Waters from normal larvae of Aedes aegypti (L.) are highly attractive to ovipositing conspecific females, whereas waters from larvae infected with the entomopathogenic digenean parasite, Plagiorechis elegans Rudolphi, are rendered strongly repellent. The production of the repellent appears to be mediated by the degree of environmentally induced stress experienced by the larvae. Whereas waters from fully fed larvae were highly attractive as an oviposition site, these were rendered progressively less attractive, and eventually strongly repellent as the larvae were deprived of food over a period of 7 days. Crowding of the larvae elicited similar repellent effects as did close contact between larvae and the walls of the container in which they were reared. The site of infection in the tissues of the mosquito larvae also influenced the intensity of repellency. Thus, infections of the head and thorax induced the highest degree of repellency, and infections of the abdomen the lowest. The repellent effect overrode attraction and remained stable for more than one week at 27°C, and even longer at lower temperatures. Stressors which induced repellency all precipitated similar physical and physiological changes in mosquito larvae. They reduced wet and dry weights and the concentration of serum carbohydrates, amino acids, proteins and lipids. Both infection and crowding rendered larvae anorexic. As well, infected larvae appeared to be unable to convert trehalose to glucose, thereby exacerbating the energy deficit. Incubating infected larvae in a dilute glucose solution significantly reduced the repellent effect of their waters. Addition of glucose to already repellent waters had little effect. Larvae of another species, Aedes atropalpus Coquillett, were equally capable of producing repellent effects when infected with P. elegans, and gravid females of Ae. aegypti were equally sensitive to these as to conspecific waters. This sensitivity, however, was not reciprocal. Aedes

No description available.

The mechanism of benzimidazole (BZ) anthelmintic resistance in Haemonchus contortus was investigated. The total binding (TB), low-affinity binding (LAB) and high-affinity (specific) binding (HAB) of ($ sp3$H) BZs (mebendazole (MBZ), oxibendazole (OBZ), albendazole (ABZ) and oxfendazole (OFZ)) in supernatants derived from BZ-susceptible (S) and BZ-resistant (R) strains were examined and compared. The TB of all ($ sp3$H) BZs was reduced for the R strain. The TB of OBZ, MBZ and ABZ was separated into LAB and HAB. However, OFZ bound with low-affinity. The binding affinity, K$ sb{ rm a},$ and maximum binding, B$ sb{ rm max},$ for the HAB of OBZ and MBZ were calculated using computer programs. Compared with the S strain, the B$ sb{ rm max}$ of the R strain was reduced but the K$ sb{ rm a}$ was not affected. LAB to parasite preparations devoid of tubulin was observed but HAB occurred to preparations containing tubulin only. The HAB per mg protein decreased from egg through larva to adult stage. It was shown by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blot and enzyme-linked immunosorbent assay (ELISA) analysis that the tubulin content per mg protein decreased from egg, through larva to adult worm. The ability of various BZs--OBZ, MBZ, ABZ, OFZ, fenbendazole (FBZ), albendazole sulphoxide (ABZSO), albendazole sulphone (ABZSO$ sb2),$ and thiabendazole (TBZ)--to bind tubulin was compared by displacement analysis and their IC$ sb{50}$ ( (BZ) required to inhibit 50% of the ($ sp3$H) BZ binding) and K$ sb{ rm a}$ values were determined. The IC$ sb{50}$ and K$ sb{ rm a}$ values approximately correlated with the known anthelmintic potency (recommended therapeutic doses) of the BZs except for OFZ and ABZSO. Tubulin bound BZs at 4$ sp circ$C with lower K$ sb{ rm a}$ than at 37$ sp circ$C. Western blot of tubulin separated by 2-dimensional electrophoresis showed that the $ beta$-tubulin isoform pattern of the S and R strains were dissimilar whil

No description available.

Biological and immunological aspects of the host-parasite relationship were examined in mice which are susceptible (A/J) and resistant (B10.A) to Giardia muris. B10.A exhibited a shorter latent period, lower cyst output during the acute phase of the infection and shorter period of cyst release compared to A/J. Characteristics of the infection transmitted from mouse-to-mouse and those induced by oral inoculation with cysts or trophozoites were similar. The infection was longer in male A/J and B10.A mice compared to females. Susceptibility and resistance during both the acute and elimination phases of the infection were under non-H-2-linked multigenic control. A/J and B10.A differed in non-specific serum IgG and IgA, but not in the specific IgG and IgA to G. muris. Specific antibodies participated in complement-mediated killing of trophozoites. Spleen, mesenteric lymph node and peritoneal cells from A/J and B10.A mice had a similar ability to kill trophozoites. The capacity of B10.A to mount inflammatory responses was greater than that of A/J. A/J were more immunosuppressed than B10.A during the infection, particularly at mucosal sites. Macrophage-like suppressor cells were shown to be the mediators of this suppression.

Bibliography: leaves 109-126. / xii, 126, [44] leaves, [34] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1997

x, 228 leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Entomology, Faculty of Agricultural Science, 1973

A simultaneous survey of canine and human gastrointestinal (GI) parasites was conducted in three socioeconomically disadvantaged, tea-growing communities in Assam, India. The aims of this study were to determine the epidemiology of GI parasites of zoonotic significance in dogs and geohelminth infection in humans using a combination of molecular biological and classical parasitological and epidemiological tools. A total of 328 and 101 dogs participated in the study. The prevalence of GI parasites in dogs was 99%. Parasitic stages presumed to be host-specific for humans such as Ascaris spp., Trichuris trichiura and Isospora belli were also encountered in dog faeces. A polymerase chain reaction - linked restriction fragment length polymorphism (PCRRFLP) was developed to identify the species of Ascaris eggs in dog faeces. The results supported the dog's role as a significant disseminator and environmental contaminator of Ascaris lumbricoides, in communities where promiscuous defecation by humans exist. The prevalence, intensity and associated risk factors for infection with Ascaris, hookworms and Trichuris were also determined among the human population. The overall prevalence of Ascaris was 38% and 43% for both hookworms and Trichuris. The strongest predictors for the intensity of geohelminths included socioeconomic status, age, household crowding, level of education and lack of footwear when outdoors. The zoonotic potential of canine Giardia was investigated by genetically characterising G. duodenalis isolates recovered from humans and dogs at three different loci. Phylogenetic analysis placed canine Giardia isolates within the genetic groupings of human isolates. Further evidence for zoonotic transmission was supported by strong epidemiological data. A highly sensitive and specific PCR RFLP based test was developed to detect and differentiate the species of canine hookworms directly from eggs in faeces. Thirty-six percent of dogs were found to harbour single infections with A. caninum, 24% single infections with A. braziliense and 38% mixed infections with both species. This newly developed PCR-based test provided a rapid, highly sensitive and specific tool for the epidemiological screening of canine Ancylostoma species in a community. A combination of canine population management, effective anthelmintic regimes and improvements in health education and sanitation is recommended for the control of canine and human gastrointestinal parasites in these communities.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Aubrey Cannon. Includes bibliographical references (p. 277-328). Also available online.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 115-117). Also available via the Internet.