Acanthamoeba more widespread in Kerala’s waterbodies than thought earlier

Far from being a random pathogen causing isolated cases of life-threatening brain infections, Acanthamoeba, the ubiquitous free-living amoeba found widely in the environment, is now emerging as a public health concern.

With more people who have exposure to well water alone getting amoebic meningoencephalitis, the Health department fears that Acanthamoeba could be much more widely present in the State’s waterbodies than was thought before.

However, it now emerges that the widespread presence of Acanthamoeba in the State’s ponds, wells and storage tanks had been reported way back in 2013 itself, though meningoencephalitis caused by Acanthamoeba was unheard of then.

Well water

In 2013, research led by Anna Cherian, who was then the Associate Professor of Microbiology at Regional Institute of Ophthalmology (RIO) in Thiruvananthapuram, had established that the glut of unhealing corneal ulcers that were flooding the wards of the hospital was in fact amoebic keratitis caused by Acanthamoeba. Majority of the patients were agricultural or manual labourers living in rural areas and in most of the cases, the source of infection was the household wells.

Her research, “A study on Acanthamoeba keratitis in a tertiary eye care centre South Kerala,” appeared in the Indian Journal of Microbiology Research, January-March, 2018 issue.

“We were getting multiple cases of non-healing corneal ulcers, accompanied by severe pain and inflammation, which raised the strong clinical suspicion of Acanthamoeba keratitis. The patients were poor and many of them ended up losing their eyesight because treatment could not be initiated early,” says P.S. Girija Devi, former Director of the RIO

Dr. Cherian then spent hours with the microscope, examining hundreds of slides of corneal scrapings in search of Acanthamoeba, a parasite that she had seen only in literature. “Through simple microscopic examination, one can see the trophozoites (active form of amoeba) but then this parasite can play hide and seek and remain so hidden in the specimen that continuous observation alone can spot it,“ says Dr. Cherian.

314 cases

From January-December 2013, out of 350 cases of keratitis, Acanthamoeba was isolated from 314. Among the districts, Thiruvananthapuram had 225 cases, Kollam 69, Pathanamthitta 6, and Alapuzha, five cases.

“If not treated adequately and aggressively, Acanthamoeba keratitis can lead to loss of vision. Well water was the source of infection in 243 out of the 314 cases of Acanthamoeba keratitis. We could isolate and culture Acanthamoeba in the water from the household wells of our patients, confirming the source of their infection. We had advised all the patients that they had to chlorinate their wells immediately,“ says Dr. Cherian.

“The epithelial surface of the cornea might have had micro trauma/tear (caused by dust, specks falling in the eye or even from rubbing the eyes). When contaminated water touches the corneal surface, the pathogen enters the eye through these micro tears causing keratitis,” explains Reena Rasheed, Proffesor of Ophthalmology, RIO, who had been involved in the 2013 study.

Highest risk group

Normally, the highest risk group for Acanthamoeba keratitis remains contact lens wearers who expose lenses or eyes to water or fail to practise proper hygiene. But Dr. Cherian’s research is proof that non-contact lens wearers are also at risk, if there are minor tears in the corneal epithelium, followed by exposure to contaminated water.

The researchers also found that Acanthamoeba grew well in water in which E.coli concentration (coliform count) was high. In the lab culture studies, Acanthamoeba grew, feeding on E.coli. This fact is significant, given that various studies have found high coliform count in many waterbodies in the State

Both eye, brain infections

There are no documented cases of a person with Acanthamoeba keratitis developing meningoencephalitis directly through spread from the eye to the brain, even though the organism can cause both eye (keratitis) and brain infections (granulomatous amoebic encephalitis or GAE), clarifies R. Aravind, Head of Infectious Diseases, Government Medical College, Thiruvananthapuram.

“None of our cases of amoebic meningoencephalitis had eye infection. To the best of our knowledge, there is no direct path of infection from eye to brain. However, we now know that Acanthamoeba and Balamuthia species can also enter through skin wounds, especially in immunocompromised individuals. The mass cleaning and chlorination of wells and water storage tanks thus assumes more public health importance than ever,” Dr. Aravind says.