COMPARATIVE ANALYSIS OF RABIES THREAT IN SELECTED ADMINISTRATIVE DISTRICTS OF POMERANIA AND WARMIAN-MAZURIAN PROVINCES IN THE YEARS OF 1997-2001

Krystyna Iwańczuk-Czernik, Dorota Witkowska, Tomasz Mituniewicz, Anna Wójcik, Krzysztof Machol, Elżbieta Kosznicka

ABSTRACT

The goal of this study was the comparison of rabies threat dimension in selected administrative districts of Pomerania and Warmian-Mazurian Provinces in the years of 1997-2001 in relation to humans and animals. The oral immunization of wild animals in Gdańsk administrative district began in 1995, while the immunization of foxes in Ostróda administrative district began as late as in 2001. One (1) case of rabid fox was diagnosed in 1997 in the area of Gdańsk administrative district. During the remaining discussed years no cases of rabies were noted in this area. In Ostróda administrative district, however, the rabies infection factor remains at a high level. In the years of 1997-2001, 104 cases were registered among wild animals and 49 cases among domestic animals. In 2001 the number of rabid animals from Ostróda administrative district fell of over a half in comparison to the year 2000. In the years of 1997-2001 in Gdańsk administrative district, 428 individuals had contact with an animal si

Key words: rabies, epizootiology, epidemiology, immunizations.

INTRODUCTION

The problem of rabies in Poland is very significant. In 1996 and 2000, the majority of rabies cases among animals in Europe were noted in our country [2]. According to Zienius et al. [17], the highest average number of infected animals among countries bordering on Lithuania fell to Poland in the years of 1995-2000. Smreczak [12] reports that over the period of 18 years – from 1983 till 2000 – 18.6% of domestic animals and 81.4% of wild animals in Poland were infected with rabies. Among domestic animals, the majority of diagnosed cases during this time were in cattle, while the next animal with regard to the infection frequency was the cat, and the dog was found to be only in the third position. Among wild animals, foxes were definitely the first group of animals infected with rabies over the analyzed period of time, and their number amounted to 82.5%. The second species in the group of wild animals was found to be the racoon (8.3% of infection cases).

According to Miller [4], at present rabies divides Poland into three parts: western, where rabies was practically eliminated; central, where some few cases still occur; and north-eastern, where most infections take place. This division results from the fact that in Western Poland the oral immunization of wild animals began in 1993 [3]. In the following years, the provinces of western-central and southern Poland were included in this program, while prophylactic immunization started at the latest time in areas with the highest percentage of cases of rabid animals noted at present.

The whole area of Warmian-Mazurian province (21.483 km²) was included in the program of oral immunization of wild foxes, in two yearly campaigns, in 16 – 20 doses per km², as late as since spring of 2001 [16]. The immunization action in the years of 1999-2000 comprised only the area of 3.071.7 km² of the former province of Elbląg. In the former provinces of Gdańsk, Słupsk or Bydgoszcz included in the present Pomeranian province, however, the wild animal immunization began as soon as in the years of 1994 – 1995 [3, 5, 6, 10].

The Pomeranian province belongs to the most afforested provinces as the Report of Forrest State in Poland says [8]. Forests constitute here 35.6% of its general area [14]. The administrative district of Gdańsk, with the area of 793 km², is located in the central part of the Pomeranian province. Wood complexes occupy 17.5% of its area, i.e. 142 km² [14].

With regard to afforestation, the Warmian-Mazurian province takes its place slightly above the country average – woods take here 29.6% of the general area. Ostróda administrative district is located in the western part of the province, occupying the area of 1 765 km², out of which the woods constitute 28.4% (515 km²) [15]. The high afforestation of these areas is related to the possibility of occurrence of a large number of wild animals, including foxes and racoons, which constitute a natural reservoir of the rabies virus.

The aim of this study was to confirm the effectiveness of the oral immunization of foxes through the analysis of rabies threat dimension with regard to humans and animals of Gdańsk and Ostróda administrative districts, where the immunization action began in two dates distant in time from each other.

MATERIAL AND METHODS

The administrative district of Gdańsk, with the seat in Pruszcz Gdański, is a newly created district which accompanied the introduction of the country administrative reform on 01.01.1999. Until that time, the area of the present administrative district of Gdańsk belonged to several Regional, and currently to District Sanitary-Epidemiological Stations in Gdańsk, Kartuzy, Starogard Gdański and Tczew. For the reason of the above, statistic data concerning rabies in humans in the area of Gdańsk administrative district in the years of 1997-2001 were collected in the Provincial Sanitary-Epidemiological Station in Gdańsk and in the District Sanitary-Epidemiological Stations in Gdańsk, Kartuzy, Pruszcz Gdański, Starogard Gdański and Tczew. In 1997, the above mentioned sanitary-epidemiological stations were visited by 59 individuals suspecting themselves of the possibility of contracting the rabies virus. There were 72 such individuals in 1998, 89 – in 1999 and 114 – in 2000, while in 2001 – 94. A t otal of 428 individuals were subject to examination in the administrative district of Gdańsk within the period of all the years.

