William M. Samuel

Parasitic diseases of wild mammals.

Ectoparasites - lice biting Flies blot Flies and warble flies ticks sarcoptes scabiei and sarcoptic mange live flukes taeniasis/echinococcosis gastrointestinal strongyles elaphostrongylin lungworms of cervids lungworms of marine mammals baylisascaris procyonis and related nematodes diseases caused by filaroid nematodes dioctophymatosis hepatic capillariasis trichinella and trichinosis protozoa - enteric protozoan infections giardia and giardiasis cyclospora, eimeria, iospora and cryptosporidium opportunistically pathogenic free-living amoeba hepatozoon infection besnoitia spp toxoplasmosis and related infections.

Elk as a Potential Host for Meningeal Worm: Implications for Translocation

Translocation of wild ungulates is a common wildlife management tool and an integral component of game farming activities throughout the world. Elk (Cervus elaphus) are a primary species being moved, and the possibility of translocating a hazardous parasite led us to examine the potential for elk to survive infections of meningeal worm (Parelaphostrongylus tenuis), to shed larvae in feces, and thus, to translocate the parasite. Twenty-six elk calves were exposed to 15-300 infective larvae of meningeal worm. All 13 elk exposed to >125 larvae developed neurologic disease and died; 2 shed larvae in feces prior to death

The biological basis of grooming in moose: programmed versus stimulus-driven grooming

In domestic and wild mammals, tick infestation can be a significant fitness cost. Grooming behaviour has been shown to be effective in removing ticks. We studied grooming by moose, Alces alces, infested with winter ticks, Dermacentor albipictus, to determine which of two nonexclusive models for the regulation of tick-removal grooming, programmed or stimulus driven, best fit this host-parasite relationship. The programmed grooming model states that most grooming is driven by an internal timing mechanism which periodically evokes a bout a grooming independent of peripheral stimulation from tick bites. Because programmed grooming is preventive, the model predicts that those animals that groom the most will carry the fewest ticks, and a baseline level of programmed grooming is predicted even in a tick-sparse or tick-free environment. The stimulus-driven grooming model, on the other hand, states that grooming is a direct response to cutaneous irritation caused by tick bites and other sources of irritation. This stimulus-driven model predicts that (1) animals showing the highest rate of grooming will carry the most ticks and (2) animals will groom little when tick challenge is low. Both predictions of the stimulus-driven model were supported for moose: (1) calves oral-groomed three times more than cows, and tick densities on calves were three times higher than on cows; and (2) although all moose carried high densities of immature winter ticks (larvae, nymphs) from October through to February, grooming rate was very low until adult ticks started feeding in March-April. Peak grooming rates occurred during adult tick engorgement in March-April. Because an engorging adult female tick produces far more irritation than an engorging nymphal or larval tick, moose appeared to groom in direct proportion to the degree of cutaneous irritation and did not show a baseline level of grooming. The predominance of stimulus-driven grooming and apparent absence of programmed grooming may be the result of relaxed selection pressure for grooming in the evolutionary history of moose. Because the winter tick appears to have been introduced to moose from deer relatively recently, moose may not have had the time to adapt to winter ticks. The coevolutionary relationship between moose and winter ticks may be of insufficient duration for the evolution and/or maintenance of programmed grooming. (c) 1998 The Association for the Study of Animal Behaviour.

Trends of winter nutritional restriction, ticks, and numbers of moose on Isle Royale

During a 7-year study, we monitored winter nutritional restriction of moose (Alces alces) and moose numbers on Isle Royale (winters 1987-88 to 1993-94). Over the 7 winters, the estimated moose population decreased 26% from an historic high of 1,653 (winter 1987-88) to 1,216 (1989-90), then increased to a new high (1,880 and 1,770) by winters 1992-93 and 1993-94. During that time, there was a significant (P = 0.0486) negative relation (r = -0.84) between the percent of urine specimens collected from snow (snow-urine) in late winter with urea nitrogen:creatinine (UN:C) ratios ≥3.5 mg:mg and percent change in the moose population from winter 1987-88. Mean urinary UN:C of moose residing on the east and west ends of Isle Royale declined (P ≤ 0.0001) among years; however, slopes of the 2 trends were different (P = 0.0001). The nutritional restriction and decline in moose numbers appeared to involve an epizootic of the winter tick (Dermacentor albipictus; indicated by percent moose observed with tick-induced hair breakage and loss). During winters 1987-88 to 1989-90, the percentage of late winter snow-urine specimens with UN:C ratios indicative of severe nutritional restriction ranged from 47 to 58%; however, the percentage decreased to zero by winter 1993-94 as the tick infestation subsided and moose numbers increased.

