An optimized background regimen design to evaluate the contribution of levofloxacin to multidrug-resistant tuberculosis treatment regimens: study protocol for a randomized controlled trial

Background

Current guidelines for treatment of multidrug-resistant tuberculosis (MDR-TB) are largely based on expert opinion and observational data. Fluoroquinolones remain an essential part of MDR-TB treatment, but the optimal dose of fluoroquinolones as part of the regimen has not been defined.

Methods/design

We designed a randomized, blinded, phase II trial in MDR-TB patients comparing across levofloxacin doses of 11, 14, 17 and 20 mg/kg/day, all within an optimized background regimen. We assess pharmacokinetics, efficacy, safety and tolerability of regimens containing each of these doses. The primary efficacy outcome is time to culture conversion over the first 6 months of treatment. The study aims to determine the area under the curve (AUC) of the levofloxacin serum concentration in the 24 hours after dosing divided by the minimal inhibitory concentration of the patient’s Mycobacterium tuberculosis isolate that inhibits > 90% of organisms (AUC/MIC) that maximizes efficacy and the AUC that maximizes safety and tolerability in the context of an MDR-TB treatment regimen.

Discussion

Fluoroquinolones are an integral part of recommended MDR-TB regimens. Little is known about how to optimize dosing for efficacy while maintaining acceptable toxicity. This study will provide evidence to support revised dosing guidelines for the use of levofloxacin as part of combination regimens for treatment of MDR-TB. The novel methodology can be adapted to elucidate the effect of other single agents in multidrug antibiotic treatment regimens.

Trial registration

ClinicalTrials.gov, NCT01918397. Registered on 5 August 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2292-x) contains supplementary material, which is available to authorized users.

Towards a standardised surveillance for Trichinella in the European Union

Each year, more than 167 million pigs in the European Union (EU) are tested for Trichinella spp. under the current meat hygiene regulations. This imposes large economic costs on countries, yet the vast majority of these pigs test negative and the public health risk in many countries is therefore considered very low. This work reviewed the current Trichinella status across the EU as well as the national level of monitoring and reporting. It also reviewed which animal species were affected by Trichinella and in which species it should be surveyed. This information was used to design a cost-effective surveillance programme that enables a standardised monitoring approach within the EU. The proposed surveillance programme relies on identifying sub-populations of animals with a distinct risk. Low-risk pigs are finisher pigs that originate from so-called controlled housing. All other pigs are considered high-risk pigs. Controlled housing is identified by the application of a specific list of management and husbandry practices. We suggest that member states (MS) be categorised into three classes based on the confidence that Trichinella can be considered absent, in the specified sub-population of pigs above a specified design prevalence which we set to 1 per million pigs. A simple and transparent method is proposed to estimate this confidence, based on the sensitivity of the surveillance system, taking into account the sensitivity of testing and the design prevalence. The probability of detecting a positive case, if present, must be high (>95 or >99%) to ensure that there is a low or negligible risk of transmission to humans through the food chain. In MS where the probability of a positive pig is demonstrated to be negligible, testing of fattening pigs from a sub-population consisting of pigs from controlled housing can be considered unnecessary. Furthermore, reduced testing of finishers from the sub-population consisting of pigs from non-controlled housing might even be considered, if conducted in conjunction with a proportionate sampling scheme and a risk-based wildlife surveillance programme where applicable. The proposed surveillance programme specifies the required number of samples to be taken and found negative, in a MS. A MS with no data or positive findings will initially be allocated to class 1, in which all pigs should be tested. When a MS is able to demonstrate a 95% or 99% confidence that Trichinella is absent, the MS will be allocated to class 2 or 3, in which the testing requirement is lower than in class 1.

Report of Trichinella spiralis in a red fox (Vulpes vulpes) in Northern Ireland

No systematic studies of the occurrence of Trichinella in wildlife have been carried out in Northern Ireland (NI) in recent years, and the last reports of trichinellosis in livestock and human outbreaks in NI date back to 1979 and 1945, respectively. In this study, covering the period 2003/2004 and 2007/2008, a total of 443 red foxes (Vulpes vulpes) were collected throughout the country and screened for trichinellosis using a modified muscle digest method. One examined animal was found to be infected with larvae from Trichinella spiralis, indicating a national prevalence in NI of Trichinella in foxes of 0.2%. This prevalence compares well to the findings reported from the bordering Republic of Ireland [Rafter, P., Marucci, G., Brangan, P., Pozio, E., 2005. Rediscovery of Trichinella spiralis in red foxes (Vulpes vulpes) in Ireland after 30 years of oblivion. J. Infect. 50, 61-65] and could be a further indication for a sylvatic Trichinella life cycle existing independently from the domestic cycle.

