Trends in the development of the epidemic process in salmonellosis caused by Salmonella typhimurium and Salmonella enteritidis

The dynamics and structure of the epidemic process of Salmonella infections among the population of Perm in 1983-1988 was studied and the results of evaluation of antibiotic resistance of the dominating Salmonella species analyzed. The study revealed that a decrease in salmonellosis morbidity caused by S. typhimurium was associated with a limited circulation of anthroponotic (antibiotic-resistant) variants of Salmonellae and a relative increase in the proportion of zoonotic (antibiotic-sensitive) strains. At the period of elevated morbidity this Salmonella infection affected mainly young children in cold months, whereas in recent years seasonal morbidity rises shifted to spring-summer and summer-autumn months, affecting older age groups of the population. The study also revealed that a rise in salmonellosis morbidity caused by S. enteritidis was due to increased circulation of zoonotic variants of Salmonellae. Changes in the epidemiological situation necessitate correction of the system of epidemiological surveillance on Salmonella infections with the emphasis on sanitation measures in stock-breeding farms with unfavorable epidemiological situation.     

Zoonotic (avian) influenza. Prognoses of pandemic and reality

Likelihood of a pandemic emergence in the near future was discussed. The majority of science-based arguments point to anthroponotic nature of future pandemic, which can be caused by return to circulation of H2N2 virus silently persisting in population from 1968 or in animals as part of various reassortants. Outbreaks of zoonotic (avian) influenza in humans emerged recently reflect natural epidemic manifestations of epizootic process which had become more intense due to specific social and natural conditions in densely populated countries of South-East Asia. This suggestion is confirmed by predominance of poultry workers between patients with avian influenza. Likelihood of pandemic influenza A virus emergence as a result of reassortation between human and avian influenza viruses is not high. Similarity of antigenic structure of human and animal influenza viruses points to their common roots, but yet humans remain the biological dead-end for reassortant viruses. Rationale for epidemiologic surveillance as well as for prophylactic and antiepidemic measures with respect to influenza A is obvious basing on anthroponotic nature of its causative agents. Although the likelihood of adaptation of animal influenza viruses to human organism and formation of anthroponotic mechanisms of transmission is small, epidemiological and, especially, epizootic surveillance for zoonotic influenza are essential.     

Zoonotic cryptosporidiosis

The widespread usages of molecular epidemiological tools have improved the understanding of cryptosporidiosis transmission. Much attention on zoonotic cryptosporidiosis is centered on Cryptosporidium parvum. Results of genotype surveys indicate that calves are the only major reservoir for C. parvum infections in humans. The widespread presence of human-adapted C. parvum, especially in developing countries, is revealed by recent subtyping and multilocus typing studies, which have also demonstrated the anthroponotic transmission of C. parvum subtypes shared by humans and cattle. Developing and industrialized countries differ significantly in disease burdens caused by zoonotic species and in the source of these parasites, with the former having far fewer human infections caused by C. parvum and little zoonotic transmission of this species. Exclusive anthroponotic transmission of seemingly zoonotic C. parvum subtypes was seen in Mid-Eastern countries. Other zoonotic Cryptosporidium spp. are also responsible for substantial numbers of human infections in developing countries, many of which are probably transmitted by anthroponotic pathways. The lower pathogenicity of some zoonotic species in some populations supports the occurrence of different clinical spectra of Cryptosporidium spp. in humans. The use of a new generation of molecular diagnostic tools is likely to produce a more complete picture of zoonotic cryptosporidiosis.     

Human vs. Animal Outbreaks of the 2009 Swine-Origin H1N1 Influenza A epidemic

The majority of emerging infectious diseases are zoonotic in origin, including recently emerging influenza viruses such as the 2009 swine-origin H1N1 influenza A epidemic. The epidemic that year affected both human and animal populations as it spread globally. In fact, before the end of 2009, 14 different countries reported H1N1 infected swine. In order to better understand the zoonotic nature of the epidemic and the relationship between human and animal disease surveillance data streams, we compared 2009 reports of H1N1 infection to define the temporal relationship between reported cases in animals and humans. Generally, human cases preceded animal cases at a country-level, supporting the potential of H1N1 infection to be a “reverse zoonosis”, and the value of integrating human and animal disease report data.     

