The Adventures of Django and Arya


For safe travels with your pet, you obviously have to look out for the most deadly flying bandit known to mankind – The Mosquito. These minuscule vectors can transmit diseases to humans and animals within the blink of an eye. Never underestimate the power of the mosquito, and always protect your cat or dog when travelling to pet friendly destinations that have a mosquito presence. Mosquitoes can transmit diseases to most mammals, including humans, cats, dogs and ferrets. In humans, Malaria poses the largest threat, while for other animals, Mosquitoes can transmit Heartworm. Heartworm symptoms in dogs can be particularly devastating, and in some cases, the disease can be fatal. So it’s super important to use a dog collar such as the Scalibor Protection Band, together with monthly Milbemax tablets. Although alternative anti-mosquito and Heartworm dog medicine, may be advised by your vet. For felines, Bravecto Plus for Cats offers two months protection from mosquitoes. Of course, your vet should always recommend the most appropriate treatments and medication for your individual pet. Like all other diseases, prevention is a priority with Heartworm to avoid devastating consequences for dogs. Also be aware that if a dog contracts Heartworm, the treatment can be expensive. Although possible, heartworm larvae is less likely to survive to adulthood in cats, as they’re usually atypical hosts. Keep reading to find out how to protect your cat or dog from mosquitoes, and subsequently Heartworm, whilst enjoying an international vacation.

Estimated reading time: 10 minutes

Which Countries have Mosquitoes with Heartworm?

Heartworm is a risk in many popular pet friendly destinations, but it’s more prevalent in southern Europe, as well as southern US States, Australia and Japan. in fact, At maturity, Heartworm is considered the most significant vector borne disease in dogs in America, having been reported in all 50 states. 

So, if your desired pet travel location basks in long, hot summers, then there’s always a possibility of mosquitoes carrying Heartworm.

If you’re travelling to the US on a pet vacation, the American Heartworm Society publishes Heartworm incidence maps every three years, showing US locations where the disease has been dominant. Testing data is gathered from thousands of veterinary practice, together with shelters. to produce this detailed map.

Which Mosquito Species Can Transmit Heartworm?

At present, more than 20 mosquito species that harbor the infective stage of heartworm larvae have been identified. However, this number continues to increase each year, with new species of mosquitoes known to transmit Heartworm (Dirofilaria immitis) being regularly discovered.

In addition, different species of mosquitoes have significant habitual and inherent differences that effect their efficacy in being Heartworm vectors. This include:

  • varying feeding and breeding habits
  • how far they can travel

As mosquitoes are known to adapt to adverse weather, global warming is said to have played a role in the growing number of mosquito species that can transmit Heartworm.

Mosquito Heartworm Transmission to Cats & Dogs

Not only are dogs more at risk of Heartworm than cats, but the consequences are also usually more severe. Heartworm is transmitted when a mosquito bites an infected host.

For example, a mosquito takes a chomp at a fox that’s carrying Heartworm larvae. Subsequently, the mosquito becomes a host for Heartworm microfilariae, which transform into Heartworm larvae within the mosquito’s body. Once infective with Heartworm larvae, the mosquito takes a blood meal from a cat or dog, which then becomes a host for the Heartworm larvae.

After the Heartworm parasite is transmitted to a host by a mosquito, the larvae starts to reproduce at an alarming rate. Heartworm rapidly spreads through the bloodstream, directly to the tissues of the infected host.

The larvae fully matures to adult Heartworm within about 6 months, and when mature, the worms take up residence in an animal’s heart and lungs.

heartworm treatment prevention cure medicine dogs cats pets mosquitoes
Mosquito Heartworm Life Cycle in Cats & Dogs

Each adult Heartworm can grow to an incredible 12 inches in length, and a large dog can hold more than 250 worms.

However, we’re not surprised that Heartworm larvae don’t usually fare well with a cat as their host! In fact, when attempting to infiltrate a cat’s bloodstream, Heartworm larvae usually won’t survive to adulthood. If they do make it, there’s likely to only be a few worms.

So, there’s a significant difference in the effects of Heartworm in these two pet species, therefore veterinarians in Heartworm prevalent countries usually emphasise preventing Heartworm in dogs.

Heartworm Symptoms in Dogs

The initial symptoms of Heartworm in dogs aren’t visible, so if a pet is infected it’s unlikely that they’ll display any outward signs until a few months later.

Then, as the worms begin to crowd the dog’s heart and lungs, one of the first symptoms to appear is usually a persistent cough.

Other Heartworm symptoms that you may notice in your dog are:

  • reluctance to exercise
  • fatigue after moderate activity
  • decreased appetite
  • weight loss

If your dog tests Heartworm positive, you must restrict their physical exercise. When dogs are active, and exerting physical energy, there’s a significant increase in the rate at which the Heartworms affect your dog’s heart and lungs.

So, it’s really important to limit their daily exercise – the more severe the Heartworm symptoms in your dog, they should have less physical activities.

Heartworm Symptoms in Cats

The most typical symptoms of Heartworm infestation in cats are a bit different to the Heartworm symptoms found in dogs.

For cats, Heartworm Symptoms tend to be:

  • Coughing
  • Raspy Breathing
  • Respiratory Issues (such as vomiting)

Consequences of Heartworm in Pets

Adult Heartworms continue to reproduce in a cat or dog’s bloodstream. Here, they continue to grow and expand, which is the most dangerous part of the life cycle. It may take years, but as the worms grow and expand, they begin to affect the heart and other vital organs as space within the cat or dog’s body reduces.

If Heartworm is left un-treated, the disease will cause life-long damage. In some cases, Heartworm can be fatal in cats and dogs.

