Tired, swollen and blistered feet are among the biggest challenges for the thousands of Central American migrants making their way through southern Mexico in hopes of starting new lives in the United States.

Three weeks of pounding the hot asphalt of highways every day takes a toll, especially for those plodding along in flimsy flip flops. Whenever possible, the migrants discard damaged footwear, replacing them with donated shoes found at stops along the way or with spare pairs they carry in backpacks.

The most grueling days demand treks of more than 100 miles (160 kilometers). Migrants eager to find strength in numbers must keep that pace to remain with the group. And they do so in cheap shoes and sweat-drenched socks, which they eagerly peel off at the end of each day.

Blisters are a nasty foe for migrant feet, young and old alike. Red Cross personnel at waystations bandage swollen feet or apply antiseptic to broken blisters. Children wince as their wounds are treated. Flies gather on open sores. The risk of infection is high.

"These are extreme conditions," says Ignacio Escotto, a Mexican vascular surgeon who specializes in treating extremities. Unrelenting contact with hot pavement will cause the feet to swell, he says, while dehydration and malnutrition wreak havoc on soft tissue. "At the end of the day, this articulation must be painful."

Yet the migrants hobble through the pain, determined to reach the U.S. They grin and bear it as they limp along. Those who can no longer take it bow out of the caravan. The Mexican government says around 3,000 migrants have applied for refuge in Mexico in recent weeks and about 500 have asked for assistance to return to their countries of origin.

On Sunday, 21-year-old Marisol Salamanca dug into a pile of donated shoes at a sports facility in Cordoba in search of a replacement for the sandals she has padded around in since leaving El Salvador several weeks earlier. "I keep tripping and hurting myself," she said.

Darwin Hueso, a 39-year-old-farmer from Honduras, was also thrilled to find fresh shoes, even though they were a bit tight and formal. The soles of the work boots he has been wearing for more than 21 days are inflexible and tough.

Adan Lara Barahona, 62, a wiry rancher from Potrerillos, Honduras, dismissed the blisters on his feet as a minor nuisance. "They are drying out already," he said, complaining instead of dizziness brought on by a severe respiratory infection.

There's no turning back for Lara Barahona, who says gangs killed his wife and two of his children seven months ago when he didn't pay them protection money.

Many of the about 4,000 migrants in the caravan have now covered more than 800 miles since setting out from Honduras on Oct. 13, hitching rides on flatbed trucks when possible and they face another more than 800-mile trek to the nearest U.S. border crossing. Clamors have grown in recent days for buses to transport scores from the caravan to the Mexican capital, where the fatigued travelers hope to find respite and medical treatment. Those buses haven't come.

The group now finds itself in the Gulf state of Veracruz, traversing what some call the "route of death" because of the large number of migrants who have disappeared in the state in recent years. It is unclear what part of the U.S. border they will aim for eventually, but their latest overnight stay in Veracruz could be one of their last before they head to Mexico City, a potential launching spot for a broader array of destinations.

Inspired by their progress and outpouring of support from townspeople along the way, several smaller caravans of migrants have formed in Central America in recent weeks in an attempt to improve their odds of making it to the U.S.


Associated Press writer Mark Stevenson reported in Cordoba and AP writer Amy Guthrie reported from Mexico City. AP writer Sonia Perez D. in Cordoba contributed to this report.