Hundreds injured by freshwater sponges
Catfish that enter your urethra while urinating aren't the only risk to bathing humans in the Amazon basin, according to the results of a new study.
Bathers are also at risk from developing painful eye injuries after bathing in waters where freshwater sponges live.
A recent outbreak of eye injuries that occurred at the town of Araguatins, on the right bank of the Rio Araguaia in Tocatins state, Brazil, was found to have been caused by tiny silicious spicules from freshwater sponges.
Hundreds of children and young people suffered serious eye injuries after the sharp silica spicules, known as gemmoscleres, which form part of the supporting elements of sponge skeletons, got lodged in their eyeballs.
Loss of sightMany of the affected children had a gradual loss of sight over a period of a few months, as well as itching, and several developed cataracts and ocular lesions as a reaction to the presence of the glassy spicules.
The study, which has just been published in the medical journal Memorias do Instituo Oswaldo Cruz, says that it took experts some time to find the cause of the outbreak of eye injuries.
"It affected particularly male children and adults and present, as main characteristic, immediate eye irritation and itching after bathing and diving with open eyes in the river waters. This outbreak reached more than 200 children and young people and was initially attributed to helminthic infection.
"Later on, a survey made by technicians of Ministry of Health showed that 80% of the children tested exhibited high levels of IgG antibodies to Toxocara canis.
"However, the large number of registers of itching and skin ulceration caused by sponge spicules in the Amazonian Region, previously reported in the Zoological, Arche-ological, and Historical bibliography led Volkmer-Ribeiro and Batista to do a survey for sponges and its spicules in the water and sediments at several stations of Araguaia river."
Sponge populationA survey of the river where the injuries had occured found a population of 10 different freshwater sponge species, as well as the presence of large numbers of their sharp spicules floating in the water.
Analysis of the spicules revealed that they were gemmoscleres from two species - Drulia uruguayensis and D. ctenosclera.
The study is believed to be the first to show that sponges are capable of causing eye injuries to bathers.
Freshwater sponges are common in Brazilian rivers and a number of species also occur in British lakes and rivers.
For more details see the paper: Volkmer-Ribeiro C, Lenzi HL, Orefice F, Pelajo-Machado M, de Alencar LM, Fonseca CF, Batista TCA, Manso PPA, Coelho J and M Machado (2006) - Freshwater sponge spicules: a new agent of ocular pathology. Memorias do Instituo Oswaldo Cruz. 2006 Dec;101(8):899-903.