Exsheathment Of Larvae Research Articles

In vitro activity of Lantana camara, Alpinia zerumbet, Mentha villosa and Tagetes minuta decoctions on Haemonchus contortus eggs and larvae

The resistance of gastrointestinal nematodes to anthelmintics has increased the need to evaluate natural products that can replace or assist current strategies to control gastrointestinal nematodes. The objective of this study was to evaluate the effect of decoctions of Lantana camara (DLc), Alpinia zerumbet (DAz), Mentha villosa (DMv) and Tagetes minuta (DTm) on Haemonchus contortus by two in vitro tests. The effects of increasing concentrations of lyophilized decoctions (0.31 to 10mg/ml) were assessed using the egg hatch test (EHT). The decoctions were then tested in the larval artificial exsheathment assay. H. contortus third stage larvae (L3) were exposed to 0.31mg/ml A. zerumbet and M. villosa decoctions and 0.62mg/ml T. minuta and L. camara decoctions for 3h and then exsheathment procedure at 10min intervals. An inhibitor of tannins, polyvinyl polypyrrolidone (PVPP), was used to study if tannins were responsible for the inhibitory effect on hatching and exsheathment of larvae. A. zerumbet, M. villosa and T. minuta showed a dose-dependent effect in the EHT, which did not disappear after the addition of PVPP. No effect was observed for L. camara in the EHT. However, the decoctions inhibited the process of larval exsheathment, which may be related to tannin action because the addition of PVPP reversed the inhibitory effect. A. zerumbet, M. villosa and T. minuta decoctions showed inhibitory activity on H. contortus larvae hatching and exsheathing. The decoctions of these plants could be used to control gastrointestinal nematodes following confirmation of their anthelmintic activity in vivo.

An attempt to produce ostertagia circumcincta infections in mongolian gerbils

Adult infections of Ostertagia circumcincta were successfully established in gerbils, although worm growth was retarded compared with infections in sheep. Chronic administration of β-methasone to the host enhanced development of the parasite reproductive system but did not increase infection rate or prevent worm rejection. Infection rates achieved with single infections were not increased by using daily or weekly trickle infection regimes with or without prior exsheathment of larvae. Examination of stomachs from infected gerbils demonstrated pathological changes in the pyloric region which was the predilection site for O. circumcincta. This is in contrast to infections in sheep in which the fundic region of the abomasum is the preferred site.

Invasion of skin by larvae of the cat hookworm,Ancylostoma tubaeforme

A modification of the ‘floating raft’ method ofin vitropenetration study is described. This allows replication of results and additional conveniences in operation. Filter paper membranes have shown characteristics similar to those of skin and have been used for quantitative studies. A method of digesting penetrating larvae from skin has been used to reduce the variability inherent in whole skin. Neither chloroform soluble skin products nor gravity were found to have a significant effect on the number of larvae entering membranes. Exsheathment of larvae was not essential prior to penetration and no specific stimuli for exsheathment appear to be necessary. Scanning electron micrographs have shown that entry may be by either hair follicles or desquamations of the stratum corneum. No evidence of enzymic activity during the invasion process has been found so far and the results suggest that a mechanical rather than chemical system obtains.