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External Parasites

Demodectic Mange:  This tiny worm-like parasite is Demodex canis. It lives in small numbers in the hair follicles of the skin on most dogs. Pups acquire this parasite from their mothers. When this parasite exists in small numbers on the dog, there is generally no issue with the animal's health. However, in young pups with weak immune systems the population of mites can proliferate. Demodex canis will usually appear between the age of three and six months. The pup will be presented with reddened areas with hair loss, around the eyes, the mouth and/or on the limbs. If the lesions remain localized the condition is mild and prognosis is good. Lesions generally resolve upon sexual maturity.  However, in a few cases, the lesions are more wide spread across the entire body. The hair loss covers a wider expanse of the body.  The reddened skin will become course and dry. This condition is very severe and if left untreated can be fatal. Treatment consists of long term treatment with a specific parasiticidal agent. A cure may be impossible to obtain but the animal can enjoy a near normal life by life long management of the condition with the current therapy.

Fleas: Fleas are normally a problem during warmer months, however, they can also persist during cooler seasons due to their ability to survive indoors. The symptoms of fleas on pets are repeated itching, scratching, and chewing. Owners may also see live fleas or flea dirt (feces) on their pets. Constant itching and scratching may lead to patches of hair loss and reddened, irritated skin. Although many pets are very itchy and uncomfortable, some may show no signs at all. In addition to making your pet uncomfortable, fleas can also transmit other parasites, such as tapeworms. Treatment of fleas consists of a monthly application (on-skin liquid or chewable tablet) of flea medication that is available from the clinic.

Ticks Are in the News Again! (Reprinted from "The Pawsitive Express" Spring 2018) There has been a lot of media promotion regarding tick prevention. With spring and summer seasons being warmer and longer, increased tick populations have been noted in Ontario in recent years. Climate change has made it possible for ticks transported by migratory birds to move further north. Some areas of Ontario have a higher tick population than others. You and your pet will encounter ticks in wooded areas, scrub brush, grassy meadows, and pastures.  

In late fall of 2017, two ticks submitted for testing from our hospital came back positive for Lyme disease. This is a great concern for humans and their pets. As a response, we have prepared a protocol for surveillance, the submission of ticks for testing, and treatment for cases with positive results. If a tick has been attached to your pet for greater than 24 hours, the tick will be sent to the Animal Health Laboratory, University of Guelph to be tested for Lyme disease. If the result of this test is positive for Lyme disease the pet will be treated for 21 days with doxycycline. If a tick has been attached for less than 24 hours the risk of disease transmission is low.  We will also be conducting a surveillance program throughout the spring to determine whether the pet has had previous exposure to Lyme disease. This surveillance protocol will determine the prevalence of Lyme disease in our area. As dogs come in for their heartworm test, the test we are using this year will screen for heartworm, lyme, ehrlichia, and anaplasmosis. If a result is positive, once again the pet will be treated for 21 days with doxycycline. If the test results are negative, we advise preventative measures to avoid tick encounters.


If you find a tick on yourself or your animal, remove it using a special tick removal tool or a pair of tweezers. Grab the tick by the head, as close to the skin as possible. Pull straight out, firmly and slowly until you have removed the tick. Do not crush it. Put the tick in a small container with a tight lid. Ticks found on dogs or cats can be submitted to our hospital for testing. Ticks found on humans should be submitted to your Public Health Office for testing. 

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Lyme Disease (Reprinted from "The Pawsitive Express" Spring 2017): Lyme disease is not actually a disease, but a syndrome with clinical signs associated with infection from the bacteria Borrelia burgdorferi. It is transmitted by ticks to host species such as dogs. Only one species of tick, Ixodes scapularis, (black legged tick), transmits the disease in Ontario. Even if your animal has a tick sitting on them, it does not mean that they are going to get sick from Lyme disease. In Ontario it is very uncommon for an animal to get sick with Lyme disease, even after a tick encounter.

There are many criteria that your veterinarian will use to evaluate if your animal truly has been infected with this bacteria and needs to be treated with specific antibiotics(1). The four main questions are:   

The signs of Lyme disease are non‑specific and are often transient or only present shortly after initial infection. There are a variety of preventive and therapeutic options for Lyme disease including tick control, vaccination and drug therapy.In North America there are only two species of tick that can transmit Borrelia burgdorferi, Ixodes scapularis and Ixodes pacificus.

There are many factors that influence the prevalence of Lyme disease in a particular area. These include: the tick’s ability to survive and propagate in an area; the presence of a Borrelia burgdorferi reservoir species in that same area; the likelihood of the tick finding a susceptible host and the likelihood of an encounter with a tick. The areas in Ontario that have established populations of ticks infected with B. burgdorferi are all located along the northern shores of Lake Ontario and Lake Erie. The spring and fall are the times of year when there is a higher chance of a host having a tick bite. It is very difficult to diagnose Lyme disease because only about 5‑10% of dogs exposed to Lyme disease develop clinical signs which are often non‑specific and variable.

