lymphosarcoma

Question 1

which LN does BLV impact usually the most? bilateral or unilateral?

Answer 1

pre-scap
bilateral

Question 1

what are the 2 broad classifications of bovine lymphosarcoma? and tell me the broad differences

Answer 1

non-viral (sporadic):
- <3yr, rare, not associated with BLV

viral (adult):
- >3yr, slow progress, caused by BLV, “enzootic bovine leukosis”

Question 2

what are the 3 types of non-viral/sporadic bovine lymphosarcoma and tell me the broad differences

Answer 2

Calf form:
- <3-6 months
- lymphadenopathy, localized signs if tumor spread

thymic form:
- 6-24 months
- mass at thoracic inlet, may see bloat, reduced blood return, swelling

cutaneous form:
- 1-3 yrs
- raised ulcerated lesions, necrotic centers, progressive T-cell lymphoma, may occur then regress then re-occur

Question 3

BLV primarily infected what type of lymphocytes?

Answer 3

B lymphocytes

Question 4

tell me the typical signalment of a cow with BLV lymphoma

Answer 4

> 4 yrs old, dairy cow, gradual loss of condition, decrease in milk

Question 5

what are the C/S of BLV lymphoma?

Answer 5

gradual loss of condition, decrease in milk, peripheral lymphadenopathy, internal lymphadenopathy (abomasum, R atrium, exophthalmos)

Question 6

what are the 4 outcomes of BLV infection and how common are they?

Answer 6

1. none established (genetic resistance)
2. seropositive & no signs (60%)
3. seropositive & persistent lymphocytosis (30%)
4. seropositive & lymphosarcoma (<5%)

don’t have to remember percentages, just remember relative values

Question 7

when you have a cow that is seropositive for BLV with persistent lymphocytosis, does that indicate a pre-neoplastic stage?

Answer 7

nope!

Question 8

list some ways to diagnose BLV lymphosarcoma

Answer 8

• Hx, C/S –> older dairy cattle, bilaterally lymphadenopathy
• CBC –> persistent lymphocytosis but normal cytology
• PCR of lymphocytes, positive before Ab
• LN biopsy (histo)
• serology –> Ab+ presumed infected (ELISA)

Question 9

what are the limitations of using serology to diagnose BLV lymphosarcoma?

Answer 9

• Ab positivity may take 3-4 months
• colostrum Ab
• ELISA false negatives

Question 10

High proviral load (PVL) = ____ risk cow

Answer 10

high

Question 11

with BLV lymphosarcomas, most cows are _____ with _____ C/S

Answer 11

infectious, no

Question 12

what is the lag b/t infection and seropositivity?

Answer 12

3-4 months

Question 13

true or false: freeze thaw kills BLV virus

Answer 13

true

Question 14

cattle w/ lymphocytosis and/or clinical disease = higher/lower risk of transmitting BLV (high PVL)

Answer 14

higher

Question 15

true or false: the PVL established shortly after infection doesn’t stay - it keeps rising

Answer 15

false. it’s established shortly after infection and stays relatively stable over time

Question 16

true or false: low PVL cattle tend to stay that way, they don’t appear to be a big risk for transmitting BLV

Answer 16

true

Question 17

what are the BLV risk factors (horizontal transmission)?

Answer 17

• open herd w/ no iso protocol
• Holsteins > brown Swiss (maybe)
• heifer contact w/ older (BLV+) milking cows
• herds with more older cows (older cows shed more)
• blood transmission
• use of bulls in breeding

Question 18

can BLV be transmitted vertically?

Answer 18

yes! in utero and through colostrum/milk

Question 19

what are the two broad levels of control?

Answer 19

• positive herd to negative herd
• eradication –> voluntary, $$$, long term plan

Question 20

true or false: you should avoid raw bulk tank milk in BLV herds to feed calves

Answer 20

true!!