Changes in structural brain development after selective fetal growth restriction in monochorionic twins.

OBJECTIVES: Fetal growth restriction (FGR) may alter brain development permanently, resulting in lifelong structural and functional changes. However, in studies addressing this research question, FGR singletons have been compared primarily to matched appropriately grown singletons, a design which is inherently biased by differences in genetic and maternal factors. To overcome these limitations, we conducted a within-pair comparison of neonatal structural cerebral ultrasound measurements in monochorionic twin pairs with selective FGR (sFGR). METHODS: Structural cerebral measurements on neonatal cerebral ultrasound were compared between the smaller and larger twins of monochorionic twin pairs with sFGR, defined as a birth-weight discordance (BWD) ≥ 20%, born in our center between 2010 and 2020. Measurements from each twin pair were also compared with those of an appropriately grown singleton, matched according to sex and gestational age at birth. RESULTS: Included were 58 twin pairs with sFGR, with a median gestational age at birth of 31.7 (interquartile range, 29.9-33.8) weeks and a median birth weight of 1155 g for the smaller twin and 1725 g for the larger twin (median BWD, 32%). Compared with both the larger twin and the singleton, the smaller twin had significantly smaller cerebral structures (corpus callosum, vermis, cerebellum), less white/deep gray matter and smaller intracranial surface area and volume. Intracranial-volume discordance and BWD correlated significantly (R2 = 0.228, P < 0.0001). The median intracranial-volume discordance was smaller than the median BWD (19% vs 32%, P < 0.0001). After correction for intracranial volume, only one of the observed differences (biparietal diameter) remained significant for the smaller twin vs both the larger twin and the singleton. CONCLUSIONS: In monochorionic twins with sFGR, neonatal cerebral ultrasound reveals an overall, proportional restriction in brain growth, with smaller cerebral structures, less white/deep gray matter and smaller overall brain-size parameters in the smaller twin. There was a positive linear relationship between BWD and intracranial-volume discordance, with intracranial-volume discordance being smaller than BWD. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

The Polygenic and Monogenic Basis of Paediatric Fractures.

PURPOSE OF REVIEW: Fractures are frequently encountered in paediatric practice. Although recurrent fractures in children usually unveil a monogenic syndrome, paediatric fracture risk could be shaped by the individual genetic background influencing the acquisition of bone mineral density, and therefore, the skeletal fragility as shown in adults. Here, we examine paediatric fractures from the perspective of monogenic and complex trait genetics. RECENT FINDINGS: Large-scale genome-wide studies in children have identified ~44 genetic loci associated with fracture or bone traits whereas ~35 monogenic diseases characterized by paediatric fractures have been described. Genetic variation can predispose to paediatric fractures through monogenic risk variants with a large effect and polygenic risk involving many variants of small effects. Studying genetic factors influencing peak bone attainment might help in identifying individuals at higher risk of developing early-onset osteoporosis and discovering drug targets to be used as bone restorative pharmacotherapies to prevent, or even reverse, bone loss later in life.

Idiopathic SIADH in the premature newborn, a case report.

BACKGROUND: Hyponatremia is a common laboratory finding in premature and ill neonates. When the degree of hyponatremia is more severe, the likelihood of a pathologic entity increases. In this case report we describe a premature neonate with severe hyponatremia due to the idiopathic syndrome of inappropriate antidiuretic hormone secretion (SIADH). CASE DESCRIPTION: The patient is a male neonate, born prematurely. He was admitted to the neonatal intensive care unit and received non-invasive respiratory support. After 48 hours of life serum sodium (Na+) decreased to 115 mmol/l. Hyponatremia progressively worsened despite aggressive Na+ supplementation. The clinical and laboratory data were most consistent with severe SIADH. Fluid restriction was initiated which resulted in a gradual normalization of Na+. A causal factor for development of SIADH could not be identified. CONCLUSION: When a neonate presents with significant hyponatremia that is not responsive to conventional therapy, it is important to perform a diagnostic work-up for SIADH, even in the absence of overt triggering factors.

Cushing's disease and hypertension: in vivo and in vitro study of the role of the renin-angiotensin-aldosterone system and effects of medical therapy.