There are many methods available both in veterinary clinics and laboratories to detect Borrelia burgdorferi spirochetes. Even when using these methods, the antibody is not detectable for the first three to four weeks after infection and will stay in the blood for years after the infection is cleared. One of the most common in‑clinic tests used is the IDEXX SNAP test. A blood sample is taken from your dog and the Snap test will diagnose the presence of antibodies to heartworm, Lyme disease and Ehrlichia canis. 

Canine Lyme vaccines provide protection by inducing antibodies that kill B. burgdoferi when the bacteria are transmitted from the infected ticks to the vaccinated host. Once a tick bites a vaccinated host, the antibodies prevent infection.

In Canada, protection from B. burgdorferi via ticks has been shown to be effective through the use of K9 Advantix. This topical spot‑on product should be applied at least seven days before suspected exposure to I. scapularis. The use of collars impregnated with amitraz have been shown to be more effective in interrupting the tick life cycle and be longer acting than topical applications of fipronil. 

Prevention includes limiting the opportunity for contact with ticks by keeping dogs on leash and limiting contact with uncultivated grasses and bushes where ticks may reside. For humans, wearing long sleeved shirts and pants will help to prevent skin attachment. The vaccines available for canine Lyme disease are not fully protective, but are recommended as part of the tick control program for dogs. Attached ticks should be removed as soon as possible and tick‑infested areas should be avoided whenever possible to reduce risk of infection.

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Ticks (Reprinted from "The Pawsitive Express" Spring 2016): There has been a lot of media promotion regarding tick prevention. Companies with tick prevention products have been pushing owners to protect their pets.  With spring and summer seasons being warmer and longer, increased tick populations have been noted in Ontario in recent years. Climate change has made it possible for ticks transported by migratory birds to move further north. 

However, not all of Ontario is endemic, as these companies would like you to believe. Certain areas of the province have higher tick populations than others. Ticks do raise health risks to pets and humans. The black legged tick which potentially carries Lyme disease is of great concern for people. (See the articles ‘Ticks” and ‘Lyme Disease” for information on tick borne diseases following this article.) In the past, Dr. Wright saw on average about three tick cases in the clinic per year. Last spring/summer there were perhaps six. Prevalence in the Centre Wellington area has been quite low.  Yet other areas like the Niagara Region or Prince Edward County have shown a greater prevalence of ticks.There will be a different risk to you and your pet depending upon your life style and where you travel. How do you determine whether you should treat or not treat for ticks? The answer is three fold - education, monitoring, and prevention:


Heartworm is a parasite spread from any infected canine (coyote, fox, wolf, dog) to your pet by a mosquito. The adult heartworm lives in the heart and large vessels of the heart. They prevent free flow of blood through the heart chambers which eventually leads to heart failure. Unfortunately, by the time you pet exhibits symptoms, the disease will have already caused severe damage to the heart. A dog with heartworm disease will fatigue easily and will not tolerate exercise. They will present with a cough and a poor general appearance.

There are a number of different heartworm treatments and heartworm/flea treatments available. The medications are based on body weight, so young dogs under seven months of age will have to be weighed before medication can be dispensed. Dogs older than seven months that have not been on heartworm medication before must have a blood test before the medication can be dispensed. This ten-minute blood test can be run at the clinic.

All heartworm medications are considered a treatment. They do not prevent heartworm disease but will treat any infection acquired over the last 30 days. These products are designed and packaged to treat your animal for the entire heartworm season which is mid-May through to late October. It is imperative that you treat your pet(s) each month until late in the fall, to make sure your pet does not harbour an infection. These products vary in method of application and cost. As well as heartworm, most products also treat intestinal worms.

Internal Parasites

When you receive the notice that your pet is due for its annual examination we request that you bring in a fresh faecal sample from your pet. The examination of the faeces is a convenient and easy method to determine whether your pet is harbouring internal parasites. Internal parasites are not only a concern for your pet's health but some are also a concern for you and your family.

The internal parasites that we most commonly look for are the roundworm, hookworm, whipworm, and tapeworm. The life cycle of these parasites can be quite complicated within their host. We won't go into details of the life cycles here, however, what is important is that eventually the mature adult worms settle in the intestines and produce eggs. These eggs are shed with the faeces and infect the environment. Your pet can acquire a parasitic infection by the ingestion (eating) of faeces or infected prey, and by ingesting grass or dirt that is contaminated with eggs. Your pet can acquire hookworm or whipworm infections by frequenting contaminated areas, as the parasites enter the body through skin contact. Puppies and kittens acquire parasitic infections through ingestion of the mother's milk.

Senior pets, puppies, and kittens are the most vulnerable for parasitic disease. A worm infection may interfere with normal food absorption and be the cause of lack of weight gain in mild cases. However, in severe infestations it can cause diarrhea, vomiting, intestinal obstruction, and life-threatening anaemia. A healthy adult animal infected by a few worms may not show any signs of disease, however it is a reservoir of infection that sheds eggs into the environment. All ages of pets can harbour parasites so treatment, preventative measures, and/or monitoring should be done on a regular basis.

