Diseases of Concern:Diseases of Concern: BVD and BVD and TrichomoniasisTrichomoniasis

Robert Mortimer, DVMRobert Mortimer, DVMRussell Daly, DVMRussell Daly, DVM

Colorado State UniversityColorado State UniversitySouth Dakota State UniversitySouth Dakota State University

Host

EnvironmentAgent

Management

The Epidemiologic Triad The Epidemiologic Triad

TrichomoniasisTrichomoniasis

From 1987-1990 Had over 50 positive herds in Colorado

TrichomoniasisTrichomoniasis Economic AspectsEconomic Aspects

• Pregnancy rate• Weaning weight• Culling rate• Replacement Rate• Labor• Veterinary Costs

Calving RateCalving Rate Difference 18.7%Difference 18.7%

Primary Infection 90 days lostPrimary Infection 90 days lostSecondary Infection 30 days lostSecondary Infection 30 days lostReinfectionReinfection Rate 50%+ within 9 Rate 50%+ within 9

monthsmonths

Trichomoniasis: ECONOMICSIGNIFICANCE

Clark and Duffey. Aust. Vet J. 1983

Typical HistoryTypical History

• Pregnancy Rates may be decreased by10- 50%– Function of size of herd, length of breeding

season, time of pregnancy diagnosis• Increased losses of pregnancy• Usually with additional information it is

determined that the disease actually entered the herd a year ahead of owner concern for a problem

Herd ProblemHerd Problem

H

Affected Cattle

3 Operations

2 Oper.

Nonaffected cattle

Large Operation with put together cattle

2Ops.

TrichomoniasisTrichomoniasis Bull PathogenesisBull Pathogenesis

• Not affected by the disease• Primary vectors• Mechanical transmission• Permanent carriers

– Age related

OrganismOrganism

• Protozoa– Trichomonas foetus

• Transmission is sexual only

Female PossibilitiesFemale PossibilitiesNot infected; Get pregnant; normal calvingBreeding

Infected, not pregnant, mount immunity finallyGet pregnant

Breeding

Get pregnant, lose pregnancy, develop pyometra, Mount immunity, Ultimately rebreed and get pregnant

Breeding Calving

Infected, carry throughout pregnancy infected for up to 60 d + postpartum

Female Risk FactorsFemale Risk Factors

• Most cows will clear themselves of the infection within 120 days but not all.

• Some cows can carry through pregnancy and be infective for 60 days pp

TrichomoniasisTrichomoniasis DiagnosisDiagnosis

• Preputial samples from bulls• Cervical vagina mucus from infected cows• Pyometra fluid from infected cows

# 6- Absolute weakness is sampling technique

Diagnostic MethodsDiagnostic Methods

• Culture in tube or Pouch of Diamonds Media

• PCR Test

Diagnostic ChallengesDiagnostic Challenges

Age of bull

Period of Sexual Rest

Number of bulls

Number of bullsNumber of bulls

• <10 bulls• 10-30 bulls• >30 bulls

• Three test• 2 tests• 1 test

Once diagnosis been made in the herd we test until we have at least 3 negative Tests

How much sexual rest?How much sexual rest?Bull Age

No Rest 20-28 day

>85 days

>100 days

1-2 year ------ 0/46 0/46 0/46

3 year 1/392.5%

3/4212.2%

8/4318.6%

0/35

4 year 6/22 27.3%

1/166.25%

3/1520.0%

0/12

5+ Year 5/1435.7%

2/922.2%

0/7 0/7

Regulatory ProgramsRegulatory Programs

• States w/programs– AZ, CO, NM, NV, ID,

UT, WY, NE, SD, ND, CA

• Weaknesses– Period of sexual rest– # tests required– May not cover female

at all.

