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Gerald C Coles

Publications and source records attributed to Gerald C Coles.

17 recordsLinked to original sources
PubMed2004

Schistosomiasis control: keep taking the tablets.

Despite the limited reports of praziquantel resistance, the relative success of chemotherapy-based control programmes for schistosomiasis has prompted overdue efforts to expand the use of cheap, generic, praziquantel in sub-Saharan Africa. The likely impact of such programmes on the development and spread of praziquantel resistance is uncertain, but this possibility reinforces the need for monitoring the spectrum of praziquantel sensitivity of schistosome populations and for an improved knowledge of the precise targets for the action of the drug. The search for alternatives to praziquantel and other tools for control of schistosomiasis must continue.

Administration, Oral↗
PubMed2003

Genetic analysis of praziquantel resistance in Schistosoma mansoni.

To determine the genetic basis of the resistance of Schistosoma mansoni to praziquantel (PZQ) and to understand whether the resistance is dominant or recessive trait, a schistosome cross was undertaken between a PZQ-susceptible and a PZQ-resistant isolate using infections of the single-sex cercariae which were identified by a direct W1-specific PCR technique. The resistances of F1 and F2 generation to PZQ were evaluated using in vitro egg, miracidial and cercarial tests. The F1 hybrid progeny from crosses between the susceptible and resistant isolates were resistant to PZQ. The resistant phenotype reappeared in the F2 progeny. It can thus be considered that the PZQ resistance behaves like a dominant trait.

Animals↗
PubMedDate not supplied

Resistance of Schistosoma mansoni to praziquantel: is there a problem?

Evidence for resistance to praziquantel (PZQ) in Schistosoma mansoni has been sought in parasites taken from treated, but uncured human patients, and in a laboratory isolate of S. mansoni subjected to successive passages under drug pressure. Patients from villages in Egypt and Senegal have yielded isolates that can tolerate higher dosages of PZQ than other ostensible control isolates when passaged and subjected to drug treatment in mice. In vitro tests on these and the laboratory-selected isolate support the conclusion that a degree of resistance to PZQ can occur in S. mansoni, but the levels of drug resistance found so far are low. Preliminary studies have begun on these isolates to identify genetic, physiological and morphological characteristics associated with PZQ resistance and some of these may find use as markers for monitoring whether or not resistance is developing in endemic areas where the drug is used. More intensive application of PZQ can be expected in future, particularly in other parts of Africa, and vigilance will be needed to ensure that it continues to be useful as a drug for treatment of schistosomiasis. Further work is needed to elucidate the mode of action of PZQ and there is already a need for alternative drugs to treat PZQ-resistant schistosomiasis, such as already exists in northern Senegal.

Animals↗
PubMedDate not supplied

Cattle nematodes resistant to anthelmintics: why so few cases?

The apparent lack of anthelmintic resistant nematodes in cattle is due to the management systems used with most cattle and the lack of surveys for resistance. With extensive beef grazing or with beef suckler herds a large percentage of worms are in refugia (not exposed to anthelmintic) and few anthelmintic treatments are used. With dairy replacement heifers resistance can become a problem unless only first year animals are treated and different fields are used for grazing the animals each year. Intensive beefproduction on grass is unsustainable and in New Zealand resistance is already becoming a serious problem. Individual farms require monitoring for resistance and steps taken to avoid the introduction of resistance. New validated tests and surveys for resistance are required as the extent of anthelmintic resistant bovine nematodes is not known.

Animal Husbandry↗