Serum amyloid A and plasma fibrinogen concentrations in horses following emergency exploratory celiotomy.

BACKGROUND: Acute-phase proteins may help assess the nature and severity of lesions and outcome in horses undergoing colic surgery. OBJECTIVES: To compare serum amyloid A and plasma fibrinogen concentrations ([SAA] and [fibrinogen]) in the immediate post-operative period after exploratory celiotomy and determine their value in assessment of post-operative complications and survival to discharge. STUDY DESIGN: Observational study. METHODS: This study included horses over 1 year of age undergoing exploratory celiotomy. Surgical procedures, lesions, post-operative care, complications and survival to discharge were recorded. [SAA] and [fibrinogen] were measured prior to surgery and 5 days post-operatively. Statistical analyses included Yate's Chi-square test, linear mixed effects model, Mann-Whitney U test and logistic regression. RESULTS: Of 300 horses, 52.0% developed post-operative complications and 83.7% survived to discharge, with significantly reduced chance of survival in horses that developed post-operative complications (P<0.01). Median [SAA] at days 1, 2, 3, 4 and 5 and median [fibrinogen] at days 3, 4 and 5 were significantly different between horses that did and did not develop post-operative complications (P<0.05). Median [SAA] at days 1, 4 and 5 were significantly different between horses that did and did not survive to discharge (P<0.05). Logistic regression revealed post-operative complications to be associated with strangulating lesions (OR 2.35, 95% confidence interval [CI] 1.41-3.91, P≤0.001) and higher [fibrinogen] at admission (OR 1.21, 95% CI 1.00-1.45, P<0.05), and survival to discharge to be associated with lower [SAA] at 5 days post-operatively (OR 0.965, 95% CI 0.94-0.99, P = 0.002). MAIN LIMITATIONS: A large variety of lesions and complications prevented detailed analysis of associations between inflammatory markers, lesions and complications. CONCLUSIONS: Horses that develop post-operative complications have acute-phase responses of greater magnitudes and durations compared with those that do not develop complications. This is also seen in horses that do not survive to discharge. Measuring [SAA] daily and [fibrinogen] at admission, may help predict the development of post-operative complications.

Magic angle effect on low field magnetic resonance images in the superficial digital flexor tendon in the equine proximal pastern region.

Recognition of artefacts is an essential component of the accurate interpretation of diagnostic images. This study aimed to investigate the presence of magic angle effect in the superficial digital flexor tendon (SDFT) in the equine proximal pastern region. The proximal pastern of four cadaver limbs was imaged using a 0.27 Tesla magnet with high-resolution sequences that are commonly utilised in clinical equine practice. The limbs were imaged in a neutral position and positions that simulated the horse 'leaning in', 'leaning out' and having internal and external rotation of the distal limb. Signal intensity changes in the SDFT were described and compared. The simulated 'leaning in' and external rotation positions resulted in increased signal intensity in the axial and middle thirds of the lateral half of the SDFT on sequences with short echo times. The simulated 'leaning out' and internal rotation positions resulted in increased signal intensity in the axial and middle thirds of the medial half of the SDFT on sequences with short echo times. These signal intensity changes did not occur or were only mild and inconsistent on T2 fast spin echo sequences with longer echo times. The increases in signal intensity in the SDFT are consistent with a position-induced magic angle artefact that has been noted in clinical cases. Attention to positioning of the equine distal limb is essential during clinical imaging; radiologists should be aware of position-induced artefacts to ensure accurate image interpretation.

Technical innovation changes standard radiographic protocols in veterinary medicine: is it necessary to obtain two dorsoproximal-palmarodistal oblique views of the equine foot when using computerised radiography systems?

Since the 1950s, veterinary practitioners have included two separate dorsoproximal-palmarodistal oblique (DPr-PaDiO) radiographs as part of a standard series of the equine foot. One image is obtained to visualise the distal phalanx and the other to visualise the navicular bone. However, rapid development of computed radiography and digital radiography and their post-processing capabilities could mean that this practice is no longer required. The aim of this study was to determine differences in perceived image quality between DPr-PaDiO radiographs that were acquired with a computerised radiography system with exposures, centring and collimation recommended for the navicular bone versus images acquired for the distal phalanx but were subsequently manipulated post-acquisition to highlight the navicular bone. Thirty images were presented to four clinicians for quality assessment and graded using a 1-3 scale (1=textbook quality, 2=diagnostic quality, 3=non-diagnostic image). No significant difference in diagnostic quality was found between the original navicular bone images and the manipulated distal phalanx images. This finding suggests that a single DPr-PaDiO image of the distal phalanx is sufficient for an equine foot radiographic series, with appropriate post-processing and manipulation. This change in protocol will result in reduced radiographic study time and decreased patient/personnel radiation exposure.

