Diseases of concern: BVD and Trichomoniasis
Transcript of Diseases of concern: BVD and Trichomoniasis
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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
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Host
EnvironmentAgent
Management
The Epidemiologic Triad The Epidemiologic Triad
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TrichomoniasisTrichomoniasis
From 1987-1990 Had over 50 positive herds in Colorado
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TrichomoniasisTrichomoniasis Economic AspectsEconomic Aspects
• Pregnancy rate• Weaning weight• Culling rate• Replacement Rate• Labor• Veterinary Costs
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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
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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
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Herd ProblemHerd Problem
H
Affected Cattle
3 Operations
2 Oper.
Nonaffected cattle
Large Operation with put together cattle
2Ops.
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TrichomoniasisTrichomoniasis Bull PathogenesisBull Pathogenesis
• Not affected by the disease• Primary vectors• Mechanical transmission• Permanent carriers
– Age related
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OrganismOrganism
• Protozoa– Trichomonas foetus
• Transmission is sexual only
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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
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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
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TrichomoniasisTrichomoniasis DiagnosisDiagnosis
• Preputial samples from bulls• Cervical vagina mucus from infected cows• Pyometra fluid from infected cows
# 6- Absolute weakness is sampling technique
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Diagnostic MethodsDiagnostic Methods
• Culture in tube or Pouch of Diamonds Media
• PCR Test
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Diagnostic ChallengesDiagnostic Challenges
Age of bull
Period of Sexual Rest
Number of bulls
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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
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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
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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
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Prevention and Prevention and Control by Control by
ManagementManagement
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TREATMENTTREATMENT
• In the United States there are no drugs approved to treat bovine trichomoniasis in either bulls of cows
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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
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Control by ManagementControl by Management DepopulationDepopulation
• Best if only few cows pregnant
• Partial depopulation almost always used
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Grazing AssociationsGrazing Associations ControlControl
• Can come ONLY IF RULES are established and followed by all involved
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Grazing AssociationsGrazing Associations Control RulesControl Rules
• Screen all bulls• Use only bulls < 4 years• ONLY cows that calved
and virgin heifers allowed on range
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Grazing AssociationsGrazing Associations Special ProblemsSpecial Problems
• If any breeding done before association grazing SAME RULES MUST APPLY or use A.I.
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Lease BullsLease Bulls RulesRules
• All bulls tested REGARDLESS OF AGE
• 3 negative tests
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What about vaccination?What about vaccination?
• Vaccine for cow use only• Vaccine will not prevent infection but may
decrease severity• Last resort option
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Management IssuesManagement Issues
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What about BVD?What about BVD?
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Etiological AgentsEtiological Agents
• BVD – Pestivirus Virus– Worldwide distribution– Estimate serum antibody prevalence 50-90%
in cattle
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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
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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)
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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
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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???
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Beef Cow HerdsBeef Cow Herds
• Many animals in same stage of reproductive cycle– especially stage of gestation
• Herd usually handled as a group
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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
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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
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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
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BVD VaccinationBVD Vaccination
• May be prevented with well planned vaccination program
• Look at fetal protection information (not 100%)