Anthelmintic resistance in India

Prevalence status and detection of benzimidazole resistance using AS-PCR in Haemonchus contortus of goats from Marathwada region, Maharashtra, India

This study examined Haemonchus contortus prevalence and benzimidazole resistance in eight districts of Marathwada, Maharashtra, India. A comprehensive investigation of 264 abomasa of goats collected from abattoirs and goats necropsied at the College of Veterinary Sciences and Animal Husbandry, Parbhani, revealed 21.21 % a prevalence of H. contortus. The incidence of H. contortus did not vary much across seasons and it was highest in summer (23.42 %), followed by monsoon (22.89 %), and lowest in winter (15.71 %). Statistically non-significant (p < 0.05) prevalence was observed in male and female animals. A detailed examination of 168 adult H. contortus worms from eight districts revealed the presence of all conceivable genotypes including homozygous resistant (rr), susceptible (SS), and heterozygous (Sr) BZ susceptible genotypes. The rr was the most frequent at 50 %, followed by SS at 27 % and Sr at 22 %. The presence of the SNP was observed in in all eight randomly selected and sequenced samples.

Efficacy of clinically used anthelmintics against toxocariasis of buffalo calves in Bangladesh

Toxocariasis is a paramount parasitic disease having > 50% prevalence among newborn buffalo calves in Bangladesh. The objective of this study was to compare the efficacy of clinically used anthelmintics and their subsequent effect on the haematological parameters and body weight in buffalo calves in commercial buffalo farms in coastal region. Thirty-two buffalo calves below 3 months of age with clinical Toxocara infection had been selected and treated with albendazole (ABZ), levamisole (LVM) and ivermectin (IVM). The EPG counts, hematological parameters and initial body weight of buffalo calves were recorded on the day of anthelmintic treatment (day 0). Fecal samples were collected on day 14 and 28 including hematological parameters and body weight were recorded on day 28 post-treatment. The efficacy (%) of anthelmintics were estimated by fecal egg count reduction test (FECRT). The parameters like Hb, PCV, ESR, TEC, TLC were analyzed from the blood samples. The FECRT revealed 96.83% efficacy for IVM followed by 94.23% and 85.84% for LVM and ABZ, respectively. Anthelmintic treated calves showed significant (p < 0.01) increase in Hb, PCV, TEC and body weight, and decrease in ESR and TLC as a result of worm expulsion from buffalo calves after 28 days of post-treatment. Among the tested anthelmintics, IVM was found to be more effective against toxocariasis in buffalo calves. This is a novel information on anthelmintics efficacy in buffalo calves in Bangladesh. Details study is recommended on the efficacy of anthelmintics in different buffalo management systems by in vitro egg hatch assay (EHA) test.

Comparative Evaluation of Two In Vitro Tests for Detection of Ivermectin Resistance in Haemonchus contortus of Small Ruminants in Uttar Pradesh, India

PURPOSE

Resistance against ivermectin in India has been detected solely implementing in vivo tests and there is no published report of resistance employing in vitro methods. The present study was carried out to study ivermectin resistance in H. contortus of small ruminants by two in vitro tests and to determine their efficacy in effectively detecting ivermectin resistance in the field isolates.

METHODS

The present study was carried out in the small ruminant farms of the western region of Uttar Pradesh, India. Faecal samples with high egg per gram of faeces for H. contortus were selected. Two in vitro tests namely Micro agar larval development test and larval development assay were performed for assessing ivermectin resistance in field isolates of H. contortus by subjecting the eggs to different concentrations of ivermectin aglycone.

RESULTS

The results of the two in vitro tests implicated towards the susceptibility of H. contortus isolates in the area under study. The standard deviations of the two tests was compared and was found to be statistically non-significant.

CONCLUSION

It can be said that both in vitro tests are reliable for detecting resistance against different anthelmintics including ivermectin.

