Heartworm Disease in Dogs

What causes heartworm disease?

Heartworm disease or dirofilariasis is a serious and potentially fatal disease. It is caused by a blood-borne parasite known as Dirofilaria immitis.

Adult heartworms are found in the heart and adjacent large blood vessels of infected dogs. Rarely, worms may be found in other parts of the circulatory system. The female worm is 6 – 14″ long (15 – 36cm) and 1/8″ wide (5mm). The male is about half the size of the female. One dog may have as many as 300 worms present when diagnosed.

“Adult heartworms may live up to five years…”

Adult heartworms may live up to five years and, during this time, the female produces millions of offspring called microfilaria. These microfilariae live mainly in the small vessels of the bloodstream.

What is the life cycle of the heartworm?

“…the parasite requires the mosquito as an intermediate host…”

The life cycle of the heartworm is complicated; the parasite requires the mosquito as an intermediate host before it can complete its life cycle in the dog. As many as 30 species of mosquitoes can transmit heartworms.

The life cycle begins when a female mosquito bites an infected dog and ingests the microfilariae during a blood meal. The microfilariae develop further for 10 – 30 days in the mosquito’s gut and then enter its mouthparts. At this stage, they are infective larvae and can complete their maturation when they enter a dog. The infective larvae enter the dog’s body when the mosquito bites the dog. They migrate into the bloodstream and move to the heart and adjacent blood vessels, maturing to adults, mating and reproducing microfilariae within 6 – 7 months.

Where is heartworm disease found?

“Canine heartworm disease occurs all over the world.”

Canine heartworm disease occurs all over the world. In the United States, it was once limited to the south and southeast regions. The highest numbers of reported cases are still within 150 miles of the Gulf of Mexico and the Atlantic Ocean coastlines and along the Mississippi River and its tributaries. However, the disease is spreading and is now found in most regions of the United States, including California, Oregon and Washington. In Canada, the disease is problematic in areas where mosquitoes are prevalent, such as along waterways and coastlines in many provinces. The greatest number of cases in Canada occurs around the southern Great Lakes.

How is heartworm disease spread?

“…the disease is not spread directly from dog to dog.”

Since transmission requires the mosquito as an intermediate host, the disease is not spread directly from dog to dog. Spread of the disease therefore coincides with mosquito season, which can last year-round in many parts of the United States. The number of dogs infected and the length of the mosquito season are directly correlated with the incidence of heartworm disease in any given area.

The mosquito usually bites the dog where the hair coat is thinnest. However, having long hair certainly does not prevent a dog from getting heartworms.

What do heartworms do to the dog?

It usually takes several years before dogs show clinical signs of infection. Consequently, the disease is diagnosed mainly in two to eight year old dogs. The disease is rare in dogs less than one year of age because the microfilariae take five to seven months to mature into adult heartworms after infection. Unfortunately, by the time clinical signs are seen, the disease is usually well advanced.

Adult heartworms: Adult heartworms cause disease by clogging the heart and major blood vessels leading from the heart. They also interfere with the valve action in the heart. By clogging the main blood vessel, the blood supply to other organs of the body is reduced, particularly blood flow to the lungs, liver and kidneys,causing these organs to malfunction.

The signs of heartworm disease depend on the number of adult worms present, the location of the worms, the length of time the worms have been in the dog and the degree of damage that has been sustained by the heart, lungs, liver and kidneys.

“Signs of heartworm disease are a soft, dry cough, shortness of breath… and loss of stamina.”

The most obvious clinical signs of heartworm disease are a soft, dry cough, shortness of breath, weakness, nervousness, listlessness and loss of stamina. All of these signs are most noticeable following exercise, when some dogs may even faint or become disoriented. Your veterinarian may notice abnormal lung and heart sounds when listening to the chest with a stethoscope. In advanced cases, congestive heart failure may be apparent and the abdomen and legs will swell from fluid accumulation. There may also be evidence of weight loss, poor condition and anemia. Severely infected dogs may die suddenly during exercise or excitement.

Microfilariae (immature heartworms): Microfilariae circulate throughout the body but remain primarily in the small blood vessels. Because they are about as wide as the small vessels, they may block blood flow in these vessels. The cells being supplied by these vessels are then deprived of the nutrients and oxygen normally supplied by the blood. Microfilariae primarily injure the lungs and liver. Destruction of lung tissue leads to coughing. Liver injury leads to cirrhosis of the liver, causing jaundice, anemia and generalized weakness. The kidneys may also be affected and allow toxins to accumulate in the body.

How is heartworm disease diagnosed?

In most cases, one or more simple blood tests will diagnose heartworm disease. Further diagnostic tests are essential to determine if the dog can safely undergo heartworm disease treatment. Some or all of the following diagnostic procedures are recommended before treatment is started:

Serological test for antigens to adult heartworms (antigen test, ELISA or SNAP test): This test is performed on a blood sample.

“The most widely used test detects antigens (proteins) produced by adult heartworms.”

It is the most widely used test because it detects antigens (proteins) produced by adult heartworms. It can be positive even if the dog does not have any microfilariae in the bloodstream (approximately 20% of cases). Dogs with less than four or five adult heartworms may not have produced enough circulating antigen to produce a positive test result, so there may be an occasional false negative result in dogs with a low burden of parasites, or in the early stages of infection. Because the detected antigen is only produced by the female heartworm, a population of only male heartworms will also give a false negative. Therefore, there must be at least four to five female worms for a positive result by this test.

Blood test for microfilariae (microscopic or Knott’s test):

“Blood sample examined under the microscope for the presence of microfilariae.”

A blood sample is centrifuged and then examined under the microscope for the presence of microfilariae. If microfilariae are seen, the test is positive. The number of microfilariae seen gives a general indication of the severity of the infection. However, the microfilariae will be found in the bloodstream in greater numbers in the summer months and in the evening, so sampling time can affect this test. Approximately 20% of dogs do not test positive, even though they have heartworms, because their immune system has acquired the ability to destroy the microfilariae. Also, there is another blood parasite that is fairly common in dogs that can be hard to distinguish from heartworm microfilariae. For these reasons, the antigen test is preferred for diagnosis.

