|SHORT RESEARCH COMMUNICATION
|Year : 2018 | Volume
| Issue : 4 | Page : 324-326
Preliminary serological investigation of Rift Valley fever in Poland
BA Bazanow1, D Stygar2, E Romuk3, B Skrzep-Poloczek2, J Pacoń4, Ł Gadzała5, M Welz6, JT Pawęska7
1 Department of Pathology, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland
2 Department of Physiology, School of Medicine with Dentistry Division in Zabrze, Medical University of Silesia, Katowice, Poland
3 Department of Biochemistry, School of Medicine with Dentistry Division in Zabrze, Medical University of Silesia, Katowice, Poland
4 Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland
5 Department of Pathology, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Wroclaw; Private Veterinary Practice “NA ASNYKA”, Tarnów, Poland
6 Voivodeship Veterinary Inspectorate, Krosno, South Africa
7 Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
|Date of Submission||24-Jul-2018|
|Date of Acceptance||28-Aug-2018|
|Date of Web Publication||18-Apr-2019|
B A Bazanow
Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Wroclaw
Source of Support: None, Conflict of Interest: None
Keywords: Cattle; mosquitoes; Poland; Rift Valley fever virus
|How to cite this article:|
Bazanow B A, Stygar D, Romuk E, Skrzep-Poloczek B, Pacoń J, Gadzała &, Welz M, Pawęska J T. Preliminary serological investigation of Rift Valley fever in Poland. J Vector Borne Dis 2018;55:324-6
|How to cite this URL:|
Bazanow B A, Stygar D, Romuk E, Skrzep-Poloczek B, Pacoń J, Gadzała &, Welz M, Pawęska J T. Preliminary serological investigation of Rift Valley fever in Poland. J Vector Borne Dis [serial online] 2018 [cited 2019 Nov 19];55:324-6. Available from: http://www.jvbd.org/text.asp?2018/55/4/324/256570
Rift Valley fever (RVF) is a mosquito-borne zoonotic viral disease affecting primarily domestic and wild ruminants, camels and humans,. The causative agent of RVF, the RVF virus (RVFV), has the capacity to cause large-scale severe outbreaks in animal and human populations, and to cross significant natural barriers, as exemplified by the virus' spread over Indian Ocean, Sahara Desert, and Red Sea in the past three decades. New-born lambs and kids are extremely susceptible to infection with RVFV, with mortality exceeding 90% in animals less than a week old. Infected pregnant ruminants may abort at any stage of gestation, with abortion rates ranging from 15 to 100%. Infection with RVFV in human results in different disease syndromes, ranging from non-fatal, febrile illness to fatal haemorrhage and/or encephalitis. Some patients develop ocular disease. RVFV is transmitted through the bites of numerous species of mosquitoes (especially the Aedes or Culex genera) and through contact with infective tissues. The disease has serious socio-economic impact on people's livelihoods, food security, trade of animals or animal products and on human health,. The recent renewed interest in RVFV as a significant veterinary and public health threat is due to numerous reasons, including a limited understanding of the vectorial, host, ecological, climatic and anthropogenic factors responsible for the cryptic transmission of the virus during long inter-epidemic periods and the re-emergence of massive RVF diseases in endemic regions or emergence of the disease in areas previously free from the virus. There is also no licensed vaccines or chemotherapeutics for immunisation and treatment in human subjects. Presently, RVFV is widespread in Africa and has recently spread to the Arabian Peninsula and Indian Ocean,. According to some authors, the probability of introduction and large-scale spread of RVF in Europe is very low. However, localised disease outbreaks may potentially occur in areas where competent vectors and large population of ruminants exist. Therefore, most RVF-free countries take strict measures to detect the emergence of a new disease and prevent its spread,,,. Risk assessment conducted by the European Food Safety Authority (EFSA), concludes that RVFV constitutes a permanent threat to the Mediterranean region, consequently also to European Union (EU) neighbouring countries. RVF is a notifiable disease in the EU and the measures to prevent its introduction and control are laid down in Council Directive 92/119. Classical disease control methods, like active surveillance, epidemiological investigation, tracing and stamping out of infected herds, as well as designation of protection and surveillance zones are used as control and eradication measures. Additionally, strengthened import controls are applied in RVFV-free countries. The ability of RVFV to spread over distant geographic regions and to survive in a range of bioclimatic environments has raised a concern about its potential introduction into North America and Europe.
The goal of this study was to assess the epidemiological situation of RVFV infection in cattle in Poland. This is important due to the presence of competent vectors, which would favour RVF introduction. This study was the first major serosurvey for RVFV infection in Poland and, to the best of our knowledge, in Europe.