Idiopathic Fibrosis of the Tunica Muscularis of the Large Intestine in Five Horses with Colic.

Histological evidence of fibrosis affecting the outer layer of the large intestinal tunica muscularis was identified in five of 32 horses affected by colic. In three cases, foci of pale eosinophilia and vacuolation of myocytes were observed. These findings are suggestive of a degenerative and fibrotic abnormality in the outer layer of the tunica muscularis of the large intestinal smooth muscle of some horses with colic.

Do low field magnetic resonance imaging abnormalities correlate with macroscopical and histological changes within the equine deep digital flexor tendon?

Correlating magnetic resonance (MR) imaging and histopathological findings is essential to validate low field MR imaging in lame horses. This study aimed to compare signal changes in the deep digital flexor tendon (DDFT) of the distal limb on low field MR imaging with macroscopical and histological findings. Cadaver limbs from lame horses with DDFT lesions were selected. The DDFT MR imaging findings and histopathological results were graded, and macroscopical abnormalities were recorded. There was a strong correlation between MR imaging and histopathology grades (rs = 0.76, p < 0.001) in the foot. There was moderate agreement (Kappa statistic 0.52) between the MR and histopathology grades; agreement was superior further proximal in the foot. The presence and severity of pathology in the DDFT are well represented by the presence and severity of MR imaging signal changes. The study supports the use of low field MR imaging for diagnosis of equine distal limb DDFT lesions.

Effect of N-butylscopolammonium bromide on equine ileal smooth muscle activity in an ex vivo model.

REASONS FOR PERFORMING STUDY: N-butylscopolammonium bromide (NBB) is an anticholinergic agent used to treat spasmodic colic in horses. Intestinal smooth muscle spasm also occurs in horses with intraluminal intestinal obstructions, such as ileal impactions. The antispasmodic effects of NBB may be useful in managing ileal impactions, but the effects of NBB on equine ileal smooth muscle are unknown. OBJECTIVES: To investigate the effects of NBB on spontaneous and induced contraction of the equine ileum in an ex vivo model. STUDY DESIGN: Ex vivo biomechanical study assessing contractile properties in isolate equine ileal smooth muscle with and without exposure to NBB. METHODS: Ileal tissue was collected from 6 healthy horses after euthanasia, and isolated circular and longitudinal smooth muscle strips were connected to isometric force transducers in organ baths. After equilibration, the effect of NBB (1 nmol/l to 100 µmol/l) on spontaneous and carbachol-induced contraction was determined and compared with responses in control tissue. RESULTS: At ≥30 µmol/l, NBB inhibited spontaneous contractions in all muscle strips that exhibited spontaneous activity. N-butylscopolammonium bromide pre-treatment inhibited carbachol-induced contraction in circular (NBB-treated half maximal effective concentration [EC50] 0.530 × 10(-8) mol/l vs. control EC50 41.57 × 10(-8) mol/l) and longitudinal muscle strips (NBB-treated EC50 0.243 × 10(-8) mol/l vs. control EC50 90.84 × 10(-8) mol/l). Abolition of carbachol-induced contraction with NBB was observed at lower concentrations in circular than longitudinal muscle strips. Pretreatment with NBB significantly inhibited carbachol-induced contractions; NBB-treated tissue required greater carbachol concentrations to produce sustained contractions than control muscle strips. Histamine-evoked contraction was not affected by NBB. CONCLUSIONS: N-butylscopolammonium bromide inhibits spontaneous and cholinergically mediated contraction in equine ileal smooth muscle strips ex vivo. Thus, NBB might reduce intestinal spasm in equine ileal impactions and could be useful for medical management of these cases, although further study is needed to confirm these effects in vivo.

Serum cortisol concentrations in horses with colic.