OBJECTIVE/METHODS: Cushing's disease (CD) is often accompanied by hypertension. CD can be treated surgically and, given the expression of somatostatin subtype 5 and dopamine 2 receptors by corticotroph pituitary adenomas, pharmacologically. Indeed, we recently observed that stepwise medical combination therapy with the somatostatin-analog pasireotide, the dopamine-agonist cabergoline, and ketoconazole (which directly suppresses steroidogenesis) biochemically controlled CD patients and lowered their blood pressure after 80 days. Glucocorticoids (GC) modulate the renin-angiotensin-aldosterone system (RAAS) among others by increasing hepatic angiotensinogen expression and stimulating mineralocorticoid receptors (MR). This study therefore evaluated plasma RAAS components in CD patients before and after drug therapy. In addition, we studied whether cabergoline/pasireotide have direct relaxant effects in angiotensin II (Ang II)-constricted iliac arteries of spontaneously hypertensive rats, with and without concomitant GR/MR stimulation with dexamethasone or hydrocortisone. RESULTS: Baseline concentrations of angiotensinogen were elevated, while renin and aldosterone were low and suppressed, respectively, even in patients treated with RAAS-blockers. This pattern did not change after 80 days of treatment, despite blood pressure normalization, nor after 4 years of remission. In the presence of dexamethasone, pasireotide inhibited Ang II-mediated vasoconstriction. CONCLUSIONS: The low plasma renin concentrations, even under RAAS blockade, in CD may be the consequence of increased GC-mediated MR stimulation and/or the elevated angiotensinogen levels in such patients. The lack of change in RAAS-parameters despite blood pressure and cortisol normalization suggests persisting consequences of long-term exposure to cortisol excess. Finally, pasireotide may have a direct vasodilating effect contributing to blood pressure lowering.

Preoperative normalization of cortisol levels in Cushing's disease after medical treatment: consequences for somatostatin and dopamine receptor subtype expression and in vitro response to somatostatin analogs and dopamine agonists.

CONTEXT: Corticotroph pituitary adenomas often highly express the dopamine 2 receptor (D2R) and somatostatin receptor subtype 5 (sst5). The sst2 expression is relatively low, likely resulting from downregulating effects of high cortisol levels. This may explain why the sst2-preferring somatostatin analog octreotide, compared with the multi-receptor-targeting somatostatin analog pasireotide, is generally ineffective in Cushing's disease. OBJECTIVE: Our objective was to compare sst and D2R expression levels between adenomas from patients with elevated and normalized preoperative urinary free cortisol excretion. PATIENTS AND DESIGN: Corticotroph adenoma tissue was examined from patients from group 1 (n = 22; elevated preoperative urinary free cortisol) and group 2 (n = 11; mean duration of preoperative normocortisolism 10 weeks). Somatotroph adenoma tissue from 10 acromegalic patients was examined to compare receptor expression profiles. MAIN OUTCOME MEASURES: We evaluated receptor mRNA and protein expression levels and effects of octreotide, pasireotide, and cabergoline on ACTH secretion by cultured human corticotroph adenoma cells. RESULTS: The sst2 mRNA expression in group 2 was 10-fold higher than in group 1 (P < .01), even comparable to that in somatotroph adenomas. There were no statistically significant differences in sst5 and D2R mRNA expression or in sst2, sst5, and D2R protein expression between both groups of corticotroph adenomas. In responders, octreotide (n = 2 out of 4; -30.5% ± 10.4%) was less potent than pasireotide (n = 5 out of 6; -47.0% ± 4.2%) and cabergoline (n = 3 out of 4; -41.9% ± 3.1%) with respect to inhibition of ACTH secretion by adenomas from group 2. CONCLUSIONS: After achieving normocortisolism induced by medical therapy, cortisol-mediated sst2 downregulation on corticotroph adenomas appears to be a reversible process at the mRNA but not at the protein level. Octreotide remains less potent than pasireotide and cabergoline with respect to in vitro inhibition of ACTH secretion. Whether sustained normocortisolism induced by medical therapy induces re-expression of functional sst2 protein in corticotroph adenomas and whether this increases the ACTH-lowering potency of octreotide remains to be established.

Cortisol diurnal rhythm and quality of life after successful medical treatment of Cushing's disease.