Other blood tests (CBC, blood chemistries, electrolytes): Abnormalities on the complete blood count (CBC) and blood tests for kidney and liver function may suggest the presence of heartworm disease. These tests will be performed on dogs diagnosed as heartworm-infected to determine the function of a dog’s organs and health status prior to treatment.

Radiographs (X-rays): A radiograph of a dog with heartworms will usually show heart enlargement and swelling of the large artery (pulmonary artery) leading to the lungs from the heart. These signs are considered presumptive evidence of heartworm disease. Radiographs may also reveal the condition of the heart, lungs and pulmonary vessels. This information allows us to predict an increased possibility of complications related to treatment.

Electrocardiogram (EKG or ECG): An electrocardiogram is a tracing of the electric currents generated by the heart. It is most useful to determine the presence of abnormal heart rhythms. This test can also detect enlargements in heart chamber size and help determine if a dog can safely undergo heartworm disease treatment.

Echocardiography (ultrasound of the heart): An ultrasonic examination shows the heart chambers allowing the general status of the heart to be evaluated. The heartworms also be visualized.

How is heartworm disease treated?

There is some risk involved in treating dogs with heartworms, although fatalities are rare.

In the past, the drug used to treat heartworms contained high levels of arsenic…”

In the past, the drug used to treat heartworms contained high levels of arsenic and toxic side effects frequently occurred. A new drug is available that does not have as many side effects, allowing successful treatment of more than 95% of dogs with heartworms.

When some dogs are diagnosed, they have advanced heartworm disease. This means that the heartworms have been present long enough to cause substantial damage to the heart, lungs, blood vessels, kidneys and liver. A few of these cases will be so advanced that it will be safer to treat the organ damage rather than risk treatment to kill the heartworms. Dogs in this condition are not likely to live more than a few weeks or months. Your veterinarian will advise you on the best treatment approach for dogs diagnosed with advanced heartworm disease.

Treatment to kill adult heartworms:

“Injectable drug to kill adult heartworms is given.”

An injectable drug to kill adult heartworms is given. It kills the adult heartworms in the heart and adjacent vessels. These injections may be divided and given thirty days apart. Your veterinarian will determine the specific injection schedule according to your dog’s condition. Many dogs will also be treated with an antibiotic to combat potential infection with bacteria (Wolbachia) that inhabit the heartworm.

“Complete rest is essential after treatment.”

Complete rest is essential after treatment. The adult worms die in a few days and start to decompose. As they break up, they are carried to the lungs, where they lodge in the small blood vessels and are eventually reabsorbed by the body. This resorption can take several weeks to months and most post-treatment complications are caused by these fragments of dead heartworms. This can be a dangerous period so it is absolutely essential that the dog be kept as quiet as possible and is not allowed to exercise for one month following treatment. The first week after the injections is critical because this is when the worms are dying. A cough is noticeable for seven to eight weeks after treatment in many heavily infected dogs. If the cough is severe, notify your veterinarian for treatment options.

Prompt treatment is essential if the dog has a significant reaction in the weeks following the initial treatment, although such reactions are rare. If a dog shows loss of appetite, shortness of breath, severe coughing, coughing up blood, fever or depression, you should notify your veterinarian. Treatment with anti-inflammatories, antibiotics, cage rest, supportive care and intravenous fluids is usually effective in these cases.

Treatment to kill microfilaria: Approximately one month following treatment to kill the adults, the dog must return to the hospital for administration of a drug to kill the baby heartworms or microfilariae. Your dog may need to stay in the hospital for the day. Following treatment, your dog will be started on a heartworm preventative.

“Newer heartworm treatment protocols use a variety of drugs to kill the microfilariae.”

Newer heartworm treatment protocols use a variety of drugs to kill the microfilariae. Your veterinarian will select the correct drug and administration time based on your pet’s condition.

Are any other treatments necessary?

Dogs with severe heartworm disease may require antibiotics, pain relief medications, special diets, diuretics to remove fluid accumulations in the lungs, and drugs to improve heart function prior to treatment for the heartworms. Even after the heartworms have been killed, these dogs may require lifetime treatment for heart failure. This includes the use of diuretics, heart medications such as ACE-inhibitors, beta-blockers or cardioglycosides, and special low-salt diets.

What is the response to treatment and prognosis?

Dog owners are usually pleasantly surprised at the improvement in their dog following treatment for heartworms, especially if the dog had been demonstrating any clinical signs of heartworm disease. Many dogs display renewed vigor and vitality, improved appetite and weight gain.

How can I prevent my dog from getting heartworms?

You can prevent your dog from getting heartworms by using a heartworm preventive. When a dog has been successfully treated for heartworms, it is essential to begin a heartworm prevention program to prevent future recurrence. With the safe and affordable heartworm preventives available today, no pet should ever have to endure this dreaded disease.

This client information sheet is based on material written by: Ernest Ward, DVM © Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.

Hookworm Infection in Dogs

What are hookworms?

Hookworms (Ancylostoma caninum, Ancylostoma braziliense) are intestinal parasites of the cat and dog that get their name from the hook-like mouthparts they use to anchor themselves to the lining of the intestinal wall. They are only about 1/8″ (3 mm) long and so small that it is very difficult to see them with the naked eye. Despite their small size, they ingest large amounts of blood from the tiny vessels in the intestinal wall. A large number of hookworms can cause life-threatening anemia. This problem is most common in puppies, but can occur in adult dogs.

How do dogs get hookworms?

Dogs may become infected with hookworms by one or all of four routes:

  • Orally
  • Through the skin
  • Through the mother’s placenta before birth (in utero)
  • Through the mother’s milk

Female hookworms pass hundreds of microscopic eggs in the feces of infected dogs, where they contaminate the environment. Larvae hatch from the eggs and can remain infective in the soil for many, many months. A dog may become infected when it inadvertently swallows hookworm larvae, often by grooming its feet, or from sniffing feces or contaminated soil. The larvae may also burrow into the skin if the dog walks or lies on contaminated ground. Once in the host’s body, the larvae migrate to the intestine where they mature and complete their life cycle. Part of the life cycle of the hookworm involves migration through muscle tissues, where they may become dormant.