The effects of stage-specific selection on the development of benzimidazole resistance in Haemonchus contortus in sheep

Resistance to the benzimidazole (BDZ) class of anthelmintics in nematodes of sheep has become a common and global phenomenon. The rate at which the selection process and development of resistance occurs is influenced by a number of factors. Of these, the effects of stage-specific exposures to anthelmintic were investigated with a BDZ-resistant strain of Haemonchus contortus (HCR) over five parasite generations. Sheep were infected at each generation with the HCR strain and were treated with thiabendazole (TBZ), either 5 days post-infection (p.i.) (larval line), 21 days p.i. (adult line), or left untreated (no selection line). Additionally eggs from each generation were exposed to TBZ (egg line). Geometric worm burdens were calculated from post-mortem worm counts, both at the start of the study, and after the final selection studies for each of the selection lines. Egg hatch assays (EHAs) were also conducted throughout the study. All data relating to worm burdens and EHAs for each generation were analysed by linear regression to produce dose titration curves and lethal dose(50) (LD(50)) values for each of the selection lines. Over the five generations, LD(50) values on dose-response were increased and worm survival occurred at higher dose rates of TBZ irrespective of the parasite stage exposed to treatment. A similar picture was seen with ED(50) values, which showed a fluctuating but generally upward trend for each of the three selection lines. In contrast, LD(50) and ED(50) values were decreased in the no selection line, indicating some degree of reversion albeit to levels still considered to be BDZ-resistant.

Anthelmintic resistance detection methods

The development of species and populations of parasitic helminths with resistance to one or more anthelmintics is an increasing problem world-wide. The majority of currently available anthelmintics used to control parasitic nematodes of cattle and sheep belong to only three main groups, the benzimidazoles, imidazothiazoles and the avermectins/milbemycins. The successful implementation of helminth control programmes designed to limit the development of resistance in nematode populations depends to some degree on the availability of effective and sensitive methods for its detection and monitoring. A variety of in vivo and in vitro tests have been developed for the detection of nematode populations resistant to the main anthelmintic groups, but each suffers to some degree from reliability, reproducibility, sensitivity and ease of interpretation. This review covers those tests that have been reported and described and highlights some of their strengths and weaknesses.

Follow-up of benign results of stereotactic core breast biopsy

RATIONALE AND OBJECTIVES

The purpose of this study was to obtain long-term follow-up data on women with benign histologic results of a breast stereotactic core needle biopsy (CNB).

MATERIALS AND METHODS

Mammography charts of 300 consecutive women who underwent prone stereotactic CNB with digital radiography were reviewed. Women with frankly malignant or suspicious histologic findings (51 patients) or a technically unsuccessful stereotactic CNB (one patient) were excluded. The remaining 248 benign core biopsies in 229 women were included in the study.

RESULTS

Follow-up mammograms were obtained for 152 lesions with benign histologic results following stereotactic CNB. The mean length of follow-up after stereotactic CNB was 34.6 months. Cancer was diagnosed in six women who underwent surgical biopsies 1/2 to 30 months after benign stereotactic CNB. An initial chart review demonstrated that no follow-up data were available for 64 lesions, and information was missing for an additional seven.

CONCLUSION

SCNB remains a sampling procedure that can result in false-negative histologic results. Intrinsic procedural issues were identified that could minimize the potential for missing a malignancy. Goals for patient compliance with follow-up recommendations fell short of expectations.

Emergency department coverage by academic departments of radiology

RATIONALE AND OBJECTIVES

The purpose of this study was to survey academic radiology departments to determine how emergency radiology coverage is handled and whether there are any prerequisites for those individuals providing this coverage.

MATERIALS AND METHODS

The authors developed a simple two-page survey and sent it to a total of 608 program directors, chiefs of diagnostic radiology, chairpersons, and chief residents at academic departments of radiology.

RESULTS

Of the 608 surveys sent, 278 (46%) were returned. More than half of the departments have an emergency radiology section that provides "wet read" coverage during the day, and most academic departments cover the emergency department during the night and on weekends. Nighttime and weekend coverage is handled mostly by residents. Most departments give time off for lunch, with few other prerequisites for faculty who provide emergency coverage. Sixty percent of the departments have teleradiology capability, and many use it for emergency department coverage.

