African Swine Fever Virus (ASFV) causes a deadly disease of pigs which spread through southeast Asia in 2019. We investigated one of the first outbreaks of ASFV in Lao Peoples Democratic Republic amongst smallholder villages of Thapangtong District, Savannakhet Province. In this study, two ASFV affected villages were compared to two unaffected villages. Evidence of ASFV-like clinical signs appeared in pig herds as early as May 2019, with median epidemic days on 1 and 18 June in the two villages, respectively. Using participatory epidemiology mapping techniques, we found statistically significant spatial clustering in both outbreaks (P < 0.001). Villagers reported known risk factors for ASFV transmission − such as free-ranging management systems and wild boar access − in all four villages. The villagers reported increased pig trader activity from Vietnam before the outbreaks; however, the survey did not determine a single outbreak source. The outbreak caused substantial household financial losses with an average of 9 pigs lost to the disease, and Monte Carlo analysis estimated this to be USD 215 per household. ASFV poses a significant threat to food and financial security in smallholder communities such as Thapangtong, where 40.6% of the district’s population are affected by poverty. This study shows ASFV management in the region will require increased local government resources, knowledge of informal trader activity and wild boar monitoring alongside education and support to address intra-village risk factors such as free-ranging, incorrect waste disposal and swill feeding.
Numerous studies have unsuccessfully tried to unravel the definitive host of the coccidian parasite Besnoitia besnoiti. Cattle infections by B. besnoiti cause a chronic and debilitating condition called bovine besnoitiosis that has emerged in Europe during the last two decades, mainly due to limitations in its control associated to the absence of vaccines and therapeutical tools. Although the exact transmission pathway of B. besnoiti is currently unknown, it is assumed that the parasite might have an indirect life cycle with a carnivore as definitive host. Current lack of studies in wildlife might underestimate the importance of free-living species in the epidemiology of B. besnoiti. Thus, the aim of the present study is to assess the presence of Besnoitia spp. in free-ranging mesocarnivores in Spain. DNA was searched by PCR on faeces collected from wild carnivores as a first approach to determine which species could be considered as potential definitive host candidates in further research. For this purpose, a total of 352 faecal samples from 12 free-living wild carnivore species belonging to the Canidae, Felidae, Herpestidae, Mustelidae, Procyonidae, and Viverridae families were collected in seven Spanish regions. PCR testing showed that Besnoitia spp. DNA was present in four faecal samples from red foxes collected in western Spain, an area with the greatest density of extensively reared cattle and associated to high incidence of bovine besnoitiosis in the country. To date, this is the first report of a Besnoitia besnoiti-like sequence (99.57% homology) from carnivore faeces in a worldwide context. Red foxes might contribute to the epidemiology of B. besnoiti, although further studies, mostly based on bioassay, would be needed to elucidate the accuracy and extent of these interesting findings.
African swine fever (ASF), is a serious global concern from an ecological and economic point of view. While it is well established that its main transmission routes comprise contact between infected and susceptible animals and transmission through contaminated carcasses, the specific mechanism leading to its long-term persistence is still not clear. Among others, a proposed mechanism involves the potential role of convalescent individuals, which would be able to shed the virus after the end of the acute infection. Using a spatially explicit, stochastic, individual-based model, we tested: 1) if ASF can persist when transmission occurs only through infected wild boars and infected carcasses; 2) if the animals that survive ASF can play a relevant role in increasing ASF persistence chances; 3) how hunting pressure can affect the ASF probability to persist. The scenario in which only direct and carcass-mediated transmission were contemplated had 52% probability of virus persistence 10 years after the initial outbreak. The inclusion of survivor-mediated transmission corresponded to slightly higher persistence probabilities (57%). ASF prevalence during the endemic phase was generally low, ranging 0.1-0.2%. The proportion of seropositive individuals gradually decreased with time and ranged 4.5 – 6.6%. Our results indicate that direct and carcass-mediated infection routes are sufficient to explain and justify the long-term persistence of ASF at low wild boar density and the ongoing geographic expansion of the disease front in the European continent. During the initial years of an ASF outbreak, hunting should be carefully evaluated as a management tool, in terms of potential benefits and negative side-effects, and combined with an intensive effort for the detection and removal of wild boar carcasses. During the endemic phase, further increasing hunting effort should not be considered as an effective strategy. Additional effort should be dedicated to finding and removing as many wild boar carcasses as possible.
