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Hayley de Ronde

Feb 01, 2022

Edited: Feb 01, 2022

Endoparasites of UK Canids: I

in Health and Behaviour

A happy, healthy fox is easy to identify. If you believe your fox is unwell, please seek veterinary advice.

Helminth Infections of UK Foxes

Helminth infections are diseases in which a part of the body is infected with parasitic worms (helminths). There are numerous species of these worm parasites, which are broadly classified into; tapeworms, heartworms, lungworms, roundworms, hookworms, whipworms and flukes - most of which are zoonotic (infecting both humans and animals).

Food Hygiene isn’t just important for us and our pets, it is just as vital for wildlife we are feeding also. Do not under-estimate how planting and good hygiene can go a long way to support wildlife, your pets and yourself.

Some examples of such parasites found in UK foxes can be seen listed below:

Tapeworm

Echinococcus multilocularis (Hydatid Worm)
Echinococcus granulosus (Dog Tapeworm)
Dipylidium caninum (Flea Tapeworm)
Taenia serialis (Fox/Canid Tapeworm)
Mesocestoides spp. (e.g. Pork Tapeworm)

Introduction and Background

Helminths are a broad range of organisms that include many different parasites, including intestinal parasites such as tapeworms. Foxes can pick up tapeworms by ingesting infected fleas, prey items and scavenged food.

Infected foxes then excrete tapeworm eggs or segments, in their faeces, which then contaminates the soil and vegetation, to be consumed again by other parasites, animals or even humans. Infestation can cause morbidity, and sometimes death through compromising nutritional status.

Clinical Signs

Foxes harboring many worms may present with pale mucous membranes and may develop an acute normocytic, normochromic anemia, followed by hypochromic, microcytic anemia due to iron deficiency.

Common signs include:

Increased appetite
Diarrhoea (worm segments or eggs may be visible)
Vomiting (worm segment or eggs may be visible)
Itching/scratching around the anus (scooting)
Lethargy and disinterest in activity
Poor skin and coat condition
Unexplained weight loss
Abdominal distension
Changes in behaviour

Diagnosis

Diagnosis does not always require sampling, but your vet may need to check for the presence of tapeworm segments on the foxes coat and in their faeces. They may ask you to bring the animal and a stool sample along to the appointment. You may even need to provide more than one sample, as tapeworm segments are not shed every time an animal defecates. .

Treatment

Microscopy is required to identify the parasite and its treatment protocol accurately, but often, a broad spectrum anti-parasite medication, according to the manufacturers dosing schedule, will suffice. Whether the preventive you choose is given as a pill, a spot-on topical medication or as an injection, all approved parasite medications work by eliminating the immature (larval) stages of the parasite.

Treatment suggested for dogs:

Fenbendazole and praziquantel are approved for treatment of Taenia spp; epsiprantel, nitroscanate, and praziquantel are approved for D caninum; and praziquantel is approved for treatment of Echinococcus spp in the US and UK.

The animal's environment will need disinfecting and soft furnishings washed.

Prevention

For captive animals, control of intestinal worms is based on preventative anti-parasite treatment, improved sanitation and increased awareness.

It is easy for any animal to get intestinal worms, but regularly treating captive animals with an effective worming product, as directed by the product, gives you peace of mind knowing they are being kept parasite free.

For wild foxes, control of intestinal parasites is difficult, but there is a lot people can do to help them.

Practice good hygiene:

Do not use bowls where it can be prevented (use a scatter feed approach; chopping up food finely and scattering it across the garden).
Do not feed more than 70g (or 200 calories) of fox-suitable food, per fox, every 2-3 days (calculated to ensure it won't affect natural behaviour and impact negatively on health).
Do not feed processed foods, it contributes to poor health and reduces the animals ability to resist disease.
If using bowls, use as many as you have wildlife visitors. Try to avoid having many animals share the same bowl. Just as for ourselves and our pets, food hygiene is important.
Disinfect all utensils thoroughly every 24 hours. Ensure water bowls are included.
If using bowls or feeding stations, move them to different areas of the garden each night.
Keep grass and vegetation cut back and keep soil patches turned over regularly and powerhouse patios weekly.
Remove leaf litter and garden waste where parasites can hide.
Do not overfeed and allow rats or mice to take advantage. They breed quickly and can carry many different parasites.
Do not allow mold and fungus to grow on food or in the environment.
Foxes will cache excess food and will defecate on any caches they do not wish to return to (which will also not occur if you are feeding daily). Ensure that faces and unwanted food caches are disposed of and reduce the amount you are feeding if excess and waste is an issue.

