Case Review: Rodenticide toxicity in five cats in same household

by Jennifer Jellison, DVM

History

Two 5-month-old kitten siblings, Nora and Mina, were presented for ovariohysterectomy (OHE). Both cats were indoor only, current on all vaccinations including rabies, feline viral rhinotracheitis (FVRCP) and feline infectious peritonitis (FIP). Feline leukemia virus (FELV)/feline immunodeficiency virus (FIV) test was negative. Client also owned the mother of the two kittens and the queen was current on all vaccinations, dewormed and FELV/FIV negative. The kittens had been on basic preventive care since 6 weeks of age with no health problems aside from roundworm infection at 6 weeks, which was treated with pyrantel and resolved.

Presentation

Mina and Nora both had normal physical exams. Pre-anesthetic bloodwork was normal (see results below). Both cats received butorphanol/Telazol® premedication followed by induction with propofol and maintained on sevoflurane during the surgical procedure. EKG and pulse oximeter readings were normal throughout the procedure with average HR 144 bpm and oxygen saturation 98%. OHE was routine—double ligation of ovarian pedicle with 3-0 Monocryl and transfixion of cervix with 3-0 Monocryl. Nora's procedure was normal.

Mina had a slight amount of bleeding from her cervix after the transfixing suture so an additional suture was placed. There was no abdominal bleeding on either kitten at time of closure, which consisted of 3-0 Monocryl simple interrupted sutures in the body wall and 3-0 Monocryl simple interrupted sutures in the skin. Recovery was uneventful. Both kittens had pink mucous membranes (mm) post-op on hourly checks, and post-op temps were 98.7/97.2, and within one hour had risen to normal (>100.1). The kittens had routine temperature-pulse-respiration (TPR s) hourly for approximately six hours post operatively.

At the time of surgical release when Nora was picked up to be placed in her carrier, frank blood oozed out of her incision. Further examination showed mm pink, capillary refill time (CRT) < 2 sec and no bruising around the incision. Radiographs showed a small area of fluid around the caudal abdominal incision and the decision to examine the abdomen for surgical bleeding was made. PCV/TP was rapidly evaluated and found to still be within normal limits but were lower than the pre-surgical values. Upon examination of the abdomen, all ligatures were intact but a small bleeder alongside of the cervix was observed. The cat did have some small amount of frank blood in the abdomen but did not appear to have any additional active bleeding present.

On closure, the musculature of the body wall seemed to be the source of the fresh bleeding. There was mild oozing but no frank bleeding was seen. The owners agreed to monitor the cat closely through the night. Mina, the second kitten, was then placed in her carrier and sent home. The owners returned in one hour with frank blood coming from her incision as well. Physical exam revealed temp 100.4, heart rate (HR) 134, respiratory rate (RR) 15, mm pink, CRT < 2 sec. Her incision was also dripping frank blood. PCV 34/Total Protein 5.4. A thorough questioning of the owner revealed no known toxins in the household. Differential diagnosis at this point was surgical complication in both kittens or an inherited bleeding disorder, which appeared unlikely based on lack of dramatic clinical bleeding.

Diagnostic tests

Nora

FELV/FIV - neg
Internal organ function – within normal limits (WNL) except ALT 123 U/L(12-115)
CBC - WNL
Fecal - negative

Mina

FELV/FIV- negative
Internal organ function - WNL
CBC - WNL except MCV 38.00 fl(normal 39-50)

Discussion points to consider

  • What heritable bleeding conditions exist in the cat?
  • What differentials would you consider?
  • If you were the surgeon on this case and believed this could be the result of surgical a complication, how would you professionally explain to the owner what was happening?
  • What would be the next step in this case?

Treatment

This case did not seem to have a clear-cut diagnostic solution. The practitioner on the case again began to take a very thorough history from both owners together. History revealed the owner's home did have rat poison in one corner of the basement, which both owners were convinced the cats could not access. Based on this information, both kittens immediately received Vit K1 injections with a small gauge needle.

Blood was drawn for coagulation testing:

Nora: Prothrombin time (PT)-14.3 seconds- Reference range 6.0-11.0 seconds
Activated partial thromboplastin time (aPTT)-59.8 seconds- Reference range 10-25 seconds

Mina: PT-12.7 sec
aPTT-54.6 sec

Both cats received whole blood transfusions and were transferred to an overnight emergency facility. Recovery through the night was uneventful. The cats were placed on Vit K1 orally, 25 mg daily for 30 days. PT testing of the other four cats in the household revealed elevated PT values as well and they were placed on Vit K1 for one month as well. It was discovered that the exterminator had placed bromodiolone as a rodenticide in the basement of the owners' home without their knowledge.

Outcome

The cats were retested in 30 days and PT, aPTT values remained elevated. The cats remained on Vit K1 for 75 days before clotting values returned to normal. Recovery was successful and all five cats are doing well six months post exposure.

Overview

Bromodiolone is an anticoagulant used commercially by exterminators. It is a potential hazard for all mammals and birds1. Interference with normal blood clotting as a result of reduced concentrations of clotting factors both intrinsic and extrinsic occurs due to competitive inhibition of the vitamin K reductase enzyme.1 Signs can occur within one day of ingestion but most commonly are seen after a lag period of three to five days. As a result, history becomes a vital part of diagnosis. Ask the owner and then ask again.

An elevated PT shows up first due to factor VII-having the shortest half life of the vitamin-K dependent factors followed by an elevation of aPTT. Strangely in this case, the post-surgical complications may have saved the lives of all the household cats as the owners were unaware that an anti-coagulant rodenticide had been placed in their home.

References

  1. Beasley V. Toxicants that interfere with the Function of Vitamin K. In: Veterinary Toxicology. International Veterinary Information Service. 199