The Hymenolepis diminuta-golden hamster (Mesocricetus auratus) model for the evaluation of gastrointestinal anticestode activity.

A novel laboratory anticestode assay was developed using Hymenolepis diminuta in the hamster. The commercial anticestode compounds, praziquantel, bunamidine, and niclosamide were active against patent infections of Hymenolepis diminuta in golden hamsters (Mesocricetus auratus) when given orally at 3.125, 100, and 200 mg/kg, respectively. The gastrointestinal nematode anthelmintics, cambendazole and mebendazole, were active at 50 mg/kg. Rafoxanide (fasciolicide) was active at 25 mg/kg, the lowest level tested. The coccidiostat, nicarbazin, was active at experimental levels (800 mg/kg and up). The anthelmintic-ectoparasiticide (endectocide), ivermectin, was inactive against the tapeworm at 0.5 mg/kg, as expected.

Pneumonia eosinofílica aguda: relato de quatro casos / Acute eosinophilic pneumonia: report of four cases

Os autores fazem um relato de quatro casos de pneumonia eosinofílica aguda (PEA) com manifestações clínicas inespecíficas, como tosse, dispnéia, febre, além dos sinais físicos de consolidação pulmonar. O quadro clínico-radiológico se notabilizou por causa de não-resposta à mutabilidade. O diagnóstico foi baseado, principalmente, na não-resposta aos quimio/antibióticos, no padrão radiológico mutável, na eosinofilia sangüínea e na resposta terapêutica obtida na utilização de corticosteróides e cambendazol

Determinaçäo de benzimidazóis em medicamentos / Determination of benzimidazoles in medicament

Os benzimidazóis tiabendazol (TZ), mebendazol (MZ) e cambendazol (CZ) foram determinados em preparaçöes farmacêuticas através de cromatografia líquida de alta eficiência de fase reversa, utilizando-se colunas LiChrospher© 100 RP 18 e LiChrosorb© RP 8, de 5 µm de tamanho de partícula, em LiChroCART© (4 mm x 12,5 cm). Foram utilizadas fases móveis com fluxo a uma velocidade de 1,0 mL/ min e as determinaçöes foram efetuadas à temperatura ambiente e com detecçäo UV a 254 nm. As duas colunas e uma única fase movel, constituída por tetraidrofurano-acetonitrila-ácido fórmico 0,5 por cento (5:25:70) foram utilizadas na determinaçäo de TZ e MZ em associaçäo (TZ - MZ). A coluna RP 18 foi utilizada para determinar TZ - MZ em comprimidos. O método foi linear nas faixas de concentraçäo de 4,0 - 40,0 µg de TZ/mL e 6,0 - 60,0 µg de MZ/mL. O coeficiente de correlaçäo (r) para TZ e MZ foi 0,9999, enquanto o erro padräo relativo de estimativa (EPRE) para TZ foi 1,64 por cento e o para MZ foi 1,03 por cento...

Structural requirements for the induction of cytochromes P450 by benzimidazole anthelmintic derivatives in cultured rabbit hepatocytes.

The effect of sulfur-containing benzimidazoles (thiabendazole, 5-hydroxy-thiabendazole, cambendazole) and sulfur-free derivatives (benzimidazole, carbendazim and 5-hydroxycarbendazim) on cytochrome P450 enzymes was investigated in primary cultures of rabbit hepatocytes considered 72 h after plating. Thiabendazole, cambendazole and carbendazim led to a significant dose-dependent increase in both EROD activity and cytochrome P4501A1/2 proteins and mRNA expression. Experiments using actinomycin D strongly suggest that these compounds have a transcriptional control on both CYP1A1 and CYP1A2 genes in primary hepatocytes. Thiabendazole increased both COH activity and P4502A protein levels. We conclude that sulfur is not a prerequisite to the P450 induction potential of benzimidazoles, while 5-hydroxylation leads to inefficient metabolites in terms of inducibility.

Genetic variability of the beta-tubulin genes in benzimidazole-susceptible and -resistant strains of Haemonchus contortus.

