Investigating the outcomes of virus coinfection within and across host species.

Interactions between coinfecting pathogens have the potential to alter the course of infection and can act as a source of phenotypic variation in susceptibility between hosts. This phenotypic variation may influence the evolution of host-pathogen interactions within host species and interfere with patterns in the outcomes of infection across host species. Here, we examine experimental coinfections of two Cripaviruses-Cricket Paralysis Virus (CrPV), and Drosophila C Virus (DCV)-across a panel of 25 Drosophila melanogaster inbred lines and 47 Drosophilidae host species.

Infection History and Current Coinfection With Schistosoma mansoni Decreases Plasmodium Species Intensities in Preschool Children in Uganda.

Malaria-schistosomiasis coinfections are common in sub-Saharan Africa but studies present equivocal results regarding the interspecific relationships between these parasites. Through mixed-model analyses of a dataset of Ugandan preschool children, we explore how current coinfection and prior infection with either Schistosoma mansoni or Plasmodium species alter subsequent Plasmodium intensity, Plasmodium risk, and S mansoni risk. Coinfection and prior infections with S mansoni were associated with reduced Plasmodium intensity, moderated by prior Plasmodium infections, wealth, and host age.

A One Health Approach to Child Stunting: Evidence and Research Agenda.

Stunting (low height for age) affects approximately one-quarter of children aged < 5 years worldwide. Given the limited impact of current interventions for stunting, new multisectoral evidence-based approaches are needed to decrease the burden of stunting in low- and middle-income countries (LMICs). Recognizing that the health of people, animals, and the environment are connected, we present the rationale and research agenda for considering a One Health approach to child stunting.

Predicting the effects of parasite co-infection across species boundaries.

It is normal for hosts to be co-infected by parasites. Interactions among co-infecting species can have profound consequences, including changing parasite transmission dynamics, altering disease severity and confounding attempts at parasite control. Despite the importance of co-infection, there is currently no way to predict how different parasite species may interact with one another, nor the consequences of those interactions.

Breaking beta: deconstructing the parasite transmission function.

Transmission is a fundamental step in the life cycle of every parasite but it is also one of the most challenging processes to model and quantify. In most host-parasite models, the transmission process is encapsulated by a single parameter Many different biological processes and interactions, acting on both hosts and infectious organisms, are subsumed in this single term. There are, however, at least two undesirable consequences of this high level of abstraction.

Endemic infection reduces transmission potential of an epidemic parasite during co-infection.

Endemic, low-virulence parasitic infections are common in nature. Such infections may deplete host resources, which in turn could affect the reproduction of other parasites during co-infection. We aimed to determine whether the reproduction, and therefore transmission potential, of an epidemic parasite was limited by energy costs imposed on the host by an endemic infection.

Coinfection: doing the math.

A transmission model clarifies the effects of influenza on pneumococcal pneumonia and bridges the gap between individual animal experiments and human epidemiological data (Shrestha et al., this issue).

The relative contribution of co-infection to focal infection risk in children.

Co-infection is ubiquitous in people in the developing world but little is known regarding the potential for one parasite to act as a risk factor for another. Using generalized linear mixed modelling approaches applied to data from school-aged children from Zanzibar, Tanzania, we determined the strength of association between four focal infections (i.e.

How to make DNA count: DNA-based diagnostic tools in veterinary parasitology.

Traditional methods for the diagnosis of parasitic helminth infections of livestock have a number of limitations, such as the inability to distinguish mixed-species infections, a heavy reliance on technical experience and also sub-sampling errors. Some of these limitations may be overcome through the development of rapid and accurate DNA-based tests. For example, DNA-based tests can specifically detect individual species in a mixed infection at either the larval or egg stages, in the absence of morphological differences among species.

Detecting interspecific macroparasite interactions from ecological data: patterns and process.

There is great interest in the occurrence and consequences of interspecific interactions among co-infecting parasites. However, the extent to which interactions occur is unknown, because there are no validated methods for their detection. We developed a model that generated abundance data for two interacting macroparasite (e.

Functional group/guild modelling of inter-specific pathogen interactions: a potential tool for predicting the consequences of co-infection.

Although co-infection is the norm in most human and animal populations, clinicians currently have no practical tool to assist them in choosing the best treatment strategy for such patients. Given the vast range of potential pathogens which may co-infect the host, obtaining such a practical tool may seem an intractable problem. In ecology the joint concepts of functional groups and guilds have been used to conceptually simplify complex ecosystems, in order to understand how their component parts interact and may be manipulated.

Pathogen interactions, population cycles, and phase shifts.

Interspecific pathogen interactions can profoundly affect pathogen population dynamics and the efficacy of control strategies. However, many pathogens exhibit cyclic abundance patterns (e.g.

