Bovine Virus Diarrhea Virus Jessica Seate LCS 630 Rotation
BVD is currently one of the most costly diseases of cattle. Cost estimates in herds with BVD range from $24 to $200 per cow per year. BVDV, What is that?? Bovine viral diarrhea virus (BVDV) is a single stranded RNA virus that is a member of the family Flaviviridae and is of the genus Pestivirus. It is related to classical swine fever in swine and border disease in ovine. BVDV was first identified in cattle 1946 and initially thought to be a gastro-intestinal disease, however, today it is primarily associated with reproductive problems BVDV has two biotypes: non-cytopathic (NCP) and cytopathic (CP) (defined by the growth characteristics of the virus in cell culture). The predominant biotype is the non-cytopathic BVDV is also divided into two genotypes: BVDV type 1 and BVDV type 2, based on the antigenic and genetic differences. Both genotypes are capable of causing severe disease and containing both the CP and NCP forms. Diseases related to BVDV cause economic losses to cattle producers throughout the world due to: decreased performance loss of milk production reproductive wastage increased risk of morbidity and mortality
Transmission Horizontal Transplacental Direct contact with body fluids from PI cattle. Virus has been isolated from nasal swabs, aerosols, saliva, urine, feces, semen, and uterine fluids from PI cattle. Introduction of an acutely infected animal or pregnant animal carrying a PI fetus Fence contact, communal pastures, and shows/exhibits Contaminated instruments Animal caretakers VERY EFFICIENT Can result in persistently infected calf
Factors influencing pathogenesis: pregnancy status gestational age of the fetus at time of infection immune status (passive or active from natural exposure or vaccination) concurrent level of environmental stress at the time of infection genetic diversity antigenic variation differences in virulence among BVDV isolates
The BVDV complex can result in subclinical benign bovine viral diarrhea, fatal mucosal disease, peracute fatal diarrhea, immune suppression, thrombocytopenia and hemorrhagic disease, reproductive failure, and congenital abnormalities in calves For this presentation, BVDV infections fall into three broad types: acute infection, fetal infection, and persistent infection (PI).
Acute Infection of Neonates Associated with failure of passive transfer Clinical Presentation: enteritis and pneumonia cough cough
Acute Infection of Calves at 6-24 months in age Most acute BVDV infections are subclinical (70 to 90 % of infections) in nature, resulting only in mild fever, leucopenia, inappetence, depression, and the development of antibodies. These infections often go undetected and usually last only a couple of days. Incubation period of the virus is 5-7 days Clinical Presentation: fever, leucopenia, depression, anorexia, oculonasal discharge, oral erosions, ulcerations, diarrhea, decreased milk production Acute infections can cause impairment of the immune system giving opportunities to secondary infections. Viremia lasting 2-5 days, possibly two weeks
Severe Acute Infection Acute course with high morbidity and substantial mortality (10-20%) Clinical Presentation: fever, pneumonia, ulcerations, sudden death, abortions are common Respiratory Distress Esophageal Ulcerations Erosions of Peyer s Patches
Hemorrhagic Syndrome BVDV has an affinity for cells of the bone marrow (primarily the megakaryocytes): Results in: decreased platelets and bleeding disorders Clinical Presentation: epistaxis, bloody diarrhea and vomit, hemorrhages of mucosal surfaces, pyrexia, leucopenia HIGHLY FATAL!!
Bovine Respiratory Disease Complex Since BVDV is a lymphotrophic virus and can induce immunosuppression it plays an important role in the bovine respiratory disease complex ( shipping fever ) in feedlots. It potentiates infections by now allowing other pathogens (BRSV, M. hemolytica) to cause effect that normally would not be able to do so alone.
Torticolli, wide stance, ataxia if born alive Developmental defects (100-150days of gestation) cerebellar hypoplasia or aplasia cleft palate hypotrichosis hydrocephalus Retinal atrophy, cataracts, microophthalmia
Persistent Infection Regardless of their prevalence, PI animals are typically the largest source of infection in any given herd Infection of the fetus during the first trimester (50-125 days) can result in the birth of an animal that is persistently infected (PI) with BVD. Takes about five months in utero for the immune system to react, before that calves are immunotolerant. Carries the virus for life Sheds loads of BVD virus in all secretions and excretions Level of virus being shed is HIGH PI animals are sickly since the infection can impair their normal immune function and end up being culled or dying before reaching adulthood PI animals are the means by which BVDV is maintained in the bovine population. Important to identify these PI calves after birth by observation or screening and eliminating the PI calf and mom from the herd **Death rate of PI calves is 50% during 1st year of life **Fewer than 10% of PI dairy replacement heifers reach lactating herd
Acute Mucosal Disease Clinical Signs: severe bloody diarrhea, erosions of gums, hard palate lesions, tongue lesions, esophageal ulcers, hyperemia of rumen and abomasum, lymphoid depletion of thymus and spleen, decreased milk production, fever, anorexia, secondary infections leading to pneumonia, mastitis, metritis Mucosal Disease Eye Opener for indicating BVDV is circulating in a herd Calf is infected in utero by a non-cytopathic strain during 50-125 days of gestation The non-cytopathic strain transforms into a cytopathic variant of that strain Chronic Mucosal Disease ** NCP and CP strains are less closely related as they are in acute mucosal disease Clinical Signs: lameness, interdigital necrosis, immunologically compromised, SEVERE emaciation, secondary bacterial infections High Mortality Short Disease Course of 3-10 days Usually Fatal
Virus Isolation Testing/Diagnostics Tissue, whole blood, serum Antibody Detection tests Serum Neutralization Nucleic Acid Detection PCR testing Antigen Detection tests BVDV Ear Notch Sampling: by far the most common diagnostic sample in calves less than 3 months of age for persistent infection (perform either IHC, ACE, or PCR) fluorescent antibody test (frozen tissues) immunoperoxidase test (formalin fixed tissues) **The choice of test depends on the current clinical problem and on the past test data from the herd or animal.