CONCLUSION

These results can serve as the basis for discussion and comparison with other institutions regarding a variety of aspects of emergency department coverage.

Occurrence of anthelmintic resistant nematodes on sheep farms in England and goat farms in England and Wales

A survey in 1992 showed that 44 per cent of the sheep farms tested in the south west and 15 per cent of those in the north east of England had parasitic nematode worm burdens which were resistant to benzimidazole anthelmintics, and that 65 per cent of the non-dairy goat farms tested in England and Wales had resistant worms. Ostertagia circumcincta was the main species in sheep and Haemonchus contortus in goats. The resistance to benzimidazoles was diagnosed by a combination of an egg hatch assay and a larval development test. A simplified faecal egg count reduction test was used to investigate sheep and goat farms for signs of ivermectin resistance but no positive cases were detected. The initial identification of levamisole resistance on one farm, both from a faecal egg count reduction test and a positive larval development test, was confirmed by a 'dose and slaughter' trial.

Potential for misinterpretation of the faecal egg count reduction test for levamisole resistance in gastrointestinal nematodes of sheep

The faecal egg count reduction test (FECRT) is widely used to assess the presence or absence of levamisole resistance in gastrointestinal nematodes in sheep flocks. However, in a recent study the FECRT appeared to falsely indicate the presence of levamisole resistance. One possible explanation for this result could have been that the anthelmintic failed to completely remove all immature stages of levamisole-susceptible strains, which then developed into egg laying adults and gave misleading results in the FECRT. Artificial infection of lambs with levamisole-susceptible, benzimidazole-resistant strains of Ostertagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis was followed by treatment with levamisole when the infections were between 2 and 10 days old. Levamisole was 84%, 88% and 98% effective against these immature stages of three species, respectively. The positive control, ivermectin, was more than 99% effective against all three species. The percentage faecal egg count reduction on samples taken 11 and 20 days post-treatment with levamisole was 80% and 78%, respectively. These results demonstrate that, due to the maturation of immature stages, the FECRT based on faecal eggs counts taken 11 or more days after treatment may give results indicative of levamisole resistance despite the absence of levamisole resistant strains of gastrointestinal nematodes.

Development of immunity to lungworm in vaccinated calves treated with an ivermectin sustained release bolus or an oxfendazole pulse release bolus at turnout

The ivermectin sustained release bolus (IVSRB), when used at turnout as recommended, will provide season-long control of parasitic bronchitis, thus obviating the need for use of a lungworm vaccine. However, some concerns have been expressed that calves treated with an IVSRB will receive so little exposure to Dictyocaulus viviparus that it will compromise their immunity in subsequent grazing seasons, which would be of particular importance in dairy herds. Although there is evidence that IVSRB-treated calves can develop immunity to D. viviparus when exposed to pasture infection, it was considered worthwhile to evaluate the compatibility of the IVSRB and lungworm vaccination to allow veterinary surgeons the option of using these products concurrently when they have particular concerns about the long term immune status of replacement dairy heifers. Thirty-two dairy replacement heifers were vaccinated with two doses of lungworm vaccine and, at turnout, half the calves received an IVSRB and the remainder an oxfendazole pulse release bolus (OPRB). At the end of the grazing season four replicate bolus treated pairs and four parasite-naive calves were challenged with 1000 D. viviparus infective larvae. At slaughter there was a 95% and 93% reduction in D. viviparus burdens in the IVSRB and OPRB treated calves respectively, compared with the unvaccinated, untreated controls. These results indicate that where it is considered necessary to use lungworm vaccination in addition to an IVSRB or an OPRB, the compatibility of these products with lungworm vaccine will allow development of a protective level of immunity to D. viviparus.

Occurrence of fibroadenomas in postmenopausal women referred for breast biopsy

OBJECTIVE

To examine the occurrence of breast fibroadenomas in postmenopausal patients referred for breast biopsy.

DESIGN

A retrospective review of breast biopsy outcome and of patient demographics, including menstrual and hormonal status.

SETTING

The Tucson Breast Center, a large outpatient breast cancer detection clinic affiliated with the University of Arizona Health Sciences Center in Tucson, Arizona.

PARTICIPANTS

All women seen at the Tucson Breast Center between 1985 and 1990 who were referred for breast biopsy.

