angio

Angiostrongylus vasorum

French Heartworm

Angiostrongylus Vasorum is a nematode (parasitic worm) from foxes that has also finds its way into dogs. Commonly found in domestic dogs, red foxes and other canids in continental Europe, and North and South America, but it has recently entered England and Ireland and found its way over to the Atlantic provinces of Canada. It was first discovered in France and, for this reason, is commonly called French heartworm or simply heartworm. Although it is called heartworm, it actually lives in the lung arteries of its definitive host, such as foxes and dogs. The disease is not easily treated in dogs and, since foxes have been implicated as a reservoir, this is a matter of concern.

In affected dogs, disease will depend upon the severity of the infection and the dog’s own ability to defend itself against infection (such as breed variation, age, other existing disease conditions). Signs of illness are usually chronic, often seen months or years after infection by such general problems as decreasing tolerance to exercise, laboured breathing, coughing, loss of appetite, and weight loss. More rapid changes can occur if worms directly or indirectly go to other parts of the body including the kidneys and brain. In infected areas, dogs kept together (such as in
kennels, or packs of hunting dogs) have a greater chance of spreading the disease amongst themselves.

Adult Angiostrongylus Vasorum are slender pinkish worms approximately 14 to 20 mm in length. The males are bursate, and the females have a “barber pole” appearance from the red intestine intertwined with the white reproductive tract. Females lay eggs that develop and hatch first-stage larvae that are 310 to 400 μm long with anterior cephalic buttons and tails with a dorsal spine.

For dogs to become infected it requires an intermediate host (slugs and snails) and a definitive host (foxes and dogs), although frogs that have eaten infected slugs and snails have also been implicated in the transmission to dogs and, presumably, foxes.

In the case of Angiostrongylus Vasorum, dogs acquire infections by the ingestion of the slug and snail intermediate hosts. Some dogs might not eat slugs and snails on purpose, but they might do so by accident - e.g. when a slug or snail is sitting on a bone or favourite toy! In fact research has shown that infective worm larvae can also be released from the slug or snail in the slimy trail they leave behind. So potentially larvae can be found wherever slugs or snails have left their trails such as puddles and outdoor drinking water bowls or even on your dogs treats or toys. Slugs and snails eat the first-stage larvae while feeding on the feaces of infected canids. When the third-stage larvae in the snail or frog are eaten by the dog, they penetrate the gut wall and develop in abdominal lymph nodes before entering the portal circulation and moving to the pulmonary arteries and right ventricle. In the lungs, the worms mature, mate, and produce eggs that lodge and develop in capillaries. Larvae that hatch from the eggs move into an airspace, are coughed up and swallowed to be passed in the feaces.

This disease has severe consequences for the infected animal. Angiostrongylus Vasorum causes an inflammatory reaction with the subsequent involvement of the surrounding lung tissue that may be accompanied by interstitial pneumonia, emphysema, thromboarteritis, coagulopathis, anemia, melena, hemoptysis, and congestive right heart failure and death. Aberrant migrations of adults larvae have been found in the eye, left ventricle, and femoral artery where as the first-stage larvae have been found in the brain, spinal chord, eye, kidney, liver, skeletal muscle, intestine, stomach, pancreas, spleen, adrenal gland, and thyroid gland.

Signs of infestation that you will notice will include coughing, breathing difficulties and unexplained bleeding problems, including spontaneous bruising and bleeding into the eye.

Stages

1. The adults of Angiostrongylus Vasorum live in the heart and pulmonary arteries. The worms lay eggs which hatch into larvae and pass into the airways of the lung.

2. The larvae are then coughed up and swallowed, passing out in the dogs pooh. Once into the environment, the contaminated feces are fed on by other snails, which then become infected.

3. Slugs and snails then swallow the larvae which develops within the snail and is now ready to infect another host, poseing a threat to young and inquisitive dogs, though dogs of all ages can be affected.

Infections are associated with chronic cough, dyspnea, exercise intolerance, and anorexia; gagging and weight loss are the most common clinical signs of infection. Pulmonary hemorrhage can occur as larvae migrate into airspaces. Granulomas develop in response to eggs and larvae, and fibrosis occurs. Pulmonary vascular lesions include thromboarteritis and intimal proliferation; pulmonary hypertension can lead to congestive right heart failure.

