Host Specialization and Dispersal in Avian Haemosporidians

In order to be able to understand the ecological and evolutionary processes involved in the emergence of infectious diseases, one needs to comprehend how parasites arrive at new geographical areas and how they manage to maintain viable populations and even expand their ranges. We discuss host specificity in avian haemosporidians and how encounter and compatibility filters affect the dispersal of avian haemosporidians, and how these filters affect avian haemosporidian assemblages at different spatial and evolutionary scales. There are at least three important barriers to the dispersal of avian haemosporidians: (i) geographic barriers, (ii) environmental barriers, and (iii) interspecies barriers. In this chapter, we discuss the factors involved in these barriers and their effects on the structure of avian haemosporidian assemblages. Host specificity plays an important role in parasite dispersal, and in the case of avian haemosporidians that are vector-borne parasites, it needs to be evaluated both at the vector and bird host levels. Understanding the effects of these factors on host–vector–parasite dynamics is important to unravel the dispersal and diversification mechanisms of avian haemosporidians. We end this chapter reviewing host specialization in avian haemosporidians of tropical regions, discussing the mechanisms involved in the dispersal and specialization of these parasites and point out important research gaps that need attention

5-Fluorouracil increases the number and complexity of premature complexes in the heart: A prospective study using ambulatory ECG monitoring

The cardiac toxicity of LV5FU2 (de Gramont) regimen which is a widely used chemotherapy regimen in gastrointestinal system cancers is not well defined. We aimed to evaluate the impact of this regimen on cardiac rhythm. Two Holter ECG recordings were obtained in all patients with gastrointestinal system cancers treated with LV5FU2 regimen as first-line chemotherapy (one before and the second during the first 24 h of chemotherapy). Records were reviewed for the heart rate, rhythm, atrial premature complexes (APC), ventricular premature complexes (VPC), grades according to Lown-Wolf grading system and ST segment changes. Holter ECG recordings were evaluated in 27 patients. In the baseline evaluation, neither clinical symptom nor ST segment changes were observed. During the treatment period, chest pain was observed in two patients without any cardiac enzyme and ST segment changes. Moreover, a decrease in mean heart rate, and an increase in the number and complexity of premature complexes secondary to treatment were observed. The mean heart rate, APC per hour and VPC per hour (±SD) before vs. during treatment were, respectively, 93.1 ± 16.4 vs. 81.6 ± 12.7 (p = 0.001), 18.9 ± 54.0 vs. 45.3 ± 53.8 vs. (p = 0.049) and 12.7 ± 29.6 vs. 38.1 ± 42.1 (p = 0.002). LV5FU2 regimen leads to a decrease in mean heart rate and a significant increase in APC and VPC which may lead to serious arrhythmias. These effects must be better understood for a safer administration of this useful and widely used drug regimen. © 2007 The Authors