Pathogen responses to host immunity: the impact of time delays and memory on the evolution of virulence.

Current analytical models of the mammalian immune system typically assume a specialist predator-prey relationship between invading pathogens and the active components of the immune response. However, in reality, the specific immune system is not immediately effective following invasion by a novel pathogen. First, there may be an explicit time delay between infection and immune initiation and, second, there may be a gradual build-up in immune efficacy (for instance, during the period of B-cell affinity maturation) during which the immune response develops, before reaching maximal specificity to the pathogen.

The effect of single and concomitant pathogen infections on condition and fecundity of the wild rabbit (Oryctolagus cuniculus).

We assessed the effect of two pathogens (myxoma virus and Eimeria stiedae) and five macroparasites (gastrointestinal helminth species) of the wild rabbit (Oryctolagus cuniculus) upon total host body mass and abdominal fat level. Additionally, we assessed the effects of these organisms on the number of foetuses in adult females during the peak breeding period. Both mass of abdominal fat and total body mass of the rabbit were negatively associated with myxoma virus infection and increasing helminth species richness.

Competition and mutualism among the gut helminths of a mammalian host.

Most animal species are infected with multiple parasite species; however, the role of interspecific parasite interactions in influencing parasite dynamics and shaping parasite communities has been unclear. Although laboratory studies have found evidence of cross-immunity, immunosuppression and competition, analyses of hosts in the field have generally concluded that parasite communities are little more than random assemblages. Here we present evidence of consistent interspecific interactions in a natural mammalian system, revealed through the analysis of parasite intensity data collected from a free-ranging rabbit (Oryctolagus cuniculus) population, sampled monthly for a period of 23 yr.

Mixed models: getting the best use of parasitological data.

Statistical analysis of parasitological data provides a powerful method for understanding the biological processes underlying parasite infection. However, robust and reliable analysis of parasitological data from natural and experimental infections is often difficult where: (1) the distribution of parasites between hosts is aggregated; (2) multiple measurements are made on the same individual host in longitudinal studies; or (3) data are from 'noisy' natural systems. Mixed models, which allow multiple error terms, provide an excellent opportunity to overcome these problems, and their application to the analysis of various types of parasitological data are reviewed here.

New world origins for haemoparasites infecting United Kingdom grey squirrels (Sciurus carolinensis), as revealed by phylogenetic analysis of bartonella infecting squirrel populations in England and the United States.

Phylogenetic analyses of bartonella have suggested divergence between bartonellae that infect mammals native to the Old and New Worlds. We characterized bartonella isolated from Eastern grey squirrels (Sciurius carolinensis) in the United States and from grey and red squirrels (Sciurus vulgaris) in the United Kingdom by nucleotide sequence comparison (gltA and groEL). Isolates from grey squirrels in the United States and the United Kingdom were identical, and most similar to Bartonella vinsonii, a species associated with New World rodents.

Patterns of parasite aggregation in the wild European rabbit (Oryctolagus cuniculus).

Understanding the factors controlling the distribution of parasites within their host population is fundamental to the wider understanding of parasite epidemiology and ecology. To explore changes in parasite aggregation, Taylor's power law was used to examine the distributions of five gut helminths of the wild rabbit. Aggregation was found to be a dynamic process that varied with year, season, host sex, age class, and myxomatosis.

The impact of acne: a study of adolescents' attitudes, perception and knowledge.

Aim: To assess adolescent students' attitudes to, perceptions and knowledge of acne and to assess the effect of acne on daily living.

Method: Students from Auckland sixth and seventh form classes were selected from ten Auckland secondary schools using a randomisation process which ensured proportional representation by socioeconomic group and gender. Eight hundred and forty-seven students completed a written questionnaire on the subject of acne vulgaris and had their acne examined.

Prevalence of acne vulgaris in Auckland senior high school students.

Aim: To assess the prevalence and severity of acne vulgaris in adolescent students.

Method: 867 students in Auckland sixth and seventh form classes were interviewed on the subject of acne vulgaris. Of these 847 students were examined and graded for severity of their acne using a modification of the Leeds technique which ranks severity according to number, extent and nature of the acne lesion.

The effect of interdental continuous loop wire splinting and intermaxillary fixation on the marginal gingiva.

To study the influence of interdental loop-wire splinting and intermaxillary fixation on the marginal gingiva, 30 patients were evaluated clinically using different periodontal parameters, at 5 examination times. It was shown that despite a standardized oral hygiene regime including the use of a mouthrinse, gingival inflammation occurred for the duration of the splinting period. Factors other than the presence of limited plaque, such as gingival trauma due to splint application and subsequent mechanical irritation should be considered as possible aetiological factors.