* Hundreds of farmers have died in Ebola outbreak
* Planting and harvesting disrupted - WFP
* U.S. troops to start training health workers
* Food prices expected to rise further (Adds detail of food distribution, quote from U.S. major general, Air Cote d'Ivoire flights resuming)
By Stephanie Nebehay and James Harding Giahyue
GENEVA/MONROVIA, Oct 17 (Reuters) - Food prices have risen by an average of 24 percent across the three countries worst hit by the Ebola outbreak, the World Food Program (WFP) said on Friday, as aid workers scrambled to distribute emergency rations to the hungry.
The food-producing regions of Guinea, Sierra Leone and Liberia in West Africa have been severely affected by the worst outbreak on record of the viral haemorrhagic fever that has killed 4,546 across the three countries.
Infection rates in the food-producing zones of Kenema and Kailahun in Sierra Leone, Lofa and Bong County in Liberia and Guéckédou in Guinea are among the highest in the region. Hundreds of farmers have died.
Decisions by the three governments to quarantine districts and restrict movements to contain the spread of the virus have also disrupted markets and led to food scarcity and panic buying, further pushing up prices, WFP and the Food and Agriculture Organization (FAO) have said.
"Planting and harvesting are being disrupted with implications for food supply further down the line. There is a high risk that prices will continue to increase during the coming harvest season," said WFP spokeswoman Elisabeth Byrs.
In the Liberian capital Monrovia, prices of cassava and imported rice, the main staple food, have jumped by 30 percent.
Aid workers in the crowded Monrovia neighborhood of Logan Town began distributing emergency rations of rice, bulgur wheat, peas and oil to around 1,000 residents on Friday.
"All our families are poor, let's be frank, so when WFP come to our rescue, along with Red Cross bringing food, they are so happy in the community," said Patricia Delaney, community chairperson of the neighborhood.
Byrs said WFP was carrying out a food security survey remotely using mobile phones to check the impact of the crisis on 2,400 families across the three worst affected nations.
In an effort to slow the spread of the virus, U.S. Major General Darryl Williams told reporters on Friday some 425 military personnel deployed to Liberia would start helping to train health workers there from next week.
"We plan to train 500 a week," he said, adding that the United States would also increase the number of helicopters sent to remote areas of the country to help with the Ebola response.
Despite repeated warnings from the World Health Organization that travel bans will only worsen the suffering of Ebola-hit countries, some U.S. lawmakers are calling for a ban on travel from West Africa.
However, Air Cote d'Ivoire's Chief Executive Rene Decurey said his airline would resume flights next week to the capitals of the three worst affected countries.
"It's not good to isolate these countries, because when you isolate them people will always find a way," he told Reuters.
In another piece of positive news, the WHO said the Ebola outbreak in Senegal was officially over, though it said the country remained vulnerable to further cases of the deadly disease being imported.
The first round of a survey of 800 people in Sierra Leone's eastern districts of Kailahun and Kenema showed people were worse off in terms of food security, despite being the main producing areas.
"The survey showed that certain families have cut down to one meal a day or that people are eating food that costs less, such as cassava instead of rice," Byrs told Reuters.
The WFP also began distributing food on Friday to 265,000 people in the Waterloo suburb near Sierra Leone's capital of Freetown, an area that has recorded high infection rates.
"The aim of the distribution is to stabilize quarantined families by giving them enough to eat so that they do not leave their homes to look for food," it said in a statement.
The aid, which included rice, pulses, vegetable oil and salt, should meet families' needs for one month, WFP added.
The WFP said it was procuring 74 vehicles including mortuary vehicles and pick-up trucks, funded by the World Bank, to help tackle the crisis. A first batch of 30 vehicles is expected to arrive by air in Sierra Leone on Saturday.
"We have enough evidence now to know that the best ambulance is not a closed ambulance, it's a pick-up. Why is it better to have a pick-up? The driver is protected. The person can be put in the back on a stretcher," said WHO's Isabelle Nuttall. (Additional reporting by Joe Bavier, Emma Farge and Tom Miles; Writing by Bate Felix; Editing by Gareth Jones)