Selection of Monitoring points for the Number and Infectivity of the Main Vectors of West Nile Virus in the Volgograd Region

Relevance. Since 1999, the incidence of West Nile fever has been recorded in the Volgograd region. The main vectors of West Nile virus in Russia are Cx mosquitoes. pipiens L. and Cx. modestus Fic. An objective assessment of the entomological situation and infection rate of these species within the framework of epidemiological surveillance of West Nile fever is possible only in biotopes with sufficiently high numbers of mosquitoes; therefore, the choice of sampling points is an urgent task. Purpose of the study. Analysis of the West Nile virus main vectors - mosquitoes Cx. pipiens L. and Cx. modestus Fic. average number, occurrence and infection rate at the various open biotopes of the Volgograd region to justify the choice of optimal points for entomological monitoring. Materials and methods. The catching and accounting of the mosquitoes’ number was carried out in 2015–2019 from May to August in the third decade of each month in a floodplain forest, at a personal plot, a summer cottage and on bank of water body. To catch mosquitoes, automatic traps Mosquito Magnet Executive and LovKom-1 were used. The accounting unit was the number of mosquitoes collected in both traps per trap-night. The average number, the index of occurrence and infection rate were determined by generally accepted methods. Detection of West Nile virus RNA in samples of mosquito pool suspensions was performed by RT-PCR using the AmpliSense WNV-FL reagent kit. The results were statistically processed using Microsoft Excel 2016 (Microsoft Corporation, USA). Results. In the 2015-2019 period, 17468 mosquitoes of the genus Culex: 8258 species – Cx. pipiens L., 9210 species – Cx. modestus Fic. were collected in over than 80 trap nights at the selected stationary points of the Volgograd region. Average number of Cx. pipiens L. was: in the floodplain forest – 4.6 individuals per 1 trap-night; at the personal plot – 183.9; at the summer cottage – 30.2; on the bank of water body – 194.3. Average number of Cx. modestus Fic. was: in the floodplain forest – 5.2 individuals per 1 trapnight; at the personal plot – 8.3; at the summer cottage – 2.5;on the bank of water body – 444.6. Occurrence index Cx. pipiens L. was highon the bank of water body and at the personal plot (47.1% and 44.5%, respectively), much lower – at the summer cottage (7.3%) and in the floodplain forest (1.1%). Level of WNV infection among Cx. pipiens L.on a personal plot was 5.4%, on a summer cottage – 3.6%,on the bank of water body – 2.2%. No infected samples were found among Cx. pipiens L. collected from the floodplain forest. WNV RNA in samples from mosquitoes Cx. modestus Fic. found only in individuals caughton the bank of water body. Their infection rate was 1.2%. Discussion. Ecological plasticity of Cx. pipiens L. mosquitoes allows them to live in settlements and near water bodies. Mosquitoes of the species Cx. modestus Fic. do not fly away from ponds, breeding places. Conclusion. High numbers and occurrence of the Cx. pipiens L. mosquitoes were observed at a personal plot within the city andon the bank of water body, Cx. modestus Fic. –on the bank of water body. WNV RNA positive samples were detected from mosquitoes collected at the personal plot, the summer cottage andon the bank of water body. To monitor the number and infection rate among Cx. pipiens L., points of registration and sampling should be placed in open stationson personal plots in settlements, banks of water bodies and summer cottages. We recommend to carry entomological monitoring for Cx. modestus Fic. out onlyon the banks of water bodies along the water's edge in reed thickets. The placement of the main WNV vectors number and infection rate monitoring points in the floodplain forest is not advisable.

West Nile Fever Virus Infection in Horses in São Paulo State, Brazil

Background: The West Nile virus (WNV) antibodies were reported in Brazil in the serum samples taken from horses and birds in the Midwest region and Paraíba state in 2008 and 2013, respectively. In 2014, the first human case was confirmed in a rural worker in the state of Piauí and, in 2018, the virus was isolated from the central nervous system of a horse with nervous symptoms in the state of Espírito Santo. The virus is a member of the Flaviviridae family of the genus Flavivirus (neurotropic), infecting several mammalian species, with humans and horses being the most susceptible. Approximately 35% of horses develop clinical signs, thus they are considered the best sentinels for this disease. The aim of this case report is to describe the first confirmed cases of West Nile Fever (WNF) in two horses in the state of São Paulo.Cases: Two horses with neurological symptoms were treated at the Veterinary Hospital of Cruzeiro do Sul University (São Paulo, SP), in 2019. Both horses came from neighboring regions that have a large Atlantic Forest preservation area and are also routes for migratory birds, known to be competent hosts for transmitting the West Nile Fever virus, such as the swallow, the falcon and the hawk. The first one had symptoms, such as weakness and sporadic seizures; however, after recovering, it was hospitalized a few days later due to kidney failure and laminitis. The second one showed incoordination, pelvic limb weakness, and was walking in circles, evolving to seizures. Both animals were euthanized, and their central nervous system samples and total blood samples were tested for rabies, herpes virus, and WNV; the first 2 tests showed negative results. Ribonucleic acids (RNA) were extracted from erythrocytes using the polymerase chain reaction (PCR) technique in-house. The WNV-specific reverse transcription-polymerase chain reaction amplification products were obtained using the nested PCR-multiplex PCR combination.Discussion: Since the 1940s, several WNF outbreaks have been reported around the world (Africa, Europe, Asia and Middle East). In the 2000s, the USA had the most amount of WNF cases reported; cases started being reported in Central and South America in the following years. The virus was identified for the first time in Brazil in 2014. Since then, our country is a route for migratory birds, with many states still having forests, several arboviruses are found such as WNF, which could become a public health problem. Both horses in the present study showed neurological signs and the horse that recovered had renal failure. Such signs are inconclusive, however, similar to those that occur in humans infected by the virus in its neurotropic form. The emergence of new diseases is an important aspect of public health. The literature is vast regarding the description of the pathogenesis, clinical signs, diagnosis, viral persistence and sequelae of WNF in humans, however, it is scarce regarding the viral persistence and sequelae of the disease in horses. Future studies are needed to understand the post-infection period in horses, as they are the most sensitive animals along with humans to this virus. Here, we report the first confirmed cases of WNF in the city of São Paulo to bring awareness about considering this disease while diagnosing horses with nervous system disorders.Keywords: encephalitis, horses, flavivirus, mosquito.Título: Infecção pelo vírus da Febre do Nilo Ocidental em equinos no Estado de São PauloDescritores: encefalite, equinos, flavivírus, mosquito.