Biomedical Evaluation of Lansium parasiticum Extract-Protected Silver Nanoparticles Against Haemonchus contortus, a Parasitic Worm

Here we show the novel anti-helminthic potential of Lansium parasiticum aqueous extract-protected silver nanoparticles (LAgNPs) against albendazole-resistant gastrointestinal parasite Haemonchus contortus. LAgNPs showed LD₅₀ values of 65.6 ± 32.8 nM (12 h), 139.6 ± 39.9 nM (12 h), and 64.3 ± 8.5 nM (24 h) against adult male, female, and L3 larvae, respectively. LAgNPs was also quite effective in inhibiting egg hatching, with an IC₅₀ value of 144.4 ± 3.1 nM at 48 h of exposure. Exposure to LAgNPs generated oxidative stress and mediated physical damage in the worms' tissue. A sharp increase in reactive oxygen species and nitric oxide synthase levels was prominent due to LAgNPs' exposure. In response to oxidative stress, a sharp increase of stress-responsive enzymes' activity, like catalase, superoxide dismutase, and glutathione peroxidase activity, along with the concentration of glutathione, was observed in worm tissue, which indicated a LAgNP-responsive alteration of metabolism. The results give rise to the opportunity for the development of alternative treatment for drug-resistant parasitic worms.

Multiple anthelmintic resistance in gastrointestinal nematodes of Caprines on Mountain Research Centre for Sheep and Goat at Kashmir Valley, India

The study was conducted to evaluate the status of anthelmintic resistance in Gastro-Intestinal Nematodes (GINs) of goats at an organized farm located in Kashmir, as there is no report of resistance against these parasites of goats from this temperate region, although it has been reported worldwide including India. Caprines reared at this farm exhibited reduced efficacy to multiple anthelmintics following treatments with Fenbendazole (FBZ), Closantel and Ivermectin (IVM) in Faecal Egg Count Reduction Test (FECRT). The results suggested that the overall efficacy was highest for IVM at 83.5% and 90.0% on 7^th and 14^th day post-treatment, respectively and least for FBZ at 44.3% and 62.5%, respectively, whereas the corresponding figures for closantel were 68.3% and 86.2%, respectively. The pre-treatment faecal culture revealed Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis as predominant strongyles, however, in post-treatment samples, only H. contortus was observed. Further, the infective larvae were subjected to Allele specific PCR (AS-PCR) for accurate diagnosis of BZ resistance. The AS-PCR revealed 52% of H. contortus were homozygous resistant (rr) and 17% were heterozygous (rS) on day “0” before treatment and 100% homozygous resistant (rr) on 7th day post treatment. In both T. colubriformis and T. circumcincta, 100% population was homozygous susceptible (SS) at day “0” before treatment. The overall frequency of resistant (r) allele for H. contortus was 60.5% and for susceptible allele (s) was 39.5%. For T. colubriformis and T. circumcincta the frequency of susceptible allele (s) was 100%. The survey indicated that the GINs of goats on the farm have developed multiple anthelmintic resistance to FBZ, closantel and IVM and the condition is alarming in the farm. Moreover surveillance studies about status of anthelmintic resistance in other farms (Govternment as well as Private) of Kashmir valley should be carried out at large scale to develop effective and sustainable control strategies against GI Nematodes.

Evaluation and Correlation of Multiple Anthelmintic Resistances to Gastrointestinal Nematodes Using Different Fecal Egg Count Reduction Methods in Small Ruminants of Punjab, India

PURPOSE

Concordance of multiple anthelmintic resistances for gastrointestinal nematodes in small ruminants by three average-based and two individually based fecal egg count reduction (FECR) tests was evaluated and corrected.

METHODS

Sheep and goats (≥ 8 weeks) from five farms were randomly assigned to three treatment groups (I, II, III; n = 10 per group) and one untreated control group (Group IV; n = 10). Group I received fenbendazole at the dose rate of 5 and 10 mg/kg, Group II received ivermectin at the dose rate of 0.2 and 0.4 mg/kg, and Group III received levamisole at the dose rate of 8 and 12 mg/kg body weight orally for sheep and goat, respectively. Three average-based methods of FECR (FECR₁, FECR₂ and FECR₃) and two individually based methods of FECR (iFECR₁ and iFECR₂) were evaluated.