“Prenatal and transmammary infections are an important route of infection for puppies.”

If a pregnant dog had hookworms in the past, the pregnancy may reactivate dormant larvae, which then enter the female’s bloodstream and infect the puppies in the uterus or through the mother’s milk during nursing. Prenatal and transmammary infections are an important route of infection for puppies.

What are the clinical signs of hookworm infection?

The most significant clinical signs are related to intestinal distress and anemia. The parasites anchor themselves to the intestinal lining so that they can feed on tissue fluids and blood, injecting an anti-coagulant substance, which can cause continued bleeding after the hookworm has detached from the feeding site. Therefore, the dog can suffer blood loss from the hookworms’ feeding, as well as continued bleeding into the bowel from the attachment sites, causing anemia. Pale gums and weakness are common signs of anemia. Some dogs experience significant weight loss, bloody diarrhea, or failure to grow properly with hookworm infection. It is not uncommon for young puppies to die from severe hookworm infections.

Skin irritation and itching, especially of the paws, caused by larvae burrowing into and along the skin, can be signs of a heavily infested environment.

How are hookworms diagnosed?

“Hookworms are diagnosed with a microscopic examination of a stool sample…”

Hookworms are diagnosed with a microscopic examination of a stool sample by a technique called fecal flotation. The stool is mixed with a solution that causes the parasite eggs to float to the top of the solution and adhere to a glass slide placed on its surface. Since there are many eggs produced daily and the eggs have a unique appearance, hookworm infections are easily detected.

It takes 2-3 weeks for hookworm larvae to mature and begin producing eggs. For this reason, fecal examination may be less reliable in very young puppies than in adult dogs.

How is a hookworm infection treated?

There are several effective drugs, called anthelmintics, which will eliminate hookworms. Most are given orally and have few, if any, side effects. However, these drugs only kill the adult hookworms.

“It is necessary to treat an infected dog again in about two to four weeks…”

Therefore, it is necessary to treat an infected dog again in about two to four weeks to kill any newly formed adult worms that were larvae at the time of the first treatment.

Since the dog’s environment can be infested with hookworm eggs and larvae, it is critical that you remove any feces from your yard promptly. Use gloves to place the feces in plastic bags and discard in your trashcan. There are currently no approved available products to eliminate hookworm larvae from your yard. The best prevention is to remove feces from your yard daily and have your pets on a monthly heartworm preventive that also protects against hookworm infection.

Are canine hookworms infectious to people?

Adult hookworms do not infect humans; however, the larvae can burrow into human skin. This causes itching, commonly called “ground itch”, but the worms do not mature into adults. More dangerous is the condition in which hookworm larvae migrate throughout the body, damaging the eyes and internal organs. Direct contact of human skin to moist, hookworm infested soil is required. Fortunately, this is extremely rare if normal hygiene practices are observed.

In rare instances, the canine hookworm will penetrate into deeper tissues and partially mature in the human intestine. A few reports of hookworm enterocolitis (small and large intestinal inflammation) have occurred in the recent past.

What can be done to control hookworm infection in dogs and to prevent human infection?

“All puppies should be treated with a veterinary-approved anthelmintic product at two to three weeks of age.”

All puppies should be treated with a veterinary-approved anthelmintic product at two to three weeks of age. In addition, prompt deworming should be given if the parasites are detected. Periodic deworming may be appropriate for pets at high risk for infection.

Prompt disposal of dog feces should occur, especially in yards, playgrounds, and public parks.

Strict hygiene is important, especially for children. Do not allow children to play in potentially contaminated environments. Frequent hand washing and bathing are essential in preventing human infections.

Nursing females should be de-wormed with their puppies. Pregnancy and nursing may reactivate a dormant hookworm infection in the female dog, which will then infect her puppies.

Most heartworm prevention products contain medication to treat hookworm infections. Some of these products will kill the adults, while others will also kill larval stages and prevent infestations. Your veterinarian can advise you of the spectrum of activity for the product prescribed for your dog.

A fresh stool sample should be rechecked one week after your pet’s final hookworm medication to be sure that the infection has been resolved. (___)

For more reliable information about parasite related issues you can go to www.petsandparasites.org or call us with questions anytime.

This client information sheet is based on material written by: Ernest Ward, DVM © Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.

Ringworm in Cats

What is ringworm and what causes it?

“Ringworm” is the common name given to a fungal infection of the superficial layers of the skin, hair and nails. Ringworm infections can occur in humans and in all domesticated species of animals. The name comes from the classical appearance of the round, red, raised ‘ring’ marking the boundary of inflammation in people infected with the disease. The common name of ringworm is somewhat misleading, in that it is not an infection caused by a worm, and the infected areas are not always ring-shaped. The organisms that cause ringworm infections belong to a specialized group of fungi known as dermatophytes, so the medical name for this disease is dermatophytosis.

Some species of dermatophytes are species-specific, meaning that they will only infect one species, whereas others can be spread between different species of animals or from animals to man. In cats, one species of dermatophyte, called Microsporum canis, is responsible for almost all ringworm infections, and this species is infectious to cats, dogs and man. Occasionally ringworm infections in cats may be caused by species such as Trichophyton mentagrophytes. Both of these species are zoonotic, meaning that they can also infect humans.

What does ringworm look like?

“The lesions of ringworm in cats may be very mild or even undetectable.”

Ringworm can be challenging to detect in cats, since the lesions of ringworm may be very mild or even undetectable. Ringworm fungi feed on the keratin that is found in the outer layers of the skin, hair and nails. A “cigarette ash” scaling in the depths of the coat may be the only visible indicator of ringworm infection in cats. Some cats may have round thickened patches of skin with hair loss. Hair loss (alopecia) occurs when the spores infect the hair shafts, resulting in increased fragility of the infected hairs.

In cats, the main sites for these lesions are the skin on the head, chest, forelegs and along the ridge of the back. These lesions are not usually itchy. Occasionally, infection of the claws known as onychomycosis may occur. The claws become rough, pitted, and develop a scaly base; they may ultimately become deformed. Ringworm may sometimes cause a more generalized disease where a much larger area of the body is affected, often seen as patchy hair loss.

