Researchers from Baylor College of Medicine, Texas Children's Hospital and The University of Texas Health Science Center at Houston advise physicians to screen patients for kidney disease if they have a history of infection with West Nile virus.
In a study of 139 patients infected with West Nile virus in the Houston-area, researchers from the three institutions found indications of varying degrees of kidney disease in 40 percent of those who had the mosquito-borne illness. Their findings appear online in the journal PLoS ONE.
Progression of disease
"We are in the process of researching the relationship between West Nile virus infection and kidney disease, but this study now allows us to understand the prevalence and progression of kidney disease in those previously infected with West Nile virus," said Dr. Kristy Murray, associate professor of pediatrics tropical medicine at BCM and Texas Children's, and senior author of the paper and principal investigator of the West Nile virus research program.
West Nile disease results from the bite of an infected mosquito. It causes fever, headache and body aches. In its most severe form, it can cause high fever, neck stiffness, stupor, coma, tremors, convulsions, muscle weakness and paralysis. In severe cases, it can cause encephalitis or inflammation of the brain and its sufferers may have to be hospitalized. While it is known that those with the most severe form of the disease can suffer long-term nerve and brain problems, long-term kidney problems have not been identified before, said Murray. Murray and Melissa Nolan, the first author of the paper, are with the National School of Tropical Medicine at BCM.
"An estimated two million Americans have been infected with West Nile, and we advise physicians to screen them for potential kidney disease, because if you catch it early, then the person can be monitored and treated should the disease progress," said Nolan, senior research coordinator at BCM and Texas Children's.
Researchers collected blood and urine samples from the 139 West Nile patients in the study and asked them general questions about their symptoms and health. They then followed up with the patients every six months from the study's starting dates in April - Nov. 2010.
The researchers found that 10 percent of the patients had test results consistent with stage three or greater chronic kidney disease and 30 percent had results consistent with stages one or two.
Chronic kidney disease is divided into five stages. The first two are milder forms of disease and stage three is a moderate form. Stage four and five are the more severe forms that are usually irreversible and can result in dialysis or kidney transplantation.
"Stage three is a tipping point where patients either recover or progress onto later stages," said Nolan. "However, since there are no symptoms of kidney disease until later stages, many people are not aware that they have it."
Researchers also found that traditional risk factors associated with kidney disease, such as diabetes, hypertension, and older age, were not statistically associated with kidney disease in the study participants. The one thing they did find significant was that those with more severe West Nile infections were at higher risk for kidney disease.
"Our next steps are going to be to understand that relationship between infection and kidney disease," said Murray. "We believe we now have good evidence towards an association. There are many long-term and serious health effects related to infection with this virus, and we want to strongly encourage people of all ages to take precautions against mosquito bites."
Others who took part in the study include Amber S. Podoll, Katherine M. Akers and Kevin W. Finkel with the UTHealth Medical School and Anne M. Hause with The University of Texas School of Public Health, which is a part of UTHealth.
Funding for this study came from the Gillson Longenbaugh Foundation and the National Institutes of Health.
The full report can be found at the journal PLoS ONE.