Associated bacterial communities, confrontation studies, and comparative genomics reveal important interactions between Morchella with Pseudomonas spp.

Members of the fungal genus Morchella are widely known for their important ecological roles and significant economic value. In this study, we used amplicon and genome sequencing to characterize bacterial communities associated with sexual fruiting bodies from wild specimens, as well as vegetative mycelium and sclerotia obtained from Morchella isolates grown in vitro. These investigations included diverse representatives from both Elata and Esculenta Morchella clades. Unique bacterial community compositions were observed across the various structures examined, both within and across individual Morchella isolates or specimens. However, specific bacterial taxa were frequently detected in association with certain structures, providing support for an associated core bacterial community. Bacteria from the genus Pseudomonas and Ralstonia constituted the core bacterial associates of Morchella mycelia and sclerotia, while other genera (e.g., Pedobacter spp., Deviosa spp., and Bradyrhizobium spp.) constituted the core bacterial community of fruiting bodies. Furthermore, the importance of Pseudomonas as a key member of the bacteriome was supported by the isolation of several Pseudomonas strains from mycelia during in vitro cultivation. Four of the six mycelial-derived Pseudomonas isolates shared 16S rDNA sequence identity with amplicon sequences recovered directly from the examined fungal structures. Distinct interaction phenotypes (antagonistic or neutral) were observed in confrontation assays between these bacteria and various Morchella isolates. Genome sequences obtained from these Pseudomonas isolates revealed intriguing differences in gene content and annotated functions, specifically with respect to toxin-antitoxin systems, cell adhesion, chitinases, and insecticidal toxins. These genetic differences correlated with the interaction phenotypes. This study provides evidence that Pseudomonas spp. are frequently associated with Morchella and these associations may greatly impact fungal physiology.

Gender and sex bias in COVID-19 epidemiological data through the lens of causality.

The COVID-19 pandemic has spurred a large amount of experimental and observational studies reporting clear correlation between the risk of developing severe COVID-19 (or dying from it) and whether the individual is male or female. This paper is an attempt to explain the supposed male vulnerability to COVID-19 using a causal approach. We proceed by identifying a set of confounding and mediating factors, based on the review of epidemiological literature and analysis of sex-dis-aggregated data. Those factors are then taken into consideration to produce explainable and fair prediction and decision models from observational data. The paper outlines how non-causal models can motivate discriminatory policies such as biased allocation of the limited resources in intensive care units (ICUs). The objective is to anticipate and avoid disparate impact and discrimination, by considering causal knowledge and causal-based techniques to compliment the collection and analysis of observational big-data. The hope is to contribute to more careful use of health related information access systems for developing fair and robust predictive models.

Effects of multiple feedings on sensitized rabbits on the fitness of Phlebotomus papatasi (Diptera: Psychodidae).

In the present study, we evaluated the effects of antibodies anti-sandfly saliva on the fecundity of Phlebotomus papatasi, vector of zoonotic cutaneous leishmaniasis in the Old World. Rabbits were repeatedly exposed to sandfly bites. Immune sera showed increased levels of anti-sandfly saliva antibody compared to the pre-exposition period. The analysis of biological parameters revealed no decline on the feeding success of females P. papatasi fed on rabbits repeatedly exposed to sandfly bites. Our results showed that anti-sandfly saliva antibodies of rabbits are not detrimental to the fitness of females P. papatasi. Thus, rabbits did not acquire resistance to sandflies following repeated exposures, and that contribute in maintaining a high density of P. papatasi. To control sandfly infestations and Leishmania transmission, more studies are needed for a better understanding of the mechanisms governing the resistance of hosts to bites of sandflies.

Correction: Enhanced attraction of sand fly vectors of Leishmania infantum to dogs infected with zoonotic visceral leishmaniasis.

[This corrects the article DOI: 10.1371/journal.pntd.0009647.].

Risk Assessment of the Role of the Ecotones in the Transmission of Zoonotic Cutaneous Leishmaniasis in Central Tunisia.

