Toxocariasis: Symptoms, Types, Causes and Treatment

Toxocariasis is a parasitic disease that often flies under the radar, yet it affects millions globally, especially children. Caused by the larvae of roundworms commonly found in dogs and cats, this zoonotic infection can lead to a range of symptoms—from mild and self-limiting to severe, organ-threatening complications. Understanding toxocariasis is essential not just for those in endemic regions but for anyone who interacts with animals, gardens, or even visits playgrounds. This article breaks down the symptoms, types, causes, and treatment options for toxocariasis, synthesizing the latest research to deliver clear, evidence-based insight.

Symptoms of Toxocariasis

Toxocariasis can be a silent invader, presenting with a broad spectrum of symptoms—or sometimes none at all. When symptoms do occur, they vary depending on which body system is affected, the intensity of infection, and the individual’s age or immune status. Recognizing the signs is crucial for timely diagnosis and treatment.

Symptom	Description	Common in Children/Adults	Source(s)
Abdominal pain	Recurrent or persistent pain	Children	1, 3, 4
Headache	General or recurrent headaches	Children, Adults	1, 5
Cough/Wheezing	Respiratory symptoms	Children, Adults	2, 4
Vision loss	Reduced or lost visual acuity	Children, Adults	2, 1, 8
Skin rash	Itchy or non-specific rashes	Children, Adults	3, 4
Fever	Low-grade or persistent fever	Children, Adults	4, 3, 5
Lymphadenopathy	Enlarged lymph nodes	Children, Adults	1, 3, 4
Hepatosplenomegaly	Enlarged liver/spleen	Children	3, 4
Eosinophilia	Elevated eosinophil count	Both	1, 3, 4, 5
Neurological symptoms	Seizures, myelitis	Rare, both	4, 6, 14
Cardiac symptoms	Myocarditis, pericarditis	Rare, both	5, 15

Table 1: Key Symptoms of Toxocariasis

Common and Non-Specific Symptoms

Most people with toxocariasis are asymptomatic, but when symptoms emerge, they are often non-specific. In children, recurrent abdominal pain, headache, cough, and loss of appetite are frequent complaints. Skin manifestations, such as rashes, may occur. Lymphadenopathy (enlarged lymph nodes) and fever are also common, particularly in the early stages or with more systemic involvement. Eosinophilia—a higher than normal count of eosinophils (a type of white blood cell)—is a hallmark laboratory finding but is not exclusive to toxocariasis 1, 3, 4.

Organ-Specific Manifestations

• Ocular involvement can result in vision loss, strabismus (misalignment of the eyes), retinitis, or even retinal detachment. Notably, only a minority of those with ocular changes initially report visual symptoms 1, 2, 8.
• Neurological symptoms are rare but serious, including seizures, myelitis, or behavioral changes. In some cases, these symptoms may be the first or only indication of infection 4, 14.
• Cardiac involvement—though extremely rare—can manifest as myocarditis, pericarditis, or even life-threatening cardiogenic shock 5, 15.

Severity and Course

While symptoms can persist or recur, especially in children, many individuals recover with or without treatment. However, severe disease involving the eyes, heart, or brain can lead to chronic disability 1, 4, 5, 14.

Types of Toxocariasis

Toxocariasis is not a one-size-fits-all disease. Its clinical presentation can be classified into several distinct types, depending on which tissues are affected by the migrating larvae. Understanding these types is key to recognizing the full spectrum of the disease.

Type	Key Features	Typical Age Group	Source(s)
Visceral larva migrans (VLM)	Multi-organ involvement (liver, lungs, CNS); systemic symptoms	Children	2, 3, 6, 8, 9, 10, 11, 14
Ocular larva migrans (OLM)	Eye involvement; vision loss, strabismus	Children, Adults	1, 2, 8, 10, 14
Covert toxocariasis	Mild, non-specific, or subclinical symptoms	Children, Adults	1, 6, 8, 9, 13, 14
Neurotoxocariasis/NLM	CNS involvement; seizures, myelitis	Rare; Both	6, 8, 9, 14
Asymptomatic	No apparent symptoms, positive serology	Both	6, 9, 13, 14

Table 2: Types of Toxocariasis

Visceral Larva Migrans (VLM)

VLM is the classic, systemic manifestation of toxocariasis. It occurs when Toxocara larvae migrate through major organs like the liver, lungs, and, less commonly, the central nervous system. Symptoms are often generalized—fever, abdominal pain, cough, hepatomegaly, and marked eosinophilia. VLM is especially common in young children who are more likely to ingest contaminated soil 2, 3, 6, 9, 11.

Ocular Larva Migrans (OLM)

OLM is characterized by eye involvement, which may lead to visual disturbances, strabismus, or even permanent blindness. OLM can occur in both children and adults, sometimes with few or no other symptoms. Because the infection is usually localized to one eye, systemic signs are often absent 1, 2, 8, 10.

Covert Toxocariasis

This form presents with mild or non-specific symptoms—headache, abdominal discomfort, cough, or skin rash. Most cases are self-limited and go undiagnosed, especially in adults. Covert toxocariasis is the most common form and may be detected only through serology or incidental laboratory findings such as eosinophilia 1, 6, 8, 9, 13.

Neurotoxocariasis

A rare but severe type, neurotoxocariasis involves the central nervous system. Patients may present with seizures, myelitis, or behavioral changes. Early recognition and treatment are essential to prevent permanent neurological damage 6, 8, 9, 14.