RESULTS

A total of 100 fibroadenomas were found in 709 breast biopsies whose results were known. Fifty-two of these were in premenopausal women and 44 in postmenopausal women; the menopausal status of four women was unknown. In postmenopausal women, 11 of the 44 patients reported hormone use. Fibroadenomas constituted 20% (39 of 195) of the benign masses and 12% (39 of 339) of all breast masses in postmenopausal women. Fibroadenomas constituted 10% (44 of 447) of all biopsies in postmenopausal women, including those with breast masses, abnormal calcifications, or other lesions.

CONCLUSION

Noncalcified fibroadenomas of the breast are not confined to young women and may constitute a small but noteworthy proportion of lesions coming to breast biopsy in postmenopausal women.

Detection of anthelmintic resistant nematodes in sheep in southern England by a faecal egg count reduction test

On five farms identified by in vitro tests to have benzimidazole resistance, and on one farm with apparent anthelmintic failure, faecal egg count reduction tests were performed using benzimidazoles, levamisole and ivermectin. With benzimidazoles efficacy was less than 70 per cent on all farms, confirming the validity of the in vitro tests to detect benzimidazole resistance. On two farms levamisole had an efficacy of less than 90 per cent but laboratory tests failed to demonstrate levamisole resistance. Ivermectin reduced egg counts by 100 per cent on all farms.

Mammographic surveillance of breast cancer patients: should the mastectomy site be imaged?

OBJECTIVE

This study evaluated the usefulness of routine mammography of the mastectomy site in women who have been treated for breast carcinoma.

MATERIALS AND METHODS

From a retrospective review of medical records and mammographic examinations of 827 patients who had mastectomies, the following information was obtained: demographic data, type of breast reconstruction (if any), length of follow-up after mastectomy, evidence of local recurrence, and results of physical examination of the breast and mammography immediately before diagnosis of local recurrence.

RESULTS

Local recurrences of breast cancer were seen in 39 (4.5%) of the 859 breasts in the study group. All patients had a physical examination of the breast and mammography within 3 months of the diagnosis of recurrent breast carcinoma. Mammography of the mastectomy site did not show any recurrences that were not suspected on the basis of physical examination. For two of 20 patients, spot-compression views of palpable abnormalities showed thickening of the surgical scar. In four patients with pain in the chest wall, no abnormalities were found on physical examination or mammograms, but bone scintigrams showed metastasis to the ribs.

CONCLUSION

Our results indicate that mammographic imaging of the mastectomy site does not increase the detection of locally recurrent breast cancer.

Association of cyclosporin A with acquired cystic kidney disease of the native kidneys in renal transplant recipients

Acquired cystic kidney disease (ACKD) is a common complication in patients treated with long-term dialysis. Previous studies performed prior to the cyclosporin A (CsA) era indicate that successful renal transplantation causes regression of ACKD. Little has been published, however, on the occurrence of ACKD in CsA-treated transplant recipients. We conducted a prospective sonographic study in 33 renal transplant recipients and 32 dialysis patients to evaluate the effect of CsA on ACKD in transplant recipients. Transplant recipients had a lower prevalence (39% vs. 56% in dialysis patients) and severity (smaller kidneys and lower cyst grades) of ACKD when compared with dialysis patients. Renal cell carcinoma was found in two dialysis patients. Using multiple regression analysis, we found that the use of CsA was significantly correlated with the presence of ACKD in transplant recipients (57% in CsA-treated vs. 8% in non-CsA-treated patients). We conclude that renal transplantation reduces the prevalence and severity of ACKD in the native kidneys; however, among transplant patients, CsA administration is associated with a greater prevalence of ACKD.

Sonographic image degradation after barium enema

RATIONALE AND OBJECTIVES

The authors previously showed that barium does not interfere with abdominal sonography performed after a biphasic upper gastrointestinal tract examination. This study was designed to assess the impact of a barium enema (BE) examination on the quality of abdominal sonography performed immediately after the barium enema.

METHODS

Forty patients scheduled for routine barium enemas (22 air contrast and 18 solid column) were prospectively examined with abdominal sonography before and after their BEs. The resulting 80 sonograms were randomized; three radiologists blindly assessed the quality of images of each of six anatomic areas (aorta, pancreas, porta hepatis, gallbladder, and the right and left lobes of the liver).

RESULTS

There was no statistically significant degradation of the images for the right and left lobes of the liver and the pancreas. However, the images for the gallbladder, porta hepatis, and aorta had a statistically significant (P < .05) degradation of their ultrasound quality following barium enema.

