The scientific journal “New England Journal of Medicine” (NEJM) published this week a case report of a patient from Germany who suffered from loiasis, disease caused by a worm in the eye (watch the video above).
The worm that causes loiasis, of the species loa loa, it is frequent (endemic) in central and west Africa, and is transmitted by flies like Chrysops. (The disease is not transmissible from person to person).
The German patient, a 36-year-old anthropologist, was infected during a business trip to the Central African Republic. According to the doctors who reported the case, the woman sought care at a clinic with “a structure similar to a moving worm in the left eyelid”.
Map shows central region of Africa. The German patient with loiasis, a 36-year-old anthropologist, was infected during a business trip to the Central African Republic. — Photo: G1
Ophthalmologist Paulo Schor, director of innovation and professor at the Federal University of São Paulo (Unifesp), explains that the loa loa “It has a predilection for the eye because the fly lands on the eye. It is a very typical disease in Africa. When you look at the back of people’s eyes there, there is a lot of scarring from this disease”, he explains.
The worm migrates through the body through the subcutaneous tissue and can produce areas of inflammatory swelling (known as Calabar swelling).
So, the loa loa it does not directly attack the retina – which is responsible for capturing and transmitting light stimuli so that we can see, but stay close to her.
Left image shows ‘Loa loa’ worm inside patient’s eyelid; in the center and on the right, microscope images show the worm. — Photo: NEJM
When detected by the immune system, our body’s defense reaction to the invader can damage nearby structures. With that, the infected person may lose sight or part of it.
“Leaving the person without vision is a very broad thing: it can affect the cells of the retina, the transparency of the cornea, the cells that drain the aqueous humor [líquido incolor e transparente do olho] and increasing eye pressure, the cells surrounding the optic nerve, and visual field vision. Vision loss is a very broad thing,” explains Schor.
Because of the body’s defense system response, the treatment of the disease also involves drugs that attenuate the immune response.. The German patient was treated with diethylcarbamazine (to eliminate the worm) and prednisolone, a corticosteroid (which mitigates this response).
Doctors reported that no new worms appeared, but they do not mention whether or not there was any loss of vision.
Outside the African continent, the loa loa is extremely rare, but at least one case has already been described in Brazil: in 2012, Unifesp doctors reported the first case of the disease in the country – in a woman originally from Cameroon. She was treated.
Paulo Schor explains that, in Brazil, toxoplasma, which causes toxoplasmosis, is the most worrying parasite. The worm has a “preference” for central nervous system tissue – like the worm. retina, which can lead to blindness.
“The retina is a place that has a lot of this nervous tissue, with a lot of myelin. [toxoplasma] go there and stay closed in this region. Every now and then it opens, and we have a really big attack on our immune system. The reaction is so great that it destroys the surrounding tissue,” explains Schor.
Toxoplasma is found in contaminated food or cat feces and is also transmitted from mother to baby during pregnancy.