Leon W. Bone

Bacillus thuringiensis strains affect population growth of the free-living nematode Turbatrix aceti

Summary Microbial toxins from Bacillus thuringiensis israelensis, B.t. kurstaki, and B.t. morrisoni reduced population growth of the free-living nematode Turbatrix aceti. Worm populations declined more after treatment with B.t. israelensis than the other tested strains. Population growth of the nematode was inhibited by repeated exposure to B.t. israelensis toxin at three-day intervals during a two-week period. Exposure of the nematodes to the toxin for eight hours caused more mortality than lesser periods of time. Microbial toxins from B. thuringiensis may be a source of agents for nematode control.

Trichostrongylus colubriformis: effect of anthelmintics on ingestion and oviposition.

Abstract The effects of the anthelmintics ivermectin, levaminsole, oxfendazole, piperazine citrate, pyrantel pamoate, tetramisole, and thiabendazole on ingestion and oviposition by Trichostrongylus colubriformis were determined. Six of the compounds reduced in vitro feeding at the tested doses while all drugs reduced in vivo feeding after treatment of the host. Additionally, in vitro or in vivo exposure to most anthelmintics decreased oviposition during subsequent in vitro assay. Invermectin had the most pronounced effect on in vivo and in vitro feeding and egg release. The neuromuscular activities of pharyngeal pumping and egg ejection may be suitable systems for rapid determinations of anthelmintic effects.

Effects of host serum on feeding by Trichostrongylus colubriformis (nematoda)

Summary The effect of host serum on in vitro feeding by Trichostrongylus colubriformis was studied by incubating adult helminths in goat serum containing the dye, Rhodamine B. The amount of dye ingested was determined by fluorometric analysis. Immune serum from goats infected with T. colubriformis suppressed helminth feeding, while normal serum from uninfected goats did not. Suppression of feeding by immune serum increased with the duration of the hosts infection. Heat‐inactivation (56°C) of immune serum did not affect its suppressive activity. Pre‐exposure of worms to immune serum decreased subsequent feeding activity. However, rigorous washing of helminths restored their feeding to levels that were similar to untreated worms. Indirect immunofluorescent studies with immune serum and FITC conjugated rabbit anti‐goat IgG demonstrated binding of immunoglobulin to the cuticle, stoma and excretory pore of whole worms. Feeding inhibition of immune serum was associated with IgG1 isotype. Results of the present studies indicated that IgG was responsible for in vitro suppression of T. colubriformis feeding and may be one effector of immunity to T. colubriformis in the goat.

Nippostrongylus brasiliensis: Feeding activity in the mouse

Abstract Nippostrongylus brasiliensis incorporated the fluorescent dye, Rhodamine B, while feeding in vivo. Uptake of dye in both sexes of helminth increased linearly from 30 to 120 min after the hosts were given dye per os. Feeding by female N. brasiliensis significantly exceeded that of the male at 4 and 5 days postinfection. Feeding declined in older helminths of both sexes. The density of helminths had no effect on their incorporation of dye in vivo. Feeding in male- and female-only groups of worms was similar to that seen in populations of mixed sexes. Feeding by helminths decreased during the first 36 h of food deprivation in the host, but increased during subsequent fasting of the host. Both sexes of N. brasiliensis resumed feeding within 15 min after the fasted hosts were fed. Growth of N. brasiliensis increased linearly from 4 to 7 days postinfection, based on dry weight. Seven-day-old and older females were significantly heavier than males.

Oviposition by Trichostrongylus colubriformis (Nematoda) in vitro

Summary Oviposition by females of the ruminant nematode Trichostrongylus colubriformis was influenced by in vitro conditions. Release of eggs declined linearly during incubation for 4.5 h. An average of 8.8 eggs was deposited by females during the first hour in vitro. Decreased pH, temperature, and osmolarity caused reduced production of eggs. Storage of females at 4°C had no effect on subsequent oviposition at 37°C. Oviposition was similar under light and dark conditions. Concomitant males or the females age did not influence production of eggs in vitro. The release of eggs in vitro was significantly decreased by octapamine and GABA while serotonin elevated oviposition. Thus, environmental stimuli from the host may partially modulate helminth fecundity.