Summary: This study evaluates through modeling the possible individual and combined effect of three populational parameters of pathogens (reproduction rate; rate of novelty emergence; and propagule size) on the colonization of new host species – putatively the most fundamental process leading to the emergence of new infectious diseases. The results are analyzed under the theoretical framework of the Stockholm Paradigm using IBM simulations to better understand the evolutionary dynamics of the pathogen population and the possible role of Ecological Fitting. The simulations suggest that all three parameters positively influence the success of colonization of new hosts by a novel parasite population but contrary to the prevailing belief, the rate of novelty emergence (e.g. mutations) is the least important factor. Maximization of all parameters result in a synergetic facilitation of the colonization and emulates the expected scenario for pathogenic microorganisms. The simulations also provide theoretical support for the retention of the capacity of fast-evolving lineages to retro-colonize their previous host species/lineage by ecological fitting. Capacity is, thus, much larger than we can anticipate. Hence, the results support the empirical observations that opportunity of encounter (i.e. the breakdown in mechanisms for ecological isolation) is a fundamental determinant to the emergence of new associations – especially Emergent Infectious Diseases - and the dynamics of host exploration, as observed in SARS-CoV-2. Insights on the dynamics of Emergent Infectious Diseases derived from the simulations and from the Stockholm Paradigm are discussed.
Ticks are involved in the transmission of various pathogens and some tick-borne diseases cause significant problems for the health of humans and livestock. Despite their obvious importance, the composition of viral communities in ticks, and their interactions with pathogens, is poorly understood, particularly in Eastern Europe that constitutes (via bird migrations for example) a major hub for animal-arthropod vectors exchanges. The aim of this study was first to describe the virome of Dermacentor sp., Rhipicephalus sp. and Haemaphysalis sp. ticks collected from poorly investigated regions of Romania (Iasi and Tulcea counties) located at the intersection of various biotopes, countries and routes of migrations. We then focused the study on viruses that could have potential relevance for human and animal health. More than 500 ticks were collected in 2019 from the environment and from small ruminants and analyzed by high-throughput transcriptome sequencing. Among the viral communities infecting Romanian ticks, viruses belonging to the Flaviviridae, Phenuiviridae and Nairoviridae families were identified and full genomes were derivedPhylogenetic analyses placed them in clades where mammalian isolates are found, suggesting that these viruses could constitute novel arboviruses. We also assessed the bacterial microbiome of the collected ticks. The characterization of these microbial communities increases the knowledge of the diversity of viruses in Eastern Europe and provide a basis for further studies on the relationship between ticks and tick-borne viruses.
Porcine Sapovirus (SaV) was first identified by electron microscopy in the United States in 1980 and has since been reported from both asymptomatic and diarrheic pigs usually in mixed infection with other enteric pathogens. SaV as the sole etiological agent of diarrhea in naturally infected pigs has not previously been reported in the United States. Here, we used four independent lines of evidence including metagenomics analysis, real-time RT-PCR (rRT-PCR), histopathology, and in situ hybridization to confirm porcine SaV genogroup III (GIII) as the sole cause of enteritis and diarrhea in pigs. A highly sensitive and specific rRT-PCR was established to detect porcine SaV GIII. Examination of 184 fecal samples from the outbreak farm showed that pigs with clinical diarrhea had significantly lower Ct values (15.9 ± 0.59) compared to clinically unaffected pigs (35.8 ± 0.71). Further survey of 336 fecal samples from different states in the United States demonstrated that samples from pigs with clinical diarrhea had a comparable positive rate (45.3%) with those from non-clinical pigs (43.1%). However, the SaV-positive pigs with clinical diarrhea had significantly higher viral loads (Ct = 26.0 ± 0.5) than those positive but clinically healthy pigs (Ct = 33.2 ± 0.9). Phylogenetic analysis of 20 field SaVs revealed that all belonged to SaV GIII and recombination analysis indicated that intra-genogroup recombination occurred within the field isolates of SaV GIII. These results suggest that porcine SaV GIII plays an important etiologic role in swine enteritis and diarrhea and rRT-PCR is a reliable method to detect porcine SaV. Our findings provide significant insights to better understand the epidemiology and pathogenicity of porcine SaV.
