Joyce A. Devaney

Progress on control of northern fowl mites on caged laying hens.

Recent research on methods for controlling the northern fowl mite (NFM) on caged laying hens is reviewed. On inanimate objects, NFM may be controlled by fumigation with methyl bromide, increased temperature (49 degrees C for 1 h), or decreased temperature (-20 degrees C for 5 days). dipping chickens in aqueous suspensions of carbaryl or stirofos controlled NFM for 6 weeks without exceeding current egg tolerance residues. Feeding chickens reasonable concentrations of systemic pesticides registered for use on dairy cattle in the U.S.A., registered anticoccidials, zinc bacitracin, avermectins, and diflubenzuron did not produce systemic control of NFM. Chickens do develop immunity to NFM. The potential for further development and adoption of these techniques should provide the poultry industry with effective alternatives to existing chemical sprays and dusts.

Resistance to ivermectin by Haemonchus contortus in goats and calves

Efficacy of ivermectin on susceptible or resistant populations of the parasitic nematode Haemonchus contortus was determined in cattle and goats held in a barn. Goats were each infected with 3000 infective, ivermectin-susceptible or -resistant H. contortus larvae on day 0 and reinfected with 2000 infective larvae on day 24. Goats were treated orally with 600 micrograms kg-1 ivermectin on day 31. No significant differences were detected in blood packed cell volume (PCV) or total protein (TP), prepatent period, or epg among the four groups of goats that were each infected with one of four parasite strains (one susceptible, three resistant). There were no differences among the four parasite strains in the numbers of infective larvae that developed to the third larval stage from fecal cultures or in the viability of cultured infective larvae when held in the laboratory at 27 +/- 1 degrees C for 14 weeks. After treatment with ivermectin, there were significant differences among the parasite strains in PCV, TP, and epg. Total worm counts were reduced by 94 to 97% with three times the recommended dose. Immature and adult Skrjabinema ovis were also present in two treated goats. In a second test, one goat infected once with 10,000 infective larvae of a resistant strain of H. contortus and then treated with nine doses of ivermectin, increasing from 500 to 2000 micrograms kg-1 over a period of 133 days, had 35 adult worms at necropsy. In a third test, three calves were readily infected with an ivermectin-resistant strain of H. contortus from goats.(ABSTRACT TRUNCATED AT 250 WORDS)

Host Immune Response to Northern Fowl Mite: Immunoblot and Lectin Blot Identification of Mite Antigens

White leghorn hens were experimentally infested with northern fowl mites (Ornithonyssus sylviarum) and antibody responses to mite immunogens were monitored over 12 weeks. Mite burdens increased during the early phase of infestation and declined over the latter weeks of the study. Antigen was prepared from homogenized whole mites, which were then sonicated and extracted with non-ionic detergent. Antigen extract was fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and antibody-reactive polypeptides were identified by immunoblotting. At the start of infestation, hens had natural, pre-existing antibodies that reacted with several mite-extract components. Individual hens had different natural antibody reactivities; however, all birds had immunoglobulins reactive with extract polypeptides of 117,000, 77,000 and 36,000 molecular weight. A variety of mite extract components reacted with hen antibodies generated in response to experimental infestation. The number of antibody-reactive mite polypeptides increased through week 8 of infestation and then decreased by week 12. Fifteen polypeptides of northern fowl mite extract were reactive with antibodies developed by the majority of infested birds. These commonly reactive polypeptides had molecular weights ranging from 40,000 to 160,000. Glycoconjugates of fractionated mite extract were identified by blotting with lectins that have different carbohydrate binding specificities. Also identified were lectins that bound extract components with the same molecular weights as those moieties complexed by immunoglobulins of infested birds.

Parasitism of Mallophaga by Trenomyces histophtorus

Abstract Despite current theory that fungi of the order Laboulbeniales are not injurious to their hosts, we found that Trenomyces histophtorus, a parasite of Mallophaga, invaded the body cavity of its host and produced an extensive rhizomycelium that resulted in the loss of fat body and skeletal muscle in these insects.