Health fears as El Comandante falters on tour to visit protege

Fidel Castro, the Cuban President, celebrates his 75th birthday today after a weekend visit to Venezuela which intensified concerns about his deteriorating health.

Although hailed by Hugo Chavez, the leftist Venezuelan leader that many consider to be his protégé, as "this 75-year-old youngster, the same Fidel as ever", El Commandante seemed to flag in the steamy heat.

When Mr Castro tottered on arrival at Caracas airport, aides rushed to grab him before he could fall. It was reminiscent of his public fainting spell seven weeks ago, which he later joked was a "rehearsal for my funeral".

President Castro's gait appeared stiff as he reviewed a military honour guard, and his croaky voice kept official speeches relatively brief, down to 45 minutes rather than the usual hours of rhetoric.

In the high humidity of Ciudad Bolivar, a colonial town on the Orinoco river where the 19th century liberator Simon Bolivar regrouped and linked up with British legionnaires, Mr Castro apologised for the failing to meet the crowd's expectations of legendary oratory. "I don't have a very clear voice today. I'm not thinking of delivering a long speech. It's very hot," he told those who gathered to see him receive the Order of Angostura, Venezuela's highest civil award.

It was difficult to believe this was the same strongman who shed his combat boots and donned trainers last year to lead millions of Cubans in protests against the US delay in returning the six-year-old castaway Elian Gonzalez to his Cuban father.

Since he gave up smoking cigars in 1985, President Castro's health has continued to be robust, despite rumours in Miami that he is suffering from prostate cancer and possibly Parkinson's disease and has had a stroke.

President Castro – who has outlasted 10 US presidents in the 42 years since he seized power in 1959 – and his brother, General Raul Castro, five years his junior, exhibit stamina beyond their years. Their late dinners and political discussions often continue until dawn. Both gobble PPG-5 pills – a kind of home-grown Viagra, derived from sugar cane – which significantly cut cholesterol and increase blood flow. PPG-5 is one of Cuba's best-selling pharmaceutical exports,

Despite temperatures in the mid-90s yesterday, the septuagenarian leader flew over the 2,900ft falls in Canaima National Park, with his Venezuelan host, before tackling bilateral meetings. The landscape of towering mesas and cascades is thought to have inspired Sir Arthur Conan Doyle's The Lost World.

One of the gifts Castro is taking back to Cuba today is the promise of 53,000 barrels of Venezuelan crude oil per day, enough to fuel the gas-guzzling 1950s jalopies which still ply Havana's streets long after the US embargo. In exchange, Cuban experts in health, athletics, and education will provide services in Venezuela.

Venezuela has become Cuba's closest ally in the region. President Chavez, 47, often sports khaki fatigues and a paratrooper's red beret, and there have been wide complaints against the curriculum he sets for state schools.

Critics call it "Cuban-style indoctrination, not education". Soldiers supervise social projects as they do in Havana. When President Castro dies, analysts believe Mr Chavez will inherit the leftist mantle in Latin America. He is fast friends with the Cuban President, talking at length about baseball and policy. He does not curry US favour, refusing to let anti-narcotics planes overfly Venezuela and last week evicting an American military mission from rent-free offices in Caracas.

Mr Chavez's fawning introduction of the Cuban leader left no doubt about his loyalties: "True fighters ... battle for an entire lifetime, overcoming hurricanes, storms and even bullets. Here is one of those men, Fidel Castro," he said to cheers.

President Castro has no plans to retire. His brother, Raul, has been handpicked as his successor as Maximum Leader, although analysts doubt he has the charisma carry it off for long.