Global Seroprevalence of West Nile Virus in Horses of Morocco

West Nile Fever (WNF) is a viral emerging mosquito-borne disease causing mortality and morbidity with varying severity (from mild fever to severe neuroinvasive disease) among human and animal populations in many parts of the world. The current study aimed to confirm the virus circulation and assess the disease seroprevalence in horses of Morocco. A sample of 1171 healthy non-vaccinated (against-WNF) horses, taken from 11 (out of 12) regions of the country during July-December 2016, was primarily tested using competitive ELISA assay (cELISA). All cELISA-reactive positive and doubtful sera (n= 269) were further tested by virus neutralization test (VNT). The results of cELISA test revealed an overall WNF seroprevalence in 21.8% (255/1171) of sampled horses. This rate decreased to 18.8% (220/1171) after the confirmation of VNT. The WNF seroprevalence in the current study varied significantly by age, gender, and breed of the tested horses. Indeed, the higher seropositivity rates were found in the oldest (27.7%), female (22.0%), and saddle (32.1%) horses. However, the origin of animals did not show any significant effect on the West Nile virus infection. The obtained results of the present study, therefore, provided serological and epidemiological evidence of the endemicity of the WNV in horse populations of Morocco.

West nile fever case in neurological practice

West Nile fever is a zoonotic arbovirus mosquito- and tick-borne infection, which occurs in humans in the form of an acute febrile illness with symptoms of general intoxication, in severe cases – with the central nervous system damage. West Nile virus belongs to the Flaviviridae family.After the start of Russians’ mass tourism to tropical and subtropical regions, number of cases of the disease in Russia has increased, especially in the south, where the virus is more viable. The infection mainly affects birds but also people and many mammals (bats, cats, dogs, skunks, squirrels, rabbits, etc.), which become infected after the bite of a mosquito of the genus Culex (Culex pipiens) carrying the disease, ixodid or argas mite. A clinical case of hemorrhagic stroke caused by West Nile fever is presented in the article.

West Nile fever in Volgograd Oblast: features of the epidemic process’s manifestations at the present stage

Objective: To study the regional features of the West Nile fever (WNF) epidemic process manifestations using the example of the territory with stable and long-term pathogen circulation (Volgograd Oblast).Materials and Methods: We used the data of the Reference Center for monitoring the WNF pathogen based on the Volgograd Research Anti-Plague Institute of Rospotrebnadzor over 1999–2021. The main method is a comprehensive epidemiological method.Results: The long-term changes in the WNF incidence in Volgograd Oblast is characterized by a cyclical nature with an interval of 1–8 years and a tendency to decrease. The maximum risk of infection occurs in August (58.8%), but there is an increase in the number of cases in September. The average duration of the epidemic season is 8.4 weeks. Case fatality rate is at the level of 4.3%; the prevalence of the number of deaths in the group of 70 years and older (75%), as well as among men (63.6%) has been established. The greatest contribution to the incidence rate is made by the age group of 60 years and older (37.7%). Features of the clinical presentation include the dominance of forms without damage to the central nervous system (91.1%) and moderate clinical course (72.3%). The prevalence of the urban population among the infected was noted (85.5%).Conclusion: A comparative analysis of the clinical and epidemiological WNF manifestations in Volgograd Oblast, territories with a stable circulation of the pathogen (Astrakhan and Rostov Oblasts) and, in overall, the Russian Federation, established differences in the duration of cyclical fluctuations in incidence, seasonality (Rostov Oblast), age structure of incidence (Astrakhan Oblast), distribution of cases by the severity of the clinical course, the site of the alleged infection and social status.

