Insect-, bird-borne diseases remain a threat in state

by Wally Northway

Published: October 24,2005

In 1878, Mississippi was hit with a “natural” disaster that, in terms of victims, far surpassed Hurricane Katrina. An outbreak of yellow fever led to hundreds of deaths in Mississippi (more than 4,000 nationwide), depopulated communities and widespread lawlessness and panic. The frightening part was that no one knew the source of the disease, and there was no cure.

Today, scientists know the source of yellow fever —mosquitoes — and there is a vaccine. But other insect-borne diseases are still a statewide health concern and have no known treatment. And now a bird-borne disease — avian flu — is taking center stage, and some health experts believe it could be the next pandemic.

The buzz about WNV

The insect-borne disease that has proven the deadliest in Mississippi over the last few years is West Nile virus (WNV). People bitten by infected mosquitoes develop flu-like symptoms. Occasionally, the illness can become severe, leading to potentially fatal encephalitis and meningitis.

According to the Mississippi State Department of Health, four Mississippians died from WNV in 2004. This year as of October 12, there have been 64 human cases of WNV identified in Mississippi (eighth highest in the U.S.), and it has claimed four lives. Four new human cases were identified the week of October 4-11 alone, and there is fear that this number will climb in the aftermath of Katrina.

Dr. Art Leis, a senior scientist at Methodist Rehabilitation Center’s Center for Neuroscience and Neurological Recovery (CNNR) in Jackson and who, along CNNR director Dr. Dobrivoje Stokic, was the first in the world to report the link between WNV and polio-like paralysis in 2000, believes the hurricane created an environment ripe for WNV. Factor in that September is the peak month for the disease, and Leis’ concerns only grow.

“A major issue is you have water collecting everywhere, and mosquitoes are breeding uncontrolled,” he said. “Electrical power has been down, and a lot of people are keeping their windows open or camping out. That makes them vulnerable to multiple mosquito bites.”

State epidemiologist Dr. Mills McNeill said it would be impossible to quantify whether Katrina would add to Mississippi’s risk for a greater outbreak of WNV. September is the historical peak month for WNV, so a jump in cases would not necessarily point to conditions created by the hurricane. The good news about WNV, according to McNeill, is that the disease has not shown any appreciable increase lately, and that it appears the risk is moving westward.

“We had a slight increase in human cases of WNV this year compared to last year, but the number is completely within the expected variation,” McNeill said. “The number of cases is still far below what we saw the first few years that the disease appeared.” He added that the highest risk for the disease, which first appeared in the eastern U.S., appears to be moving steadily westward and away from Mississippi.

He pointed to two factors he believes is helping slow the number of human WNV cases in Mississippi. One is “Fight the Bite,” a public awareness campaign aimed at informing Mississippians on how to avoid being infected. The other is biological — as birds (a host for the virus) build up immunity to WNV, they become less effective as a reservoir for the disease.

Swarm of diseases

WNV is certainly not the only mosquito-borne disease that has invaded Mississippi. However, these diseases seem to be on the wane here, as well.

Eastern equine encephalitis (EEE), in ways, makes WNV seem almost tame. Though human cases occur rather infrequently, the CDC reports that the fatality rate is 35%, and for survivors, 35% face mild to severe neurological problems. While there have been no reported human cases of EEE reported in the state this year, the Mississippi Board of Animal Health has discovered EEE in animals in Mississippi.

St. Louis encephalitis is yet another mosquito-borne illness that threatens Mississippi. There have been no human cases identified in Mississippi this year, but from 1964-1998, there have been 337 cases found in the state, the fifth-highest total in the U.S.

Mosquitoes aren’t the only disease carriers to be aware of, either. Lyme disease is carried by infected ticks, and the bacteria may cause a rash, flu-like symptoms and muscle and joint pain. Left untreated, the disease can produce such symptoms as swelling and pain in the major joints or mental changes months after being infected.

There were 133 human cases of Lyme disease identified in Mississippi from 1994-2003. There were 24 cases of Lyme disease reported in Mississippi in 1996 and 27 cases in 1997, the two worst years. In 2002, the last year for which data is available, 12 cases were identified in Mississippi

Fine feathered flu

If all of these insect-borne diseases weren’t enough, now birds are being watched warily. Avian flu is the newest of global health concerns, and the bird-borne illness has killed dozens of people, predominantly in Asia (more than 40 in Vietnam alone). But the disease has been found not only in poultry but also in migratory birds, and health officials have been concerned about a potential pandemic that could reach the U.S.

Now, those fears — and the disease — are hitting closer to home. In mid-October, it was announced that the avian flu had reached Turkey and Greece, and health and government leaders are now huddled trying to determine what to do and how bad it could get.

McNeill said there is reason for concern, but not panic, even for Mississippians traveling to areas where the risk is the highest. He stressed that the disease is predominantly found in rural areas, and urban outbreaks prompt warnings from health officials. (Airports in Asia are using scanning technology that can actually identify fever in travelers.)

Here at home, McNeill said there is already a pandemic influenza plan in place that can be used to enhance surveillance and expedite the distribution of vaccines. “We are very actively engaged in response to these health concerns,” he said.

Contact MBJ staff writer Wally Northway at northway@msbusiness.com.

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