RESULTS

For fenbendazole resistance, Spearman correlation coefficient for FECR₁ was non-significant with other formulae, but for FECR₂ with FECR₃, FECR₃ with iFECR₁ and iFECR₁ with iFECR₂ coincidence was significant at 1%, while for FECR₂ with iFECR₂ and FECR₃ with iFECR₂ it was significant at 5%. Spearman correlation coefficients for ivermectin resistance were significant at 1% level and for levamisole it showed significant coincidence at 1% for FECR₁ with FECR₂ and iFECR₁, FECR₂ with FECR₃ and iFECR₁, and iFECR₁ with iFECR₂, while for FECR₁ with FECR₃ and iFECR₂ coincidence was significant at 5% level. Concordance of kappa values indicated that the coincidence of the prevalence of anthelmintic resistance (95% CI) among the five farms was non-significant.

CONCLUSIONS

Concordance between the standard average-based FECR and individually based methods suggests that either method could be applied to small ruminant farms.

Efficacy of closantel, fenbendazole and ivermectin against GI helminths of cattle in central Kashmir

Three trials were conducted to evaluate the therapeutic efficacy of closantel (@ 7.5 mg/kg body weight, orally), fenbendazole (@ 7.5 mg/kg body weight, orally) and ivermectin bolus (@ 0.2 mg/kg body weight, orally) against gastrointestinal (GI) helminth parasites of cattle in central zone of Kashmir valley. Twenty cattle suffering from GI helminth infection were randomly selected and divided into two groups in each trial. In each trial, one group comprising of fifteen animals were treated with anthelmintic and second group comprising of five animals were kept as infected untreated control. To determine the therapeutic efficacy of different anthelmintic drugs against GI helminths, faecal samples were directly collected from rectum before treatment and on 7th, 14th and 28th day post treatment and eggs per gram of faeces was determined by using Stoll's method. Then the efficacy of different anthelmintics was calculated by employing Faecal Egg Count Reduction Test. On 14th day post treatment closantel was found to be 100 and 94.44% effective against Fasciola spp. and strongyle worms, respectively, however, it was not found effective against Trichuris spp. The efficacy of fenbendazole was 100% against Fasciola spp., paramphistomes, Moniezia spp., Trichuris spp. and strongyle worms on 14th day post treatment. Ivermectin was found to be 100% effective against Trichuris spp. and strongyle worms on 14th day post treatment, however, it was not effective against Fasciola spp. and paramphistomes.

In vitro effect of metrifonate on the indices of oxidative stress in Gigantocotyle explanatum

Helminth infections in general and digenetic trematodes in particular cause a huge economic loss globally to our livestock. Gigantocotyle explanatum is a digenetic amphistome that infects the bile ducts of water buffalo and are highly prevalent in tropical and sub-tropical countries. In the present study, effects of an organophosphate compound, Metrifonate (MF) in three doses, viz., 9.4 × 10^-5 M (Dose I), 14.4 × 10^-5 M (Dose II), and 19.4 × 10^-5 M (Dose III), have been studied in vitro, on the motility and on some enzymatic and non-enzymatic oxidative stress indices in G. explanatum. The worm's motility and their non-enzymatic oxidative stress biomarkers like lipid peroxides measured as thiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH) were disrupted significantly in a dose-dependent manner. However, the enzymatic oxidative stress biomarkers like glutathione-S-transferase (GST) and superoxide dismutase (SOD) were affected by MF treatment in a biphasic manner. Exposure to Dose I significantly stimulated the activities of both GST and SOD, whereas exposure to Doses II and III resulted into significant inhibition in a dose-dependent manner. Our findings suggest that MF has potential to be a strong and effective anthelmintic, however, further studies in vitro as well as in vivo are needed to explore further these observations and understand the exact mode of MF action in G. explanatum and other trematodes of veterinary economic importance.