Humans can acquire a parasitic infection from their pets. Children and people with compromised immune systems are the most at risk.


Roundworms: Humans are not the natural host for dog and cat parasites. The accidental ingestion of roundworm eggs results in a condition called Toxocarisasis (visceral larvae migrans). The eggs hatch and the larvae migrate through the visceral and muscle tissue looking for their natural host. This infection can cause fever, coughing, pain, and liver and spleen enlargement.

Hookworms:  Hookworm infections cause a dermatitis called cutaneous larvae migrans or "creeping eruption". The larvae migrate through tissues searching for its natural host. For humans, the chance of contracting an infection in temperate climates is small. However, infection is common in tropical areas where soils are moist and sanitation is poor. Infection is acquired by walking barefoot in contaminated areas as the larvae penetrate the skin. Hookworm infection can also cause fever, coughing, and abdominal pain as well as presenting a very itchy rash on the skin.

Tapeworms:  Tapeworm infestation cannot be detected by looking for eggs in the faeces. Tapeworm eggs are shed in small packets called proglottids and look like grains of rice. They can be shed with or without faeces and are found around your pet's anal area. Diagnosis of tapeworm is done by observation (often by the owner) or through consultation with your veterinarian. Tapeworms have an intermediate host, meaning that the larvae must pass through a different species before it manifests itself and matures in its specific host, in this case the dog or cat. The intermediate host for the dog and cat tapeworms can be a number of other species including the flea, rabbits, mice, and other rodents. Therefore, if your pet is frequently outdoors and ingests mice or rabbit droppings or your pet has contracted fleas, it is assumed that a tapeworm infection follows and the pet will be treated appropriately. 

Giardia is a common protozoan (single celled) parasite that affects many species but is most common among dogs, cats, humans, and beavers. When the cysts of the giardia are ingested, the cyst walls are digested and the organisms situate themselves in the small intestine. As the organisms increase in number and start to produce cysts, they cause an infection that results in severe diarrhea.

Diagnosis is determined by a wet mount faecal smear. This smear must be created using a fresh, warm faecal sample. When viewed under a microscope, these motile organisms can be seen swimming about on the slide. Treatment is a course of appropriate antibiotics. 

The following will assist in preventing parasite infection in your pet(s) and your family:

Vector Borne Diseases

Vector borne diseases are those whose pathogens are transmitted from one animal including humans to another by arthropods, (invertebrate insects). Included within this group are mosquitos, fleas and ticks. Arthropods transmit diseases from almost every class of pathogen e.g. viruses, bacteria, rickettsia (micro-organism similar to bacteria), protozoa and helminthes (worm or worm-like parasite). These pathogens gain entry into the blood stream through feeding of an infected insect on blood.

Lyme disease and Heartworm disease are the best known vector borne diseases familiar to pet owners. In a recent letter sent to our canine clients, we mentioned four other diseases spread by arthropods (mainly ticks). These included Babesia spp., Bartonella spp, Ehrlichia spp, and Anaplasma spp.

Babesia spp. is a protozoan parasite that enters and attacks blood cells. In dogs it causes biliary fever or malignant jaundice. Some signs that a dog may present with are pale mucous membranes, fever, icterus (jaundice), and splenomegaly (enlarged spleen). Babesia spp. is treated with a readily available antibiotic, Clindamycin. Prognosis for dogs suffering from Babesia is guarded. It is not unusual for the dog to experience a relapse.

Bartonella spp. is a bacterium. Ticks are strongly suspected as being the vector for spreading this disease. Dogs seen with Bartonella spp. present with fever, anemia, lethargy, pale mucous membranes, which can lead to myocarditis (inflammation of the heart muscle, endocarditis (inflammation of the heart lining). Doxycyline is considered the treatment of choice for Bartonella spp. infections.

Anaplasma spp. and Ehrlichia spp. are both rickettsiae parasites of blood. Both create anemia in the infected host. Often dogs infected with either Anaplasmosis or Ehrlichia may appear asymptomatic, showing no signs of disease. In mild cases of Anaplasmosis and Ehrlichiosis the signs would be anemia, lethargy, pale mucous membranes and fever. In severe cases of Anaplasmosis, a dog could develop cyclic thrombocytopenia; a condition where the blood platelets are reduced affecting the clotting process of the blood. This can lead to a life threatening condition where the bone marrow is unable to produce new red blood cells. The good news is that treatment with Doxycycline and supportive therapy has been very successful in treating Anaplasmosis and Erhliciosis in dogs.

A study published in the Canadian Vet Journal in May 2011(1) found that the risk for vector borne infectious agents in the Canadian canine population in general was low. Vector borne diseases were found in all provinces. Although wide spread, there were areas where the number of affected ticks were more concentrated. With warmer weather from climate change we have already seen an increase of ticks in Ontario. This would suggest that the 2011 publication greatly underestimates the infection rate 10 years later. We can expect to see an increase of these vector borne diseases in Ontario in the future.

In summary:

Prevention is the best protection: