Zoonotic focus of plague, Algeria

An overview of fleas (Siphonaptera) in wild and domestic mammals from Algeria with new data from the central north and south of the country

Fleas (Siphonaptera) are medically and veterinary important ectoparasites known to infest a wide range of host species. This study presents a systematic review complemented by new data on the diversity of flea species and host associations in Algeria. 198 mammals were examined, including previously understudied hosts such as sheep, red foxes, fennec foxes, and golden African wolves. Of these animals, 108 (54.55%) were infested with fleas. Overall, 1.906 fleas belonging to seven species (Archaeopsylla erinacei s.l., Ctenocephalides felis, C. canis, Nosopsyllus fasciatus, Pariodontis riggenbachi, Pulex irritans, Xenopsylla cheopis) were identified, originating from seven provinces across Algeria. Statistical analysis techniques were employed to process the data, including descriptive statistics, statistical tests, and principal component analysis (PCA). This study reveals the diverse flea fauna in Algeria and their association with various host species, including wild and domestic animals. This comprehensive survey aimed to combine literature reviews, fieldwork, and statistical analysis to understand fleas' diversity and host associations. The findings contribute to the growing knowledge of flea ecology and host-parasite interactions, with implications for public health and veterinary practices in Algeria and potentially other regions with similar ecological characteristics.

Genetic Evidence of the Black Death in the Abbey of San Leonardo (Apulia Region, Italy): Tracing the Cause of Death in Two Individuals Buried with Coins

The Abbey of San Leonardo in Siponto (Apulia, Southern Italy) was an important religious and medical center during the Middle Ages. It was a crossroads for pilgrims heading along the Via Francigena to the Sanctuary of Monte Sant’Angelo and for merchants passing through the harbor of Manfredonia. A recent excavation of Soprintendenza Archeologica della Puglia investigated a portion of the related cemetery, confirming its chronology to be between the end of the 13th and beginning of the 14th century. Two single graves preserved individuals accompanied by numerous coins dating back to the 14th century, hidden in clothes and in a bag tied to the waist. The human remains of the individuals were analyzed in the Laboratorio di Antropologia Fisica of Soprintendenza ABAP della città metropolitana di Bari. Three teeth from each individual were collected and sent to the Istituto Zooprofilattico Sperimentale di Puglia e Basilicata to study infectious diseases such as malaria, plague, tuberculosis, epidemic typhus and Maltese fever (Brucellosis), potentially related to the lack of inspection of the bodies during burial procedures. DNA extracted from six collected teeth and two additional unrelated human teeth (negative controls) were analyzed using PCR to verify the presence of human DNA (β-globulin) and of pathogens such as Plasmodium spp., Yersinia pestis, Mycobacterium spp., Rickettsia spp. and Brucella spp. The nucleotide sequence of the amplicon was determined to confirm the results. Human DNA was successfully amplified from all eight dental extracts and two different genes of Y. pestis were amplified and sequenced in 4 out of the 6 teeth. Molecular analyses ascertained that the individuals buried in San Leonardo were victims of the Black Death (1347–1353) and the data confirmed the lack of inspection of the corpses despite the presence of numerous coins. This study represents molecular evidence, for the first time, of Southern Italy’s involvement in the second wave of the plague pandemic.

Pathogen Carriage by Peri-Domestic Fleas in Western Kenya

Fleas are carriers for many largely understudied zoonotic, endemic, emerging, and re-emerging infectious disease agents, but little is known about their prevalence and role as a vector in Africa. The aim of this study was to determine the diversity of fleas and the prevalence of infectious agents in them collected from human dwellings in western Kenya. A total of 306 fleas were collected using light traps from 33 human dwellings; 170 (55.56%) were identified as Ctenocephalides spp., 121 (39.54%) as Echidnophaga gallinacea, 13 (4.25%) as Pulex irritans, and 2 (0.65%) as Xenopsylla cheopis. Of the 306 individual fleas tested, 168 (54.9%) tested positive for rickettsial DNA by a genus-specific quantitative real-time PCR (qPCR) assay based on the 17-kDa antigen gene. Species-specific qPCR assays and sequencing revealed presence of Rickettsia asembonensis in 166 (54.2%) and Rickettsia felis in 2 (0.7%) fleas. Borrelia burgdorferi, normally known to be carried by ticks, was detected in four (1.3%) flea DNA preparations. We found no evidence of Yersinia pestis, Bartonella spp., or Orientia spp. Not only were Ctenocephalides spp. the most predominant flea species in the human dwellings, but also almost all of them were harboring R. asembonensis.