Canid-safe, parasite-busting, immune-boosting plants:

Mugwort, Garden Cress, Wild Strawberry, Dandelion, Broadleaf Plantain, Milk Thistle, Fennel, Turmeric, Chicory, Chervil, Carrot, Celeriac, Pumpkin, Barley, Rye, Hibiscus, Blackberry, Rosehip, Blueberry, Mulberry, Gooseberry, Juniper, Elderberry, Coriander, Parsley, Rosemary, Thyme, Sage, Peppermint, Sweet Basil, Lemon Balm, Sunflower, Valerian and Dill.

Parasite-repelling plants:

Astrenia, Anise, Wormwood, Rue, Rosemary, Chamomile, Fleabane, Fleawort, Sweet Bay, Mint, Lavender, Garlic, Pennyroyal, Pyrethrum, Sage, Citronella, Marigolds, Scented Geraniums, Beebalm and Catmint.

Heartworm

Dirofilaria immitis (Dog Heartworm)
Angiostrongylus vasorum (French Heartworm)

Introduction and Background

Heartworm is a preventable but potentially fatal disease caused by a parasite transmitted by the bite of infected mosquitos. Mosquitoes carry the heartworm larvae (called microfilariae) from the blood meal of an infected animal host to a new animal host. Once the larvae arrive in a new host, they grow into adult worms in several months and live in the blood vessels that serve the heart and lungs. In advanced infections, the heartworms enter the heart as well.

The presence of parasites placing stresses on the foxes heart causes inflammation of the blood vessels and lungs. In addition, severe complications are possible when the number of worms present becomes high and when a large number of the heartworms die at once. Susceptible animals can be reinfected numerous times, so different stages of heartworm infections may be present in the same animal.

Clinical Signs

Heartworms are an invisible threat because they cause severe damage to the vessels of the animals lungs, typically long before any symptoms appear.

While treatment is available, heartworm disease causes lasting damage to the heart, lungs, and arteries, and can affect the animals health and quality of life, long after the parasites are gone. Common signs include:

Mild persistent cough
Lethargy and poor condition
Unexplained weight loss
Changes in behaviour
Vomiting and diarrhoea
Distended abdomen (due to fluid build up as a result of heart failure)
Breathing difficulty (more severe respiratory issues like rapid breathing and coughing).

Diagnosis

Heartworm disease is a serious, progressive disease transmitted by the bite of infected mosquitos. The earlier it is detected, the better the chances the animal will recover. There are few, if any, early signs of disease when an animal is infected with heartworms, so detecting their presence with a heartworm test administered by a veterinarian is important.

The test requires just a small blood sample from your pet, and it works by detecting the presence of heartworm proteins. If the fox tests positive, further tests may be ordered.

Treatment

Before treatment can begin, it is often necessary to restrict exercise and movement and to stabilize the animal's current condition. Once the animal is stabilized, a treatment protocol involving several steps may be required. Animals with no signs or mild signs of heartworm disease, such as cough or exercise intolerance, have a high success rate with treatment.

More severe disease can also be successfully treated, but the possibility of complications is greater. The severity of heartworm disease does not always correlate with the severity of symptoms, and an animal with many worms may have few or no symptoms early in the course of the disease.

Treatment suggested for dogs:

Adulticide treatment (insecticide used to kill heartworm) consists of initial treatment with doxycycline and macrocyclic lactones in advance of adulticide treatment. Different protocols are available, but a typical example is:

Day 1 – doxycycline 10mg/kg sid or bid for 30 days
Heartworm preventive (macrocyclic lactone) on day 0 and 15
Day 30 – melarsomine dihydrochloride 2.5mg/kg intramuscular (IM)
Day 60 and 61 – melarsomine dihydrochloride 2.5mg/kg IM

The patient should then be tested for microfilariae 30 days post treatment and antigen serology tested six months post treatment.

Prevention

For captive foxes, the correct anti parasite medication is required and a strict anti-parasite schedule must be followed. Whether the preventive you choose is given as a pill, a spot-on topical medication or as an injection, all approved heartworm medications work by eliminating the immature (larval) stages of the heartworm parasite. This includes the infective heartworm larvae, as well as the following larval stage that develops inside the animal.

Prevention programs using milbemycin, milbemycin/lufenuron, milbemycin/praziquantel, milbemycin/spinosad, moxidectin/imidacloprid, ivermectin/pyrantel, or ivermectin/pyrantel/praziquantel are suitable in the US and UK.

