Transboundary and Emerging Diseases最新文献

The H5N6 avian influenza virus (AIV) is constantly undergoing recombination and evolution with other subtypes of AIV, resulting in various types of recombinant H5N6 viruses. However, the risk to human public health of different recombinant types of H5N6 viruses remains unclear. Recently, two types of different recombinant H5N6 viruses were isolated from chickens. One of the viruses possessed six internal genes originating from H9N2, named A/Chicken/Hubei/112/2020 (H5N6) (abbreviated 112); the other virus possessed PB2, PB1, PA, and NP originating from H5N1, while the M and NS genes were derived from H9N2, named A/Chicken/Hubei/125/2020 (H5N6) (abbreviated 125). Here, we investigated the receptor binding properties, pathogenicity, and transmissibility of the two H5N6 AIVs. The results showed that 112 and 125 could bind α-2,3-linked sialic acid receptor (avian-like receptor) and α-2,6-linked sialic acid receptor (human-like receptor). However, 125 and 112 showed different pathogenicity in mice. Mice infected with 125 lost only a slight body weight and all survived, while mice infected with 112 lost weight rapidly and all died within a week of infection. Furthermore, in the transmission experiment, 125 could only transmit through direct contact, while 112 could transmit not only by direct contact but also by aerosol. The above results indicated that 112 exhibited enhanced pathogenicity and transmissibility compared to 125, suggesting that the H5N6 virus, whose internal genes were derived from H9N2, could pose a greater threat to human health. Therefore, continuous monitoring of different recombinant H5N6 viruses in poultry should be carried out to prevent their transmission to humans.

The African swine fever virus (ASFV) causes African swine fever (ASF), a highly lethal disease affecting domestic pigs and wild boars. Since its initial outbreak in October 2019 in Yeoncheon, Gyeonggi Province, ASF has continued to spread in South Korea. This study aimed to differentiate closely related ASFV strains through the analysis of the intergenic region (IGR) between I73R and I329L genes. In 2019, genetic analysis confirmed one IGR I type case and two IGR III type cases in Paju, followed by two more IGR III type cases in 2020. After a period of detecting only the IGR II type, IGR III type cases re-emerged in Pohang and Cheong-song in November and December 2023. Genetic analysis using B646L, CP204, B602L, and EP402R genes confirmed that the IGR III strains belong to genotype II and serogroup 8, similar to the Georgia/2007/1 strain but differing in IGR type. Since the first occurrence of ASF in wild boars in South Korea, we have continuously monitored the introduction and variation of ASFV. As a result, we reconfirmed the presence of the IGR III type ASFV in 2023, 3 years and 8 months later, in a different area from where it was last detected. This finding would not have been possible without the continuous monitoring of ASFV introduction and genetic variation. We emphasize the critical role of regular monitoring based on molecular markers and comprehensive genomic analysis in enhancing the effectiveness of ASFV control and prevention.

Geographical expansion and trans-continental transmission of the African swine fever virus (ASFV) pose a significant risk to the global swine industry due to its high impact on swine health and agro-economy. Several different modes of ASFV transmission make it difficult to predict and prevent ASFV introduction to the free area and its spread in the affected area. Indirect transmission through contaminated surfaces could be one of the possible routes to introduce ASFV to the United States due to its high resistance on environmental surfaces and the frequency of international movements. However, there is limited knowledge about environmental samples for ASFV surveillance, when compared to clinical samples from infected pigs. Therefore, the aim of this study was to develop methods for better detection of ASFV DNA in the presence of four different types of organic contaminants: soil, swine feces, feed dust, and their mixture. The presence of organic contaminants negatively affected the sensitivity of ASFV DNA detection. Centrifugation and filtration were crucial for ASFV detection in environmental samples with soil and mixture, whereas filtration reduced the sensitivity of ASFV DNA detection in samples from clean surfaces and swine feces- and feed dust-contaminated surfaces. Detection of ASFV was significantly improved when sampled by the sponge stick with DNA/RNA shield when compared to the cost-effective sampling strategy, the cotton gauze with phosphate-buffered saline. These findings highlight the effect of organic contaminants and the use of the nucleic acid stabilization buffer on ASFV diagnostic performance and provide important background for ASFV preparedness.

