Potential impacts of clearcutting on parasites of minnows in small boreal lakes.

Clearcutting and deforestation lead to increased erosion, increased water temperature, altered water chemistry, and modified watershed hydrology in aquatic systems. Effects on biological organisms have been documented for phytoplankton, zooplankton, benthos, and fish. In this study, parasites of the northern redbelly dace, Phoxinus eos (Cope), were examined from an experimental area consisting of headwater lakes and their watersheds in the boreal forest of Ontario, Canada prior to and after clearcutting around the lakes. Catchments of two lakes were heavily, and one lake partially, clearcut in 1996, and that of a fourth lake was untouched. In 1993, three years prior to clearcutting, five taxa of parasites, including the monogeneans Dactylogyrus sp. and Gyrodactylus sp., metacercaria of the digenean Clinostomum complanatum (Rudolphi, 1819), the nematode Rhabdochona canadensis Moravec et Arai, 1971 and the myxozoan Myxobolus sp. were found in or on northern redbelly dace. In 1998, two years after clearcutting, eight taxa were found on northern redbelly dace, including all of the above plus the digeneans Allocreadium sp. and Ornithodiplostomum ptychocheilus (Faust, 1917) and the copepod Ergasilus lizae Krøyer, 1863. Mean infracommunity species richness and the maximum number of species per fish were higher in the control and partially cut lake than in the heavily logged lakes. Uninfected fish were found in the heavily cut lakes, but not in the other lakes. Thus, disturbance may reduce parasite infracommunity complexity. Among individual parasite species, R. canadensis was absent from the two most heavily clearcut lakes and abundant in the two other lakes in 1998. Clearcutting may have affected the abundance of certain invertebrates in these lakes, in particular the mayflies that serve as intermediate hosts for R. canadensis. The parasites Allocreadium sp., O. ptychocheilus, and E. lizae have not been previously reported in or on northern redbelly dace.

Tissue migration of Elaphostrongylus spp. in guinea pigs (Cavia porcellus).

Third-stage larvae of Elaphostrongylus cervi, originating from red deer (Cervus elaphus), first reached the central nervous system (CNS) of guinea pigs (Cavia porcellus) 11 days postinfection (DPI). Neurologic signs were seen between 11 and 62 DPI in 4 of a total of 18 infected guinea pigs killed up to 112 DPI. Animals showing signs had 3 or more larvae in the CNS. Only 1, of a total of 1,114 larvae recovered, had developed to the fourth stage at 40 DPI. A direct tissue migration by third-stage larvae to the CNS was revealed by pressing and digesting almost all body tissues and by histological examination. Larvae penetrated through the stomach wall into the peritoneal cavity and then through the diaphragm into the pleural cavity. Many became encapsulated by inflammatory cells in the omentum, abdominal mesentery, mediastinum, and just beneath the liver capsule and lung pleura. A total of 44 larvae succeeded in reaching the CNS, apparently by migrating from the body cavities into muscles of the lateral body wall and entering the vertebral canal, likely along spinal nerves. Data were not consistent with a hematogenous migratory route that has been proposed previously. Few third-stage larvae of E. alces, originating from moose (Alces alces), were able to penetrate the gut of guinea pigs and none reached the CNS.

Extracting Protostrongylus spp. larvae from bighorn sheep feces.

First-stage larvae of Protostrongylus spp. were more numerous in the core of bighorn sheep (Ovis canadiensis canadiensis) pellets than near the surface. As a result, only 22% could be extracted from whole pellets and the numbers collected did not reflect the total number of larvae present in samples. Crushing semi-dried pellets yielded seven times as many larvae and numbers collected were correlated with totals present. The use of tissue, in addition to a screen filter in a beaker extraction method, produced a cleaner sample and did not affect larval collection or the correlation. By comparison, most first-stage larvae of Parelaphostrongylus tenuis from white-tailed deer (Odocoileus virginianus) were near the surface of fecal pellets where they may be removed readily by water.

Extracting protostrongylid nematode larvae from ungulate feces.

A major weakness of the Baermann funnel technique for extracting nematode larvae from feces is the funnel. As many as 67% of Parelaphostrongylus tenuis first-stage larvae lodged on the sloping surface of glass Baermann funnels. The number of larvae collected after 24 hr was not significantly correlated with total numbers in the samples, whether feces were supported over tissue paper or over window screening. Instead, we collected about 8 times as many larvae and achieved a significant relationship between larvae collected and the total numbers present when pelleted fecal material was submerged over screening in vertical-sided beakers. The methodology of this more efficient and more accurate way of estimating numbers of protostrongylid larvae is described. Most larvae were located on and in the mucous layer covering fecal pellets and readily left fresh pellets emersed in water; 72% of these larvae left after 6 min and only 11% remained after 1 hr. Larvae in water at room temperature sank as fast as 6 cm/min, but those close to a vertical glass surface sank more slowly (97% sank 18.5 cm in 105 min).

Spring migratory birds (Aves) extend the northern occurrence of blacklegged tick (Acari:Ixodidae).

