Echinococcus multilocularis in foxes and raccoon dogs: an increasing concern for Baltic countries

BACKGROUND

In Europe, the life-cycle of Echinococcus multilocularis is predominantly sylvatic, involving red foxes (Vulpes vulpes) as the main definitive hosts and rodents such as muskrats and arvicolids as intermediate hosts. The parasite is the etiological agent of human alveolar echinococcosis, a malignant zoonotic disease caused by the accidental ingestion of eggs shed by definitive hosts in their faeces. The aims of this study were to investigate the prevalence of E. multilocularis in red foxes and raccoon dogs (Nyctereutes procyonoides) and to study the environmental factors favouring the perpetuation of the parasite in Latvia.

METHODS

A total of 538 red foxes and 407 raccoon dogs were collected across Latvia from 2010 to 2015. The sedimentation and counting technique was used for collecting E. multilocularis adult worms from fox and raccoon dog intestines. The morphological identification of the parasite was confirmed by molecular analysis.

RESULTS

The prevalence of E. multilocularis was significantly higher in foxes (17.1%; intensity of infection 1-7,050 worms) (P < 0.001) than in raccoon dogs (8.1%; intensity of infection 5-815 worms). In foxes, a significant positive correlation (r (10) = 0.7952, P = 0.001) was found between parasite prevalence and the intensity of infection. A positive relationship (R s = 0.900, n = 5, P = 0.037) between parasite prevalence and precipitation was also observed. In raccoon dogs, a significant negative relationship (F (1,8) = 9.412, P = 0.015) between animal density and parasite prevalence, and a significant positive relationship (F (1,8) = 7.869, P = 0.023) between parasite prevalence and agricultural land cover, were detected.

CONCLUSIONS

The results of this study confirm the red fox as the most important definitive host of E. multilocularis and, consequently, as the main target for control programmes in the Baltic countries. Raccoon dogs seem to play a secondary role in the life-cycle of E. multilocularis within the investigated European region.

Functional symptoms in neurology: questions and answers

Between 10 and 30% of patients seen by neurologists have symptoms for which there is no current pathophysiological explanation. The objective of this review is to answer questions many neurologists have about disorders characterised by unexplained symptoms (functional disorders) by conducting a multidisciplinary review based on published reports and clinical experience. Current concepts explain functional symptoms as resulting from auto-suggestion, innate coping styles, disorders of volition or attention. Predisposing, precipitating, and perpetuating aetiological factors can be identified and contribute to a therapeutic formulation. The sympathetic communication of the diagnosis by the neurologist is important and all patients should be screened for psychiatric or psychological symptoms because up to two thirds have symptomatic psychiatric comorbidity. Treatment programmes are likely to be most successful if there is close collaboration between neurologists, (liaison) psychiatrists, psychologists, and general practitioners. Long term, symptoms persist in over 50% of patients and many patients remain dependent on financial help from the government. Neurologists can acquire the skills needed to engage patients in psychological treatment but would benefit from closer working relationships with liaison psychiatry or psychology.

Enhanced dynamic wedge and independent monitor unit verification

Some serious radiation accidents have occurred around the world during the delivery of radiotherapy treatment. The regrettable incident in Panama clearly indicated the need for independent monitor unit (MU) verification. Indeed the International Atomic Energy Agency (IAEA), after investigating the incident, made specific recommendations for radiotherapy centres which included an independent monitor unit check for all treatments. Independent monitor unit verification is practiced in many radiotherapy centres in developed countries around the world. It is mandatory in USA but not yet in Australia. This paper describes development of an independent MU program, concentrating on the implementation of the Enhanced Dynamic Wedge (EDW) component. The difficult case of non centre of field (COF) calculation points under the EDW was studied in some detail. Results of a survey of Australasian centres regarding the use of independent MU check systems is also presented. The system was developed with reference to MU calculations made by Pinnacle 3D Radiotherapy Treatment Planning (RTP) system (ADAC - Philips) for 4MV, 6MV and 18MV X-ray beams used at the Newcastle Mater Misericordiae Hospital (NMMH) in the clinical environment. A small systematic error was detected in the equation used for the EDW calculations. Results indicate that COF equations may be used in the non COF situation with similar accuracy to that achieved with profile corrected methods. Further collaborative work with other centres is planned to extend these findings.