Unfortunately, within 51 days, immature heartworm larvae can molt into an adult stage, which cannot be effectively eliminated by preventives. Because heartworms must be eliminated before they reach this adult stage, it is extremely important that heartworm preventives be administered strictly on schedule (monthly for oral and topical products and every 6 months for the injectable). Administering prevention late can allow immature larvae to molt into the adult stage, which is poorly prevented.

For wild foxes, control of mosquitoes and midges can be difficult, but there is a lot people can do to help themselves and wildlife.

Practice good hygiene:

Dump all standing water on your property (in flowerpots, containers, buckets etc.)
Clean water bowls daily, do not allow biofilm and mold to build.
If you have a water feature, add a waterfall or fountain to keep the water moving or treat it with a natural bacteria called Bacillus thuringiensis, which kills mosquito larvae.
Remove all damp leaf litter from the garden.
Keep gutters clean and flowing.
Keep grass and vegetation cut back.
Do not use bowls where it can be prevented (use a scatter feed approach; chopping up food finely and scattering it across the garden).
Do not feed more than 70g (or 200 calories) of fox-suitable food, per fox, every 2-3 days (calculated to ensure it won't affect natural behaviour and impact negatively on health).
Do not feed processed foods, it contributes to poor health and reduces the animals ability to resist disease.
If using bowls or feeding stations, move them to different areas of the garden each night. Use as many bowls as you have wildlife visitors, try to avoid having many animals share the same bowl.

Canid-safe, parasite-busting, immune-boosting plants:

Mugwort, Garden Cress, Wild Strawberry, Dandelion, Broadleaf Plantain, Milk Thistle, Fennel, Turmeric, Chicory, Chervil, Carrot, Celeriac, Pumpkin, Barley, Rye, Hibiscus, Blackberry, Rosehip, Blueberry, Mulberry, Gooseberry, Juniper, Elderberry, Coriander, Parsley, Rosemary, Thyme, Sage, Peppermint, Sweet Basil, Lemon Balm, Sunflower, Valerian and Dill.

Parasite-repelling plants:

Astrenia, Anise, Wormwood, Rue, Rosemary, Chamomile, Fleabane, Fleawort, Sweet Bay, Mint, Lavender, Garlic, Pennyroyal, Pyrethrum, Sage, Citronella, Marigolds, Scented Geraniums, Beebalm and Catmint.

Lungworm

Aelurostrongylus abstrusus (Feline Lungworm)
Crenosoma vulpis (Fox Lungworm)
Oslerus osleri (Dog Lungworm)

Introduction and Background

Lungworm is an infection caused by the roundworm parasites listed above. Slugs, snails and frogs carry the lungworm larvae and spread it through their slime trails. Foxes generally become infected when they consume the parasite from the environment. Unlike many diseases, lungworm cannot be passed through contact.

Lungworm live in nodules in the trachea of infected animals, and larval eggs laid by adults hatch there. Foxes become infected from contact with the faeces or saliva of an infected animal (for example, when hunting).

Clinical Signs

Signs of lungworm infection range from moderate to severe:

Dry coughing and/or persistent coughing
Increased respiratory rates and/or respiratory distress
Abnormal blood clotting or bloody urine
Lethargy and poor condition
Unexplained weight loss
Changes in behaviour
Vomiting or diarrhoea

Diagnosis

Diagnosis of lungworm infection is based on signs, known transmission patterns, and presence of larvae in faeces. It can be a challenge for the veterinarian to diagnose lungworm because infected animals do not always pass the larvae in their faeces, and when they do, they may be few in number.

Examination of the airways with an endoscope (bronchoscopy) and x-rays can be helpful. Bronchoscopy can be used to collect washings from the trachea ('tracheal washing') to examine for eggs, larvae, and white blood cells.

Treatment

Lungworm infection in foxes can be difficult to treat, but there is evidence that appropriate antiparasitic drugs are effective, particularly when combined with surgical removal of the nodules in the trachea. It may be necessary to continue antiparasitic treatment for up to 2 months.

The ESCCAP guidelines for dogs, advise the use of a macrocyclic lactone-based anthelmintic or daily administration of a benzimidazole-based anthelmintic for 3 weeks. The guide adds that supportive treatment, with antibiotic and glucocorticoids as well as blood substitute fluids, may be needed in severe clinical cases, and the animal should be rested during the treatment period (at least 2–3 days).