The data concerning rabies in animals in the area of Gdańsk administrative district constitute the documentation of the Provincial Veterinary Inspectorate in Gdańsk and District Veterinary Inspectorates in Gdańsk and Pruszcz Gdański, where 1 fox was documented as rabid in 1997, while in the years of 1998-2000 there were no registered cases of the disease among animals.

The data concerning rabies in humans in the administrative district of Ostróda constitute the documentation of the District Sanitary-Epidemiological Station in Ostróda, which was visited by 2 186 individuals suspecting themselves of the possibility of contracting rabies in the years of 1997-2001 (377 individuals – in 1997; 350 – in 1998; 429 – in 1999; 562 – in 2000; 468 – in 2001).

The data concerning the incidence of rabies in animals in the area of Ostróda administrative district in the years of 1997-2001 were documented by the District Veterinary Inspectorate in Ostróda and Veterinary Hygiene Institute, where 14 cases of rabid animals were registered in 1997, 4 cases – in 1998, 28 cases – in 1999, 72 - in 2000 and 35 – in 2001. A total of 153 animals were diagnosed with rabies in the area of Ostróda administrative district in the years of 1997-2001.

RESULTS AND DISCUSSION

One case of rabies in a fox was diagnosed in 1997 in the area of Gdańsk administrative district (Table 1). In the years of 1998-2001 no cases of rabies were diagnosed in the discussed area, neither in humans nor in animals (Table 1, 2). As for Ostróda administrative district, 104 cases of rabies were registered in wild animals (Table 1) as well as 49 cases in domestic animals (Table 2) in the years of 1997-2001. From 1997 till 2000, except for 1998, the number of infected animals in the administrative district of Ostróda increased (Fig. 1), reaching its peak in 2000. In 1998 rabies was confirmed by laboratory tests only in 2 foxes, 1 marten and 1 cow (Table 1, 2) in the area of the discussed administrative district. In the year 2000, 72 animals were found to be rabid in Ostróda administrative district (41 wild and 31 do mestic animals), while in 2001 the number of animals diagnosed with rabies dropped to 35, i.e. to 25 wild and 10 domestic animals (Table 1, 2). In the area of Ostróda administrative district in the years of 1997-2001, rabies was found in 71 foxes, 27 racoons, 4 badgers, 2 martens (Table 1) as well as in 30 heads of cattle, 11 dogs and 8 cats (Table 2).

In the administrative district of Gdańsk, 34 630 dogs and only 84 cats were immunized against rabies in the years of 1997-2001 (Table 3). The number of immunized cats in Ostróda administrative district was slightly higher (568); yet in comparison to dogs (48 926), it also proved to be insignificant (Table 3).

As far as the immunization of humans is concerned, in Gdańsk administrative district in the years of 1997-2001, 428 individuals had contact with an animal sick or suspected of rabies, out of which 76 were subject to immunization (Table 4). In the area of Ostróda administrative district, 2 186 individuals reported the possibility of contracting the rabies virus during the discussed years, out of which 537 were immunized (Table 4). Nevertheless, one must take into consideration the fact that the administrative district of Ostróda is inhabited by 112 thousand people, while the administrative district of Gdańsk numbers 79 thousand inhabitants. In spite of the fact that no case of rabies in animals has been diagnosed in Gdańsk administrative district since 1998, yet the number of individuals having contact with suspected animals as well as the number of immunized humans increase every year. In 1997, 59 individuals reported to the Sanitary-Epidemiologic al Stations in this area, out of which 10 were subject to immunization, while in 2001 out of 94 reported individuals, 22 were immunized (Table 4). In Ostróda administrative district, the fewest individuals (350) reported for immunization in 1998, when there were also the fewest diagnosed cases of rabies in animals. Only 31 individuals were immunized then. The highest number of the reported and immunized humans was noted in this area in the years of 2000-2001. In 2000, 562 individuals had contact with an animal sick or suspected of rabies, out of which 175 were immunized. In 2001, 468 individuals were reported, out of which 195 were immunized (Table 4). The highest number of wild and domestic animals were found to be rabid during that period in the administrative district of Ostróda (Table 1, 2).

In spite of the high extent of afforestation, the Pomeranian province – together with Gdańsk administrative district belonging to it – is one of those provinces in Poland where the problem of rabies begins to disappear. In the years of 1999-2000, 21 cases of rabies among animals occurred in the Pomeranian province as Mól reports [7].

As for the administrative district of Ostróda, the epizootiological situation is much worse. The index of rabies incidence among animals in this area, with regard to province and country, still remains at a high level. However, in 2001 the number of rabies cases in the area, though still high, decreased significantly in comparison to the year 2000 (Fig. 1). As results from the information of the Provincial Veterinary Inspectorate in Olsztyn [16], a similar – like in the whole administrative district of Ostróda – decrease tendency after the year of 2000 remains in the whole Warmian-Mazurian province. In 2000, 446 animals infected with rabies were registered here – 315 wild and 131 domestic animals. In 2001 the number of the disease incidence decreased to 387, including 294 wild animals and 93 domestic ones, while in 2002 only 40 cases were diagnosed, including 30 wild animals and 10 domestic ones.