Fleas and flea-borne diseases of North Africa

North Africa has an interesting and rich wildlife including hematophagous arthropods, and specifically fleas, which constitute a large part of the North African fauna, and are recognised vectors of several zoonotic bacteria. Flea-borne organisms are widely distributed throughout the world in endemic disease foci, where components of the enzootic cycle are present. Furthermore, flea-borne diseases could re-emerge in epidemic form because of changes in the vector-host ecology due to environmental and human behaviour modifications. We need to know the real incidences of flea-borne diseases in the world due to this incidence could be much greater than are generally recognized by physicians and health authorities. As a result, diagnosis and treatment are often delayed by health care professionals who are unaware of the presence of these infections and thus do not take them into consideration when attempting to determine the cause of a patient's illness. In this context, this bibliographic review aims to summarise the main species of fleas present in North Africa, their geographical distribution, flea-borne diseases, and their possible re-emergence.

Fleas of black rats (Rattus rattus) as reservoir host of Bartonella spp. in Chile

Background

Rattus rattus is a widely distributed, invasive species that presents an important role in disease transmission, either directly or through vector arthropods such as fleas. These black rats can transmit a wide variety of pathogens, including bacteria of the genus Bartonella, which can cause diseases in humans and animals. In Chile, no data are available identifying fleas from synanthropic rodents as Bartonella vectors. The aim of this study was to investigate the prevalence of Bartonella spp. in the fleas of R. rattus in areas with different climate conditions and featuring different human population densities.

Methods

In all, 174 fleas collected from 261 R. rattus captured from 30 localities with different human densities (cities, villages, and wild areas) across five hydrographic zones of Chile (hyper-arid, arid, semi-arid, sub-humid, and hyper-humid) were examined. Bartonella spp. presence was determined through polymerase chain reaction, using gltA and rpoB genes, which were concatenated to perform a similarity analysis with BLAST and phylogenetic analysis.

Results

Overall, 15 fleas species were identified; Bartonella gltA and rpoB fragments were detected in 21.2% (37/174) and 19.5% (34/174) of fleas, respectively. A total of 10 of the 15 fleas species found were positive for Bartonella DNA. Leptopsylla segnis was the most commonly collected flea species (n = 55), and it also presented a high prevalence of Bartonella DNA (P% = 34.5%). The highest numbers of fleas of this species were collected in villages of the arid zone. There were no seasonal differences in the prevalence of Bartonella DNA. The presence of Bartonella DNA in fleas was recorded in all hydrographic areas, and the arid zone presented the highest prevalence of this species. Regarding areas with different human densities, the highest prevalence was noted in the villages (34.8% gltA and 31.8% rpoB), followed by cities (14.8% gltA and 11.1% rpoB) and wild areas (7.4% gltA and 14.8% rpoB). The BLAST analysis showed a high similitude (>96%) with four uncharacterized Bartonella genotypes and with two species with zoonotic potential: B. mastomydis and B. tribocorum. The phylogenetic analysis showed a close relationship with B. elizabethae and B. tribocorum. This is the first study to provide evidence of the presence of Bartonella in fleas of R. rattus in Chile, indicating that the villages and arid zone correspond to areas with higher infection risk.

Emerging infectious diseases in Africa in the 21st century

Many infectious diseases have emerged or reemerged in Africa in the 21st century. Some of them are associated with newly discovered microorganisms such as Rickettsia felis and Tropheryma whipplei; others are known, historical diseases such as plague and cholera. In addition are diseases related to previously known microorganisms which recently have been involved for the first time in massive outbreaks with worldwide impacts (such as Ebola virus, Zika virus and Chikungunya virus). Research on emerging infectious diseases needs to be identified as a priority.