Genotyping of benzimidazole resistant and susceptible isolates of Haemonchus contortus from sheep by allele specific PCR

Extensive and indiscriminate use of the benzimidazole class of drugs has led to the onset of anthelmintic resistance. In tropical countries like India, Haemonchus contortus is the most pathogenic parasite infecting sheep and goats. The widespread presence of resistant helminths (especially H. contortus) threatens the livestock farming. The use of various drugs has led to single nucleotide polymorphism that causes specific amino acid substitutions in β-tubulin protein of H. contortus to confer resistance. This emphasizes the need for a survey on the present status of resistance in India. In this study, allele specific PCR was employed to screen the presence of a SNP, a thymine-to-adenine transversion which leads to substitution of amino acid in codon 200 of β-tubulin gene that is correlated specifically with BZ resistance. Third stage larvae (L3) from pooled faecal cultures of four organized sheep farms served as a source of genomic DNA for identification of H. contortus and further genotype analysis. A total of 1000 larvae was screened, out of which 673 larvae were identified as H. contortus. Among 673 H. contortus larvae, 539 larvae (80 %) were genotyped as homozygous resistant (rr) and remaining 134 (20 %) were heterozygous susceptible (Sr) by allele specific PCR. The concluded resistance status reasons out the failure of anthelmintic drug in treating ruminants. Immediate steps are needed to avoid further aggravation of the problem. Target selective treatment by reviewing the resistance status of individual drugs, appropriate use of anthelmintic drugs and other control strategies will provide a pragmatic option for delaying the further spread of anthelmintic resistance.

Survey on anthelmintic resistance to gastrointestinal nematodes in unorganized goat farms of Tamil Nadu

One of the major problems in small ruminant farms is emergence of anthelmintic resistance (AR) to commonly used dewormers. This study investigated AR to gastrointestinal nematodes affecting goats in 27 unorganized farms in three different agro-climatic zones (Cauvery delta zone, high altitude zone and high rainfall zone) of Tamil Nadu, India. Two anthelmintics viz., albendazole (AZ) and levamisole (LEV) were used in this study as per the dose recommended by the manufacturer. Status of AR was detected by using the faecal egg count reduction test. Results revealed the presence of high level of resistance to both AZ and LEV. In the high rainfall and high altitude zones, all the farm flocks were found to be resistant to LEV. In the Cauvery delta zone, 13 farm flocks were resistant and four farm flocks showed suspect resistance to AZ. Fifteen farm flocks showed resistance and two showed suspect resistance to LEV. Further, morphological characterization of the infective larvae derived from faecal cultures indicated that by far the most predominant gastrointestinal nematode species found in goats was Haemonchus contortus.

Efficacy of fenbendazole, levamisole and ivermectin against gastrointestinal nematodes in Jamunapari goats

Efficacy of fenbendazole, levamisole and ivermectin was checked in comparison to untreated controls in twenty Jamunapari goats, naturally infected with gastrointestinal nematode parasites. Faecal examination at day 0 revealed an egg per gram of 930 ± 175.1, 1350 ± 421.1, 1060 ± 224.9 and 800 ± 279.7 in group A, B, C and D, respectively having five animals each. The results of larval culture examination revealed the presence of Haemonchus, Trichostrongylus, Oesophagostomum, Bunostomum and Strongyloides spp. in these animals. Faecal egg counts of the animals treated with fenbendazole (group A), levamisole (group B) and ivermectin (group C) were reduced by 23.66, 63.70 and 98.11%, respectively on day 14 post-treatment.

