Assessment of West Nile Virus Infection in Turkey Based on Two Recent Cases
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ASSESSMENT OF WEST NILE VIRUS INFECTION IN TURKEY BASED ON TWO RECENT CASES Tugba Sari1, Dilek Menemenlioglu2, Ebru Aydin3, Tuba Nur Ozden4, Metin Kizilelma5, Hasan Irmak6 and Irfan Sencan6 1Department of Infectious Diseases and Clinical Microbiology, Faculty of Medicine, Pamukkale University, Denizli; 2Turkish Public Health Institution, Department of Microbiology Reference Laboratories; 3Turkish Public Health Institution, Department of Zoonotic and Vectorial Diseases, Ankara; 4Manisa Public Health Office, Department of Communicable Diseases, Manisa; 5Izmir Public Health Office, Department of Communicable Diseases, Izmir; 6Turkish Public Health Institution, Ankara, Turkey Abstract. West Nile virus (WNV) is an arbovirus maintained in enzootic trans- mission cycles between mosquitoes and birds and is occasionally transmitted to mammals. This study evaluated WNV-infected patients and public health mea- sures taken in Turkey. Upon notification of two cases of WNV neuroinvasive form in October 2016 serological and neutralization tests were performed and clinical and epidemiological surveillance studies conducted. A female patient in Izmir recovered but a male patient in Manisa died from the infection. The prevalence of suspected WNV-infected cases in the two provinces in 2016 varied between 0-22.1 per 100,000 population. However, patients diagnosed with viral encephalitis, arthropod-borne viral encephalitis or mosquito-borne viral encephalitis were not infected with WNV. From a “One Health, One World” perspective, collaboration among veterinary and health authorities, entomologists, environmental special- ists, and biologists, provides the best strategy towards control and prevention of WNV disease in Turkey. Keywords: West Nile virus, prevalence, Turkey INTRODUCTION through birds and mosquitoes, whereas humans and horses are considered dead- West Nile virus (WNV), a single- end hosts (Hubálek and Halouzka, 1999; stranded RNA virus of family Flaviviridae, Petrić et al, 2017). WNV was first isolated genus Flavivirus is the cause of a mosquito- in 1937 from a female patient in the West borne zoonotic disease with a mortality Nile District of Uganda (Smithburn et al, rate of 4-14% ( Rossi et al, 2010; Conde et al, 1940). WNV infection is a growing public 2017). The natural life-cycle of WNV is health problem, especially in regions of Africa, Asia, Europe, and the Middle East. Correspondence: Tugba Sari, Department of Europe has seen WNV fever epidemics Infectious Diseases and Clinical Microbiology, since 1960’s (Hayes et al, 2008). Turkey, Faculty of Medicine, Pamukkale University, a northeastern Mediterranean country, Denizli 20160, Turkey. is at risk for arboviral diseases such as Tel: +90 258 296 5766. Fax: +90 258 296 6000 WNV because of the country’s favorable E-mail: [email protected] ecological and climatic characteristics 86 Vol 50 No. 1 January 2019 WEST NILE VIRUS INFECTION IN TURKEY (Ergünay et al, 2011). the living/working place; and number WNV is mostly transmitted to hu- of patients with meningitis/meningoen- mans by mosquitoes of Culex genus, but cephalitis in the region were evaluated. also through virus contaminated blood Numbers of meningitis/meningoen- transfusion and organ transplantation cephalitis patients were calculated ac- and from infected mother-to-child route cording to 25 ICD-10 diagnostic codes during pregnancy, delivery or breastfeed- for meningitis and encephalitis (Turkish ing (Ergünay et al, 2017). The incubation Ministry of Health, 2016). Duplicate period lasts 3-14 days. While it is esti- subjects were excluded from the study. mated the majority of WNV infections are Prevalence is calculated as the number of asymptomatic, 20-30% of patients develop new cases/100,000 population. acute systemic febrile illness, and mostly Laboratory assays the elderly and immunocompromised Specimens kept at 4°C were submitted patients develop a neuroinvasive form, to the National Virology Reference eg encephalitis, meningitis or myelitis, Laboratories, Arbovirus and Viral Zoonotic which may lead to death (Winston et al, Diseases Unit and stored at -25°C until 2014); however, WNV infection is often tested for presence of anti-West Nile virus self-limited. Currently, there is no specific IgG and Ig M using ELISA (Anti-West Nile treatment or vaccine for WNV fever (Rossi virus ELISA IgG and IgM; Euroimmun, et al, 2010; Patel et al, 2015). Lübeck, Germany) and IFA (IIFT Flavivirus This study evaluated epidemiology Mosaic 1 IgG and IgM; Euroimmun) and public health measures following kits. Plaque-reduction neutralization test reports of WNV-infected patients in 2016 (PRNT) was carried out for detection of from Izmir and Manisa Provinces, Turkey. specific