Asymptomatic Toxocariasis

A significant proportion of infections are asymptomatic, discovered only by positive serologic tests. The vast majority of people with toxocariasis fall into this category, highlighting the often silent nature of the disease 6, 9, 13, 14.

Causes of Toxocariasis

The roots of toxocariasis lie in the close association between humans, domestic animals, and the environment. Understanding how the infection is acquired is key to prevention and control.

Cause	Transmission Mode	Main Host(s)	Source(s)
Ingestion of eggs	Fecal-oral (contaminated soil/food)	Dogs, Cats	7, 10, 11, 12
Contact with pets	Direct exposure, especially puppies/kittens	Dogs, Cats	7, 10, 11
Environmental exposure	Sandboxes, parks, gardens	Dogs, Cats	7, 10, 11, 12
Poor hygiene	Lack of handwashing, geophagia	Humans	2, 7, 11
Inadequate pet care	Infrequent deworming, improper feces disposal	Pets	2, 7, 10, 11

Table 3: Main Causes and Transmission of Toxocariasis

Life Cycle and Transmission

Toxocariasis is caused by the larvae of Toxocara canis (dog roundworm) and Toxocara cati (cat roundworm). These parasites reproduce in the intestines of their definitive hosts—dogs and cats. Eggs are shed in animal feces, contaminating soil, sandboxes, gardens, and even public parks. Within a few weeks, these eggs become infectious. Humans, especially children, accidentally ingest the eggs when they put contaminated hands, food, or objects in their mouths 7, 10, 11.

Risk Factors

• Close contact with pets—particularly puppies and kittens, who are most likely to harbor the worms.
• Playing in contaminated environments, such as sandboxes and playgrounds.
• Poor hygiene, including infrequent handwashing, especially after outdoor activities or contact with animals.
• Pica or geophagia—the habit of eating soil or dirt—is a notable risk factor in children 2, 7, 11.

Contributing Environmental and Social Factors

• Inadequate pet deworming and lack of responsible pet ownership contribute to environmental contamination.
• Improper disposal of animal feces further spreads infectious eggs.
• Wild and stray animals also serve as reservoirs, complicating eradication efforts 7, 10, 11.

Treatment of Toxocariasis

Prompt treatment is essential to minimize complications, especially in severe cases. The therapeutic approach depends on the clinical form, organ involvement, and severity of symptoms.

Treatment	Indication	Additional Measures	Source(s)
Albendazole	First-line for VLM, covert, some OLM	Repeat courses for persistent symptoms	1, 2, 6, 11, 14
Mebendazole	Alternative to albendazole	Similar efficacy	2, 14
Corticosteroids	Severe inflammation, OLM, myocarditis	Used with antihelmintics	2, 5, 14, 15
Surgery	Ocular involvement, complications	Ophthalmic surgery	2
Supportive care	Symptom management	ICU for severe cases	5, 15
Prevention	Hygiene, pet deworming, feces disposal	Public education	2, 7, 10, 11

Table 4: Treatment and Prevention Strategies

Antiparasitic (Anthelmintic) Therapy

• Albendazole is the most widely used medication, typically administered at 15 mg/kg/day for 5 days. Some cases, especially those with persistent symptoms or high antibody titers, may require repeated courses 1, 2, 6, 14.
• Mebendazole is an alternative with similar efficacy; choice depends on local availability and patient tolerance 2, 14.
• Thiabendazole is another option, though less frequently used 11.

Adjunctive Therapies

• Corticosteroids are recommended in cases of severe inflammation—especially with ocular involvement, myocarditis, or neurological disease. They help control tissue damage caused by the immune response 2, 5, 14, 15.
• Ophthalmic surgery may be necessary for retinal detachment or other serious eye complications 2.
• Supportive care, including ICU admission, may be necessary for life-threatening complications such as cardiac involvement 5, 15.

Monitoring Response and Follow-up

• Successful treatment typically results in symptomatic improvement, reduction of eosinophilia, and decrease in antibody titers over weeks to months.
• Some symptoms (e.g., headaches) may persist even after successful therapy.
• In a subset of cases, symptoms may remain despite negative serology, highlighting the diagnostic and therapeutic challenges 1, 14.

Prevention

• Regular deworming of pets, beginning at an early age.
• Proper disposal of pet feces and discouraging pets in public parks and sandboxes.
• Personal hygiene: Handwashing after soil contact, discouraging pica in children.
• Public education on the risks and prevention of zoonotic diseases 2, 7, 10, 11.

Conclusion

Toxocariasis is a complex and often underestimated zoonotic disease. Its symptoms can range from mild or absent to severe, depending on the form and organ involvement. Prompt recognition and treatment are crucial to prevent complications, especially in vulnerable populations such as children. Prevention strategies, including responsible pet ownership and public education, remain the cornerstone of controlling this neglected disease.

Key Takeaways:

• Symptoms vary from non-specific (abdominal pain, headache, rash) to severe organ-specific manifestations (vision loss, myocarditis, neurological deficits) 1, 2, 3, 4, 5, 6.
• Five main types: visceral, ocular, covert, neurological, and asymptomatic toxocariasis 6, 8, 9, 14.
• Caused by accidental ingestion of Toxocara eggs, mainly from environmental contamination by dog and cat feces 7, 10, 11.
• Treatment relies on antiparasitic drugs (albendazole, mebendazole), sometimes with corticosteroids or surgery for severe cases 1, 2, 14, 15.
• Prevention is essential: regular pet deworming, hygiene, and safe disposal of animal waste 2, 7, 10, 11.

By staying informed and practicing good hygiene and responsible pet care, we can reduce the burden of toxocariasis and protect vulnerable communities worldwide.