Does Cryptosporidium parvum have a clonal population structure?

Cryptosporidiosis, the disease caused in humans by the opportunistic parasite Cryptosporidium parvum, is the result of zoonotic or anthroponotic transmission. Molecular characterization of different isolates from humans and other mammalian species has recently shown this species to be heterogeneous; this heterogeneity has been linked to the host of isolation, suggesting that the parasites causing zoonotic cryptosporidiosis and those propagated by anthroponotic transmission are genetically distinct. Here, Fatih Awad-El-Kariem provides an update on the taxonomic and epidemiological significance of these observations, and discusses evidence for and against the clonality hypothesis as a model to explain strain variation in this species.     

Plant‐based oral vaccines against zoonotic and non‐zoonotic diseases

The shared diseases between animals and humans are known as zoonotic diseases and spread infectious diseases among humans. Zoonotic diseases are not only a major burden to livestock industry but also threaten humans accounting for >60% cases of human illness. About 75% of emerging infectious diseases in humans have been reported to originate from zoonotic pathogens. Because antibiotics are frequently used to protect livestock from bacterial diseases, the development of antibiotic‐resistant strains of epidemic and zoonotic pathogens is now a major concern. Live attenuated and killed vaccines are the only option to control these infectious diseases and this approach has been used since 1890. However, major problems with this approach include high cost and injectable vaccines is impractical for >20 billion poultry animals or fish in aquaculture. Plants offer an attractive and affordable platform for vaccines against animal diseases because of their low cost, and they are free of attenuated pathogens and cold chain requirement. Therefore, several plant‐based vaccines against human and animals diseases have been developed recently that undergo clinical and regulatory approval. Plant‐based vaccines serve as ideal booster vaccines that could eliminate multiple boosters of attenuated bacteria or viruses, but requirement of injectable priming with adjuvant is a current limitation. So, new approaches like oral vaccines are needed to overcome this challenge. In this review, we discuss the progress made in plant‐based vaccines against zoonotic or other animal diseases and future challenges in advancing this field.     

A stakeholder-informed approach to the identification of criteria for the prioritization of zoonoses in Canada

Background

Zoonotic diseases account for over 60% of all communicable diseases causing illness in humans and 75% of recently emerging infectious diseases. As limited resources are available for the control and prevention of zoonotic diseases, it is necessary to prioritize diseases in order to direct resources into those with the greatest needs. The selection of criteria for prioritization has traditionally been on the basis of expert opinion; however, details of the methods used to identify criteria from expert opinion often are not published and a full range of criteria may not be captured by expert opinion.

Methodology/Principal Findings

This study used six focus groups to identify criteria for the prioritization of zoonotic diseases in Canada. Focus groups included people from the public, animal health professionals and human health professionals. A total of 59 criteria were identified for prioritizing zoonotic diseases. Human-related criteria accounted for the highest proportion of criteria identified (55%), followed by animal-related criteria (26%) then pathogen/disease-related criteria (19%).Similarities and differences were observed in the identification and scoring of criteria for disease prioritization between groups; the public groups were strongly influenced by the individual-level of disease burden, the responsibility of the scientific community in disease prioritization and the experiences of recent events while the professional groups were influenced by the societal- and population-level of disease burden and political and public pressure.

Conclusions/Significance

This was the first study to describe a mixed semi-quantitative and qualitative approach to deriving criteria for disease prioritization. This was also the first study to involve the opinion of the general public regarding disease prioritization. The number of criteria identified highlights the difficulty in prioritizing zoonotic diseases. The method presented in this paper has formulated a comprehensive list of criteria that can be used to inform future disease prioritization studies.     

