BRUCELLOSIS SURVEILLANCE

An Overview:Primary SurveillanceSecondary SurveillanceActive SurveillancePassive surveillance

Brucellosis Surveillance SystemInfected herds may not readily enter into the surveillance system, resulting in long term undetected infection.Why not?selling only non-test eligible cattle through the livestock markets.sales through livestock markets of Brucellosis exposed first calf heifers in mid-term pregnancy that are test negative.failure to do private change of ownership test.not consulting a veterinarian for abortion and reproductive problems.veterinarian not considering Brucellosis on list of rule-outs.incomplete epidemiological investigations.Inadequate action by state-federal personnel in handling adjacent, community, contact and epidemiologically traced herds.

Brucellosis Primary Surveillance Market Cattle Testing: Pros / ConsLarge numbers of cattle can be sampled.Best primary surveillance system we had for beef cattle.Samples are tested on site; immediate action taken.Stops movement of test positive animals and exposed.Can collect milk and tissues for culture.Quarantine can be issued without delay.Animal ID is recorded to facilitate tracing.Cattle movement and dealer activity can be monitored.successful in locating infected herds.Con more expensive than SLT, most states quit.

Market Cattle Identification (MCI):

Objective: ID for BR MKT / SLT SurveillanceA way to continuously monitor the U.S. adult breeding cattle population.The primary method of BR surveillance used in most states now is SLT surveillance.Provides a way to gather state, regional and national prevalence data.Provides the animal identification and record keeping components for tracebacks.Is cost effective when considering overall scope and range of applications.

MCI Slaughter SurveillanceMCI test cattle or bison at MKT/SLT:All cows and bulls 2 years of age and older must be officially identified at FPC.95 percent must have blood samples collected at slaughter to maintain status.90 percent of reactors must be traceable to herd of origin to maintain status.Measured on national report for status status (VS Form 4-1 Report)

MCI SurveillanceState status:Annual reports must include: The number of MCI tests (Market / Slaughter) The number of MCI reactors. The number of MCI reactors traced to herd of origin:1.that were tested (TTR)2.that were not tested (TTN)3.that were traced out-of-state (TOS)4.that were traced to known reactor herds (TRH).5.that were traced to dealers (TD) or feedlots (TF) Number of successful and unsuccessful traces.

MCI SurveillanceAnnual reports must include:A narrative description of epidemiologic surveillance investigations and results such as a.MCI investigations and results, including the number of MCI reactors that cannot be traced because of a lack of applied identification;b.MCI procedures and problems at each of the slaughter establishments that failed to collect blood samples from 95 percent of the cows and bulls 2 years of age and older during the reporting period.

Brucellosis Ring Test(BRT)

and the

Heat Inactivated Ring Test(HIRT)

BRT SurveillanceThe BRT was first introduced in 1937 by Fleischhauer and has been used in the Brucellosis Eradication since the 1950s.Is a simple rapid test designed to detect antibodies in milk.Is a very sensitive test.Vaccination status Seasonal changesStage of lactation Garbage bacteria

HIRTThe HIRT was developed in 1989 by Dr. Don Pietz as a means to improve the specificity of the BRT.

The laboratory procedure is similar to the BRT except that the milk sample is heated to 65 degrees Celsius for 30 minutes in a circulating water bath.

BRT/HIRT Surveillance IssuesThe infected cow(s) may not be included in the milk sample:dry cowsfresh cowsHerds can be missed in the BRT round collection:soured samplespatrons switching dairy markets

BRT/HIRT Surveillance ProblemsFalse Negative BRT/HIRT results:Improper handling of samplesProduction of antibodies there is a lag time between infection and the production of antibodies in milk.Local antibodies in the udder are not produced until the udder becomes infected, however udder infection does not always occur.

BRT/HIRT Surveillance ProblemsFalse Positive BRT/HIRT results:Mastitis problemsStrain 19Recent whole herd vaccination (i.e. Lepto or Vibrio)Seasonal effectsOther factors

UM&R Program UsesQualifying method for Certified Brucellosis-Free herd:For initial certification, a dairy herd must have a minimum of four consecutive Brucellosis Milk Surveillance Tests (BMST) conducted at intervals of 90 days or more, followed by a negative herd blood test conducted within 90 days after the last negative BMST.