Porcine astroviruses (PoAstVs) have been reported globally and are divided into at least five distinct lineages (PoAstV1-PoAsV5). The primary objective of this study was to summarize the scientific literature about the frequency of detection, associated clinical presentations, and type of samples and diagnostic tools used for the detection of porcine astroviruses. The secondary objective was to summarize the body of knowledge about the causal role in disease of PoAstVs using the Bradford Hill framework. A search was conducted using Centre for Biosciences and Agriculture International (CABI), MEDLINE, American Association of Swine Veterinarians (AASV) Swine Information Library (SIL) abstracts, swine conferences including American College of Veterinary Pathologists (ACVP), and American Association of Veterinary Laboratory Diagnosticians (AAVLD). From 168 studies identified by the search, 29 studies were eligible. Results indicated that 69% (20/29) of the literature on PoAstVs has been published between 2011 and 2018. Of 29 papers, 52% were detection studies (15 of 29) and 48% (14 of 29) were case-control studies. Seventy-two percent (21 of 29) reported differential diagnosis and 10% (3 of 29) reported histologic lesions, out of which 67% (2 of 3) associated the detection of PoAstV3 with development of polioencephalomyelitis. PCR-based assays were the most common diagnostic tools. Keywords: Swine, Astrovirus, Scoping review, Bradford Hill, PoAstV detection
The hypothesis that feed ingredients could serve as vehicles for the transport and transmission of viral pathogens was first validated under laboratory conditions. To bridge the gap from the laboratory to the field, this current project tested whether three significant viruses of swine could survive in feed ingredients during long-distance commercial transport across the continental US. One-metric ton totes of soybean meal (organic and conventional) and complete feed were spiked with a 10 mL mixture of PRRSV 174, PEDV, and SVA and transported for 23 days in a commercial semi-trailer truck, crossing 29 states, and 10,183 km. Samples were tested for the presence of viral RNA by PCR, and for viable virus in soy-based samples by swine bioassay and in complete feed samples by natural feeding. Viable PRRSV, PEDV, and SVA were detected in both soy products and viable PEDV and SVA in complete feed. These results provide the first evidence that viral pathogens of pigs can survive in representative volumes of feed and feed ingredients during long-distance commercial transport across the continental US.
Rabies is a global viral zoonosis endemic to South Africa, resulting in fatal encephalitis in warm blooded animals, including humans. The loss of human lives and economic losses in rural areas through loss of livestock are substantial. A review was conducted of all confirmed rabies cases in South Africa from 1993 to 2019, with a total of 11 701 cases identified to species level to assess the wildlife plays in the epidemiology of rabies. A spatiotemporal cluster analysis using a discrete Poisson space-time probability model, accounting for underlying estimated dog and livestock densities, identified 13 significant clusters (p<0.05). These included four long-term clusters lasting more than 8 years in duration and seven short term clusters lasting less than 2 years, with the remaining two clusters being of intermediate length. Outside of these endemic clusters, wildlife outbreaks in the remainder of South Africa were often less than one and a half years in duration most likely due to the rapid decline of wildlife vectors, especially jackals associated with rabies infection. Domestic dogs accounted for 59.8% of cases, with domestic cats (3.2%), livestock (21.1%) and wildlife (15.8%) making up the remainder of the cases. Yellow mongoose (Cynictis penicillate) was the most frequently affected wildlife species, followed by bat-eared fox (Otocyon megalotis), black-backed jackal (Canis mesomelas), meerkat (Suricata suricatta) and aardwolf (Proteles cristatus). Rabies in wildlife species followed different spatial distributions: black-backed jackal cases were more common in the north-western parts of South Africa, yellow mongoose cases more frequent in central South Africa, and bat-eared fox and aardwolf cases were more frequent in southern and western South Africa. Clusters often spanned several provinces, showing the importance of coordinated rabies control campaigns across administrative boundaries, and high-risk areas were highlighted for rabies in South Africa.