Benzimidazole anthelmintics are the most common chemotherapeutic agents used to remove intestinal helminths from farm animals. The development of drug resistance within helminth populations is wide-spread and can render these drugs essentially useless. The mechanism of benzimidazole resistance appears to be common to many species ranging from fungi to nematodes and involves alterations in the genes encoding beta-tubulin. During the selection process resulting in resistance, there must be quantitative changes in the population gene pool. Knowledge of these changes would indicate the mechanisms underlying the spread of resistance in the population, which in turn could be used to design more effective drug administration strategies. To this end we have identified allelic variation at two beta-tubulin genes in Haemonchus contortus using restriction map analysis of individual adults. Extremely high levels of variation were identified at both loci within a susceptible strain. In two independently derived benzimidazole resistant strains, allele frequencies at both loci were significantly different from the susceptible strain but not from each other. The same alleles at both loci, in both resistant strains, were favored by selection with benzimidazoles, suggesting that both loci are involved in determining benzimidazole resistance. These data confirm that changes in allele frequency, rather than novel genetic rearrangements induced by exposure to the drug, explain the changes associated with benzimidazole resistance. These results also show that any DNA based test for the development of benzimidazole resistance must take into account the frequency of alleles present in the population and not simply test for the presence or absence of specific allelic types.

Pneumonia eosinofílica: relato de um caso / Eosinophilic peneumonia

Os autores relatam um caso de peneumonia eosinofílica, com manifestaçöes clínicas inespecíficas com tosse, dispnéia e febre, além de sinais físicos de broncoespasmos de leve intencidade. O quadro clínico-radiológico de evoluçäo mais demorada que o habitual constitui-se em aspecto atípico na síndrome (mais de 30 dias) e o diagnóstico foi baseado principalmente no padräo radiológico alveolar mutável, na eosinofilia sangüinea e na resposta terapêutica obtida com uso de corticosteróide e cambendazol

Control of cambendazole-resistant small strongyles (Population S) with oxibendazole in a pony band: an 8 year field test (1984-1992).

Studies in a band of ponies harboring Population S benzimidazole-resistant small strongyles were initiated in 1974 and have continued for 18 years. Treatment (bimonthly) was with cambendazole for the first 4 years and with oxibendazole (OBZ) for the next 14 years. Data on the first 10 years have been published. The present investigation includes the last 8 years (4 October 1984-11 September 1992), which are the seventh through fourteenth years, of treatment with OBZ. Pre- and posttreatment mean counts of strongyle eggs (epg) and larvae (lpg) per gram of feces were determined biweekly during the current study to monitor the efficacy of OBZ. The average annual percent reductions of epg counts effected by OBZ treatments were 51%, 53%, 38%, 38%, 39%, 28%, 40%, and 19% for the seventh through fourteenth years, respectively. Similar levels of reductions were observed for lpg counts. Although OBZ was initially highly effective on this population of small strongyles, epg and lpg counts gradually declined, but have remained more or less constant since the fifth year of research. However, reductions of the counts were the lowest for the last year of the study.

Haemonchus contortus: the role of two beta-tubulin gene subfamilies in the resistance to benzimidazole anthelmintics.

The role of beta-tubulin genes in benzimidazole (BZ) resistance was investigated using one susceptible (S) and two resistant (Rt and Rc) strains of Haemonchus contortus. The Rt strain was isolated from the field on the basis of thiabendazole resistance. The Rc strain was derived from the S strain by treatment with cambendazole. cDNAs, derived from the S strain, encoding two isoforms of beta-tubulin (beta 12-16 and beta 8-9), alpha-tubulin and phosphofructokinase (Pfk) were used as probes for Southern hybridization analysis of genomic DNA digested by restriction enzymes. Genomic DNA was isolated from a pool of worms or single worms. The restriction-enzyme fragment length polymorphism (RFLP) differences among these strains depended on the enzyme and the probe used. When digested with Stu I or Hpa I, and probed under stringent conditions with beta 8-9 or beta 12-16, fewer fragments were seen in the Rt and Rc strains than in the S strain. Different hybridizing fragments were found in different individuals. The frequency of individuals bearing certain fragments hybridizing to beta 12-16 or beta 8-9 in the susceptible population was reduced significantly in the resistant populations. Some differences in RFLP between these strains were observed when probed with alpha-tubulin or Pfk, but the changes were not consistent with fragments being lost from the resistant strains as observed for beta-tubulin probes. These changes in RFLP pattern correlate with changes in the binding profiles of BZs and isoelectric isoform patterns reported previously for these strains. The data confirm that reduced heterogeneity within the population is associated with BZ resistance. Our results show that both the beta 8-9 and the beta 12-16 subfamilies of beta-tubulin are affected to a similar extent by this reduction in heterogeneity in a resistant population.