neutralizing antibodies according The information obtained should be of to case definitions by ECDC (2017a). value in the implementation of public IFA test was also performed for detec- health policies to control and prevent tion of flavivirus mosaic 1 (Euroimmun), spread of this potentially life-threatening tick-borne encephalitis virus (TBEV), yel- mosquito-borne viral disease. low fever virus (YFV), WNV, and Japanese encephalitis virus (JEV). A PRNT valida- MATERIALS AND METHODS tion test was performed with WNV/NY99 Study areas and surveillance procedures strain [using 200 plaque forming units Upon notification by the National (PFU) per reaction] for specific differential Virology Reference Laboratories in An- diagnosis of WNV. kara of two cases of WNV neuroinvasive Serum samples with >70% neutral- form in Izmir and Manisa Provinces in ization were accepted as seropositive. A October 2016, clinical and epidemiologi- confirmed case is defined as a patient with cal surveillance studies were conducted at least one of the following laboratory in the two provinces. Risk factors, such criteria: isolation of WNV from blood, de- as animal feeding, bird feed-contact, tection of WNV RNA by RT-PCR in blood, blood/ plasma/blood product delivery; detection of increasing levels of IgM and environmental factors, eg presence of mos- IgG against WNV using ELISA, and posi- quitos in living/working place, presence tive PRNT (ECDC, 2017a). Clinical criteria of water catchment area (lake/dam) near of confirmed WNV cases were based on a Vol 50 No. 1 January 2019 87 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH modified European case definition, which negative for WNV (including tests after includes neurological symptoms (ECDC, two weeks of admission) and other neuro- 2017a). trophic viruses [herpes simplex viruses (1 and 2), varicella zoster virus, Epstein-Barr RESULTS virus, cytomegalovirus, human herpes viruses (6, 7 and 8) and enterovirus] and Geographical features arboviruses using RT-PCR. Gram and Selendi District, Manisa Province, fungal stains of blood and CSF cultures situated at an altitude of 390 m above sea were negative as were autoimmune tests. level, and Kemalpasa District, Izmir Prov- Negative serological tests were obtained ince, at an altitude of 240 m surrounded for brucellosis, Lyme disease, leptospiro- by mountains covered with pine trees, lie sis, syphilis and tularemia were negative. in western Turkey. The two villages lie Computed tomography and magnetic among highly irrigated fields with access resonance imaging of the brain were un- to water from river channels. Weather is remarkable. The patients were given sup- usually warm in these regions and mos- portive treatment including intravenous quitoes are present nearly all year round. fluids and antipyretics, the female patient Cases was discharged in a healthy condition af- In 2016 two cases of WNV infection ter day 21 of hospitalization but the male were reported, a female (18 years of age) patient died on day 39 after admission. from Selendi District, Manisa Province Surveillance and a male (63 years of age) from Ke- In 2015 and 2016, Izmir and Manisa malpasa District, Izmir Province. Both Provinces reported 628 (143 cases in patients presented high fever (≥38.5°C), Manisa Province) hospitalized cases of nausea, vomiting, weakness, headache meningitis/meningoencephalitis in 2015 and lack of appetite. The patients were not and 528 (221 cases in Manisa Province) vaccinated against flaviviruses (yellow hospitalized cases in 2016. In Manisa fever, tick-borne encephalitis or Japanese Province the number of cases rose in encephalitis virus) and had a history of September, October and November, 2015 contact with animals and mosquitoes. and in July, August and September, 2016. The female patient was working as an Until October, 2016 when WNV infection agricultural worker in the vineyard and case was reported, 135 cases with men- her family had sheep. The male patient ingitis/meningoencephalitis cases had was a guard and living with six dogs. been admitted. Clinicopathological findings [high fever (≥ 38.5 °C), nausea, vomiting, weakness, Attention was focused on Manisa headache and lack of appetite] were sug- Province, given the 1.5-fold increase in gestive of WNV neuroinvasive form. Clin- meningitis/meningoencephalitis cases ical samples [cerebrospinal fluid (CSF) from 2015 to 2016. When the numbers of and blood] sent to the National Virology suspicious cases of meningitis/menin- Reference Laboratories in Ankara, showed goencephalitis in all districts in Manisa positive serological and neutralization Province from January to October, 2016 tests for blood (increasing levels of IgM were examined, prevalence varied from and IgG against WNV using ELISA, and 4.7 to 22.1 per 100,000 population, with 9.8 positive PRNT) but CSF