TICK DEFENSE STRATEGIES IN BISON: THE ROLE OF GROOMING AND HAIR COAT

Summary Grooming behaviour, and its effectiveness in controlling infestation by the winter tick (Dermacentor albipictus), was studied for plains bison (Bison bison bison) in Elk Island National Park, Alberta, Canada from October 1995 through June 1996. Bison had few ticks (mean, 133 ticks per animal; 0.009 ticks per cm2), particularly in comparison with smaller sympatric cervids (moose, Alces alces; elk, Cervus elaphus; and white-tailed deer, Odocoileus virginianus), suggesting that tick defense in bison is highly effective. Bison performed grooming or grooming-like behaviours (oral grooming, scratching, rubbing, and wallowing) at a high rate during October, when winter tick larvae were blood feeding, but groomed very little from November to April, when nymphal and adult ticks predominated. Grooming in October probably removed many larval ticks while they were still unattached and traversing the body surface in search of an attachment site. Because bison groomed at the highest rate during the larval feeding period, when they were subjected to the lowest intensity of tick

MORTALITY OF FALLOW DEER (DAMA DAMA) EXPERIMENTALLY-INFECTED WITH MENINGEAL WORM, PARELAPHOSTRONGYLUS TENUIS

Six fallow deer (Dama dama) fawns died after receiving 25 to 150 infective larvae of Parelaphostrongylus tenuis. Fawns given higher doses usually died sooner (6 to 23 days) than those given lower doses (54 to 67 days). Early deaths were associated with severe acute peritonitis resulting from perforation of the intestinal wall; later deaths were associated with paralysis and inability to rise. Numerous adult P. tenuis were found within neural tissues of the brain and spinal cord in the three fawns with paralysis. One white-tailed deer (Odocoileus virginianus) exposed to infective larvae from the same source survived infection without exhibiting clinical signs and began passing larvae in feces 88 days post-exposure. At the doses used in this study, meningeal worm caused fatal infections in fallow deer. Results are compared to published observations of fallow deer naturally-infected with P. tenuis.

Parasites of the collared peccary from Texas.

Results of a survey of the parasites of the collared peccary (Dicotyles tajacu angulatus) in Texas are presented. Three ectoparasites, Amblyomma cajennense, Dermacentor variabilis, and Pulex porcinus were very common on peccaries from south Texas, but less common or absent in arid west Texas. Sucking lice, Pecaroecus javalii, were common on peccaries from west Texas, but were not found in south Texas. The known range of this louse in Texas is extended into the Big Bend area. Two ticks, Amblyomma inornatum and Haemaphysalis leporis-palustris, were found infrequently. Five of nine species of endoparasites found in this survey (Dirofilaria acutiuscula, Parabronema pecariae, Parostertagia heterospiculum, Physocephalus sp., and Texicospirura turki) were prevalent. Three species, D. acutiuscula, Gongylonema baylisi, and Fascioloides magna, are reported from North American peccaries for the first time. The geographic distribution of the large American liver fluke, F. magna, coincided with an area where the parasite is enzootic in white-tailed deer. It is concluded that parasitism was of little importance in population control of peccaries during the period of the study.

Parelaphostrongylus andersoni (Nematoda: Protostrongylidae) in White-tailed Deer from Michigan

Dorsal-spined larvae in fecal samples from free-ranging white-tailed deer (Odocoileus virginianus) in Michigan and Pennsylvania were used as a source of larvae to infect a hand-raised white-tailed deer fawn. The fawn received 200 third-stage larvae and passed dorsal-spined larvae in feces 66 days later. Muscleworm (Parelaphostrongylus andersoni), and meningeal worm (Parelaphostrongylus tenuis) were recovered at necropsy. Two white-tailed deer and seven wapiti (Cervus elaphus) exposed to larvae of the source from Pennsylvania harbored only P. tenuis. This is the first report of P. andersoni in the midwestern United States and extends the known range of this muscle-worm in free-ranging white-tailed deer. Concurrent infections of P. andersoni and P. tenuis have not been established previously in experimentally infected fawns.

MENINGEAL WORM EVOKES A HETEROGENEOUS IMMUNE RESPONSE IN ELK

Meningeal worm (Parelaphostrongylus tenuis) is a neurotropic nematode of ungulates in eastern North America. Lack of an effective diagnostic test increases the concern of translocating potentially infected ungulates into western North America, where P tenuis does not occur naturally. In an attempt to identify serodiagnostic molecules, we determined (1) whether elk (Cervus elaphus) experimentally infected with P. tenuis produce antibodies against infective larvae or adult worms, and (2) if sera consistently recognize antigens that distinguish P. tenuis from a common nematode parasite of elk, the lungworm Dictyocaulus viviparus. Each of 10 elk were exposed to 15 or 300 infective P. tenuis larvae. Serum was collected (0, 41, and 83 days post-exposure and at necropsy) and monitored for antibodies using the enzyme-linked immunosorbent assay (ELISA) and immunoblot. When reactivity of sera with larval P. tenuis protein was compared (day 0 versus 83), ELISA values were significantly higher on day 83 for elk exposed to 15 or 300 parasites. Likewise, ELISA values using protein of adult P. tenuis were higher for elk exposed to 300 larvae. Immunoblots showed that sera from elk, with adult worms in the central nervous system, consistently recognized the 25–27, 28–30, and 34–36 kDa antigens of infective larvae after 83 days. However, many D. viviparus molecules were found to cross-react with antibodies formed against meningeal worm antigens. Use of adult worm proteins for serodiagnosis appears limited, because no protein was consistently recognized by sera collected from elk exposed to 15 larvae. We believe that development of a reliable diagnostic test for meningeal worm requires more research addressing cross-reactivity and detection of P. tenuis during the incubation stage.

Dermacentor albipictus (Acari, Ixodidae) on Captive Reindeer and Free-ranging Woodland Caribou

Infestations of winter ticks (Dermacentor albipictus) on two captive reindeer (Rangifer tarandus tarandus) are reported and may be associated with increased grooming and alopecia. Over 400,000 ticks were recovered from one reindeer. Few ticks (<25 ticks/animal) were found on three free-ranging woodland caribou (Rangifer tarandus caribou).