A trip to the developing nations of the Third World, even with the President of the United States, holds its own perils for unwary Americans used to the pampered life.

That, at least, was the message the White House conveyed to the 150 reporters, photographers and television technicians who accompanied President Carter here yesterday on the first leg of his journey to Venezuela Brazil, Nigeria and Liberia.

Half an hour out of the safe confines of Andrews Air Force Baes, White House aides passed out a two page advisory on the two press planes that preceded Air Force One to Caracas. Itwas blandly titled "Health Advisory for Presidential Trip," but in reality it was a catalog of potential horrors awaiting the Waiting House press corps at every sto along the way. If it is to be believed and the reporters are not careful, they may require hospital planes for the return to the United States. The bulletin warned reporters about everything from dysentery and beach undertows to Liberian mamba snakes.

In each of the five cities that Carter will visit, the message was the same: Don't drink the water and "ices cubes are to bv avoided." Moreover, according to the advisory, each city has its own special problems.

In Caracas, for example, the journalists were told that "the drive to and from the airport is treacherous' steep drop-offs, sharp curves and tunnels." In Brasilla, where the president will visit today, the press was advised to avoid all animals because of the danger of rabies.

Carter will stop overnight in Rio de janeiro tomorrow and the American party is clearly looking forward to spending a few hours along that city's famed sun-drenched beaches. But the White House advisory painted a somewhat gloomy picture of Rio.

Tere is a uncovered between 11 a.m. and 2 p.m. Use sun screen liberally and limit time exposure. Theft is a great problem, especially on the beach and in the streets. Carry little of value with you.

The advisory also warned that Rio's air pollution causes respiratory problems such as asthma and sunusitis."

It will apparently be the same in Africa. As in Rio, there is a "severe undertow" along the beaches at Lagos Nigeria, the reporters were told. And in Monrovia, Liberia, according to the advisory, "Poisonous snakes, particularly the mamba, are prevalent. Avoid the shoreline and areas of thick vegetation."

The "common diseases" listed in the four countries the president will visit include amoebic dystentery, gastronenteritis, hepatitis, rabies, dermatosis, malaria, cholera, tentanus, typhoid, filariasis, yellow fever, meningitis and many others.

There is no way to know, of course, how many, if any, of these possible perils will actually confront the travelling Americans. But there was one hopeful sign yesterday afternoon. The "treacherous" drive from the airport into downtown Caracas turned out to be along a modern, four-lane divided highway.

The White House press corps stillawaits its first encounter with the mamba snake.