In the West, I don’t believe that there is a single case of a child being blinded1 by cat faeces but their eyesight can be negatively affected in very rare cases. The infections can be treated. It is worth mentioning that dog faeces can also cause the same problem. Precautions should be taken.
There are two parasites that can do the damage. The first is toxoplasmosis and the second is the roundworm parasite. Toxoplasmosis is very extensively discussed on the Internet. Some people like to exaggerate the dangers of toxoplasmosis. It is known to even these people that an estimated 60 million people in the US carry the parasite. Most of the infections come from handling raw foods incorrectly.
For most people toxoplasmosis causes no or few symptoms and the condition passes without further problems. Sometimes, rarely, people can develop complications one of which is “ocular toxoplasmosis”. The parasite causing toxoplasmosis can remain inactive at the back of the eye for a long time. It can become active if the person’s immune system is depressed (by drugs for instance). And it can cause inflammation and scarring in the eye. It can affect one or both eyes. It can cause blurred vision, reduced or loss of vision and floaters. There are treatments and steroids can be used to reduce swelling.
Obviously, children are more at risk of ingesting the parasite because they play on the ground and put their hands into their mouths.
The other parasite is, as mentioned, the roundworm. The condition that it can cause in humans is called toxocariasis. It is also a very rare infection. Once again children are more likely to come into contact with soil contaminated by roundworm eggs which hatch into larvae and penetrate the walls of the digestive tract. In very rare cases they can migrate to the eyes. In the UK there are around 50 cases reported annually and usually children are infected. There are 65 million people in the UK. You can see therefore how rare this disease is.
If an eye is affected by toxocariasis there is, a risk of permanent vision loss but prompt attention can reduce this risk. A blood test is used to detect the disease. In addition an eye test may be required.
The roundworm parasite causing this lives in the digestive system of foxes, cats and dogs. The worms produce eggs. These eggs are released in the faeces of the animal which contaminates the soil. Humans become infected if the contaminated soil enters their mouth. The infection is not transmitted from person to person.
Good hygiene practices reduces the chances of developing toxocariasis. This means washing hands with soap and warm water after coming into contact with sand or soil. Some people recommend washing your hands after handling your cat or dog but I don’t think that this is practical and bearing in mind the extreme rarity of this condition I don’t think it is necessary but you should seek professional advice if you have concerns after reading this.
Of course, most cats and probably dogs are dewormed as a matter of routine. Obviously, this will significantly reduce the risk. But not everyone deworms their cat or dog and in public places dogs are common.
An example of a girl contracting toxocariasis is that of Millie Knight. Her story was reported in the Daily Mail online. The infection remained dormant for several years from aged one and she had no symptoms. When she was six the condition became active in her left eye. She felt poorly. The teacher noticed that her eyesight was not as good as it once was. The doctors realised what had happened. Millie has scarring in her central vision. She is classified as B2 in disability terminology. She is visually impaired. Millie won’t let her poor eyesight hold her back as she wants to be part of the Winter Paralympic ski team.
Note 1: I have said I don’t believe that a child has blinded in the opening sentence. This is because to be blinded as to become completely blind which means both eyes do not function at all. These conditions can affect the eyesight of humans negatively but my research indicates that nobody has been completely blinded.
Associated: Can I get toxoplasmosis by kissing my cat?
Sources: Daily Mail online, NHS UK, American Association for Paediatric Ophthalmology and Strabismus
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