Few studies have evaluated cortisol concentrations in horses with colic. In humans with septic shock, high cortisol levels are associated with an increased risk of death. The objectives of this study were to compare the serum total cortisol concentrations (STCCs) in horses with colic to those without colic, and to assess whether the STCC relates to the pathological nature or outcome of the disease. STCCs were determined at presentation in horses with colic and in systemically healthy 'control' horses. Horses with colic were grouped based on clinical and clinico-pathological parameters at admission, treatment, lesion type and location, and outcome. Univariable and multivariable logistic regression were performed using two different outcome measures: (a) whether the horse had colic or not (yes vs. no), and (b) horse STCC (≥200 nmol/L vs. <200 nmol/L). Horses were more likely to have colic if they presented with high STCCs (≥200 nmol/L compared with <200 nmol/L). Horses with colic and with STCCs ≥200nmol/L were more likely to have moderate or severe colic signs (compared with mild colic) and heart rates >45 beats per min (compared with ≤45 beats per min). It was concluded that colic in horses is associated with elevated STCCs, and increased STCC in horses with colic appears to relate to the severity of the disease. STCCs may provide additional decision-making and prognostic information in horses with colic but further studies are required to avoid misinterpretations associated with the wide variation in STCCs.

Child rights and Child and Adolescent Mental Health Services (CAMHS) in Ireland.

This paper explores children's rights in the child and adolescent mental health arena in Ireland. It begins by outlining the legal and policy contexts of both children's services and mental health policy and practice. It specifically focuses on the notion of participation as a key factor in addressing rights-based approaches in the provision of services. The article explores current practice in Child and Adolescent Mental Health Services, highlights some of the disparities in services, which result in questions about human rights. Mainly reflective in its approach, it does, however, provide data from a small scale qualitative study carried out in relation to young people diagnosed with ADHD and their perceptions of psychopharmacological approach. The issue of consent is explored as an example of how current practice approaches fall short of a rights-based framework. It concludes with recommendations for changes incorporating a more participatory and collaborative approach.

Concealed pregnancy: prevalence, perinatal measures and socio-demographics.

A target group of women who concealed their pregnancy (n = 43) was compared to an aged-matched control group (n = 30) that experienced a crisis pregnancy. Comparisons were also made with a larger dataset (n = 6363) of births in University Hospital Galway (UHG) (normative group). Data was analysed using the Chi-square test and the Kolmogorov-Smirnoff two-sample test. The number of women from the target group that were from a rural background was 28 (65%), compared to 10 (33%) from the control group. The number of women from the target group that feared a negative parental reaction to the pregnancy was 34 (79%), compared to 12 (40%) from the control group. The birth weight in the target group was 4009 lower than the normative birth weight. The average age of women who concealed was 8 years lower than the normative age. The prevalence of concealed pregnancy in UHG was one in every 148 births.

Poor seroprotection but allosensitization after adjuvanted pandemic influenza H1N1 vaccine in kidney transplant recipients.

BACKGROUND: Seasonal and pandemic influenza virus infections in renal transplant patients are associated with poor outcomes. During the pandemic of 2009-2010, the AS03-adjuvanted monovalent H1N1 influenza vaccine was recommended for transplant recipients, although its immunogenicity in this population was unknown. We sought to determine the safety and immunogenicity of an adjuvant-containing vaccine against pandemic influenza A H1N1 2009 (pH1N1) administered to kidney transplant recipients. METHODS: We prospectively enrolled 124 adult kidney transplant recipients in the fall of 2009 at two transplant centers. Cohort 1 (n = 42) was assessed before and after pH1N1 immunization, while Cohort 2 (n = 82) was only assessed post immunization. Humoral response was measured by the hemagglutination inhibition assay. Vaccine safety was assessed by adverse event reporting, graft function, and human leukocyte antigen (HLA) alloantibody measurements. RESULTS: Cohort 1 had a low rate of baseline seroprotection to pH1N1 (7%) and a low rate of seroprotection after immunization (31%). No patient <6 months post transplant (n = 5) achieved seroprotection. Seroprotection rate was greater in patients receiving double as compared with triple immunosuppression (80% vs. 24%, P = 0.01). In Cohort 2, post-immunization seroprotection was 35%. In both cohorts, no confirmed cases of pH1N1 infection occurred. No difference was seen in estimated glomerular filtration rate before (54.3 mL/min/1.73 m(2) ) and after (53.8 mL/min/1.73 m(2) ) immunization, and no acute rejections had occurred after immunization at last follow-up. In Cohort 1, 11.9% of patients developed new anti-HLA antibodies. CONCLUSION: An adjuvant-containing vaccine to pH1N1 provided poor seroprotection in renal transplant recipients. Receiving triple immunosuppression was associated with a poor seroresponse. Vaccination appeared safe, but some patients developed new anti-HLA antibodies post vaccination. Alternative strategies to improve vaccine responses are necessary.