Serological and PCR investigation of Yersinia pestis in potential reservoir hosts from a plague outbreak focus in Zambia

Background

Plague is a bacterial zoonotic disease, caused by Yersinia pestis. Rodents are the natural hosts with fleas as the vehicle of disease transmission. Domestic and wild dogs and cats have also been identified as possible disease hosts. In Zambia, plague outbreaks have been reported in the Southern and Eastern regions in the last 20 years. Based on these observations, Y. pestis could possibly be endemically present in the area.

Methods

To substantiate such possibility, sera samples were collected from rodents, shrews, dogs and cats for detection of antibodies against Fraction 1 gene (Fra1) of Y. pestis while organs from rodents and shrews, and fleas from both dogs and rodents were collected to investigate plasminogen activator gene (pla gene) of Y. pestis using ELISA and PCR respectively.

Results

A total of 369 blood samples were collected from domestic carnivores, shrews and domestic and peri-domestic rodents while 199 organs were collected from the rodents and shrews. Blood samples were tested for antibodies against Fra1 antigen using ELISA and 3% (5/165) (95% CI 0.99–6.93%) dogs were positive while all cats were negative. Of 199 sera from rodents and shrews, 12.6% (95% CI 8.30–17.98%) were positive for antibodies against Fra1 using anti-rat IgG secondary antibody while using anti-mouse IgG secondary antibody, 17.6% (95% CI 12.57–23.60%) were positive. PCR was run on the organs and 2.5% (95% CI 0.82–5.77%) were positive for plasminogen activator gene of Y. pestis and the amplicons were sequenced and showed 99% identity with Y. pestis reference sequences. All 82 fleas collected from animals subjected to PCR, were negative for pla gene. The specific rat-flea and dog-flea indices were 0.19 and 0.27 respectively, which were lower than the level required to enhance chances of the disease outbreak.

Conclusions

We concluded that plague was still endemic in the area and the disease may infect human beings if contact is enhanced between reservoir hosts and flea vectors. The lower specific rodent-flea Indices and absence of Y. pestis in the potential vectors were considered to be partly responsible for the current absence of plague outbreaks despite its presence in the sylvatic cycle.

Yersinia pestis halotolerance illuminates plague reservoirs

The plague agent Yersinia pestis persists for years in the soil. Two millennia after swiping over Europe and North Africa, plague established permanent foci in North Africa but not in neighboring Europe. Mapping human plague foci reported in North Africa for 70 years indicated a significant location at <3 kilometers from the Mediterranean seashore or the edge of salted lakes named chotts. In Algeria, culturing 352 environmental specimens naturally containing 0.5 to 70 g/L NaCl yielded one Y. pestis Orientalis biotype isolate in a 40 g/L NaCl chott soil specimen. Core genome SNP analysis placed this isolate within the Y. pestis branch 1, Orientalis biovar. Culturing Y. pestis in broth steadily enriched in NaCl indicated survival up to 150 g/L NaCl as L-form variants exhibiting a distinctive matrix assisted laser desorption-ionization time-of-flight mass spectrometry peptide profile. Further transcriptomic analyses found the upregulation of several outer-membrane proteins including TolC efflux pump and OmpF porin implied in osmotic pressure regulation. Salt tolerance of Y. pestis L-form may play a role in the maintenance of natural plague foci in North Africa and beyond, as these geographical correlations could be extended to 31 plague foci in the northern hemisphere (from 15°N to 50°N).

Plague in Iran: its history and current status

OBJECTIVES:

Plague remains a public health concern worldwide, particularly in old foci. Multiple epidemics of this disease have been recorded throughout the history of Iran. Despite the long-standing history of human plague in Iran, it remains difficult to obtain an accurate overview of the history and current status of plague in Iran.

METHODS:

In this review, available data and reports on cases and outbreaks of human plague in the past and present in Iran and in neighboring countries were collected, and information was compiled regarding when, where, and how many cases occurred.