Some cats, especially longhaired breeds, may have ringworm without any clinical signs or hair loss. This condition is known as an asymptomatic carrier state. These cats may infect other animals or people, especially in shelter or multi-cat environments, without caregivers suspecting they may be infected.

How is ringworm transmitted?

“Ringworm is contagious and can be passed between infected and non-infected individuals through direct contact or by contact with contaminated objects.”

Ringworm is contagious and transmission occurs by direct contact with the fungus. It may be passed by direct contact with an infected animal or person, or by handling contaminated objects or touching contaminated surfaces.

The fungal spores may remain dormant on combs, brushes, food bowls, furniture, bedding, carpet or other environmental surfaces for many months (reportedly up to 18 months). Spores may be killed with a solution of chlorine bleach and water (one pint of chlorine bleach (500 ml) in a gallon of water (4 liters), or a dilution of 1:10 to 1:100), where it is feasible to use it.

Contact with ringworm fungus does not always result in an infection. The amount of environmental contamination is an important factor in the development of a ringworm infection, as is the age of the exposed person or animal. Healthy adult humans usually are resistant to infection unless there is a break in the skin such as a scratch. Elderly people, young children, and adults with immune system weaknesses or skin sensitivities are especially susceptible to ringworm infection. If your child has ringworm, he or she may have acquired it from your pet or from another child at school. If you or any of your family members develop suspicious skin lesions, see your family physician immediately.

How long does it take to get it?

The incubation period between exposure to ringworm fungus and the development of ringworm lesions usually ranges from seven to fourteen days; some cases may take up to 21 days before signs of infection develop.

How is a ringworm infection diagnosed?

The majority of cases of feline ringworm caused by M. canis will glow with a yellow-green fluorescence when the skin and coat are examined in a dark room under a special ultraviolet lamp called a Wood’s lamp. However, not all cases show clear fluorescence and some other dermatophytes like Trychophyton mentagrophytes do not fluoresce. Some skin ointments and other materials will fluoresce and may give a false positive result.

The preferred method for diagnosing ringworm in cats is by culture of the fungus in a laboratory. For this, samples of hair and skin scrapings are taken. A positive culture can sometimes be confirmed within a couple of days, but in some cases the fungal spores may be slow to grow, and culture results can take up to four weeks, meaning that a suspected case cannot be called negative for at least a month. Cats are often tested after one to two weeks of treatment, and then at weekly intervals until two consecutive ringworm cultures are obtained.

There are numerous causes of hair loss in cats. Before making a diagnosis of ringworm, your veterinarian may recommend additional testing to rule out some of these causes.

How is ringworm treated?

“…treatment of the disease is always indicated to minimize the spread of the infection…”

Although ringworm is a self-limiting infection in many cats, with resolution typically taking three to five months, treatment of the disease is always indicated to minimize the risk of spread of infection to humans, especially children, and other pets.

The most common way to treat ringworm in cats is to use a combination of topical therapy (application of creams, ointments or shampoos) and systemic oral therapy (administration of anti-fungal drugs by mouth). In order for treatment to be successful, all environmental contamination must be eliminated.

1. Topical treatment

Occasionally, topical therapy is used alone for treatment of ringworm, but more commonly it is used in combination with oral medication. Various creams and ointments are available to apply to localized areas of the skin affected by ringworm. If there are only one or two affected areas, shaving of the hair from these areas may be sufficient. If there is more generalized disease, or if your cat is a longhaired breed, your veterinarian may recommend clipping the pet’s hair short to aid in treatment, along with bathing the cat with a medicated shampoo, typically twice a week. It is extremely important only to use preparations that have been specifically provided or recommended by your veterinarian. Topical treatment will usually be necessary for a period of several weeks to several months.

After bathing or treating your cat, be sure to wash your hands and sanitize any surfaces your cat been in contact with.

2. Oral treatment

In the majority of cases of ringworm, effective treatment will require administration of an oral anti-fungal drug. The most widely used drug for this purpose has traditionally been griseofulvin, although newer drugs such as itraconazole or terbinafine (Lamasil) are being used more frequently and are often preferred since they have fewer side effects. The response of individual cats to a treatment varies, and if therapy is stopped too soon, the disease may recur. Treatment must usually be continued for a minimum of six weeks, and in some cases, much longer therapy is required. Ringworm cultures are generally taken one to two weeks after the start of treatment to determine if your pet is still infected, and treatment is typically continued until two consecutive negative ringworm cultures are obtained.

If there is more than one pet in the household, try to separate infected from non-infected animals and just treat the infected ones. In some situations, it may be preferable to treat all of the pets. Your veterinarian will advise you on the best treatment given your individual circumstances.

3. Environmental cleaning

Infected hairs contain numerous microscopic fungal spores that can be shed into the environment. Infection of other animals and humans can occur, either by direct contact with an infected cat or through contact with fungal spores in a contaminated environment. In addition to minimizing direct contact with an infected cat, it is also important to attempt to keep the environment free of spores.

“It is also worthwhile to restrict the cat to certain rooms of the house that are easy to clean.”

Clipping of infected hairs (with careful disposal) combined with topical antifungal treatment of affected areas of skin may help to reduce environmental contamination. Damp mopping or using electrostatic cleaners will aid you in removing pet hair from floors and furniture.

It is also worthwhile to restrict the cat to certain rooms of the house that are easy to clean. Environmental contamination can be minimized by thorough damp mopping or vacuuming of all rooms or areas that are accessible to your cat; this should be done as frequently as is possible (e.g. daily). In addition, the use of diluted bleach (1:10 to 1:100 bleach to water dilution) is recommended in areas that can be readily disinfected.

In multi-animal facilities such as animal shelters or kennels, treatment of ringworm can be extremely challenging and costly, and environmental contamination can be difficult to contain..

How long will my cat be contagious?

Infected pets remain contagious for about three weeks if aggressive treatment is used. The ringworm will last longer and remain contagious for an extended period of time if only minimal measures are taken or if you are not faithful with the prescribed approach. Minimizing exposure to other dogs or cats and to your family members is recommended during this period.

