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Importance of Acaricide Treatment for Prevention of Natural Focal Infections of Tick-Borne Encephalitis and Lyme Borreliosis in St. Petersburg

 Rediger
  Published: 14.08.12 Updated: 16.08.2012 14:31:04

S. Bogachkina1, I. Rakitin1, A. Meltser1, O. Parkov1, I. Chhindzheria1, L. Antyikova2, A. Datskevich3

1 Directorate of the Federal Service for Surveillance on Consumer Rights Protection and Human Well-Being (Rospotrebnadzor) in the City of St. Petersburg, Russia
2 Hygiene and Epidemiology Centre in St. Petersburg, Russia
3 Municipal Disinfection Station in St. Petersburg, Russia

Citation: Bogachkina S, Rakitin I, Meltser A et al. Importance of Acaricide Treatment for Prevention of Natural Focal Infections of Tick-Borne Encephalitis and Lyme Borreliosis in St. Petersburg. EpiNorth 2011; 12: 76-82.

Abstract

In the last five years, the share of tick-borne encephalitis and borrelioses within the structure of all natural focal diseases registered in St. Petersburg was 77-89%.
Seven of eighteen administrative districts of St. Petersburg are included in the list of areas endemic for tick-borne encephalitis in the Russian Federation. The incidence of tick-borne infections in St. Petersburg depends primarily on the frequency with which non-immune citizens visit infection foci located in Leningrad oblast (1). Most patients infected with tick-borne encephalitis (72%) had been bitten by ticks in Leningrad oblast, 26% were bitten in other areas while 2% (1 case) were bitten in the city of St. Peterburg. The majority of patients infected with Lyme disease reported that they had been bitten by ticks in Leningrad oblast (70%, 217 people) and in suburbs of St. Petersburg (4 %, 11 people). The rest of the patients (26%) had been bitten by ticks in other administrative territories. The tick-borne encephalitis infectiousness of ticks in St. Petersburg during 2006-2010 was 0.8-1.0%, while Lyme disease infectiousness varied from 10% to 28% during the same period. In accordance with the data of the Directorate of the Federal Service for Surveillance on Consumer Rights Protection and Human Well-Being in the City of St. Petersburg (Rospotrebnadzor in the City of St. Petersburg), every year 7 to 16 thousand people bitten by Ixodes ticks visit the municipal medical and preventive treatment facilities; 1-1.5 thousand report that they have been bitten in suburbs of the city.

Introduction
Tick-borne encephalitis can result in severe clinical disease, complications, lethality and a high incapacitation rate. Because there is no specific prophylaxis for Lyme disease, ehrlichiosis, anaplasmosis and other tick-borne infections, acaricide treatment remains the most effective preventive measure to be taken against these diseases in St. Petersburg. This article presents our experience with acaricide treatment in St. Petersburg for prevention of tick-borne infections.

Methods
Only two species of ticks of epidemiological importance, Ixodes persulcatus (dominant species) and Ixodes ricinus (not as widely spread), are found in the city suburbs. The peak of tick activity is usually in May and June. At the end of June and beginning of July the number of attacking ticks decreases, after which the activity intensifies again in August. The use of the insecticide DDT (dichloro-diphenyl-trichloroethane) was prohibited in 1972 and since there has been no treatment of natural foci against tick-borne infections. As a result, the number of ticks and cases of tick-borne infections has increased. In 1999, four hectares in the town of Pavlovsk were treated against ticks with a new acaricide. The effectiveness of Baytex 40% W.P. (Bayer AG, Germany) was tested for eliminating Ixodes ticks carrying various infections (2). Baytex was 95% effective within 24 hours and from 72 hours to 7 days was 100% effective. Effectiveness was estimated by counting ticks in the treated area before and after treatment. The residual effect of the agent lasts no longer than a month.
Specialists of the Federal State Healthcare Institution “Centre of Hygiene and Epidemiology in the City of St. Petersburg” are responsible for regular monitoring of the spread, dynamics and species composition of Ixodes ticks. In addition they study prospective and current foci of tick-borne encephalitis and borrelioses in the city. The Directorate of the Federal Service for Surveillance on Consumer Rights Protection and Human Well-Being in the City of St. Petersburg (Rospotrebnadzor in the City of St. Petersburg) organizes and implements acaricide treatment.

Results and Discussion
Annually, 7-16 thousand people bitten by ticks visit the medical and preventive treatment facilities of the city; 1-1.5 thousand report that they have been bitten in suburbs of the city (Figure 1).

Fig. 1. Number of people who visited medical and preventive treatment facilities after being bitten by ticks, St. Petersburg, 2005 - 2010

