Animal Exposure and Human Plague, United States, 1970-2017

Acid phosphatase-like proteins, a biogenic amine and leukotriene-binding salivary protein family from the flea Xenopsylla cheopis

The salivary glands of hematophagous arthropods contain pharmacologically active molecules that interfere with host hemostasis and immune responses, favoring blood acquisition and pathogen transmission. Exploration of the salivary gland composition of the rat flea, Xenopsylla cheopis, revealed several abundant acid phosphatase-like proteins whose sequences lacked one or two of their presumed catalytic residues. In this study, we undertook a comprehensive characterization of the tree most abundant X. cheopis salivary acid phosphatase-like proteins. Our findings indicate that the three recombinant proteins lacked the anticipated catalytic activity and instead, displayed the ability to bind different biogenic amines and leukotrienes with high affinity. Moreover, X-ray crystallography data from the XcAP-1 complexed with serotonin revealed insights into their binding mechanisms.

Love or conflict: A qualitative study of the human-long tailed macaque interface in Nakhon Sawan Province, Thailand

A wide range of zoonotic pathogens can be transmitted during human-wildlife interactions. Few qualitative studies have been conducted on human-nonhuman primate interfaces in Thailand, notably direct and indirect contact. Since Long-tailed macaques (LTMs) are prevalent in Thailand's Banphot Phisai district, part of Nakhon Sawan province, this qualitative study was conducted in 2019 to determine in-depth contact characteristics between humans and LTMs in the communities. Key informant interviews (KIIs) and focus group discussions (FGDs) were conducted with 35 villagers who reported close contact with LTMs in this study location. The results showed that villagers had different levels of contact with LTMs, depending on their occupations, perceptions, beliefs, religions, previous experiences, and local regulations. Monks in temples and vendors selling food for LTMs were reported to have the closest contact with them. LTMs have been reported to destroy personal property, houses, buildings, and crops. However, the villagers do not hurt them due to their religious beliefs relating to a respected abbot (a man who headed an abbey of monks). Even community members have had extensive interaction with LTMs, but they lacked awareness and information regarding diseases transmitted to humans directly or indirectly by non-human primates. Therefore, individuals who have frequent and close contact with LTMs should be provided health education, and appropriate behavioral change communication interventions should be performed. Furthermore, the results could be used to develop future disease prevention strategies and public awareness campaigns in the area.

Revisiting the sialome of the cat flea Ctenocephalides felis

The hematophagous behaviour emerged independently in several instances during arthropod evolution. Survey of salivary gland and saliva composition and its pharmacological activity led to the conclusion that blood-feeding arthropods evolved a distinct salivary mixture that can interfere with host defensive response, thus facilitating blood acquisition and pathogen transmission. The cat flea, Ctenocephalides felis, is the major vector of several pathogens, including Rickettsia typhi, Rickettsia felis and Bartonella spp. and therefore, represents an important insect species from the medical and veterinary perspectives. Previously, a Sanger-based sialome of adult C. felis female salivary glands was published and reported 1,840 expressing sequence tags (ESTs) which were assembled into 896 contigs. Here, we provide a deeper insight into C. felis salivary gland composition using an Illumina-based sequencing approach. In the current dataset, we report 8,892 coding sequences (CDS) classified into 27 functional classes, which were assembled from 42,754,615 reads. Moreover, we paired our RNAseq data with a mass spectrometry analysis using the translated transcripts as a reference, confirming the presence of several putative secreted protein families in the cat flea salivary gland homogenates. Both transcriptomic and proteomic approaches confirmed that FS-H-like proteins and acid phosphatases lacking their putative catalytic residues are the two most abundant salivary proteins families of C. felis and are potentially related to blood acquisition. We also report several novel sequences similar to apyrases, odorant binding proteins, antigen 5, cholinesterases, proteases, and proteases inhibitors, in addition to putative novel sequences that presented low or no sequence identity to previously deposited sequences. Together, the data represents an extended reference for the identification and characterization of the pharmacological activity present in C. felis salivary glands.