Bovine herpesvirus type-4 (BHV-4) belongs to the gamma-herpesvirus subfamily, and its association with reproductive disorders in dairy cows is controversial. In this study, 386 whole blood and reproductive swab samples from dairy cows across eight provinces in China were collected. BHV-4 antibody levels in the serum were determined via ELISA, while real-time fluorescent quantitative PCR (qPCR) was employed to detect the DNA of BHV-4, BHV-1, bovine viral diarrhea virus type-I (BVDV-1), and bovine viral diarrhea virus type-II (BVDV-2) in the samples. Additionally, the DNA content of BHV-4 in various tissues of cows and stillborn fetuses was assessed via qPCR. Breeding information for the participating cows was gathered through farmer interviews, and correlation analyses were conducted between the detection results and breeding information. The findings revealed a BHV-4 antibody positive rate of 57.8% and a nucleic acid positive rate of 36.3%. Chi-square analysis revealed a correlation between BHV-4 and BHV-1 infections. Among several pathogens associated with reproductive disorders, only BHV-4 was significantly correlated, whereas BHV-1, BVDV-1, and BVDV-2 were not correlated. Furthermore, the study revealed elevated BHV-4 DNA in the reproductive tracts of cows and stillborn fetuses. Histopathological sections revealed mucosal damage in the vaginal and uterine tissues of stillborn fetuses, a phenomenon not previously reported. In summary, our study provides novel insight into the correlation between BHV-4 and reproductive disorders and presents new evidence that supports the vertical transmission of BHV-4.

Bats represent natural reservoirs of several paramyxoviruses, raising concerns about the potential for these viruses to cause cross-species infections. In this study, we isolated two jeilongviruses belonging to the family Paramyxoviridae from oral swab samples of the Eastern bent-wing bat (Miniopterus fuliginosus) and Far Eastern myotis bat (Myotis bombinus) in Kagoshima Prefecture, Japan. Notably, this is the first report isolating bat paramyxoviruses in Japan. Genomic analyses revealed a high identity between Kagoshima isolates (PMV/Bat35 and PMV/Bat111) and jeilongvirus B16-40, previously isolated from a Schreiber’s bent-wing bat (Miniopterus schreibersii) in South Korea in 2016. PMV/Bat35 infected and replicated in a range of cell lines derived from different animal species, although the level of syncytium formation varied among cell lines. Animal experiments revealed that Syrian hamsters inoculated intranasally with PMV/Bat35 did not exhibit clinical symptoms or significant weight loss. Nevertheless, viral genes were detected in the lungs and tracheas of Syrian hamsters on 2- and 5-day postinfection (dpi). Importantly, neutralizing antibodies against PMV/Bat35 developed in hamsters on 14 dpi. These results suggest that bat jeilongviruses can cross the species barriers. Our findings highlight the critical importance of ongoing monitoring and characterization of viruses circulating in bat populations to assess the risk of zoonotic outbreaks.

