The tropical fowl mite, Ornithonyssus bursa (Acari: Macronyssidae): environmental and host factors associated with its occurrence in Argentine passerine communities.

The tropical fowl mite, Ornithonyssus bursa, is a common avian parasite found on diverse bird species worldwide. In the Neotropical region, O. bursa is present in wild birds, but it may also infect poultry and bite humans. Little is known about the ecology and epidemiology of this parasite. We conducted a thorough longitudinal study in passerine assemblages from central Argentina, gathering data from six reproductive seasons, with the aim of identifying factors that have a role in driving the occurrence and distribution of O. bursa in its natural hosts. We focused on the brood and microhabitat levels, accounting for potential confounders of higher levels. The results hereby presented contribute to our knowledge on the eco-epidemiology of O. bursa in natural hosts of the Neotropical region. Among the many variables assessed, nest material and host species appeared to be the most important correlates of O. bursa prevalence. Nonetheless, supplementary analyses showed that host species is a stronger predictor than nest material. Moreover, mite burden (parasite intensity) was found to depend on host species, but not on nest material. The association with species depended on nestling age, suggesting that resistance builds up as the nestling develop, but at a different pace depending on the bird species. Brood size was inversely correlated with intensity of parasitism, suggesting a dilution of the parasite burden on each nestling.

Dynamics of Exposure to Rickettsia parkeri in Cattle in the Paraná River Delta, Argentina.

Several cases of human rickettsiosis caused by Rickettsia parkeri were recently documented in the Paraná River delta of Argentina, where the tick vector is Amblyomma triste Koch. As cattle suffer recurrent A. triste infestations, they are at risk of becoming infected with R. parkeri Herein we investigated the dynamics of R. parkeri and its A. triste vector in a herd of beef cattle. Cattle were followed for 18 mo and samples were analyzed for the presence of antibodies against four Rickettsia species (R. parkeri, Rickettsia bellii, Rickettsia amblyommii, and Rickettsia felis) and also for the presence of rickettsial DNA. Additionally, cattle were examined for attached ticks and questing adult ticks were collected. All ticks were analyzed for the presence of rickettsial DNA. No evidence of rickettsemia was found in any cow, but the high R. parkeri infection rate documented in A. triste both questing in the study area (13.9%) and feeding on cattle (19.8%) and the identification of antibodies against R. parkeri antigen in 90% of cattle are evidence that infection is taking place. Altogether, our data suggest that A. triste ticks are capable of naturally exposing cattle to R. parkeri However, the progress of R. parkeri infection and its impact on bovine health and production remain to be established.

First record of the avian ectoparasite Philornis downsi Dodge & Aitken, 1968 (Diptera: Muscidae) in Argentina.

Species of Philornis Meinert, 1890 (Diptera, Muscidae) are Neotropical dipterans that include species with parasitic larvae which feed on nestling birds. To date, all Philornis species that have been recorded from Argentina have parasitic subcutaneous larvae. Here, for the first time for Argentina, we report the finding of Philornis downsi Dodge & Aitken, 1968, a fly with a nest-dwelling, semi-haematophagous larva. This record, from the humid Chaco ecoregion of Argentina in the nest of a saffron finch Sicalis flaveola pelzelni Sclater, substantially extends the known distribution of this species. We also report the consensus sequences of the internal transcribed spacer 1 (ITS1) and ITS2 regions of three of the specimens for future reference and comparison. Further investigation is needed to determine whether Argentina is part of the historical range of P. downsi or, alternatively, represents a recent expansion of its range, perhaps due to climatic changes or other factors of global environmental variation.

Barrett's esophagus: combined treatment using argon plasma coagulation and laparoscopic antireflux surgery.