Plague risk in the western United States over seven decades of environmental change

After several pandemics over the last two millennia, the wildlife reservoirs of plague (Yersinia pestis) now persist around the world, including in the western United States. Routine surveillance in this region has generated comprehensive records of human cases and animal seroprevalence, creating a unique opportunity to test how plague reservoirs are responding to environmental change. Here, we test whether animal and human data suggest that plague reservoirs and spillover risk have shifted since 1950. To do so, we develop a new method for detecting the impact of climate change on infectious disease distributions, capable of disentangling long-term trends (signal) and interannual variation in both weather and sampling (noise). We find that plague foci are associated with high-elevation rodent communities, and soil biochemistry may play a key role in the geography of long-term persistence. In addition, we find that human cases are concentrated only in a small subset of endemic areas, and that spillover events are driven by higher rodent species richness (the amplification hypothesis) and climatic anomalies (the trophic cascade hypothesis). Using our detection model, we find that due to the changing climate, rodent communities at high elevations have become more conducive to the establishment of plague reservoirs-with suitability increasing up to 40% in some places-and that spillover risk to humans at mid-elevations has increased as well, although more gradually. These results highlight opportunities for deeper investigation of plague ecology, the value of integrative surveillance for infectious disease geography, and the need for further research into ongoing climate change impacts.

Epidemiological Situation on Plague in 2020. Forecast of Episootic Activity of Natural Plague Foci in the Russian Federation and Other CIS Countries for 2021

The aim of the work was to substantiate the forecast of the epidemiological and epizootiological situation in natural foci of plague in the Russian Federation, countries of the near and far abroad for the year of 2021. Characteristics of the distribution of Yersinia pestis strains of the main subspecies (subspecies pestis) of medieval and antique biovars, Caucasian (ssp. caucasica) and central Asian (ssp. central asiatica) subspecies by 45 natural foci of the CIS countries are presented in the paper. The persistence of a multidirectional trend in the dynamics of epizootic activity of natural foci of the CIS countries with the circulation of Y. pestis pestis strains of the medieval biovar of the 2.MED1 phylogenetic branch and the antique biovar of the 0.ANT5, 4.ANT phylogenetic branches in the current decade has been outlined. For the Russian Federation, the development of epizootics is predicted in the Gorno-Altai highland and Tuva mountain natural foci caused by the circulation of Y. pestis pestis strains of the antique biovar 4.ANT and Y. pestis of the Altai biovar of the Central Asian subspecies 0.PE4a in 2021. For the Republic of Kazakhstan, there is a high probability of preserving epizootic activity in the North Aral, Aral-Karakum, Balkhash, Mojynkum, Taukum desert and Ili intermountain natural foci with the circulation of Y. pestis pestis strains of the medieval biovar of the phylogenetic branch 2.MED1. For the Kyrgyz Republic, the forecast for the development of plague epizootics caused by Y. pestis pestis strains of the antique biovar 0.ANT5 phylogenetic branch in the Sarydzhaz and Upper Naryn high-mountain natural foci has been substantiated. A high epidemic risk of epizootic manifestations caused by highly virulent strains of Y. pestis pestis of antique biovars 0.ANT5, 4.ANT and medieval biovar 2.MED1 for the entire territory of the CIS countries is noted. The relevance of implementing forecasts of the epidemiological situation into practice, taking into account the molecular-genetic and epidemiological characteristics of Y. pestis strains circulating in areas of expected epizootic manifestations of plague, is highlighted.

Yersinia pestis: the Natural History of Plague

The Gram-negative bacterium Yersinia pestis is responsible for deadly plague, a zoonotic disease established in stable foci in the Americas, Africa, and Eurasia. Its persistence in the environment relies on the subtle balance between Y. pestis-contaminated soils, burrowing and nonburrowing mammals exhibiting variable degrees of plague susceptibility, and their associated fleas. Transmission from one host to another relies mainly on infected flea bites, inducing typical painful, enlarged lymph nodes referred to as buboes, followed by septicemic dissemination of the pathogen. In contrast, droplet inhalation after close contact with infected mammals induces primary pneumonic plague. Finally, the rarely reported consumption of contaminated raw meat causes pharyngeal and gastrointestinal plague. Point-of-care diagnosis, early antibiotic treatment, and confinement measures contribute to outbreak control despite residual mortality. Mandatory primary prevention relies on the active surveillance of established plague foci and ectoparasite control. Plague is acknowledged to have infected human populations for at least 5,000 years in Eurasia. Y. pestis genomes recovered from affected archaeological sites have suggested clonal evolution from a common ancestor shared with the closely related enteric pathogen Yersinia pseudotuberculosis and have indicated that ymt gene acquisition during the Bronze Age conferred Y. pestis with ectoparasite transmissibility while maintaining its enteric transmissibility. Three historic pandemics, starting in 541 AD and continuing until today, have been described. At present, the third pandemic has become largely quiescent, with hundreds of human cases being reported mainly in a few impoverished African countries, where zoonotic plague is mostly transmitted to people by rodent-associated flea bites.