Brucellosis Epidemiological Surveillance System in Animal Health Sector

Brucellosis Epidemiological Surveillance System in Animal Health Sector By Prof. Dr. Mohamed Refai Faculty of Veterinary Medicine, Cairo University, Giza, Egypt Tel: 33806554, 0105187590, E-mail mohrefai@yahoo. com

Points to be discussed in this lecture: n n Definition of surveillence system Objectives of surveillence system Means and tools for the control of brucellosis Evaluation and monitoring of the surveillence system

Epidemiological Surveillance * Epidemiological Surveillance is the ongoing and systematic collection, analysis and interpretation of healthrelated data * It involves describing and monitoring health events in populations of animals and humans

Surveillance System A surveillance System is a set of activities, institutions, facilities and procedures • to conduct, analyze, transfer, and diffuse information • for planning, management, and evaluation of activities in a given field, sector, services, etc. *i. e. a surveillance system is designed for decisionmaking

Surveillance System n n activities : herd-visits, serological tests, vaccination, etc institutions : local vet. units, laboratories, data processing centers, etc facilities : vehicles, computers, faxes etc. procedures : filling of forms, data storage, data processing, analysis and transfer

Epidemiological Surveillance System provides answers to the following questions n n n n When infection occurred? Where infection occurred? What is the source of infection? What is the mode of transmission? How extensive is the infection? Is the prevalence and incidence increasing, decreasing or static? Which animal species is/are involved? What species of Brucella are involved? , etc.

Challenges in designing surveillance programme for brucellosis n n n The infection is chronic Symptoms and I. p. are variable Laboratory confirmation is essential Lack of animal identification Poor movement control, etc.

Designing and operating brucellosis surveillance system The following points should be considered: 1. Identifying indicators of human and animal health events 2. Establishing clearly defined objectives 3. Developing specific case definition 4. Identifying existing data sources or develop new data collection systems, including a flow chart 5. Defining role of laboratories 6. Analysing and interpreting data 7. Developing dissemination methods 8. Evaluating the surveillance system

Designing and operating brucellosis surveillance system n n n 1. Identify indicators of human and animal health events Numerical: e. g. number of known infected herds Ratios: e. g. number of newly identified herds in a year compared with that of previous year Rates (percentages): number of infected herds divided by number of herds at risk Incidence (new cases) rate is preferred than prevalence (all cases) rates because it reflects better the dynamics of the disease

Designing and operating brucellosis surveillance system 2. Establish clearly defined objectives n Determination of the incidence and prevalence of infected humans, animals, herds, or group of animals, villages, regions, etc n Detection of epidemics and sporadic or endemic cases n Identification of modes and means of transmission to humans, or between animals n Monitoring of short- and long term trends by location and over time

Designing and operating brucellosis surveillance system 3. Develop specific case definition n In animals: using isolation and serology to place every herd or animal in one of 3 categories: positive, negative or uncertain n In man: using symptoms and signes + lab. Test to describe possible, probable or confirmed cases

Designing and operating brucellosis surveillance system 4. Identify existing data sources or develop new data collection systems, including a flow chart n Passive Surveillance System (monitoring) the routine mandated reports received by health or veterinary departments n Active Surveillance System the specific efforts made to supplement the passive data by use of directed investigations, surveys and epidemiological studies

Passive Surveillance System Data passively acquired from : n Abortion submissions to diagnostic lab. n Routine testing of on-farm animals, such as milk or blood n Notification from field veterinarians n Off-farm sampling from markets or slauhgterhouses All these data may be biased

Passive Surveillance System n n Advantages: * Generally less costly than active surveillance * Huge amounts of data are collected Disadvantages: * Its specificity and sensitivity are generally unknown * Data may be biased * Periodic evaluation of the system is needed

Active Surveillance System 3 approaches n n n 1. Total (census) testing efficient but costly 2. Random (probability-based) sampling, provides statistically reliable estimates 3. Non-random (purposive) sampling of suspected high-risk group likely to be biased

