J.D. Kelly

In vitro field screening for anthelmintic resistance in strongyles of sheep and horses.

Abstract Simplified in vitro field methods are described for the detection and assay of benzimidazole-resistance in sheep trichostrongylids and horse strongyles. Worm eggs are recovered from fresh faeces, within 1 hour of collection, by flotation in sugar solution. The separated eggs are then incubated for 20–24 hours at 27–30° C in solutions of thiabendazole in distilled water ranging from 0.1 to 1.1 p.p.m. for sheep trichostrongylids and from 0.05 to 0.5 p.p.m. for horse strongyles. Under controlled conditions, eggs from thiabendazole-susceptible individuals of both sheep and horse nematodes rarely hatch at thiabendazole concentrations of 0.1 p.p.m. Eggs from resistant individuals will hatch at 0.1 p.p.m. and above. Semi-quantitative estimates of the level of resistance can be determined by measuring the % egg-hatch at varying concentrations of thiabendazole. A field method for selecting test animals with low egg-counts, and an in vitro method for the culture of eggs or first-stage larvae to third stage for identification are described.

The segregation of lambs into 'responders' and 'non-responders': response to vaccination with irradiated Trichostrongylus colubriformis larvae before weaning.

Abstract Random bred Merino ram and ewe lambs were vaccinated at 1, 2 and/or 3 months of age with irradiated T. colubriformis larvae. An exponentially increasing challenge of normal larvae was given to all groups including unvaccinated controls commencing at 1 month of age. The results, based on faecal egg counts, showed a dissociation into animals which responded to vaccination (geometric mean egg count 441) and those which did not (geometric mean egg count 1567). The proportion of responders was greatest in groups first vaccinated at the earliest age (1 month). Wool growth and liveweight gains showed severe depression corresponding to peak egg counts, however, responders were less affected than non-responders. There was no correlation between haemoglobin type and resistance to challenge. Faecal egg counts after impulse challenge with 10,000 normal larvae given at about 6 1 2 months of age showed a significant ranked correlation with those obtained during the primary exponential challenge. These results confirm that a proportion of young lambs respond to vaccination with irradiated larvae, and that genetically-determined factors are implicated in the ability of animals to respond to vaccination at an early age.

Intestinal Mast Cell and Eosinophil Numbers During Worm Expulsion in Nulliparous and Lactating Rats Infected with Nippostrongylus brasiliensis

Counts of small intestinal eosinophils and mast cells in nulliparous rats during primary infection with Nippostrongylus brasiliensis showed that worm expulsion preceded mast cell an

Nippostrongylus brasiliensis: effects of immunity on the pre-intestinal and intestinal larval stages of the parasite

Abstract Nippostrongylus brasiliensis : effects of immunity on the pre-intestinal and intestinal larval stages of the parasite. International journal for Parasitology 4: 183–191. Migration of the pre-intestinal larval stages of N. brasiliensis was studied in rats undergoing either primary or challenge infections. In rats undergoing a primary infection, more than 67 percent of larvae successfully migrated from the skin to the oesophagus by 70 h after infection, and subsequently over 90 per cent of these larvae became established in the small intestine as sexually mature adults. In immune rats undergoing a second infection, 46 per cent of larvae completed migration to the oesophagus by 70 h and of these, only 1·6 per cent became established in the intestine to produce eggs. These inhibitory effects on the pre-intestinal and intestinal larval stages were even more pronounced in immune rats undergoing a third or fourth infection and in addition, there was a prolonged sojourn and substantial retention of larvae in their lungs. There was no evidence that the immune response had an adverse effect on oesophageal fourth stags larvae as these organisms (obtained from immune donors) were able to establish and develop to maturity when transferred per os to normal animals. Syngeneic transfer of immune mesenteric lymph node cells to normal recipients, caused expulsion of parasites from the intestine but failed to effect migration of pre-intestinal larval stages. The implications of these findings are discussed in the context of current knowledge of the mechanisms of immunity to helminths.

Expulsion of Nippostrongylus brasiliensis from the Intestine of Rats

The relative activities of synthetic prostaglandins of the A, B, E and F classes in causing expulsion of N. brasiliensis worms from the small intestine of rats was compared by intra

Expulsion of Nippostrongylus brasiliensis from the Intestine of Rats: the Role of a Cellular Component Derived from Bone Marrow

Reconstitution of heavily irradiated rats (750 rad whole-body irradiation) with mesenteric lymph node cells from immune donors and bone marrow cells from either immune or normal (non-immune) donors caused the expulsion of transplanted damaged worms of Nippostrongylus brasiliensis. These results show that a third component derived from bone marrow is required for worm expulsion and is additional to the humoral (worm damage by antibody) and cell-mediated components previously defined by the studies of Jones and Ogilvie [1971], Kelly and Dineen [1972a], Keller and Keist [1972] and Dineen et al. [1973b].

Expulsion of Nippostrongylus brasiliensis from the Small Intestine of the Rat by Prostaglandin-Like Factors from Ram Semen

The widespread distribution of prostaglandins in tissues and fluids, their association with inflammatory responses of immunological origin and their biological properties suggest that they may play a

The stimulation of resistance in sheep to Fasciola hepatica by infection with Cysticercus tenuicollis

Abstract Infection of sheep with Cysticerus tenuicollis for 12 weeks generated a high level of protection (> 95%) against intra-ruminal challenge with metacercariae of Fasciola hepatica as measured by recovery of flukes from liver and bile ducts and counts of fluke eggs in faeces. The animals were resistant to Fasciola whether challenge was superimposed upon the cestode infection or after removal of the cestode with mebendazole. Previous infection with C. tenuicollis also protected against the pathogenic effects of challenge infection with F. hepatica. Liver fibrosis was much less extensive in resistant sheep than controls and PCVs were not affected although these were reduced during fluke infection in the control animals.

The metabolic lesion in Nippostrongylus brasiliensis induced by prostaglandin E1in vitro

Abstract Aerobic incubation of 6-day Nippostrongylus brasiliensis worms in the presence of PGE1 at 1000 ng ml of medium affected the energy status of the parasite. Both adenylate energy charge and ATP/ADP ratio were depressed. PGE1 either reduced the rate of phosphorylation or increased the rate of utilization of high energy phosphate bonds, or both. Addition of PGE1 to the culture medium reduced glucose uptake by the parasite, increased internal lactate and lactate output, decreased internal malate and increased the internal concentration of succinate. Several of these effects of PGE1 on metabolism were also exhibited by worms in vitro under anaerobic conditions. The action of PGE1 on worms in vitro adversely affected their ability to re-establish in rats and caused structural damage.

Expulsion of Nippostrongylus brasiliensis from the Intestine of Rats: Evidence for a Third Component in the Rejection Mechanism

Mesenteric lymph node cells obtained from immunized donors caused the expulsion of transplanted damaged worms of Nippostrongylus brasiliensis in both non-irradiated and irradiated (