Ringworm cultures are generally taken several weeks after the start of treatment to determine if your pet is still infected. Typically two consecutive negative ringworm cultures indicate your cat has been successfully treated.

Will my cat recover from ringworm?

The vast majority of cats, if treated appropriately, will recover from a ringworm infection within a few weeks. While the appearance of the lesions may not change much during the first week or so of treatment, some improvement should be evident within two to three weeks. Symptoms may recur if the treatment was discontinued too early or was not aggressive enough (i.e. only topical treatment was used), or if the pet has some underlying disease compromising the immune system. Occasionally, despite appropriate treatment, the infection persists, and in this situation, your veterinarian may have to try alternative anti-fungal drugs.

What is the risk to humans?

Ringworm can be transmitted quite easily to humans, particularly children, and it is important to take appropriate steps to minimize exposure to the fungus while the cat is being treated (see Environmental Cleaning above).

“If any humans in the house develop skin lesions, especially small patches of skin thickening and reddening with raised scaly edges, early medical attention should be sought.”

If any humans in the house develop skin lesions, especially small patches of skin thickening and reddening with raised scaly edges, early medical attention should be sought. Ringworm in humans generally responds very well to treatment. However, the ringworm fungus can remain infective for up to 18 months in the environment and re-infection may occur.

This client information sheet is based on material written by: Ernest Ward, DVM © Copyright 2010 Lifelearn Inc. Used and/or modified with permission under license.

Roundworm Infection in Cats

What are roundworms?

Roundworms are one of the most common intestinal parasites of the cat. They can be an important cause of illness, even death, in kittens. As their name implies, these are large-bodied round worms, averaging about 3-6 inches (8-15 cm) in length. They do not attach to the wall of the intestine, as some intestinal parasites do. Instead, they are literally “swimming” freely within the intestine.

The scientific name for the feline roundworm is Toxocara cati. Another less common roundworm, Toxascaris leonina, can infect both dogs and cats. Roundworms are sometimes called ascarids and the disease they cause is called ascariasis.

What are the clinical signs of roundworm infection?

“…large numbers may cause life-threatening problems in kittens and debilitated older cats.”

Roundworms are not particularly pathogenic or harmful to adult cats, but large numbers may cause life-threatening problems in kittens and debilitated older cats. In kittens, common clinical signs include a pot-bellied appearance, abdominal discomfort, depressed appetite, vomiting and diarrhea, or poor growth.

In both kittens and adult cats with small numbers of worms, there may be no clinical signs of infection.

How do cats get roundworms?

Trans-mammary or milk-borne infection is the major route of roundworm transmission in kittens. The immature roundworms called larvae are present in the mother’s mammary glands and pass through her milk to the kittens during nursing.

Both kittens and adult cats may become infected by swallowing eggs that contain infective roundworm larvae. These eggs may come from the feces of infected cats or from the tissues of paratenic hosts. In a paratenic host, the roundworm eggs do not mature into adults, but are merely transported. If a cat eats the paratenic host, the roundworm is able to complete its maturation. Common paratenic hosts for roundworms include earthworms, cockroaches, rodents and birds.

The lifecycle of the roundworm is complicated. Once ingested, the larvae hatch out in the cat’s gastrointestinal tract and migrate through the muscle, liver, and lungs. Some of these larvae may encyst in a dormant in these organs for years before migrating back to the intestines or even to the kittens across the placenta or through the milk. Most, however, return to the intestine within a few weeks to mature into adults. When the adult worms begin to reproduce, eggs will pass into the cat’s stool, thus completing the life cycle of the parasite.

How are roundworms diagnosed?

To diagnose roundworm infection, a small amount of the cat’s stool is mixed in a special solution that causes the eggs to float to the top of the solution. The sample is covered with a glass slide on which the floating eggs will collect, and the slide is examined under a microscope.

“The distinctive eggs are easily recognized under the microscope.”

The distinctive eggs are easily recognized under the microscope. Roundworm eggs are usually plentiful but, in some cases, it may take more than one fecal examination to find them. Occasionally, intact adult roundworms can be found in the cat’s stool or vomit.

What is the treatment for roundworms?

Fortunately, the treatment for roundworms is safe, simple, and relatively inexpensive. The dead and dying roundworms pass into the stool after administration of the anthelmintic or deworming medication. Since none of these treatments will kill the encysted forms of the worm or the migrating larvae, some cats may need repeated treatments during their life. Ideally, kittens are dewormed with each visit for booster vaccinations. If your adult cat goes outdoors, you may wish to administer doses of an anthelmintic every 3 months to prevent problems.

All cats should have their stools rechecked after deworming for roundworms to ensure that treatment was successful.

What is the prognosis for a cat diagnosed with roundworms?

The prognosis of a roundworm infection is good if appropriate medication is given promptly. However, in some instances, extremely debilitated kittens may die.

Can I prevent my cat from getting roundworms?

Prevention of roundworm infection should include the following measures:

  • Breeding queens (females) should be dewormed prior to pregnancy and again in late pregnancy. This will reduce the risk of environmental contamination or transmission from the mother to her new kittens.

“First deworming should be given at two to three weeks of age.”

  • Kittens should be appropriately dewormed as recommended by your veterinarian. The first deworming should be given at two to three weeks of age. Note that this is prior to the time most kittens are seen for first vaccines. It is entirely appropriate to present new kittens for initial examination and deworming only.
  • Adult cats remain at risk for re-infection with roundworms throughout their lives. Whenever roundworms are seen, the cat should be promptly dewormed. It is appropriate to routinely deworm all cats that remain at high risk for re-infection. For example, it is advisable for cats with predatory habits or indoor/outdoor cats to have a fecal examination several times a year or even to be prophylactically dewormed quarterly..
  • Control of insects and rodents is important since they may serve as sources of roundworm infection for cats.
  • Stool should be removed from litter boxes daily, if possible. Litter boxes can be cleaned with a soap and water to facilitate removal of eggs. Always wash your hands after handling litterbox material.
  • Appropriate disposal of cat and dog feces, especially from yards and playgrounds, is important. Roundworm eggs may remain viable in the environment for long periods unless they are exposed to direct sunlight or very dry conditions.
  • • Strict hygiene is especially important for children. Do not allow children to play in potentially contaminated environments. Be mindful of the risk that public parks and non-covered sandboxes pose. Even though stool may not be visible, roundworm eggs may be present. Sandboxes that have fitted covers are popular and help prevent infection of children with roundworms.
  • Contact your animal control officials when homeless animals are found.