Cushing's disease (CD) is associated with severely impaired quality of life (QoL). Moreover, the physiological cortisol diurnal rhythm (CDR) is disturbed in CD. QoL can improve after successful surgery, the primary treatment for CD. We evaluated the effects of medical treatment on QoL and CDR. In 17 patients, stepwise medical treatment was applied with the somatostatin analog pasireotide, the dopamine agonist cabergoline and the adrenal-blocking agent ketoconazole. After 80 days, 15/17 (88%) patients had reached normal urinary free cortisol excretion (UFC). Subsequently, patients continued medical therapy or underwent surgery. UFC, plasma and salivary CDR and QoL-related parameters (assessed using 5 questionnaires: Nottingham Health Profile, Hospital Anxiety and Depression Scale, Multidimensional Fatigue Index-20, RAND-36, CushingQoL) were measured. At baseline, 5/17 patients had preserved CDR. In 6/12 patients with disturbed baseline CDR, recovery was observed, but without any correlation with QoL. QoL was significantly impaired according to 18/20 subscales in CD patients compared to literature-derived controls. According to the RAND-36 questionnaire, patients reported more pain at day 80 (p < 0.05), which might reflect steroid-withdrawal. Generally, QoL did not improve or deteriorate after 80 days. CushingQoL scores seemed to improve after 1 year of remission in three patients that continued medical therapy (p = 0.11). CDR can recover during successful pituitary- and adrenal-targeted medical therapy. Patients with CD have impaired QoL compared to controls. Despite the occurrence of side-effects, QoL does not deteriorate after short-term biochemical remission induced by medical therapy, but might improve after sustained control of hypercortisolism.

The hypercoagulable state in Cushing's disease is associated with increased levels of procoagulant factors and impaired fibrinolysis, but is not reversible after short-term biochemical remission induced by medical therapy.

CONTEXT: Cushing's disease (CD) is accompanied by an increased risk of venous thromboembolism. Surgery is the primary treatment of CD. OBJECTIVE: The aim of the study was to compare hemostatic parameters between patients with CD and controls and to evaluate the effect of medical treatment of CD on hemostasis. DESIGN AND SETTING: During 80 d, stepwise medical treatment was applied with the somatostatin analog pasireotide, the dopamine agonist cabergoline, and ketoconazole, which suppresses adrenocortical steroidogenesis, at four university medical centers in The Netherlands. PATIENTS: Seventeen patients with de novo, residual, or recurrent CD were included. MAIN OUTCOME MEASURES: We measured urinary free cortisol and parameters of coagulation and fibrinolysis. RESULTS: Patients with CD had significantly higher body mass index (P < 0.001), shortened activated partial thromboplastin time (P < 0.01), and higher levels of fibrinogen, Factor VIII, and protein S activity (P < 0.05) compared to healthy control subjects. In addition, fibrinolytic capacity was impaired in patients with CD as reflected by prolonged clot lysis time (P < 0.001) and higher levels of plasminogen activator inhibitor type 1, thrombin-activatable fibrinolysis inhibitor, and α2-antiplasmin (P < 0.01). There were no statistically significant differences in von Willebrand factor:antigen, antithrombin, and protein C activity. After 80 d, 15 of 17 patients had normalized urinary free cortisol excretion. Despite biochemical remission, only slight decreases in antithrombin (P < 0.01) and thrombin-activatable fibrinolysis inhibitor (P < 0.05) levels were observed. Other parameters of coagulation and fibrinolysis did not change significantly. CONCLUSIONS: The hypercoagulable state in patients with CD, which is explained by both increased production of procoagulant factors and impaired fibrinolysis, is not reversible upon short-term biochemical remission after successful medical therapy. This may have implications for the duration of anticoagulant prophylaxis in patients with (cured) CD.

Mifepristone effects on tumor somatostatin receptor expression in two patients with Cushing's syndrome due to ectopic adrenocorticotropin secretion.