Birds that had migrated northward across Lake Superior were captured upon reaching landfall at Thunder Cape (48 degrees 18' N, 88 degrees 56' W) at the southwestern tip of the Sibley Peninsula, northwestern Ontario, from 9 May to 9 June 1995. Twenty-one of 530 birds examined (6 of 55 species) had a total of 34 ticks; 1 blue jay, Cyanocitta cristata, had a northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago). Four blacklegged tick, Ixodes scapularis Say, larvae were found on an American robin, Turdus migratorius, and 2 on a chipping sparrow, Spizella passerina. This tick was not found on small mammals at Thunder Cape. Twenty-six larvae and a nymph of the rabbit tick, Haemaphysalis leporispalustris (Packard) were found on 1 American robin, 2 Swainson's thrushes, Catharus ustulatus, 1 white-throated sparrow, Zonotrichia albicollis, 1 common yellowthroat, Geothlypis trichas, 1 blue jay, and 12 chipping sparrows. A nymph of H. chordeilis (Packard) occurred on 1 chipping sparrow. Results demonstrate that northward migrating birds transport larvae of I. scapularis to areas of Ontario where the tick does not appear to have become established in small mammal populations. Spring migrants may be more involved in the dispersal of I. scapularis larvae than previously thought. Cooler temperatures and shorter seasons experienced in the more northerly, continental parts of the established distribution of this tick may extend the life cycle, resulting in a predominance of larvae rather than nymphs being acquired by northward-bound birds in early spring. Consequently, the role of spring migrating birds in the northward spread of I. scapularis and of borreliosis should be reevaluated.

The possible importance of wintering yards in the transmission of Parelaphostrongylus tenuis to white-tailed deer and moose.

Terrestrial gastropods were collected, 15 June to 25 November 1994, from beneath cardboard sheets on deer range in northeastern Minnesota (USA) and examined individually for larvae of Parelaphostrongylus tenuis, the meningeal worm of white-tailed deer (Odocoileus virginianus). Overall, 10 (0.08%) of 12,096 snails and slugs were infected with a mean (+/- SD) of 3.2 +/- 2.5 P. tenuis larvae. The prevalence of infection in gastropods was greater in a traditional deer wintering yard (seven of 4,401, 0.16%), where deer aggregated for almost 5 months at a density of 50/km2, than on summer range (three of 7,695, 0.04%) where they occurred at 4/km2. Despite relatively low densities of infected gastropods, their ingestion purely by chance remains a tenable explanation for the high prevalence of P. tenuis infection observed in white-tailed deer.

Infrapopulation dynamics of Parelaphostrongylus tenuis in white-tailed deer.

The prevalence and intensity of Parelaphostrongylus tenuis was determined by examining the head and a fecal sample from each of 379 white-tailed deer (Odocoileus virginianus) of known age that had been killed by vehicles in northeastern Minnesota (USA), November 1991 to May 1993. Small numbers of adult worms (mean +/- SD, 3.2 +/- 2.2; maximum, 13) were found in the cranium of 311 (82%); but over a third (118 of 311) of the infected deer were not passing larvae in their feces. Most occult infections were sterile because only one sex of the parasite was present. Adult P. tenuis were not found in the vertebral canal of deer. Prevalence of adult worms and larvae was lower in fawns (68% and 35%, respectively) than in older age classes of deer (89% and 63%, respectively). Forty-three of 45 deer between 7 and 15 yr old were infected. Mean (+/- SD) intensity of adult worms was lower in fawns (2.7 +/- 1.8) and yearlings (3.0 +/- 2.1) than in deer 7 to 15 yr (4.1 +/- 2.5). Conversely, the mean (+/- SD) number of larvae in feces was higher in fawns (103 +/- 119 larvae/g) than in adults 2 to 6 yr old (36.2 +/- 46 larvae/g) and 7 to 15 yr old (35.6 +/- 60 larvae/g). Mean (+/- SD) fecundity of female worms was greatest in fawns (51.6 +/- 64.8 larvae/g of feces/female worm). Deer of all ages passed more lavae in the spring. Deer from an area where year-round density was 30 deer/km2 had a mean (+/- SD) of 3.5 (+/- 1.8) adult worms; deer from the study area, with a summer density 2 deer/km2, had 3.2 (+/- 2.2) worms; however, deer at the greater density passed a greater mean number of larvae (93.8 and 57.1 larvae/g, respectively). Based on our results we propose that P. tenuis is a long-lived parasite and that most deer become infected in their first or second summer of life, and acquire few additional worms thereafter.

A practical method for cleaning Baermann glassware.

When using the Baermann technique to detect larvae of Parelaphostrongylus tenuis in deer feces, it is difficult to ensure that no larvae remain on glassware between samples. Of several cleaning methods tested here, emersion in 95% ethanol after flushing with hot or cold water was the most effective and practical.

Cardiovascular calcification associated with nephritis in a badger.

Calcification of the endocardium of the left artrium, and to a lesser extent the media of the pulmonary artery and aorta, was found associated with nephritis in a badger (Taxidea taxus).