Fenbendazole is a commonly used off-label treatment for lungworm, although it is not licensed for this use. However milbemycin oxime and moxidectin and reported clinical experience supports the use of moxidectin as first-line treatment in animals with mild to moderate disease, or in suspected cases. There is no clear evidence regarding treatment to be used in more severe cases and clinicians may have to approach these on a case-by-case basis.

Prevention

For captive foxes, the correct anti parasite medication is required and a strict anti-parasite schedule must be followed. Whether the preventive you choose is given as a pill, a spot-on topical medication or as an injection, all approved lungworm medications work by eliminating the immature (larval) stages of the lungworm parasite. This includes the infective lungworm larvae, as well as the following larval stage that develops inside the animal.

Because lungworms must be eliminated before they reach this adult stage, it is extremely important that lungworm preventives be administered strictly on schedule (monthly for oral and topical products and every 6 months for the injectable). Administering prevention late can allow immature larvae to molt into the adult stage.

For wild foxes: Control of slugs, snails and frogs can be difficult, but there is a lot people can do to help themselves and wildlife.

Practice good hygiene:

Dump all standing water on your property (in flowerpots, containers, buckets etc.)
Disinfect all utensils thoroughly every 24 hours. Ensure water bowls are included. Do not allow biofilm and mold to build up.
Do not use bowls where it can be prevented (use a scatter feed approach; chopping up food finely and scattering it across the garden) and running water features.
Do not feed more than 70g (or 200 calories) of fox-suitable food, per fox, every 2-3 days (calculated to ensure it won't affect natural behaviour and impact negatively on health).
Do not feed processed foods, it contributes to poor health and reduces the animals ability to resist disease.
If using bowls, use as many as you have wildlife visitors. Try to avoid having many animals share the same bowl. Just as for ourselves and our pets, food hygiene is important.
A natural bacteria called Bacillus thuringiensis, sold as a ‘soil drench', kills parasites and can be used to treat the soil.
If using bowls or feeding stations, move them to different areas of the garden each night.
Keep grass and vegetation cut back and keep soil patches turned over regularly and powerhouse patios weekly.
Remove leaf litter, bricks, logs and garden waste where slugs, snails and frogs can hide.
Do not overfeed and allow slugs and snails to take advantage.
Copper tape can also be used to help deter slugs and snails, reacting with their biofilm slime to give them a shock.

Canid-safe, parasite-busting, immune-boosting plants:

Mugwort, Garden Cress, Wild Strawberry, Dandelion, Broadleaf Plantain, Milk Thistle, Fennel, Turmeric, Chicory, Chervil, Carrot, Celeriac, Pumpkin, Barley, Rye, Hibiscus, Blackberry, Rosehip, Blueberry, Mulberry, Gooseberry, Juniper, Elderberry, Coriander, Parsley, Rosemary, Thyme, Sage, Peppermint, Sweet Basil, Lemon Balm, Sunflower, Valerian and Dill.

Parasite-repelling plants:

Astrenia, Anise, Wormwood, Rue, Rosemary, Chamomile, Fleabane, Fleawort, Sweet Bay, Mint, Lavender, Garlic, Pennyroyal, Pyrethrum, Sage, Citronella, Marigolds, Scented Geraniums, Beebalm and Catmint.

Roundworm

Toxocara canis (Dog Roundworm)
Toxocara cati (Cat Roundworm)
Toxascaris leonina (Common Roundworm)
Strongyloides spp. (Threadworm)
Trichinella spiralis (e.g Pork Roundworm)

Introduction and Background

Roundworms are commonly referred to as ascarids and are the most common parasites found in pets and wildlife, being transmitted by infected faeces, soil and bodily fluids. Roundworms live an average of 4 months and have a life cycle ranging from as early as 14 days to as long as 80 days depending on the species.

The geographic distribution of Toxocara spp. is widespread in the pet population around the United Kingdom and many pets younger than 6 months of age naturally shed toxocara eggs. Hence our persistence with regular worming schedules for young animals and adults.

Clinical Signs

Although it is possible for a fox to have roundworms and not show any symptoms, there are certain signs that can accompany a case of roundworms:

Distended abdomen
Weakness and lethargy
Diarrhoea (worms may be visible)
Vomiting (worms may be visible)
Abdominal pain or shielding
Dull coat and poor condition
Unexplained weight loss
Behavioural changes

Diagnosis

Your vet will diagnose infection by detection of eggs in feces by microscopy. Distinguishing the spherical, pitted-shelled eggs of Toxocara spp from the oval, smooth-shelled eggs of Toxascaris leonina is important because of the public health significance of the former.