Spatial and temporal patterns in antimicrobial resistance of Salmonella Typhimurium in cattle in England and Wales.

Salmonella is the second most commonly reported human foodborne pathogen in England and Wales, and antimicrobial-resistant strains of Salmonella are an increasing problem in both human and veterinary medicine. In this work we used a generalized linear spatial model to estimate the spatial and temporal patterns of antimicrobial resistance in Salmonella typhimurium in England and Wales. Of the antimicrobials considered we found a common peak in the probability that an S. typhimurium incident will show resistance to a given antimicrobial in late spring and in mid to late autumn; however, for one of the antimicrobials (streptomycin) there was a sharp drop, over the last 18 months of the period of investigation, in the probability of resistance. We also found a higher probability of resistance in North Wales which is consistent across the antimicrobials considered. This information contributes to our understanding of the epidemiology of antimicrobial resistance in Salmonella.

The clinical and pathological features of gastric impaction in twelve horses.

REASONS FOR PERFORMING STUDY: Gastric impaction in the horse is poorly described in the veterinary literature. OBJECTIVES: To review the clinical and pathological features of gastric impaction. METHODS: The clinical details of horses presenting with colic over a 7-year period and cases in which gastric impaction was considered to determine the outcome were reviewed. Clinical and clinicopathological data were recorded. RESULTS: Twelve cases of gastric impaction were recorded (1.4% of 857 horses hospitalised for colic). Diagnosis was achieved by ultrasonographic examination, gastroscopy, exploratory celiotomy and/or post mortem examination. Five out of 12 horses were successfully treated, 5/12 were subjected to euthanasia (3 at celiotomy and 2 due to recurrence of impaction) and 2/12 died. Three out of 12 horses had spontaneous gastric rupture despite attempted treatment (one was subjected to euthanasia at celiotomy and 2 died). Post mortem examination (7 horses) revealed gross muscular thickening of the stomach wall in 6/7 horses. Histological examination revealed focal fibrosis of the stomach wall in 4/6 and focal myositis in 1/6 horses. CONCLUSIONS AND PRACTICAL SIGNIFICANCE: Gastric impaction is a rare cause of colic and affected horses can present with acute, chronic or recurrent colic in the presence or absence of other gastrointestinal disease. Spontaneous gastric rupture may occur. A proportion of affected horses have gross thickening of the muscular layers of the stomach wall.

Ex vivo comparison of three hand sewn end-to-end anastomoses in normal equine jejunum.

REASONS FOR PERFORMING STUDY: Although single layer techniques are preferred in man and small animals for small intestinal end-to-end anastomoses, double layer techniques are more popular in equine surgery. This study was undertaken to evaluate the ex vivo characteristics of 2 single layer anastomoses in comparison to the traditionally performed double layer anastomosis in equine jejunum. OBJECTIVES: To compare ex vivo: 1) construction time; 2) bursting pressure; and 3) lumen size reduction of 3 suture patterns (double layer simple continuous/Cushing pattern [2C]; single layer Lembert pattern [1L]; and single layer Cushing pattern [1C]) for end-to-end equine jejunojejunostomies. METHODS: End-to-end jejunojejunostomies were constructed using 2C (n = 7), 1L (n = 7) and 1C (n = 7) in harvested equine jejunum and construction times were recorded. Anastomosed and control segments were distended with gas until failure. Intraluminal pressure at failure and mode of failure were recorded. Lumen size reduction was calculated as a percentage decrease from control jejunum. Results were compared using an ANOVA and P<0.05 was considered significant. RESULTS: The 1C anastomoses were faster to construct than the 1L anastomoses, which were faster to construct than the 2C anastomoses. There were no differences in bursting pressures between the different anastomoses and control jejunum. All anastomoses decreased lumen size from control values but there were no differences in lumen reduction between types of anastomoses. CONCLUSIONS: Single layer anastomoses are faster to construct than double layer anastomoses, with the 1C being fastest. Single layer anastomoses are as strong and result in comparable lumen size reduction as traditional 2C anastomoses. POTENTIAL RELEVANCE: As the 1C anastomosis results in less exposed potentially adhesiogenic suture material than the 1L while providing adequate strength and similar luminal size reduction, the 1C may be better for equine small intestine anastomosis and further in vivo studies are warranted.

Surgical drainage and post operative lavage of large abdominal abscesses in six mature horses.