The treatment of Barrett's esophagus is still controversial. Actually, the only method to prevent the development to cancer is endoscopic surveillance, which ensures good results in terms of long-term survival. An ideal treatment capable of destroying columnar metaplasia, followed by squamous epithelium regeneration could potentially result in a decrease of the incidence of adenocarcinoma. Recently most ablative techniques were used, such as photodynamic therapy, ablation therapy with Nd-YAG laser or argon plasma coagulation and endoscopic mucosal resection. We started a prospective study in January 1998, enrolling 94 patients affected by Barrett's esophagus and candidates for antireflux repair in order to assess the effectiveness and the results of endoscopic coagulation with argon plasma combined with surgery in the treatment of uncomplicated Barrett's esophagus. All patients underwent endoscopic treatment with argon plasma; we observed complete response in 68 patients (72.34%), 27 of them (39.7%) underwent antireflux surgery and the other 41 continued medical therapy. Post-operatively 19 patients (70%) underwent regular surveillance endoscopies and in two cases metaplasia recurred. The final objective of these combined treatments should be the complete eradication of metaplastic mucosa. Our experience was that argon plasma coagulation combined with antireflux surgery or proton pump inhibitor therapy gave satisfactory results, even if follow-up is too short to evaluate the potential evolution of metaplasia to cancer. For this reason, we recommend that this technique should be done only in specialized centres and that these patients continue their endoscopic surveillance program.

Does previous endoscopic treatment affect the outcome of laparoscopic Heller myotomy?

STUDY AIM: Aim of this study was to assess symptomatic and objective outcome in patients undergoing laparoscopic Heller myotomy after unsuccessful endoscopic treatment, compared to patients having primary surgery. PATIENTS AND METHOD: Between November 1992 and December 1998, 92 patients with esophageal achalasia underwent laparoscopic Heller myotomy and Dor fundoplication. Intraoperative endoscopy was routinely performed. Sixty patients had primary surgery (PS); 32 patients had surgery after unsuccessful pneumatic dilatation (PD) (n = 22), or botulinum toxin (Botox) injection (n = 10). RESULTS: The mean operative time and the incidence of postoperative dysphagia were similar in the two groups. The incidence of intraoperative mucosal tears was 5% in the PS group and 12.5% in the PD/Botox group (P = NS). Mucosal tears occurred more frequently during the first 30 operations (17% vs 3.2%, P < 0.05). Median follow-up was 28 months (range 4-76). An abnormal esophageal acid exposure was documented in 2 patients in the PS group (7.7%), and in two patients in the PD/Botox group (13.3%) (P = NS). Lower esophageal sphincter pressure significantly decreased in both groups (P < 0.01). The mean percentage of radionuclide residual activity in the esophagus at 1 and 10 minutes significantly decreased in both groups (P < 0.01). CONCLUSION: There is only a trend, although not statistically significant, towards an increased risk of complications and adverse effects in patients previously treated by PD and/or Botox. The higher incidence of mucosal tears during the first 30 operations suggests the effect of the learning curve.

Previous endoscopic treatment does not affect complication rate and outcome of laparoscopic Heller myotomy and anterior fundoplication for oesophageal achalasia.

BACKGROUND: Anedoctal reports suggest a detrimental effect of pneumatic dilation and botulinum toxin injection in patients who are potential candidates for Heller myotomy. AIMS: To assess symptomatic and objective outcome in patients undergoing Heller myotomy as a primary procedure or after failed endoscopic treatment. PATIENTS: Between November 1992 and December 1998, 92 patients with oesophageal achalasia were treated. Sixty patients had primary surgery; 32 patients had surgery after unsuccessful pneumatic dilation (n = 22), or botulinum toxin injection (n = 10). METHODS: Laparoscopic Heller myotomy plus Dor fundoplication with routine intraoperative endoscopy. Operative records, symptoms, and results of radiological, manometric and scintigraphic assessment in the two groups of patients were compared. RESULTS: The mean operative time, the rate of intraoperative mucosal tears and the incidence of postoperative dysphagia were similar in the two groups. Mucosal tears occurred more frequently during the first 30 operations (p < 0.05). Median follow-up was 28 months (range 4-76). An abnormal oesophageal acid exposure was documented in 2 patients in the primary surgery group (7.7%), and in 2 patients in the pneumatic dilation/botulinum toxin group (13.3%) (p = ns). Lower oesophageal sphincter pressure significantly decreased in both groups (p < 0.01). The mean percentage of radionuclide residual activity in the oesophagus at 1 and 10 minutes significantly decreased in both groups (p < 0.01). CONCLUSIONS: There was only a trend, although not statistically significant, towards an increased risk of complications and adverse effects in patients previously treated by pneumatic dilation or botulinum toxin. The higher incidence of mucosal tears during the first 30 operations suggests the effect of the learning curve.

