Brucellosis Epidemiological Surveillance System in Animal Health Sector

1
Brucellosis Epidemiological Surveillance System
in Animal Health Sector

• By
• Prof. Dr. Mohamed Refai
• Faculty of Veterinary Medicine, Cairo University,
  Giza, Egypt
• Tel[phone], E-mail
  mohrefai_at_yahoo.com

2
Points to be discussed in this lecture

• Definition of surveillence system
• Objectives of surveillence system
• Means and tools for the control of brucellosis
• Evaluation and monitoring of the surveillence
  system

3
Epidemiological Surveillance

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

4
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
  decision-making

5
Surveillance System

• 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

6
Epidemiological Surveillance System provides
answers to the following questions

• 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.

7
Challenges in designing surveillance programme
for brucellosis

• The infection is chronic
• Symptoms and I.p. are variable
• Laboratory confirmation is essential
• Lack of animal identification
• Poor movement control, etc.

8
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

9
Designing and operating brucellosis surveillance
system

• 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

10
Designing and operating brucellosis surveillance
system

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

11
Designing and operating brucellosis surveillance
system

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

12
Designing and operating brucellosis surveillance
system

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

13
Passive Surveillance System

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

14
Passive Surveillance System

• 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

15
Active Surveillance System3 approaches

• 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

16
Random (probability-based) sampling

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

17
Active Surveillance System

• Advantages
• The performance of the system is
• measurable and prederterminable
• Disadvantages
• Increased expenses involved
• Limitation of only selected data

18
Which type of Surveillance System to be applied?

• Due to advantages in both ways
• Passive collection is the main source of data
• 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

19
Sources of passive data collection

• Peripheral public health services
• Peripheral veterinary services
• Hospitals
• Veterinary laboratories and clinics
• Physicians and veterinary practioners
• Universities
• International organizations

20
Sources of active data collection

• 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)

21
Factors influencing Brucellosis Surveillance

• Political and legal factors
• Financial and administration factors
• Culture, motivation and education factors
• Veterinary Services infrastrucure factors
• Intersectoral collaboration and cooperation

22
Factors to be considered in Designing a
Surveillance System

• 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

23
Data recording systems for surveillance

• 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

24
Control of brucellosis in animals

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

25
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

26
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 -)

27
Isolation of brucellae

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

28
Isolation failure may be due to

• the viability and numbers of organisms in the
  sample
• the nature of the sample, which
• is commonly contaminated.

29
Serological Diagnosis of brucellosis

• Although the serological diagnosis is not 100
  reliable when positive
• It is the main tool for the rapid recognition of
  infected herd and individual animals

30
A positive serology means

• field strain infection
• vaccination infection
• residual vaccination titre
• cross-reactivity with other organisms, like
  Yersinia, Salmonella, Pasteurella etc
• human errors.

31
Polymerase chain reaction (PCR)

• PCR is particularly useful in case of tissues and
  fluids contaminated with non-viable 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 1990b), Baily et al. (1992)
  and Da Costa et al. (1996).

32
Vaccination
33
Bang, 190
Natural infection gives life-long immunity This
means the best immunity is achieved by using live
vaccines
34
ATTENUATED BRUCELLA VACCINES

• Brucella abortus Strain 19
• Spontaneous loss of virulence
• Brucella suis 2
• by in-vitro transfer
• Brucella melitensis Rev 1
• Selective mutagenesis
• Brucella abortus RB51
• through antibiotics

35
Brucella abortus Strain 19 (S19) vaccine

• 1. It is Brucella abortus biovar 1
• 2. Can be smooth or rough
• 3. Does not revert to virulence
• 4. Rarely persists in the body for long
• 5. Is not excreted

36
Brucella melitensis Rev 1 vaccine (Elberg,1955)

• Streptomycin independent variant of
  streptomycin-dependent mutant of B. melitensis
  biovar 1
• Genetically stable
• Low virulence , good immunogenicity
• Effective protection in small ruminants

37
Vaccines through genetic engineering

• aim to produce alternative vaccines that are
• safe and
• do not induce antibodies,
• which interfere with the serodiagnosis of
  field infection.

38
Brucella cell components acting as antigens 

• 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

39
Conclusion about Vaccines through genetic
engineering

• Subunit vaccines proved to be not effective in
  protecting animals from subsequent infection
• (Confer et al., 1987 and Winter et al., 1988).

40
The failure to obtain an effective subunit or
recombinant monovalent Brucella vaccine

• This problem is in great extent related to the
  antigen processing and presentation events which
  are rather complex
• (Schurig, 1994).

41
The failure to obtain an effective subunit or
recombinant monovalent Brucella vaccine

• Moreover, microorganisms do not express the same
  antigens at all times
• (Yura et al., 1993).
• This is why, the best immunity is commonly
  achieved by live microorganism.

42
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
• 2. the vaccinal strain has a low but real
  residual virulence linked to ability to multiply
  and resist

43
(No Transcript)
44
Brucella abortus RB51

• 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 S19 and S2308

45
The genome sequence of Brucella melitensis strain
16M

• contains 3,294,935 bp on 2 chromosomes
• 2,117,144 bp and 1,177,787 bp encoding 3,197
  ORFs.
• 2,487 (78) ORFs were assigned functions

46
Surveillance techniques /Stage of brucellosis
control programm

• 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

47
No or minimal efforts to control brucellosis

• 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)

48
Intensive vaccination phase of herds and flocks

• 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

49
Test and removal, segregation or slaughter phase

• Use screening test for identifying infected herds
• Use confirmatory test for confirmation of cases
• Once infected herd has been identified, all
  test-eligible 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

50
Freedom phase herds, regions and countries

• 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
• Test prior and after movement
• Test adjacent herds

51
Evaluation of Brucellosis Surveillance System

• 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
  decision-makers
• Evaluate the out-come in relation to objectives
• Evaluate conclusions and recommendations

52
Brucellosis Surveillance Indicators

• 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

53
Brucellosis Surveillance Indicators Diagnostic
indicators

• 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

54
???? ??? ??? ????????

• Thank you for your attention