Resistência anti-helmíntica de nematóides gastrintestinais em ovinos, Mato Grosso do Sul

Entre os métodos de controle da verminose gastrintestinal em ovinos, a utilização de produtos químicos é o mais empregado. Porém, o uso indiscriminado e continuado desses produtos tem selecionado populações de helmintos resistentes aos anti-helmínticos, fenômeno relatado no mundo todo. Este trabalho teve como objetivo identificar as espécies de parasitos gastrintestinais e diagnosticar a situação da resistência anti-helmíntica em ovinos no Estado de Mato Grosso do Sul. Foram realizados testes de redução na contagem de ovos por grama de fezes (OPG) em rebanhos de dezesseis propriedades rurais; as sete formulações utilizadas continham as seguintes bases farmacológicas: Albendazol, Ivermectina, Levamisole, Triclorfon, Moxidectina, Closantel e uma contendo as três primeiras associadas. As espécies identificadas nas necropsias, em ovinos adultos, foram: Haemonchus contortus, Trichostrongylus colubriformis, Cooperia curticei, C. punctata, C. pectinata e Oesophagostomum columbianum; em ordem de prevalência. As formulações contendo Albendazol e Ivermectina não apresentaram eficácia na redução de OPG nos rebanhos testados, com médias de redução de 0,7 e -19,6%, respectivamente. Closantel apresentou eficácia média de 6,7%; Levamisole, Moxidectina e Triclorfon de 28,7, 26,8 e 65%, respectivamente; a associação das três bases (Albendazol, Ivermectina e Levamisole), uma média de eficácia de 55,8%. As percentagens médias de larvas infectantes recuperadas nas coproculturas, tanto no pré como no pós-tratamento, foram semelhantes; indicando que a resistência às bases testadas está presente em todas as espécies citadas, em maior ou menor intensidade. Os dois gêneros predominantemente resistentes são Haemonchus sp., com 86,9%; seguido por Trichostrongylus sp., com média de 47,5%; Strongyloides sp. 33,6%; Oesophagostomum, sp. 21,4% e Cooperia sp. 19,7%.

Duration of anthelmintic effect of three formulations of ivermectin (oral, injectable and pour-on) against multiple anthelmintic-resistant haemonchus contortus in sheep

We report the results of investigations that were conducted in a sheep flock in Uttaranchal, India where repeated failure of anthelmintic medication was noted. The study revealed that Haemonchus contortus in sheep had developed resistance to benzimidazoles (fenbendazole, mebendazole and albendazole), imidazothiazole (levamisole) and salicylanide (rafoxanide), while it was fully susceptible to avermectins (ivermectin). Further, the suppression of nematode egg output in faeces of sheep naturally infected with multiple anthelmintic-resistant H. contortus following treatment with ivermectin tablet (0.4 mg/kg body weight (bw), orally), ivermectin injection (1% w/v, 0.2 mg/kg bw, subcutaneously) and ivermectin pour-on (0.5 w/v, 0.5 mg/kg bw) was also studied over a period of 10 weeks post treatment. It was noted that ivermectin tablet after initial clearance of infection (faecal egg count reduction 100%), could not prevent establishment of new patent natural infection for even a single day, while ivermectin pour-on and injection prevented the establishment of new infection for 7 and 14 days post treatment, respectively. Maximum protection period (duration for which mean faecal egg count of sheep reaches 500 eggs per gram of faeces or more) of 68 days was recorded in sheep treated with injectable ivermectin, followed by pour-on (60 days) and oral (53 days) preparations.

Anthelmintic resistance: The state of play revisited

Helminthosis is one of the major constraints in the successful wool and mutton industry throughout the world. Anthelmintic Resistance (AR) is said to have been established when previously effective drug ceases to kill exposed parasitic population at the therapeutically recommended dosages. Anthelmintic resistance is almost cosmopolitan in distribution and it has been reported in almost all species of domestic animals and even in some parasites of human beings. Some of the most important species of parasites of small ruminants in which AR has been reported include: Haemonchus spp., Trichostrongylus spp. Teladorsagia spp., Cooperia spp. Nematodirus spp., and Oesophagostomum spp. All the major groups of anthelmintics have been reported for development of variable degrees of resistance in different species of gastrointestinal nematodes. This paper describes the global scenario of prevalence and methods used for detection of AR in small ruminants. Different mechanisms and contributory factors for the development of AR are discussed. Various options and alternate strategies for the control and/or delay in the onset of AR are suggested in the light of available information.

