9th Symposium of the
International Society for Veterinary Epidemiology and Economics,
ISVEE 9 Proceedings
SUPPORTING ZOONOSES PREVENTION, REDUCTION AND
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.
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
* 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.
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.
instructions for preventive actions planning. State Veterinary
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,
Statistical yearbooks. State Veterinary Administration,
Zoonoses surveillance in