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Strongyloidiasis (Intestinal Infection Caused by Threadworms, Strongyloides) in Dogs

Occurrence: common
Location of illness: Abdomen/pelvis

Author: Dr. med. vet. Gisa Löwe | Last modified: 06.11.2025

Strongyloidiasis is a parasiticParasitic refers to diseases or conditions caused by parasites. Parasitic infections can affect the digestive tract, skin, and other organ systems. infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. in dogs caused by the threadworm Strongyloides stercoralis. This infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. mainly affects the intestineThe intestine is the medical term for the gut, including the small intestine (intestinum tenue) and the large intestine (intestinum crassum). It plays a central role in the digestion and absorption of nutrients. and can lead to a variety of gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. symptoms.

The most important facts at a glance

Strongyloidiasis in dogs is caused by the microscopic threadworm Strongyloides stercoralis and occurs mainly in tropical and subtropical regions. The infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. is commonly observed in dogs living in crowded or unhygienic environments. The parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans. enters the body through the skin or mucous membranes and develops further in the intestineThe intestine is the medical term for the gut, including the small intestine (intestinum tenue) and the large intestine (intestinum crassum). It plays a central role in the digestion and absorption of nutrients.. Symptoms include Cough, DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., skin rashes, and Weight loss. DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is made by microscopic examination of the stool to detect larvae, and in some cases by serological tests. Treatment includes antiparasiticsAntiparasitics are medications or substances used to treat parasitic infestations, such as worms, protozoa, and ectoparasites. They work by killing the parasites or inhibiting their growth. such as Ivermectin and Fenbendazole, as well as measures to improve the dog’s living conditions to prevent re-infection. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. is generally good if the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. is detected and treated early. Preventive measures include maintaining a clean environment, regular veterinary check-ups, and avoiding contact with contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. materials. Research focuses on improving diagnostic procedures, developing new treatment strategies, and understanding the epidemiological spread of the disease. It is also being investigated to what extent dogs could serve as reservoir hosts for transmission to humans. These research approaches aim to improve the health of dogs and minimize the risk to humans.

Causes

Strongyloides stercoralis is a microscopic threadworm that occurs worldwide, especially in tropical and subtropical regions. The parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans. can develop both in the soil and in the body of its host, in this case the dog. Reproduction is asexual, which allows for rapid spread of the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease..

The infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. often occurs in dogs living in crowded or unhygienic environments, such as animal shelters or kennels. The larvae of the parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans. enter the body through the skin or mucous membranes and then migrate to the intestineThe intestine is the medical term for the gut, including the small intestine (intestinum tenue) and the large intestine (intestinum crassum). It plays a central role in the digestion and absorption of nutrients., where they develop and multiply.

Causes of the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. are often direct contact with contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. soil or water, as well as contact with infected animals. In addition, transmission can occur through ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. of larvae through the skin or through the consumption of contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. materials. In some cases, transmission from the mother dog to the puppies can also occur via the mother’s milk.

Symptoms

Very common symptoms:

Common symptoms:

Rare symptoms:

The symptoms of strongyloidiasis in dogs can vary, depending on the severity of the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. In mild cases, dogs may remain asymptomaticAsymptomatic means that there are no recognizable symptoms of a disease. An animal can have a disease or infection without showing visible signs, which can make diagnosis and treatment more difficult., while severe infections can lead to a variety of gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. complaints.

The most common symptoms include DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., which is often watery or mucous, as well as Vomiting. Affected dogs may also show a loss of appetite, leading to Weight loss. In some cases, AbdominalThe term “abdominal” refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. pain and Flatulence may occur.

In severe infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease., systemic disease may occur, characterized by symptoms such as Fever, lethargy, and dehydrationDehydration occurs when the body loses more fluid than it takes in. This can lead to a number of problems, including headaches, Dizziness, and in extreme cases, renal failure or Cardiovascular collapse.. Young dogs and those with a weakened immune systemThe immune system is the body’s defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. are particularly at risk, as the parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans. can cause severe health problems in these cases.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of strongyloidiasis is usually made by microscopic examination of the dog’s stool to detect larvae or eggs of the parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans.. MultipleMultiple means manifold or repeated and is used to describe conditions or events that occur in multiple instances or at different locations. In veterinary medicine, this may indicate multiple lesions, tumors, or other pathological changes. stool samples may be required because the excretion of larvae is not constant.