The prevalence of anthelmintic resistance of horse strongyles in The Netherlands.

A survey to determine the prevalence of anthelmintic resistance of horse strongyles was carried out with 616 horses on 22 farms. The tested drugs were cambendazole, pyrantel pamaote and ivermectin. Based on egg count reduction tests the efficacy of cambendazole varied from 0% to 93% and of pyrantel from 93% to 100%. Ivermectin treatments were 100% effective on all farms. Larval cultures after cambendazole treatments revealed exclusively cyathostome larvae. After pyrantel treatments besides cyathostome larvae other types of larvae were also found. After ivermectin treatments only a few cyathostome larvae were observed. It can be concluded that benzimidazoleresistance of cyathostomes is very common and widespread in the Netherlands. This means that benzimidazoles and pro-benzimidazoles should be excluded for strategic use in horses.

Resistance of population-B equine strongyles to thiabendazole, oxfendazole, and phenothiazine (1981 to 1987).

Critical tests were completed on foals (n = 15) naturally infected with benzimidazole (BZ)-resistant population-B strongyles during the period between 1981 and 1987. Thiabendazole at a dosage of 44 mg/kg was tested in 8 foals, oxfendazole at 10 mg/kg was tested in 4 foals, and phenothiazine at 55 mg/kg, cambendazole at 20 mg/kg, and fenbendazole at 5 mg/kg were tested in 1 foal each. Efficacies of thiabendazole, cambendazole, and fenbendazole against the 5 species of BZ-resistant small strongyles (Cyathostomum catinatum, Cyathostomum coronatum, Cylicocylus nassatus, Cylicostephanus goldi, and Cylicostephanus longibursatus) were partial. Removals in the aggregate averaged 48%, 52%, and 68%, respectively, indicating continued resistance of the 5 species of small strongyles to thiabendazole, cambendazole, and fenbendazole. In contrast, oxfendazole was efficacious, removing an aggregate average of 95% of the 5 BZ-resistant species of small strongyles in the 4 foals. This apparent reversion to susceptibility to oxfendazole may be attributable to paucity of reference data (1 test foal) done in 1976. All 5 species of the BZ-resistant small strongyles had cross resistance to phenothiazine (38% aggregate removal), whereas 9 of the BZ-susceptible species were effectively (99%) removed. This suggests a similar mode of action between phenothiaznie and the BZ compounds.

Effect of cambendazole and haloxon on the carbohydrate metabolism of Ascaridia galli and Heterakis gallinae (Nematoda).

Cambendazole 10(-4) M significantly reduced the level of glycogen in both the parasites. Lactic acid level was found enhanced. Oxygen consumption was suppressed by 63 and 94% in A. galli and H. gallinae, respectively, by 10(-4) M cambendazole. Haloxon did not cause any significant change in glycogen and lactic acid level in either parasite, but reduced oxygen consumption by 23 and 31% in Ascaridia galli and Heterakis gallinae, respectively.

Motility response of levamisole/benzimidazole-resistant Haemonchus contortus larvae.

Electronic measurements of the motility of third stage larvae of a susceptible and a levamisole/benzimidazole-resistant strain of Haemonchus contortus were made after incubation in solutions of anthelmintics for 24 h. Results confirmed the resistance to benzimidazoles, but failed to show differences in response to levamisole. Visual observations of paralysis of first and third stage larvae in solutions of levamisole also failed to show significant differences between the two strains. The tests as conducted failed to demonstrate levamisole resistance, suggesting that nematode strains may vary in their mechanisms of resistance to levamisole.