Lethality of Bacillus thuringiensis morrisoni for eggs of Trichostrongylus colubriformis (Nematoda)

Summary A spore-crystal preparation of Bacillus thuringiensis morrisoni was lethal in vitro to eggs and larvae of the ruminant nematode Trichostrongylus colubriformis with an LD50 value of 0.21 μg total protein/ml. Toxicity of the microbial products declined with storage at ambient temperature, autoclaving, or heating over 65°C. Antibiotics and selected inhibitors of membrane transport reduced the toxicity of B.t. morrisoni for nematode eggs. The toxin from B.t. morrisoni differs from that of B.t. israelensis and B.t. kurstaki and may allow microbial control of helminths.

Nippostrongylus brasiliensis: in vitro feeding activity.

Abstract Nippostrongylus brasiliensis incorporated the fluorescent dye, Rhodamine B, while feeding in vitro . Uptake of dye in both sexes of helminth was time-dependent with maximal incorporation occurring after 30 min. Feeding activity was elevated as the time of removal from the host increased from 1 to 8 h. Feeding was reduced in 4- or 5-day-old helminths when compared to 7-day-old or older worms. Feeding activity increased also after temperature increases, pH decreases and solute decreases. Feeding was similar under conditions of both light and dark. Feeding by males and females of N. brasiliensis decreased as the density of worms in single- or mixed-sex groups of worms was increased. Females fed significantly more than males under crowded conditions.

Egg Enzymes of the Ruminant Nematode Trichostrongylus colubriformis

Summary Preparations from eggs of the ruminant nematode Trichostrongylus colubriformis were examined for the presence of selected enzymes. Chitinase (0.12 units/mg total protein), collagenase (0.56 units/mg total protein), lipase (0.16 units/mg total protein) and acetylcholinesterase (0.61 units/mg total protein) were detected. Hatching of nematode eggs may require several forms of enzymatic activity.

Characterization of and male adaptation to pheromone of femaleTrichostrongylus colubriformis (Nematoda)

Males of the ruminant nematodeTrichostrongylus colubriformis were significantly attracted to an incubate from their females during in vitro assay. Exposure of males to sera from uninfected and infected animals or selected neurotransmitters had no effect on their subsequent responsiveness to the females pheromone. In contrast, exposure to 1500 female-hours of pheromone decreased male responsiveness after moderate rinsing prior to bioassay. Rinsing of the males with larger volumes of Tyrodes solution prior to in vitro assay increased their subsequent response to the females pheromone. High-performance liquid chromatography yielded a presumptive pheromone peak with a fivefold increase in biological activity. This peak was soluble in alcohols and tetrahydrofuran, based on elution from reverse-phase Sep-Pak cartridges. Stability of the peak was increased by EDTA or ascorbic acid (10 mM). Storage for six weeks in ascorbic acid at 4 °C allowed recovery of 47.3% of the original material.

Effect of host serum on in vitro oviposition by Trichostrongylus columbriformis (Nematoda)

Summary Oviposition in vitro by female Trichostrongylus colubriformis was reduced after treatment with serum from goats which were infected for over 32 days. Serum from animals at 90 days postinfection reduced, dosage-dependently, in vitro oviposition by female nematodes. Serum and the immunoglobulin G fraction from animals that were immunized with adult worms also reduced egg release. The immunoglobulin G from immunized animals was bound to the cephalic region of the female worm, based on labelling by fluorescein isothiocyanate-conjugated rabbit anti-goat immunoglobulin G. Treatment of females with immune serum from immunized goats that was absorbed with mixed sexes or females of T. colubriformis had no effect on the females oviposition.