Random (probability-based) sampling n Simple Random Sampling, using tables or computer-generated numbers n Systematic Random Sampling, by selecting every nth animal, herd, village, etc n Stratified Random Sampling, by dividing population into sections e. g. owners, breeds, etc n Multistage Random Sampling, e. g. randomly selected herds, then randomly selected animals within a herd

Active Surveillance System n n Advantages: * The performance of the system is measurable and prederterminable Disadvantages: * Increased expenses involved * Limitation of only selected data

Which type of Surveillance System to be applied? Due to advantages in both ways n Passive collection is the main source of data n Active collection is suitable for ad hoc surveys, which are carried out to: * evaluate the performance of passive data collection * evaluate the need for implementation of a routine system for data collection

Sources of passive data collection n n n Peripheral public health services Peripheral veterinary services Hospitals Veterinary laboratories and clinics Physicians and veterinary practioners Universities International organizations

Sources of active data collection n Surveys for the presence or absence of the disease Surveys to prove that the disease is not present Surveys to establish the level of occurrence of the disease (prevalence)

Factors influencing Brucellosis Surveillance n n n Political and legal factors Financial and administration factors Culture, motivation and education factors Veterinary Services infrastrucure factors Intersectoral collaboration and cooperation

Factors to be considered in Designing a Surveillance System n n n n The major species of Brucella infecting man and animals in the country The current or baseline levels of infection in the primary animal reservoirs (prevalence) The units of observation (herd, village, etc. ) Test eligibale animals Type of livestock production, marketing and slaughter systems Information on animal numbers and identification Laboratory support and testing strategies Data recording system

Data recording systems for surveillance n n n n Herd, flock or village form Individual animal sample form Laboratory investigations form Abortion outbreak/incidence form Records of on-farm testing Records of off-farm testing Epidemiological investigation of reactor herd form

Control of brucellosis in animals 1. Prevention of exposure of animals to infection n 2. Rapid recognition of infected animals n 3. Measures to be taken in infected herds n 4. Vaccination n

2. Rapid recognition of infected animals *Abortion, if it occurs *Presence of the organism in the body by bacteriological examination of each abortion or premature birth *Presence of antibodies in diagnostic titres by regular serological testing of animals

Diagnosis of brucellosis *Accordingly, diagnosis depends on: 1. Isolation of Brucella which is conclusive if +, but not when 2. Detection of antibodies which is conclusive if - , but it is not 100% conclusive when +(false +, false -)

Isolation of brucellae n Isolation is the most definitive diagnosis when it is positive. n Failure to isolate the organism does not mean negative result.

Isolation failure may be due to: the viability and numbers of organisms in the sample n the nature of the sample, which is commonly contaminated. n

Serological Diagnosis of brucellosis Although the serological diagnosis is not 100% reliable when positive n It is the main tool for the rapid recognition of infected herd and individual animals n

A positive serology means: field strain infection n vaccination infection n residual vaccination titre n cross-reactivity with other organisms, like Yersinia, Salmonella, Pasteurella etc n human errors. n

Polymerase chain reaction (PCR) n n n PCR is particularly useful in case of tissues and fluids contaminated with nonviable or low numbers of Brucella organisms in diagnosis, It can detect Brucella DNA. A good sensitivity of PCR was reported by Fekete et al. (1990 a and 1990 b), Baily et al. (1992) and Da Costa et al. (1996).

Vaccination

Bang, 190 Natural infection gives life-long immunity This means the best immunity is achieved by using live vaccines

ATTENUATED BRUCELLA VACCINES n Brucella abortus Strain 19 Spontaneous loss of virulence n Brucella suis 2 by in-vitro transfer n Brucella melitensis Rev 1 Selective mutagenesis n Brucella abortus RB 51 through antibiotics

Brucella abortus Strain 19 (S 19) vaccine 1. It is Brucella abortus biovar 1 n 2. Can be smooth or rough n 3. Does not revert to virulence n 4. Rarely persists in the body for long n 5. Is not excreted n

Brucella melitensis Rev 1 vaccine (Elberg, 1955) n n Streptomycin independent variant of streptomycin-dependent mutant of B. melitensis biovar 1 Genetically stable Low virulence , good immunogenicity Effective protection in small ruminants

Vaccines through genetic engineering n aim : to produce alternative vaccines that are: * safe and * do not induce antibodies, which interfere with the serodiagnosis of field infection.