In some cases, a serological test can also be performed to detect antibodies against the parasite in the dog’s blood. These tests can help confirm an infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease., especially if no larvae are found in the stool.

In addition to laboratory diagnostic procedures, the veterinarian can also perform a thorough clinical examination to rule out other possible causes for the symptoms. A historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits. of the dog, including information about its living conditions and contacts with other animals, is also helpful for the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients..

Therapy

Treatment of strongyloidiasis in dogs is usually done with antiparasiticsAntiparasitics are medications or substances used to treat parasitic infestations, such as worms, protozoa, and ectoparasites. They work by killing the parasites or inhibiting their growth. that are specifically effective against threadworms. Ivermectin and fenbendazole are commonly used medications that are usually administered for several days to kill all stages of the parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans..

In addition to drug treatment, it is important to improve the dog’s living environment to prevent re-infection. This may include regular cleaning and disinfection of the dog’s living area, as well as avoiding contact with potentially contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. materials.

In severe cases, especially in dogs with systemic symptoms, supportive treatment may be necessary. This includes the administration of fluids to treat dehydrationDehydration occurs when the body loses more fluid than it takes in. This can lead to a number of problems, including headaches, Dizziness, and in extreme cases, renal failure or Cardiovascular collapse. and, if necessary, the administration of medications to control Vomiting and DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems..

Prognosis and follow-up care

The prognosis for dogs with strongyloidiasis is generally good, especially if the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. is detected and treated early. Most dogs recover completely after appropriate antiparasitic therapy.

In more severe infections or in dogs with a weakened immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body., recovery may take longer and there is a higher risk of complications. In such cases, close monitoring by the veterinarian is necessary to ensure the success of the treatment.

An untreated infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. can lead to chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. health problems and, in rare cases, can even be life-threatening, especially in young puppies or severely immunocompromised dogs.

Prevention

The preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. of strongyloidiasis includes several measures to minimize the risk of infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. One of the most important measures is to maintain a clean and hygienic environment for the dog. Regular cleaning and disinfection of kennels, sleeping areas, and feeding areas can prevent the spread of the parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans..

It is also important to avoid contact with potentially contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. soils or water sources, especially in areas where strongyloidiasis is common. Dogs should not be left outside unattended to reduce the risk of infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease..

Regular veterinary check-ups and stool examinations can help detect and treat an infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. early before it develops into a serious health problem. In addition, the veterinarian may recommend preventive antiparasitic treatments, especially in high-risk areas or in dogs housed in communal facilities.

By combining these preventive measures with appropriate medical care, the risk of strongyloidiasis infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. in dogs can be significantly reduced.

Outlook on current research

Research on strongyloidiasis in dogs is currently focused on several key areas, including improving diagnostic procedures, developing more effective treatment strategies, and understanding the epidemiological spread of this parasiticParasitic refers to diseases or conditions caused by parasites. Parasitic infections can affect the digestive tract, skin, and other organ systems. infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. A significant advance in diagnostics is the refinement of molecular techniques that allow the threadworm (Strongyloides stercoralis) to be identified in dog stool samples with greater precision. These techniques, such as polymerase chain reaction (PCR), are significantly more sensitive than conventional microscopic methods and can provide reliable results even at low parasite densities.

Another significant area of research is the development of new antiparasiticsAntiparasitics are medications or substances used to treat parasitic infestations, such as worms, protozoa, and ectoparasites. They work by killing the parasites or inhibiting their growth. and treatment protocols to prevent resistanceResistance refers to the ability of microorganisms to withstand the effects of antibiotics, antifungals, or other antimicrobial drugs. Resistance can also refer to the body's ability to be insensitive to diseases or toxins. and increase treatment effectiveness. Scientists are investigating the effectiveness of various agents and their combinations to achieve the best treatment outcomes. In addition, there are studies on the possibility of vaccineA vaccine is a substance that stimulates the immune system to develop immunity against specific pathogens without causing the disease itself. Vaccines may contain weakened or inactivated pathogens, toxoids, or recombinant antigens. development to establish preventive measures against this infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. The challenge here is to better understand the complex immune responseAn immune response is the immune system's reaction to foreign substances (antigens), such as microorganisms or proteins. It involves a series of processes aimed at recognizing, fighting, and eliminating these antigens. of the host to the parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans..

