CS: Underperformance and Infectious Dz Flashcards
Measures of beef performance?
- daily live weight gain (0.8kg/d, 1kg/d when weaning?)
- % in calf (>95%)
- more qualitative d/t block calving cf. dairy
- live calfs /no. cows put to bull (aim >95%, slightly cows cf. heifers)
- muscle: fat ration for grading carcasse
- involuntary culls
Measures dairy performance?
- calving interval (aim 365 or 400d ish)
- growth rate (0.7kg/d)
- milk yield (~7,500l/cow/year average)
Diseases affecting performance?
> biggest - mastitis - lameness > also - lepto - IBR - BVD - Neospora - Salmonella - Campy - Endometritis - TB - E. Coli - Johnes (^ prevalence) - SARA - Fatty liver/pregnany toxaemia
Assessnig presence endemic dz
- Bulk milk tank sampling (Brucellosis serology also, mastitis cell count, low fat for SARA)
- CMT
- observation (lameness etc.)
- intradermal (eg. TB)
> check different age groups (if + serology only present older cows likely historic infection rather than active)
-
How can disease be avoided?
- vax and isolate new stock
How do different Johnes tests differ in sense and spec?
- milk higher sensitivity as threshold for + outcome lowered (cf blood)
Effects of Neospora caninum ?
> losses d/t - v post weaning weight - v milk yield - premature culling - ABORTION > signs - often none - early embreyonic death (if infected
How is neospora caninum transmitted?
- vertical and horizontal
> vertical - parasite migration during pregnancy to foetus from PI dams
- will affect several generations and successive pregnancies
> horizontal - dogs IH, cows ingest oocysts from feaces
- CAN BECOME pi
Dx neospora caninum?
- histopath on aborted foetuses
- serology of dam or calf (if calf + assume dam also +, but PI animals Ab levels fluctuate so can get false -ves: Better test needed if trying to eradicate dz or maintain free herd
- PCR/IHC to differentiate from other protozoa on histo
Is there a vax for neospora? Control/prevention?
- not currently
- cull infected cattle
- breed seronegative stock
- consider embryo transfer for infected stock high genetic merit
- dogs away from farm
- biosecurity at calving, dispose of placentas and aborted material
Clinical effects of BVDV
- infertility (abortions/stillbirths/mummification)
- birth defects (weak sickly calves, neuro signs)
- ill thrift and stunted growth
- poor condition
- IMMUNOCOMPROMISE -> 2* infection; esp scours and pneumonia
- v milk yield
- mucosal dz if cytopathic form mutates (6-18mo)
- Better groups list **
- Naïve, non-pregnant, immunocompetent: no CS in 70-90%
- Acute: fever, lethargy, anorexic, ocular discharge, nasal discharge, oral lesions, diarrhoea, reduced milk yield
- Chronic: mucosal disease.
- In-utero infection: abortions, congenital defects (cerebellar hypoplasia) weak, small calves, unthrifty PI calves.
Tests for IDing presence BVDV?
- Ab ELISA to see exposure of herd (bulk milk or bloods)
- PIs Antigen/viral RNA/virus isolation hunt: bulk milk or young stock bloods or ear notch 2 samples 3wks apart
How can BVD potentially be eradicated on farm?
- eradicate PI reservoir
- vax all breeding females to prevent new PIs born (killed vax so 2 jabs needed, ensure well before 1st service eg. yearlings)
- booster each service
- with active infection may need to vax other stages +- dam few weeks before calving to ^ colostrol abs
- continue bloodm onitoring 12mo after last PI identified
- purchase animals from BVDV free herds or quarantine 1m and blood test
- isolate cows bought in calf until parturition then screen calves PI (trojan mother poss with variable ab titre but no active infection despite PI calf)
- prevent contact with neighbouring farms using double perimeter fence
What can interfere with testing calves?
- MDA
- blood sample pre-colostrum or >4mo
How else may BVDV be spread
semen
- PI bulls
- check semen before AI (not allowed to sell AI semen from BVD+ bulls but if DIY be careful)
Diseases affected performance by type of pathogen
> Bacteria: Mastitis (S Aureus), TB, Johne’s, metritis, leptospirosis, pneumonia in calves (growth stunt)
Prions: BSE
Viruses: BVDV, Rotavirus, FMDV, BTV, IBR(not so common but nasty outbreaks),
Protozoa: Coccidia, Neospora (causes abortions)
Parasites: Ostertagia (affects growth of young stock), Fluke (affects young and older animals)
Metabolic: SARA, ketosis, milk fever, hypomagnesia
Which diseases have greatest economic impact on farm?
- IBR
- Lepto
- BVD
overview of IBR
- causes range of dz
- very infectious
- life-long latency ni trigem ganglia
- recrudescence poss
Most common linical signs of IBR
> Rhinotracheitis
- Most common disease caused by a BoHV-1 infection
- Can also cause reproductive (infectious pustular balanoposthitis/infectious pustular vulvovaginitis) , nervous (typucally calves
Is viraemia detectable with IBR?
No - virus excreted from mucosal surfaces
Dx IBR?
>Serology Ab detected 2-6 weeks post infection Highest during early clinical signs - isolate seronegatvies and breed, snatch calves from sero+ and test >Virus neutralisation – collect 1 sample then 2nd 4w later ELISA DIVA vaccines available Virus isolation Nasal / vaginal swabs Sperm sample Tissue sample – dead / aborted animals Needs to be collected during acute disease – as latent >Bulk milk tank Serology PCR
Biosecurity associated with protecting a herd from IBR
> Buying in infected animals is the most common source of infection
- Buy from disease free herds
- Quaratine & test new animals before mixing into herd
Remove seropositive animals
Vaccines (DIVA)
- just preweaning can alleviate all clinical forms of IBR
- MLV IM (feedlot cattle, can cause abortion)
- MLV intranasal (can be used in outbreaks, does not cause abortions or interfere with passive immunity), inactivated, killed
4-6 months old
Biosecurity
Foot baths for staff
Gloves when handling infected cows
Prevent proximity of infected and non-infected animals
Oronasal spread
Indirect spread
Contaminated semen
Embryo transfer
Humans
Contaminated materials
Airborne transmission
Eradicating IBR
> No direct tx Isolate NSAIDs > Carrier cattle should be identified and culled > Vaccination DIVA In non-infected animals Bi-annually – Spring & Autumn
Is the ab ELISA for IBR sensitive? specific?
Very sensitive? I think - check this, presentation not clear
- + animals must be classified as exposied