Minimally invasive surgery for Zenker diverticulum: analysis of results in 95 consecutive patients.

OBJECTIVE: To assess the effectiveness of transoral stapled diverticulum esophagostomy in relieving symptoms and decreasing outflow resistance at the pharyngoesophageal junction in patients with Zenker diverticulum. DESIGN: Cohort study. From April 1, 1992, until May 31, 1996, the operation was attempted in 95 patients. The median follow-up was 23 months (range, 13-48 months). SETTING: Tertiary care university hospital. PATIENTS: There were 74 men and 21 women, with a median age of 64 years (age range, 37-92 years). All complained of dysphagia and pharyngo-oral regurgitation, and 18 (20%) suffered from recurrent aspiration pneumonia. The median size of the pouch measured by flexible endoscopy was 4 cm (range, 2.5-8 cm). INTERVENTION: The septum between the diverticulum and the esophageal lumen was divided under general anesthesia using a linear endostapler introduced through a Weerda endoscope. In most patients, 2 applications of the endostapler with a modified anvil were used. Operative time averaged 23 minutes. MAIN OUTCOME MEASURES: Morbidity, symptom score, patient's satisfaction, videofluorographic barium transit, hypopharyngeal intrabolus pressure, upper esophageal clearance of radioisotope. RESULTS: A switch to open surgery was required in 3 patients (3.1%), due to difficult exposure of the common wall in 2 cases and a mucosal tear in the other. No postoperative morbidity or mortality was recorded. Oral feeding was started the following day and the median hospital stay was 3 days (range, 2-8 days). Five patients complained of persistent symptoms; 3 of them underwent another endosurgical operation, 1 underwent laser treatment by means of flexible endoscopy, and 1 eventually required open surgery. All patients are asymptomatic at the latest follow-up visit. Postoperative radiologic studies showed free flow of barium in all patients. Manometry showed a significant reduction of hypopharyngeal intrabolus pressure over preoperative values (P=.003). Radionuclide studies showed a significant reduction of upper esophageal residual activity at 1 minute compared with preoperative values (P=.006). CONCLUSIONS: Endosurgical approach to hypopharyngeal diverticula larger than 2 cm is safe and effective. Symptom relief, elimination of the pouch, and decreased outflow resistance at the pharyngoesophageal junction can be obtained without morbidity and with a short hospital stay.

Biochemical markers of upper esophageal sphincter compliance in patients with Zenker's diverticulum.

The aim of this study was to investigate the biochemical basis of biomechanical and morphological alterations of upper esophageal sphincter, which have been reported in patients with Zenker's diverticulum. 4-L-Hydroxyproline (4-Hyp) (collagen), isodesmosine (Ides), and desmosine (Des) (elastin) contents were measured in samples of cricopharyngeal muscle (CPM) and muscularis propria of the esophagus below the CPM. The specimens were collected from seven patients operated for Zenker's diverticulum and eight cadavers, without esophageal and connective tissue disease, 4-Hyp was assayed colorimetrically, Ides and Des by high-performance liquid chromatography. Mean (+/-SEM) values were compared by Mann-Whitney U test. In patients, collagen content was significantly increased, both in CPM and in the muscularis propria of the esophagus below the CPM (P < 0.05). In CPM, Ides to Des and collagen to elastin ratios were significantly higher in patients than in controls (P < 0.05). Both the CPM and the upper muscular cuff of the esophagus appear to be involved in the pathogenesis of Zenker's diverticulum. This finding supports the extension of the myotomy to the muscularis propria of the esophagus below the CPM. The alterated Ides to Des ratio suggests a primary disease of CPM as a cause of Zenker's diverticulum.