Xiao Yu is five years old, his best friend is his mother gave him a puppy Bobby on his third birthday. Every day, Xiaoyu and Bobbi are inseparable to play together. Recently, when his mother took a picture of Xiaoyu, she noticed that the reflection in the pupil of his right eye was not the usual red color, but yellowish white, like a cat’s eye. The mother hurriedly took Xiaoyu to the hospital, and once she checked his vision, she realized that the vision of Xiaoyu’s right eye was so bad that he could only see the finger in front of him. The ophthalmologist carefully examined Xiaoyu’s eyes, and after taking blood tests, told the mother that Xiaoyu had “ocular canine roundworm disease”, which had seriously affected her vision and required medication, and in serious cases, surgery might be required. What is canine roundworm disease? Toxoplasma gondii is a common parasite that lives in the intestinal tract of dogs (canine roundworms) or cats (feline roundworms) and is called canine roundworm disease when it infects humans. It is most common in children under 10 years of age, especially those who have dogs or cats in their homes or have close contact with them. How did my child become infected with Toxoplasma gondii? Why didn’t my father and I get infected? Toxoplasma gondii in humans is caused by the larvae of Toxoplasma gondii. The eggs are excreted in the feces of an infected cat or dog, contaminate areas where children may play – floors, sandboxes, shoes, toys, etc. Once swallowed by children, they hatch into larvae that travel through the walls of the gastrointestinal tract to the child’s liver, lungs, eyes, and other places. Children are at greater risk of infection if they: are 1-4 years old; frequently put their hands in their mouths; and do not like to wash their hands. Adults have actually contracted Toxoplasma gondii from eating raw contaminated meat, liver or soil fetishes, but 80% of the cases are in children under 16 years old. In addition, human-to-human transmission of Toxoplasma gondii is not possible. How do I know if my child has Toxoplasma gondii? Systemic symptoms include fever, cough, croupy lungs, loss of appetite, abdominal pain, enlarged liver, spleen and lymph nodes, and hives (bumps). Systemic canine toxoplasmosis is usually treated with the anthelmintic albendazole. The eye is one of the most common sites of attack for Toxoplasma gondii, and the ocular manifestations are relatively distinctive and characteristic, so the disease is often diagnosed first by ophthalmologists. The earliest manifestation of the eye should be decreased vision, but due to the child’s limited ability to express or not noticing because of normal vision in the other eye, the narrative when coming to the clinic is mostly a skewed eye position, abnormal pupil reflection or swelling around the eye. If the above-mentioned symptoms occur and ocular toxoplasmosis is suspected, the child should be promptly brought to the ophthalmology department of a regular hospital for consultation. The diagnosis can be confirmed in most cases through ophthalmic examination and examination of serum antibodies and blood cell components. How serious are the consequences of ophthalmic toxoplasmosis? The treatment of ocular toxoplasmosis is relatively tricky and complex compared to other infections. The outcome varies greatly depending on the extent of the damage caused by the infection, the timing of treatment, and the response to treatment. Children’s eyes are extremely delicate and fragile, and the damage caused by Toxoplasma gondii in the eye not only directly damages the lens, vitreous, retina, choroid, and other ocular structures, but also causes disruption of vision development and amblyopia due to abnormal function of these structures. Children with mild cases can retain some vision after timely and effective treatment, while children with severe or delayed cases may lose their vision forever, and even the shape of the eye may change, with eye atrophy, black eye (cornea) degeneration and whitening, etc. How should I treat my child with ocular toxoplasmosis? Mild, stable cases of ophthalmoplegia can be treated without treatment and monitored closely, but if the lesions are vision-threatening and progress in activity, they should be treated promptly. Standard medication is anti-inflammatory treatment with corticosteroids, some doctors will combine this with anti-parasitic treatment, and if the worm reaction in the eye causes cataracts, persistent vitreous clouding, traction or even retinal detachment, the most complex surgical treatment in ophthalmology, vitrectomy, may be required to save the eye. Any treatment should be done under the guidance and supervision of an ophthalmologist. How can I prevent ocular canine archaeal ascariasis? In developed countries such as Europe and the United States, pet dogs and cats have strict deworming and immunization regulations, but even so, 20% of dogs in the United States can still excrete Toxoplasma gondii eggs in their feces, 24% of park soil samples in the United Kingdom can detect contamination with Toxoplasma gondii eggs, and a study in China found Toxoplasma gondii infection rates of 41.67-50% in the feces of free-ranging dogs. Therefore, the prevention of Toxoplasma gondii in dogs should be a systematic project. The government health department should develop prevention and extermination measures, especially for public sandpits, playgrounds, etc. Some places in Japan, Europe and the United States have started to build protective nets or covers around sandpits in parks to prevent dogs and cats from entering the sandpits to defecate; canine roundworm is more likely to occur in preschool and school-age children, so kindergarten and school educators should also know certain knowledge and take preventive measures; as parents, they should teach their children to wash their hands often, cut their nails in time, and not put things on the ground or dirty hands into their mouths; Studies have shown that puppies under 6 months of age are more contagious, so families with dogs and cats, especially puppies as pets should regularly go to formal institutions for deworming and immunization. Some countries in Europe, the United States, Japan and other countries have set aside places for dogs in parks and require dog and cat owners to clean up, seal and discard feces centrally in a timely manner in signage in public places. We often say, “dogs are man’s best friend”, dogs and cats bring us warmth and joy; but this friend may also bring unintentional harm to children. With the efforts of doctors, Xiao Yu saved his right eye, but due to the destruction of the worm, he will never be able to see the world as clearly as his left eye. In order to prevent more children from having regrets like Xiao Yu, we hope that everyone will learn about ocular canine archaic roundworm disease, educate children to develop good hygiene habits, and protect our children from harm from their pet friends!