Diseases of Concern: BVD and Trichomoniasis Robert Mortimer, DVM Russell Daly, DVM Colorado State University South Dakota State University
The Epidemiologic Triad Host Management Agent Environment
Trichomoniasis From 1987-1990 Had over 50 positive herds in Colorado
Pregnancy rate Weaning weight Culling rate Replacement Rate Labor Veterinary Costs Trichomoniasis Economic Aspects
Trichomoniasis: ECONOMIC SIGNIFICANCE Calving Rate Difference 18.7% Primary Infection 90 days lost Secondary Infection 30 days lost Reinfection Rate 50%+ within 9 months Clark and Duffey. Aust. Vet J. 1983
Typical 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 Problem 2 Oper. Nonaffected cattle H Affected Cattle 2 Ops. 3 Operations Large Operation with put together cattle
Trichomoniasis Bull Pathogenesis Not affected by the disease Primary vectors Mechanical transmission Permanent carriers Age related
Organism Protozoa Trichomonas foetus Transmission is sexual only
Female Possibilities Breeding Not infected; Get pregnant; normal calving Infected, not pregnant, mount immunity finally Get pregnant Breeding Breeding Get pregnant, lose pregnancy, develop pyometra, Mount immunity, Ultimately rebreed and get pregnant Calving Infected, carry throughout pregnancy infected for up to 60 d + postpartum
Female 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
Trichomoniasis Diagnosis Preputial samples from bulls Cervical vagina mucus from infected cows Pyometra fluid from infected cows # 6- Absolute weakness is sampling technique
Diagnostic Methods Culture in tube or Pouch of Diamonds Media PCR Test
Diagnostic Challenges Age of bull Number of bulls Period of Sexual Rest
Number 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? Bull Age No Rest 20-28 day >85 days >100 days 1-2 year ------ 0/46 0/46 0/46 3 year 1/39 2.5% 4 year 6/22 27.3% 5+ Year 5/14 35.7% 3/42 12.2% 1/16 6.25% 2/9 22.2% 8/43 0/35 18.6% 3/15 0/12 20.0% 0/7 0/7
Regulatory 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 Control by Management
TREATMENT In the United States there are no drugs approved to treat bovine trichomoniasis in either bulls of cows
Control 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 Management Depopulation Best if only few cows pregnant Partial depopulation almost always used
Grazing Associations Control Can come ONLY IF RULES are established and followed by all involved
Grazing Associations Control Rules Screen all bulls Use only bulls < 4 years ONLY cows that calved and virgin heifers allowed on range
Grazing Associations Special Problems If any breeding done before association grazing SAME RULES MUST APPLY or use A.I.
Lease Bulls Rules All bulls tested REGARDLESS OF AGE 3 negative tests
What about vaccination? Vaccine for cow use only Vaccine will not prevent infection but may decrease severity Last resort option
Management Issues
What about BVD?
Etiological Agents BVD Pestivirus Virus Worldwide distribution Estimate serum antibody prevalence 50-90% in cattle
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 Cell Killing BVDV - 2 Phenotypes (Lab Characteristics) Noncytopathic (NCP) p 80/N53 is absent Considered the standard virus Accounts for >90% of infections Cause of persistent infections Dubovi, Comp. Imm. Inf. Dis. 15:155, 1992 Non Cell Killing
What causes a PI calf? Acute infectionpregnant female exposed to NCP BVDV 93% Persistently infected female giving birth 7% (Wittum, et al, Prev Vet Med 49 (2001) 83-94)
FETAL BVDV INFECTION infertility repeat breeding DURING GESTATION congenital defects immune response d 0 d 58 d 90 d 125 d 150 d 283 persistent infection abortion, weak or stillbirth
What about the bull? KNOWN: PI possibility Testes immunologically protected site BVDV shed semen Viral transmission and Infection 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 Herds Many animals in same stage of reproductive cycle especially stage of gestation Herd usually handled as a group
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 Positive Retain in Herd Adapted from: Kelling,et al,the Bov Pract, 34:1 (2000) 13-22 Calves Remove Positive Calves and Dams from Herd Prebreeding Bulls and Cattle without Calves Sell for Slaughter
Remove Positive Calves and Dams from Herd Prebreeding Sell positive calves for slaughter Positive Cow - PI calf product of PI cow Test Dams Negative Cow - PI calf from acute infection Adapted from: Kelling,et al,the Bov Pract, 34:1 (2000) 13-22 Sell for slaughter Only cow may return to herd
BVD Vaccination May be prevented with well planned vaccination program Look at fetal protection information (not 100%)