Treatment

Compounds approved for treatment of roundworm infections include fenbendazole, milbemycin, moxidectin, piperazine, and pyrantel in the US and the UK.

In dogs, the suggested dosage is:

Daily doses of fenbendazole (25 mg/kg, PO) from day 40 of gestation to day 2 after birth (approved in the UK),
Ivermectin (0.3 mg/kg, SC) on days 0, 30, and 60 of gestation, and 10 days after birth,
Ivermectin (0.5 mg/kg) on days 38, 41, 44, and 47 of gestation, or
Ivermectin (1 mg/kg) on days 20 and 42 of gestation; these uses of ivermectin are extra-label.

Otherwise, to minimize egg output, young should be treated as early as possible; ideally, treatment should be given 2 weeks after birth and repeated at 2-week intervals to 2 months of age, and then monthly to 6 months of age. Nursing females should be treated at the same time as the young. In other animals, the appropriate frequency of preventive treatment for roundworms should be based on a risk assessment of the animal's environment.

The animal's environment will need disinfecting and soft furnishings washing and because the eggs adhere to many surfaces and become mixed in soil and dust, strict hygiene should be observed by people, particularly children, exposed to potentially contaminated animals or areas.

Roundworm eggs can be found in large numbers, are very hardy and may live for years in the environment. Extreme measures such as paving an area, complete removal of topsoil, controlled burns of the contaminated areas, or treating with steam have shown to effectively remove or destroy roundworm eggs in the environment.

Prevention

For captive animals, control of intestinal worms is based on preventative anti-parasite treatment, improved sanitation and increased awareness.

It is easy for any animal to get intestinal worms, but regularly treating captive animals with an effective worming product, as directed by the product, gives you peace of mind knowing they are being kept parasite free.

Protecting the environment by promptly removing faeces, preventing scavenging tendencies, and administering monthly deworming (in the case of captive foxes), are all ways in which to control and prevent roundworm infections.

Cleaning the environment of stools to prevent eggs from becoming infective is crucial.

For wild foxes, control of intestinal parasites is difficult, but there is a lot people can do to help them.

Practice good hygiene:

Do not use bowls where it can be prevented (use a scatter feed approach; chopping up food finely and scattering it across the garden).
Do not feed more than 70g (or 200 calories) of fox-suitable food, per fox, every 2-3 days (calculated to ensure it won't affect natural behaviour and impact negatively on health).
Do not feed processed foods, it contributes to poor health and reduces the animals ability to resist disease.
If using bowls, use as many as you have wildlife visitors. Try to avoid having many animals share the same bowl. Just as for ourselves and our pets, food hygiene is important.
A natural bacteria called Bacillus thuringiensis, sold as a ‘soil drench', kills the roundworm parasite and can be used to treat the soil.
Disinfect all utensils thoroughly every 24 hours. Ensure water bowls are included.
If using bowls or feeding stations, move them to different areas of the garden each night.
Keep grass and vegetation cut back and keep soil patches turned over regularly and powerhouse patios weekly.
Remove leaf litter and garden waste where parasites can hide.
Do not overfeed and allow rats or mice to take advantage. They breed quickly and can carry many different parasites.
Do not allow mold and fungus to grow on food or in the environment.
Foxes will cache excess food and will defecate on any caches they do not wish to return to (which will also not occur if you are feeding daily). Ensure that faces and unwanted food caches are disposed of and reduce the amount you are feeding if excess and waste is an issue.

Canid-safe, parasite-busting, immune-boosting plants:

Mugwort, Garden Cress, Wild Strawberry, Dandelion, Broadleaf Plantain, Milk Thistle, Fennel, Turmeric, Chicory, Chervil, Carrot, Celeriac, Pumpkin, Barley, Rye, Hibiscus, Blackberry, Rosehip, Blueberry, Mulberry, Gooseberry, Juniper, Elderberry, Coriander, Parsley, Rosemary, Thyme, Sage, Peppermint, Sweet Basil, Lemon Balm, Sunflower, Valerian and Dill.

Parasite-repelling plants:

Astrenia, Anise, Wormwood, Rue, Rosemary, Chamomile, Fleabane, Fleawort, Sweet Bay, Mint, Lavender, Garlic, Pennyroyal, Pyrethrum, Sage, Citronella, Marigolds, Scented Geraniums, Beebalm and Catmint.