An increasing number of sick racoons requires attention, particularly in the area of north-eastern Poland. In 1997, 1 case of rabies was diagnosed in this species in the area of Ostróda administrative district, in 1998 – none, while in 1999 – 10, and in 2000 – 11 racoons. In 2001, this number decreased to 5 sick animals (Table 1). Mól [6] reports that in the years of 1976-1998 the majority of rabid racoons were noted in the former provinces of Olsztyn, Suwałki, Gdańsk and Elbląg. As results from the analysis of Smreczak [12], in 1983 only 28 racoons were found to be rabid in Poland, while in the following years this number increased up to 231 in 1992, and then it began to drop slowly to 93 cases in 1997. An increasing number of sick racoons have been noted again since 1997. In Lithuania, as Zienius reports [17], located in close neighborhood to the Warmian-Mazurian province, a higher increase of racoon population over the fox population was noted in the years of 1995-2 000, which directly influenced the dynamics of rabies incidence there. Over the period of a decade (1990-2000), 470 cases of rabies among racoons were noted in Lithuania, out of which 407 cases occurred in the last three years. It is possible that another important virus reservoir is in the process of formation in nature [17].

Among domestic animals, the majority of rabies cases in the administrative district of Ostróda, particularly in the year 2000 (23 cases), were diagnosed in cattle (Table 2) A similar tendency is observed in the whole country. Smreczak [12] states that this situation results from the ease of attacking cattle grazing in the pastures by rabid foxes, lacking their natural fear. Therefore, it would be worth considering the introduction of cattle immunization against rabies before turning them out to pastures. The compulsory immunization of cats would also undoubtedly limit the spread of rabies among animals, especially that in Poland during the period of 18 years (from 1983 to 2000) the infected cats took their position directly after the cattle infected with the rabies virus. In Ostróda administrative district in the years of 1997-2001 cats took the third position after cattle and dogs, with regard to rabies infection; however in 2001, the number of sick cats was equal to that of dogs (Table 2). It should be added that rabies in cats constitutes a specific indicator of the disease incidence in foxes in a given area [quotation 12], since the cat, as an animal not kept tethered, frequently gets in contact with rabid foxes while hunting [12].

In Gdańsk as well as in Ostróda administrative districts, a small percentage of cats was subject to immunization during the discussed years (Table 3), which might indicate that domestic animal owners have not been sufficiently made aware of the causes and consequences of rabies, and only legal regulations can force them to immunize cats. A spokesman of the Warmian-Mazurian Provincial Chief Veterinary Doctor reports that the Warmian-Mazurian Voivode submitted a motion to the Minister of Agriculture and Rural Development to issue a decree concerning compulsory immunization of cats against rabies [16].

Since July 1985 no cases of rabies in humans were found in Poland until the year 2000, when in a town near Iława in the Warmian-Mazurian province a cat’s owner, who ignored the attack by her own animal and did not report for immunization, died; and then in 2002, when one case of rabies was diagnosed in an individual in Podkarpackie province [1, 11, 13].

The suppression of rabies among animals in the area of Gdańsk administrative district had no influence on the decrease of immunized humans; to the contrary, this number increased year by year during the discussed period (Table 4). In Ostróda administrative district, except for 1998, a similar tendency was observed among individuals subject to immunization in the years of 1997-2001 (Table 4). The number of individuals immunized against rabies in the Pomeranian province in the years of 1998-2001 oscillated between 407 and 582, with the highest number in the year 2000 [1]. The number of immunized individuals exposed to a contact with an animal suspected of rabies in the Warmian-Mazurian province in the following years is increasing (1 008 individuals were immunized in 1998, while 1 484 – in 2001) [1]. A similar growing tendency can be observed since 1999 in the whole country, where 7002 individuals were immunized in 1999, 9 914 – in 2000, while in 20 01 there were as many as 11 382 of such individuals [1]. According to Seroka [9] this results from the fact that the drop in the number of detected cases of rabies in animals, particularly in western and central Poland, cannot be yet equivalent to the liquidation of all animal sources of infection. The exemption from the immunization of humans exposed to infection from domestic animals, which are the most frequent reasons of undertaking immunization, will become possible when all animal infection sources have died out [9, 11].

CONCLUSIONS

1. Long-term oral immunization of foxes significantly reduces the spread of rabies among wild and domestic animals.

2. Compulsory immunization of cats as well as cattle immunization, before the grazing season, could significantly reduce the spread of rabies among domestic animals.

3. It is necessary to familiarize the public with the threats related to rabies and with the importance and effectiveness of prophylactics against this dangerous disease.

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