Banked bovine sera (n = 973), collected from animals of different age, sex and breed during routine screening for tuberculosis and bovine leukaemia in 2012–13 (n = 592) and in 2018 (n = 381) were used. In 2012–13 sera were collected, from animals residing mostly on small farms (one or few cows) located in southern and eastern macro-regions, Poland [Table 1]. In 2018 sera were obtained from all over the country [Figure 1]. Serum samples collected in 2012–13 were tested by the serum neutralisation test (SNT) as described previously. The titre was expressed as the reciprocal of the serum dilution that in hibited ≥75% of viral cytopathic effect. A serum sample was considered seropositive, if it had a titre of ≥log10 0.6, equivalent to a serum dilution ≥1 : 4. Bovine sera collected in 2018 were all tested by commercially available RVF enzyme-linked immunosorbent assay (ELISA) for the detection of anti-RVF antibodies in ruminant serum or plasma (ID Screen® Rift Valley Fever Competition Multi-species, IDvet Innovative Diagnostics, Grabeles, France). The IDvet RVF ELISA was performed as per the manufacturer's instructions. The ELISA absorbance readings of test samples (S) were converted into percentage competition (PC) of internal negative control sample (N), using the following formula: S/N × 100. A value of PC ≤ 40% was considered to be positive. Irrespective of the age, sex and geographic origin, all 973 serum samples tested were negative for IgG antibodies to RVFV [Table 1].
|Figure 1: The number of sera collected in 2018 and 2012–13 (indicated in parentheses) in different macro-regions of Poland, and the geographical distribution of mosquito species.|
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|Table 1: RVFV seropositivity in different regions of Poland; and age and sex of cattle|
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Owing to the severity of RVFV infection and high socioeconomic impacts, the virus is listed as one of the major zoonotic threats. During the past two decades, RVF has emerged in previously RVFV-free geographic regions. Further expansion of the geographical range of RVFV is likely, therefore, serosurveys and vector biosurveillance aiming at monitoring of the virus' activity are highly recommended,,, and should be regularly conducted as a part of a control strategy to protect Europe against RVF. The risk for Poland is real, due to the presence of competent mosquito species and climatic conditions which potentially are conducive for survival of RVF mosquito vectors, and consequently for establishing RVFV endemicity. Moreover, ongoing climate change might further create favourable conditions for new mosquito species and increase the possibility of virus introduction into the country. About 47 mosquito species occur in Poland, of which 12 are of medical importance, including nine, which have vector potential for transmitting RVFV. Aedes vexans, Ochlerotatus caspius, O. detritus, Culex pipiens, Cx. theileri, Cx. perexiguus, Cx. antennatus, Cx. tritaeniorhynchus and Ae. albopictus are main RVFV vectors in Poland. Most of them are widely present in the Mediterranean Basin and in the Nile Delta but some species (Cx. pipiens, Ae. vexans) commonly occur in Poland [Figure 1]. Additionally, O. detritus (Ae. detritus), a species which is gradually increasing its extent, has been reported in northwest Poland (Szczecin). Passive transportation of infected mosquitoes in boats or planes travelling from Africa is one of the most probable scenarios of disease importation into Europe. The main risk is, however, uncontrolled livestock trade from endemic to non-endemic areas associated with growing human populations and the increased demand for meat. Admittedly in the European Union, such animal transportation is forbidden, but illegal and unknown ruminant importations probably occur between the Middle East and central Europe, and between northern Africa and southern Europe.
Furthermore, introduction could occur through the importation of viraemic wildlife species or zoo animals. It has been proposed that even a single infected person or animal that enters a naive country might be sufficient to initiate an outbreak. With increasing climate change, people migration and animal trade, the risk of introduction of new diseases or even the reappearance of previously eradicated diseases increases dramatically. In 2014–17, African swine fever virus was confirmed in wild boars and domestic pigs in Poland (748 and 104 cases, respectively). Also, results of a recent study indicates activity of exotic viruses like West Nile virus (WNV) or Usutu virus (USUV) in Poland. In this context, the potential for outbreaks caused by viruses currently not endemic to Poland should always be a consideration. Implementation of an active monitoring programme to characterise the bionomics of RVFV vectors, in order to develop RVFV risk introduction and models of its spread, would contribute to the improvement of disease surveillance and provide more efficient decision-making tools. Considering the zoonotic nature, public health importance and the presence of competent vectors, it was reasonable to assess the seroprevalence of RVF in cattle in Poland.
The SNT is regarded as a gold standard in RVF serology, but it is very laborious and can only be performed in biosafety level-3 facilities, making this assay not very suitable for large-scale serosurveys. For these reasons, bovine sera collected in 2018 were all tested by commercially available RVF competitive enzyme-linked immunosorbent assay (ELISA) (ID Screen® Rift Valley Fever Competition Multi-species, IDvet Innovative Diagnostics, Grabeles, France). This assay is based on RVFV recombinant nucleocapsid protein (rNP). Advantages and validation data on rNP-based ELISAs vs the SNT in domestic and wild ruminates as well as in humans have been reported in earlier studies. Although results of this first RFV serosurvey study do not provide any serological evidence of RVFV infection in local cattle populations, the probability of introduction of exotic arboviruses in Europe cannot be ignored and should be monitored on a regular basis in EU member state countries.
Conflict of interest : None.
| Acknowledgements|| |
The authors would like to express their gratitude to Mr. M.A. Shyam and Mrs. Devaky Sivadasan for their technical support.
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