9th Symposium of the
International Society for Veterinary Epidemiology and Economics,
ISVEE 9 Proceedings
SURVEILLANCE SYSTEM
SUPPORTING ZOONOSES PREVENTION, REDUCTION AND
ERADICATION IN
Kouba V.
Formerly: Chief, Animal Health Service, Food and
Agriculture Organization of the United Nations and Professor,
Ten years after
World War II hundred thousands of animals and thousands of humans
suffered by different zoonoses and the situation was becoming worse due to lack
of control programs. Czech authorities decided to start campaign against
major zoonotic diseases. The action had
to cover country territory of 78864
km 2 with about 10
million inhabitants, 3.5 million heads of cattle, 5 million pigs and 30
million chicken. The task was to improve
animal populations health and thus to protect inhabitants against zoonoses,
reduce their incidence and increase food production. Data about zoonoses were
based upon ad hoc reporting clinically
manifested cases with only local response having no impact upon country
situation. Incomplete data collection
only for "statistics" proved to be waste of time and resources. In world literature suitable methods for
multi-disease surveillance system in a territory with prevailing intensive
large-scale livestock were missing. Therefore, to start effective programs
against zoonoses, it was necessary to develop a new original system. This paper
is based mainly upon official documents (1,5,6,7)
as well as experience of the author (2,3)
as former Chief epizootiologist
responsible for national animal population diseases control programs.
Material &
Methods
For selection of priority zoonoses following criteria
were used: disease occurrence (morbidity and nidality), stage, trend and territorial distribution in animal and human
populations, public health, economical and social importance, program feasibility,
availability of necessary inputs and success probability. Following zoonoses
were selected: bovine brucellosis and
tuberculosis, rabies, salmonellosis, toxoplasmosis, leptospirosis, listeriosis,
tularaemia, ornithosis, trichophytosis, anthrax and zoonotic helminthiases
(taeniasis-cysticercosis, hydatidosis- echinococcosis and trichinellosis). Surveillance aim was in diseases to be
eradicated or eliminated to discover all
not yet registered affected herds, in diseases to be reduced to discover
new affected herds and in the others to reconfirm specific zoonoses free
status. Common tasks were to monitor zoonoses trend, survey risk of their
introduction from abroad, provide data for programs evaluation, managerial
operation and strategic decision and identify research and resources needs.
Objective of the study was to develop effective and
flexible surveillance procedures linked with field control measures for
different situations and conditions. Particular information system (data
collection, collation and interpretation) for situation analyses, tendency
study and early warning about critical problems was introduced.
Quantitative indicators such as ratio of tests/population (RTP) and
ratio of tests/discovered cases (RTC) were used. Data collected from field,
laboratories, slaughterhouses, clinics etc. were used for operational response
and later published in "Zoonoses
surveillance" yearbooks written by specialists for individual zoonoses of both services.
The new system required new legislation defining
obligation to report new cases, apply control measures, etc.. Forms, indications and frequencies of
specific preventive investigations as well as standard field and laboratory
diagnostic methods for individual zoonoses in different species under different
conditions were elaborated and made
obligatory. Particular attention was given to exposed animals in critical
places, periods and moments (e.g. related with trade, import). Monthly
"prevention days" consisting in visits of veterinarians in all larger
farms (to detect signs of livestock diseases and control the measures) were
included into the system. For veterinary and public health services were issued
special instructions for activities at field, laboratory and management levels
following surveillance findings.
Laboratory serological tests supported by
microbiological investigations represented the most used diagnostic methods.
Tuberculosis surveillance consisted mainly in PPD tuberculin tests (neck skin)
and slaughterhouse inspections. All suspect cases were investigated using
complexes of available methods to clarify the etiology (including types). A
dense network of well equipped and staffed diagnostic laboratories (up to one
thousand specialists) were built during initial stages. Reference laboratories within both services
and intersectorial national, provincial
and regional committees for coordination were established. Indications and
number of preventive investigations, as
priority component of the surveillance, were planned every year. Major
frequency of tests was in diseases to be eradicated or eliminated to discover
all affected herds. Organization and management of government services were
adjusted and necessary input ensured (manpower, diagnostics, equipment,
premises, transport, funds, etc.). Networks of regional and provincial epizootiologists and epidemiologists were
developed. Up to 2,5 thousand government veterinarians were involved.