Objectives: evaluate the Surveillance Program of Gestational and Congenital Toxoplasmosis. Methods: 424 pregnant women were interviewed regarding their knowledge of prevention measures in 2019. Secondary prevention measures were assessed on the results of anti-Toxoplasma gondii serological tests were collected from pregnant women, from 2015 to 2018. the tertiary prevention measures, we screened the babies of mothers who had recent suspected infections of T. gondii to verify the referrals to the reference service. Results: 45.5% (192/424) reported that they had received guidance from health professionals; 35.4% (68/192) changed their risk habits. The variables of schooling and age, having received prior guidance from health professionals and feline possession, proved to be significant when associated with the notions of preventive measures. 90.2% (17,423 / 19,319) of pregnant women had undergone serological tests to detect anti-T. gondii antibodies but there was an excess in requests for tests and medication and only 40.6% (26/64) of the children were referred to the referral hospital. Conclusions: the Program presents positive results regarding the performance of serological screening in prenatal care; however, the dissemination of knowledge about the prevention of toxoplasmosis and the request for tests need to be improved.
Atypical porcine pestivirus (APPV), which has been confirmed to be associated with congenital tremor (CT) in pigs, is a newly discovered porcine virus that has been found in the Americas, Europe, and Asia; however, no report of APPV in Japan has been published. We identified an APPV in the central nervous system of Japanese piglets with CT, and firstly determined and analyzed the complete genome sequence. Phylogenetic analysis using the complete genome nucleotide sequence of the Japanese APPV, named Anna/2020, and those of APPVs from the NCBI database showed that APPVs were divided into three genotypes (genotypes 1 to 3), and that Anna/2020 clustered with the genotype 3 APPV strains, but distantly branched from these strains. Pairwise complete coding region nucleotide sequence comparisons revealed that there was 94.0% to 99.7% sequence identity among the genotype 3 strains, while Anna/2020 showed 87.0% to 89.3% identity to those genotype 3 strains, suggesting that Anna/2020 represents a novel APPV lineage within genotype 3. Retrospective examinations using RT-PCR revealed one genotype 1 and two novel genotype 3 APPVs from pigs without CT, and that novel genotype 3 APPVs have been prevalent in Japan since at least 2007.
The aim of the present study was to evaluate the duration of protective immunity against Porcine epidemic diarrheoa virus (PEDV). To that, a two phases study was performed. In the first phase, 75 four-week-old pigs (group A) were orally inoculated (0 days post-inoculation; dpi) with a European PEDV G1b strain and 14 were kept as controls (group B). The second phase started five month later (154 dpi), when animals in group A were homologous challenged and animals in group B were challenged for first time. Clinical signs, viral shedding and immune responses were evaluated after each inoculation, including the determination of antibodies (ELISA and viral neutralisation test, IgA and IgG ELISPOTs using peripheral blood mononuclear cells and lymph node cells) and the frequency of interferon-gamma (IFN-γ) secreting cells. During the first phase, loose stools/liquid faeces were observed in all group A animals. Faecal shedding of PEDV occurred mostly during the first 14 days but, in some animals, persisted until 42 dpi. All inoculated animals seroconverted for specific-PEDV IgG and IgA, and for neutralizing antibodies (NA). At 154 dpi, 77% of pigs were still positive for NA. After that, the homologous challenge resulted in a booster for IgG, IgA, NA, as well as specific-PEDV IgG, IgA and IFN-γ secreting cells. In spite of that, PEDV was detected in faeces of all pigs from group A, indicating that the immune response did not prevent reinfection although the duration of the viral shedding and the total load of virus shed was significantly lower for previously challenged pigs (p<0.05). Taken together, the results indicated that, potentially, maintenance of PEDV infection within an endemic farm may occur by transmission to and from previously infected animals and also indicates that sterilising immunity is shorter than the productive life of pigs.
