Publications

Skeletal malformation rates for several frog species were determined in a set of randomly selected wetlands in the north-central USA over three consecutive years. In 1998, 62 sites yielded 389 metamorphic frogs, nine (2.3%) of which had skeletal or eye malformations. A subset of the original sites was surveyed in the following 2 yr. In 1999, 1,085 metamorphic frogs were collected from 36...

The effect of echinostome infections on the survival of Rana pipiens tadpoles was examined in relation to developmental stage of tadpoles. Individual tadpoles of Gosner stages 25, 27, 32–33, and 37–39 were exposed to 1 of 4 levels of cercariae (0, 20, 50, or 100). Only tadpoles at stage 25, the earliest stage infected, died within a 5-day experimental period. This stage-specific...

No abstract available.

Vacuolar myelinopathy was confirmed by light and electron microscopic examination of mallards (Anas platyrhynchos), ring-necked ducks (Aythya collaris), and buffleheads (Bucephala albeola) collected during an epizootic at Lake Surf in central North Carolina (USA) between November 1998 and February 1999. Clinical signs of affected birds were consistent with central nervous system...

The effects of aquatic contaminants generated by soda ash mining processes on the North American eared grebe (Podiceps nigricollis) population illustrates important issues associated with human-induced habitat degradation on the health of migratory species. Eared grebes have been extensively studied in their staging and breeding habitats, but little is known about their 2- to 3-day...

Using a raccoon poxvirus (RCN) expression system, we have developed new recombinant vaccines that can protect mice against lethal plague infection. We tested the effects of a translation enhancer (EMCV-IRES) in combination with a secretory (tPA) signal or secretory (tPA) and membrane anchoring (CHV-gG) signals on in vitro antigen expression of F1 antigen in tissue culture and the...

Recent evidence suggests that infection by larvae of the trematode Ribeiroia ondatrae accounts for a significant proportion of limb malformations currently observed in amphibian populations of North America. However, the effects of R. ondatrae infection on northern leopard frogs (Rana pipiens), one of the species most frequently reported with malformations, have not been adequately...

The number of Sarcocystis species that infect sea otters (Enhydra lutris) is unknown. Sea otter tissues were recently shown to harbor sarcocysts of S. neurona and of unidentified species of Sarcocystis. Whereas sarcocysts of S. neurona have walls 1–3 μm thick with type 9 villar protrusions, ultrastructure of a distinct thin-walled sarcocyst (0.5–0.7 μm thick) lacking villar protrusions...

Chronic wasting disease (CWD) is a disease of the nervous system that results in distinctive brain lesions. CWD affects elk, white-tailed deer, and mule deer, but has not been documented in livestock or humans. The origins of the disease, as well as the modes of transmission, remain unknown. Infected deer and elk appear robust and healthy in the early stages of CWD; clinical signs might...

No abstract available.

In 1993, the amphibian fauna of Las Tablas, Costa Rica, began to decline, and by 1998 approximately 50% of the species formerly present could no longer be found. Three years later, at the Reserva Forestal Fortuna, in western Panama, a site approximately 75 km east southeast of Las Tablas, KRL encountered a mass die-off of amphibians and a subsequent decline in abundance and species...

Because of the difficulty in identifying botulinum toxin in cattle, it is hypothesized that cattle are sensitive to levels of toxin below the detection limits of current diagnostic techniques (the mouse protection bioassay and the immunostick enzyme-linked immunosorbent assay [ELISA] for type C botulinum toxin). Using an up-down method for toxicologic testing, the median toxic dose...