RESULTS:

This paper considers the history of plague in Persia (the predecessor of today’s Iran) and has a brief review of plague in countries in the World Health Organization Eastern Mediterranean Region, including a range of countries in the Middle East and North Africa.

CONCLUSIONS:

Since Iran has experienced outbreaks of plague for several centuries, neighboring countries have reported the disease in recent years, the disease can be silent for decades, and the circulation of Yersinia pestis has been reported among rodents and dogs in western Iran, more attention should be paid to disease monitoring in areas with previously reported human cases and in high-risk regions with previous epizootic and enzootic activity.

Plague in Arab Maghreb, 1940-2015: A Review

We reviewed the epidemiology of 49 plague outbreaks that resulted in about 7,612 cases in 30 localities in the Arabic Maghreb (Mauritania, Morocco, Algeria, Tunisia, Libya, and Egypt) over 75 years. Between 1940 and 1950, most cases recorded in Morocco (75%) and Egypt (20%), resulted from plague imported to Mediterranean harbors and transmitted by rat ectoparasites. By contrast, the re-emergence of plague in the southern part of Western Sahara in 1953 and in northeast Libya in 1976 was traced to direct contact between nomadic populations and infected goats and camels in natural foci, including the consumption of contaminated meat, illustrating this neglected oral route of contamination. Further familial outbreaks were traced to human ectoparasite transmission. Efforts to identify the factors contributing to natural foci may guide where to focus the surveillance of sentinel animals in order to eradicate human plague, if not Yersinia pestis from the Arab Maghreb.

Enzootic plague foci, Algeria

In Algeria, PCR sequencing of pla, glpD and rpoB genes found Yersinia pestis in 18/237 (8%) rodents of five species, including Apodemus sylvaticus, previously undescribed as pestiferous; and disclosed three new plague foci. Multiple spacer typing confirmed a new Orientalis variant. Rodent survey should be reinforced in this country hosting reemerging plague.

[Importance of Shaw's Jird Meriones shawii within the trophic components of the Barn Owl Tyto alba in steppic areas of Algeria]

The study of the diet of the Barn Owl in two steppic regions (M'Sila and Djelfa) located in the Algerian highlands is based on the analysis of the pellets of rejections collected in six stations. The analysis of 706 pellets resulting from the various stations made it possible to count 1380 individuals, represented by seven classes, 12 orders, 32 families, and 76 species of preys. The mammals are consumed with variable abundance rates between 59.1 % and 90.0 % whose predominance is assigned to the rodents (relative abundance: AR > 58 %). The latter constitute the most advantageous preys in biomass (61.4 ≤ B % ≤ 99.2). The most consumed prey is Meriones shawii, with variable rates between 31.9 % and 76.6 %. Generally, Tyto alba presents a diversified diet in the majority of the stations (0.69 ≤ E ≤ 0.76), except the station of Ain El-Hadjel (E = 0.35), with a low diversity and dominance of M. shawii (AR = 76.6 %).

Plague outbreak in Libya, 2009, unrelated to plague in Algeria

After 25 years of no cases of plague, this disease recurred near Tobruk, Libya, in 2009. An epidemiologic investigation identified 5 confirmed cases. We determined ribotypes, Not1 restriction profiles, and IS100 and IS1541 hybridization patterns of strains isolated during this outbreak. We also analyzed strains isolated during the 2003 plague epidemic in Algeria to determine whether there were epidemiologic links between the 2 events. Our results demonstrate unambiguously that neighboring but independent plague foci coexist in Algeria and Libya. They also indicate that these outbreaks were most likely caused by reactivation of organisms in local or regional foci believed to be dormant (Libya) or extinct (Algeria) for decades, rather than by recent importation of Yersinia pestis from distant foci. Environmental factors favorable for plague reemergence might exist in this area and lead to reactivation of organisms in other ancient foci.

