Heartworm – the silent killer

Yulia Khouri / Khmer Times No Comments Share:
MC aka Nori hunting bugs at his home. He passed away on April 22 of heartworm disease. Rest in Peace, little guy. Supplied

Yesterday we had to say goodbye to one of our most memorable rescues, a cat called MC, who was adopted by two roommates – Jamie and Taylor – about a year ago. I rescued him as a tiny kitten under a rather unforgettable circumstance: barely six weeks of age, he was trying to cross Norodom Boulevard near the Independence Monument at noon. To those living in Phnom Penh, you know how huge, very busy and erratic the traffic is in that area.

The kitten was running, then stopping and running again, appearing and disappearing under the speeding cars. I noticed him and at first, I thought it was a rat. Still, feeling bad for the terrified animal, I slowed down my car. But as soon as I realised it was a panicking kitten, I didn’t think twice (one could safely say I did not think much at all and acted on instincts only), stopped my car and ran out, chasing the terrified kitten between the cars: the traffic – at first hasty – went dead quite quickly. All cars stopped. I am sure I presented a fairly interesting and unexpected entertainment to the drivers, with both laughter and some disbelief as everyone observed me – a foreigner running madly between the cars.

To my relief, when I dived under one car trying to lure the kitten from underneath, I realised that many people, car and tuk-tuk drivers and passengers, were getting out of their vehicles and were enthusiastically helping me catch him. When I had him finally in my arms – terrified, dirty, skinny, full of fleas, but also full of life in his eyes – everyone clapped. I called the kitten Nori; and after 2 months of rehabilitation, vaccinations and treatment with us, he was adopted to a great, caring and loving home and was renamed MC.

He grew strong, big and beautiful. He ate well and, according to his owners, loved to chase bugs all day long.

All was well, until about eight weeks ago. MC was brought in to our clinic with lethargy, loss of appetite and weight, fever and vomiting.

We dived in immediately, testing him thoroughly. Blood tests, rapid antigen tests, antibody tests. Specific lab tests ruled out most common problems like FIV, FIP and FELV. After another set of blood tests – both lab and microscope smears – and X-rays, we sent the samples off to our consulting vets around the world: Australia, California and Columbia University in New York.

All vets called him a mystery cat – a bitter coincidence in some way that his name was MC. We followed several treatments and at some point, he was getting better. But just few weeks after, he was back with same symptoms and he was getting more ill.

At last, we found the cause: MC tested positive for heartworm. We were devastated.

So, what is heartworm? Heartworms are spread through mosquito bites carrying infective heartworm larvae. The larvae migrate through the body until they reach the heart and blood vessels of the lungs. There, the larvae mature and reproduce, releasing immature heartworms into the animal’s blood. It is thought to be much less common in cats than in dogs, but this view is now changing with new research.

One of the most challenging aspects of diagnosing feline heartworm disease is that there are no specific clinical signs.

According to the American Heartworm Society, the signs vary from subtle to very dramatic: it could be a sudden onset of coughing and rapid breathing, but these signs can also be caused by several other diseases. Other common symptoms “include weight loss, vomiting, lack of appetite, difficulty walking, experience fainting, seizures, or suffer from fluid accumulation in the abdomen”. Veterinary researchers agree that the disease in cats has more prevalence than previously thought. Several university studies have shown that up to “15 percent of all cats in certain locations, regardless whether they are outdoor or indoor have been exposed to feline heartworm disease”.

According to several veterinarians I personally spoke to, the treatment of heartworm is just as complex and unpredictable as its diagnosis. Some suggest to treat the heartworm in cats with medications designed for dogs, but this could lead to fatal side effects such as lung failure and death. Treating the symptoms and hoping that the patient outlives the worms is another course of action. The complications in this case seem to be rather vast, from acute crisis and sudden death.

In some parts of the world – Japan and Europe – surgical extraction techniques of heartworms are being perfected. There is an optimism among the veterinary community that with improvement of the technique, it may become the best option for treating the disease.

At this time however, there is no good treatment for heartworm-infected cats. Effective drugs are not available, especially in Cambodia. Even those infected cats that seem to be doing better may die suddenly or succumb to terrible side effects.

According to Dr Ernest Ward “treating heartworm infections in cats is risky at best, and not treating these cats is just as risky. It will take about two years for the parasitic infection to be eliminated in the cat, and serious clinical signs can suddenly appear at any time during this period.”

I cannot stress enough that prevention is the best way to protect your furry family member. There are plenty of safe drugs available and they have low toxicity levels. At our clinic we use products called Advocate or Revolution – both have shown a wide margin of safety even for kittens as young as eight weeks. These are not injections, but topical drops that will protect your animal from heartworm and other parasite infestation as well. Your veterinarian can help you choose the safest option for your animal.

As I said goodbye to MC (whom we all called Mystery Cat in the end, given the intensive search for answers for his mystery illness globally) and hugged his grieving family, I once again reminded myself that even an indoor cat – the loved and cared one – needs just that one mosquito bite to succumb to the deadly disease. And in hot and humid Cambodia, where mosquitoes are lurking everywhere, the risk is just too high.

Stay protected.

In Loving Memory of MC aka Nori.


Animal Mama® Animal Clinic & Welfare Centre provides a wide range of services for animals & pets: vet care, boarding, daycare, pet food & supplies, hydrotherapy, grooming and doggy play dates.
Please visit us at:
Villa #15, Street 500
Toul Tom Pong, Phnom Penh 12311
Clinic: +855888744411
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