Ácaros (Acari: mesostigmata) en la interface doméstico-silvestre: aves de corral y aves paseriformes

Las aves silvestres han sido consideradas una posible fuente de ácaros mesostigmátidos en granjas de gallinas ponedoras, aunque pocos estudios se han enfocado en probar esta hipótesis. Adicionalmente, es escaso el conocimiento que se tiene sobre los ácaros parásitos presentes en sistemas comerciales de gallinas ponedoras en el sur de Sudamérica. Durante dos años fueron colectadas muestras de manera sistemática de gallinas ponedoras, aves silvestres adultas y pichones capturados en el ambiente de las granjas. Fueron cuantificados los ácaros del orden Mesostigmata, y una proporción de ellos fue identificada morfológicamente hasta el nivel de especie.Centro de Estudios Parasitológicos y de Vectore

Effect of Biodiversity Changes in Disease Risk: Exploring Disease Emergence in a Plant-Virus System

The effect of biodiversity on the ability of parasites to infect their host and cause disease (i.e. disease risk) is a major question in pathology, which is central to understand the emergence of infectious diseases, and to develop strategies for their management. Two hypotheses, which can be considered as extremes of a continuum, relate biodiversity to disease risk: One states that biodiversity is positively correlated with disease risk (Amplification Effect), and the second predicts a negative correlation between biodiversity and disease risk (Dilution Effect). Which of them applies better to different host-parasite systems is still a source of debate, due to limited experimental or empirical data. This is especially the case for viral diseases of plants. To address this subject, we have monitored for three years the prevalence of several viruses, and virus-associated symptoms, in populations of wild pepper (chiltepin) under different levels of human management. For each population, we also measured the habitat species diversity, host plant genetic diversity and host plant density. Results indicate that disease and infection risk increased with the level of human management, which was associated with decreased species diversity and host genetic diversity, and with increased host plant density. Importantly, species diversity of the habitat was the primary predictor of disease risk for wild chiltepin populations. This changed in managed populations where host genetic diversity was the primary predictor. Host density was generally a poorer predictor of disease and infection risk. These results support the dilution effect hypothesis, and underline the relevance of different ecological factors in determining disease/infection risk in host plant populations under different levels of anthropic influence. These results are relevant for managing plant diseases and for establishing conservation policies for endangered plant species

True versus False Parasite Interactions: A Robust Method to Take Risk Factors into Account and Its Application to Feline Viruses

International audienceBACKGROUND: Multiple infections are common in natural host populations and interspecific parasite interactions are therefore likely within a host individual. As they may seriously impact the circulation of certain parasites and the emergence and management of infectious diseases, their study is essential. In the field, detecting parasite interactions is rendered difficult by the fact that a large number of co-infected individuals may also be observed when two parasites share common risk factors. To correct for these "false interactions", methods accounting for parasite risk factors must be used. METHODOLOGY/PRINCIPAL FINDINGS: In the present paper we propose such a method for presence-absence data (i.e., serology). Our method enables the calculation of the expected frequencies of single and double infected individuals under the independence hypothesis, before comparing them to the observed ones using the chi-square statistic. The method is termed "the corrected chi-square." Its robustness was compared to a pre-existing method based on logistic regression and the corrected chi-square proved to be much more robust for small sample sizes. Since the logistic regression approach is easier to implement, we propose as a rule of thumb to use the latter when the ratio between the sample size and the number of parameters is above ten. Applied to serological data for four viruses infecting cats, the approach revealed pairwise interactions between the Feline Herpesvirus, Parvovirus and Calicivirus, whereas the infection by FIV, the feline equivalent of HIV, did not modify the risk of infection by any of these viruses. CONCLUSIONS/SIGNIFICANCE: This work therefore points out possible interactions that can be further investigated in experimental conditions and, by providing a user-friendly R program and a tutorial example, offers new opportunities for animal and human epidemiologists to detect interactions of interest in the field, a crucial step in the challenge of multiple infections

Disposal of industrial lump sulphur by-productin soil. Influence on soil chemical and biochemical properties and on yeld and quality of sugar beet (Beta vulgaris L)

A field experiment was carried out to evaluate modifications on the chemical and biochemical parameters of an agricultural alkaline soil (pH=8.31) under sugar beet (Beta vulgaris L.) by applying different amounts of sulphur by-product coming from oil desulphurization process. Soil chemical properties such as sulphate formation, pH, soil electrical conductivity (EC), total and extractable organic carbon (TOC and TEC), and biochemical parameters such as microbial biomass carbon content (MBC) and total hydrolytic capacity (FDA-hydrolysis), arylsulphatase (ArS-ase) and o-diphenoloxidase (o-DPO), were monitored. Commercial parameters of yield and quality production of sugar beet (yield of roots, % of polarization, extractable saccharose content and purity of thick juice) were also determined. All soil chemical and biochemical properties and commercial parameters of sugar beet were monitored in plots treated with 1 (S1), 5 (S5) and 10 (S10) t ha-1 of sulphur by-product and compared with untreated plots (S0). In S1, 60 days after amendment the highest values of sulphate formed (310 mg kg-1) and the EC (1596 mS cm-1), were observed. In S5, the sulphate formed was 2583 mg kg-1 and soil EC was 4138 mS cm-1 after 210 days, while in S10 the amount of sulphur added probably exceeded soil oxidation capacity since it continued more slowly till the end of the experiment. After 210 days, soil pH reached the lowest value in all the treated plots and it was 7.75, 7.52 and 7.26 in S1, S5 and S10, respectively. No significant modifications were made on soil biochemical parameters tested by the different amounts of sulphur added. A decrease in the production yield of sugar beet (27.2%) was found only when the highest amount of sulphur was applied. In contrast, no worsening of main commercial parameters was observed

Dynamics of exposure to Rickettsia parkeri in cattle in the paraná river delta, Argentina

Several cases of human rickettsiosis caused by Rickettsia parkeri were recently documented in the Paraná River delta of Argentina, where the tick vector is Amblyomma triste Koch. As cattle suffer recurrent A. triste infestations, they are at risk of becoming infected with R. parkeri. Herein we investigated the dynamics of R. parkeri and its A. triste vector in a herd of beef cattle. Cattle were followed for 18mo and samples were analyzed for the presence of antibodies against four Rickettsia species (R. parkeri, Rickettsia bellii, Rickettsia amblyommii, and Rickettsia felis) and also for the presence of rickettsial DNA. Additionally, cattle were examined for attached ticks and questing adult ticks were collected. All ticks were analyzed for the presence of rickettsial DNA. No evidence of rickettsemia was found in any cow, but the high R. parkeri infection rate documented in A. triste both questing in the study area (13.9%) and feeding on cattle (19.8%) and the identification of antibodies against R. parkeri antigen in 90% of cattle are evidence that infection is taking place. Altogether, our data suggest that A. triste ticks are capable of naturally exposing cattle to R. parkeri. However, the progress of R. parkeri infection and its impact on bovine health and production remain to be established.Fil: Monje, Lucas Daniel. Universidad Nacional del Litoral; ArgentinaFil: Costa, F.B.. Universidade de Sao Paulo; BrasilFil: Colombo, Valeria Carolina. Universidad Nacional del Litoral; ArgentinaFil: Labruna, M.B.. Universidade de Sao Paulo; BrasilFil: Antoniazzi, Leandro Raúl. Universidad Nacional del Litoral; ArgentinaFil: Gamietea, I.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; ArgentinaFil: Nava, Santiago. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; ArgentinaFil: Beldomenico, Pablo Martín. Universidad Nacional del Litoral; Argentin