Bartonella clarridgeiae, B. henselae and Rickettsia felis in fleas from Morocco

A total of 554 fleas were collected in the Moroccan Casablanca and Tiznit regions from domesticated animals and ruminants between August 2007 and October 2008 and were tested for the presence of Rickettsia spp. and Bartonella spp. using molecular methods. For the first time in Morocco, we found Rickettsia felis, the agent of flea-borne spotted fever in Ctenocephalides felis; B. henselae, an agent of cat scratch disease; and Bartonella clarridgeiae, a cat pathogen and potentially a human pathogen.

A multi-gene analysis of diversity of Bartonella detected in fleas from Algeria

We report the molecular detection of several Bartonella species in 44 (21.5%) of 204 fleas from Algeria collected from 26 rodents and 7 hedgehogs. Bartonella elizabethae and B. clarridgeiae were detected in the fleas collected on hedgehogs. Bartonella tribocorum and B. elizabethae were detected in fleas collected from rats and mice, and sequences similar to an unnamed Bartonella sp. detected in rodents from China were detected in rats as well as a genotype of Bartonella closely related to Bartonella rochalimae detected in fleas collected on brown rats (Rattus norvegicus).

Development and evaluation of two simple, rapid immunochromatographic tests for the detection of Yersinia pestis antibodies in humans and reservoirs

Background

Tools for plague diagnosis and surveillance are not always available and affordable in most of the countries affected by the disease. Yersinia pestis isolation for confirmation is time-consuming and difficult to perform under field conditions. Serologic tests like ELISA require specific equipments not always available in developing countries. In addition to the existing rapid test for antigen detection, a rapid serodiagnostic assay may be useful for plague control.

Methods/Principal Findings

We developed two rapid immunochromatography-based tests for the detection of antibodies directed against F1 antigen of Y. pestis. The first test, SIgT, which detects total Ig (IgT) anti-F1 in several species (S) (human and reservoirs), was developed in order to have for the field use an alternative method to ELISA. The performance of the SIgT test was evaluated with samples from humans and animals for which ELISA was used to determine the presumptive diagnosis of plague. SIgT test detected anti-F1 Ig antibodies in humans with a sensitivity of 84.6% (95% CI: 0.76–0.94) and a specificity of 98% (95% CI: 0.96–1). In evaluation of samples from rodents and other small mammals, the SlgT test had a sensitivity of 87.8% (95% CI: 0.80–0.94) and a specificity of 90.3% (95% CI: 0.86–0.93). Improved performance was obtained with samples from dogs, a sentinel animal, with a sensitivity of 93% (95% CI: 0.82–1) and a specificity of 98% (95% CI: 0.95–1.01). The second test, HIgM, which detects human (H) IgM anti-F1, was developed in order to have another method for plague diagnosis. Its sensitivity was 83% (95% CI: 0.75–0.90) and its specificity about 100%.

Conclusion/Significance

The SIgT test is of importance for surveillance because it can detect Ig antibodies in a range of reservoir species. The HIgM test could facilitate the diagnosis of plague during outbreaks, particularly when only a single serum sample is available.

Plague is due to the bacterium Yersinia pestis. It is accidentally transmitted to humans by the bite of infected fleas. Currently, approximately 20 developing countries with very limited infrastructure are still affected. A plague case was defined according to clinical, epidemiological and biological features. Rapid diagnosis and surveillance of the disease are essential for its control. Indeed, the delay of treatment is often rapidly fatal for patients and outbreaks may occur. Bubo aspirate is the most appropriate specimen in case of bubonic plague, but its collection is not always feasible. The main current biological approaches for the diagnosis of human plague are F1 antigen detection, serology for antibody detection by ELISA and Y. pestis isolation. The biological diagnosis of plague remains a challenge because the clinical signs are not specific. In this study, we developed some simple, rapid and affordable tests able to detect specific plague antibodies. These tests can be used as alternative methods for plague diagnosis in the field and for plague surveillance.

Geographic distribution and ecological niche of plague in sub-Saharan Africa

BACKGROUND

Plague is a rapidly progressing, serious illness in humans that is likely to be fatal if not treated. It remains a public health threat, especially in sub-Saharan Africa. In spite of plague's highly focal nature, a thorough ecological understanding of the general distribution pattern of plague across sub-Saharan Africa has not been established to date. In this study, we used human plague data from sub-Saharan Africa for 1970-2007 in an ecological niche modeling framework to explore the potential geographic distribution of plague and its ecological requirements across Africa.