Are roundworms a danger to my family or me?

Roundworms can be a health risk for humans. The most common source of human infection is by ingesting eggs that have come from soil contaminated with cat (or dog) feces.

“In suitable environments, the eggs may remain infective to humans and cats for years.”

As many as 10,000 cases of roundworm infection in humans have been reported in one year in the United States. Children are at an increased risk for health problems should they become infected. A variety of organs, including the eyes, may be affected as the larvae migrate through the body. In suitable environments, the eggs may remain infective to humans and cats for years. Because of the potential to affect people,Kingsbrook Animal Hospital recommends deworming all puppies and kittens for roundworms.

This client information sheet is based on material written by: Ernest Ward, DVM © Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.

Roundworm Infection in Dogs

Roundworms (nematodes or ascarids) are parasites that live freely in the intestine, feeding off of partially digested intestinal contents. Their name is derived from their tubular or “round” shape.

Toxocara canis and Toxascaris leonina are two important species of roundworms in dogs. Toxocara canis causes more significant disease and also may be transmitted to humans.

How did my dog get roundworms?

Infected dogs shed the microscopic roundworm eggs in their feces. Other dogs may become infected by sniffing or licking infected feces. Roundworm eggs can also be spread by other animals such as rodents, earthworms, roaches and birds. In these animals, the roundworms are merely transported, and do not mature into adults; if a dog eats this “paratenic” host, the roundworm is liberated and completes its maturation.

“In the dog, the roundworm undergoes a complicated life cycle.”

In the dog, the roundworm undergoes a complicated life cycle before mature roundworms are found in the intestinal tract. This involves several stages and includes migration through various bodily tissues. Roundworm larvae (immature worms) can migrate and encyst throughout the host’s body. This is important in the female dog because these encysted larvae will start to develop during pregnancy and ultimately cross the placenta into an unborn puppy. Thus puppies can be born with roundworms and can pass fertile eggs from adult worms in their stools by the time they are approximately eleven days old. Roundworm larvae may also enter the mother’s mammary glands and be transmitted through the milk.

Are roundworms a threat to my dog?

“The most common consequence of roundworms is growth reduction.”

Roundworms are most threatening to puppies. The most common consequence of roundworms is growth reduction. Since roundworms eat partially digested food in the intestinal tract, if there is a large burden of roundworms they will rob the growing puppy of vital nutrients.

The life cycle of Toxocara canis is more complicated than that of other nematode worms found in dogs. Roundworms can complete their life cycle in immature dogs, but as the pup’s immune system matures (usually by 6 months of age), the larval stages will become “arrested” or encyst in the pup’s muscles Roundworm larvae swallowed by adult dogs usually encyst in the dog’s tissues. Few roundworms will mature in the bowel of infected adult dogs. Consequently few eggs are passed in the stool leading to difficulty in definitive diagnosis and treatment.

In intact female dogs, encysted Toxocara canis larvae can resume development after estrus, and she can shed eggs in the stool at that time. With dogs that have been spayed or castrated, development of a roundworm infection may indicate that there is an underlying immune system disease that has allowed the encysted larvae to complete their life cycle.

Toxascaris leonina can complete their life cycle in any age of dog, or in cats.

How are roundworms diagnosed?

“In puppies, clinical signs such as stunted growth, potbelly, and recurrent diarrhea are a good indication of roundworm infection.”

In puppies, clinical signs such as stunted growth, potbelly, and recurrent diarrhea are a good indication of roundworm infection. Definitive diagnosis is made by microscopic examination of the dog’s feces.

Is it true that children can get roundworm infections?

If the infective eggs of Toxocara canis are swallowed by people, the larvae can invade the tissues and become encysted in various organs. Humans act like any other paratenic or accidental host. If a young child ingests a large number of infected eggs, clinical disease may become apparent.

Very rarely, liver problems may result from roundworm larval migration (visceral larval migrans). Even less commonly, the larvae can migrate into the eye and cause blindness (ocular larval migrans). Because of the risk of roundworm infection in humans, it is recommended by the Centers for Disease Control (CDC) that all dogs be de-wormed monthly. Modern monthly heartworm preventives also prevent roundworm infections and are highly recommend for all dogs and cats.

“Because of the risk of roundworm infection in humans, it is recommended by the Centers for Disease Control (CDC) that all dogs be de-wormed monthly.”

Because of the risk of roundworm infection in humans, it is recommended by the Centers for Disease Control (CDC) that all dogs be de-wormed monthly. Modern monthly heartworm preventives also prevent roundworm infections and are highly recommend for all dogs and cats.

How are roundworms treated?

Treatment is simple and effective. There are many safe and effective preparations available to kill adult roundworms in the intestine

Many heartworm preventives contain medications that are effective against intestinal roundworms help prevent future infections. Some of these preparations only the adult worms and do not affect migrating or encysting larvae. New products have recently been developed that will also affect the larval stages. Your veterinarian will advise you on the best treatment and prevention plan for your pet.

What about roundworm eggs shed in the environment?

Initially the eggs are not infective. After a period, which may vary from weeks to months, the eggs develop into infective larvae. Under ideal conditions, this takes approximately four weeks. These infective larvae can remain viable in the environment for long periods of time and are particularly resistant to changes in temperature and humidity.

The best environmental treatment is prevention. Remove your dog’s feces as soon as possible to prevent the spread and transmission of roundworms.

What is the most effective strategy I can use to control infection in my dogs, protect my family and reduce contamination of the environment?

Deworm pregnant dogs in late pregnancy, after the 42nd day or after six weeks of pregnancy. This will help reduce potential contamination of the environment for newborn puppies.