Infectious porcine reproductive and respiratory syndrome virus (PRRSV) causes PRRS, but noninfectious PRRSV cannot. PCR and ELISA are commonly used for PRRSV detection but they cannot discriminate PRRSV infectivity. Virus isolation is a gold standard to determine virus infectivity. However, it is time-consuming. Therefore, we developed a propidium monoazide (PMA) qPCR assay for rapid and universal detection of infectious PRRSV in this study. After comparing the inactivation efficacies of distinct disinfectants, ultraviolet (UV) light, and heat, heat at 72°C for 15 min was determined as an effective strategy for PRRSV inactivation, which was confirmed by virus isolation and immunofluorescence assay (IFA) detection. In addition, PMA pretreatment parameters were optimized, including PMA concentration (5 μM), PMA binding time (25 min), PMA binding temperature (37°C), and photolysis time (25 min). The optimal concentration of primers and probes adapted from our previous study was redetermined. The optimized PMA-qPCR assay exhibited satisfied specificity, sensitivity, and reproducibility. Furthermore, the new PMA-qPCR was applied on the detection of 270 clinical samples (including 57 environmental feces, 177 lungs, 33 lymph nodes [LN], and 3 sera) and compared with previously developed qPCR. Eighty samples were qPCR positive, while only 63 samples were PMA-qPCR positive. No virus could be isolated in the 17 qPCR-positive but PMA-qPCR-negative clinical samples; meanwhile, PRRSV could be isolated in representative PMA-qPCR-positive samples, supporting that only live PRRSV isolates in distinct samples could be detected by this PMA-qPCR assay. In conclusion, this study provides the first PMA-qPCR assay for rapid and universal detection of infectious PRRSV, offering an alternative and effective method for PRRSV diagnosis, prevention, and control.

Livestock farming is an important part of Mali’s economy and a major source of income for the rural population especially women. One of the major constraints to this activity is high burden of animal disease, in particular peste des petits ruminants (PPR), which hinder the productivity of small ruminants and thus reduces the income of livestock farmers. This disease that has an effective vaccine is subjected to a worldwide eradication program. The aim of this study is therefore to develop risk maps and identify the disease’s risk factors to inform national vaccination strategy in Mali. This tool will help decisions-makers rationalize the limited resources available for disease control. A compilation of retrospective cases of PPR from 2011 to 2023 was used to generate risk maps using multivariable regression models and geographically weighted regression. Results show that the southern regions of Mali are more at risk than the northern. PRR cases occur more during rainy and hot dry seasons. Parameters such as railroads length, rainfall, and watering points were identified as risk factors for the spread of the disease. These results point out high priority areas during a risk-based vaccination campaign against PPR in Mali.

Ascertaining the feeding behavior of vectors is a key for understanding epidemiology of the infections they transmit. For some host–vector–parasite systems, this information is biased towards human and peridomestic habitats, frequently underestimating the likely role of wildlife. In addition, studies on vector interactions often focus on a one-to-one host–vector relationship, even though it is crucial to analyze how multiple vector species interact with multiple hosts. These biases particularly affect our knowledge of sandflies, the main vector of Leishmania spp. and various phleboviruses, that are rarely explored in non-peridomestic habitats and in the context of multiple interactions with various hosts. To reveal the multihost/multivector network involving phlebotomine sandflies in a semiarid and poorly populated area of Spain, we sampled the sandfly community close to avian nests by means of two trapping methods (Centers for Disease Control (CDC) and sticky traps) during 3 years and identified the blood-meal source of all engorged sandflies. We detected six phlebotomine species with Phlebotomus perniciosus, P. papatasi, and Sergentomyia minuta being the most abundant ones. We identified 13 blood source species, with humans being the most common one, followed by Coracias garrulus (European roller) and Sus scrofa (likely wild boar). Five of the six sandfly species fed largely on wild mammals, although, three also fed on wild birds. Phlebotomus sergenti only fed on birds based on this analysis. Phlebotomus papatasi and P. sergenti were common visitors of bird nests suggesting an endophagic behavior. A network analysis showed a highly-connected and poorly-specialized network wherein sandflies shared most of the blood source and showed an opportunistic feeding behavior with marked anthropophilia. Our results obtained close to avian nests show that sandfly populations are maintained by various wild animals, which will greatly complicate the management and control of the pathogens they transmit to humans and domestic animals.

Background: Although the rate of emerging infectious diseases that originate in wildlife has been increasing globally in recent decades, there is currently a lack of epidemiological data from wild animals.

