The evolution of virulence and host specialization in malaria parasites of primates

Parasite virulence, i.e. the damage done to the host, may be a by-product of the parasite's effort to maximize its fitness. Accordingly, several life-history trade-offs may explain interspecific differences in virulence, but such constraints remain little tested in an evolutionary context. In this phylogenetic study of primate malarias, I investigated the relationship between virulence and other parasite life-history traits. I used peak parasitaemia as a proxy for virulence, because it reflected parasite reproductive success and parasite-induced mortality. Peak parasitaemia was higher in specialist than in generalist species, even when confounding life-history traits were controlled. While there was a significant phylogenetic relationship between the number of competitors per host and host specialization, peak parasitaemia was unrelated to within-host competition. Therefore, the key evolutionary factor that favours virulence is host specialization, and the evolutionary success of virulent parasites, such as Plasmodium falciparum, may be better understood when the trade-off in virulence between different hosts is considered. Such phylogenetic results may help us design better protection programmes against malaria

Myiasis gastrointestinal humana por Eristalis tenax Gastrointestinal human myiasis for Eristalis tenax

Son caracterizadas las myiasis registradas en Bariloche y establecidas las condiciones probables bajo las cuales se produjeron las infestaciones. Las larvas obtenidas a partir de heces de 2 pacientes fueron identificadas como Eristalis tenax (Diptera: Syrphidae) de acuerdo a las claves de Hartley (1961) y Organización Panamericana de la Salud (1962). Estos 2 casos de myiasis gastrointestinal humana constituyen los primeros registrados en Bariloche (Patagonia, Argentina) y sus características responden a las registradas para esta especie de Díptera en otras partes del mundo. La falta de control específico en el sistema domiciliario de suministro de agua ha sido la causa más probable de la infestación. Este registro extiende la distribución de E. tenax y de las myiasis gastrointestinales humanas en América del Sur hasta los 41º 03' S.<br>Foram caracterizadas as miasis registradas em Bariloche (Patagonia, Argentina) e estabelecidas as prováveis condições sob as quais são produzidas as infestações. As larvas obtidas a partir das fezes de dois pacientes foram identificadas como Eristalis tenax (Diptera: Syrphdae). Esses dois casos de miasis gastrointestinal humana foram os primeiros registrados em Bariloche, Argentina, e suas características respondem às registradas para esta espécie de Diptera em outras partes do mundo. A falta de controle específico no sistema domiciliário de abastecimento de água tem sido a causa mais provável de infestação. Este registro amplia a distribuição de E. tenax e das miasis gastrointestinais humanas em América do Sul até os 41º 03's.<br>The myiasis observed in Bariloche are characterized and the probable conditions under which the infestations took place established. The larvae obtained from faeces of 2 patients were identified as Eristalis tenax (Diptera: Syrphidae) according to Hartley (1961) and Organización Panamericana de la Salud keys (1962). These 2 cases of human gastrointestinal myiasis were the first to be registered in Bariloche (Patagonia, Argentina) and their characteristics were similar to those described for this species in other parts of the world. The lack of specific control measures in the domestic water supply system was the most probable cause of the infestation. This event extends the distribution of E. tenax and human gastrointestinal myiasis in South America to 41º 03' S

Difilobotriasis humana en la Patagonia, Argentina Human diphyllobothriasis in Patagonia, Argentina

OBJETIVO: El objetivo del trabajo fué detectar hospedadores humanos en la zona andino patagónica argentina, teniendo en cuenta las prácticas de pesca desportiva y la importancia de los salmónidos dentro de la zona. MATERIAL Y METODO: Entre 1986 y 1995 se implementaron Campañas de Información en los laboratorios de Análisis Clínicos de la región andinopatagónica argentina, destinadas a lograr una detección más eficiente de la difilobotriasis, a través de análisis coproparasitológicos. RESULTADOS: Adicionalmente, se confeccionaron planillas destinadas a recoger información sobre las características de la infección, del tratamiento y del paciente. Durante este período se detectaron 13 nuevos casos humanos, por identificación directa del parásito o por la presencia de huevos en materia fecal. Las características de las infecciones responden a las descriptas para el género Diphyllobothrium. CONCLUSIONES: En la región, los salmónidos son los peces predilectos en la pesca deportiva. Estos peces, frecuentemente parasitados con larvas, constituyen la principal fuente de contagio para el hombre al ser consumidos insuficientemente cocidos o ahumados en frío.<br>OBJECTIVE: In view of the amateur fishing practices and the importance of salmonids in the region the study sets out to detect human hosts in the Andean-Patagonian zone. MATERIAL AND METHOD: Information campaigns were carried out by Clinical Analysis Laboratories of Andean Patagonia between 1986 and 1995 to detect diphyllobothriasis more efficiently by means of coproparasitological analysis. RESULTS: Further, forms were prepared for the collection of information about infection, treatment and the characteristics of the human host. During this period 13 new cases were registered either through direct identification of the parasite or through the presence of eggs in the faeces. The characteristics of infection are similar to those described for the genus Diphyllobothrium. CONCLUSIONS: The favourite game fish in Andean Patagonia are salmonids. This fish, often infected with plerocercoids, when eaten insufficiently cooked or cold smoked, constitutes the main source of human infection