Six mature horses with large abdominal abscesses (defined as an abscess >15-20 cm in at least one dimension) were treated by surgical drainage and post operative lavage. The abscess was associated with previous intestinal surgery in one horse, and with Streptococcus equi spp. equi infection in the other 5. A Foley catheter was used to drain and lavage the abscess in all cases. The abscess was accessed by a ventral midline laparotomy in 5 cases and by standing flank laparoscopy in one. Two horses were subjected to euthanasia within 7 days due to persistent or recurrent colic. The other 4 horses survived. Lavage of the abscess was continued for a median time of 19 days. Antibacterial therapy was continued until the plasma fibrinogen concentration was normal (median 47 days). Follow-up information was obtained at a median of 1.8 years. All 4 horses were alive at the time of follow-up; 2 horses had suffered one or more bouts of colic that had responded to medical treatment.

The prevalence of antimicrobial-resistant Escherichia coli in sympatric wild rodents varies by season and host.

AIMS: To investigate the prevalence and temporal patterns of antimicrobial resistance in wild rodents with no apparent exposure to antimicrobials. METHODS AND RESULTS: Two sympatric populations of bank voles and wood mice were trapped and individually monitored over a 2- year period for faecal carriage of antimicrobial-resistant Escherichia coli. High prevalences of ampicillin-, chloramphenicol-, tetracycline- and trimethoprim-resistant E. coli were observed. A markedly higher prevalence of antimicrobial-resistant E. coli was found in wood mice than in bank voles, with the prevalence in both increasing over time. Superimposed on this trend was a seasonal cycle with a peak prevalence of resistant E. coli in mice in early- to mid-summer and in voles in late summer and early autumn. CONCLUSIONS: These sympatric rodent species had no obvious contact with antimicrobials, and the difference in resistance profiles between rodent species and seasons suggests that factors present in their environment are unlikely to be drivers of such resistance. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings suggest that rodents may represent a reservoir of antimicrobial-resistant bacteria, transmissible to livestock and man. Furthermore, such findings have implications for human and veterinary medicine regarding antimicrobial usage and subsequent selection of antimicrobial-resistant organisms.

Comparison of high-field and low-field magnetic resonance images of cadaver limbs of horses.

Eleven limbs taken postmortem from 10 lame horses were examined by MRI in a low-field 0.27T system designed for standing horses and a high-field 1.5T system used to examine anaesthetised horses. Nine limbs were examined in the foot/pastern region and two in the fetlock region, and the results were compared with gross pathological examinations and histological examinations of selected tissues. The appearance of normal tissues was similar between the two systems, but the anatomical arrangement of the structures was different due to differences in positioning, and a magic angle artefact was observed at different sites in some imaging sequences. Articular cartilage could be differentiated into two articular surfaces in most joints in the high-field images but could generally be separated only at the joint margins in the low-field images. Abnormalities of tendon, ligament and bone detected by gross examination were detected by both forms of MRI, but some details were clearer on the high-field images. Articular cartilage found to be normal on pathological examination was also classified as normal on MRI, but lesions in articular cartilage detected on pathological examination were identified only by high-field MRI. An abnormality was detected on MRI of all the limbs that had abnormal navicular flexor fibrocartilage on pathological examination.

Identification of performance problems in a commercial human immunodeficiency virus type 1 enzyme immunoassay by multiuser external quality control monitoring and real-time data analysis.

In June 2005, a pilot program was implemented in Canadian laboratories to monitor the performance of the Abbott human immunodeficiency virus types 1 and 2 (HIV-1/2) gO enzyme immunoassay (EIA). Two different external quality control (QC) reagents and a "real-time" software analysis program were evaluated. In November 2005, higher-than-expected calibrator rate values in these kits were first reported at the Ontario Ministry of Health (Etobicoke), followed by the Alberta Provincial Public Health Laboratory (Edmonton and Calgary) and others. These aberrations were easily and readily tracked in "real time" using the external QC reagents and the software program. These high calibrator values were confirmed in Delkenheim, Germany, by Abbott, and a manufacturing change was initiated beginning with lot 38299LU00, which was distributed to laboratories in Canada in April 2006. However, widespread reports of calibrator failure by laboratories outside Canada were made in March 2006. In April 2006, Abbott Diagnostics initiated a level III investigation to identify the root cause, which was prolonged storage, under uncontrolled storage conditions, of the raw material used in the manufacture of the matrix cells. To the best of our knowledge, this is the first example of a program in Canada for serological testing that combines a common external QC reagent and a "real-time" software program to allow laboratories to monitor kit performance. In this case, external QC monitoring helped identify and confirm performance problems in the Abbott HIV-1/2 gO EIA kit, further highlighting the benefit of implementing such a program in a national or multilaboratory setting for laboratories performing diagnostic and clinical monitoring testing.

