DVM Large Animal Medicine 5

Question 1

A cow is treated with a prostaglandin F2α analogue to induce luteolysis. On which day of the estrous cycle will this treatment be MOST effective?

Accepted Answer

Day 5-17 (mid to late diestrus)

Answer

PGF2α is effective only when a functional corpus luteum is present (days 5-17 of the bovine estrous cycle); administration before day 5 or after day 17 will not induce luteolysis.

Question 2

Which of the following is the MOST important biosecurity measure to prevent introduction of bovine leukemia virus (BLV) into a naïve herd?

Accepted Answer

Testing and culling of BLV-positive animals before introduction

Answer

BLV is transmitted via infected lymphocytes, so testing incoming cattle by ELISA or AGID and excluding seropositive animals is the most effective biosecurity measure.

Question 3

A horse is presented with acute laminitis following grain overload. Which underlying pathophysiologic mechanism is most directly responsible for lamellar disruption?

Accepted Answer

Activation of matrix metalloproteinases degrading lamellar basement membrane

Answer

In laminitis, MMP activation (particularly MMP-2 and MMP-9) degrades the lamellar basement membrane, disrupting the bond between the sensitive and insensitive lamellae.

Question 4

Potomac horse fever is caused by which organism and transmitted by which vector?

Accepted Answer

Neorickettsia risticii transmitted by ingestion of infected aquatic insects

Answer

Potomac horse fever is caused by Neorickettsia risticii, which infects aquatic flukes living in insects such as caddisflies; horses are infected by accidentally ingesting these insects near water.

Question 5

A feedlot steer develops peracute septicemia with hemorrhagic nasal discharge and dies within 24 hours. Post-mortem reveals hemorrhagic tracheitis and severe pulmonary edema. Which pathogen is most likely responsible?

Accepted Answer

Histophilus somni (thromboembolic meningoencephalitis)

Answer

Histophilus somni can cause a peracute septicemic form with hemorrhagic tracheitis, myocarditis, and rapid death, in addition to the classic thromboembolic meningoencephalitis.

DVM - Doctor of Veterinary Medicine Practice Test

DVM - Doctor of Veterinary Medicine Practice Test

DVM Large Animal Medicine 5