May 2010




Where does your water come from?

by Matt Young EyeWorld Contributing Editor


Ophthalmologists often worry about outbreaks of ocular disease caused by something used in clinic, such as a contaminated knife or sterilizer. A new study suggests an outbreak of ocular disease could be caused by something as seemingly innocuous as drinking water. In a southern India city, 248 patients acquired retinitis via systemic infection with toxoplasmosis—likely resulting from bad water. “Most of our patients used municipal drinking water for drinking/consumption purposes, indicating municipal drinking water as the most probable source of infection,” according to lead study author Manohar B. Balasundaram, M.S., Uvea Clinic, Aravind Eye Hospital, Madurai, India, and Postgraduate Institute of Ophthalmology, Coimbatore, India. “Small rivers and streams from the hills in the west and north of Coimbatore city contribute to its large reservoirs, the source of its municipal drinking water.”

The study was published in the January 2010 issue of Archives of Ophthalmology. Dr. Balasundaram hopes the study serves as a warning. “The purpose of this article is to alert all concerned that an outbreak like this could take any population by surprise, can involve all age groups and sexes, and that ocular involvement can occur without any significant evidence of systemic disease,” Dr. Balasundaram noted. “If a big population is affected, there could be significant ocular and systemic morbidity as well as enormous stress on the public health system.”

The investigation

Dr. Balasundaram analyzed 248 patients with acquired retinitis caused by systemic infection with toxoplasmosis, and eliminated the possibility that the disease could have been congenital in nature.

It was important to do this because, as Dr. Balasundaram noted, most retinitis cases are thought to have a congenital link. “The clinical presentation of our patients differs from those of patients with toxoplasmic chorioretinitis that occurs as a late sequela of infection that occurs in utero.” “Congenital disease tends to be bilateral, while acute acquired toxoplasmosis tends to be unilateral, single, and variable in size. Most of our patients (n = 242; 97.58%) had unilateral disease, while only 6 (2.42%) had bilateral disease. Most patients presented with solitary, discrete, active focus of retinochoroiditis with no preexisting scars, consistent with acquired ocular toxoplasmosis.”

The mean age of the patients, 40.47 years, was higher than in those with recurrent congenital disease. Toxoplasmic retinochoroiditis typically occurs in the second and third decades of life, Dr. Balasundaram noted. “All had laboratory evidence of acquired systemic infection with Toxoplasma gondii, and all favorably responded to antitoxoplasma therapy,” Dr. Balasundaram noted. “Toxoplasma IgM and IgG antibodies were detected, suggesting recently acquired systemic disease.”

There were also factors that pointed to an outbreak. “The striking aspect in this case series was the sheer number of patients who reported to our hospital: 28 in September, 56 in October, 51 in November, 43 in December 2004, and then 24 in January, 15 in February, 8 in March, 10 in April, 12 in May, and 1 to 2 cases per month until July 2005,” Dr. Balasundaram reported. Those infected had something in common. “A noticeable feature was that 209 patients (84.27%) were residents of a city and its suburbs, implying the source of infection to be common to everyone infected,” Dr. Balasundaram reported. Although Dr. Balasundaram couldn’t pinpoint the source of infection, he deduced it likely came from the city’s municipal water, as mentioned. Other methods of exposure, Dr. Balasundaram noted, could have been oocysts in cat feces, consumption of inadequately cooked infected meat, leukocyte transmission, and potentially consumption of raw milk. Results after treatment were excellent, Dr. Balasundaram noted. “Visual acuity worsened from baseline values in only 11 eyes (5.52%),” Dr. Balasundaram reported.

William B. Trattler, M.D., cornea specialist, Center for Excellence in Eye Care, Miami, commented that drinking water is not the most typical method of exposure for toxoplasmosis, citing instead eating raw pork and inhaling cysts from cat feces as more likely causes. He also said that water in the United States is heavily chlorinated, killing bugs including those that might transmit toxoplasmosis easily. That said, Dr. Trattler was intrigued and further researched this issue, finding that an outbreak of toxoplasmosis occurred in 1995 in Canada. “There was a whole run of this, involving hundreds of individuals,” he said. The cause was linked to a reservoir supplying water to Greater Victoria. The system used unfiltered, chloraminated surface water. “It’s very interesting that that happened,” Dr. Trattler said, adding that it’s important to filter water.

Editors’ note: Dr. Balasundaram has no financial interests related to this study. Dr. Trattler has no financial interests related to his comments.

Contact information

Trattler: 305-598-2020,

Where does your water come from? Where does your water come from?
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