Deep erosions of the palmar aspect of the navicular bone diagnosed by standing magnetic resonance imaging.

REASONS FOR PERFORMING STUDY: Erosion of the palmar (flexor) aspect of the navicular bone is difficult to diagnose with conventional imaging techniques. OBJECTIVES: To review the clinical, magnetic resonance (MR) and pathological features of deep erosions of the palmar aspect of the navicular bone. METHODS: Cases of deep erosions of the palmar aspect of the navicular bone, diagnosed by standing low field MR imaging, were selected. Clinical details, results of diagnostic procedures, MR features and pathological findings were reviewed. RESULTS: Deep erosions of the palmar aspect of the navicular bone were diagnosed in 16 mature horses, 6 of which were bilaterally lame. Sudden onset of lameness was recorded in 63%. Radiography prior to MR imaging showed equivocal changes in 7 horses. The MR features consisted of focal areas of intermediate or high signal intensity on T1-, T2*- and T2-weighted images and STIR images affecting the dorsal aspect of the deep digital flexor tendon, the fibrocartilage of the palmar aspect, subchondral compact bone and medulla of the navicular bone. On follow-up, 7/16 horses (44%) had been subjected to euthanasia and only one was being worked at its previous level. Erosions of the palmar aspect of the navicular bone were confirmed post mortem in 2 horses. Histologically, the lesions were characterised by localised degeneration of fibrocartilage with underlying focal osteonecrosis and fibroplasia. The adjacent deep digital flexor tendon showed fibril formation and fibrocartilaginous metaplasia. CONCLUSIONS: Deep erosions of the palmar aspect of the navicular bone are more easily diagnosed by standing low field MR imaging than by conventional radiography. The lesions involve degeneration of the palmar fibrocartilage with underlying osteonecrosis and fibroplasia affecting the subchondral compact bone and medulla, and carry a poor prognosis for return to performance. POTENTIAL RELEVANCE: Diagnosis of shallow erosive lesions of the palmar fibrocartilage may allow therapeutic intervention earlier in the disease process, thereby preventing progression to deep erosive lesions.

Evaluation of foot pain in the standing horse by magnetic resonance imaging.

The records of 41 horses with previously undiagnosed foot pain that had been examined by standing magnetic resonance imaging were reviewed and follow-up information was obtained from their owners two years after the examination. A range of soft tissue and osseous abnormalities were identified, with multiple lesions frequently occurring. Deep digital flexor tendonitis was recorded in 12 of the horses, and distension of the distal interphalangeal joint was identified in 15, but it was not always associated with lameness; in contrast, distension of the navicular bursa was always associated with lameness in the seven affected horses. Navicular bone lesions were identified in 13 of the horses, often in the absence of radiographic changes. Follow-up information was obtained for 35 of the horses, 27 of which were alive; of these, 16 had returned to their previous level of performance. Of the five horses with navicular bursal changes, four had been euthanased owing to lameness and the other had returned to work at a reduced level.

The prevalence of herpes simplex virus shedding and infection in the oral cavity of seropositive patients undergoing head and neck radiation therapy.

OBJECTIVE: Herpes viruses are characterized by their ability to establish and maintain a latent infection that can reactivate. Only 2 preliminary studies have examined herpes simplex virus (HSV) reactivation in patients receiving head and neck radiotherapy. The role of radiation therapy in the reactivation of a latent virus has not been established. The purpose of the present study was to evaluate the incidence of HSV reactivation in patients receiving radiation treatment for head and neck malignancies. METHODS: Twenty patients, 19 of whom were HSV seropositive, undergoing head and neck radiation therapy were assessed weekly before and during radiation therapy, and HSV cultures were completed during cancer treatment. RESULTS: Only 3.6% of the cultures were positive for HSV during radiation therapy. HSV was cultured in 4 men receiving a mean of 6,000 cGy to the head and neck area. Recovery from HSV was seen in patients nearing completion of radiation therapy. CONCLUSIONS: The results of this study suggest that HSV reactivation is not common during radiation therapy. Therefore, this study does not support prophylaxis of HSV in patients undergoing head and neck irradiation.