Parasite Control

Heartworm

Heartworm disease is a serious and potentially fatal disease that is caused by the parasitic worm Dirofilaria immitis, and it mainly affects dogs and less commonly, cats. The disease is endemic in Singapore and is spread by mosquitoes. When an infected mosquito bites a dog or cat, it injects the larvae into the pet, and the larvae then migrate via the blood to the lungs and eventually the heart, where they mature into adult worms (this process takes around 6 months). These adult worms, which can grow up to 12cm long, can result in severe damage to the heart, lungs, other organs, and in severe cases, death. 

What are the signs of heartworm disease?

In the early stages of the disease, many dogs (who are the natural host for the parasite) show few symptoms or no symptoms at all. If the infection persists resulting in increasing numbers of adult worms, symptoms will develop. 

Signs of heartworm disease may include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss. As heartworm disease progresses, pets may develop heart failure. Dogs with a large number of heartworms can develop a sudden blockage of blood flow within the heart, leading to a life-threatening form of cardiovascular collapse. 

Heartworm disease in cats is very different from heartworm disease in dogs. The cat is an atypical host for heartworms, and most worms in cats do not survive to the adult stage. Cats with adult heartworms typically have just one to three worms, and many cats affected by heartworms have no adult worms. This means that heartworm disease often goes undiagnosed in cats, however, even immature worms cause real damage in the form of a condition known as heartworm associated respiratory disease (HARD). Symptoms may include coughing, asthma-like attacks, periodic vomiting, lack of appetite, or weight loss. Unfortunately, the first sign in some cases is when the cat sudden collapses or dies.

How is heartworm disease prevented?

Heartworm disease causes lasting damage to the heart, lungs, and arteries, and can affect the pet’s health and quality of life long after the parasites are gone. For this reason, heartworm prevention is by far the best option. Treatment for heartworm disease, when needed, should be administered as early as possible in the course of the disease because the adverse effects of the treatment increases proportionally to the clinical signs.  

For puppies and kittens under 6 months old, a good cautionary measure to take would be to start them on heartworm preventives, in the form of chewable tablets or spot-on topical medication that is administered monthly. There is also a long-acting injection that can be given once a year. All these options are readily available at veterinary clinics.

If your pet is more than 6 months old and has never been on any preventatives, they will have to get tested for heartworms before starting on preventive medication. This is a simple blood test that will have results ready in just 15 minutes, and is absolutely necessary in case your pet already has heartworms, because some preventives, when ingested, can cause an anaphylactic reaction when it kills the juvenile heartworms present in the bloodstream.

Fleas, ticks, mites

How do our pets get fleas and ticks?

Fleas and ticks are external parasites that love to hide in your dog’s or cat’s fur and attach themselves to the skin for feeding. Pets that spend time outdoors, especially in grassy areas and thick foliage, are at risk. These parasites can also be found at home, in the garden, or in carpet fibres and underneath furniture. 

Why is flea and tick prevention important?

Fleas and ticks in Singapore can carry parasites and diseases that can cause severe, and sometimes even fatal diseases in your pet. 

Fleas commonly cause tapeworm (an intestinal worm) infections and skin disease (flea allergy dermatitis), and even anaemia in both dogs and cats. Fleas like human blood too, and they can jump from your pet’s fur or bedding onto your skin. Some people have a bad skin reaction to flea bites which can be intensely itchy. 

Ticks mainly affect dogs, and they can transmit serious and sometimes life-threatening tick-borne diseases such as tick fever (babesiosis, anaplasmosis, Lyme disease, ehrlichiosis). 

What are the tick and flea medications available?

Getting rid of and preventing fleas and ticks is easy and effective thanks to the availability of a variety of topical and oral medication. Depending on the level of infestation and the lifestyle of the pet, your veterinarian will help you select the product best suited for your pet. 

Tick and flea collars will repel fleas and ticks, and even prevent ticks from attaching, but they must be applied tightly enough to have skin contact. 

Topical spot-ons such as Frontline Plus® once applied, are stored in the sebaceous glands in your pet’s skin and spread over their body surface with their natural oils. Fleas and ticks are killed through contact with your pet’s skin and coat, before getting a chance to bite. These topical spot-ons usually last for a month and are not washed off the body even after grooming. 

Oral preventatives containing isoxazoline (e.g., Nexgard, Simparica, Credelio, Bravecto)  do not prevent tick attachment, but they have a relatively fast tick kill time. The tick kill time is important because the risk of disease transmission increases the longer the tick remains alive and attached to the host. Once these oral preventatives are administered, existing ticks are killed off in 24 hours, and fleas are killed off within 6-8 hours. These products continue to kill new tick and flea infestations for 1-3 months, depending on the product used. Other oral medications such as nitenpyram (Capstar) can start killing adult fleas within 30 minutes of ingestion, but the duration of action does not persist for very long. 

Fur mites in cats

Fur mites (Lynxacarus radovskyi) infest cats quite commonly in Singapore, especially those that roam outdoors and come into contact with grooming tools or stray cats that have contaminated the surrounding environment. These mites cause inflammation of the skin, and signs include a salt-and-pepper appearance of the hair coat, hair loss, and itching. The amount of itching seen varies between cats. 

Veterinarians diagnose the mites by taking a sample of the fur and searching for the mites and their eggs under a microscope. Treatment and prevention involve using a topical spot-on treatment such as Revolution® which lasts a month, or Bravecto® which lasts up to 12 weeks. 

Gastrointestinal worms

What are some of the common gastrointestinal worms?

Gastrointestinal worms that affect dogs and cats include roundworms, tapeworms, hookworms, and whipworms. 

Roundworms are the most common intestinal parasite. Your pet can pick up the infection by ingesting infected soil, licking contaminated fur or paws, or by drinking contaminated water. Infected female dogs may pass the infection to their puppies before birth, or afterwards while nursing. Infected female cats cannot infect their kittens before birth but can pass on the infection through nursing. Hookworms and whipworms can also be picked up by our pets by similar means. 

Pets become infected with tapeworms when they ingest fleas or lice that carry the parasite, or when they eat infected rodents, raw meat, and offal.

Many of these worms are zoonotic, meaning that they can be transmitted to humans. The most common animal to human infections come from accidentally eating the worm larvae or from larvae that penetrate through the skin. For example, children are at risk for infection if they play in areas that may contain infected faeces (such as dirt piles and sandboxes) where they pick up the larvae on their hands. It is important to practice good hygiene (e.g., prompt removal of faeces and washing hands) in potentially contaminated areas or around affected pets.

If our pets are infested, clinical signs include vomiting, diarrhoea, weight loss, anaemia (commonly caused by hookworms), and even death if left untreated. A simple faecal test can usually detect the presence of these worms. 

Treatment and prevention

Treatment and prevention options are readily available in the form of dewormers (tablets or topical treatment), which can be administered monthly or at longer intervals depending on a pet’s risk of infection. 

Puppies and kittens should be treated prophylactically as they could have been exposed whilst in utero or during nursing. Ideally, treatment should be given 2 weeks after birth and repeated at 2- to 3-week intervals to 2 months of age, then monthly to 6 months of age.