CONTEXT: Two patients presented with Cushing's syndrome due to ectopic ACTH secretion. Initial localization studies included computed tomography, magnetic resonance imaging, and octreoscans ((111)In-pentreotide scintigraphy), which were negative in both patients. They were treated with the glucocorticoid receptor antagonist mifepristone, with improvement in their clinical symptoms. Follow-up octreoscans after, respectively, 6 and 12 months showed the unequivocal presence of a bronchial carcinoid in both patients. OBJECTIVE: The objective of the study was to correlate in vivo and in vitro findings in patients with ectopic ACTH-producing syndrome. METHODS: We determined the expression of somatostatin and dopamine receptors by immunohistochemistry (patients 1 and 2), quantitative PCR, and in vitro culturing of tumor cells (patient 1 only). IN VITRO RESULTS: Both tumors were strongly positive for somatostatin receptor type 2 (sst(2)) on immunohistochemistry, whereas one of the tumors (patient 1) was also dopamine receptor subtype 2 (D(2)) positive on both immunohistochemistry and quantitative PCR. Octreotide (a sst(2) preferring analog) and cabergoline (D(2) agonist) both decreased the ACTH levels in the cultured tumor cells of patient 1. CONCLUSION: We describe two patients with ACTH-producing bronchial carcinoids, in whom a direct down-regulatory effect of glucocorticoid levels on tumoral sst(2) receptor expression is suggested by a remarkable change in octreoscan status after successful mifepristone therapy. Further studies will have to demonstrate whether glucocorticoid lowering or antagonizing therapy may be used to improve the diagnostic accuracy of somatostatin receptor scintigraphy in patients with ectopic ACTH production of unknown primary origin.

Cushing's disease in dogs and humans.

BACKGROUND: Cushing's disease (CD) is a common endocrinological disorder in dogs with an estimated incidence of 1 to 2 cases/1,000 dogs/year. This is in contrast to humans in whom CD is rare. The clinical presentation of CD, however, is highly similar between dogs and humans, with characteristic signs, such as abdominal obesity, weight gain, fatigue, muscle atrophy and skin changes. Canine CD may therefore serve as an animal model for human CD, especially since therapeutic canine hypophysectomy can generate substantial amounts of primary corticotroph adenoma tissue for in vitro research purposes. In a recent study, we found that dopamine (DA) D(2) and somatostatin (SS) receptor subtypes are well expressed in canine corticotroph adenomas, but there are some distinct differences compared with the expression profile observed in human CD. These differences need to be considered when using canine CD as a model to evaluate the efficacy of novel DA/SS compounds for potential use in human CD. CASE REPORT: This case involves an 8-year-old female dog that developed signs of exercise intolerance, muscle weakness and polyuria/polydipsia due to an adrenocorticotropic hormone-secreting pituitary adenoma. The dog underwent curative transsphenoidal hypophysectomy and has remained in complete remission in the 3.5 years since surgery.

Somatostatin and dopamine receptors as targets for medical treatment of Cushing's Syndrome.

Somatostatin (SS) and dopamine (DA) receptors are widely expressed in neuroendocrine tumours that cause Cushing's Syndrome (CS). Increasing knowledge of specific subtype expression within these tumours and the ability to target these receptor subtypes with high-affinity compounds, has driven the search for new SS- or DA-based medical therapies for the various forms of CS. In Cushing's disease, corticotroph adenomas mainly express dopamine receptor subtype 2 (D(2)) and somatostatin receptor subtype 5 (sst(5)), whereas sst(2) is expressed at lower levels. Activation of these receptors can inhibit ACTH-release in primary cultured corticotroph adenomas and compounds that target either sst(5) (pasireotide, or SOM230) or D(2) (cabergoline) have shown significant efficacy in subsets of patients in recent clinical studies. Combination therapy, either by administration of both types of compounds separately or by treatment with novel somatostatin-dopamine chimeric molecules (e.g. BIM-23A760), appears to be a promising approach in this respect. In selected cases of Ectopic ACTH-producing Syndrome (EAS), the sst(2)-preferring compound octreotide is able to reduce cortisol levels effectively. A recent study showed that D(2) receptors are also significantly expressed in the majority of EAS and that cabergoline may decrease cortisol levels in subsets of these patients. In both normal adrenal tissue as well as in adrenal adenomas and carcinomas that cause CS, sst and DA receptor expression has been demonstrated. Although selected cases of adrenal CS may benefit from sst or DA-targeted treatment, its total contribution to the treatment of these patients is likely to be low as surgery is effective in most cases.

Differential regulation of human dopamine D2 and somatostatin receptor subtype expression by glucocorticoids in vitro.

