Self-evidently, you might think, there are several reasons why it is not a good idea to take pills made from pulverised rattlesnake meat and sold at roadside stalls in Mexico. But according the US Centres for Disease Control and Prevention (CDC) there is now an extra one: they can give you a potentially lethal dose of salmonella.

In its Morbidity and Mortality Weekly Report, the CDC includes notification of two cases occurring in late 2017 of people falling seriously ill with salmonella – both linked to the consumption of rattlesnake pills.

In the first case, in Texas, salmonella was found both in the patient and in the pills he had been taking as part of a “natural health” regime. The particular salmonella strain isolated by whole genome sequencing was found to be a close match for that found in another patient, a man from Kansas.

The Texan victim refused to be interviewed by CDC investigators, but the Kansas gent admitted to having travelled to the state of Chihuahua in Mexico, and purchasing five homemade rattlesnake pills – or, as they are also known, pastillas de víbora de cascabel. He had swallowed all of them.

The pills, made from dehydrated and smashed up snake flesh, are popular in Mexico and among some Hispanic communities in the US. They are marketed as cures for acne and cancer.

They have been associated with salmonella, sometimes lethally, on several occasions. In 1994, they were blamed for three deaths in Los Angeles County.

Their claimed benefit in treating severe illnesses, however, lends a particular danger to their use. In 1988, three Hispanic patients in Los Angeles developed salmonella after taking the pills – all had underlying chronic illnesses, including AIDS and heart disease. Another report, in 1990, details a previously healthy man who took rattlesnake pills and then developed salmonella, which turned out to be the “his initial manifestation of infection with the human immunodeficiency virus (HIV)”.

In its latest report, the CDC notes that rattlesnake pills resulted in “a majority of illnesses occurr[ing] in persons with cancer”.

The authors, led by epidemiologist Lyndsay Bottichio, note that the US Food and Drug Administration “does not review rattlesnake pills for safety or effectiveness”. They go on note that eating the pills is probably not a good idea for people with HIV, those receiving chemotherapy, pregnant women, children under five or anyone over 60.

Reporting on another case, in 2017, the American Council on Science and Health was rather less restrained in its advice.

“If you really have a yen to consume rattlesnake, avoid the pills and just go for the meat — but make sure it’s properly treated (i.e., cooked) to eliminate the risk of bacterial contamination,” author Ruth Kava suggested.

“Better yet, leave the snakes alone, after all, most other sources of meat don’t have dangerous venom and the means of delivering it.”