RESULTS

We predict a broad potential distributional area of plague occurrences across sub-Saharan Africa. General tests of model's transferability suggest that our model can anticipate the potential distribution of plague occurrences in Madagascar and northern Africa. However, generality and predictive ability tests using regional subsets of occurrence points demonstrate the models to be unable to predict independent occurrence points outside the training region accurately. Visualizations show plague to occur in diverse landscapes under wide ranges of environmental conditions.

CONCLUSION

We conclude that the typical focality of plague, observed in sub-Saharan Africa, is not related to fragmented and insular environmental conditions manifested at a coarse continental scale. However, our approach provides a foundation for testing hypotheses concerning focal distribution areas of plague and their links with historical and environmental factors.

Long-term persistence of virulent Yersinia pestis in soil

Plague is characterized by geographical foci from which it re-emerges after decades of silence, a fact currently explained by enzootic and epizootic cycles between plague-susceptible and plague-resistant rodents. To assess the potential role of soil in plague epidemiology, we experimentally investigated whether Yersinia pestis could persist alive and virulent in soil. Sterilized soil inoculated with virulent Y. pestis biotype Orientalis was regularly sampled for 40 weeks in duplicate. Each sample was observed by acridine orange staining and immunofluorescence using an anti-Y. pestis polyclonal antibody, and DNA was extracted for PCR amplification and sequencing of the Y. pestis ureD, caf1 and pla genes. All samples were inoculated onto selective agar, and samples from soil that had been incubated for 10, 60, 165, 210 and 280 days were also inoculated into each of two BALB/c female mice. The mouse experiment was performed in triplicate. Non-inoculated, sterilized soil samples were used as negative controls. Micro-organisms fluorescing orange and detected by immunofluorescence were identified as Y. pestis in all samples. They were recovered in pure agar cultures for up to 30 weeks but thereafter were contaminated with Pseudomonas spp. Soil that had been inoculated with Y. pestis proved to be fully virulent in mice, which died with Y. pestis septicaemia and multiple organ involvement. Negative control mice showed no signs of disease. These data indicate that Y. pestis biotype Orientalis can remain viable and fully virulent after 40 weeks in soil. This study is a first step on which to base further investigations of a potential telluric reservoir for Y. pestis, which could represent an alternative mechanism for the maintenance of plague foci.

Plague reappearance in Algeria after 50 years, 2003

An outbreak of plague occurred in the region of Oran, Algeria, from June to July 2003. Algeria had not reported this disease for >50 years. Eighteen bubonic cases were identified, and Yersinia pestis was isolated from 6 patients. Except for the index case-patient, all patients recovered. Targeted chemoprophylaxis, sanitation, and vector control played a crucial role in controlling the outbreak. Epidemiologic and biomolecular findings strongly suggested the existence of a local animal reservoir during this period, but its origin (resurgence or re-importation) could not be determined. This sudden and unexpected reemergence of plague, close to an important commercial seaport, is a textbook illustration of a public health event of international importance. It also demonstrates that the danger of plague reoccurrence is not limited to the currently indexed natural foci.

Emergency preparedness and public health systems lessons for developing countries

Low- and middle-income countries, where emerging diseases often make their debut, are also likely to bear the harshest consequences of a potential influenza pandemic. Yet public health systems in developing countries are underfunded, understaffed, and in many cases struggling to deal with the existing burden of disease. As a result, developed countries are beginning to expand assistance for emergency preparedness to the developing world. Given developing countries' weak infrastructure and many competing public health priorities, it is not clear how to best direct these resources. Evidence from the U.S. and other developed countries suggests that some investments in bioterror and pandemic emergency preparedness, although initially implemented as vertical programs, have the potential to strengthen the general public health infrastructure. This experience may hold some lessons for how global funds for emergency preparedness could be invested in developing countries to support struggling public health systems in responding to current health priorities as well as potential future public health threats.