A multicenter evaluation of the effectiveness of Quest Gel (2% moxidectin) against parasites infecting equids.

Controlled trials with a common protocol were conducted in Idaho, Illinois and Tennessee to evaluate anthelmintic effectiveness of Quest Gel (QG; 2% moxidectin) against lumenal parasites in horses. Candidate horses were required to have naturally acquired nematode infections, as confirmed by presence of strongylid eggs in feces. At each site, 24 equids were blocked on the basis of pretreatment strongyle fecal egg counts (EPG) and randomly assigned to treatments within blocks. Within each block of two animals, one received QG on Day 0 at a dosage of 0.4 mg moxidectin/kg b.w. and one was an untreated control. Body weights measured the day before treatment served as the basis for calculating treatment doses. Horses assigned to treatment with QG received the prescribed dose administered orally with the commercially packaged Sure Dial syringe. Horses were necropsied 12-14 days after treatment, and lumenal parasites and digesta were harvested separately from each of five organs, including the stomach, small intestine, cecum, ventral colon and dorsal colon. Parasites from stomachs and small intestines were identified to genus, species and stage. Micro- (i.e., < 1.5 cm) and macroparasites (i.e., > 1.5 cm) in aliquots from the cecum, ventral colon and dorsal colon were examined in aliquots of approximately 200 parasites until at least 600 parasites had been identified to genus, species and stage or until all parasites in the 5% aliquot were examined, whichever occurred first. Data were combined across sites and analyzed by mixed model analysis of variance to assess the fixed effect of treatment and random effects of site and block within site. Because QG does not contain a cestocide, efficacy of QG against tapeworms was not significant (P > 0.05). Based on geometric means, however, efficacy of QG was greater than 90% (P < 0.05) against 38 species and developmental stages of cyathostomes, strongyles, bots, larval pinworms and ascarids encountered in at least 6 of 36 control horses in the combined data set. None of the horses treated with moxidectin exhibited evidence of adverse effects. Study results demonstrate QG, administered to horses with naturally acquired endoparasite infections at a dosage of 0.4 mg moxidectin/kg b.w., was highly effective against a broad range of equine parasitic infections.

Isolation of a microsporidian from a human patient.

Several genera of microsporidia have been identified morphologically in human tissue but none has yet been propagated in vitro. These primitive, obligate intracellular parasitic protozoa are poorly understood pathogens of a wide variety of vertebrates and invertebrates. In humans they are especially important as opportunistic pathogens in AIDS patients. A microsporidian was recovered from a human patient and propagated in vitro. The organism has diplokarya, divides by binary fission, and often is found free in the host cell cytoplasm. The name Nosema corneum is suggested.

Effects of heavy metals on structure, function, and metabolism of ciliated respiratory epithelium in vitro.

Tracheal explants were used to evaluate the relative ciliostatic and cytotoxic potential of heavy metal salts (cadmium chloride, chromium chloride, nickel chloride, and copper sulfate). Explants from hamster, rat, and guinea pig were all sensitive to the metals, though guinea pig explants showed the greatest difference between the untreated and metal treated tissues. Dosage levels were 50, 100, and 500 microM, for 24 to 148 h. Cadmium caused the greatest degree of ciliostasis and cell necrosis. Copper was less toxic, and nickel and chromium caused marginal damage when tested at 100 microM or lower. In each instance, damage became detectable at approximately 24 to 48 h and was nearly stabilized by 72 h. A significant loss of ciliary motion was always accompanied by a decrease in metabolic activity (dehydrogenase activity and ATP content). Transmission and scanning electron microscopy revealed a severely necrotic epithelium after exposure to cadmium, with only subtle morphological alterations after exposure to other metals. With all of the treatments there was no overt structural damage to cilia and little alteration in membranes of cells remaining in the epithelium. Some coagulation or vacuolization was noted in cadmium and copper treated explants but most cellular organelles did not display obvious damage. The most significant changes in the tracheal epithelium exposed to heavy metal salts in vitro were a loss of ciliary motion and a decrease in total ATP content.

Cytotoxicity and ciliostasis in tracheal explants exposed to cadmium salts.

Cadmium salts were examined for their biological effects on ciliated respiratory epithelium in hamster tracheal explants. Cadmium chloride and cadmium acetate both caused significant decreases in ciliary motion when tested at 100 micrograms M and above. Reductions in relative ciliary activity were dose-dependent and were first demonstrable at 8-32 hr. The decreased ciliary motion was accompanied by decreases in two key metabolic compound (ATP and dehydrogenase) which are normally associated with cell viability. Histopathological examination of cadmium-treated tissues showed an epithelium thinner than normal, with extensive vacuolization and few, if any, intact ciliated cells. The various biological effects exerted by cadmium are presented, along with potential mechanisms of pathogenesis for the observed ciliostasis and cytonecrosis. Decreases in adenosine triphosphate appear to play a critical role in the development of cadmium-related effects on cellular function and metabolism.