Recent cases of scabies in Spain or worm meningitis in the US remind us that in developed countries we are not safe from parasitic diseases.

Illustration of a tick.

Who does not know that “scabies with pleasure does not itch”? Today many of those who hear this saying for the first time should be explained what scabies is. Development, medicine, and hygiene habits have turned many previously common pests into rarities. Except for the perennial scourge of lice in schools, the urban citizen of western countries may think parasites are a thing of the past, and today only a third world problem. But recent outbreak of scabies in a Toledo school It is not a rare case, nor is this the only parasite that can attack us in developed countries. We review some of them.


Scabies is always itchy, even in the highly unlikely event that someone was willingly carrying tiny creatures digging tunnels in your skin. The scabies ripperSarcoptes scabiei) is a mite less than one millimeter that is contracted by contact with the skin of an infected person, or with the materials that he has touched or dressed. They can happily spread over almost the entire surface of the body, burrowing galleries and leaving eggs and droppings buried under the skin.

Despite what is often believed, this disease it’s not just a post-war thing: in Spain they have been notified several outbreaks in recent years, especially in hospitals, nursing homes and prisons. The fact that it infects not only humans, but also other mammals, facilitates the occurrence of occasional outbreaks, which spread easily where many people live.

Fortunately, and beyond the strong itching, the disease is usually benign and the treatment is effective, although the usual thing is that all the people who live together must follow it, since the parasite is very contagious.


Pinworms may also seem like a thing of the past, but they are not. More than one father and mother will have discovered with horror in the feces of their children a kind of white threads of approximately one centimeter that, worst of all, move. Is he oxiuro (Enterobius vermicularis), a more common parasitic worm in developed countries than it might seem. In the US, it is estimated that it affects just over 11% of children. In Spain, a 1997 study in the child population of the Guadalquivir valley found an incidence of 20%.

Contrary to what might be believed, children do not get it because an infected dog or cat has defecated in the sand of the park: pinworm is an exclusively human parasite. It lives in the large intestine, from where the female leaves at night to deposit the eggs around the anus. Children often scratch, which transfers the eggs to the fingers and nails, facilitating their spread. It is common for those affected to be reinfected by sucking their fingers or biting their nails, so it is important to wash your hands before eating. Luckily, pinworm doesn’t usually cause serious symptoms, other than itchiness. The infestation has an effective treatment.


La Billiards or Schistosoma (Schistosoma) is a worm that it is usually restricted to the tropical fringe of the planet, where it produces the second disease with the greatest impact after malaria. Schistosomiasis is a souvenir undesirable that many tourists take home after a trip to the tropics, because of the bad idea of ​​bathing in that oasis so appetizing; the worm incubates in freshwater snails, goes outside and makes its way through the skin of bathers, to then circulate through the blood until it settles in the organs. The disease has a low mortality, but can become chronic if left untreated.

Sporadically, the schistosome can appear in our latitudes. In 2014, a group of German tourists contracted the disease in a river on the French island of Corsica. In 2016, a new case was reported, for which the authorities warned that the presence of the parasite may be permanent on the island. The snail that acted as intermediate host in these cases, Bulinus truncatus, also lives in Spain. This does not mean that the parasite is present in our country, but the mollusk could spread the disease if the worm reached the waters where it lives.

Drilling worm

In 2016, the authorities of the state of Florida (USA) reported the detection of deer infected by the screwworm, a scourge that the US had eradicated from its territory more than 30 years ago. The worm is actually the larva of the fly Cochliomyia homovorax, which has the ugly habit of laying its eggs in the wounds of living animals, including humans. The larvae feed on the meat by sinking into it like a corkscrew, which gives the parasite its name.

The disease is more common in tropical countries. In the early 1980s, the US and Mexico They managed to eradicate it from their territories thanks to a campaign to liberate sterile males., which mated with wild females without producing offspring.

The infestation is not usually fatal in humans; but in addition to the nightmare of carrying fly larvae under the skin, eating the meat, the healing process is most grotesque, since the larvae must be extracted one by one with tweezers. In 2007, American doctors used bacon to attract the larvae that had colonized the scalp of a girl during a vacation in Colombia. In total they extracted 142 larvae.


As in all Eden a snake is never missing, the authorities of Hawaii are alarmed by the recent appearance of several cases of a parasitic disease that seems to be increasing its incidence in the American archipelago: angiostrongyliasis. Under this tongue twister hides a parasitic worm called Angiostrongylus, that can invade the brain causing life-threatening meningitis.

The Angiostrongylus It is not usually a parasite of humans, but especially of rats, which expel it in their feces. As in the case of the schistosome, some snails act as intermediate hosts, but the worm can also be found in freshwater crabs and frogs. Accidental contagion to humans occurs through these animals, either directly or through contaminated food.

In many cases the infection in humans does not cause symptoms. But when it does, they can be terrifying and disabling. One affected on the island of Maui described the pain like that of a needle piercing his brain into his eye. The island authorities suspect that the transmission vector could be an invasive slug whose population infected by the parasite is estimated at 80%.

The bad news is that There is no specific treatmentAccording to the US Center for Disease Control, antiparasitic efficacy has not been proven, and toxins from dead worms may also worsen neurological symptoms. The Maui patient is receiving only pain relievers and antibiotics to control possible secondary bacterial infections.