Detection of benzimidazole resistance in Haemonchus contortus using RFLP-PCR technique

Benzimidazole (BZ) resistance in Haemonchus contortus is linked primarily with the mutation in the beta-tubulin isotype 1 gene that substitute phenylalanine (Phe) to tyrosine (Tyr) at 200 codon of the gene. In the present study, a new restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR) technique has been developed for detection of BZ resistance in the beta-tubulin isotype 1 gene of H. contortus. The technique utilizes two primers viz. AvikaF and AvikaR to amplify the region containing mutation in the beta-tubulin gene followed by restriction digestion. After digestion, the 'rr' individuals (homozygous resistant) revealed 257 and 48 bp bands, the 'rS' individuals (heterozygous) showed 305, 257 and 48 bp bands, while 'SS' individuals (homozygous susceptible) revealed uncut 305 bp band. A total of 162 adult male H. contortus collected from Avikanagar, Jaipur and Bikaner regions (54 from each region) were genotyped for analyzing BZ resistance in the beta-tubulin gene. Out of which, 130 adults were 'rr' types, 20 'rS' types and 12 'SS' types. The results showed that genotypic frequencies of different genotypes (rr, rS and SS) were highly significant difference among the three regions (P<0.001). The 'rr' individuals were higher (98%) in Jaipur followed by Avikanagar (93%) and Bikaner (50%) regions. Overall, the prevalence of BZ resistant allele (r) was higher (86%) as compared to BZ susceptible allele (S) (14%). The technique was also found suitable for genotyping of larvae of H. contortus and yielded reproducible results. The study indicated that RFLP-PCR is an easy, reproducible and less expensive than allele specific PCR. This technique will be helpful in establishing the prevalence rate of BZ resistance in H. contortus and can also be utilized for existing worm control programme.

Efficacy of benzimidazole anthelmintics in goats and sheep in the Philippines using a larval development assay

The negative effects of nematodes in small ruminants can be reduced by use of dewormers but their effectiveness is increasingly limited by the emergence of anthelmintic resistance. The efficacy of benzimidazole (BZ) anthelmintics in the Philippines was estimated by an in vitro larval development assay using worm eggs recovered from faeces collected from goats and sheep. Two hundred and eighteen farms were selected to represent areas of the country with high goat and sheep populations and the full range of farm sizes, from smallholders with just a few animals to commercial and institutional farms with several hundred. Initial surveys of worm control advisers indicated that BZs have been in continuous widespread use for up to 20 years with little use of other chemical groups. A larval development assay (LDA: DrenchRite) was modified for use with BZs alone to allow up to five samples to be analysed on a single microtitre plate. The assay was validated by comparison with the faecal egg count reduction test (FECRT). The dominant nematode genera were Haemonchus and Trichostrongylus with small numbers of Oesophagostomum. The range of BZ efficacy estimated from the LDA results was 0-100% and the distribution of efficacy levels was continuous, with mean efficacy of 82 and 64% for goats and sheep, respectively. There were significant associations between efficacy and parameters measured to characterize the sampled farms: size of animal management group, FEC of sample, recent importation of stock and no access to common grazing were all correlated with decreased efficacy. Likewise, low efficacy was associated with reported frequency and number of years that BZ drenches had been used. The LDA was found to be highly suited to estimate efficacy in nematode populations from small farms where performance of a FECRT for even one chemical would be impractical. Using a larval development assay, we have demonstrated a wide efficacy range for BZs against nematodes from all sizes of goat and sheep farms in the tropics.

Anthelmintic resistance on an organized sheep farm in India

Monitoring anthelmintic resistance in strongyle nematodes by the faecal egg count reduction test and a commercial larval development assay on an organized sheep farm in the semi-arid area of Rajasthan revealed the emergence of resistance to benzimidazoles and rafoxanide and a potential risk of the development of levamisole/tetramisole resistance. A benzimidazole/levamisole combination, avermectins and closantel were each found to be efficacious.