Don’t rely on state programs to keep you free from the disease. Develop and

maintain your own Biosecurity program

Prevention and Prevention and Control by Control by

ManagementManagement

TREATMENTTREATMENT

• In the United States there are no drugs approved to treat bovine trichomoniasis in either bulls of cows

Control by ManagementControl by Management

• Only virgin animals or animals free of exposure enter noninfected herd–Allow ample time after calving

before bull exposure• Artificial Insemination

–Reputable source

Control by ManagementControl by Management DepopulationDepopulation

• Best if only few cows pregnant

• Partial depopulation almost always used

Grazing AssociationsGrazing Associations ControlControl

• Can come ONLY IF RULES are established and followed by all involved

Grazing AssociationsGrazing Associations Control RulesControl Rules

• Screen all bulls• Use only bulls < 4 years• ONLY cows that calved

and virgin heifers allowed on range

Grazing AssociationsGrazing Associations Special ProblemsSpecial Problems

• If any breeding done before association grazing SAME RULES MUST APPLY or use A.I.

Lease BullsLease Bulls RulesRules

• All bulls tested REGARDLESS OF AGE

• 3 negative tests

What about vaccination?What about vaccination?

• Vaccine for cow use only• Vaccine will not prevent infection but may

decrease severity• Last resort option

Management IssuesManagement Issues

What about BVD?What about BVD?

Etiological AgentsEtiological Agents

• BVD – Pestivirus Virus– Worldwide distribution– Estimate serum antibody prevalence 50-90%

in cattle

BVDV BVDV -- 2 Phenotypes2 Phenotypes (Lab Characteristics)(Lab Characteristics)

• Cytopathic (CP)– Expression of p 80/N53

in BVD infected cells– Correlates with induction

of cytopathic changes in cells

Donis & Dubovi, Virology 158:168, 1987

• Noncytopathic (NCP)– p 80/N53 is absent– Considered the

“standard” virus– Accounts for >90% of

infections

– “Cause” of persistent infectionsDubovi, Comp. Imm. Inf. Dis.

15:155, 1992Cell Killing Non Cell

Killing

What causes a PI calf?What causes a PI calf?AcuteAcute infectioninfection-pregnant female

exposed to NCP BVDV

93%

Persistently infectedPersistently infectedfemale giving birthfemale giving birth

7%7%

(Wittum, et al, Prev Vet Med 49 (2001) 83-94)

FETAL BVDV INFECTION FETAL BVDV INFECTION DURING GESTATIONDURING GESTATION

persistent infection

abortion, weak or stillbirth

infertility congenital defectsrepeat breeding

immune responsed 0 d 283d 125 d 150d 58 d 90

What about the bull?What about the bull?KNOWN:•PI possibility•Testes immunologically protected site•BVDV shed semen•Viral transmission andInfection can occur

Can this result in development of a PI calf? Rare! Single study, frozen semen from a known PI bull used in 12 susceptible heifers resulted in all being pregnant, all infected, and 1 of the 12 was a PI calf. Meyling and Jensen. Veterinary Microbiology 17: 97-105. 1988.

What does this mean relative to natural service???

Beef Cow HerdsBeef Cow Herds

• Many animals in same stage of reproductive cycle– especially stage of gestation

• Herd usually handled as a group

TAKE HOME MESSAGE!TAKE HOME MESSAGE!

• All herds should have monitoring/surveillance plan

• Plan should be put in place for monitoring herd additions

• In high risk herds, have a PI eradication plan

Beef Cattle - Prebreeding Test of Calves, Bulls, Cattle without Calves

Negative

Retain in Herd

Positive

Sell for Slaughter

Bulls and Cattle without

CalvesRemove Positive Calves and Dams

from Herd Prebreeding

Calves

Adapted from:Kelling,et al,The Bov Pract, 34:1 (2000) 13-22

Remove Positive Calves and Dams from Herd Prebreeding

Sell positive calves for slaughter

Test Dams

Positive Cow - PI calf product

of PI cow

Sell for slaughter

Only cow may return to herd

Negative Cow - PI calf from

acute infection

Adapted from:Kelling,et al,The Bov Pract, 34:1 (2000) 13-22

BVD VaccinationBVD Vaccination

• May be prevented with well planned vaccination program

• Look at fetal protection information (not 100%)