A parasite misses its mark.
by Margaret Leary
Patient information: Name: JXN. Species: Feline. Sex: MN. Breed: DSH. Birthday: 7/26/2011. Age: 1 year old. Color: Grey. Weight: 10 lbs. 12 oz.
Presenting concerns: fever.
History: Still febrile, ate once after home yesterday-new today, small scab on neck.
Physical exam findings: Scab is over breathing hole, not yet erupted, of small cuterebra. Removal after anesthesia/capstar, removed 7 mm grub, flush out poorly defined multichambered pocket over trachea. Red swollen area of tissue approx. 2.5 cm wide, hole after removal small, approx. 6 mm.
Assessment: Grub is a normal rabbit parasite. Does not mature to fly in a cat. Makes cat very sick before the grub dies. He will be 100% better as toxins leave his body. Hole will close up without any more treatment.
This report from the Ann Arbor Animal Hospital tells a lot about a type of cat parasite that was new to me, even after sixty years of cat ownership. But there's more. So here's the backstory.
"I'm way overinvolved emotionally with this cat, and I don't think he's going to make it to his first birthday next week," I told veterinarian Jessica Franklin at the AAAH on a hot day in late July. "He's been lethargic for two days, the antibiotics he got here yesterday didn't make any difference, he won't eat or drink, and he has this little scab on his neck that isn't near big enough to make him sick." I started to cry.
We got JXN shortly after Thanksgiving 2011-when Luke, our oldest cat, suddenly died. We chose a new feline-the smartest, handsomest, and most curious of all the kittens at the Ann Arbor Cat Clinic. We named him Jackson, and decided to spell it JXN for ease of texting (us, or him?). JXN is a beautiful cat, close to a Russian Blue: long legs, big ears, and huge eyes whose pupils are often enlarged by his close attention to every moving thing. We had JXN neutered, got all the right shots and tests,
and brought him home.
From day one, he was a delight, learning to climb on our fake holiday tree as he systematically removed each ornament, loving anyone who came to the house, and performing acrobatic, aerobatic leaps at his Cat Dancer toy. In spring he went outdoors and learned that real trees aren't so sturdy as steel ones. He fell about twenty feet but recuperated after an extended pee of relief. He had other scrapes, getting stuck on the roof and in other trees, and finding out about skunks, but by midsummer he was maturing and having fewer scary episodes. I remained concerned, however, about his habit of exploring every new thing, whether animal, vegetable, or mineral, by licking and nibbling.
And now this inexplicable, possibly incurable, fevered stupor.
"Your cat came in here yesterday with a fever of undetermined origin," Franklin told me. Then she broke into what seemed an inappropriate smile of joy. "But I know what's wrong. You found it. And I can fix it right now! Your cat chased a rabbit into its hole."
JXN had a "cuterebra grub" which is toxic to cats, Franklin said, but once it's removed an adult cat will quickly recover. JXN's fever and accompanying slightly elevated white blood cell count were his immune system's response to the grub's toxins.
Half an hour later, I was taking a woozy JXN home. He had a shaved spot on his neck, and the hole was a bit larger where Franklin had used tiny tweezers to gently remove the entire grub.
A bit of research on the Michigan Department of Natural Resources website helped me understand that JXN was the victim of Cuterebra horripilum. After a pair of botflies' summer mating, gravid females deposit eggs, usually along runways or at entrances to the host animal's burrow. C. horripilum tends to seek out the throat region in cottontail rabbits (or overly curious marauding cats). JXN probably picked his up chasing a rabbit into its lair.
The eggs hatch into larvae in response to a sudden increase in temperature-we certainly had that last July-and the moist environment of the host. The larvae enter the host by way of a natural body opening, commonly the nose or mouth (that licking habit), or a minute abrasion of the skin. They frequently remain in oral and nasal passages several days before worming and eating their way to preferred locations under the skin. Eventually the cuterebra pushes out of its breathing hole, falls to the ground, and pupates into another fly.
Cuterebra horripilum do not usually kill a healthy adult cat, although secondary infections might. The cuterebra can seriously compromise a kitten or young rabbit, though, because their weak immune systems allow the grub to grow quickly.
Staff at the Ann Arbor Animal Hospital told me that JXN was only their second cuterebra victim last summer, but in other years cuterebra cases have been numerous. All cat owners know about such parasites as fleas and worms, but who knew about cuterebras? Now I have my own specimen, safely stoppered up in a tube of alcohol.
Most important, JXN is completely back to his energetic, overly curious self. And I see that my deep attachment to him is driven by my preference to focus on his youth, not my own age, and on his need for me now that, in retirement, I have few other responsibilities.
There he goes, leaping off the deck to chase a squirrel up a tree. I hope he doesn't get to the nest.
[Originally published in July, 2013.]
On July 18, 2013, Fran wrote:
It's great to let people know about rare causes of sicknesses in pets like this, but everything could have easily been avoided if he was an indoor only cat. Especially since he explores with his mouth, there are lots of toxic plants and animals out there. After all, the average outdoor cat only lives 2-5 years, while the average indoor cat lives 17.
Keep your cats healthy and keep them inside!
On July 21, 2013, Margaret Leary wrote:
I appreciate your comment, and know about the statistics. This is a choice all cat owners have to make, and the decision may vary from cat to cat. Our cats have all lived over 10 years and like the outdoors so much we don't want them to be cut off from it. I trust you to make the best decision for your pets!
On October 12, 2013, wrote:
My daughter had one of these this month. Turns out children can also be incidental hosts.