Leishmania donovani is the causative agent of historically anthroponotic visceral leishmaniasis (VL) on the Indian subcontinent (ISC). L. donovani is transmitted by the sand fly species Phlebotomus argentipes. Our collaborative group and others have shown that sand flies trapped outside in endemic villages have fed on cattle and dogs in addition to people. Domestic animals are reservoirs for L. donovani complex spp., particularly L. infantum, in other endemic areas. Multiple studies using quantitative PCR or serological detection methods have demonstrated that goats, cattle, rats and dogs were diagnostically positive for L. donovani infection or exposure in eastern Africa, Bangladesh, Nepal and India. There is a limited understanding of the extent to which L. donovani infection of domestic animals drives transmission to other animals or humans on the ISC. Evidence from other vector-borne disease elimination strategies indicated that emerging infections in domestic species hindered eradication. The predominant lesson learned from these other situations is that non-human reservoirs must be identified, controlled and/or prevented. Massive efforts are underway for VL elimination on the Indian subcontinent. Despite these herculean efforts, residual VL incidence persists. The specter of an animal reservoir complicating elimination efforts haunts the final push toward full VL control. Better understanding of L. donovani transmission on the Indian subcontinent and rigorous consideration of how non-human reservoirs alter VL ecology are critical to sustain elimination goals.
Current results do not provide conclusive evidence on the effect of BCG vaccination on COVID-19 alone or in combination with other factors. To address this limitation, in this study we used a citizen science initiative on the COVID-19 pandemic to collect data worldwide during October 2-30, 2020 (1,233 individuals) in a structured way for analyzing factors and characteristics of affected individuals in relation to BCG vaccination. For the first time, the results of our study suggested that vaccination with BCG may increase the risk for COVID-19 at certain age, particularly in individuals vaccinated at childhood. A reasonable explanation for this effect is the activation of certain innate immunity mechanisms associated with inflammatory reactions, which should be considered when analyzing the risks associated with this global pandemic. These factors should be considered when analyzing the risks associated with this global pandemic.
Level and duration of protective immunity against SARS-CoV-2 after primary infection is of crucial importance for preventive approaches. In order to provide evidence for the longevity of specific antibodies, we investigated the generation and maintenance of neutralizing antibodies of convalescent SARS-CoV-2-afflicted patients over a five month period post primary infection using an immunofluorescence assay, a commercial chemiluminescent immunoassay and an in-house enzyme-linked plaque-reduction neutralization assay. We present the successful application of an improved version of the plaque-reduction neutralization assay, which can be analyzed optometrically, significantly simplifying the interpretation of the results. Based on the results of the plaque-reduction neutralization assay, neutralizing antibodies were maintained in 85.3% of convalescent individuals without significant decay over five months. Furthermore, a positive correlation between severity of infection and neutralizing titer was shown. In conclusion, SARS-CoV-2-afflicted individuals have been proven to be able to establish and maintain neutralizing antibodies over a five months’ period after primary infection which allows to hope for long-lasting presumably protective humoral immunity after wild-type infection or even after vaccination.
African Swine Fever Virus (ASFV) is a highly contagious pathogen causing disease in pigs, commonly characterised by acute haemorrhagic fever. Prior to August 2018, African Swine Fever (ASF) had not been reported in Asia, but has since spread throughout China, Mongolia, Korea, Vietnam, Laos, Cambodia, Myanmar, the Philippines, Hong Kong, Indonesia, Timor-Leste and Papua New Guinea. Using data collated from reports of confirmed cases, we applied spatio-temporal analysis to describe ASFV spread throughout Asia, from 1 August 2018 (reported start date) to 31 December 2019. Analysis revealed a propagating epidemic of ASFV throughout Asia, with peaks corresponding to increased reports from China, Vietnam and Laos. Two clusters of reported outbreaks were found. During the epidemic, ASFV primarily spread from the North-East to the South-East: a larger, secondary cluster in the North-East represented earlier reports, whilst the smaller, primary cluster in the South-East was characterised by later reports. Significant differences in country-specific epidemics, morbidity, mortality and unit types were discovered, likely attributable to differences in prevention, surveillance and control measures. The initial number of outbreaks and enterprise size are likely predictors of the speed of spread and the effectiveness of ASFV stamping out procedures. Biosecurity methods, wild boar populations and the transportation of pigs and movement of infected fomites are discussed as likely risk factors for facilitating ASFV spread across Asia.
