Guinea pigs, human and otherwise

Clinical trials are big business and some Americans claim to earn a living from volunteering. Anyone considering taking part in a trial might want to refer to the internet site Guinea Pigs Get Paid, which lists details of forthcoming clinical trials and offers advice for participants.

Among its tips for volunteers are that one should not eat poppy seeds before a trial, because they show up in drug tests as opiates, and one should avoid drinking binges within a week of a study, because they can leave you with raised liver enzymes and thinned blood.

And the site recommends replenishing your red blood cell count between trials by taking iron supplements or eating iron rich foods washed down with orange juice.

The site also warns volunteers in the US to be wary of the “Jerry Springer crowd” — the “low life element” and “hot-headed rednecks” who may be attracted to taking part in clinical trials and whose volatile behaviour, as exhibited on the Jerry Springer Show, can can provoke confrontations that result in other volunteers being thrown off trials.

Advice for potential human research subjects is also available from a number of other sources. Among them is Guinea Pig Zero, an internet newsletter for volunteers set up by a veteran guinea pig.

It details historical accounts of early human experiments, provides tips on finding the least demanding and best paid trials, and also retells horror stories of clinical trials that have gone wrong.

But what is the link between guinea pigs and medical advances? The Andean rodents (Cavia porcellus) have been used in scientific experiments since the 17th century, when the Italian biologists Marcello Malpighi and Carlo Fracassati conducted vivisections of guinea pigs in their examination of anatomic structure.

Guinea pigs went on to play a major role in the establishment of germ theory in the late 19th century, through the work of Louis Pasteur, Emile Roux and Robert Koch.

The guinea pig was a popular laboratory animal until later in the 20th century. In the US, about 2.5 million were used annually for research in the 1960s, but the number decreased to about 375,000 by the mid 1990s.

By 2007, guinea pigs accounted for only about 2 per cent of laboratory animals. They have been replaced in research primarily by mice and rats, partly because research into their genetics has lagged behind that of other rodents. But they are still often used to diagnose tuberculosis, since they are easily infected with human tuberculosis bacteria.

And because they are one of the few animals that, like humans, cannot synthesise vitamin C, they are ideal for research into scurvy. Guinea pigs have also been identified as model organisms for the study of juvenile diabetes and, because of their frequency of pregnancy toxaemia, pre-eclampsia.