| Introduction
Rabies is a notifiable disease within both the public health and veterinary
surveillance systems in Poland. Terrestrial rabies posed a serious problem
in Poland in the 20th century, but within the past decade the epidemiological
situation has started to change [1]. Three key factors in the strategy
for the elimination of rabies have exerted a major influence both on
the pattern of animal rabies and on the risk of human rabies. These include
the introduction of mass vaccination of dogs in 1950, introduction of
safe and immunogenic cell culture based vaccine in 1984 and the introduction
of mass oral immunisation of foxes in 1993. The immunisation programme
for foxes was implemented in 1993 on the western border and was then
successively expanded eastward to cover the entire territory of Poland
in 2002 [2].
Following the implementation of oral immunisation programmes of foxes in
various European countries, rabies in terrestrial animals was eliminated
in some countries and dramatically reduced in others [3]. The problem of
and interest in bat rabies has become more significant.
Two genotypes of rabies virus have been isolated in Polish territory ,
genotype 1 ( classical rabies virus) from terrestrial animals and genotype
5 (European Bat Lyssavirus type 1, EBLV1) from bats. Moreover, diversity
within the genotype 1 cluster has been observed. Polish strains belong
to four different phylogenetic groups of genotype 1 rabies virus present
in Europe. Strains from two of the phylogenetic groups are dominant in
Polish territory and their geographic spread is strictly dependent on the
geographical barrier of the Vistula River. The north-eastern European (NEE)
group is limited to the eastern side of the Vistula river, and the central
European (CE) cluster has been isolated mainly in the west and south of
Poland - on the west side of the Vistula river [4].
The purpose of this article is to highlight the recent changes in the epizootiology
and epidemiology of rabies in Poland.
Methods
Data used in this study came from two sources. Cumulative data on annual
number of animal rabies from the Veterinary Inspectorate were used
to evaluate the epizootiological situation of rabies. In Poland, only
laboratory confirmed animal rabies cases are reported. Fluorescent
antibody test (FAT) is routinely used for diagnosis of rabies. Assessment
of the public health hazard and human exposure to rabies were based
on information derived from the routine infectious disease surveillance
system. Surveillance data on human rabies and administration of post
exposure treatment against rabies, collected by the National Institute
of Hygiene, consist of annual cumulative numbers from 1964 to 2004
and individual detailed reports on persons vaccinated against rabies
from 1990 to 2003.
Results
Animal rabies
Between 1990-2003, foxes (Vuples vulpes) were the main reservoir and
source of rabies in Poland, as they were during the preceding two decades.
They represented between 60% of all infected animals in 2003 (233/390),
69% in 2002 (822/1188), and 74% in 2001 (2241/3037) [FIGURE 1]. The second
most important host species were racoon dogs (Nyctereutes procyonoides).
In recent years the percentage of racoon dogs among all infected animals
appears to be increasing, although substantial fluctuations are present
[FIGURE 2]. The influence of oral immunisation programme of foxes introduced
in 1993 became clear from 2002 [FIGURE 1]. The number of cases in 2004
(136 cases) was nine fold lower compared with 2002 (1188) and 17-fold
lower than the median annual number of cases during 1990-2001 (2294.5).
The proportion of infections occurring in domestic animals varied between
17% and 23% of the total number of cases of animal rabies. Rabies
in domestic animals is closely related to rabies in foxes and racoon
dogs.
Between 1990–2003, no cases in domestic animals were reported
in territories where no cases of rabies in wild animals occurred in
the
same year.
Until 1998 only 4 cases of bat rabies had been reported in Poland.
However, in recent years, several cases have occurred every year.
The annual number
of rabid bats reported in 1998-2004 varied between 4 in 1999 to 14
in 2001 and 10 in 2004. Although the numbers are not high, their
relative
importance is increasing [FIGURE 2].
Human rabies
No human cases occurred between 1985 and 2000 in Poland. Then two deaths were
reported - in 2000 and 2002. Both infections were acquired in Polish territory.
The first case occurred in a 59 year old woman in northeast Poland who was
bitten on the finger by her cat in 2000. The second case occurred in a 28
year old man in southern Poland in 2002, who was most probably exposed to
a wild animal. The strains of rabies virus isolated from both cases belonged
to genotype 1. The first one represented the phylogenetic group north-eastern
Europe (NEE) and the second one the central European (CE) group. Neither
patient received either pre- or post-exposure prophylaxis.
Human post-exposure treatment against rabies
In Poland, a country of approximately 38 millions inhabitants, post-exposure
treatment is administered to approximately 7000 persons annually. The
individual reports sent to the National Institute of Hygiene from 1990
to 2003 cover approximately 90% of all persons vaccinated against rabies.
Of the 100 395 persons vaccinated against rabies in this time period,
only 26% were immunised following exposure to animals definitively
confirmed to be rabid; 64% were immunised following exposure to animals
in which rabies could neither be ruled out nor confirmed.
The proportion of different animal species to which humans are exposed
is unrelated to their distribution among all reported rabid animals in
Poland. Rabid dogs and cats, constituting about 12% of all infected animals,
were the reason for vaccination for 74% of the total number of vaccinees
[FIGURE 1].
Contact with rabid foxes, which represent 68% of rabid animals, were
the reason for vaccination for only 9% of the total number of vaccinees.
Moreover, in the case of red foxes, indirect contact (e.g. contact with
a dog bitten by a fox), touching and contact with saliva were the most
common types of exposure (88%), leading to human vaccination. Exposures
among vaccinees to dogs and cats were most often associated with bites
(83%).
Impact on post-exposure treatment
Figure 3 shows time trends in the numbers of vaccinated people, compared
with the number of cases of animal rabies. The impact of two important
events on the number of post-exposure treatments administered was considered.
Firstly, in 1984, a highly immunogenic and safe cell-culture vaccine
against rabies was introduced for human use. Secondly, in 1993, mass
oral rabies vaccination of foxes was implemented. From the introduction
of the cell culture vaccine the number of vaccinated people increased.
This trend has continued in recent years, although a considerable decrease
in animal rabies cases was already apparent.
Discussion and conclusion
Routine surveillance data confirm a decreasing trend in animal rabies,
which is a consequence of the implementation of the fox immunisation
programme. At the same time, an increase of rabies reservoirs other
then fox host species has been observed, which merits further attention
and is currently being investigated. One important example is the increasing
importance of bat rabies, while terrestrial rabies incidence is falling.
At the present time it is difficult to determine whether there is a
real increase of rabies infection in bats, or whether this observation
results from greater attention given by the public health authorities.
Public attention and fears currently seem to be most focused on foxes
as the source of rabies. This is supported by the fact that the majority
of human post-exposure treatments are administered following low risk
contact such as being licked by a fox, or even having indirect contact
with foxes.
In contrast, dogs and cats either known or suspected to be rabid were
responsible for most of the bites and abrasions. This underlines the
importance of preventive vaccination of these animals against rabies
and their potential influence on the human hazard. Immunised dogs and
cats create a protective barrier between wild animals and humans. This
was once again confirmed by the recent case of human rabies in a person
exposed to a cat.
Recent human cases show that the risk of becoming infected on the Polish
territory is still present. Additionally, new risk factors have emerged,
such as travel to rabies endemic areas. Based on the situation in France,
the United Kingdom and Germany, where animal rabies is eliminated or
well controlled, we may expect that in the near future cases of human
rabies will be imported rather then acquired in Poland [5,6,7]. In conclusion,
rabies should still be considered a public health concern in Poland.
Moreover, there is a need to fill the existing gaps in public awareness
about rabies.
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