UM&R Program UsesRe-qualifying method for Certified Brucellosis-Free herd:The dairy herd must already be certified under one of the two approved initial certifications methods, then

A dairy herd may recertify by conducting4 consecutive negative BMSTs at approx. intervals of 90 days, with the fourth test conducted within 60 days before the certification anniversary date.

UM&R Program RequirementsClass Free State:The BMST must be conducted at least two times per year at approximately six month intervals.A State may increase the frequency of BMSTs to achieve more effective surveillance.An epidemiologic investigation of all herds with suspicious BMST results must be conducted and an approved action plan must be developed within 15 days of the laboratory test date.Patron lists must be reviewed to ensure that all dairy herds producing commercial milk have been included in at least two BMST rounds per year.

UM&R Program RequirementsClass A State:The BMST must be conducted at least four times per year at approximately equal intervals.A State may increase the frequency of BMSTs to achieve more effective surveillance.An epidemiologic investigation of all herds with suspicious BMST results must be conducted and an approved action plan must be developed within 15 days of the laboratory test date.Patron lists must be reviewed to ensure that all dairy herds producing commercial milk have been included in at least two BMST rounds per year.

VS Memorandum 551.27Subject: Increasing the sensitivity of the BRT

The purpose of this memo is to provide guidelines for increasing the sensitivity of the BRT.

Such an adjustment is necessary to compensate for the dilution factor in composite milk samples from large dairy herds.

By increasing the sensitivity of the BRT, the likelihood of detecting brucellosis recently introduced or maintained in chronic carrier animals is increased.

Brucellosis Milk Ring Test

Dairy herds are getting larger

BRT - The IssuesMeeting UM & R Requirements for sampling (2, 4 rounds/yr)Use of BRT / HIRT in large herdsShipment of milk across state lines and reporting of BRT results back to state of origin

General BRT IssuesUses of the BRTSurveillance of the nations dairy herdsFollow-up for MCI tracesCost effectiveness of BRT surveillanceMy general opinion: the goal BRT surveillance should be to detect an infected dairy herd prior to MCI surveillance, not just to collect the required number of rounds per year.

BRT / HIRT in large herdsThe UM&R protocol limited samples up to 700 cows.Alternate protocol California Modified BRT presented at 1997 USAHA meetingAdopted in 1986 in CA, data presented in 1997.Sampling up to 1500 head without significant loss in sensitivity.This method was included in UM &R in 1998.

The California BRT Method

Milk volume (ml)Lactating herd size (cows)1.06 - 150 1.5 151 - 2502.0251 - 3502.5351 - 5003.0 501 - 7003.5701 - 1,0004.0 1,001 - 1,5004.5 1,501 - 2,0005.0 > 2,000

California method (contd)Sensitivity = 96%, Specificity = 83%This analysis applies only to states conducting monthly BRT surveillance.Less frequent collection would decrease the sensitivity of the test.Number of false positives increases over 1500 head (4 cc)My experience is that HIRT eliminates quite a few false positives.

Using BRT in Large HerdsBULKTANKBULKTANK2000 Cows2000 Cows

Using BRT in Large HerdsBULKTANKBULKTANK1000 Cows = 3.5 cc1000 Cows = 3.5 cc

Segmenting HerdsUsesIsolate positive pen on suspicious bulk tankDealing with large herds on routine surveillance and tracesMethodsLine tap (randomization not tested)Sequential sampling of bulk tankIssuesTime consuming & labor inefficientSanitary concerns with line tap

Out of state patrons / PUPsProducers who constantly change PUPs in more than one stateChance that collection could be missedIncreased office timeReporting issuesConsistent mechanism for reporting results back to states of origin has been lacking.Different & incompatible data systems used among states

DBEs need to maintain effective surveillance!Is your state conducting 2/4 rounds per year?Do you have any large dairy herds over 700 head in your state?May need to suggest more rounds per year on large dairies to maintain sensitive BRT surveillance.Are you seeing MCI traces to dairies without seeing positive BRTs first? If so, you need to look at your BRT testing system and change it.

Questions?Thank you!