All puppies should be dewormed routinely, starting at about two weeks of age and repeated regularly. Your veterinarian will design the most appropriate deworming schedule for your pets.

The use of a heartworm preventative product that is effective against roundworms will stop the shedding of eggs into the environment.

Rodent control is important since rodents can serve as a source of infection.

Dogs should be prevented from defecating in children’s play areas and there should be prompt disposal of all dog feces, especially in gardens, playgrounds and public parks.

“Practice strict hygiene particularly with children.”

Practice strict hygiene particularly with children. Do not allow them to play in potentially contaminated environments and ensure proper and frequent hand washing.

This client information sheet is based on material written by: Ernest Ward, DVM © Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license

Tapeworm Infection in Cats

What are tapeworms?

Tapeworms are intestinal parasites of the cat and dog. They are classified as cestodes. They belong to a different family than hookworms and roundworms, which are the other common intestinal parasites of dogs and cats. Several types of tapeworms are known to infect cats. Dipylidium caninum is by far the most common species observed in cats.

The tapeworm uses its hook-like mouthparts for anchoring to the wall of the small intestine. Eventually, adult tapeworms may reach several inches in length. As the adult matures, individual segments called proglottids break off from the main body of the tapeworm and pass into the cat’s feces.

Are certain cats more likely to get Dipylidium caninum tapeworms?

“Fleas are the intermediate host for Dipylidium caninum.”

Fleas are the intermediate host for Dipylidium caninum. In other words, the tapeworm is unable to complete its life cycle without the presence of fleas in the environment. Regardless of whether the owner may have seen fleas, the cat must have ingested a flea in order to have tapeworms. Consequently, tapeworms are more common in environments that are heavily infested with fleas. Lice are also reported as intermediate hosts for this tapeworm but they are relatively uncommon parasites of cats.

How do cats get Dipylidium caninum tapeworms?

First, tapeworm eggs must be ingested by flea larvae, an immature stage of the flea. Contact between flea larvae and tapeworm eggs are facilitated by contaminated bedding or carpet. Adult fleas do not participate in this part of the tapeworm lifecycle. The infected flea larvae will mature into adult fleas.

Next, the cat chews or licks its skin in response to a fleabite, and inadvertently swallows the flea. As the flea is digested within the cat’s intestine, the tapeworm is released and it hatches and anchors itself to the intestinal lining.

What are the clinical signs of tapeworm infection?

Tapeworms are not particularly harmful to the cat and few clinical signs are attributed to their presence.

“…owner’s aversion to the presence of the crawling proglottids or tapeworm segments.”

Usually, the cat is brought to the veterinarian because of the owner’s aversion to the presence of the crawling proglottids or tapeworm segments. Rarely, tapeworms may cause debilitation or weight loss if they are present in large numbers. A cat will occasionally scoot or drag its anus across the ground or carpet due to the anal irritation caused by the proglottids. However, this behavior is much more common in dogs than cats.

Occasionally, a tapeworm will release its attachment in the intestines and migrate to the stomach. When this happens, the cat may vomit an adult tapeworm several inches in length.

How are tapeworms diagnosed?

Most commonly, owners recognize that the cat has tapeworms and bring this to the attention of the veterinarian. When terminal segments of the tapeworm break off and pass into the cat’s stool, they can be seen crawling on the surface of the feces. These proglottid segments look like grains of cooked white rice or cucumber seeds. Less commonly, segments are seen moving around the cat’s anus. Each of these proglottid capsules contains up to twenty tapeworm eggs.

When these proglottids are released into the environment, they dehydrate and harden, becoming smaller and taking on a golden hue. Eventually, they break open and release their contents. You should note that tapeworms are not readily diagnosed with routine fecal examinations. Because of this, you should notify your veterinarian when tapeworm segments are found in your cat’s stool.

What is the treatment for tapeworms?

A variety of products are available to treat tapeworms in cats but they are not all equally effective. For the best advice on the type of de-worming preparation most suitable for your cat, you should seek the help of your veterinarian. The most effective worming products are only available by prescription from a licensed veterinarian.

The deworming medication called an anthelmintic may be given as a tablet or oinment that is placed on the skin. After treatment, the tapeworm dies and is usually digested within the intestine, so worm segments don’t usually pass into the stool. Side effects, such as vomiting and diarrhea, are rarely reported with the newer tapeworm medications.

“Flea control is the cornerstone of preventing Dipylidium caninum infection.”

Flea control is the cornerstone of preventing Dipylidium caninum infection. If the cat lives in a flea-infested environment, tapeworm infection can become re-established within a few weeks. This is very rarely due to treatment failure; in most cases, reappearance of tapeworm segments represents re-infection of the cat. Additional recommendations include:

1. Promptly have your cat treated when tapeworms are detected.

2. Remove and dispose of all pet feces properly, especially in public parks, yards, or playgrounds.

3. Teach and practicestrict hygiene practices for children after playing outdoors.

What is the prognosis?

New tapeworm medications and flea preventives are safe and effective. The prognosis for successful treatment is excellent. In most cases, prevention is successfully accomplished by using a monthly flea preventive.

Are Dipylidium caninum tapeworms from my cat dangerous to my family or me?

Humans can become infected with tapeworms, although infection is rare because it is requires ingestion of a flea. Most reported cases have involved children living in less-than-ideal conditions. The risk for human infection with Dipylidium caninum is quite remote but does exist.

What are the other tapeworms that can infect my cat?

The other common tapeworms that can infect a cat are members of a group called Taenia. The intermediate hosts of these tapeworms are mice, birds, or rabbits.

“…cats acquire Taenia infestations by eating infected mice, birds, or rabbits.”

In a similar manner to Dipylidium transmission, cats acquire Taenia infestations by eating infected mice, birds, or rabbits. Tapeworm medications are highly effective at eliminating these parasites. However, if your cat continues to eats prey, reinfection can occur with passage of tapeworm segments in 6-8 weeks.