Actual problems of creation of informational-analytical system for rapid control of epidemics of infectious diseases

Structure and modules of computer informational-analytical system "Electronic atlas of Russia" is presented, the object of mapping in this system is epidemiology of socially significant infectious diseases. Systemic information on processes of emergence and spread of socially significant infectious diseases (anthroponoses, zoonoses and sapronoses) in the population of Russian Federation is presented in the atlas. Detailed electronic maps of country territory filled with prognosis-analytical information created by using technological achievements of mathematic and computer modeling of epidemics and outbreaks of viral and bacterial infections are of particular interest. Atlas allows to objectively evaluate the pattern of infection spread, prepare prognoses of epidemic and outbreak developments taking into account the implementation of control measures (vaccination, prophylaxis, diagnostics and therapy) and evaluate their economic effectiveness.     

The leishmaniases as emerging and reemerging zoonoses

The 20 or so species of Leishmania which have been recorded as human infections are all either zoonotic, or have recent zoonotic origins. Their distribution is determined by that of their vector, their reservoir host, or both, so is dependent on precise environmental features. This concatenation of limiting factors leads to specific environmental requirements and focal distribution of zoonotic or anthroponotic sources. Human infection is dependent on the ecological relationship between human activity and reservoir systems. Examples are available of the emergence of leishmaniasis from the distant past to the present, and can be postulated for the future. These emergences have been provoked by the adoption of new, secondary reservoir hosts, the adoption of new vector species, transport of infection in humans or domestic animals, invasion by humans of zoonotic foci, and irruption of reservoir hosts beyond their normal range. The leishmaniases therefore present an excellent model for emerging disease in general, and for the generation of the principles governing emergence. The model is, however, limited by gaps in our knowledge, usually quantitative, sometimes qualitative, of the structure of reservoir systems.     

Emerging parasite zoonoses: the role of host-parasite relationship

Human-parasite relationships have played an essential role in the emergence or re-emergence of some parasitic diseases. These interactions are due to numerous causes. Some are linked to humans (immunodeficiencies due to AIDS among other causes, treatments, nosocomial contaminations, genetic predisposition), others concern the parasite (particular genotypes having modified their parasitic specificity). Several of these causes were predominant in the emergence of parasitoses such as cryptosporidiasis, microsporidioses or, to a certain point, pneumocystosis, the transmission of which has become zoonotic or even anthroponotic, inter-human. Re-emergent diseases (toxoplasmosis, leishmaniasis, giardiasis, strongyloidiasis, scabies) had already been described in human pathology, but their frequency or symptomatology have been drastically modified. In this case also, the unbalanced host-parasite relationship is largely responsible but it can not be dissociated from other causes, especially environmental and nutritional.     

Flying squirrels and their ectoparasites: disseminators of epidemic typhus

Information gathered during the past decade indicates that the eastern flying squirrel, Glaucomys volans, is a zoonotic reservoir of Rickettsia prowazekii - causative agent of louse-borne (epidemic) typhus. The sporadic cases o f typhus that have occurred in the USA in association with flying squirrels provide evidence that flying squirrels can transmit R. prowazekii infection to humons. Strains of R. prowazekii, isolated from flying squirrels multiply readily in human body lice, but flying squirrel lice, although readily infected, are very host specific and tend not to bite humans. It may be that the infection is spread to humans in infective ectoporasite faeces aerosolized when the flying squirrels groom themselves. As Joseph McDade emphasizes in this article, current concepts of typhus epidemiology and control must be re-evaluated to take into account this zoonotic aspect.     

The system of the epidemic process

An original social-ecological concept of the epidemic process has been constructed on the basis of using social ecology, systemic approach and the basic principles of cybernetics. According to this concept, the epidemic process is regarded as a biosocial, hierarchic, integral system providing for the reproduction of the species of human parasites. At a higher level of organization, the epidemic process is an epidemiological social-ecological system consisting of two interacting subsystems: the biological (epidemiological ecosystem) and the social (social and economic conditions of life of the society) subsystems where the biological subsystem plays the role of the governed object and the social acts as the internal regulator of these interactions. On the basis of this concept a rational structure of the system of epidemiological surveillance over infectious diseases has been proposed according to which each level of the structure of the epidemic process should be subject to adequate monitoring.     