Newcastle disease (ND), caused by avian orthoavulavirus type-1 (NDV), is endemic in poultry in the Middle East causing continuing outbreaks in poultry populations despite efforts to vaccinate. In the past, genotype 2.XXI (former 2.VI) was present in poultry in Egypt but has been replaced by genotype 2.VII. We investigated whether virus evolution contributed to superseding, and focused on the antigenic sites within the Heamagglutinin-Neuramindase (HN) spike protein. Full length sequences of a NDV genotype 2.VII isolate currently circulating in Egypt was compared to a genotype 2.XXI isolate that was present as co-infection with vaccine type viruses (2.II) in an historical isolate of the year 2011. Amino acid differences in the HN glycoprotein for both 2.XXI and 2.VII viruses amounted to 11,7% and 11,9 % compared to LaSota vaccine type. However, mutations within the globular head (aa 126-570), bearing relevant antigenic sites, were underrepresented (aa divergence of 8,8% and 8,1 % compared to 22,4% and 25,6% within the fragment encompassing cytoplasmic tail, transmembrane part and stalk regions (aa 1-125) for genotypes 2.XXI and 2.VII, respectively. Nevertheless, reaction patterns of HN-specific monoclonal antibodies revealed differences between vaccine type viruses and genotype 2.XXI and 2.VII viruses for specific epitopes. Accordingly, compared to Egyptian vaccine type isolates and the LaSota vaccine reference strain, single aa substitutions in 6 of 10 described neutralizing epitopes were found within the attachment protein. However, the same alterations in neutralization sensitive epitopes were present in old genotype 2.XXI as well as in newly emerged genotype 2.VII isolates. In addition, isolates were indistinguishable by polyclonal chicken sera raised against different genotypes including vaccine viruses. These findings suggest, that factors other than antigenic differences within the HN-protein account for facilitating spread of genotype 2.VII while displacing genotype 2.XXI viruses in Egypt.
Avian influenza (AI) is a contagious disease of birds with zoonotic potential. AI virus (AIV) can infect most bird species, but clinical signs and mortality vary. Assessing the distribution and factors affecting AI incidence can direct targeted surveillance to areas at risk of disease outbreaks, or help identify disease hotspots or areas with inadequate surveillance. Using virus surveillance data from passive and active AIV wild bird surveillance, 20062020, we investigated the association between a range of landscape factors and game bird release and the presence of AIV. Furthermore, we assessed potential bias in the passive AIV surveillance data submitted by the public, via factors related to public accessibility. Lastly, we tested the AIV data for possible hot and cold spots within Denmark. The passive surveillance data was biased regarding accessibility to areas (distance to roads, cities and coast) compared to random locations within Denmark. We found significant effects of variables related to coast, wetlands and cities for the passive and active AIV surveillance data (P< 0.01), but found no significant effect of game bird release. We used these variables to predict the risk of AIV presence throughout Denmark, and found high-risk areas concentrated along the coast and fjords. For both passive and active surveillance data, low-risk clusters were mainly seen in Jutland and northern Zealand, whereas high-risk clusters were found in Jutland, Zealand, Funen and the southern Isles such as Lolland and Falster. Our results suggest that landscape affects AIV presence, as coastal areas and wetlands attract waterfowl and migrating birds and therefore might increase the potential for AIV transmission. These findings have enabled us to create risk maps of AIV incidence in wild birds and pinpoint high-risk clusters within Denmark. This will aid targeted surveillance efforts within Denmark and potentially aid in planning the location of future poultry farms.