Tests Available BVDV Tests Offered by Cornell Diagnostic Laboratory 1. Bovine Viral Diarrhea Immunohistochemistry (IHC) test 2. Bovine Viral Diarrhea Serum Isolation (with IHC detection) 3. Bovine Viral Diarrhea Fluorescent Antibody test (FA) 4. Bovine Viral Diarrhea Virus Isolation 5. Bovine Viral Diarrhea Virus Serum Neutralization test (SN) 6. Bovine Viral Diarrhea Serum Isolation 7. Bovine Viral Diarrhea Whole Blood Isolation 8. PCR Detection Using (Bulk) Milk Samples 9. Bovine Viral Diarrhea Antigen Capture ELISA test [ACE](serum) 10. Bovine Viral Diarrhea Antigen Capture ELISA test [ACE](skin) 11. Pooled PCR testing for herd screening 12. BVDV PCR test Any combination of these tests are appropriate for multiple circumstances. For instance if there is a suspected Chronic BVD case, Found dead animal with suggestive lesions, Possible PI in herd, Cattle with sporadic abortions and poor reproductive performance, and even for animals that are being shipped for AI purposes.
Treatment/Prevention Animals persistently infected with BVDV are an important target for control of transmission Strategic management of the production system, diagnostic investigation, vaccination., herd-monitoring, biosecurity and biocontainment programs. Each management program will need to involve multiple components and customized to fit the goals and capabilities of each producer. As treatment infected animals is not a viable option: the control, prevention, and future eradication efforts for this disease must be implemented by the cow-calf industry and by individual dairy barns
Cows and heifers need to be well protected during FIRST TRIMESTER of pregnancy. Recommend vaccination of cows and heifers with a modified-live BVD vaccine a few weeks before breeding for adequate protection during early pregnancy. Or...a killed vaccines can be administered to all animals, semi-annually. Killed vaccines must be administered twice (two to four weeks apart) if the animal is being vaccinated for the first time (i.e. heifers). Without the booster vaccination, animals are not protected against BVD, even if they receive annual revaccinations with the killed product
Bovine Viral Diarrhea Control Procedures/Protocol 1. Implement an effective immunization program a. Vaccinate heifers initially with a modified-live BVD vaccine b. Booster in 2-4 weeks with a modified-live or killed BVD product c. Booster annually (MLV to open animals only), or semi-annually (killed). d. Depending on vaccination history, all purchased animals should be vaccinated against BVD at least once, and possibly twice. e. Store and handle all vaccines according to label recommendations 2. Maintain a closed herd if possible. 3. If expanding, purchase replacements from a local grower practicing good animal husbandry. Isolation of new additions for minimum of three weeks. 4. Test all purchased animals for BVD persistent infection (PI) status.
Protocol Continued 5. Test all replacements for BVD PI status either before colostrum feeding or at 3-4 months of age. 6. Cull any PI animal and its offspring. 7. Prevent disease entry into the herd by a. Isolating all animals entering the facility (replacements, bulls, and animals returning from shows or contractual raising) for two weeks. b. Requiring clean boots, clothing, and equipment for people and employees entering the premises. c. Moving dead and down cows away from the facility prior to pickup. d. Moving animals with your own truck, or at least insisting on a clean truck moving only your animals. e. Purchasing semen from AI establishments with active BVD screening procedures.
Differentials Acute Infection of 6-24 months: Salmonella Winter dysentery Johne s Disease Malignant Catarrhal Fever Vesicular Stomatitis FMD Bluetongue Intestinal parasites Arsenic poisoning Acute Infection of Neonates: Rotavirus Corona virus Cryptosporidium E.Coli Salmonellosis BRSV Pasteurellosis Coccidiosis Hemophilosis Mycoplasma Severe Acute Infection: Mucosal Disease
References: Baker, JC. (1995) The clinical manifestations of bovine viral diarrhea infection. Vet Clin North Am Food Anim Pract. 13(3):425-54. Brook, K.V. (2004) Strategies for the control and prevention of bovine viral diarrhea virus. Vet Clin Food Anim. 20:171-180. Campbell, J.R. (2004) Effect of bovine diarrhea virus in the feedlot. Vet. Clin. North. Am. Food Anim. Pract. 20(1):39-50. Grooms, DL. (2009) Integrated BVD Control Plans for Beef Operations. The Bovine Practitioner 43(2): 106-116. Dr. Maes Virology Notes MMG 565 Merck Veterinary Manual Ninth Ed. Merck & Co., Inc. 2005: 220-222 Smith, BP. Large Animal Internal Medicine. 4 th ed. Elsevier Inc. 2009: 610-611