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.

Survival of sylvatic Trichinella spiralis isolates in frozen tissue and processed meat products.

The ability of Trichinella spiralis larvae to survive at subfreezing temperatures encysted in the musculature of wild carnivorous mammals was assessed by evaluating motility and infectivity (to rodents) of trichinae at various intervals after storage in frozen skeletal muscle. Fifty to 60% of the larvae in grizzly bear meat were alive after storage for 27 months at -6.5 to -20 C, and 30% to 50% were still alive at 34 months. However, none survived for 38 months, on the basis of infectivity in mice and larval motility. Trichinella larvae survived up to 4 months in frozen (-6.5 to -20 C) wolverine tissue. Viable larvae were not recovered from mountain lion or fisher muscle frozen for 1 month. The effect of postslaughter processing on Trichinella larvae encysted in bear meat was evaluated by use of a similar bioassay procedure. Viability of larvae recovered from black bear meat that had been processed into ham or jerky was not affected by dry curing with a commercial salt mixture. Trichinae from both preparations induced infections in mice (58 to 90 larvae/g of tissue). However, a combination of curing and smoking was consistently lethal to encysted larvae. Viable trichinae were not recovered from ground bear meat preparations (pepperoni, salami, or sausage) processed according to commercial standards.

The morphology and histochemistry of eggshell formation in Cephaluris coloradensis, a parasite of pikas.

Histochemical and histological studies of Cephaluris coloradensis (Nematoda: Oxyuridae) a parasite of pikas (Ochotonidae), show that in this species the eggs are each enclosed by three shells. The inner shell is chitin with an operculum at one end; the operculum is chemically distinct. The other two shells are lipoprotein. The inner lipoprotein shell is new, not previously reported in nematode species. It forms after the outer lipoprotein shell but beneath it, and is believed to be a product of the egg. The new layer encircles part of the embryo. A thin mucoprotein cementing substance binds the inner lipoprotein shell to the chitinous shell. A thin outermost mucoprotein layer formed from secretions of the uterus covers the eggshell.