Threadworms are present in the United Kingdom and also in the United States of America. This type of worm is able to affect dogs, cats, horses, rats and pigs. They are intestinal parasites and each subtype can infect different species than other subtypes. A threadworm infection in the animal can sometimes lead to death in young puppies.
Strongyloides in Dogs
Dogs are infected by the species of threadworm called the Strongyloides stercoralis, although it is also able to infect cats. This parasite is extremely thin and, as is implied by the name, has a thread like appearance. It is inside the intestine of the dog that the threadworm resides and reproduces. Once the eggs have hatched, the dog defecates and passes out the larvae in its faecal matter.
The animals more susceptible to contracting this internal parasite are dogs living in unhygienic areas and in overcrowded areas. Transmission can occur once the larvae have burrowed through the skin of an animal, such as the dog, that it comes into contact with. They are able to rapidly multiply irrespective of the presence of the animal thus increasing the chance of it being transmitted.
Some infected dogs may not show any signs or symptoms. However, others may be severely affected showing signs of diarrhoea or problems within the respiratory tract. Humans can become infected by this parasite and so it is known as zoonotic. Infected humans show signs of dermatitis.
Transmission of Threadworms
Threadworms are transmitted from the environment to the animal when the parasitic larvae burrow into the skin of the host and infect the tissues, usually those of the small intestine. Once inside the dog, threadworms rapidly reproduce in the small intestine. Puppies may become infected by the disease if suckling from an affected mother. This generally occurs if the larvae have travelled to the mammary glands. The threadworms can remain in an animal’s tissues longer even than a year.
The threadworms S. Stercoralis have the ability to multiply whether or not in the presence of its host. This increases the risk for dogs to come into contact with and thus become infected with the worm. The parasites are best suited to hot and humid environments. Larvae can be found in faecal and other decaying matter.
Signs and Symptoms of Threadworms
The majority of dogs are asymptomatic during an infection of the threadworm. This means that they show no signs or symptoms. In other cases, there may be signs of dermatitis in areas where the larvae burrow through the skin. Either mild or severe diarrhoea may be observed, the severity generally increasing the younger the puppy. The dog could be weak or dehydrated. A loss in appetite and weight may also be a result of a threadworm infection.
Re-infection sometimes happens if the larvae travel to the lungs and are coughed up, later to be swallowed back into the gut. Therefore, coughing may also be another sign. Bronchopneumonia can affect threadworm infected dogs.
Treatment of Threadworms
There are available treatments to deal with a threadworm infection although they have limited success since the larvae of the parasite live inside the tissues. It is therefore difficult for the medication to gain access to these tissues. These medications often include the use of Fenbendazole and Ivermectin which are given orally. In the most severe cases, fluids are administered to replace those lost as well as electrolytes to treat any imbalance of these important substances.
Prevention from S. Stercoralis Infection
As is the fundamental rule of medicine: “Prevention is better than cure”. Clearly, it is in the best interests of both dog and owner for preventative measures to be put into place. High levels of hygiene are a necessity as well as regular worming.
Due to the fact that the parasite thrives in hot and humid areas, it is essential to maintain a basic cleaning routine which ensures a dry environment for the dog which also has good levels of hygiene. All faecal matter should be immediately removed to prevent the spread of threadworm. In parks and other areas where dogs come into contact with, the dog should be discouraged from going any where near to faeces.
Animals diagnosed with threadworm should be treated as soon as possible and isolated for a short period of time to prevent the larvae migrating and infecting other animals. Previously infected animals should be regularly tested to ensure no re-infection has occurred. All areas within the home and garden should be cleaned which have come into contact with the infected animal.
Diagnosis of a Threadworm Infection
There are various methods of diagnosis where threadworms are concerned. These include routine baseline tests, a direct faecal exam and a test known as the Baermann technique. In cases of dermatitis, a skin scraping may be acquired to detect the presence of the parasite following the use of a microscope.
The routine baseline tests are usually the only test required to provide a positive diagnosis. These simply test the blood for a full blood count and a biochemical profile is acquired. Urine samples are also taken to test for a thread worm infection.
A fresh faecal sample is also sometimes required to detect and identify the presence of threadworms in a dog. In effect, this method uses a microscope to find the eggs and larvae of S. Stercoralis in the dog’s faeces. The dog suspected of an infection has its faeces smeared on a microscope slide with a special solution for a positive diagnosis.
A more reliable method is the Baermann technique. This provides an easier method of spotting the tiny larvae which may be difficult to see in the already mentioned methods. A sample of the infected animal’s faeces is taken, wrapped in cloth and is then placed in warm water. Here there is a funnel with a rubber tube clamped off at its bottom to reduce any water escaping. The rubber tubing leads to a conical flask, or a collecting jar. The larvae that may be present will migrate naturally travel out of the cloth and into the warm water where they sink to the bottom of the collection of water. Once the clamp is opened a single drop of water is collected. This drop should then contain a high concentration of the larvae which can then be examined microscopically.
Prognosis of Threadworm Infections
Several infected puppies may die following infection and if they are left untreated. In older dogs it is rare for the disease to cause any major adverse health problems. Treatment is not always completely successful since the larvae can migrate deep into the tissues of the dog.