Zoonotic cutaneous leishmaniasis (ZCL), endemic in Central and Southern Tunisia, is caused by Leishmania major (Kinetoplastida: Trypanosomatidae), which is transmitted by the sand fly Phlebotomus papatasi. In Tunisia, the fat sand rat Psammomys obesus and the desert jird Meriones shawi are the principal reservoir hosts of L. major. The presence of the P. papatasi vector of the L. major etiologic agent of ZCL was assessed in the vicinity of villages in endemic areas of Central Tunisia. The study was performed from September through October 2019, a period corresponding to the main peak of activity of P. papatasi. Sand flies were collected from rodent burrows located at the ecotone level, which is the transition zone between the natural environment and human settlement. Sand flies were identified to species level and tested for the presence of L. major by PCR. Our entomological survey showed that P. papatasi is the most abundant sand fly species associated with rodent burrows, and this abundance is even higher in ecotones primarily occupied by P. obesus in comparison to ecotones occupied by M. shawi. Infections with Leishmania major were detected only in P. papatasi, with an overall minimum infection rate (MIR) of 2.64%. No significant difference was observed between the MIRs in ecotones of P. obesus and of M. shawi. Incidence of ZCL in the studied areas ranged from 200 to 700 cases per 100,000 inhabitants, with a mean incidence of 385.41 per 100,000. Higher ZCL incidence was identified in ecotones of M. shawi compared to ecotones of P. obesus. ZCL cases are positively correlated with the MIRs. Considering the short flight range of P. papatasi, increases in its densities associated with burrows of P. obesus or M. shawi at the ecotone level expand the overlap of infected vectors with communities and subsequently increase ZCL incidence. Therefore, control measures should target P. papatasi populations at the ecotones.

Enhanced attraction of sand fly vectors of Leishmania infantum to dogs infected with zoonotic visceral leishmaniasis.

BACKGROUND: The sand fly Phlebotomus perniciosus is the main vector of Leishmania infantum, etiological agent of zoonotic visceral leishmaniasis in the Western Mediterranean basin. Dogs are the main reservoir host of this disease. The main objective of this study was to determine, under both laboratory and field conditions, if dogs infected with L. infantum, were more attractive to female P. perniciosus than uninfected dogs. METHODOLOGY/PRINCIPAL FINDINGS: We carried out a series of host choice experiments and found that infected dogs were significantly more attractive to P. perniciosus than uninfected dogs in the laboratory as well as in the field. Significantly more P. perniciosus fed on infected dogs than on uninfected dogs. However, the fecundity of P. perniciosus fed on infected dogs was adversely impacted compared to uninfected dogs by lowering the number of laid eggs. Phlebotomus perfiliewi, the second most abundant sand fly species in the field site and a competent vector of L. infantum had similar trends of attractivity as P. perniciosus toward infected dogs under field conditions. CONCLUSIONS: The results strongly suggest that L. infantum causes physiological changes in the reservoir host which lead to the host becoming more attractive to both male and female P. perniciosus. These changes are likely to improve the chance of successful transmission because of increased contact with infected hosts and therefore, infected dogs should be particularly targeted in the control of zoonotic visceral leishmaniasis in North Africa.

The Impact of Illegal Waste Sites on the Transmission of Zoonotic Cutaneous Leishmaniasis in Central Tunisia.

Illegal waste disposal represents a risk health factor for vector-borne diseases by providing shelter for rodents and their ectoparasites. The presence of the Phlebotomus papatasi vector of Leishmania major, an etiologic agent of zoonotic cutaneous leishmaniasis (ZCL), was assessed at illegal waste sites located at the vicinity of villages in endemic areas of Central Tunisia. The study was performed over a two-year period over three nights from July to September 2017, and over three nights in September 2018. Household waste is deposited illegally forming dumpsites at the vicinity of each village and contains several rodent burrows of Psammomys obesus, the main reservoir host of L. major. Sandflies were collected from rodent burrows in the natural environment and in dumpsites using sticky traps and were identified at species level. Female sandflies were tested for the presence of L. major by PCR. Our entomological survey showed that Phlebotomus papatasi is the most abundant sandfly species associated with rodent burrows in these waste sites. The densities of P. papatasi in dumpsites are significantly higher compared to the natural environment. The minimum infection rate of P. papatasi with L. major in these illegal waste sites is not significantly different compared to the natural environment. Considering the short flight range of P. papatasi, increases in its densities, associated with burrows of P. obesus in illegal waste sites located at the edge of villages, expands the overlap of infected ZCL vectors with communities. Thus, illegal waste sites pose a high risk of spreading ZCL to neighboring home ranges. Waste management is an environmentally friendly method of controlling sandfly populations and should be included in an integrated management program for controlling ZCL in endemic countries.