Dopamine agonists (DA) and somatostatin (SS) analogues have been proposed in the treatment of ACTH-producing neuro-endocrine tumours that cause Cushing's syndrome. Inversely, glucocorticoids (GCs) can differentially influence DA receptor D(2) or SS receptor subtype (sst) expression in rodent models. If this also occurs in human neuro-endocrine cells, then cortisol-lowering therapy could directly affect the expression of these target receptors. In this study, we investigated the effects of the GC dexamethasone (DEX) on D(2) and sst expression in three human neuro-endocrine cell lines: BON (carcinoid) and TT (medullary thyroid carcinoma) versus DMS (small cell lung cancer), which is severely GC resistant. In BON and TT, sst(2) mRNA was strongly down-regulated in a dose-dependent manner (IC(50) 0.84 nM and 0.16 nM), whereas sst(5) and especially D(2) were much more resistant to DEX treatment. Sst(2) down-regulation was abrogated by a GC receptor antagonist and reversible in time upon GC withdrawal. At the protein level, DEX also induced a decrease in the total number of SS (-52%) and sst(2)-specific (-42%) binding sites. Pretreatment with DEX abrogated calcitonin inhibition by sst(2)-preferring analogue octreotide in TT. In DMS, DEX did not cause significant changes in the expression of these receptor subtypes. In conclusion, we show that GCs selectively down-regulate sst(2), but not D(2) and only to a minor degree sst(5) in human neuro-endocrine BON and TT cells. This mechanism may also be responsible for the low expression of sst(2) in corticotroph adenomas and underwrite the current interest in sst(5) and D(2) as possible therapeutic targets for a medical treatment of Cushing's disease.

Expression and functional analysis of dopamine receptor subtype 2 and somatostatin receptor subtypes in canine cushing's disease.

Cushing's disease (CD) is a severe disorder characterized by chronic hypercortisolism due to an ACTH-secreting pituitary adenoma. Transsphenoidal adenomectomy is the treatment of choice in humans with CD, but recurrences occur frequently. Finding an effective and safe medical treatment for CD may improve long-term clinical outcome. The recent demonstration of expression of somatostatin receptor subtypes (mainly sst5) and dopamine receptor subtype 2 (D2) in human corticotroph adenomas offers the possibility for medical treatment of CD with novel somatostatin analogs and dopamine agonists. Investigation of the effects of these drugs is hampered by the low incidence of CD in humans. Interestingly, CD is a frequent disorder in dogs with striking clinical similarities with CD in humans. Therefore, we investigated the expression and functional role of D2 and somatostatin receptors in corticotroph adenoma cells from 13 dogs with active CD that underwent therapeutic hypophysectomy and normal anterior pituitary cells from five dogs. Quantitative RT-PCR and immunohistochemistry revealed that both in CD and normal anterior pituitary, sst2 was the predominant receptor subtype expressed, whereas D2 was modestly expressed and sst5 was expressed only at very low levels. In primary cultures of canine adenomas (n = 7), the sst2-preferring agonist octreotide also showed the strongest ACTH-suppressive effects. In conclusion, canine corticotroph adenomas provide an interesting model to study CD, but differences in somatostatin and dopamine receptor expression between humans and dogs should be taken into account when using dogs with CD as a model to evaluate efficacy of novel somatostatin analogs and dopamine agonists for human CD.

Is the current dose of a conventional oxytetracycline formulation adequate for the management of infections in sheep?

In the veterinary industry, short-acting or conventional oxytetracycline formulations are recommended for use once a day for 4 days, at a dose of 10 mg/kg. With the large degree of antimicrobial resistance reported, the efficacy of this dose was assessed using pharmacodynamic modelling. The specific parameters evaluated were based on the time-dependent activity of the tetracycline class of antimicrobials according to the total time above minimal inhibitory concentration (T > MIC) and the ratio of the total exposure in 24 hours, represented by area under the curve (AUC24), to the minimal inhibitory concentration (AUC24:MIC). The current pharmacokinetic study examined whether the prevailing antimicrobial resistance could be overcome by doubling the recommended conventional dose. Using reported MIC data for South Africa and elsewhere, modelling indicated the presence of a large degree of resistance. In general, doubling the dose only overcame resistance of 2 bacterial species in South Africa.

Implementation of a vascular access quality programme improves vascular access care.

