2,4,5-trichlorophenol)piperazine salt] (Short and Elslager, 1962; Thompson, Worley, and McClay, 1962), hexylresorcinol, tetrachlorethylene, pyrvinReceived for publication 20 August 1962. * Present address: Veterinary Research Laboratory, Montana State College, Bozeman.

TRICHINELLA SP. IN WOLVES FROM INTERIOR ALASKA

Tongue samples were collected from 148 wolf (Canis lupus) carcasses during 1993 and 1994 near Fairbanks (Alaska, USA). A standard peptic digestion procedure was used to detect Trichinella sp. larvae. Larvae were found in 54 of 148 (36%) samples. There was no significant difference in sex-specific prevalence. Prevalence was significantly related to age. There was no relationship between the number of larvae/g of host tissue and the age or sex of the host. Trichinella spp. infection may cause illness in individual wolves. However, there was no indication the parasite had any impact on the population.

STUDIES ON PRONGHORN ANTELOPE (Antilocapra americana) AS RESERVOIRS OF ANAPLASMOSIS IN MONTANA1

Twenty-six pronghorn antelope (Antilocapra americana) were collected in an area of eastern Montana where bovine anaplasmosis is enzootic. Their sera were examined for evidence of anaplasmosis by the complement-fixation test. Strong false positive reactions (3+ and 4+ reactors) occurred for 19 of the sera tested; 6 sera were anticomplementary. Inoculation of antelope blood into anaplasmosis-free intact calves did not produce clinical or serological evidence of anaplasmosis, and anaplasma bodies were not found in stained blood smears of antelope or recipient calves.

Possible relationships between trichinellosis and abnormal behavior in bears

Data compiled from parasite studies of grizzly bears (Ursus arctos) and black bears (U. americanus) in the Yellowstone and Glacier National Park populations and surrounding areas of Montana and Wyoming during 1969-79 are reviewed with reference to the possible influence of infection with the muscleworm Trichinella sp. on bear behavior. In grizzly bears, the high prevalence of this parasite (61% of 254 bears infected), the elevated larval concentrations in sensitive anatomical sites such as the tongue (average, 51 larvae per gram of tissue), and the chronic nature of bear infections as indicated by the tendency for highest infection rates to occur in older age classes (> 16 yrs.), suggest a potential behavior-modifying effect might exist. However, retrospective analysis of recent human attacks by 4 grizzlies and 2 black bears in the northern Rocky Mountain region failed to demonstrate a consistent connection between erratic conduct and levels of Trichinella larvae (trichinae) in bear tissues. Clinical similarities of trichinellosis in bears and humans are hypothesized, and possible behavioral effects of ursine trichinellosis are discussed. Int. Conf. Bear Res. and Manage. 5:280-283 Reasons for overly aggressive behavior of some bears which periodically results in human attacks have been the subject of considerable speculation. Despite retrospective attempts to analyze confrontations which led to bear assaults (Herrero 1970, 1974; Martinka 1971; Schneider 1977), uncertainties still exist as to the factors responsible for the belligerent behavior displayed under some circumstances by both grizzly and black bears. This paper considers the possible influence of infections with the muscleworm, Trichinella sp. in triggering antagonistic behavior which could lead to bear-human conflicts. Recent human encounters with bears which resulted in personal injury or death in the northern Rocky Mountain region are reviewed in an attempt to determine whether this parasite might play a part in triggering atypical bear conduct for which there presently is no explanation. This research was supported by Federal Aid in Wildlife Restoration, Montana Project W-120-R (5891). The assistance of numerous colleagues and students who participated in various phases of this project, including J.B. Winters, J.C. Fox, R.H. Jacobson, F. Sogandares, R.H. McBee, M.S. Sterner, and F.M. Seesee, is sincerely acknowledged. Agencies that furnished logistical support or supplied samples for laboratory testing, which were a vital part of the project, include the Montana Department of Fish, Wildlife, and Parks; the National Park Service; the Montana Cooperative Wildlife Research Unit; and the Division of Wildlife Management of the U.S. Fish and Wildlife Service. CLINICAL ASPECTS OF MAMMALIAN TRICHINELLOSIS