Models of virulence evolution for horizontally transmitted parasites often assume that transmission rate (the probability that an infected host infects a susceptible host) and virulence (the increase in host mortality due to infection) are positively correlated, because higher rates of production of propagules may cause more damages to the host. However, empirical support for this assumption is...

The intracellular parasite Toxoplasma gondii has multiple strategies to alter host cell function, including the injection of rhoptry proteins into the cytosol of host cells as well as bystander populations, but the consequence of these events is unclear. Here, a reporter system using fluorescent parasite strains that inject Cre recombinase with their rhoptry proteins (Toxoplasma-Cre) was combin...

ophionyssus natricis is a purely blood sucking parasite of snakes and of worldwide distribution. infected snakes often exhibit lethargy, pruritus, crusting dermatitis,and behavioral changes. ophionyssus natricis can also attack humans, causing popular vesiculo-bullous eruption of the skin. a 29 years old man working in zoo,sari, mazandaran, iran, presented itchy papullar eruption of the skin. h...

Phosphorus (P) is an essential nutrient for growth in consumers. P-limitation and parasite infection comprise one of the most common stressor pairs consumers confront in nature. We conducted a life-table study using a Daphnia-microsporidian parasite model, feeding uninfected or infected Daphnia with either P-sufficient or P-limited algae, and assessed the impact of the two stressors on life-his...

The degree to which parasites use hosts is fundamental to host-parasite coevolution studies, yet difficult to assess and interpret in an evolutionary manner. Previous assessments of parasitism in eugregarine-host systems suggest high degrees of host specificity to particular host stages and host species; however, rarely have the evolutionary constraints on host specificity been studied experime...

Black Carp (Mylopharyngodon piceus) has invaded the Mississippi River and is a potential threat to native mollusks. During prior diet research, we discovered that fluke Aspidogaster conchicola, mollusk parasite, occurs regularly in gastrointestinal tract of Carp. The remains fish intestines for extended periods after consumed its host. Flukes were found 33% wild examined, numbers ranged from 1 ...

This study investigated why the susceptible or resistance phenotype to the nematode Heligmosomoides polygyrus was lost when susceptible (C57BL/6) and resistant (Balb/c) strains of mice were housed together in indoor arenas with continuous transmission of the parasite larvae present in peat trays (Scott, 1991). First, both strains expressed their normal phenotype when given a controlled challeng...

the purpose of this study was to investigate the status and epidemiology of intestinal parasites in iran. the information was driven from an extensive health survey which was done by the ministry of health and medical education, deputy of research affairs in 1990-92. sampling fraction was 1 per 1000 of individuals aged between 2 and 69, the sampling method was cluster sampling and each cluster ...

1. A 39-year bumblebee data base was used to study the codistribution of six cuckoo bumblebees in the subgenus Psythirus of Bombus (hereafter called Psythirus) and their free-living bumblebee hosts in the British Isles. 2. A model of nest parasitism predicted host threshold densities and stable deterministic dynamics, with fluctuations only emerging as a result of environmental or demographic s...

The spatial distribution of individuals of any species is a basic concern of ecology. The spatial distribution of parasites matters to control and conservation of parasites that affect human and nonhuman populations. This paper develops a quantitative theory to predict the spatial distribution of parasites based on the distribution of parasites in hosts and the spatial distribution of hosts. Fo...