Methodology: We used serology to determine prior exposure to foot-and-mouth disease virus (FMDV), Brucella spp., and Coxiella burnetii and used genetic testing to detect blood-borne parasitic infections in the genera Ehrlichia, Anaplasma, Theileria, and Babesia from wildlife in two national parks, Kruger National Park (KNP), South Africa, and Etosha National Park (ENP), Namibia. Serum and whole blood samples were obtained from free-roaming plains zebra (Equus quagga), greater kudu (Tragelaphus strepsiceros), impala (Aepyceros melampus), and blue wildebeest (Connochaetes taurinus). Risk factors (host species, sex, and sampling park) for infection with each pathogen were assessed, as well as the prevalence and distribution of co-occurring infections.

Results: In KNP 13/29 (45%; confidence interval [CI]: 26%–64%) kudus tested positive for FMD, but none of these reacted to SAT serotypes. For brucellosis, seropositive results were obtained for 3/29 (10%; CI: 2%–27%) kudu samples. Antibodies against C. burnetii were detected in 6/29 (21%; CI: 8%–40%) kudus, 14/21 (67%; CI: 43%–85%) impalas, and 18/39 (46%; CI: 30%–63%) zebras. A total of 28/28 kudus tested positive for Theileria spp. (100%; CI: 88%–100%) and 27/28 for Anaplasma/Ehrlichia spp. (96%; CI: 82%–100%), whereas 12/19 impalas (63%) and 2/39 zebra (5%) tested positive for Anaplasma centrale. In ENP, only 1/29 (3%; CI: 0%–18%) wildebeest samples tested positive for FMD. None of the samples tested positive for brucellosis, while C. burnetii antibodies were detected in 26/30 wildebeests (87%; CI: 69%–96%), 16/40 kudus (40%; CI: 25%–57%), and 26/26 plains zebras (100%; CI: 87%–100%). A total of 60% Anaplasma/Ehrlichia spp. and 35% Theileria/Babesia spp. in kudu and 37% wildebeest tested positive to Theileria sp. (sable), 30% to Babesia occultans, and 3%–7% to Anaplasma spp. The seroprevalence of Q fever was significantly higher in ENP, while Brucella spp., Anaplasma, Ehrlichia, Theileria, and Babesia species were significantly higher in KNP. Significant coinfections were also identified.

Conclusion: This work provided baseline serological and molecular data on 40+ pathogens in four wildlife species from two national parks in southern Africa.

The recent emergence of West Nile virus (WNV) and Usutu virus (USUV) in some European countries has triggered an increase in animal and human cases across Europe. Wild birds, serving as key reservoirs for WNV and USUV, often act as crucial indicators for the introduction and spread of these viruses. Currently, there is no durable large-scale monitoring for WNV in Belgium, and specific monitoring for USUV is lacking. In Flanders, passive WNV monitoring in birds has been in place for many years, while initial efforts to initiate active monitoring started in 2022. Here, we present the results of a limited study conducted during the vector seasons of 2022 and 2023 in Flemish bird populations to actively and passively monitor the prevalence of WNV and additionally assess the presence of USUV. Several real-time reverse transcription-PCR tests were employed for virus detection, revealing the absence of WNV-RNA during both vector seasons. Conversely, USUV-RNA was identified in 2022 through active surveillance, affecting two (5.5%) out of 36 birds (Corvus corone), and in passive surveillance, impacting eight (72.7%) out of 11 birds (Turdus merula [6] and Rhea pennata [2]). In 2023, active surveillance was more extensive and identified 16 (7.2%) USUV-RNA positive birds (Buteo buteo [1], T. merula [14] and Athene noctua [1]) out of 222 examined birds, while passive surveillance detected two (7.1%) positive birds (T. merula [1], and Larus marinus [1]) out of 28. Viral sequence information was obtained from seven USUV-positive birds using whole genome sequencing or Sanger sequencing. Phylogenetic analysis placed all identified strains within the Africa 3 lineage. This restricted WVN monitoring effort in Flanders did not reveal WNV presence, but found indications of an endemic USUV circulation in Belgium. It is crucial to intensify monitoring efforts for WNV in the coming years, considering its endemic status in several European countries and its expanding geographical range in northern Europe.