Parasites

Parasites are defined as an organism which feeds off of a host animal who gains no benefit from the parasite.

Parasites can be classed as either ectoparasites (living on the outside of the host) or endoparasites (living off a host internally)

Extoparasites

Flea - Flea infestations cause a significant effect on their hosts and can carry viral and bacterial diseases including Bartonella as well as tapeworms . The small jumping insect bites through the animal’s skin to reach the blood causing irritation to the skin. Over time, exposure to fleas can lead to flea-bite allergy in some animals due to increased hypersensitivity to flea saliva. Dogs with severe infestations may suffer from anaemia.

·         Symptoms:   Scratching

Biting/chewing

Black grit in the coat (flea droppings)

Fleas (approximately 2mm in size and rapid moving)

 

Fleas are highly contagious and breed rapidly and profusely. Fleas don’t need to be on the animal to breed therfore it is vital to ensure the environment and the affected animal are both treated. This is especially important as the fleas can live for up to 6 months without feeding.

 

Tick – There are various types of tick, however dogs are most commonly affected by the sheep tick. As ticks inject an anesthetic when they bite ticks do not generally cause irritation to the host. The tick bites through the skin and stays attached until full of blood, at which point it drops off into the environment. Ticks are carriers of Lyme disease which can cause flu like symptoms in both people and dogs.

Removal of ticks should be done carefully, to ensure the head does not remain embedded in the host. Failure to remove the whole tick may result in infection developing. It is recommended that ticks are removed using a specialist tool which gets under the head part of the parasite.

 

Lice – There are two main types of lice which commonly affect dogs: sucking and biting lice. Sucking lice do bite through the skin to feed on tissue fluid where as biting lice chew on loose flakes of skin. Both types of louse are commonly found around orifices and under matted hair. Lice are often referred to as “nits”, however it is actually the eggs which are regarded as the nit. While highly contagious, lice are different from fleas in that they can only survive for a few days without a host.

·         Symptoms:  scratching / skin irritation anaemia

lice (approximately 4mm in size)

 

Mites – There are various types of mites, which can be classified according to if they are burrowing or surface mites. Mites are significantly smaller than other ectoparasites and are only just visible to the naked eye.

 

 

Endoparasites

 

Roundworms - Toxocara canis is the roundworm which affects dogs and is zoonotic. It is common for adult, healthy animals to carry a small worm load with no adverse effects, however as a result the majority of puppies are born infected with worms. It is for this reason that early worming is recommended. Roundworms do not attach themselves to the host, rather they move around the animal’s intestine feeding of the nutrients ingested by the host animal.

 

 

 

Roundworms are thin, white ‘spaghetti-like’ worms that can reach up to 7-12cm in length.

 

Eggs can survive on the ground for two years or more and are resistant to boiling, freezing and disinfectants.

 

 

 

Dogs with a round worm infestation are often asymptomatic however is severe cases  the following symptoms can be seen.

 

 

 

• Symptoms:         Dull hair / coat

 

Pot-bellied appearance

 

Poor weight gain

 

Intermittent diarrhea or constipation

 

Worms can be visible in faeces

 

 

 

Tapeworms – One of the most common types of tape worm is Dipylidium caninum. This zoonotic parasite is usually ingested when an animal comes into contact with and ingests an already infected intermediate host. Fleas can also act as intermediate hosts for tapeworm, the flea settles on the host, the host cleans themselves by licking and ingests the flea and subsequent tapeworm.

 

 

 

• Symptoms:          Dull hair / coat

 

Visible worm segments in faeces or fur.

 

 

 

Tapeworms appear as a creamy, flattened, segmented ‘ribbon’ and can grow to 50-75cm in length. The head of the tapeworm is called the scolex and has hooks which grasp onto the wall of the small intestine of the dog.

 

 

 

Heartworms – Heartworms are not found in Britain, however they are a serious problem for the host and can result in death. The worm larvae are carried by mosquitos. It can take up to 4 months for the heartworms to mature and migrate through the blood stream into the heart where they cause significant damage.

 

 

 

• Symptoms:           Generally no symptoms during incubation

 

High blood pressure

 

Heart failure

 

Breathing difficulties.

 

 

 

Heartworms are almost thread like in appearance and can reach up to 30cm in length.

 

 

 

Hookworms – Hookworms are commonly seen in kenneled dogs. Once the host has become infected the worms use their cutting plates to hook onto the animal’s intestines, attaching to different areas and leaving ulcers at attachment sites. Unlike most other worms, hookworms are able to migrate through the animal’s skin into the blood stream.

 

 

 

• Symptoms:           Poor weight gain

 

Intermittent diarrhea or constipation

 

Skin irritation (often between toes) caused by migrating larvae

 

 

 

Hookworms are small, thin worms, approximately 1cm long with hook like plates and teeth.

 

 

 

Whipworm – Like tapeworm, whipworms generally go unnoticed and cause little harm to the host unless the host has a weakened immune system or a particularly heavy worm load. Once inside the host they migrate to the intestine where they embed themselves and feed on the hosts blood. 

 

 

 

• Symptoms:           Diarrhoea

 

Anemia

 

Reduced growth in young dogs.

 

 

 

Whipworms are tapered in appearance, with a thick head and a whip like tail.

 

 

 

Lungworm – Lungworm is relatively new in Britain and therefore uncommon in dogs, but is serious when it does occur due to the fact that is migrates to the lungs. Lungworm is also known as French heartworm.  Dogs generally become infected by eating infected slugs and snails.

 

 

 

• Symptoms:           Lethargy / depression

 

Coughing / difficulty breathing

 

Poor blood clotting

 

 

 

Lungworms are long, thin worms, reaching 2.5cm.

 

 

 

Threadworm – Threadworms are also known as pinworms. They are zoonotic and can be spread by the saliva of ticks or coming into contact with infected faeces. Like tapeworm and whipworms, threadworms generally asymptomatic and cause little harm to the host unless the host has a weakened immune system or a particularly heavy worm load.

 

 

 

• Symptoms:     Diarrhoea

                         Abdominal discomfort

                           Dehydration

 

 

 

Threadworms look like small white pieces of thread, approximately 1cm long and can be seen around the animal’s anus.