Results of epizootic monitoring of natural foci of particularly dangerous infections common to humans and animals in Rostov Oblast

Objective: To analyze the results of epizootic monitoring of natural foci of particularly dangerous infections common to humans and animals in Rostov Oblast to establish their activity.Materials and Methods: The data of epizootic monitoring conducted by zoologists; the results of laboratory research of field material obtained in natural foci of infectious diseases. Descriptive, zoological, genetic, serological methods, and retrospective epidemiological analysis were used.Results: The results of the conducted epizootic monitoring showed the presence in Rostov Oblast of natural foci of particularly dangerous infectious diseases common to humans and animals. While the natural focus of the plague is in a depressed state and does not show activity, in the foci of tularemia, West Nile fever (WNF), Crimean hemorrhagic fever (CHF), ixodic tick-borne borreliosis (ITB), hemorrhagic fever with renal syndrome (HFRS), Q fever, Batai fever, California serogroups, Syndbis revealed the antigens of these pathogens in biological material obtained from small mammals and blood-sucking insects, which indicates the epizootic activity of these foci. In the natural foci of WNF, CHF, ITB, HFRS, cases of these disease among the population were recorded, which confirms the epidemic activity of these foci.Conclusion: The obtained results of epizootic monitoring over the period from 2008 to 2020 emphasize the relevance and necessity of continuing these studies in natural foci in Rostov Oblast.

Effect of the natural and climatic factors on epidemiological situation related to natural focal infections

This article is dedicated to the analysis and generalization of the Russian and foreign research results on natural and climatic factors effect on the intensity of epidemic process manifestations and the natural focal infections pathogens vectors vital activity which are the most widespread in the Russian Federation. Over the past seven years tick-borne infections have been accounting for more than 50 per cent in the natural focal diseases general nosological structure. Among the diseases of this group Lyme borreliosis leads in prevalence and frequency of cases identification. Tick-borne viral encephalitis is still a serious danger for national health. Crimean-Congo hemorrhagic fever epidemiological situation remains unfavorable in the south of the European part of Russia. In addition to the annual patients identification, the demonstrable trend of shifting and expansion of the pathogen’s area in a northerly direction was established. It creates a risk for the spread of the Crimean-Congo hemorrhagic fever virus outside the southern regions of the country. High incidence of the dangerous vector-borne infection — West Nile fever — with the involvement of new subjects in the epidemic process and the emergence of local cases of infection in previously non-endemic territories is registered. Expansion of hemorrhagic fever with renal syndrome natural foci borders, which is the most widespread natural focal zoonosis of viral etiology in the Russian Federation and is the second by the frequency of patients identification after tick-borne infections, is noted. Research data for the dependence of the carriers pathogens number and the dynamics of the natural focal infections incidence on the values of climatic factors, confirmed using various methods of mathematical statistics (time-series analysis, autoregression integrated moving average, logistic regression, correlation analysis, one-way analysis of variance and other) were systematized. It was found that the temperature and humidity of the air and soil, the amount of precipitation, the height of the snow cover are the common abiotic factors for all of investigated infections. The values of these factors can be used for the subsequent epidemiological forecast. The further study of relationship between the incidence rate of the population, the number of arthropod vectors and small mammals with indicators of soil moisture and temperature at different depths, hydrothermal coefficient, normalized relative vegetation index, accumulated values of temperature and precipitation, as well as similar studies on other actual natural focal infections in the Russian Federation will be very promising.

Assessing the introduction risk of vector-borne animal diseases for the Netherlands using MINTRISK: A Model for INTegrated RISK assessment

To evaluate and compare the risk of emerging vector-borne diseases (VBDs), a Model for INTegrated RISK assessment, MINTRISK, was developed to assess the introduction risk of VBDs for new regions in an objective, transparent and repeatable manner. MINTRISK is a web-based calculation tool, that provides semi-quantitative risk scores that can be used for prioritization purposes. Input into MINTRISK is entered by answering questions regarding entry, transmission, establishment, spread, persistence and impact of a selected VBD. Answers can be chosen from qualitative answer categories with accompanying quantitative explanation to ensure consistent answering. The quantitative information is subsequently used as input for the model calculations to estimate the risk for each individual step in the model and for the summarizing output values (rate of introduction; epidemic size; overall risk). The risk assessor can indicate his uncertainty on each answer, and this is accounted for by Monte Carlo simulation. MINTRISK was used to assess the risk of four VBDs (African horse sickness, epizootic haemorrhagic disease, Rift Valley fever, and West Nile fever) for the Netherlands with the aim to prioritise these diseases for preparedness. Results indicated that the overall risk estimate was very high for all evaluated diseases but epizootic haemorrhagic disease. Uncertainty intervals were, however, wide limiting the options for ranking of the diseases. Risk profiles of the VBDs differed. Whereas all diseases were estimated to have a very high economic impact once introduced, the estimated introduction rates differed from low for Rift Valley fever and epizootic haemorrhagic disease to moderate for African horse sickness and very high for West Nile fever. Entry of infected mosquitoes on board of aircraft was deemed the most likely route of introduction for West Nile fever into the Netherlands, followed by entry of infected migratory birds.