Ticks, Fleas and Heartworm
- Ticks are small spider-like arachnids that attach to a host and suck blood. The host can be an animal (dog, cat, rodent) or a human. Adult ticks are about the size of a sesame seed but an engorged adult female can grow up to a half an inch.
- Ticks have a 4 stage life cycle that can take anywhere from 2 months to 2 years to complete depending on the species and environment. The four stages of growth are egg, larva, nymph and adult. An engorged adult female drops off the host and lays up to 3000 eggs in the environment. The eggs hatch into larvae which then develop into nymphs. Both the larva and the nymph attach to a host to suck blood, although these hosts are more typically rodents rather than dogs and cats. The adult tick is the typical form that attaches to dogs, cats and humans.
- Adult ticks crawl to the tips of grasses and shrubs and move onto the host when they brush up against the plant. Ticks cannot jump or fly. Although ticks can be found anywhere on the skin, they are more commonly found on the head, ears, neck and feet. Tick bites are generally painless and once they attach, they may feed for several days.
- Ticks are efficient at carrying and transmitting disease, since they feed slowly and often attach unnoticed. Of particular concern are Ixodes species of ticks, commonly known as blackleg or deer ticks. These ticks can transmit diseases such as Lyme disease and Ehrlichia. In dogs, symptoms of Lyme disease include fever, lethargy, swollen/painful joints and lameness. Lyme disease causes chronic long-term illness in dogs and humans when not treated quickly. It is thought to take at least 36hrs for an attached tick to transmit Lyme disease. Therefore, removing a tick quickly is very important.
- The Alberta Health Tick Surveillance study had over 1800 ticks submitted in 2015. Of these ticks, 133 were of the Ixodes species and 13% tested positive for the bacteria that causes Lyme disease. Blackleg (Ixodes) ticks are more common in southern BC, Manitoba, Ontario, Quebec and the Atlantic provinces. Warmer winters in Alberta are thought to be allowing for an increase in the tick population as more are surviving the winter. Ticks can become active when the ground temperature reaches 4C or higher.
- Fleas are a common external parasite of dogs and cats. They can be transmitted between these two species as well as acquired from rodents or other wildlife. Fleas are most prevalent in Alberta between April and October but can occur at any time of year in certain situations (ie. Outdoor cats, dogs boarding or at daycare). Fleas are small black insect-like parasites with red legs. They can jump high and move quickly.
- Fleas have a 4 stage life cycle. It is important to understand this life cycle in order to control fleas in the environment.
- Eggs – Flea eggs are very tiny. They are laid on the pet and then fall off into the environment. Eggs hatch in as little as 2-4 weeks especially in warm, humid conditions.
- Larvae- Flea eggs hatch into larvae. The larvae feed on organic debris and flea feces. They hide from light and burrow down into vegetation outdoors and carpet or furniture indoors.
- Pupae – Pupae form a protective cocoon over themselves. This is where the adult flea will develop. The adult can emerge from the cocoon in as little as 5-10 days or can survive in the cocoon for up to 9 months depending on the conditions in the environment. The cocoon is resistant to freezing, drying and insecticides. Adults are stimulated to emerge from the cocoon by heat, vibration, carbon dioxide or pressure.
- Adult – Once the adult emerges from the cocoon, it is attracted to light. This is how it finds a host animal. Once on the animal, the female flea will begin producing eggs within a couple of days. The adult can live on the host for 3 weeks and produce 40 eggs a day. The time from egg to adult stage can be as little as 2-4 weeks.
- Fleas can cause a number of problems in our pets: severe itching and skin disease, anemia in young/debilitated animals, the spread of diseases (ie. This is how the Plague was spread) and acting as carriers of tapeworms.
- Flea bites can also cause allergic reactions in some dogs. This is called Flea Bite Allergy. Only one bite is required to cause a reaction and the itching can be very intense. Often pets with flea bite allergy have never had a flea found on them. This is why flea control is so important in our pets that have skin allergies.
- Because most of the life cycle of fleas does not take place on our pets, it is often necessary to treat the environment as well as the pet when an infestation is confirmed. Environmental sprays should contain Insect Growth Regulators (IGRs) that will stop the development of eggs and larva. Vacuuming before treating the environment is important as this will stimulate adults to emerge from the cocoon. Discard the vacuum bag after use. Bedding should be washed in hot water.
- Heartworm (Dirofilaria immitus) is a blood borne parasite that lives in the heart and large vessels of dogs and occasionally cats. The female worm can be up to 14 inches long and infected dogs can have up to 300 worms in their heart. Adult heartworms can live for 5 years and can produce millions of offspring (microfilaria).
- Heartworm requires certain species of mosquitos as intermediate hosts. Microfilaria in the bloodstream are transmitted to the mosquito when it bites the host. They develop into larvae in this intermediate host. The infective larvae then re-enter a dog’s body through a mosquito bite. The infective larvae take about 6months to mature, move into the heart and vessels and produce microfilaria. Heartworm cannot be spread dog to dog without a mosquito intermediate host.
- Heartworm disease is found worldwide. Heartworm incidence in Canada is highest in southern Manitoba, southern Ontario, southern mainland British Columbia and southern Quebec. Heartworm is also found in most US states. Heartworms have to be carried by certain species of mosquitos. If these mosquito species start to move northward, this parasite may become more prevalent in other parts of Canada also.
- It takes several years for heartworm disease to cause clinical signs. Adult worms can clog the heart and major vessels, causing reduced blood flow to organs and congestive heart failure. Symptoms include cough, exercise intolerance, weakness and lethargy. This disease is often quite advanced when clinical signs become apparent and it can be fatal.
- The diagnosis of heartworm disease is typically by an ELISA blood test which tests for a protein produced by adult worms. This test can be negative early in the infection before the larvae have matured. Other possible tests include a blood smear to look for microfilaria, xrays to measure heart and vessel size as well as heart ultrasound which may actually visualize the worms.
- Treatment of heartworm disease carries some risk, although it is rarely fatal. The treatment can take months and dogs in treatment have to be carefully rested and monitored. Some dogs with heavy infestations can have lasting organ damage to the heart, liver and kidneys.
- Preventive medications are very safe and available in a variety of forms. These medications will kill microfilaria in the dogs bloodstream before they can mature and reach the heart. Heartworm preventive medications are typically given monthly during mosquito season. In Alberta, we typically recommend heartworm preventive medications when the pet travels to an area known to have heartworm disease. It is important that these pets are on monthly heartworm medications for the time they are travelling and receive their last dose when they are back in Alberta. These medications can be tablets, chews or spot on products.
There is a take-home message from all of this information. These parasitic infections can be prevented and controlled. Medications are available that are safe and effective in preventing all of these parasites. There is often some overlap in what the medications prevent and treat. Which medication is best for your pet depends on their lifestyle, the time of year, their age and any travelling they do. Some pets will require certain products only part of the year while others may benefit from year round treatment. It is important to give these medications on the schedule prescribed to make sure that there is not a break in your pet’s coverage. Beware of over-the-counter insecticide spot-ons for flea and tick control that can be purchased in pet stores. These products are very toxic to cats and can make cats very sick if they are in contact with a treated dog or if they are accidentally treated themselves. Please discuss your pet’s specific needs with one of our veterinary team and we can recommend a product that best fits your situation.