Colorimetric assay for the detection of benzimidazole resistance in trichostrongyles.

A modified version of the aphid tile-test, which is used to detect insecticide resistance in single adult aphids that are resistant or susceptible to organophosphate or carbamate insecticides, was used to compare the levels of non-specific esterases in strains of the trichostrongyle nematodes Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis which were known to be resistant or susceptible to benzimidazole (BZ) anthelmintics. This colorimetric assay has shown that there is significantly more non-specific esterase in the infective-stage larvae of BZ-resistant strains than in susceptible strains and this may prove to be of use in the detection of resistance to benzimidazole anthelmintics.

Larval development test for detection of anthelmintic resistant nematodes.

The growth, using freshly cultured Escherichia coli with ampicillin or heat-treated lyophilised E coli as a food source, of the larvae of the mouse nematode Nematospiroides dubius and the infectivity of resulting third stage larvae were determined. Concentrations of E coli between 0.5 and 1 mg dry weight ml-1 permitted optimal larval development for both N dubius and Trichostrongylus colubriformis. Development of larvae of susceptible and cambendazole-resistant strains of Haemonchus contortus in thiabendazole solutions showed clear differences between the strains and the larval development test was more sensitive than the egg hatch test. The test also detected a levamisole resistant strain of H contortus, although the degree of resistance could not be adequately measured. It is concluded that the test can be run with any anthelmintic to which resistance is suspected.

Effect of some anthelmintics on malate dehydrogenase activity and mortality in two avian nematodes Ascaridia galli and Heterakis gallinae.

Cambendazole and tiabendazole at 10(-4) M concentrations caused mortality in both the parasites after 10 min and 20 min, respectively. H. gallinae was killed by 10(-4) M haloxon but A. galli remained alive even after 60 min exposure. The effect of these drugs was found to be irreversible since no resumption of activity was observed when the parasites were returned to normal saline solution. The ratio of oxaloacetate reduction to malate oxidation in the homogenates of A. galli and H. gallinae was 4.38:1 and 3.17:1 respectively. Cambendazole at 10(-3) M inhibited the enzymic activity in both directions by 100% in both A. galli and H. gallinae. 10(-3) M tiabendazole, however, inhibited the malate oxidation by 82.8 and 60.8% and oxaloacetate reduction by 76.6 and 92% in A. galli and H. gallinae, respectively. Haloxon had little effect on malate dehydrogenase activity of any of the parasite. Assay of malate dehydrogenase, following the in vitro drug treatment cambendazole and tiabendazole, exhibited moderate inhibition of the activity in both the parasites.

Strongyloides ratti and S. stercoralis: effects of Cambendazole, Thiabendazole and Mebendazole in vitro

Os efeitos da incubaçäo de três antihelmínticos, tiabendazol, mebendazol e cambendazol sobre Strongyloides foram comparados. Nenhuma droga afetou a eclosäo dos ovos de S. ratti ou a viabilidade de larvas infectantes ou vermes adultos parasitários, mas todas as três inibiram a formaçäo de larvas de S. ratti. Além disso, cambendazol, mas näo tiabendazol ou mebendazol, diminuiu a viabilidade de larvas de primeiro e segundo estágio de S. ratti. As três drogas näo tiveram efeito sobre vermes adultos de vida livre isolados, de S. stercoralis, mas todas evitaram o desenvolvimento de larvas rabditiformes de S. stercoralis. Tianbendazol e mebendazol näo tiveram efeito sobre a infectividade de larvas infectantes de S. ratti ou de S. stercoralis, mas a infecçäo com esses vermes foi anulada por incubaçäo prévia com cambendazol. Esses resultados indicam que cambendazol age de modo diferente das outras duas drogas. Uma vez que ele é ativo contra larvas migrando através dos tecidos, é potencialmente de muito maior valor que a tiabendazol ou mebendazol na terapêutica da estrongilodíase