Brucella cell components acting as antigens n n n n 1. Purified extracts 2. Cell wall fractions 3. Lipopolysaccharide (LPS) 4. O-polysaccharides (OPS) 5. Outer membrane proteins (OMPs) * conserved in all Brucella species 6. Ribosomal fractions 7. DNA

Conclusion about Vaccines through genetic engineering n Subunit vaccines proved to be not effective in protecting animals from subsequent infection (Confer et al. , 1987 and Winter et al. , 1988).

The failure to obtain an effective subunit or recombinant monovalent Brucella vaccine n This problem is in great extent related to the antigen processing and presentation events which are rather complex (Schurig, 1994).

The failure to obtain an effective subunit or recombinant monovalent Brucella vaccine n Moreover, microorganisms do not express the same antigens at all times (Yura et al. , 1993). n This is why, the best immunity is commonly achieved by live microorganism.

A good, strong and long-lasting immunity against Brucella requires that: the vaccinal strain persists a time longe enough in lymphoid organs to produce the desired immunity 1. 2. the vaccinal strain has a low but real residual virulence linked to ability to multiply and resist

Brucella abortus RB 51 * It is a laboratory-derived rough mutant of the virulent strain 2308 of Brucella abortus * Rifampin and penicillin resistant * It contains the same OMP as S 19 and S 2308

The genome sequence of Brucella melitensis strain 16 M contains 3, 294, 935 bp on 2 chromosomes: n 2, 117, 144 bp and 1, 177, 787 bp encoding 3, 197 ORFs. n 2, 487 (78%) ORFs were assigned functions n

Surveillance techniques /Stage of brucellosis control programm n n No or minimal efforts to control brucellosis Intensive vaccination phase of herds and flocks Test and removal, segregation or slaughter phase Freedom phase: herds, regions and countries

No or minimal efforts to control brucellosis n n n Voluntary investigation of abortion (passive) Sero-surveillance (active) Bacteriological and serological examination of tissues and blood from cattle of breeding age at markets or slaughter (active)

Intensive vaccination phase of herds and flocks n n Evaluate vaccination coverage, over 80% should be seropositive within 2 -3 w after vaccination Monitor abortion rate Monitor randomly selected herds by tests that distinguish between infected and vaccinated animals such as competitive ELISA Culture blood and tissue samples of randomly selected slaughtered animals

Test and removal, segregation or slaughter phase n n Use screening test for identifying infected herds Use confirmatory test for confirmation of cases Once infected herd has been identified, all testeligible animals should be tested: animals of 18 -20 m at 3 -6 m intervals Once incidence or prevalence rates decreased, start market and/or slaughterhouse testing with trace-back efforts

Freedom phase: herds, regions and countries n n n Periodical sero-surveillance No vaccination for at least the past 3 years All reactors are slaughtered Newly introduced animals officially free MRT and indirect ELISA are primary methods of surveillance for dairy herds n n Test prior and after movement Test adjacent herds

Evaluation of Brucellosis Surveillance System n n n Evaluate the brucellosis surveillance indicators Evaluate the overall system for simplicity, flexibility, acceptability, sensitivity, predictive value, representativeness and timeliness Evaluate the usefulness of information obtained by surveillance for actions taken by decisionmakers Evaluate the out-come in relation to objectives Evaluate conclusions and recommendations

Brucellosis Surveillance Indicators n n n Performance indicators incidence rates based on groups of animals is the most sensitive indicator for success or failure of a programme Resource indicators cost per test (serology, Bacteriology) cost for epidedmiological investigation cost per animal for vaccination Diagnostic indicators

Brucellosis Surveillance Indicators Diagnostic indicators n n n Number of complete herd test at monthly intervals needed to clear herds of infection Efficiency of trace-back procedures Number of culture-positive animals in relation to number of seropositive ones Number of serological tests in a herd Number of animals or herds vaccinated Mean quarantined period of a herd