 
The average number of Ixodes ticks in the last decade varied from 2.3 to 9.2 ticks per flag-hour. In 2006-2010, 0.8-1.0% of ticks found in St. Petersburg were infected with tick-borne encephalitis; the infestation of ticks with borrelias increased from 10% in 2006 to 28% in 2010.
Acaricide treatment has been conducted since 2000 in the areas surrounding children’s out-of-town institutions where Ixodes ticks are found (11 hectares). From 2001 to 2005, 213 hectares around such institutions underwent acaricide treatment. In 2001, the Yuzhnoe Cemetery was included in a trial of the insecticide/acaricide agent “Cifox”. The effectiveness was 98% within 24 hours and 100% from 72 hours to 7 days. The residual effect of the agent lasts no more than a month. In 2002, environmentally safe acaricides produced by Russian manufacturers including “Cifox” and “Taran” started to be used. Since 2003, acaricide treatment of parks, woods and cemeteries have been performed in Vyborgsky, Kurortny, Petrodvortsovy, and Primorsky districts. The volume of treatment has gradually increased to include additional current and prospective foci of tick-borne encephalitis and Lyme disease in the city area. From 2000 to 2005, a total area of 480.3 hectares was subjected to acaricide treatment. The acaricide treatment campaign in parks and cemeteries was financed by various organizations and municipal councils.
From 2005 to 2011, three decrees of the Government of St. Petersburg were prepared and approved on an initiative from the Directorate of Rospoterbnadzor in relation to tick-borne infections (3,4,5). In accordance with the decrees, the plans were approved for preventive measures against natural focal infections, extremely dangerous infectious diseases and rodents’ control in St. Petersburg. The city government imposed the responsibility for the organization and implementation of acaricide treatment on the heads of district administrations in the city.
The plans included the following measures:
- vaccination of people visiting and living in areas endemic for tick-borne encephalitis;
- expert monitoring of areas in various districts of the city that are most often visited by citizens in order to estimate the magnitude of treatment required;
- organization and implementation of acaricide treatment;
- estimation of acaricide treatment effectiveness.
Since 2007, the volumes and dates of acaricide treatment of the city area and children’s out-of-town recreational institutions are annually approved by the decrees of the Chief State Sanitary Doctor of the city of St. Petersburg (6,7). In 2009, the Regulation on Acaricide Treatment in St. Petersburg and in Children’s Out-of-Town Institutions was approved. Acaricide treatment in various parts of the city and in children’s out-of-town recreational institutions is provided by public and private disinfection organizations. In 2010, 70% of work was performed by private institutions and 30% by state-owned organization.
Entomological surveys conducted by experts in the affected areas documented the maximum effectiveness of anti-tick treatment despite of quite short residual effect of acaricides. The following agents were used: Alfatrin (water-soluble powder manufactured by CJSC NKF RAT, Moscow), Acaritox 5% W.P. (water-soluble powder manufactured by Sulphur Mills Ltd., India), Cifox (emulsion concentrate manufactured by LLC NPC Fox & Co., Moscow), Cipaz Super (manufactured by Hallmark Chemicals, Netherlands) and Baytex 40% W.P. (manufactured by Bayer Environmental Science S.A., Germany). These agents were evaluated for weatherproof durability, combustibility, storage life and visual control. According to these criteria Baytex was the best followed by Acaritox, Alfatrin, Cipaz Super and Cifox.
Acaricide treatment was performed using “Quasar” backpack mist sprayers and pneumatic sprayers with a petrol engine. The latter showed high productive capacity that facilitated the work without detriment to the quality of the acaricide treatment. The production and expert control was provided by specialists from the department of preventive disinfection and from the Federal State Health Care Institution “Centre of Hygiene and Epidemiology in the City of St. Petersburg”.
The effective collaboration between the Directorate of Rospotrebnadzor in the City of St. Petersburg, the Government of the city and the district administration representatives resulted in timely and full-scale acaricide treatment of the city areas that are endemic for tick-borne encephalitis and frequently visited by citizens. The increase in the volume of acaricide treatment in combination with other preventive measures contributed to a reduction in the number of people bitten by Ixodes ticks and a decreased incidence of tick-borne infections in St. Petersburg. The number of patients bitten by Ixodes ticks in the city suburbs decreased by 26%: 1303 and 970 people were bitten in 2009 and 2010, respectively (Figure 2).

Fig. 2. Number of patients bitten by Ixodes ticks within the city and volume of acaricide treatment (in hectares) in St. Petersburg, 2005-2010

 

The number of children bitten by ticks in the areas of out-of-town recreational institutions decreased from 47 cases in 2005 to 0 cases in 2010 (Figure 3).

Fig. 3. Number of children bitten by Ixodes ticks in children’s out-of-town recreational institutions and volume of acaricide treatment (in hectares), 2006-2010

 

In 2010, the incidence of tick-borne encephalitis decreased by 42% in comparison with the previous year. Among children under the age of 14 the number of cases decreased by 8%. During 2010 were registered 43 cases of tick-borne encephalitis including 12 cases among children under the age of 14. In 2009 there were 74 cases registered including 13 cases among children). The incidence in 2010 was 0.94 per 100,000 population compared to 1.62 in 2009, which is 2.3 times lower than the average incidence in the Russian Federation (2.19) (Figure 4).
The incidence of Lyme disease in 2010 in comparison with the previous year decreased by 38% yielding a rate of 6.7 per 100,000 population. In 2009 the incidence was 10.66 per 100,000 population. However, the incidence was still higher than the average in the Russian Federation (4.98). A total of 307 cases of Lyme disease were registered including 29 cases among children under 14 years of age in 2010 as compared to 487 cases including 70 cases among children in 2009 (Figure 4).

Fig. 4. Dynamics of tick-borne encephalitis and Lyme disease incidence and volume of acaricide treatment (in hectares) in St. Petersburg, 2005-2010

 

Conclusion
Thus the increase in volume of acaricide treatment resulted in the following:
• Created a barrier for the spread of ticks to the city of St. Petersburg from Leningrad oblast which is the recreational area for the urban population and which has still low volume of acaricide treatment.
• Helped to reduce the number of ticks and the number of bitten people in the suburbs of St. Petersburg.
• Reduced the number of cases of tick-borne encephalitis infected within the city border to single cases.
• Reduced to 0 the number of children bitten by Ixodes ticks in children’s out-of-town recreational institutions.
The main preventive measure against tick-borne encephalitis is still vaccination of the city population, primarily children and those who travel to areas endemic for tick-borne encephalitis for summer vacation and work.

References
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