CONCLUSIONS

Unlike upper gastrointestinal tract examination, BE examination does interfere with the quality of a subsequent abdominal ultrasonography. Thus, when both studies are required, sonography should be performed first.

Moonlighting during the radiology residency

RATIONALE AND OBJECTIVES

The authors surveyed current residents and practicing radiologists to assess motivations for and attitudes about radiology moonlighting during residency.

METHODS

One thousand one hundred current fourth-year radiology residents and 1,100 practicing radiologists who finished training within the past 10 years were surveyed. Information was solicited concerning motivations for and attitudes toward moonlighting and the effects of moonlighting on residents' training. Current residents were compared with former residents to assess changes in attitudes about moonlighting.

RESULTS

There were no important differences in the practicing and training cohorts. Of each group, 52% moonlighted. Debt was the main motivating factor influencing a resident's decision to moonlight. Moonlighters owed significantly more money (average debt, $25,804) at the beginning of their residency than did non-moonlighters (average debt, $19,554). In addition, 72% of moonlighters had to begin loan repayments during training with average monthly payments of $284. Departmental policy was less of an influencing factor. There was no statistical difference in the way moonlighters and non-moonlighters spent their time with respect to clinical work, reading radiology, or participating in research.

CONCLUSIONS

Residents moonlight primarily for financial reasons but also perceive a positive educational benefit. Although no significant negative effects on the residency were found in this study, rising debt, decreased forbearance of repayment, and possible resultant increases in the amount of time spent moonlighting, might eventually affect resident's productivity in more traditional residency activities.

A survey of benzimidazole resistant nematodes in sheep in three countries of southern England

Faecal samples were collected from 209 randomly selected sheep farms in southern England, and the nematode eggs extracted were tested by an egg hatch assay and by a larval development test for their resistance to benzimidazoles. Benzimidazole resistance was found on 35 per cent of farms tested in East Sussex, 44 per cent in Oxfordshire and 61 per cent in West Sussex.

Effectiveness of strategic anthelmintic dosing in controlling Haemonchus contortus infections in sheep in the United Kingdom

The strategic use of anthelmintics in the control of infections of Haemonchus contortus in ewes and lambs, was investigated in a series of paddock trials. The levels of infection and clinical signs associated with the presence of either benzimidazole-resistant or benzimidazole-susceptible strains of H contortus in lambs were controlled by regular drenching with levamisole or mebendazole, respectively, or by the strategic use of closantel in combination with mebendazole. In the latter case, control was achieved by dosing either the ewes in the early part of the grazing season, or the lambs from June onwards. It was concluded that worm control strategies based on closantel could provide effective control of both benzimidazole-susceptible and benzimidazole-resistant strains of H contortus on farms in the United Kingdom.

Effectiveness of clean grazing strategies in controlling Haemonchus contortus infections in sheep in the United Kingdom

The effectiveness of clean grazing systems for controlling the sheep abomasal parasite Haemonchus contortus under experimental conditions was monitored for a grazing season in ewes and lambs carrying either benzimidazole-susceptible or resistant populations of the parasite. Both preventive and evasive strategies failed to give effective control of H contortus. Lambs grazing with ewes that had received no anthelmintic showed clinical signs of haemonchosis by early July. Lambs from ewes dosed with a benzimidazole (mebendazole) before turn out, developed clinical signs of haemonchosis later in the season. The presence of anthelmintic resistant genotypes had a significant effect on the appearance of clinical signs, and on the epidemiology and control of disease. It was concluded that alternative worm control strategies will be required for the effective control of H contortus in the United Kingdom.

Prospective comparison of plain abdominal radiography with conventional and digital renal tomography in assessing renal extracorporeal shock wave lithotripsy patients

Most publications citing the effectiveness of renal extracorporeal shock wave lithotripsy have used plain abdominal radiography to assess residual calculi after treatment. We compared radiologist sensitivity and specificity in the detection of calculi on plain abdominal radiographs versus conventional film-screen and digital renal tomograms in extracorporeal shock wave lithotripsy patients. Of the patients 50 were imaged before and within 24 hours after lithotripsy. Six radiologists evaluated the resultant 300 studies for the presence and location of calculi. The mean sensitivity for digital tomograms was 83% for pre-lithotripsy and post-lithotripsy studies, which was significantly higher than for plain abdominal radiography and conventional tomography after lithotripsy. However, there were significantly more false positive stone diagnoses associated with digital tomogram interpretation. Signal detection analysis verified the over-all superiority of digital tomography for post-extracorporeal shock wave lithotripsy imaging. Calculus detection by conventional and digital tomography is superior to detection by plain abdominal radiography. However, because we did not perform delayed imaging, it is not possible to say what impact digital tomography might have on the management of extracorporeal shock wave lithotripsy patients.