Evaluation of P-type semiconductor diodes for in-vivo dosimetry in a 6MV x-ray beam

The importance of dose verification in radiotherapy has long been recognised. Semiconductor diodes used for in-vivo dosimetry are well suited for this purpose. It was the aim of the present study to investigate the performance of a commercially available set of diodes (Rainbow diodes by Nuclear Associates) which had been in use for two years in our department. The reading of the diodes proved to be reproducible within +/- 0.5% and recalibration was necessary approximately every month. While no marked influence of field size or beam modifiers was found, SSD proved to be a significant factor influencing diode response. Using various radiation qualities in air and phantom experiments, it could be shown that dose rate was not the contributing factor to the SSD dependence of the diode reading, as has been reported by some authors. The results reinforce the need to thoroughly assess diode response prior to clinical use. Using a correction for SSD this work has resulted in the implementation of an accurate and reliable system for diode entrance dose measurements in our 6MV x-ray beams, allowing an action level of +/- 4% to be set in patient measurements.

Evaluation of rectal shielding in a Henschke system applicator

PURPOSE

To assess the effectiveness of avoid shielding in the Henschke intracavitary gynaecologic 3-channel applicator.

MATERIAL AND METHODS

An acrylic phantom was used with our locally modified 3-channel Henschke applicator so that standard treatments with caesium-137 sources could be simulated. Thermoluminescent dosimeters were used to measure point A and rectal doses with and without ovoid shielding to assess the benefits of this shielding. Unshielded measurements were also compared to our planning computer calculations to assess its accuracy. The thermoluminescent dosimeters were calibrated against a caesium teletherapy unit. An estimate of shielding effect produced by the ovoid shielding when using iridium-192 wire was also determined.

RESULTS

Doses received at points in the plane containing the rectal point as defined by the ICRU in its report 38 [4] show a reduction ranging from 5% to 15% over the area measured due to the ovoid shielding. As expected this benefit is more pronounced when using iridium-192 sources. Given the steep dose gradients, good agreement is found between computed and measured values of point A doses.

CONCLUSION

While ovoid shielding will never provide a large reduction in rectal dose using caesium-137 sources, our results indicate that it can be a worthwhile option when using the Henschke applicator.

The pharmacology of excitatory transmission in the rat olfactory cortex slice

The pharmacology of excitatory transmission in slices of olfactory cortex of the rat, perfused with solution containing picrotoxin, has been studied by assessing the effects of cis-2,3-piperidine dicarboxylate, a nonselective antagonist of excitatory amino acid receptors, 2-amino-5-phosphonopentanoate, a selective antagonist of N-methyl-D-aspartate (NMDA) receptors and 2-amino-4-phosphonobutyrate (APB) and baclofen, which act at APB and GABAB sites, respectively, on evoked surface field potentials. Monosynaptic excitatory transmission was monitored by measuring the amplitude of the N'a'-wave, evoked on stimulation of the lateral olfactory tract, whilst di-/polysynaptic excitatory transmission was evaluated by calculating the areas of the potentials evoked on direct stimulation of the superficial and deep-lying association fibre systems. On the basis of the effects of the drugs in this and earlier studies, it is concluded that: (i) transmission at the lateral olfactory tract-pyramidal cell synapse is mediated by kainate/quisqualate but not NMDA receptors and is regulated by inhibitory APB receptors, located on the tract terminals; (ii) NMDA receptors are involved in mediating excitatory transmission at the synapses of superficial association fibres with the proximal apical dendrites of pyramidal cells with inhibitory APB receptors playing a regulatory role; (iii) transmission at synapses of association fibres with basal dendrites of pyramidal cells, is mediated in part by NMDA receptors with (presynaptic?) GABAB receptors exerting a strong inhibitory influence. These proposed roles of NMDA receptors have been confirmed in experiments in which the effects of magnesium ions on field potentials evoked in slices perfused in magnesium-free solution were monitored.