Determining travel fluxes in epidemic areas

Infectious diseases attack humans from time to time and threaten the lives and survival of people all around the world. An important strategy to prevent the spatial spread of infectious diseases is to restrict population travel. With the reduction of the epidemic situation, when and where travel restrictions can be lifted, and how to organize orderly movement patterns become critical and fall within the scope of this study. We define a novel diffusion distance derived from the estimated mobility network, based on which we provide a general model to describe the spatiotemporal spread of infectious diseases with a random diffusion process and a deterministic drift process of the population. We consequently develop a multi-source data fusion method to determine the population flow in epidemic areas. In this method, we first select available subregions in epidemic areas, and then provide solutions to initiate new travel flux among these subregions. To verify our model and method, we analyze the multi-source data from mainland China and obtain a new travel flux triggering scheme in the selected 29 cities with the most active population movements in mainland China. The testable predictions in these selected cities show that reopening the borders in accordance with our proposed travel flux will not cause a second outbreak of COVID-19 in these cities. The finding provides a methodology of re-triggering travel flux during the weakening spread stage of the epidemic.     

Kuru: the old epidemic in a new mirror

The kuru epidemic lasted almost a century; it started in 1901-1902, reached epidemic proportions in the mid-1950s, and disappeared in the 1990s. Kuru is the prototype member of a group of disorders known as transmissible spongiform encephalopathies (TSEs) or prion diseases. Recent data on the genetics and pathogenesis of TSEs contribute to a better understanding of the documented kuru phenomena, and vice versa, observations made during the kuru epidemic are immensely helpful in understanding the epidemic of variant Creutzfeldt-Jakob disease that is currently developing in Europe. The major goal of this review is to identify and illustrate these points.     

Goats in the city: prevalence of <Emphasis Type="Italic">Giardia duodenalis</Emphasis> and <Emphasis Type="Italic">Cryptosporidium</Emphasis> spp. in extensively reared goats in northern India

Background

Various characteristics of goats mean they are highly suitable livestock for backyard rearing by people with limited resources. They are a popular livestock choice in India, where they are often kept to supplement an already scarce income. In these settings, hygiene and sanitation standards tend to be low, and weakens the interface between humans and animals, thus reducing the barrier between them and thereby increasing the likelihood that zoonotic and anthroponotic infections will occur.

Results

This study reports an investigation of the occurrence of Cryptosporidium spp. and Giardia duodenalis in goats being reared in different settings in urban and peri-urban areas in northern India, and addressed the zoonotic potential of these important protozoan parasites shed from goats living close to humans. The overall prevalence of G. duodenalis was 33.8 and 0.5% for Cryptosporidium spp.; the relatively low prevalence of cryptosporidiosis may reflect that most samples were derived from adult animals. The prevalence of G. duodenalis excretion was found to be similar to that reported in other studies. However, although other studies have reported a predominance of non-zoonotic Assemblage E in goats, in this study potentially zoonotic Assemblages predominated [Assemblage A (36%) and Assemblage B (32%)].

Conclusions

The results of this study indicate that in this area where goats and humans are living in close proximity, there may be sharing of intestinal parasites, which can be detrimental for both host species.

     

Conspicuous impacts of inconspicuous hosts on the Lyme disease epidemic

Emerging zoonotic pathogens are a constant threat to human health throughout the world. Control strategies to protect public health regularly fail, due in part to the tendency to focus on a single host species assumed to be the primary reservoir for a pathogen. Here, we present evidence that a diverse set of species can play an important role in determining disease risk to humans using Lyme disease as a model. Host-targeted public health strategies to control the Lyme disease epidemic in North America have focused on interrupting Borrelia burgdorferi sensu stricto (ss) transmission between blacklegged ticks and the putative dominant reservoir species, white-footed mice. However, B. burgdorferi ss infects more than a dozen vertebrate species, any of which could transmit the pathogen to feeding ticks and increase the density of infected ticks and Lyme disease risk. Using genetic and ecological data, we demonstrate that mice are neither the primary host for ticks nor the primary reservoir for B. burgdorferi ss, feeding 10% of all ticks and 25% of B. burgdorferi-infected ticks. Inconspicuous shrews feed 35% of all ticks and 55% of infected ticks. Because several important host species influence Lyme disease risk, interventions directed at a multiple host species will be required to control this epidemic.     

