July 13, 2012
West Nile Virus May Cause Chronic Kidney Disease
Lawrence LeBlond for redOrbit.com - Your Universe Online
Patients who have a history of infection with West Nile virus (WNV) should be screened for chronic kidney disease (CKD), after US researchers have found varying degrees of the life-threatening disease in 40 percent of those patients who also contracted the mosquito-borne illness at an earlier time.
Researchers from three organizations -- Baylor College of Medicine, Texas Children's Hospital and The University of Texas Health Science Center -- studied 139 patients who had been infected with West Nile virus. The teams used the Kidney Disease Outcomes Quality Initiative (KDOQI) criteria, based on the Modification of Diet in Renal Disease (MDRD) formula and urinary abnormalities, to assess risk factors and biomarkers of the disease.
Publishing the findings in the online edition of PLoS ONE, the team found that 2 in 5 of the West Nile patients also had a prevailing form of kidney 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 study leader Dr. Kristy Murray, associate professor of pediatrics at BCM and Texas Children´s.
At the time of the study, which involved mostly white (86%) men (60%) with an average age of 57 years, about 83 percent of the patients were four to nine years post-infection. Based on the KDOQI initiative, 40 percent of the participants showed evidence of CKD, with 10 percent having Stage III or greater and 30 percent with Stage I or II.
The researchers further found that 26 percent of patients had proteinuria and 23 percent had hematuria. Plasma NGAL levels were also elevated in 14 percent of the patients.
WNV results from a bite from an infected mosquito. It causes fever, headache and body ache. In severe cases, it may cause high fever, neck stiffness, stupor, coma, tremors, convulsions, muscle weakness and paralysis. It can also lead to encephalitis or inflammation of the brain and sufferers of the most severe forms may likely need to be hospitalized.
While it has been known that the most severe forms of the disease have been known to contribute to long-term nerve and brain damage, long-term kidney problems have not been identified before, Murray noted.
“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 study coauthor, Melissa Nolan, of the National School of Tropical Medicine at BCM.
CKD is divided into five stages. The first two stages are mild, and the third stage is a moderate form. Stages four and five are the most severe forms and are usually irreversible, often resulting in dialysis or transplantation.
“Stage three is a tipping point where patients either recover or progress onto later stages,” said Nolan, noting that because there are no symptoms in the early stages of kidney disease, many people do not even know they have it.
Whereas traditional risk factors associated with kidney disease include diabetes and hypertension, the researchers found these risks were typically not associated with kidney disease found in the study participants, giving the disease a stronger connection to WNV in the study group.
The researchers will next look at the relationship between WNV infection and CKD.
“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,” Murray said.