Epidemiological research aims to map the occurrence and spread of strongyloidiasis in dogs in different regions of the world. It is believed that climate change and the increasing mobility of pets may contribute to the spread of this infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. Therefore, studies that address the ecological and social factors that contribute to the transmission of Strongyloides are crucial to better predict and control future outbreaks.

In addition, research is addressing the role of dogs as potential reservoir hosts for the transmission of Strongyloides to humans, particularly in regions with close cohabitation of humans and animals. These interdisciplinary studies are crucial to deepen the understanding of the zoonotic aspects of strongyloidiasis and to develop appropriate preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. measures.

Overall, current research aims to improve the health and well-being of dogs by minimizing the impact of strongyloidiasis, while also reducing the potential risks to humans. By combining advances in diagnostics, therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions., and epidemiology, scientists hope to significantly improve control over this parasiticParasitic refers to diseases or conditions caused by parasites. Parasitic infections can affect the digestive tract, skin, and other organ systems. disease.

Frequently asked questions (FAQs)

What is strongyloidiasis in dogs? Strongyloidiasis in dogs is an intestinalIntestinal refers to the intestine, the part of the digestive tract that extends from the stomach to the anus. Intestinal diseases affect the small and/or large intestine. infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. caused by threadworms of the genus Strongyloides. These parasites can nest in the intestinalIntestinal refers to the intestine, the part of the digestive tract that extends from the stomach to the anus. Intestinal diseases affect the small and/or large intestine. lining and cause a variety of symptoms, including DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., Vomiting, and Weight loss.
How do dogs get infected with Strongyloides? Dogs can become infected through contact with contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. soil, water, or feces. The larvae of Strongyloides can penetrate through the skin or be ingested orally. In some cases, the infection can also be transmitted from the mother to the puppies.
What symptoms do dogs with strongyloidiasis show? The most common symptoms include DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., Vomiting, Weight loss, loss of appetite, and weakness. In severe cases, RespiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress may also occur if the larvae migrate to the lungs.
How is strongyloidiasis diagnosed in dogs? DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is usually made by a stool examination, in which the larvae or eggs of the parasites are identified under the microscope. Modern molecular tests such as PCR can also be used to confirm the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease..
What treatment options are available for strongyloidiasis in dogs? Treatment usually includes antiparasiticsAntiparasitics are medications or substances used to treat parasitic infestations, such as worms, protozoa, and ectoparasites. They work by killing the parasites or inhibiting their growth. that are specifically effective against Strongyloides. It is important to carry out the treatment according to the veterinarian’s instructions to ensure complete eliminationElimination refers to the process by which waste products and toxins are removed from the body. This includes excretion via the kidneys (urine), intestines (stool), lungs (breath), and skin. of the parasites.
Can humans be infected by dogs with strongyloidiasis? There is a potential risk of zoonotic transmission, especially in areas with poor hygienic conditions. Humans can become infected through direct contact with contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. soil or water.
How can the spread of strongyloidiasis in dogs be prevented? Good hygiene and regular deworming are crucial to prevent the spread of the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. Dog owners should ensure that their pets do not have access to potentially contaminatedContaminated describes something that has been polluted by harmful microorganisms, chemicals, or other dangerous substances. In veterinary medicine, this can affect food, water, toys, or the environment. soil or water.
Is there a way to vaccinate dogs against strongyloidiasis? Currently, there is no vaccineA vaccine is a substance that stimulates the immune system to develop immunity against specific pathogens without causing the disease itself. Vaccines may contain weakened or inactivated pathogens, toxoids, or recombinant antigens. against strongyloidiasis in dogs. However, research is working on developing possible vaccinationVaccination is the process of administering a vaccine to develop immunity against a specific infectious disease. It is one of the most effective methods of prevention of infectious diseases. strategies to prevent future infections.
How common is strongyloidiasis in dogs? The prevalence of strongyloidiasis varies by region. In some tropical and subtropical areas, the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. may be more common, while it is less common in temperate climates.
What should dog owners do if they suspect their dog is infected? If a dog owner suspects that their dog is infected with Strongyloides, they should seek veterinary attention immediately. Early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and treatment are crucial to protect the dog’s health and prevent the spread of the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease..

You can find an interesting overview of gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. problems in dogs, supplemented with information on the intestinalIntestinal refers to the intestine, the part of the digestive tract that extends from the stomach to the anus. Intestinal diseases affect the small and/or large intestine. microbiome and the importance of probiotics, here: https://petsvetcheck.de/fachbeitrag/magen-darm-probleme-beim-hund/