Multilocus genotyping of human Giardia isolates suggests limited zoonotic transmission and association between assemblage B and flatulence in children

Background

Giardia intestinalis is one of the most common diarrhea-related parasites in humans, where infection ranges from asymptomatic to acute or chronic disease. G. intestinalis consists of eight genetically distinct genotypes or assemblages, designated A–H, and assemblages A and B can infect humans. Giardiasis has been classified as a possible zoonotic disease but the role of animals in human disease transmission still needs to be proven. We tried to link different assemblages and sub-assemblages of G. intestinalis isolates from Swedish human patients to clinical symptoms and zoonotic transmission.

Methodology/Principal Findings

Multilocus sequence-based genotyping of 207 human Giardia isolates using three gene loci: ß-giardin, glutamate dehydrogenase (gdh), and triose phosphate isomerase (tpi) was combined with assemblage-specific tpi PCRs. This analysis identified 73 patients infected with assemblage A, 128 with assemblage B, and six with mixed assemblages A+B. Multilocus genotypes (MLGs) were easily determined for the assemblage A isolates, and most patients with this genotype had apparently been infected through anthroponotic transmission. However, we also found evidence of limited zoonotic transmission of Giardia in Sweden, since a few domestic human infections involved the same assemblage A MLGs previously reported in Swedish cats and ruminants. Assemblage B was detected more frequently than assemblage A and it was also more common in patients with suspected treatment failure. However, a large genetic variability made determination of assemblage B MLGs problematic. Correlation between symptoms and assemblages was found only for flatulence, which was significantly more common in children less than six years of age infected with assemblage B.

Conclusions/Significance

This study shows that certain assemblage A subtypes are potentially zoonotic and that flatulence is connected to assemblage B infections in young children. Determination of MLGs from assemblages A and B can be a valuable tool in outbreak situations and to help identify possible zoonotic transmission.     

The zoonotic,fish-borne liver flukes Clonorchis sinensis,Opisthorchis felineus and Opisthorchis viverrini

Clonorchis sinensis, Opisthorchis felineus and Opisthorchis viverrini are the three most important liver flukes involved in human health, infecting more than 45 million people worldwide. Both C. sinensis and O. viverrini, and possibly O. felineus, can induce human cholangiocarcinoma as well as inducing other hepatobiliary pathology. Although the life cycles of all three species are similar, only that of O. felineus in Europe remains predominantly zoonotic, while O. felineus in Asia and C. sinensis have a stronger mixture of zoonotic and anthroponotic components in their life cycles. Opisthorchis viverrini from the Mekong area of southeastern Asia is predominantly anthroponotic. Here we discuss the comparative epidemiology of these three taxa comparing in detail the use of first, second and final animal hosts, and consider the potential role of humans in spreading these pathogens. In addition we discuss the genetic structure of all three species in relation to potentially cryptic species complexes.     

Evidence supporting zoonotic transmission of Cryptosporidium in rural New South Wales

Cryptosporidium hominis, which has an anthroponotic transmission cycle and Cryptosporidium parvum, which is zoonotic, are the primary species of Cryptosporidium that infect humans. The present study identified the species/genotypes and subgenotypes of Cryptosporidium in 7 human and 15 cattle cases of sporadic cryptosporidiosis in rural western NSW during the period from November 2005 to January 2006. The species/genotype of isolates was determined by PCR sequence analysis of the 18S rRNA and C. parvum and C. hominis isolates were subgenotyped by sequence analysis of the GP60 gene. Fourteen of 15 cattle-derived isolates were identified as C. parvum and 1 as a C. bovis/C. parvum mixture. Of the human isolates, 4 were C. parvum and 3 were C. hominis. Two different subgenotypes were identified with the human C. hominis isolates and six different subgenotypes were identified within the C. parvum species from humans and cattle. All four of the C. parvum subtypes found in humans were also found in the cattle, indicating that zoonotic transmission may be an important contributor to sporadic human cases cryptosporidiosis in rural NSW.