Systematic postgraduate training helped to proceed uniformly. Epizootiology as
subject of animal population medicine was included into
undergraduate education.
Results
Action
oriented multi-disease surveillance system to support zoonoses prevention,
reduction and eradication was developed in a country with predominant intensive
large-scale livestock production units. The system ascertained specific health/diseases status,
early detected new outbreaks and important changes of influencing factors and
thus enabled appropriate follow-up
actions. The system has contributed
significantly to anti- zoonotic programs as their integral parts providing them
information about specific zoonosis
risk and discovering new or not yet registered cases for early follow-up
measures, evaluation and correction of particular program operation and
strategy as well as reconfirming disease free status (e.g. for trade purposes). Key surveillance actions consisted
in active preventive diagnostic tests. During
forty years several hundred millions of preventive tests were carried out to discover zoonoses
reality and risks. Maximal annual value of RTP was
in bovine tuberculosis 2.01 (6109595 tuberculin tests in 1967) and in
bovine brucellosis 0.52 (1568021
serological tests in 1959). Examples (annual averages):
___________________________________________________________________
Zoonoses Stage Period Tests RTP Cases RTC
---------------------------------------------------------------------------------------------------------------------------
Bov.brucellosis Eradication 1959-64 1385320 0.45 3208 432
Post-eradic. 1965-75 751886 0.25 20 * 37939
1976-98 569747 0.19
0 13 million/0
Bov.tuberculosis Elimination 1959-68 5030449 1.65.
93304 54
Post-elimin. 1969-88 5269568 1.59 863 *+ 6108
1989-98 1994992 0.84
156 *+ 12830
*
Import + M.avium
The system has contributed to substantial reduction of
zoonoses. In animal populations was eradicated bovine brucellosis (in 1964
after stopping vaccination from the very beginning) and anthrax (in 1976), bovine tuberculosis was eliminated (in 1968)
as well as trichinellosis and
hydatidosis, while rabies,
trichophytosis and taeniasis were significantly reduced, etc. Improvement of zoonoses situation in
animals was followed by the reduction of zoonoses in human population: incidence of brucellosis caused
by Brucella abortus and tuberculosis
caused by Mycobacterium bovis,
rabies, anthrax, trichinellosis and
hydatidosis stopped and of the others was reduced.
Discussion
Majority of zoonoses has subliclinical forms and their
discovery requires active search
using tests supported by laboratory
etiological diagnosis. Therefore, the previous superficial “paper surveillance” based upon
ad hoc reporting of manifest
cases only, serving mainly for "statistics" and overloading
administration, had been replaced. The
most effective proved to be action-oriented surveillance based upon mass,
active, systematic and intensive etiological investigations linked with
feasible corrective practical response. Very important were clear targets and
motivations declaring that main
criterion was how far the surveillance was contributing to improve the
situation in animal and human populations. Strong vertically organized
government veterinary service, able to cope with so immense tasks, had the key
role in implementation of this highly demanding system. Modified multi-disease
surveillance system has continued also after recent reorganization of the
services when planned preventive investigations, financed by government, have
been carried out by private veterinarians. The study has showed that zoonoses
surveillance can be effective only when applying corresponding follow-up
practical measures and when represents integral component of diseases control
programs.
Reference
1. Annual
instructions for preventive actions planning. State Veterinary
Administration,
2. Kouba V. The surveillance system to control
food-born infections and
intoxications. World Health Organization, Document
VPH/Rome/WP/77.26, 1977.
3. Kouba V. General Epizootiology. University
of Veterinary Sciences, Kosice, 1994,
209 pp.
4. Raska K. The epidemiological surveillance
programme. J.Hyg.Epidem. (Praha), 8, 1964, 137- 168.
5. Statistical yearbooks. Ministry of Health,
6.
Statistical yearbooks. State Veterinary Administration,
7.
Zoonoses surveillance in