Efficacy of ivermectin against benzimidazole-resistant nematodes of sheep

Two trials involving a total of 36 Dorset horn lambs were conducted to assess the anthelmintic efficacy of ivermectin against experimental infections of benzimidazole-resistant strains of Haemonchus contortus and Ostertagia circumcincta. Two resistant strains of each of the two species were used and in each trial the lambs were allocated to three groups. One group was given 200 micrograms ivermectin/kg bodyweight orally, the second group was given 5 mg oxfendazole/kg bodyweight orally and the third group remained untreated as controls. Fourteen days after treatment the lambs were necropsied. Ivermectin was found to be more than 99 per cent to 100 per cent effective against all four benzimidazole-resistant strains, whereas oxfendazole was 78.6 per cent and 83.8 per cent effective against the H contortus strains, and 25.6 per cent and 39.8 per cent effective against the O circumcincta strains.

Comparison of breast consistency at palpation with breast density at mammography

Palpable breast consistency on physical examination was compared with the breast density on mammography for 909 consecutive patients. One of two experienced nurse practitioners palpated each patient's breasts and assigned a consistency value of 1 (little palpable breast consistency) to 4 (maximal palpable breast consistency). Seven mammographers rated the breast density on mammography as either fatty, mild, moderate, or marked parenchymal density for each breast. A low statistical correlation between the two parameters was shown. Thirty-seven percent of markedly dense breasts on mammography was rated only 1 or 2 on palpation. Thus, breast consistency judged by palpation cannot be directly correlated with the density shown on mammography and cannot be used to predict optimal radiographic technique.

The lack of sonographic image degradation after barium upper gastrointestinal examination

The presence of barium in the gastrointestinal tract after barium studies of the stomach and colon is thought to interfere with the performance of abdominal sonography. This notion results in delays in diagnosis and scheduling inconveniences when both studies are indicated at the same time. To determine if this belief is true, we prospectively obtained sonograms before and after biphasic upper gastrointestinal examinations in 40 patients. The 80 sonograms were randomized and blindly interpreted by two radiologists who used a scale from 0 to 4 to rate the appearance of six anatomic areas (gallbladder, pancreas, aorta, porta hepatis, and right and left lobes of the liver). The results showed no degradation of the image of these structures on the sonograms obtained after the barium meal compared with the prebarium sonograms. We conclude that barium does not interfere with sonography performed immediately after an upper gastrointestinal examination. Consequently, when both studies are needed, a sonogram can be scheduled after an upper gastrointestinal exam.

Anthelmintic drug resistance in the UK

The term 'anthelmintic drug resistance' describes the heritable ability of some nematode parasites to survive treatment with anthelmintic drugs at the recommended therapeutic dose levels. Genes for resistance appear to be present in many of the important pathogenic nematodes of ruminants and horses. Under intensive management systems, where heavy reliance is placed on anthelmintic drugs for worm control, the selection of resistant genotypes may result in increased reports of the drugs failing to control the nematode populations against which they are aimed. Anthelmintic resistance has been reported from many parts of the world, and in some countries multiple drug-resistant strains have emerged. In the UK, recent investigations indicate an increasing level of resistance to benzimidazoles among nematodes of sheep and horses. The incidence, diagnosis, epidemiology and implications of anthelmintic resistance are discussed.

Field observations on the control of ovine parasitic gastroenteritis in south-east England

Three worm control strategies, on a commercial farm in south east England, were monitored parasitologically for a grazing season. Three peaks of larval infection in June, late August and late October/early November occurred on paddocks grazed by dosed ewes and lambs on a new ley (preventive strategy). Lambs dosed and moved on to a hay aftermath in July (evasive strategy), had a mean egg count of 2090 by late August, attributable to infection with Haemonchus contortus. Three weekly drenching of lambs (suppressive strategy), suppressed faecal egg counts until September when the treatment interval was extended due to other on-farm commitments. In addition to these observations, autoinfection, with Haemonchus contortus, was seen to occur in lambs grazing summer turnips. An in vitro egg hatch assay, and critical efficacy trial, confirmed the presence of a benzimidazole resistant strain of Haemonchus contortus on this farm. The implications of these findings are discussed.