what disease would you be suspicious of if you saw enlarged sciatic nerves and nodules in the liver during a PM?
mareks disease
what is another name for mareks disease
Gallid herpesvirus 2
what type of samples would you submit for PCR to confirm mareks disease?
1 mL blood (live animals); tissues, feather tip (postmortem)
Target: Gallid herpesvirus 2 nucleic acid (DNA virus)
what disease do you suspect with splayed legs in chickens?
mareks disease
mareks disease virus life cycle
-MDV invades lung air space and infects epithelial cells -> MDV infects cells and spreads to the feather follicle to replicate -> birds shed MDV particles in skin dander -> birds inhale MDV particles from dust in the environment
vaccination for mareks disease
-In OVO! We can vaccinate 18-day-old embryos!
-The chick has the best possible start when it hatches and better disease resistance from day one
-Manual subcutaneous vaccination is susceptible to human errors, while in ovo vaccination systems deliver the right dose in the right location
what are some reasons an animal may get a disease even though they are vaccinated against it? (4)
-Particularly virulent strain of virus
-Vaccine failure? (wrong administration route, not administered in correct quantity, poor preservation (e.g. vaccine got too hot/cold/old)
-Non-responder to the vaccine / immune status?
-Vaccine does not prevent infection, but prevents disease!
what viruses can cause erosive/ulcerative mouth lesions? (6)
-Bovine viral diarrhea virus (Flavivirus)
-Foot and mouth disease (Picornavirus)
-Infectious bovine rhinotracheitis (Alphaherpesvirus)
-Malignant catarrhal fever (Gammaherpesvirus)
-Rinderpest (Paramyxovirus)
-Vesicular stomatitis (Rhabdovirus)
what virus are you suspicious of if you see the following clinical signs?
-Progressing severe watery bloody diarrhea in young animals
-Oral mucosal ulceration
-Poor-doing calves (scruffiness, poor coordination, small)
-Distal limb erosions
*Clinical presentation could fit with mucosal disease OR severe, acute BVDV
what do you need to submit to determine BVDV?
To detect viral antigen:
-RT-PCR (both type 1 and type 2)
-Immunohistochemistry
-Virus isolation (~20 days)
Samples:
-Ileum with Peyer’s patch, spleen, mesenteric lymph node, esophagus
what do you need to consider when doing virus neutralization for BVDV?
- Results in 1 to 3 weeks
- Animals that have been vaccinated for BVDV will show a positive result
- Persistently infected animal: low or no antibodies
how do you differentiate between persistent infection and acute infection
A +ve PCR resut on a single sample cant distinguish between an acutely infected animal and a PI animal. re-test positive animal at least 3 weeks after first testing. PI animals will be virus positive a second time. acutely infected animals that have recovered will be negative
how can you test a herd for BVDV and tell positive/negative
-If the test is negative: you know every animal who contributed to the bulk tank is negative
-If the test is positive: milk should be retested in 3 weeks to rule out acute
infection
-If the bulk milk sample is positive a second time: you need to evaluate
animals individually
how do you control for BVDV
-Identification and elimination of persistently infected animals in a herd = also need to test any replacement animals
-vaccination = Ideally you would want to choose a vaccine that works against both BVDV 1 and 2