Also, the cost of Heartworm treatment for dogs is long-lasting and expensive. The disease itself is extremely detrimental to a dog’s health, so as far as Heartworm is concerned, prevention is better than a cure.

How Long does Heartworm Last in Cats & Dogs?

Heartworm lifespan in dogs is between five to seven years. On the off chance the Heartworm survive until adulthood in a cat, they can last for two to four years.

Can Cats & Dogs Transmit Heartworm to Other Pets & Humans?

Heartworm isn’t a contagious disease, so a dog or other animal can’t pass it on directly.

However, if a Heartworm positive dog is bitten by a mosquito, that same mosquito could bite other pets. In this case, it will pass on Heartworm microfilariae to the other pet’s bloodstream, and they’ll become Heartworm positive. Therefore, always use a mosquito prevention treatment or collar for Heartworm positive dogs.

Humans can sometimes contract Heartworm, but it isn’t very common. Like cats, humans just aren’t great hosts for the Heartworm larvae!

Heartworm Treatment & Medicine for Dogs

The good news is that, in most cases, Heartworm in dogs is fully treatable.

Should a vet confirm a positive diagnosis, they will want to ensure that your dog’s health is stabilised before Heartworm treatment commences. If a dog has other serious health conditions, and is particularly weak, this process could take several months.

Efficacy of Heartworm treatment and medicine for dogs can depend on the severity of the symptoms. For instance, dogs with little or no signs of Heartworm, such as cough or lack of energy, have a high treatment success rate.

Thankfully, more severe dog Heartworm cases are also usually treated successfully, although there’s a higher risk of complications. Be aware that severity of symptoms doesn’t correlate with severity of Heartworm disease. A dog with few symptoms, could still have a high rate of Heartworm infection.

The American Heartworm Society provides a strategy for combating Heartworm in dogs, including treatment and medicine:

  • Your vet should start your dog on monthly Heartworm prevention medicine before the treatment commences. This is to ensure that your dog can’t contract any new Heartworm infection from mosquitoes, and is recommended for two months prior to Heartworm treatment.
  • The US Food & Drug Administration (FDA) has only approved one Heartworm medicine for infected dogs – melarsomine
  • To treat Heartworm, your dog will receive injections of melarsomine medicine by your veterinarian.
  • Wiithin 1-3 months of melarsomine use in dogs, the vast majority of adult Heartworms are eliminated. Although there are some risks associated with this medication’s use,
  • Resting in a confined area, and significantly restricted exercise during the Heartworm dog treatment period can decrease the chances of complications from the medicine.
  • Approximately 6 months after treatment is completed, your veterinarian will perform a Heartworm test to confirm your dog no longer has Heartworm.
  • To avoid the possibility of your dog contracting Heartworm disease again, it’s important to administer heartworm prevention dog medication or treatment, year round, for life.

Along with melarsomine, the Heartworm American Heartworm Society dog treatment criteria includes a few other medication. However, these Heartworm treatments are designed to improve the chance of melarsomine treatment success.

Heartworm Prevention for Dogs & Cats

Your vet should always be your first port of call, as they will recommend the best Heartworm prevention treatments for your pet. However, it’s common to use an anti-mosquito dog protection collar, together with monthly tablets, to protect your cat or dog from infected mosquitoes when you travel. These Heartworm prevention measures should be sufficient in protecting your dog from mosquitoes and Heartworm.

Effective cat and dog prevention treatments against mosquitoes, and subsequently Heartworm, include

Milbemax for Dogs

Milbemax tablets are available for both cats and dogs. For our dogs Django, Arya and Summer, we give them monthly Milbemax tablets to prevent Heartworm infection, as recommended by our vet here in Portugal. Whilst Milbemax offers protection against common internal worms when given on a quarterly basis, if it’s administered monthly it also protects dogs against the deadly Heartworm parasite transmitted by mosquitoes.

We also used to give our cat, Star, Milbemax tablets. However, after we were adopted by our new kitten Storm, we began using Bravecto Plus!

Bravecto Plus for Cats

Bravecto Plus is a comprehensive spot on treatment that protects cats from Heartworm parasites, as well as:

If there are gaps between treatments, cats can be re-infected with Heartworm and intestinal worms. But, with regular use every 2 months, Bravecto Plus reaches a steady state, providing continuous protection from Heartworm and intestinal worms between doses. 

Scalibor Dog Protection Band or Seresto Collar

In addition, we recommend investing in a Scalibor Dog Protection Band collar, which deters mosquitoes from biting your dog in the first place. The collar also offers 6 months anti-feeding protection against mozzies, while deterring fleas, ticks and sandflies for 5-6 months.

We have used the Scalibor Collar on our dogs for a few years now, in conjunction with monthly Milbemax tablets, and they’ve never had any noticeable bites.

The active ingredient in the Scalibor Dog Collar becomes effective after one week, so always put the collar on your dog at least a week before you are due to travel to a mosquito infested location. Don’t allow your dog to swim in the sea or fresh water areas for the first 5 days of wearing the collar, as it can be harmful to aquatic life.

The Seresto Dog Collar is another option, but it doesn’t stop a mosquito from biting your pet. However, it has been shown in scientific studies to be efficient in preventing Heartworm.

Scalibor Collars are only suitable for dogs, but the Seresto Protection Collar is also available in a version for cats.

These simple measures can save a lot of suffering for your pet further down the line. Once Heartworms are fully mature, the treatments available are very invasive, and expensive. So for your pet’s sake, keep them safe from mosquitoes when you travel to an international destination.

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