Giardiasis can be found in several areas all over the world, including the United States although infections are argued to be a rare occurrence. The Giardia parasite can infect many animals including cats, and this particular parasite (Giardia canis) can be found in dogs of all ages. If the disease is allowed to enter its advanced stage, fatalities can occur, generally as a result of poor absorption in the infected animal’s gut, although treated animals do tend to recover from giardiasis. 

Giardia Canis

A protozoan infection, the disease called Giardiasis is caused by a parasite which resides inside the body and, in dogs, is known as Giardia canis. The parasite is made up of only one cell and so is called a single celled organism. The Giardia parasite, upon entering the animal, resides in the small intestines of the infected dog and release trophozites which replicate. The parasite’s oocysts are then found in the affected dogs faeces.

Dogs which are more susceptible to this parasite and its infection of the disease are young dogs and puppies. This is because they will not have yet acquired strong enough immunity when compared with their older counterparts. Transmission of giardiasis can occur when an unaffected animal ingests the faeces, contaminated with oocysts, belonging to an infected dog.

The signs and symptoms following a parasitical infection of Giardia canis are best known to be the production of yellowy diarrhoea which emits an abnormally unpleasant odour. Mal-absorption leads to this problem as well as severe dehydration. Whether this disease is zoonotic, in other words transferrable to humans, or not is not yet known.

Transmission of Giardiasis

Giardiasis is transmitted as a result of the parasite giardia. Ingestion of contaminated faeces containing this parasite’s oocysts results in the transmission of the disease in unaffected dogs. The oocysts are ingested and the result is a release of a couple of trophozoites from each oocyst.

Ingestion can occur via active feeding of infected faeces or even simply licking these contaminated materials. Contaminated water and food are also sources of infection, as well as the bowls they are kept in. One factor increasing the spread of this disease is the fact that many infected dogs may become asymptomatic. This means that they show known signs of infection and so owners are less likely to be aware that they need to be treated. Therefore, the dog is able to infect many other dogs without the knowledge of owners.

The oocysts are able to survive outside the host for as long as a few months, even in cold weather, and are immediately infectious. They are also resistant to wet conditions.

Signs and Symptoms of Giardiasis

Dogs infected with the parasite giardia can show varying signs of infection although it is common for no signs or symptoms to be presented at all. The medical term for this is asymptomatic.

Young puppies are more severely affected following the contraction of the disease. Generally, different degrees of greasy diarrhoea are observed in puppies with giardiasis due to a mal-absorption of nutrients in the intestines. Soft, pale yellow faeces are passed and an unpleasant smell will be noticed. A loss in weight can therefore result as well as lethargy. If severe dehydration is an occurrence as a result of this, the infection becomes very dangerous for the dog’s health.

Treatment for a Giardiasis Infection in Dogs 

The treatments used to restore an infected dog back to full health include medication which attempts at the removal of the parasites, the elimination of any secondary bacterial infections and provide relief for particular symptoms. However, treatment programmes vary and there is no set plan to deal with this parasitical disease.

The main medication administered for the removal of worms is known as fenbendazole. A positive diagnosis must be acquired before any treatment should start. Antibiotics are given to prevent or treat any possible secondary bacterial infections which can result following the contraction of the parasite. High levels f hygiene must be maintained at all times. If severely dehydrated, fluids are often given to replace those lost.

Metronindazole is sometimes given in conjunction with fenbendazole although complete efficacy, despite the use of both drugs, is not a certainty when dealing with giardiasis. It has been suggested that despite apparently successful treatment, where the faecal matter becomes free of oocysts, the parasites may still survive within the intestines of the dog. Thus, they would be acting as carriers.

Prevention of Canine Giardia Infection

Due to the lack of knowledge or licensed drugs concerning the treatment of canine giardiasis, preventative measures are vital to prevent the spread of the disease.  These measures include maintaining high levels of hygiene, taking care when introducing new dogs to households, and generally reducing exposure to sources of infection.

Hygiene levels can be kept high by regularly disinfecting areas such as kennels, water and food bowls. Certain bleaches and products containing ammonium compounds are generally seen as effective measures when cleaning contaminated surfaces. It is important the animal does not ingest these products. Steam cleaning surfaces can also work towards the elimination of the parasite.

Removal of faeces in the garden, park or other such areas is another good method of prevention. Infected animals should be treated in the hope that they will not longer pass the oocysts in their faeces, thus disallowing them from infecting other animals. Owners should not allow their dogs from sniffing, licking, eating or ideally going near the faecal matter belonging to other animals. Dogs should also be washed using warm water and canine-friendly shampoo. 

New dogs should be isolated for a short period of time, usually a few days, and observed for any unusual signs or symptoms. This is to prevent the disease rapidly infecting other dogs which may have otherwise come into contact with the possibly infected animal. This is especially important in properties with a high density of dogs, such as kennels. Dogs shown to be infected should be regularly tested for the presentation of oocysts in their faeces.

Diagnosis of Canine Giardiasis

Initially animals are diagnosed by observing and noting the signs and symptoms presented. The medical history of the area and of the animal can also be used for initial diagnostic purposes. However, a complete diagnosis is required. This consists of taking samples of the suspected animal’s faecal matter. These are tested using the ELISA test in order to detect the presence of the parasite’s oocysts. 

Prognosis for Dogs with Giardiasis

Animals treated efficiently can have a good prognosis but many treatments can sometimes be unsuccessful, albeit simply relieve the symptoms, it is difficult to give an accurate generalised prognosis. This only becomes really poor if the disease progresses so that severe dehydration results from the diarrhoea caused by the parasite.


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