INTRODUCTION: In the Netherlands an access quality improvement plan (QIP) was introduced by vascular access coordinators (VAC) with the aim to decrease vascular access-related complications by preemptive intervention of malfunctioning accesses. A vascular access QIP was established in 24 centres (46% of all Dutch facilities) and a structural multidisciplinary vascular access meeting was instituted. In these centres, including 2300 patients, a protocol for enhancement of fistula creation and access surveillance programme was implemented, with instruction of physicians and nurses, and rounds to discuss complications and evaluate vascular access interventions. The number and type of vascular access, permanent catheters, thrombosis rates and number of interventions were evaluated at the start and end of the study period. RESULTS: After the surveillance programme, the number of autogenous arterio-venous fistulas (AVFs) had increased significantly from 69 to 77% (P < 0.01), while the use of temporary subclavian vein catheters declined (34% vs 11%) (P < 0.01), with a substantially higher percentage of jugular vein catheters (from 23 to 35%). Interventional treatment of malfunctioning accesses by percutaneous transluminal angioplasty (PTA) (from 0.39 to 0.50 patient/year; P < 0.001)) and surgical revisions (from 0.06 to 0.12 per patient/year; P < 0.001) also increased. CONCLUSION: These data demonstrate that a vascular access QIP resulted in placement of more autogenous AVFs, increased number of PTAs and surgical interventions. These findings suggest that a vascular access care QIP is worthwhile to improve dialysis patients' care and access morbidity.

The use of a pour-on and spray dip containing Amitraz to control ticks (Acari: Ixodidae) on cattle.

Knockdown and persistence efficacies of a pour-on containing Amitraz 1% and Cypermethrin 1% and a spray dip containing 12.5% Amitraz were compared. Knock-down and persistence efficacies of the Amitraz spray dip against Rhipicephalus (Boophilus) decoloratus and Amblyomma hebraeum were significantly higher for the duration of the trial than those of the pour-on. In the case of Rhipicephalus appediculatus and Rhipicephalus evertsi evertsi, efficacy was significantly higher on Days 2 and 5. Resistance testing prior to the start of the trial indicated that R. (B.) decoloratus was resistant to both Cypermethrin and Amitraz, yet in the case of the spray dip excellent efficacy results were obtained. It is thought that the cattle's scruffy winter coat may have hindered the spread of the pour-on, but that the thorough wetting and especially the higher concentration of active ingredient applied via the spray dip allowed this formulation to be effective. These results show that under certain conditions a spray dip containing 12.5% Amitraz may be more effective than a pour-on containing 1% Amitraz and 1% Cypermethrin, despite apparent in vitro resistance.

Pain and attention: attentional disruption or distraction?

UNLABELLED: The effect of pain processing on attention capacity during visual search was examined in 2 experiments. In the first experiment, we investigated whether pain draws on the same limited resources as attentional task performance. It was hypothesized that pain would negatively affect task performance under different load manipulations. Low and high load conditions of a visual search task were presented in a mixed design combined with a painfully cold or neutral cold pressor test. Performance was not affected by pain. In experiment 2, low and high load conditions were separated in different blocks to study whether pain perception was affected when task load could be anticipated. Again, pain did not significantly affect task performance. In contrast, subjective pain intensity scores were significantly lower after performing the high load compared with the low load condition. Simultaneous recordings of event-related potentials indicated an increased negativity during the pain compared with the control condition. Also, in the early (350 to 450 msec) interval of event-related potentials, an increase in negativity was found for the high load compared with the low load condition. Topographic distributions suggested that pain and task load are mediated by qualitatively different resources. PERSPECTIVE: Our findings indicate that highly demanding attentional task performance and pain processing interfere as a result of difficulties in allocating attention. The clinical relevance of this finding is that performing a highly demanding task might distract attention from pain.

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against myiasis causing parasites on ruminants.

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of efficacy of ectoparasiticides against the myiasis causing parasites of ruminants. These guidelines specifically focus on larvicidal efficacy against myiasis causing flies. Information is provided on the selection of animals, dose determination and dose confirmation studies, field studies, record keeping and result interpretation. These guidelines advocate the use of pen facilities for dose determination and dose confirmation studies for defining therapeutic and persistent efficacy. These guidelines are also intended to assist investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the world-wide adoption of standard procedures.

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against biting and nuisance flies on ruminants.

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of the efficacy of ectoparasiticides (excluding repellents) against the biting and nuisance dipteran flies of ruminants. Information is provided on the selection of animals, dose determination and dose confirmation studies, field studies, record keeping and result interpretation. These guidelines advocate the use of pen facilities for dose determination and dose confirmation studies. These guidelines also are intended to assist investigators on how to conduct specific studies, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the worldwide adoption of standard procedures.