Comparative anthelmintic activity of strategic sustained low-level administration of albendazole in feed pellets compared to single doses of closantel and tetramisole against natural ovine parasitic gastroenteritis

The strategic use of single therapeutic doses of closantel, tetramisole or sustained low-level administration of albendazole in feed pellets in controlling naturally acquired parasitic gastroenteritis in sheep was investigated on a farm in semi-arid Rajasthan, India. A total of 303 5- to 6-month-old sheep were divided into three groups. Two groups were dosed with single therapeutic doses of closantel and tetramisole and the third group was given a low-level medication with albendazole through feed pellets for 30 days. Faecal egg counts revealed significantly lower counts (p<0.001) in the group treated with closantel compared to the other two groups. The faecal egg counts in the group receiving sustained low-level albendazole rose after withdrawal of the medication but remained significantly lower than those in the group treated with tetramisole up to 7 weeks after treatment (p<0.05). On the other hand, in the group treated with tetramisole, the mean faecal egg count rose from 3 weeks after treatment and remained continuously higher than those in any other group up to 12 weeks after treatment. The closantel-treated group gained more body weight but the first six-monthly greasy fleece yield was greater in the group treated with medicated pellets. During the first 3 months of the experiment, three animals in the group treated with tetramisole died of parasitic gastroenteritis. Following sustained low-level administration of albendazole in feed pellets, the plasma disposition curve of both the sulphoxide and sulphone metabolites reached its plateau level by day 5 and remained almost constant thereafter. The comparative cost-effectiveness of the three treatment regimes during the first 3 months of treatment was best for the group treated with closantel followed by the group treated with medicated feed pellets.

Further studies on anthelmintic resistance in sheep at an organised farm in arid region of Rajasthan

Faecal egg count reduction test (FECRT) and in vitro egg hatch assay (EHA) was performed on Indian Karakul (3/4 crosses of Karakul with Malpura, Marwari and Sonadi) transported from arid region campus, Bikaner, where resistance was reported in 1996. FECRT revealed that fenbendazole and levamisole were 100% effective in reducing the egg counts. LC50 value on EHA was 0.074 +/- 0.015 microg thiabendazole ml(-1). The faecal culture examination revealed the presence of Haemonchus contortus only. It was concluded that H. contortus was fully susceptible to both benzimidazole and levamisole.

The pharmacokinetics and efficacy of long-term low-level and split-dose administration of albendazole through in-feed formulations against ovine and caprine parasitic gastroenteritis

Two trials were conducted against natural and experimentally induced parasitic gastroenteritis in sheep and goats using an in-feed formulation of albendazole to evaluate its therapeutic and prophylactic efficacy. In the first trial, albendazole was incorporated in feed pellets to deliver an average daily dose of 0.7 mg/kg body weight in order to evaluate its prophylactic efficacy. In the second trial, feed pellets were offered to deliver an average total dose of 8.0 mg/kg body weight in two equal split doses in order to evaluate its curative efficacy. Sustained plasma concentrations of the active compound, albendazole sulphoxide, and its metabolite albendazole sulphone, sufficient to prevent establishment of infection, were achieved when the animals were allowed to feed on medicated pellets for 10 consecutive days. The bioavailability of the metabolites of albendazole following the administration of a therapeutic dose in two split doses of the in-feed formulation was sufficient to remove established adult nematodes. The concentrate feed pellets could be used for self-medicating small ruminants for therapeutic use as well as for prophylaxis based on their strategic use appropriate to the epidemiology of the parasitic disease.

Effect of single and divided dose administration on the pharmacokinetics of albendazole in sheep and goat

The pharmacokinetics of albendazole were studied in sheep and goats following single and divided dose administration at nematocidal and flukicidal dose rates. The disposition curves of the metabolites indicated increased uptake of the drug both in sheep and goats at divided dose schedules compared to single dose administration (P < 0.05). The increased bioavailability of benzimidazole anthelmintics in divided dose schedules could improve their efficacy and help in extending their lives.