Another less common group of tapeworms called Echinococcus is of increasing concern as a threat to human health. These tapeworms cause serious, potentially fatal, disease when humans become infected. Infection with this parasite is harder to diagnose than Dipylidium because the segments are small and not readily seen. Trappers and hunters in the north central United States and south central Canada may be at increased risk for infection with this worm when strict hygiene is not practiced. Foxes, coyotes, and the wild rodents upon which they prey are important in the life cycle of this parasite. Dogs and cats may also become infected if they eat rodents carrying the parasite. When eggs of Echinococcus are passed in the feces of the dog and cat, humans are at risk for infection. Free-roaming cats and dogs may need to be periodically treated with tapeworm medication. Rodent control and good hygiene are important in preventing the spread of this disease to humans. As with the more common tapeworm, human infection with Echinococcus is rare yet possible.

My child has pinworms. Did they come from my cat?

Tapeworms and pinworms look very similar. However, contrary to popular belief, pinworms do not infect cats or dogs. Any worm segments seen associated with cats are due to tapeworms. Children who contract pinworms do not get them from cats or dogs.

For more information on parasite related issues you can go to www.petsandparasites.org or feel free to call us with questions anytime.

This client information sheet is based on material written by: Ernest Ward, DVM © Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.

Tapeworm Infection in Dogs

What are tapeworms?

Tapeworms are flat intestinal worms that are made up of many small segments, each about ¼ – ½” (3-5 mm) long. Unlike roundworms that live freely in the intestinal tract, tapeworms attach to the wall of the small intestine using hooklike mouthparts.

Tapeworms belong to the cestode family of intestinal worms. The most common tapeworm of dogs and cats is Dipylidium caninum. The adult worms may reach up to 8 inches (20 cm) in length. The individual segments begin to develop starting behind the head and move down the tapeworm as they gradually mature, finally being shed at the opposite end, either singly or in short chains. These segments, called proglottids, are passed in the feces when an infected dog defecates. They are about 1/8″ (3 mm) long and look like grains of rice or cucumber seeds. Occasionally they can be seen moving on the hairs around the anus or on the surface of freshly passed feces. As the tapeworm segment dries, it becomes a golden color and eventually breaks open, releasing the fertilized eggs into the environment.

Unlike roundworms, dogs cannot become infected by eating fertilized tapeworm eggs. Tapeworms must first pass through an intermediate host (a flea) before they can infect a dog.

How do dogs get tapeworms?

When the infected eggs are released into the environment, they have to be swallowed by immature flea larvae in the environment. Once inside the larval flea, the tapeworm egg continues to develop as the flea matures into an adult flea. During grooming or in response to a flea bite, a dog can ingest the tapeworm infected flea and complete the life cycle.

Are tapeworms dangerous for my dog?

Tapeworms do not normally cause serious health problems in dogs, but they are REALLY gross. Occasionally dogs will drag their bottoms on the ground, a behavior known as scooting, in order to allay this irritation. Note that scooting can also occur for other reasons such as impacted anal sacs. Kingsbrook Animal Hospital 5322 New Design Road, Frederick, MD, 21703 Phone: (301) 631-6900 Website: KingsbrookVet.com In puppies, heavy tapeworm infestation can be more serious. Lack of growth, anemia and intestinal blockages can occur. Occasionally, the head of the tapeworm or scolex detaches from the intestinal wall; the entire adult tapeworm will then be passed in the feces or vomited up.

How is a diagnosis made?

Clinical diagnosis is usually made by observing the white mobile tapeworm segments in the feces or crawling around the anus. They often look like grains of rice.

Tapeworm segments are only passed intermittently and therefore are often not diagnosed on routine fecal examination. If you find any segments, white or golden color, bring them to your veterinarian for a definitive diagnosis.

What is the treatment?

With today’s drugs, treatment is simple and effective. It causes the parasite to dissolve in the intestines so you normally will not see tapeworms passed in the stool. These drugs are very safe and should not cause any side effects.

Is there anything else I should do?

“Flea control is critical in the management and prevention of tapeworm infection.”

Flea control is critical in the management and prevention of tapeworm infection. Flea control involves treating the dog and the environment. Your veterinarian can recommend a safe and effective flea control for your pet. If your dog lives in a flea-infested environment, re-infection with tapeworms may occur in as little as two weeks. Since tapeworm medication is so effective, recurrent tapeworm infections are almost always due to re-infection from fleas and not failure of the product.

Can I get tapeworms from my dog?

You cannot get tapeworms directly from your dog. Dipylidium caninum, the most common canine tapeworm, depends on the flea as the intermediate host. A person must swallow an infected flea to become infected. A few cases of tapeworm infection have been reported in children. Vigorous flea control will also eliminate any risk of children becoming infected.

Although Dipylidium species are the most common tapeworms in dogs, other cestodes are also important in certain areas.

Taenia species – These tapeworms are the second most common type that we see in dogs. They are acquired by eating prey or waste containing the infective larval stage. These are much larger tapeworms, often up to one yard (one meter) in length. Intermediate hosts include rodents, rabbits, hares and sheep. The intermediate stages develop hydatid cysts in various organs in the intermediate host. There are effective medications that will eliminate Taenia infections in dogs. If your dog eats prey such as rodents or rabbits, re-infection can occur with passage of tapeworm segments in 6-8 weeks.

Echinococcus species – These are very small tapeworms, consisting of only three or four segments, and are usually less than 3/8″ (1 cm) in length. Intermediate hosts can be sheep, horses and occasionally man. In humans the disease is called hydatidosis, hydatid disease, or hydatid cyst disease, and results in cysts being formed in the liver. The disease is very rare in the United States, but has been reported in California, Arizona, New Mexico and Utah. Humans are infected by eating contaminated meat or by accidentally ingesting eggs that have originated from the feces of dogs, coyotes or foxes harboring the adult tapeworm. Fortunately, de-worming preparations, particularly those containing praziquantel, are effective for eliminating this cestode from infected dogs.

Prevention of cestode tapeworm infection involves avoidance of uncooked or partially cooked meat or meat by-products.

For more reliable information on parasite related issues you can go to www.petsandparasites.org or feel free to call us with questions anytime.

This client information sheet is based on material written by: Ernest Ward, DVM © Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.