Diagnosis
The majority of dogs that have been diagnosed were less than 2 years of age. There are three syndromes although a single animal may show aspects of more than one syndrome.

1. Cardiorespiratory (heart and lung) signs include coughing, reduced ability to exercise, rapid or laboured breathing, collapse and occasionally coughing up blood.

2. Coagulopathy (clotting) signs include haematomas (large blood filled cavities under the skin,) anaemia (Paleness around the eyes and gums) epistaxis (nose bleeds), bleeding into the eye, bruising and prolonged bleeding from accidental or surgical wounds.

3. Neurologic signs include weakness, depression, seizures, ataxia (drunken movement), behavioural changes and blindness, spinal pain, weight loss, loss of appetite, vomiting and diarhoea. These are due to larva that have become 'lost' and migrated the wrong way.

Dogs can be examined for this disease quite easily through the laboratory analysis of fresh feces. Though a single sample with no evidence of worms does not guarantee freedom from infection (as the worms are not shed on a continual basis), a series of tests will be able to indicate whether the animal is infected or not. Diagnosis may be presumptive as a result of clinical signs or chest radiographs or may be confirmed by fecal examinations. For Angiostrongylus Vasorum, larvae are detected in feaces using the Baermann technique or fecal flotation. Larvae are less reliably detected on fecal flotation. Multiple fecal samples may need to be examined. Radiographic changes may include diffuse peribronchial, interstitial and alveolar densities. Multiple nodular-like densities may occur in the peripheral regions of the caudal lung lobes, and enlargement of the right heart and pulmonary artery may also be visible.

Treatment
Treatment is aimed at killing the parasite and controlling the clinical signs until the infection is cleared. Your vet will prescribe a monthly spot-on treatment. According to Susan Shaw of the University of Bristol's School of Clinical Veterinary Science, there are just two drugs on the UK market licensed for treating AngioStrongylus Vasorum: Milbemycin and Moxidectin. No drug is currently licensed for preventive use. Severe dyspnea and ascites may be seen after treatment; bronchodilators, expectorants, and diuretics may be required to manage these post-treatment reactions. Severe signs may require intensive medical treatment and fatalities may still happen in severely affected animals. Prevention revolves around breaking the cycle of infection. Feces should be disposed of, control access of animals to slugs and snails, and treat with an effective worming product on a regular basis. Note that routine wormers are not effective. As foxes may be a major source of infection they should be discouraged from scavenging in the garden by removal of any food sources.

If you notice any of the symptoms described above or it seems your dog may be at risk, it is important that you talk to your vet. Early diagnosis and treatment will give your dog the best chance of a complete recovery.

Prevention
Other than the precautionary measures generally used for sanitary purposes (regularly washing out kennels, control of slugs and snails), or
the avoidance of potentially affected wild areas, there is no specific preventative measure for this disease. Pets can be protected by minimizing the amount of hunting that the animals do. Fencing and mollusk control could also help to minimize the infection in dogs. Dogs that are dewormed on a regular basis would have some protection against this disease if the dewormer used had activity against this parasite. Foxes kept on farms would not be at risk from the disease unless they came into the farm infected or were kept where infected slugs and snails could live.

Public Health Considerations
Most of these nematodes do not infect people. There have been rare reports of human infections with E.S aerophilus in Russia and Morocco. (Companion Animal Parasite Council)

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French HeartWorm

French heartworm ("Angiostrongylus Vasorum") can cause serious illness and is spreading within the UK. A recent case in Glasgow proved that the worm has moved beyond its usual territory in the South East. The affected dog had never left the area.

Dogs that eat slugs and snails risk swallowing the worm, but it is not passed on in dog faeces or from dog to dog. Signs of infestation include coughing, bleeding or collapse. Close examination may show worms within the eye or patches of bruising under the skin.

Treatment is available, but is most effective in midly affected dogs. Wormers can be ordered only through your veterinary practice. Supermarket brands are not licensed for treatment. Dogs that have lost blood may require hospital care and may die. Prevention is very difficult as inquisitive, outdoor dogs are prone to infection.
Harvey Caruthers 2008

Angiostrongylosis

Advocate

The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinarian for confirmation of any diagnosis. Your pets life may depend on it.